ABSTRACT
Witanachchi, Channa Devinda. Isovolumetric Weathering of Granite in Wake County, North Carolina. (Under the direction of Dr. Stanley W. Buol).
Saprolite, formed by chemical weathering of rocks near the earth’s surface, holds water,
serves as a parent material of soils, and is a medium for waste disposal. Saprolite
formation consumes CO2 and may stabilize atmospheric CO2 levels. This dissertation
examined the influence of joint orientation on isovolumetric weathering of saprolite
developed on the Rolesville granitic batholith at Knightdale, North Carolina. Rock
-3 density (ρs) (µ α 0.05) was 2.62±0.01 g cm . Mass altered per unit volume (mA/VT) of saprolite was taken as the difference between ρs and primary mineral mass remaining per
0 unit volume (m1 R/VT). Altered mass lost per unit volume (mAL/VT) was taken as the
difference between ρs and bulk density (ρb). Altered mass retained per unit volume
(mAR/VT) was taken as (mA/VT) – (mAL/VT).
Saprolite with steeply-dipping joints showed a uniformly sandy texture. The distribution
(mass percent) of sand-, silt-, and clay-sized particles (µ α 0.05) was 82.4±2.7, 10.3±1.8,
and 2.3±2.5, respectively, on a whole saprolite basis, and ρb (µ α 0.05) was 1.66±0.06
g cm-3. Saprolite with horizontally-oriented unloading joints was extensively altered and
occurred between horizontal slabs of unweathered rock. The saprolite was composed of
sandy layers alternating with clayey layers on the scale of approximately 1 to 2 cm. The
distribution of sand-, silt-, and clay-sized particles (µ α 0.05) in the saprolite was
50.1±10.4, 3.1±0.5, and 46.8±10.5, respectively, on a whole saprolite basis. Bulk density -3 (µ α 0.05) was 1.55±0.01 g cm . The mean content of sand-, silt-, and clay-sized particles
in the two saprolites differed statistically at α = 0.001, and mean bulk density differed at
α = 0.01.
The fine-earth fraction of saprolite with steeply-dipping joints was characterized (µ α 0.05)
by pH of 5.8±0.2, mass percent Fe2O3 of 0.21±0.09, cation exchange capacity (CEC) at
pH 7.0 of 3.95±0.88 cmol+ kg -1, and percent base saturation (% BS) of 36.66±9.93. The
fine-earth fraction of saprolite with horizontal joints was characterized (µ α 0.05) by pH of
+ –1 5.1±0.2, mass percent Fe2O3 of 2.68±0.28, CEC at pH 7.0 of 8.28±0.91 cmol kg , and
% BS of 19.73±9.22. The means of pH, mass percent Fe2O3, and CEC in the two
saprolites differed statistically at α = 0.001, and the means of % BS differed at α = 0.05.
The differences in mean values of individual extractable bases are not significant at
α = 0.05.
-3 Density of unweathered granite (µ 0.05) was 2.62±0.01 g cm . Calculated mean (µ α 0.05)
-3 values of mA/VT, mAL/VT, and mAR/VT (all in g cm ) in saprolite with steeply-dipping joints were 1.17±0.12, 0.96±0.06 and 0.21±0.05, respectively. Corresponding values in saprolite with horizontal joints were 1.85±0.15, 1.08±0.02 and 0.77±0.17, respectively.
Calculated mean (µ α 0.05) values of mAL/mA were 0.82±0.03 for the former saprolite and
0.58±0.06 for the latter, indicating greater leaching losses in the former. Differences in
the calculated means of mA/VT, mAR/VT, mAR/mA and mAL/mA in the two saprolites are
statistically significant at α = 0.001, and mAL/VT differed at α = 0.05. Saprolite with steeply dipping joints was composed predominantly of plagioclase and potassium feldspar. Saprolite with horizontal joints contained approximately equal proportions of potassium feldspar and kaolinite (or halloysite). Nordstrandite occurred in both types of saprolite.
0 Saprolite was classified based on the relative proportions of (m1 R/VT) 100/ρs, (mAR/VT)
100/ρs, and (mAL/VT) 100/ρs. Saprolite with steeply-dipping joints classified as
‘moderately altered, highly leached”, and saprolite with horizontal joints classified as
‘severely altered, moderately leached’.
Joint orientation appears to be a significant variable in saprolite formation. ISOVOLUMETRIC WEATHERING OF GRANITE
IN WAKE COUNTY, NORTH CAROLINA
by
Channa Devinda Witanachchi
A Dissertation Submitted to the Graduate Faculty of
North Carolina State University
In Partial Fulfillment of the
Requirements for the Degree of
Doctor of Philosophy
Department of Soil Science
Raleigh
2004
Approved by
______
(Chairman of Advisory Committee)
______
Biography
The author received the first eleven years of formal education in Sri Lanka. He came to the United States to attend the last year of high school and received a high school diploma from Vista High School, in Vista, North San Diego County, California.
He received a Bachelor of Arts degree in geology from Occidental College, Los
Angeles. Subsequently, he attended the geology program at Bryn Mawr College,
Pennsylvania, and received a Master of Arts degree in geology. At Bryn Mawr, the title of his thesis was 'Metamorphism and Deformation in the Wissahickon Schist,
Southeastern Pennsylvania', done under the supervision of Dr. Maria L. Crawford.
This was followed by one year of study in the graduate geology program at Emory
University, in Atlanta, and a year in the graduate geology program at Duke University, in Durham, North Carolina.
The author joined the Soil Science program at North Carolina State University in 1994 to further pursue his interests in agronomy and the environmental sciences, and served as a Research Assistant in the Pedology Laboratory for three years. Subsequently he worked at the North Carolina Geological Survey’s Piedmont Office. He is presently employed by the Division of Water Quality at the North Carolina Department of
Environmental and Natural Resources (NCDENR).
ii Acknowledgements
The author wishes to express appreciation for the guidance received from his advisor,
Dr. Stanley W. Buol. Much was learned about soils and global agriculture through our many conversations.
Many thanks are due to Dr. Aziz Amoozegar, Dr. Mike Vepraskas, and Dr. Edward
Stoddard for their support in many ways, including the service in the author’s advisory committee. Special thanks are due to Dr. Stoddard for extensive use of the X-ray equipment at the Department of Marine, Earth and Atmospheric Sciences, for his encouragement of cross-disciplinary studies, and for helping locate a study site for the research. Special thanks are also due to Dr. Amoozegar for help with bulk density determinations.
Thanks are due to Kim Hutchinson for answers to many laboratory questions, to
Peggy Longmire for assistance with centrifugation, and Roberta Harraway-Miller for assistance with determination of particle-size distribution and cation exchange capacity.
The study site at Wake Stone Corporation’s quarry in Knightdale, Wake County,
North Carolina was made available through the kind permission of Mr. John R.
Bratton. Thanks are extended to all staff at the quarry for their assistance, especially to geologist David Lee.
iii The author thanks the Soil Science Department of North Carolina State University for support through a research assistantship.
iv TABLE OF CONTENTS
List of Tables ……………………………………………………………….. XIV
List of Figures ……………………………………………………………….... XVI
Chapter 1 INTRODUCTION AND OBJECTIVES 1
Chapter 2 PREVIOUS WORK ……………………………... …………. 21
2.1 Weathering profiles ………………………………………….. 21
2.2 Weathering depth .…………………………………………… 28
2.3 Saprolite texture ……………………………………………… 31
2.4 Factors influencing weathering ……………………………… 35
2.5 Mechanisms of mineral alteration in saprolite ………………. 41
2.6 Major chemical reactions in saprolite ………………………. 44
2.7 Feldspar Weathering ………………………………………... 46
2.8 Previous work on quantification of weathering ……………... 51
Chapter 3 A MASS BALANCE APPROACH OF WEATHERING 57
3.1 Mass alteration, retention and loss ………………………….. 57
3.2 Bulk density ………………………………………………….. 64
3.3 Particle size distribution as a tool in the study of 65 isovolumetric weathering ……………………………………
3.4 Interpreting particle size distributions of isovolumetrically 69 weathered regolith in terms of alteration of primary mineral mass …………………………………………………………
Chapter 4 STUDY SITE 74
Chapter 5 MATERIALS AND METHODS 77
v 5.1 Sample selection and preparation …………………………… 77
5.2 Soil reaction ……………………………………………..….. 80
5.3 Analysis of free iron ….……….……………………………. 81
5.4 Extractable Cations …………………………………………. 81
5.5 Cation exchange capacity …………………………………… 81
5.6 Particle size distribution …………………………………….. 82
5.7 Bulk density …………………………………………………. 82
5.8 Mineralogical analyses of randomly-oriented specimens of 82 sand- and silt-sized fractions and oriented specimens of clay- sized fractions of saprolite using X-ray diffraction …………
5.9 Petrographic examination of grain mounts of the sand-sized 84 fraction of saprolite ………………………………………….
5.10 Statistical Analyses ………………………………………….. 87
Chapter 6 PHYSICAL CHARACTERISTICS OF REGOLITH 88
6.1 Mass distribution of sand-, silt-, and clay-sized particles …… 88
6.2 Particle size distribution of sand subfractions ……….………. 92
6.3 Bulk density …………..…………………………………….. 93
Chapter 7 MASS ALTERATION AND ITS PARTITIONING 96 BETWEEN SAPROLITE AND ITS ENVIRONMENT
7.1 Calculating mass altered per unit volume ….……………….. 96
7.2 Calculating altered mass lost per unit volume ……………… 101
7.3 Calculating altered mass retained per unit volume ………… 101
7.4 Variation of mA/VT, mAL/VT, mAR/VT, mAL/mA and mAR/mA 104 with weathering environment ………………………….……
vi Chapter 8 CHEMICAL CHARACTERISTICS OF REGOLITH 108
8.1 Soil reaction (pH) ……………………………………………. 110
8.2 Cation exchange capacity (CEC) ……………………………. 110
8.3 Extractable bases ……………………………………………. 111
8.4 Percent base saturation (% BS) …………………………….. 112
8.5 Mass percentage of citrate-bicarbonate-dithionite extractable 112 (free) iron ……………………………………….
Chapter 9 REGOLITH MINERALOGY 114
9.1 Petrographic examination of grain mounts of the sand – sized 114 fraction of saprolite ………………………………………….
9.2 X-ray diffraction ……………………………………….…... 117
9.3 Distribution of quartz and feldspar …………………………. 118
9.4 Distribution of non-interstratified 2:1 phyllosilicates ……… 124
9.5 Distribution of interstratified 2:1 phyllosilicates ……………. 126
9.6 Distribution of halloysite and kaolinite …………………….. 128
9.7 Distribution of hydroxides and oxyhydroxides of aluminum .. 132
9.8 Distribution of hydroxy apatite, monazite, allanite and zircon 137
9.9 Pseudomorphs and their contribution to the cation exchange 140 capacity of saprolite ………………………………………..
Chapter 10 A CLASSIFICATION FRAMEWORK FOR 143 ISOVOLUMETRICALLY WEATHERED REGOLITH
10.1 Classification framework proposed for isovolumetrically 146 weathered regolith ………………………………………….
10.2 Comparison of classification framework to Buol’s (1994) 151 saprolite classification ………………………………………
vii 10.3 Classification of saprolite investigated in this study using 153 the proposed classification framework ……………………
Chapter 11 VARIATION OF ISOVOLUMETRIC WEATHERING 155 WITH VARIATION IN JOINT ORIENTATION
11.1 Effect of joint orientation on the residence times of 156 weathering fluids ……………………………………………
11.2 The origin of red- and gray-colored saprolite ……..………. 158
11.3 A classification of isovolumetric weathering environments 162
Chapter 12 SUMMARY OF CONCLUSIONS 168
References …………………………………………………………..…... 177
Appendix I EQUATIONS DEVELOPED IN THE TEXT 198
Appendix II ATTRIBUTES OF PARTICLE-SIZE DISTRIBUTION 199
Appendix II-A Statistical attributes of the particle size distribution of 199 saprolite (mass percent) …………………………………….
Appendix II-B Statistical attributes of the ratios between masses of 200 selected particle-size fractions on a whole saprolite basis …
Appendix II-C Statistical attributes of subfractions of the sand-sized 201 fraction of saprolite (2.0 mm – 0.50 mm) …………………..
Appendix II-D Particle size distribution within the sand-sized fraction 202 expressed as mass percent of the fine-earth fraction of saprolite ……………………………………………………
Appendix II-E Statistical attributes of subfractions of the sand-sized 203 fraction (2.0 mm – 0.50 mm) as a fraction of the fine-earth (<2 mm) fraction of saprolite ……………..……
Appendix II-F Particle size distribution within the sand-sized fraction 204 expressed as mass percent of whole saprolite …………….
Appendix II-G Statistical attributes of sand subfractions (2.0 mm – 0.50 205 mm) on a whole-saprolite basis (mass percent) …………..
viii Appendix III X-RAY DIFFRACTION DATA FOR THE SAND-SIZED 206 FRACTION
Appendix III-A X-Ray diffractograms of Na-saturated randomly-oriented 206 specimens of the sand-sized fraction at 25oC ……………….
Appendix III-B XRD peaks (nm) indicative of muscovite and biotite in Na- 209 saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite. ……………………………
Appendix III-C XRD peaks (nm) indicative of 2:1 phyllosilicates (excluding 211 muscovite and biotite) in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite ……..
Appendix III-D XRD peaks (nm) indicative of halloysite in Na-saturated 213 randomly-oriented powder mounts of the sand-sized fraction of saprolite …………………………………………………..
Appendix III-E XRD peaks (nm) indicative of kaolinite in Na-saturated 215 randomly-oriented powder mounts of the sand-sized fraction of saprolite …………………………………………
Appendix III-F XRD peaks (nm) indicative of the plagioclase feldspar 217 low albite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite ……………………...
Appendix III-G XRD peaks (nm) indicative of K-feldspars orthoclase, 219 intermediate microcline and maximum microcline in Na-saturated, randomly-oriented powder mounts of the sand-sized fraction of saprolite …………………………….
Appendix III-H XRD peaks (nm) indicative of quartz in Na-saturated 223 randomly oriented powder mounts of the sand-sized fraction of saprolite …………………………………………
Appendix III-I XRD peaks (nm) indicative of gibbsite, bayerite and 226 nordstrandite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite ……………...
Appendix III-J XRD peaks (nm) indicative of pseudo boehmite and 232 boehmite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite …………..….
ix Appendix III-K XRD peaks (nm) indicative of diaspore in Na-saturated 234 randomly-oriented powder mounts of the sand-sized fraction of saprolite ………………………………………
Appendix III-L XRD peaks (nm) indicative of hydroxy apatite in 236 Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite …………………………..
Appendix III-M XRD peaks (nm) indicative of monazite in Na-saturated 238 randomly-oriented powder mounts of the sand-sized fraction of saprolite ………………………………………
Appendix III-N XRD peaks (nm) indicative of allanite in Na-saturated 240 randomly-oriented powder mounts of the sand-sized fraction of saprolite ………………………………………
Appendix III-O XRD peaks (nm) indicative of zircon in Na-saturated 242 randomly-oriented powder mounts of the sand-sized fraction of saprolite ………………………………………
Appendix IV X-RAY DIFFRACTION DATA FOR THE SILT-SIZED 244 FRACTION
Appendix IV-A X-ray diffractograms of Na-saturated randomly oriented 244 specimens of the silt-sized fraction of saprolite ………….
Appendix IV-B XRD peaks (nm) indicative of muscovite and biotite 247 detected in Na-saturated randomly oriented specimens of the silt-sized fraction of saprolite ………………………..
Appendix IV-C XRD peaks (nm) indicative of 2:1 phyllosilicates (excluding 249 muscovite and biotite) detected in Na- saturated randomly oriented specimens of the silt-sized fraction of saprolite ………………………………………..
Appendix IV-D XRD Peaks (nm) indicative of halloysite in Na-saturated 251 randomly-oriented specimens of the silt-sized fraction of saprolite …………………………………………………..
Appendix IV-E XRD peaks (nm) indicative of kaolinite in Na-saturated 253 randomly-oriented specimens of the silt-sized fraction of saprolite ……………………………………………………
x Appendix IV-F XRD peaks (nm) indicative of the plagioclase feldspar low 255 albite in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite ……………………………
Appendix IV-G XRD peaks (nm) indicative of the potassium feldspars 257 orthoclase, intermediate microcline and maximum microcline in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite …………………………
Appendix IV-H XRD peaks (nm) indicative of quartz in Na-saturated, 261 randomly-oriented specimens of the silt-sized fraction of saprolite …………………………………………………..
Appendix IV-I XRD peaks (nm) indicative of gibbsite, bayerite and 263 nordstrandite in Na-saturated, randomly-oriented specimens of the silt-sized fraction of saprolite ………………………..
Appendix IV-J XRD peaks (nm) indicative of pseudoboehmite and 269 boehmite in Na-saturated, randomly oriented specimens of the silt-sized fraction of saprolite ………………………….
Appendix IV-K XRD peaks (nm) indicative of diaspore in Na-saturated, 272 randomly oriented specimens of the silt-sized fraction of saprolite ……………………………………………………
Appendix IV-L XRD peaks (nm) indicative of hydroxy apatite in Na 274 saturated, randomly-oriented specimens of the silt-sized fraction of saprolite ………………………………………..
Appendix IV-M XRD peaks (nm) indicative of monazite in Na saturated, 276 randomly-oriented specimens of the silt-sized fraction of saprolite ……………………………………………………
Appendix IV-N XRD peaks (nm) indicative of allanite in Na saturated, 278 randomly-oriented specimens of the silt-sized fraction of saprolite ………………………………………………...
Appendix IV-O XRD peaks (nm) indicative of zircon in Na saturated, 280 randomly-oriented powder mounts of the silt-sized fraction of saprolite ……………………………………….
xi Appendix V X-RAY DIFFRACTION DATA FOR THE CLAY-SIZED 282 FRACTION
Appendix V-A X-Ray diffractograms of deferrated, K-saturated clays at 282 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays ………………………………………………………
Appendix V-B XRD peaks (nm) indicative of 2:1 phyllosilicates in oriented 296 specimens of the clay-sized fraction of saprolite ………….
Appendix V-C XRD peaks (nm) indicative of halloysite and kaolinite in 302 oriented specimens of the clay-sized fraction of saprolite …………………………………………………….
Appendix V-D XRD peaks (nm) indicative of gibbsite in oriented 311 specimens of the clay-sized fraction of saprolite ………..…
Appendix V-E XRD peaks (nm) indicative of nordstrandite in oriented 315 specimens of the clay-sized fraction of saprolite ………..…
Appendix V-F XRD peaks (nm) potentially indicative of more than one 318 aluminum hydroxide or aluminum oxyhydroxide in oriented specimens of the clay-sized fraction of saprolite …
Appendix V-G XRD peaks (nm) indicative of pseudoboehmite and 322 boehmite in oriented specimens of the clay-sized fraction of saprolite ………………………………………………...
Appendix V-H XRD peaks (nm) indicative of diaspore in oriented 325 specimens of the clay-sized fraction of saprolite ………….
Appendix V-I XRD peaks (nm) indicative of plagioclase feldspar low 329 albite in oriented specimens of the clay-sized fraction of saprolite …………………………………………………….
Appendix V-J XRD peaks (nm) indicative of potassium feldspars 332 orthoclase and microcline in oriented specimens of the clay-sized fraction of saprolite ……………………………..
Appendix V-K XRD peaks (in nm) indicative of quartz in oriented 336 specimens of the clay-sized fraction of saprolite ………….
xii Appendix V-L XRD peaks (nm) indicative of hydroxy apatite, monazite, 339 and allanite in oriented specimens of the clay-sized fraction of saprolite ………………………………………..
Appendix V-M XRD peaks (nm) indicative of zircon in oriented specimens 342 of the clay-sized fraction of saprolite …………………
Appendix VI XRD PEAKS ATTRIBUTABLE TO PRIMARY 346 REFLECTIONS FROM THE [001] PLANE OF HALLOYSITE AND KAOLINITE IN THE SAND-, SILT-, AND CLAY-SIZED FRACTIONS OF SAPROLITE
xiii LIST OF TABLES
Table 1 Calculated values of mass altered per unit volume (mA/VT), altered 71 mass lost per unit volume (mAL/VT) and altered mass retained per unit volume (mAR/VT) required for selected mass distributions of primary minerals (PM) and secondary minerals (SM) at selected values of bulk density in the range 2.65 - 1.59 g cm-3 .……………
Table 2 Modal compositions (volume percent) for Rolesville granitoids 76 from Wake Stone Corporation’s quarry, Wake County, North Carolina. ………………………………………………………..
Table 3 Particle size distribution of saprolite (mass percent) ……………… 89
Table 4 Ratios between masses of selected particle-size fractions on a 90 whole saprolite basis ……………………..……………………….
Table 5 Particle size distribution within the sand-sized fraction of saprolite 93 expressed as mass percent of the total sand-sized fraction of saprolite ……………………………………………………………
Table 6 Bulk density of saprolite …………………………………………. 94
Table 7 Pseudomorph distribution (in number percent) in the sand-sized 99 fraction of saprolite ……………………………………………….
Table 8 Mass altered per unit volume (mA/VT) of isovolumetrically 100 weathered regolith …………………………………………………
Table 9 Altered mass lost per unit volume (mAL/VT) and altered mass lost 102 per unit mass altered (mAL/ mA) in isovolumetrically weathered regolith …………………………………………..………………
Table 10 Altered mass retained per unit volume (mAR/VT) and altered mass 103 retained per unit mass altered (mAR/ mA) in isovolumetrically weathered regolith …………………………………………………
Table 11 Comparison of population means for the parameters mA/VT, 105 mAL/VT, mAR/VT, mAL/ mA and mAR/ mA within weathering subenvironments and between weathering environment ………….
Table 12 Chemical characteristics of the untreated fine-earth fraction …….. 108
xiv Table 13 Statistical attributes of chemical characteristics of the untreated 109 fine-earth fraction …………………………………………………..
Table 14 Minerals and particles identified using petrographic microscope 115 and their number percent in the (whole) sand fraction of saprolite ..
Table 15 Distribution of quartz in saprolite ………………………………… 119
Table 16 Distribution of feldspar in saprolite ……………………………….. 121
Table 17 Distribution of non-interstratified 2:1 phyllosilicates in saprolite as 125 determined by XRD and petrography ……………………………...
Table 18 Distribution of interstratified 2:1 phyllosilicates in saprolite as 127 determined by XRD ………………………………………………..
Table 19 Distribution of halloysite and kaolinite in saprolite ……………….. 129
Table 20 Solubility of quartz in distilled water at room temperature, 132 expressed in µg/ml ………………………………………………..
Table 21 Distribution of hydroxides and oxyhydroxides of aluminum in 133 saprolite based on XRD …………………………………………….
Table 22 Distribution of hydroxy apatite and monazite in saprolite ………… 139
Table 23 Cation Exchange Capacity (CEC), particle-size distribution, and 141 abundance of pseudomorphs in saprolite ………………………….
Table 24 Saprolite classification fields ……………………………………… 149
Table 25 A Classification of weathering environments based on the 163 interaction of joint orientation of rocks with meteorology ………...
xv LIST OF FIGURES
Figure 1 Weathering profile developed on granite at Knightdale, North 17 Carolina …………………………………………………………….
Figure 2 Granite with steeply-dipping joints …………………………. 17
Figure 3 Excavation of saprolite developed from granite with steeply- 18 dipping joints ………………………………………………………
Figure 4 Massive granite …………………………………………………… 18
Figure 5 Weathering pattern associated with horizontally oriented unloading 19 joints ……………………………………………………………….
Figure 6 Schematic depiction of the alteration of primary mineral mass and 58 its potential partitioning between the sample and its environment during isovolumetric weathering …………………………………..
Figure 7 Definition of symbols used in the following text …………………. 59
Figure 8 Ranges in the calculated values of mass altered per unit volume of 72 isovolumetrically weathered regolith (mA/VT) required to obtain specified distributions of primary minerals in the bulk density range 2.65 - 1.59 g cm- 3 ……………………………………………
Figure 9 Location of study site .…………………………………………….. 75
Figure 10 Saprolite developed from granite with steeply-dipping joints …….. 78
Figure 11 Saprolite developed from granite with unloading joints ………….. 79
Figure 12 Classification framework for isovolumetrically weathered regolith 147
Figure 13 Classification position of the A and B saprolite (*) and the G and R 154 saprolite (+) within the classification framework for isovolumetrically weathered regolith ………………………………
xvi CHAPTER I
INTRODUCTION AND OBJECTIVES
The exposed crust of the earth consists mainly of plagioclase (35%), quartz (20%), K-
feldspar (11%), volcanic glass (12%), biotite (8%), and muscovite (5%), with feldspars
and glass representing approximately seventy five percent of the labile minerals (Nesbitt
and Young, 1984). In terms of rock types, the upper crust1, which ranges in thickness
from 20 – 50 km, is composed of 14% sedimentary rocks, 25% granite, 20% granodiorite,
5% tonalite, 6% gabbro, and 30% gneisses and mica schists (Wedepohl, 1995).
However, the proportion of crystalline rock outcrops differs markedly among continents,
ranging from 48 percent in North America to 13 percent in Europe (Blatt and Jones,
1975). Physical weathering processes mechanically break bedrock into fragments
(Bricker et al., 1994), and chemical weathering dissolves minerals by the action of water and its solutes (Wieland et al., 1988). Subsurface water containing or in association with atmospheric gases is the prime cause of chemical weathering (Ruxton and Berry, 1957;
Helgeson et al., 1969). The main chemical mechanisms of weathering are exchange, hydration, oxidation, hydrolysis, carbonation, and congruent dissolution (McBride, 1994, p. 207; Johnsson, 1992), and to a lesser extent reaction with sulfuric, nitric, and humic acids (Johnsson, 1992). Mineral dissolution typically proceeds by selective attack at specific sites on the mineral surface rather than by uniform dissolution of the entire surface (Burch et al., 1993). During chemical weathering, rocks and primary minerals become transformed to solutes and soils and eventually to sediments and sedimentary rocks, and thus chemical weathering is an important feature of the global
1 Defined by a P-wave velocity of less than 6.5 km/s (Wedepohl, 1995). hydrogeochemical cycle of elements (Giovanoli et al., 1988). Weathering, however, is
not only an earthly concern. Ferric-bearing assemblages on Mars indicate that oxidative
weathering of surface basalts has occurred during the evolution of the Red Planet (Burns,
1993).
Regionally metamorphosed rocks and intrusive igneous rocks with their characteristic
interlocking textures, structures, and mineral assemblages form in the earth’s interior at
elevated pressures and temperatures. The chemical alteration or weathering of an
igneous rock begins prior to uplift and erosion, and can be viewed as consisting of two
stages. The first is deuteric and/or hydrothermal alteration. The term ‘deuteric’ should
be restricted to alteration which does not involve large quantities of water introduced
from outside the rock and produces only small changes in the bulk composition of the
rock, whereas hydrothermal alteration involves large quantities of water from outside the
rock and can lead to drastic changes leading to complete replacement of feldspars by
other minerals (Brown and Parsons, 1994). Deuteric alteration occurs at temperatures
<450oC in most igneous rocks and can lead to (1) partial replacement by other phases
such as clay minerals, (2) replacement by feldspars of different compositions, and (3)
microtextural changes not involving changes in bulk composition (Brown and Parsons,
1994). The second alteration stage begins when erosion of overburden in response to
tectonic uplift brings plutonic rocks towards the earth’s surface where they encounter an
environment characterized by low temperature, low pressure, an abundance of meteoric
water, O2, CO2, organic activity and organic compounds. The minerals formed at high
temperatures and pressures alter to those which are stable in the near surface weathering
2 environment (Harris & Adams, 1966; Clayton et al., 1979; Twidale, 1982; Aleva, 1983;
Nahon, 1991; Evans, 1992, p. 107; Johnsson, 1992). However, weathering (as well as
diagenesis and regional metamorphism) occurs under a wide variety of conditions of
temperature and pressure, and can produce disequilibrium mineral assemblages as well
(Nagy et al., 1991).
Weathering reactions mainly involve the transformation of feldspars, phyllosilicates,
amphiboles, pyroxenes, and volcanic glass to the secondary mineral groups, kandites,
illites, smectites, vermiculites, and/or chlorites (Nesbitt and Young, 1989). The relative
reactivity of minerals decreases in the order: carbonates > mafic silicates > feldspars >
quartz (White and Blum, 1995). At low runoff, silicate weathering is more effective,
while at high runoff carbonates weather more rapidly (White and Brantley, 1995, p. 16).
Among silicates, the hydrolysis of Si-O-Al linkages is preferred over Si-O-Si linkages
+ under both H2O catalysis as well as H3O catalysis due to lower activation energies (Xiao
and Lasaga, 1994). Feldspar weathering is the most important weathering reaction
(Nesbitt et al., 1997). During the weathering of granitic rocks, Ca, Na, P, K, Sr, Ba, Rb,
Mg and Si are very mobile, Zr, Hf, Fe, Al, Th, Nb, Sc and the REE2 are immobile, and
the behavior of Mn, Cr, V, Fe and Ce is very dependent on redox conditions (Middleburg et al., 1988).
Weathering leads to changes in the original texture and structure of rocks. The unconsolidated materials above solid rock is defined as regolith (Glossary of Soil Science
2 Rare Earth Elements 3 Terms, 1997). Thus regolith is taken to include weathered rock, saprolite, as well as soil.
Saprolite is defined as “soft, earthy, clay-rich, thoroughly decomposed rock formed in
place by chemical weathering of igneous and metamorphic rocks” (Glossary of Geology,
1972), and the term saprolite is attributed to Becker (1895). Saprolites are also referred to as alterites (Nahon, 1991, p. 97). However, alterites are also defined as grains that have been so thoroughly altered by chemical weathering that identification of the original grain is impossible (Johnsson, 1990). In saprolites, original structures of the parent rock
may be preserved during pseudomorphosis of parent minerals by the resulting weathering
products (Nahon, 1991, p. 97). In a study of the Stone Mountain granite in Georgia,
Grant (1963) stated that the preservation of primary structures in saprolite indicates that
no large volume changes have occurred. Anand et al. (1985) interpreted the perfectly preserved granitic fabric within saprolite in southwestern Australia as an indicator of isovolumetric weathering. Pavich and Obermeier (1985) defined saprolite as the
isovolumetric weathering product of crystalline rocks. Since Becker’s definition of saprolite in 1895, the term saprolite has come to mean a residual regolith developed isovolumetrically on crystalline rock in which some or all of the primary minerals have
been extensively transformed in situ to weathering products (Velbel, 1990). In this study,
saprolite, isovolumetrically weathered rock, and isovolumetrically weathered regolith are
used interchangeably.
The preservation of structures in saprolite is due to a framework of variable rigidity
generated during the initial stages of weathering (Nahon, 1991, p. 97). The framework
may be provided either by the crystalliplasmas (septa of oxyhydroxides) themselves, or
4 when of granular nature, by parent relicts (skeletal grains) within the argilliplasma3
(Nahon, 1991, p. 97). Although isovolumetrically weathered regolith is usually recognized in the field by the apparent continuity of features such as relict rock foliations and joints, it is difficult to apply these criteria to regolith formed from rocks that originally lacked these features.
The properties of regolith that impact its many uses can be viewed as belonging to two categories – material properties of regolith, and profile or geometric properties of regolith. Specific attributes within these broad categories will impact specific uses.
Material properties can be taken to include physical and chemical attributes of regolith such as shear strength, compressive strength, volume expansion with water content, mineralogy, secondary porosity (f), saturated and unsaturated hydraulic conductivity, cation exchange capacity, and anion exchange capacity. Profile properties can be taken to include the arrangement in space, including the orientation and thickness, of different zones characterized by distinct physical and or chemical properties. A review of the literature indicates that such material and profile properties of regolith usually vary with attributes of the parent rock, weathering environment, position in the landscape as well as with the duration of weathering.
Some regolith properties that have implications for productivity in natural and managed ecosystems include, but are not limited to, total and exchangeable nutrient content,
3 Weathering products different from crystalliplasmas, formed under less aggressive weathering conditions than under which the crystalliplasmas formed (Nahon, 1991, p. 70)
5 regolith depth, pH, water-holding capacity, and drainage. It was known as early as 1967 that plagioclase is the principal source of calcium in most crystalline or silicate- dominated clastic terranes (Bowser and Jones, 2002). In severely weathered granitic saprolite in Malaysia, calcium constituted 0.01 percent of the total element content (on an
oxide basis) and exchangeable Ca values determined by the NH4OAc pH 7 method
ranged from 0.35 to 0.22 cmol+ kg-1 (Hamdan and Burnham, 1996). Hamdan and
Burnham suggested that ecosystem productivity was maintained only by closed nutrient
cycling in the absence of any aerial inputs such as loess and volcanic dust. As calcium is
phloem immobile, calcium needed for root growth must be taken up from the external
solution by the apical zones (Marschner, 1995 p. 519). Therefore, in less weathered
regoliths that still contain Ca-bearing phases such as plagioclase feldspars, amphiboles
and pyroxenes, it can be expected that the presence of these minerals would enhance the
colonization of the regolith by plant roots.
Weathering rocks acquire secondary porosity, and thus a capacity to store and transmit
fluids and gases, and depending on original composition and weathering conditions, a
capacity to exchange cations and/or anions as well. Bedrock permeability in granitic
rocks is primarily intragranular and is created by internal weathering networks of
interconnected plagioclase phenocrysts, whereas saprolite permeability is principally
intergranular resulting from the dissolution of silicate phases (White et al., 2001).
Together with fractured rock, regolith is often an important aquifer because of its porosity
(Heath, 1984; Jones, 1985; Le Grand, 1989; McFarlane, 1992; Welby, 1994). The
composition of water moving through regolith can be altered depending on the regolith’s
6 cation exchange capacity (CEC), anion exchange capacity (AEC), capacity to chemisorp
(specifically adsorp) cations and anions, as well as due to dissolution of regolith minerals.
These properties of regolith, together with regolith thickness, hydraulic conductivity and
the location of the groundwater table, are important considerations in protecting
groundwater from fertilizers and wastes applied on land.
Weathering influences the composition of natural water bodies as well. The composition
of natural waters can be viewed as the result of a titration of atmospheric CO2 with mineral rocks, and the composition of seawater can be viewed as the result of a titration of acid of volcanoes with the bases of rocks (Stumm and Morgan, 1981). Although natural water chemistry can be strongly modified by surficial or secondary processes, the overall mineral assemblage and mineral chemistry of the underlying material ultimately determine it (Bowser and Jones, 2002). Exchange sites and biomass represent interim storage that may or may not be in steady state over time (Bowser and Jones, 2002).
Silicate weathering represents an important sink for acidity on a local and global scale, whether it be of anthropogenic or natural origin (Oxburgh et al., 1994). Within the soil environment, neutralization of acidic inputs is accomplished by dissolution / exchange of
2- - - basic cations (Ca, Mg, Na, K) and / or retention of acidic anions (SO4 , NO3 , Cl )
(Schecher and Driscoll, 1987).
The determination of the extent of weathering and the nature and engineering properties of the products of weathering are among the most frequent and important geological problems that arise in connection with the investigation of the sites of practically every
7 dam, tunnel and power station (Moye, 1955). Saprolites are susceptible to collapse under
loading and saturation (De Sola, 1985), and this must be considered in the design of
foundations. Weathering often severely limits the number of possible quarry sites for
concrete materials, rock fill and rip rap (Moye, 1955). Estimates of the thickness of the
weathered mantle are necessary to determine the depth of excavation to bedrock and
expected settling of structures (Segovia, 1983). Segovia further stated that the
incomplete evaluation of the variations in the nature and thickness of the weathered
mantle can result in tilting and fracturing of structures, cost overruns in excavation
contracts, high maintenance costs of highways and other costs. In the Piedmont and Blue
Ridge geologic provinces of the eastern U.S. the lateral and vertical variability of rock
weathering presents significant problems in evaluating the probable cost of excavation
(White and Richardson, 1987). Regolith properties such as particle size distribution,
strength and the orientation of joints have been found to affect the stability of slopes
under conditions of rainfall and seismic shock, and have received considerable attention
of engineering geologists. Particle breakage was determined to be the principal means of
plastic volumetric compression of a decomposed granite soil4 by Lee and Coop (1995),
and the breakage of soil particles was found to greatly affect compaction properties and
permeability of decomposed granite soil (Makiuchi et al., 1988).
The products of weathering include sediments and solutes. Erosion transports weathered
material or sediment to a new site of residence or deposition (Johnsson, 1992). The dissolved yield of rivers is usually dispersed and homogenized oceanwide before
4 The term soil is used in the engineering sense of the word. 8 eventual removal (Edmond et al., 1995). For rivers that drain most rock types, the sum of
cations is balanced largely by bicarbonate (Bluth and Kump, 1994). These authors also
stated that the dissolved yield of a given drainage basin is determined by a balance
between physical and chemical weathering. Based on a study of sixty-eight watersheds
underlain by granitoid rock types distributed world-wide, White and Blum (1995) found
that due to evapotranspiration, stream solute concentrations were an inappropriate
surrogate for chemical weathering. These authors found that fluxes of K, Ca, and Mg
exhibit no climatic correlation, implying that other processes such as ion exchange,
nutrient cycling, and variation in lithology obscure any climatic signal, whereas SiO2 fluxes exhibit stronger correlations with temperature (r2 = 0.45) and precipitation
(r2 = 0.52). Grantham and Velbel (1988), based on a study of modern fluvial sands of the
southern Blue Ridge Mountains, North Carolina, determined that rock fragments are most sensitive to chemical degradation and that their abundance is the best indicator of cumulative weathering effects. McLennan (1993) observed a negative correlation between sedimentary yield and weathering history as measured by the chemical alteration
(CIA)5 of the suspended sediment for many of the world’s major rivers and other regions of denudation.
Knowledge of the dominant causes of denudation and uplift episodes is crucial to
understanding the tectonic and morphological evolution of continents (Foster and
Gleadow, 1993). The compositional data of clastic sedimentary rocks have been used to
chart orogenic progression, unroofing, and plate tectonic evolution (Johnsson, 1993).
5 CIA = [Al2O3 / (Al2O3 + CaO + Na2O + K2O)]*100 9 Sandstones commonly provide our only source of information concerning the composition, distribution, and evolution of ancient land masses (Johnsson, 1992).
The research of several workers has contributed to an understanding of the denudational
and climatic history of the Appalachian Piedmont. Based on borehole and seismic data,
Poag and Sevon (1989) determined that the source areas of the central Appalachians were
tectonically uplifted, intensely weathered, and rapidly eroded three times since the Late
Triassic. Popenoe (1985), based on a seismic-stratigraphic analysis, determined that the
Cenozoic strata off North Carolina’s continental shelf, slope and rise consist of eleven major depositional packages reflecting large eustatic sea-level changes. After 0.85 Ma
(middle to late Pleistocene) eight out of ten glaciations covered the northern
Appalachians and brought periglacial conditions to the southern Appalachians (Braun,
1989). Braun further stated that the Appalachians south of the glacial limit may be
evolving towards an equilibrium periglacial form “where the landscape is being shaped to
provide just the slope necessary to transport the debris provided by periglacial
conditions”. Based on thermobarometric calculations, Guaghan and Stoddard (2003)
suggested that over 10 km of crust may have been removed along the western side of the
Rolesville batholith in the Piedmont of North Carolina.
The physical and chemical properties of the saprolite itself, as well as the nature of the
contact between the regolith and bedrock may hold clues to reconstructing recent climatic
and weathering history at a given location. Most saprolite is better understood as having
a dynamic history throughout the Neogene, including the Quaternary, whether in
10 continuously warm or periodically cold climates (Thomas, 1995). Etching and stripping
(Twidale, 1990; Lidmar-Bergstrom, 1995) can be taken as an example of such a long
term geomorphic process. Etching is a two-stage mechanism of landform development:
first, an etch surface develops through the interaction of groundwaters and country rock,
and subsequently the regolith is stripped, exposing the weathering front (Twidale, 1990).
Etch forms are widely distributed and are especially well developed and preserved in the
relatively stable shield areas (Twidale, 1990). Lidmar-Bergstrom (1995) highlighted the importance of deep weathering and subsequent stripping during different times of exposure of the Precambrian basement of Sweden, and determined that the most important factor for the present relief differentiation is the time of exposure of the
basement surface during the Phanerozoic. Fairbridge and Finkl (1980), in a study of the
West Australian craton, determined that the erosional-sedimentation history has been one of repeated exhumation and reburial. They named this morphogeodynamic pattern of events as the cratonic regime. In most areas of the world, the present-day landscape contains form elements and materials that have been produced by past tectonic and /or climatic conditions which differ from the present ones (Ahnert, 1994). Thomas (1994, p.
83) noted that as saprolite formation may be influenced not only by the prevailing climate but also by climatic, tectonic and geomorphic evolution through perhaps 106 years,
weathering profiles simply do not develop in equilibrium with a single set of prevailing
environmental conditions, and that weathering profiles often have no definitive beginning or ending of evolution. Based on a cosmogenic 10Be analysis from a residual weathering
profile developed from metapelite in the Virginia Piedmont, Pavich (1985) suggested that
the profile developed during a period no less than 8 X 105 yr. Pavich (1989), based on a
11 minimum rate of saprolite production of about 4 m Ma-1 determined using base flow
dissolved solids draining the Appalachian Piedmont, suggested that the typical Piedmont
upland regolith has a residence time of between 1 and 5 Ma.
Many researchers have suggested that chemical weathering influences climate,
particularly through interactions with the global C cycle. On the continents, the two
major sinks for atmospheric carbon are the uptake of CO2 during chemical weathering
- and its transformation to dissolved HCO3 , and the uptake of CO2 during photosynthesis
and its transformation to organic matter (Gaillardet et al., 1999). The interaction between
weathering and CO2 is an important component of many climate change hypotheses. The addition and removal of CO2 to the earth’s atmosphere on a million-year timescale is dominated by geologic processes (Berner and Berner, 1997). They stated that CO2 is
- added by global degassing from a variety of sources. The HCO3 formed by silicate and
carbonate weathering is transported from soil and groundwaters to rivers and by rivers to
the sea (Berner, 1995, p. 566). The weathering of Ca- and Mg-silicates results in the net
removal of CO2 from the atmosphere, whereas the weathering of Na and K in silicates is
not important in the removal of CO2 because of the great solubility of Na- and K-
carbonate minerals (Berner, 1995, p. 567). Sodium and potassium are most likely
removed from ocean water by silicate formation accompanied by the return of CO2 to the
atmosphere (Moulton et al., 2000). The precipitation of CaCO3 in the ocean also has no net effect on atmospheric CO2 (Berner, 1995, p. 567). Over million-year timescales, the
process of chemical weathering of the continents may shift considerable amounts of CO2
from the atmosphere to seafloor carbonate sediments via river runoff (Bluth and Kump,
12 1994). Berner (1995, p. 566) distinguished between the short term (103 to 105 year)
carbon cycle where carbon storage and release involves transfers between the
atmosphere, ocean, and the biosphere, from the much longer multimillion year
geochemical carbon cycle where storage and release is only to and from rocks. Because
the total atmospheric CO2 content is relatively small, it is most sensitive to changes in the
flux rates between the reservoirs (Bluth and Kump, 1994).
Chamberlin (1899) proposed that the CO2 content of the earth’s atmosphere decreased
during times of enhanced continental weathering, resulting in glacial epochs. He
attributed the increase in the rate of chemical weathering to increased orogenic activity
and higher average elevations, which promoted the rapid weathering of silicates. Since
Chamberlin’s initial proposal, several variations of the uplift-climate hypotheses have
been proposed. In an overview of the connection between uplift and climate, Ruddiman
and Prell (1997) stated that two basic categories of uplift effects on climate are recognized: (1) direct physical impacts on climate by means of changes in the circulation
of the atmosphere and ocean; and (2) indirect biochemical effects on climate via changes
in atmospheric CO2 and global temperature caused by chemical weathering of silicate
rocks.
During the past 5 million years, uplift rates in Himalayan and Andean mountain ranges
and the Tibetan Plateau have increased significantly (Raymo et al., 1988). Raymo et al.
suggested that the cooling of global climate over the past few million years may be linked
to a decrease in atmospheric CO2 driven by enhanced continental weathering in these
13 tectonically active regions. Silicate hydrolysis weathering can buffer atmospheric CO2, thus moderating large increases and decreases in global temperature and precipitation through the greenhouse effect (White and Blum, 1995). According to Kump et al.
(2000), chemical weathering has played a substantial role in both maintaining climatic stability over the eons as well as driving climatic swings in response to tectonic and paleogeographic factors. However, based on GENESIS (version 1.02) climate model experiments, Gibbs et al. (1999) found a weaker-than-expected CO2-climate weathering
feedback. Their main findings were (1) silicate weathering rates are similar to outgassing
rates of volcanic and metamorphic CO2, (2) times of supercontinental stasis represent low
outgassing but also high aridity due to extreme continentality and thus low chemical
erosion fluxes, (3) times of continental dispersion represent high outgassing as well as
high runoff (and fluxes) due to increased proximity to moisture sources, and (4) changes
in hydrology due to differences in paleogeography accounted for significant variation in
the total silicate chemical erosions rates, whereas spatial variation in lithology accounted
for little variation in the total silicate chemical erosions rates.
The influence of vegetation on weathering, climate and CO2 levels have been
investigated by several researchers. Based on a study of anorthite6 and augite7
dissolution, Brady and Carroll (1994) found that silicate weathering in organic-rich
solutions is not directly affected by soil CO2 but is very sensitive to temperature. They
suggested that CO2 appeared to accelerate silicate weathering indirectly by fertilizing
6 A plagioclase feldspar with 90-100 % anorthite mole percent (Phillips and Griffen, 1981, p. 337). 7 A clinopyroxene (Phillips and Griffen, 1981, p. 183). 14 organic activity and the production of corrosive organic acids. Berner and Kothavala
(2001), based on their model GEOCARB III, found very high CO2 values during the
early Paleozoic, a large drop during the Devonian and Carboniferous, very high values
during the early Mesozoic, and a gradual decrease from about 170 Ma to low values
during the Cenozoic. They found through sensitivity analysis that the results of paleo-
CO2 are especially sensitive to the effects of CO2 fertilization and temperature on the
acceleration of plant-mediated chemical weathering, the quantitative effects of plants on
mineral dissolution rate for constant temperature and CO2, the relative roles of
angiosperms and gymnosperms in accelerating rock weathering, and the response of
paleo-temperature to the global climate model used. A major unknown in the advent of land plants on weathering rates is the thickness, particle-size distribution and
permeability of the pre-Silurian regolith (Drever, 1994). In today’s climate of western
Iceland, Moulton et al. (2000) found that the rate of weathering release of Ca and Mg to streams is about four times higher in vegetated areas than in bare areas, and that trees increased plagioclase weathering by a factor of two and pyroxene weathering by a factor of ten.
Over a period of about six months, the author made observations of saprolite and granite exposed in a quarry located within the Rolesville granitic batholith at Knightdale, about
16 km east of the city limit of Raleigh, in the eastern Piedmont of North Carolina.
(Subsequently, this site was selected as the site for this study). The thickness and texture of the apparently isovolumetrically weathered regolith appeared to vary with the structure
of the unweathered rocks. Depth of weathering, as indicated by brown-colored staining,
15 varied from less than a meter to over ten meters in sites located less than ten meters apart
(Figure 1). The thicker regolith was developed on granite with closely spaced steeply
dipping joints (Figure 2). The thicker regolith was of a relatively uniform sandy texture,
contained no core stones in the interval from the soil surface to about 5 m depth, and
could be excavated by earth-moving equipment without the use of explosives (Figure 3).
The thinner regolith was developed from massive granite that contained horizontally-
oriented joints (Figure 4). This type of regolith was composed of approximately
horizontally oriented slabs of rock with weathered material located between the slabs
(Figure 5). The weathered zones were composed of gray-colored layers alternating with red-colored layers on the scale of about 1-2 cm, with both types of layers oriented horizontally, almost perpendicular to the steeply dipping weakly defined foliation in the rock. In contrast to the sandy regolith developed from granite with steeply-dipping joints, the thinner regolith was of a clayey texture.
16
Figure 1. Weathering profile developed on granite at Knightdale, North Carolina. Regolith on the left side of figure shows weathering to a greater depth than regolith on the right. The deeply weathered regolith has developed from granite with steeply-dipping joints, and the less weathered regolith from massive granite with horizontally-oriented unloading joints.
Figure 2. Granite with steeply-dipping joints.
17
Figure 3. Excavation of saprolite developed from granite with steeply-dipping joints. The uniform weathering enables excavation without use of explosives.
Figure 4. Massive granite. Horizontally oriented unloading joints are visible near the soil surface.
18
Figure 5. Weathering pattern associated with horizontally oriented unloading joints. Lighter- colored less weathered (LW) material that cannot be broken with a hand shovel alternate with darker-colored more weathered (MW) material that is easily broken with a hand shovel.
Given the multiple roles of saprolite in nature as well its importance to many human
activities, the variation of saprolite properties, quantification of these variations as well as
identifying factors influencing saprolite genesis are of interest. The objective of this
study is to
(1) Develop a theoretical framework that would aid the conceptualization, quantification,
modeling, and comparison of isovolumetric weathering of igneous and metamorphic
rocks.
As this objective was pursued, joint orientation was perceived to be a primary factor in
the saprolite composition and the following objectives were pursued:
19 (2) Investigate the influence of the orientation of joints in the Rolesville granitic batholith
exposed in Knightdale, North Carolina, in controlling properties of the resulting
isovolumetrically weathered regolith when climate (rainfall and temperature),
organisms (fauna and flora), relief and time are similar.
(3) Determine the mass of primary minerals altered, altered mass retained, and altered
mass lost – all per unit volume – in saprolite developed from granite with steeply-
dipping joints and for saprolite developed from granite with horizontally-oriented
unloading joints in the Rolesville granitic batholith exposed in Knightdale, North
Carolina.
(4) Determine differences in particle-size distribution, bulk density, pH, cation exchange
capacity, extractable cations, CBD8-extractable Fe, and mineralogy for saprolite
developed from granite with steeply-dipping joints and for saprolite developed from
granite with horizontally-oriented unloading joints in the Rolesville granitic batholith
exposed in Knightdale, North Carolina.
Although not an objective of the study the author has proposed a conceptual classification of saprolite to promote further study.
8 Citrate-bicarbonate-dithionite 20 CHAPTER 2
PREVIOUS WORK
2.1 WEATHERING PROFILES
The vertical arrangement of weathered materials in the landscape is referred to as a
weathering profile. The weathering profile has also been described as the expression of
the sequence of changes necessary to bring the fresh bedrock into equilibrium with the
near-surface environment (Ruxton and Berry, 1957). These authors stated that at the
commencement of the development of a weathering profile, the rate and intensity of
weathering processes decrease with depth below the surface as the gases are gradually
exhausted. This implies that the weathering profile is gradational, with the degree of
weathering of the materials in the profile decreasing from the surface downwards. Buol
and Weed (1991) viewed the soil-saprolite profile as approaching a chromatographic
column if the material remains in place vertically and is undisturbed by horizontal
transport, as in this event, the severity of mineral weathering increase from the rock
through the saprolite to the solum with no apparent discontinuities. Reflecting the interests of the geotechnical community, Deere and Patton (1971) defined the weathering profile as the sequence of layers of materials with different physical properties which have developed in place by either mechanical or chemical weathering and which lie above the unweathered rock. The simplest expression of a weathering profile as exhibiting a progressive increase in the degree of alteration with distance from the weathering front may not always hold. For example, the most intense or aggressive
21 weathering may take place at some depth, controlled by the groundwater regime
(Thomas, 1994, p. 52).
Weathering profiles developed on granite show a great diversity. Many deep weathering
profiles developed on granite in Australia, Southeastern Asia, Africa and Brazil are
lateritic. Gilkes et al. (1973), in a study of lateritic deep weathering on porphyritic
microcline granite near Perth, Western Australia, detected five weathering zones. Zone 1 was the parent granite. Zones 2 and 3 were characterized by the alteration of primary minerals, whereas zones 4 and 5 were characterized by the alteration of secondary minerals. Gilkes et al. (1973) stated that these zones are not simply related to the conventional morphological pallid, mottled, and ferruginous zones. These authors suggested that this sequence may be regarded as normal in Western Australian laterites.
Butt (1983) described weathering profiles developed on granite in the Barr-Smith Range on the Yilgarn Block, Western Australia, that consist of kaolinitic saprolites (pallid zones) merging upwards into silcrete9, sandstone and grit. Neither aluminum oxides
derived from kaolinite nor iron oxides were present above the kaolinitic saprolite. The
quartz sandstone was interpreted to have formed by the removal of kaolinite by
congruent10 dissolution and the vertical settling and compaction of the resistant quartz
grains. In a study of granite weathering in Peninsular Malaysia, Eswaran and Bin
(1978a) detected several weathering zones. From the surface downwards these include the α zone (includes the A, B, C pedological profile), the β zone defined by a layer of gravel accumulation, the γm zone (mottled zone) with mottle > 5 %, the γp zone (pallid
9 Described by Butt (1983) as the most siliceous of the silica-indurated surficial deposits in Australia. 10 Synonymous with simple dissolution (Berner and Berner, 1987, p. 150) 22 zone) composed of a gray to white matrix with a sandy texture with rock structure
evident, the δ zone (weathered rock), and lastly R or cohesive rock. Boulange et al.
(1990) described a weathering profile developed on granite from Ivory Coast, which was
constituted, from the bottom to the top by a massive saprolitic bauxite, a fragmentary
saprolitic bauxite and a fragmentary alumino-ferruginous crust, in which textures and
structures were preserved in all three facies. Pavich (1986) divided the weathering
profile into soil, massive and structured saprolite, and weathered rock. He referred to the
transition zone between the soils and saprolite as the massive zone. Pavich et al. (1989)
divided the generalized weathering profiles for quartzofeldspathic rocks in Fairfax
County, Virginia, into weathered rock, saprolite, massive subsoil, and soil. These
classifications of weathering profiles did not consider the engineering properties of the
weathered materials.
A review of the geotechnical literature shows that most engineering divisions of
weathering profiles follow that of Moye (1955). He divided the weathering profiles
developed on granitic rocks in the Snowy Mountains in the South Eastern Highlands of
Australia into six zones. From bottom to top, in order, they are fresh rock, slightly
weathered granite, moderately weathered granite, highly weathered granite, completely weathered granite, and granitic soil, each zone being defined by engineering properties as well as by the presence or absence of granitic fabric, state of weathering of feldspars and biotite, and color. He noted that even in the completely or highly weathered zone, there frequently are large residual boulders of fresh or only slightly weathered granite surrounded by completely or highly weathered granite. Such boulders are referred to in
23 the literature as core stones (e.g., Twidale, Granite Landforms, 1982, p.89). Ruxton and
Berry (1957) described what they termed a typical section of weathered granite in Hong
Kong. It is composed, from bottom to top, of partially weathered rock (zone IV), core stones with residual debris (zone III), residual debris with core stones (zone II), residual debris (zone I), and soil (A and B horizons of pedologists). Corestones, however, have
not been reported from some weathering profiles. Newbery (1971) did not encounter spheroidal core boulders in weathered granite in excavations for the Batang Padang
hydro-electric scheme in West Malaysia, where the depth of weathering commonly
extended to 100 feet from the surface. He attributed this to the microfractures which facilitate the penetration of groundwater, the agent largely responsible for chemical
weathering. Dixon and Young (1981), described deep arenaceous weathering mantles
developed on granodiorite on the Bega batholith, Australia, that extended to depths of at
least 13 m beneath hill crests, which at the base of the mantles changed abruptly to solid
rock, with no zone of corestones.
Dearman (1974) distinguished between material properties and mass properties of
weathering rocks. Material properties are brought about by solution and decomposition of mineral grains, by opening up of grain boundaries and fracturing of mineral grains.
Baynes and Dearman (1978) attributed the changes in the engineering properties of granite induced by weathering to microfracturing, opening of grain boundaries and development of intragranular porosity. They stated that microfabrics are related to the degree to which feldspars have been weathered, to the proportions of clay produced during the decomposition reaction, and also to the extent to which particles have been
24 eluviated from the system. The Geoguide 2 (1987, p. 21), published by the Geotechnical
Control Office in Hong Kong, states that material descriptions may include color, grain size and other textural features, degree of decomposition, degree of microfracturing, strength, soil or rock name, and other characteristics such as slakeability. Martin (1986) summarized a comprehensive list of index tests that have been used in engineering studies of weathered rocks.
Properties of a weathering rock mass are defined by different stages of disintegration and solution (Dearman, 1974). The rock mass may be considered as a discontinuum consisting of rock material rendered discontinuous by planes of weakness or discontinuities (Anon, 1977). Mass descriptions may include (a) size, angularity, percentage and distribution of harder fragments, (b) spacing and nature of discontinuities, and (c) geological structure (Geoguide 2, 1987, p. 21). According to Bieniawski (1993), rock masses are classified in order to (i) identify the most significant parameters influencing the behavior of a rock mass; (ii) divide a particular rock mass formation into a number of rock mass classes; (iii) provide a basis for understanding the characteristics of each rock mass class; (iv) derive quantitative data for engineering design;
(v) recommend support guidelines for tunnels and mines; (vi) provide a common basis for communication between engineers and geologists; and (vii) relate the experience on rock conditions at one site to the conditions and experience encountered at others. In general, the importance of the properties of intact rock material will be overshadowed by the properties of the discontinuities in the rock masses (Bieniawski, 1993). Martin and
Hencher (1986) noted that at the larger scale or beyond that of individual minerals,
25 although it is often necessary to group mixtures of different material grades into mass
zones, which, for engineering purposes, can be considered to have distinct characteristics,
it is rare for uniform grades to extend through sufficiently large volumes of rock for their
properties to be considered representative for engineering designs. Goodman (1993,
p. 219) stated that “Because both rock-material changes and proportions of rock variously
affected are fuzzy concepts, there is no one right way to describe and classify weathering
profiles”.
Several workers have examined the zone between saprolite and weathered rock. Deere
and Patton (1971) referred to the transition from saprolite to weathered rock in
metamorphic and intrusive igneous rocks as the transition zone. Deere and Patton described this zone as characterized by a great range in physical properties of its
components, varying from soil-like materials to rock-like corestones, with corestones making up 10 to 95 percent by volume of the transition zone. Due to this variability, these authors stated that the transition zone is the seat of a great many engineering problems in residual soils. The soil between the corestones is a medium to coarse sand which can be relatively clean, or silty and micaceous (Deere and Patton, 1971). This zone is commonly very permeable and water losses are often noted by drillers when they reach this zone (Deere and Patton, 1971). Harned and Daniel (1989) also recognized a transition zone at the base of the regolith where unconsolidated material grades into bedrock, that consists of partially weathered bedrock and lesser amounts of saprolite, with particles ranging from silts and clays to large boulders of unweathered rock. Harned and Daniel stated that the thickness and texture of this zone depends on the texture and
26 composition of the parent rock, with the best defined transition zones being associated with highly foliated metamorphic rock and poorly defined transition zones associated with massive igneous rocks with saprolite present between masses of unweathered rock.
Thomas (1994, p. 54) stated that massive granite or migmatite11 may exhibit a sharp weathering front, appearing as a basal surface with transition to highly weathered characteristics over a distance of 1-3 m. Thomas (1994, p. 56) stated that rocks with minimal porosity tend to decompose thoroughly across a narrow band of saprolite formation. Sharp transitions are also often found where massive igneous rocks undergo sheeting due to pressure release (dilation) (Thomas, 1994, p. 56). Rainbird et al. (1990) described a 1 to 2 m thick transition zone located between “unaltered” granite and the overlying saprolite from Quebec, Canada.
Weathering profiles do not always exhibit decreased alteration with depth. For example, in the Inner Piedmont of the southeastern USA, Overstreet et al. (1968) reported that layers of unweathered rock may be completely surrounded by saprolite. Similar observations were made by Donn et al. (1989) in the Piedmont of South Carolina. In granitic saprolite developed from the Liberty Hill pluton in South Carolina, Gardner and
Nelson (1991) reported the occurrence of partially saprolitized joint blocks occurring immediately above similarly-sized wholly saprolitized blocks. Similar observations have been reported from Australia also. Twidale (1982) reported that in drill holes and in vertical shafts, it is frequently found that zones of fresh rock are underlain by rotted materials. Ollier (1965) reported that in weathered granite profiles over 400 feet thick
11 A heterogeneous rock type composed of interlayered bands or streaks of granitic mineralogy and a darker metamorphic component (Williams et al., 1982, p. 183-184) 27 that were encountered in the Khancoban Project (New South Wales, Australia), although weathering was usually most intense at and near the surface and decreased gradually with depth, some bores again showed alternating variably weathered and almost fresh granite.
2.2 WEATHERING DEPTH
In the Piedmont region of the southeastern USA, saprolite lies over the bedrock in most places (LeGrand, 1989). The soil-saprolite zone ranges in thickness locally according to the type of rock, topography, and hydrogeological history; it is as much as 100 feet thick in some places, but is generally less than 45 feet thick in most places (LeGrand, 1989).
In a study of the upland residual mantle of the Piedmont of Fairfax County, Virginia,
Pavich et al. (1989) reported that in general, saprolite is thickest beneath interfluves, and is thin or absent in valleys where erosion is rapid. Pavich (1990) observed in the same county that the thickness of saprolite is a function of rock structure and mineralogy; beneath uplands it is thickest on quartzofeldspathic metapelite, metagraywacke, and granite, thinner on diabase, and thinnest on serpentinite. Saprolite constituted the bulk of the weathering profile over quartzofeldspathic rocks (Pavich et al., 1989). Based on excavations in gneissic material the Piedmont and Blue Ridge provinces of Virginia, Stolt et al. (1992) observed that saprolite thickness decreased from summit to footslope, and attributed the greater thickness of saprolite at summits to the relative stability of this landscape position compared with associated backslopes and footslopes. These authors however did not investigate if saprolite thickness varied with the orientation of joints in the bedrock.
28 Reported thicknesses of saprolite in the southeastern U.S. are quite variable. In the
Piedmont of North Carolina, 90 percent of the records for cased bedrock wells show
combined thicknesses of 97 feet or less for the regolith and transition zones (Daniel,
1987), the transition being the basal part of the regolith that grades into bedrock (Harned and Daniel, 1989). At most places in the Piedmont of Fairfax County, saprolite is thicker than weathered rock. (Pavich et al., 1980). Saprolite is approximately 15 m thick beneath
Piedmont uplands near Washington D.C. (Pavich and Obermeier, 1985). The weathering profile developed on the granitic Liberty Hill pluton in South Carolina is at least 20 to 25 m thick (Gardner and Nelson 1991). In the Inner Piedmont of eastern North America, the maximum reported depth of saprolite is 185 feet logged in a water well near Cherryville,
Gaston County, N.C. (Overstreet et al., 1968). In the southern Piedmont region of the
USA, it is not unusual to find that one end of a building site must be blasted out of sound rock while the other end requires drilled shaft or pile foundations 30 m deep (Sowers,
1985).
Deep saprolite profiles have been reported from northern latitudes. In the Precambrian
Trail Creek granite facies of the Sherman Granite, southern part of the Laramie Range, in
Wyoming-Colorado, the granite is deeply disintegrated into a coarse grained sandy sediment (grus), and local thicknesses reach as much as 200 feet (Eggler et al., 1969).
Gauthier (1980) cited an unpublished report by Gagne (1979) that the thickness of the grus mantle developed on massive, coarse grained pink granite in the Big Bald Mountain area in New Brunswick, Canada as detected by seismic refraction locally reaches 60 m.
O’Beirne-Ryan and Zentilli (2003) reported a 30 m thick, argillaceous saprolite horizon
29 beneath Triassic clastic sedimentary rocks developed from granitoids of the South
Mountain Batholith of southwestern Nova Scotia. Smith and McAlister (1987) reported
the occurrence of deeply weathered (depth unspecified) granite in the Northwest Mourne
Mountains in Northeast Ireland. Rainbird et al. (1990) reported a 7.5 m thick saprolite
zone from Quebec, Canada, developed on granite that fully preserved the texture of the
protolith.
Saprolite thicknesses have also been reported from many temperate, subtropical, and
tropical regions. In the Hercynian granites of northern Portugal, it is not uncommon to
find a saprolitic layer 10 m thick (Middleburg et al., 1988). Moye (1955) described
granite weathered to depths from 60 to 100 feet in the Snowy Mountains of the South
Eastern Highlands of Australia. Ollier (1965) reported weathered granite over 400 feet
thick from the Khancoban Project in New South Wales. Dixon and Young (1981)
described arenaceous weathering mantles developed on granodiorite in the Bega batholith
in southeastern Australia that extended to depths of at least 13 m beneath hill crests.
Smith (1985) reported weathering depths extending to 60 m in porphyritic granite in near
Worsley, Western Australia. In the granitic landscapes of the central Ivory Coast,
Verheye and Stoops (1975) reported that saprolite may attain a depth of more than 15 m.
The weathering mantle developed on granite near Qala en Nahl in Sudan is usually less
than 30 feet (Ruxton, 1959). Melfi et al. (1983) investigated six weathering profiles on
granite in Brazil, from three bioclimatic zones located between approximately 10o S to
30o S. Saprolite thicknesses ranged from 20 m under high rainfall in southeastern Brazil
to 2 m in arid parts in northeastern Brazil. In Hong Kong, granite is frequently weathered
30 to a depth of more than 60 m, and much of the granite is weathered to depths of more
than 30 m (Ruxton and Berry, 1957). The depth of weathering of granite encountered
during construction of the Batang Padang hydro-electric scheme in West Malaysia
commonly extended to 100 feet from the surface, and the maximum depth of weathering
recorded was 1000 feet (Newberry, 1971). In Japan, the depth of ‘masa’ – or clean sand developed from granitic rocks that “retains the crystalline structure of the mother rocks”– sometimes exceeds 20 m (Mori, 1985), and is mainly distributed in the western part of the Japanese archipelago. In the weathered granites of the Kaduna District, Nigeria, the weathered granite zone extends to 20 to 40 meters below the ground surface and is characterized by an undulating weathering front relative to the ground surface (Sueoka et
al., 1985).
2.3 SAPROLITE TEXTURE
A review of the literature of weathering revealed that the texture of saprolite developed
from granitic rocks is almost always sandy, or arenaceous. The only report of an
argillaceous saprolite the author encountered is that by O’Beirne-Ryan and Zentilli
(2003) who reported a 30 m thick, argillaceous horizon of weathered granitoid beneath
Triassic clastic sedimentary rocks developed from granitoids of the South Mountain
Batholith of southwestern Nova Scotia.
The term grus is commonly applied to granite sand or fine gravel, regardless of whether some of the constituent particles have suffered alteration (Twidale, 1982, p. 93). The evolution of granitic rocks in temperate regions is characterized by the formation of
31 sandy saprolites (Aoudjit et al., 1995), with only 2 to 6 % clay (Aoudjit et al., 1993).
They stated that the clay fraction of these saprolites can have a diversity of compositions, ranging from kaolinite (the most widespread), to gibbsite or smectite. The occurrence of sandy textured saprolites have also been related to drainage conditions in the weathering environment. Pavich et al. (1989) stated that in well-drained environments, quartzofeldspathic rocks weather to kaolinitic sandy saprolite. They stated that the clay content of the most highly weathered felsic saprolites is generally from 5 to 10 percent.
Sandy-textured or grussy saprolite has been reported from many parts of the world. In the Precambrian Trail Creek granite facies of the Sherman Granite in the southern part of the Laramie Range, Wyoming-Colorado, the granite is deeply disintegrated into grus, with local thicknesses reaching as much as 200 feet. (Eggler et al., 1969). The presence of gruss was also reported in the Precambrian Boulder Creek Granodiorite of Colorado
(Isherwood and Street, 1976), and in granitic rocks of the southern Sierra Nevada in
California (Wahrhaftig, 1965). Krank and Watters (1983) reported that the Sierra Nevada granodiorite has broken down to a “sand sized soil”. Several sandy saprolites are reported from Canada. Gauthier (1980) reported the occurrence of sandy saprolite (grus) developed on massive, coarse grained pink granite in the Big Bald Mountain area in New
Brunswick, Canada, which they interpreted as a relict of pre-Wisconsin weathering.
They reported that the grus consists mainly of granule and sand-sized angular quartz and feldspar crystals, and consisted of more than 75 % sand and less than 25 % clay. In the small grain size fractions, quartz concentration decreased as the plagioclase increased.
McKeague et al. (1983) reported saprolite developed from granite gneiss from Cape
32 Breton Island, Nova Scotia, Canada. Their analyses indicated that the clay content of the saprolite is less than 8 percent. The weathered granite or growan from Dartmoor in southwest England contains much undecomposed feldspar, and characteristically has a low clay content, ranging between 2 – 7 % (Eden and Green, 1971). The fine fraction
(< 2 mm) of the deeply weathered granite in the Northwest Mourne Mountains in
Northeast Ireland reported by Smith and McAlister (1987) contained no more than 6% clay, and normally less than 2 %.
Outside of North America and Europe, sandy saprolites have been reported from Hong
Kong, Australia, and Brazil. In zone II of the weathered granite in Hong Kong described by Ruxton and Berry (1957) – which often contains roughly equal amounts of core stones, gruss, and residual debris - clay-sized grains seldom exceeded 5 percent. Dixon and Young (1981) described deep arenaceous weathering mantles on granites and granodiorites of the Bega batholith, southeastern Australia. They determined that these arenaceous mantles seem to have formed under humid temperate climates similar to those now experienced in southeastern Australia. The mantles consist of a shallow soil layer on top of gruss. The sand-sized (> 63 µm) content of the grus is 54 – 86 percent. They noted that the original granitic composition can be recognized with the naked eye, and seems to have undergone little chemical alteration. The six weathering profiles developed on granite in Brazil investigated by Melfi et al. (1983) were predominantly coarse-grained, consisting of 70 – 80 % pebbles and coarse sand and less than 5 % clay- sized material.
33 Grussification of many granitic rocks has been attributed to the expansion of biotite
during weathering. In the Precambrian Trail Creek granite facies of the Sherman Granite,
southern part of the Laramie Range, in Wyoming-Colorado, grussification is thought to
have been caused by the high temperature oxidation (principally the opaques and biotite)
early in the history of this granite which prepared for later exploitation by surficial
processes (Eggler et al., 1969). Grussification in the Precambrian Boulder Creek
Granodiorite of Colorado was attributed to biotite expansion along basal cleavages and
formation of hydrobiotite and biotite-hydrobiotite interlayer combinations (Isherwood
and Street, 1976). The major process in the weathering of Sierra Nevada granodiorites is
the expansion of biotite in contact with ground water, which produced microfractures
which progressively broke down the original rock to a sand sized soil (Krank and
Watters, 1983). In the granitic rocks of the Idaho batholith, Clayton et al. (1979)
determined that initial hydrolysis and oxidation of biotites provided sufficient pathways
for water entry, providing for the necessary conditions for the formation of grus. The
expansion of biotite was cited by Dixon and Young (1981) as the single most important
factor leading to the disintegration of the Bega granodiorite in southeastern Australia. In
some tonalite and granodiorite clasts in some glacial and glaciofluvial deposits in
southwestern British Columbia, Bustin and Mathews (1979) determined that the
alteration and expansion of biotite was responsible for the development of microfractures in the clasts which facilitated further chemical weathering.
Gruss may also form in rocks where minerals are highly fissured or may contain many
fluid inclusion, and also in coarse granitoid rocks with abundant plagioclase and mica
34 (Thomas, 1994, p. 55). Thomas (1994, p. 55) also stated that weathering penetration may take place throughout the rock mass in such rocks, no marked basal surface of weathering appears, and are commonly weathered to great depths. Thomas further stated that clay formation has hardly begun in such gruss, but that hydration and expansion of feldspar crystals together with early weathering of biotite have disrupted the rock fabric. In the granitic rocks of the southern Sierra Nevada in California, Wahrhaftig (1965) noted that the weathering of biotite and, to a much lesser extent, of plagioclase, appeared to break down the rock to grus. He stated that the actual breakdown to grus involves the development of many closely spaced fractures, the most prominent of them being oriented parallel to the boundaries of core stones.
2.4 FACTORS INFLUENCING WEATHERING
The thickness and degree of weathering is a product of the rate and duration (Taylor et al., 1992), and the depth of regolith is the product of a balance between the rate of production by weathering processes and the rate at which products of weathering are removed by erosion (Bricker et al., 1994, p. 85). Factors influencing the weathering of granite include climate, rock composition, texture, and fractures in rock (Twidale, 1982, p. 71-88).
Joint-controlled subsurface weathering transforms an essentially homogeneous rock mass into two types of material, namely corestones of fresh rock and the grus matrix (Twidale,
1982, p.89). The role of joints in the weathering of granite has been recognized by several others as well, including Moye (1955), Grant (1963), Wahrhaftig (1965), Pavich
35 et al. (1989), Pavich (1990), Overstreet et al. (1968), Ollier (1965), LeGrand (1989),
Little (1969), Baynes et al. (1978), Krank and Watters (1983), Thomas (1994, p. 55), and
Frazier and Graham (2000). In weathered granite in the Snowy Mountains, southeastern
Australia, Moye (1955) observed that weathering first penetrated along joints, and then
attacked the blocks that they enclosed. In the Stone Mountain granite in Georgia, Grant
(1963) noted that the initial condition of weathering may be visualized as rectangular blocks of rock surrounded by water bearing fractures. Little (1969) noted that most rocks are much more permeable through their joint systems than in the body of the rock and
that dense igneous rocks are virtually impermeable in the body. He noted that near the
surface, the joints are more open and water flows readily along them carrying the
biochemical products of vegetable decay and other corrosive compounds in solution. He
also noted that these solutions started to attack the rock along the rock joints and
weathering spread from them into the body of the rock. In the granitic rocks of the
southern Sierra Nevada in California, weathering proceeds inwards from joint surfaces
toward the cores of joint blocks (Wahrhaftig, 1965). In weathered granite of the San
Jacinto Mountains, Southern California, Frazier and Graham (2000) observed that the
effects of chemical weathering – indicated by increased feldspar pitting and biotite
expansion - increased upward in the profile and laterally toward joint fractures. In granodiorite in the Sierra Nevada, Krank and Watters (1983) observed that joints tend to collect and retain debris and water so that consistent weathering can take place on the joint surface adjacent to the collected debris and water. They further stated that once the fresh surface of the rock has been weathered, the permeability will increase and weathering can take place progressively deeper within the rock mass. Pavich (1990)
36 stated that since water movement is dependent on rock structure, the rock weathering rate
may be more dependent on soil water balance and rock structure than it is on mineral
dissolution kinetics if the rock contains at least one mineral phase that reacts rapidly with dilute acidic solutions. In the crystalline rocks in the Inner Piedmont of the southeastern
USA, weathering is deepest in rocks rich in plagioclase feldspar and on strongly jointed or foliated rocks (Overstreet et al., 1968). Ollier (1965) reported that in the weathered granite encountered in the Khancoban Project (New South Wales, Australia), rocks with closely spaced joints are usually uniformly weathered, but widely spaced jointing often leads to spheroidal weathering and the formation of corestones. In the Piedmont region of the southeastern USA, a soil-saprolite zone only a few feet thick is likely to suggest poorly fractured rocks below (LeGrand, 1989). At a granite quarry in Hingston Down in the South-west of England, Baynes et al. (1978) observed that the deeply weathered areas in the quarry “correspond with the more closely jointed areas”.
Fractures in the bedrock in the Piedmont of the eastern United States commonly occur in three intersecting sets, one consisting of sheet joints roughly parallel to the land surface, which are hydraulically connected to the regolith through two intersecting sets of nearly vertical fractures (Heath, 1989). However, in the Stone Mountain granite in Georgia,
Grant (1963) noted that weathering begins with meteoric water percolating downward in three sets of vertical joints of tectonic origin and horizontally along sheet joints. Harned and Daniel (1989) stated that the greatest number of open fractures in the Piedmont bedrock generally occur at depths less than 400 feet. However, Harned and Daniel did not specify the type of fracture.
37 As crystalline rocks weather where they encounters weathering fluids, the movement of weathering fluids within the landscape is pertinent to this study. Heath (1984) viewed the ground-water system in the Piedmont and Blue Ridge provinces of North Carolina as a terrain in which the regolith functions as a reservoir which slowly feeds water downwards into the fractures in the bedrock, the fractures serving as an intricate interconnected network of pipelines that transmit water either to springs or streams or to wells. In the Piedmont region of the southeastern states (of the U.S.), Le Grand (1989) also recognized water occurring in two contrasting types of media: (a) clayey granular soil-saprolite and (b) underlying fractures and other linear opening in bedrock. The soil- saprolite zone is capable of storing water readily but transmitting it slowly; in contrast, the bedrock fracture system has a relatively low storage capacity but is capable of transmitting water readily where fractures occur and interconnect (Le Grand, 1989). He noted that discharge is through porous granular material (clayey soil-saprolite or floodplain deposits), but much of the intermediate flow between the recharge and
discharge areas is through bedrock openings. In Wake County, North Carolina, recharge to the saturated zone is estimated to be approximately 10 to 15 percent of the annual precipitation (Welby, 1994).
The transition zone at the base of the regolith is a zone of high permeability (Daniel and
Dahlen, 2002). Daniel and Dahlen attributed the high permeability to the result of incomplete weathering where chemical alteration of the bedrock has progressed to a stage of mineral expansion and extensive fracture development in the crystalline rock, but not progressed so far that formation of clays and other weathering by-products has been
38 sufficient to clog the fractures. They believed that this transition zone of high
permeability on top of the bedrock may create a zone of increased groundwater flow in
the ground-water system.
The saprolite matrix has a wide range of pore sizes due to differential weathering of
individual mineral grains and subsequent solution removal (Schoeneberger and
Amoozegar, 1990). The lower bulk density of saprolite contributes to higher porosity
and a greater capacity for holding water at saturation than expected for soil materials with
the same texture as saprolite (Amoozegar et al., 1993). Amoozegar et al. also found in
that study, based on a study of saprolites in the Piedmont and Mountain physiographic
provinces of North Carolina, that the majority of pores in saprolite are greater than 0.003
mm in diameter. In weathered granitic rock in Southern California, Johnson-Maynard et
al. (1994) found, based on effective pore size distributions calculated from water
retention data, that 25% of the total porosity was associated with pores >100 µm in
diameter.
Several researchers have investigated the hydraulic conductivity of saprolite, weathered
bedrock, and associated soils. Amoozegar et al. (1993) studied the hydraulic
conductivity of twelve different soils and saprolites in the Piedmont and Mountain
physiographic provinces of North Carolina. They found that for the majority of sites,
saprolite had a higher saturated hydraulic conductivity (Ksat) than the Bt and / or the transitional (BC) horizon above it. In the Piedmont region of North Carolina,
Schoneberger et al. (1995) studied the variation in Ksat in a soil and underlying saprolite
39 developed on a gneiss schist at three geomorphic positions (ridge top, shoulder, and ridge nose). At all three geomorphic positions, the laboratory determined Ksat was consistently highest in the clayey Bt horizon, diminished with depth until reaching a minimum value in the transitional, less clayey B/C horizon, and then increased with depth in the upper part of the massive, low clay content saprolite. Vepraskas et al. (1996) investigated hydraulic conductivity of soil - saprolite horizons in two sites in the Piedmont
-1 physiographic province of North Carolina. The lowest Ksat values (< 0.3 cm h ) occurred in or near the transitional horizons that were directly below the Bt horizon. They determined that in the transitional horizons, the inter / interparticle pores were plugged with clay and this caused the horizons to have low Ksat values. In saprolite developed from felsic gneisses and schists in Wake County in the North Carolina Piedmont,
Amoozegar et al. (1991) found that macropores (root channels 0.1 to 0.5 mm in diameter) comprised approximately 2% of the saprolite body, but accounted for 95% of the water flow through saprolite under saturated condition. They determined that at a soil water potential of -10 cm, 50% of the flow was through the saprolite matrix. Vepraskas et al.
(1991) investigated the hydraulic conductivity of saprolite developed from a mica-schist
-1 near Raleigh, North Carolina. They found Ksat values ranging from 0.01 to 1.71 cm h , with a geometric mean of 0.27 cm h-1. They also found that channels (primarily 0.1-0.5 mm in diameter), although comprised only 1.9% of the sample volume, accounted for
93% of the Ksat. In weathered granitic bedrock with a low clay content (< 6%) in
Southern California, Graham et al. (1997) found Ksat values ranging from 1.4 to 3.7 cm h-1.
40 2.5 MECHANISMS OF MINERAL ALTERATION IN SAPROLITE
Nahon (1991) recognized two main types of chemical reactions during weathering at the expense of parent minerals. The first of these is simple dissolution, which leaves no weathering product in place (Nahon, 1991, p. 90). In simple dissolution, also known as congruent dissolution, secondary products are formed under equilibrium conditions from ions released in the weathering solution and transported for a variably short distance, and the process is also known as neotransformation (Nahon, 1991, p. 43). Congruent dissolution occurs without pseudomorphism (Nahon, 1991, p. 53) and structures are rapidly destroyed by congruent weathering (Nahon, 1991, p. 63). Congruent dissolution is also known as stoichiometric dissolution (McBride, 1994, p. 209). At the scale of observation of the petrographic microscope, weathering is designated as congruent if no secondary mineral is observed within the original boundaries of the parent mineral
(Nahon, 1991, p. 52). In silicate minerals, congruent dissolution is rare and is confined only to relatively iron-free olivine, amphiboles, and pyroxenes (Berner and Berner, 1987, p. 155).
The second type of alteration is incongruent dissolution, which generates secondary products through relative or selective accumulation of material through loss of other constituents (Nahon, 1991, p. 90). Incongruent dissolution is also known as nonstoichiometric dissolution (McBride, 1994, p. 209). At the scale of observation of the petrographic microscope, weathering is designated as incongruent when the secondary product replaces the parent mineral within its original boundaries (Nahon, 1991, p. 52).
As the secondary products are formed in situ from the nondissolved parent crystalline
41 structure, this process is called transformation (Nahon, 1991, p. 43). The
transformational products are related to the parent mineral, and the alteration products are
pseudomorphic after the parent mineral (Nahon, 1991, p. 53). Structures are preserved in incongruent dissolution (Nahon, 1991, p. 63). Weathering products that replace the parent mineral within its original boundaries during incongruent dissolution are called alteroplasmas (Nahon, 1991, p. 91). Among alteroplasmas, one can distinguish crystalliplasmas and argilliplasmas (Nahon, 1991, p. 91). Crystalliplasmas consist of oxyhydroxides and they lead to a peripheral pseudomorphosis of parent minerals simultaneously with generation of high microporosity (Nahon, 1991, p. 91).
Argilliplasmas consist essentially of phyllitic minerals and they lead to a complete pseudomorphosis of the parent mineral with generation of porosity detectable only under
SEM high magnification (Nahon, 1991, 91). Crystalliplasmas are generated where mineral weathering is very active (Nahon, 1991, p. 53), whereas argilliplasmas are generated under less aggressive conditions of weathering (Nahon, 1991, p. 70).
Congruent dissolution of grains at higher levels and incongruent dissolution of grains at lower levels is a common feature in the saprolite of many lateritic profiles (Merino et al.,
1993). In such profiles, parent rock minerals are universally replaced by kaolinite and oxides of Fe, Al, and Mn (mainly hematite, goethite, gibbsite, and lithiophorite) (Merino et al., 1993). They described the following sequence of textural alteration. Plagioclase and pyroxene shows a similar sequence of textural alteration within the profile. Fresh grains are pseudomorphically replaced by oxide shells (gibbsite in the case of feldspar, and hematite in the case of pyroxene) higher up in the profile. Still higher up in the
42 profile, the cores of the grains are dissolved congruently, creating voids inside the
pseudomorphic shell. Higher up, near non-saprolite, the voids become filled with oxide cement. If the parent mineral grains can also be replaced by kaolinite, kaolinite itself
will, higher up in the profile, be replaced by oxides, exhibiting the same sequence of
partial replacement. For feldspars and pyroxenes, this sequence typically takes place
over only a few millimeters from fresh rock, whereas for kaolinite, the changes occur
over a distance of tens of meters. Although weathering profiles are characterized by the
occurrence of both congruent and incongruent reactions, the overall weathering profile
has been viewed as being incongruent by several researchers. Kronenberg and Nesbitt
(1981) viewed chemical weathering of rocks as incongruent because a weathering residue
or soil replaces the rock cover. Middleburg et al. (1988) viewed weathering systems
overall as being open, irreversible and incongruent because dissolved salts are carried
away by flowing groundwater leaving behind a solid phase that is markedly different
from the fresh rock.
In the saprolite of lateritic profiles, the oxide shells constitutes a strong framework that is
mechanically able to bear the whole alteration profile without collapse (Merino et al.,
1993). According to Pavich et al. (1989), the strength of saprolite developed on foliated
metasedimentary and granitic rock derives from the orientation of and the large
percentage of quartz and muscovite grains that resist chemical weathering. They stated
that this fabric acts as a stable framework in which the dissolution of less resistant
minerals occur because without a chemically and physically stable framework, access of
solutions to unweathered minerals would be greatly restricted.
43 2.6. MAJOR CHEMICAL REACTIONS IN SAPROLITE
The most important mineralogical and geochemical modifications of the parent rock
occur during the initial phase of weathering characterized by preservation of original
structures and volumes (Nahon, 1991, p. 97). In granite, the decomposition is produced
by an alteration of the feldspars and micas by water (Lumb, 1962). In weathered granite
in Hong Kong, Ruxton and Berry (1957) determined that biotite commences to
decompose first in the solid rock, followed by plagioclase. When part of the plagioclase
had decomposed and the orthoclase was beginning to be attacked, the rock broke down to
platy fragments of decomposed granite called grus. They found that plagioclase
completed its decomposition first, and when most of the orthoclase had rotted to kaolin,
the grus crumbled into a silty sand. Greasy yellow flakes of mica persisted in this
residual debris which may outlast the orthoclase. Apart from disaggregation, the quartz
appeared to remain unchanged.
Calcium, Mg, Na and Si have been found to be very mobile in weathering profiles. In
lateritic weathering of granite in Western Australia, Gilkes et al. (1973) found that Ca,
Na, and Mg - which are mainly present in plagioclase feldspars and ferromagnesian
minerals - are removed during the earliest stages of alteration. Pavich (1990) stated that
the major reaction in saprolite formed from aluminosilicate-rich parent rocks is the
dissolution of mafic minerals and plagioclase, which leaves a skeleton of muscovite and
quartz. In foliated granitic rock of the Virginia Piedmont, chemically, most of the mass
lost from the saprolite is CaO, Na2O, and SiO2 (Pavich, 1986, p. 565). Pavich (1986) found this to correlate with the petrographic observation of alteration and loss of
44 plagioclase feldspar. Pavich (1986) found that other phases such as biotite and pyrite,
although altered in the weathered rock zone, are less abundant phases and, therefore,
comprise less of the mass lost than does dissolved feldspar. Pavich estimated that the
total mass lost during alteration of saprolite formed on a foliated granitic rock in the
Virginia Piedmont to soil as being about 75% as indicated by the increase in ZrO2.
However, based on a study of quartzofeldspathic rocks (quartz- and mica-rich metasedimentary rocks – i.e. metapelite, metagraywacke, and foliated granite) in Fairfax
County in the Piedmont of Virginia, Pavich et al. (1989) determined that the plagioclase dissolution does not determine the position of the weathering front because the hydrolysis of the feldspar proceeds at a kinetically slower rate than does the oxidation of the iron-bearing minerals and the hydration of the micas.
Advanced stages of weathering from the deeply weathered African erosional surface in
Malawi was described by McFarlane and Bowden (1992). The surface is mantled by a lateritic residuum overlying saprolite. Although the saprolite retained the original rock textures and structures, it was found to be severely leached, dominated by kaolins, quartz and secondary Fe minerals. McFarlane and Bowden determined that the leaching of aluminum from the vadose saprolite - that results from the congruent dissolution of kaolinite - results in the collapse of the saprolite. McFarlane and Bowden also believed that the contingent collapse of the kaolinized saprolite would lower the interfluves, progressively narrowing the vadose zone, until the land surface approaches the planar form of the stable, regional water table, and thus would be a realistic process for the leveling of extensive planation surface.
45 2.7 FELDSPAR WEATHERING
As the exposed crust of the earth consists of abundant plagioclase (35%) and K-feldspar
(11%) (Nesbitt and Young, 1984), the study of feldspar alteration has received considerable attention. Feldspar weathering occurs via dissolution of all components into solution with the subsequent precipitation of secondary minerals from solution (Blum,
1994). Feldspars preferentially dissolve at highly localized sites in the crystal lattice, which are determined by the location of crystal defects, and the exposure of these defects is not easily related to total surface area (Holdren and Speyer, 1985). Holdren and
Speyer stated that reactions at these crystal defects dominate weathering processes during the early stages of dissolution.
Feldspar dissolution is more rapid in very acid solutions, is more or less constant in the pH 5 to 8 range, and increases again above pH 8 (McBride, 1994, p. 210). Albite and K- feldspar have similar dissolution kinetics at pH <6 (Blum, 1994). For plagioclase feldspar in acid solution (pH 3 – 7) at 25oC the reaction rate increases with anorthite content (Oxburgh et al., 1994). The dissolution rate increases gradually with increasing
12 Ca content until ~ An75 , with a large increase in the dissolution rate of plagioclase between the compositions An75 and An<90 (Blum, 1994). Compositionally zoned plagioclase crystals commonly show differential weathering. For example, Rainbird et al. (1990) observed in weathered granite and saprolite in Quebec, Canada, that the sodic rims of many plagioclase grains were unaltered whereas the calcic cores were altered.
Feldspar weathering is one to three orders of magnitude slower than predicted from
12 An: mole percent anorthite 46 laboratory studies (Blum, 1994). Various explanations offered include (Blum, 1994)
(1) isolation of a large proportion of the feldspar surface area in isolated micropores, (2)
adsorbtion of inhibitors such as Al and Fe, (3) the high saturation states of soil solutions,
and (4) short duration of experiments relative to geologic time scales.
Several different products of plagioclase feldspar weathering have been observed. The influence of microenvironment on feldspar weathering products has been documented by several workers. Eswaran and Bin (1978b) studied weathered plagioclase feldspar
developed on granite in Peninsular Malaysia with the aid of SEM. Eswaran and Bin
(1978b) found that close to the rock, the first product is allophonic material present as
globules adhering to the voids in the grains. In the weathered rock zone the product was
halloysite with some amorphous silica spherules. Kaolinite formation commenced in the
pallid zone and gibbsite in the mottled zone. Eswaran and Bin (1978b) did not encounter
the alteration by the same feldspar to give admixtures of gibbsite and halloysite or
gibbsite and kaolinite. However, in the same horizon, they found that one feldspar grain
may alter to kaolinite while another to gibbsite, indicating that the presence of a void
beside a feldspar grain may determine the course of alteration. In the same weathered
granite, Eswaran and Bin (1978c) found that feldspars (dominantly plagioclases) and
micas are present until the upper part of the mottled zone. On granitic gneiss in the
Piedmont Province of North Carolina, Calvert et al. (1980) found that the initial
weathering of feldspar at the rock-saprolite contact is very rapid and results in a variety
of minerals, each formed within a specific microenvironment. Through electron
microscopy and other techniques Calvert et al. confirmed the direct formation of
47 halloysite, amorphous aluminosilicates and gibbsite. These same techniques also
suggested the resilication of the latter two minerals into tubular halloysite. Somewhat
higher in the profile Calvert et al. found that the halloysite recrystallized into kaolinite via
a randomly interstratified transitional phase. Calvert et al. determined that kaolinite is the
predominant clay mineral in most soils of the region. In granitic saprolite in
southwestern Australia, Anand et al. (1985) found that feldspars have altered to
halloysite, kaolinite, and gibbsite with no evidence of noncrystalline material. Anand et
al. found that the secondary minerals are commonly present as intimate mixtures within
altered feldspar grains, but discrete zones of gibbsite or halloysite-kaolinite are also
present. Anand et al. also believed that variations in the chemical microenvironment
within micrometer-size zones in grains controlled the type and distribution of secondary
minerals. Esteoule-Choux et al. (1993) observed abundant newly formed quartz grains
associated with altered K-feldspars in granite from the Central Hoggar (Algeria).
In addition to Calvert et al. (1980), several other workers have detected gibbsite as an
initial weathering product of feldspar. In the weathering of biotite-plagioclase gneiss in
Dekalb County, Georgia, the first products of plagioclase weathering were gibbsite and
probably allophane (Grant, 1964). Gibbsite was found associated with partially weathered feldspar, whereas groundmass feldspar - when completely weathered - yielded mainly kaolinite. Green and Eden (1971) detected gibbsite in the < 53 µm fraction of weathered granite or growan from Dartmoor in southwest England using XRD, in amounts ranging up to 20%. The growan contained much undecomposed feldspar
(15 – 25 %), and characteristically had a low (2 - 7 %) clay content. Green and Eden did
48 not find gibbsite in soil developed from growan, and concluded that gibbsite is an initial product of weathering that appears to be lost as weathering proceeds. Also in the weathering Dartmoor granite, based on a study of water chemistry, Ternan and Williams
(1979) stated that “ the decomposition of silicate minerals is currently leading to the production of kaolinite where spring water is circulating more slowly at deeper levels and to gibbsite under very freely drained conditions nearer the ground surface”. In granitic saprolites in northeast Scotland, Hall et al. (1989) found gibbsite occasionally associated with feldspar during the initial stages of weathering. In a study of granite weathering in
Brazil, Melfi et al. (1983) found that feldspar altered to kaolinite (and sometimes to gibbsite) in sub-humid to humid climates, but altered only to kaolinite in humid- temperate climates. In granite saprolite below glacial deposits in the Bayersischen Wald,
Germany, Wilke and Schwertmann (1977) found small amounts of gibbsite (DTA) in feldspar and biotite grains selected from the sand fraction of the saprolite (at 3 m depth).
Wilke and Schwertmann interpreted the decrease in gibbsite concentration towards the
surface as indicating that halloysite and gibbsite are unstable in the surface soil under
present conditions. On the granite complex in Ivory Coast, Verheye and Stoops (1975) found that all plagioclase had transformed into kaolinite without any intermediate weathering stage.
Field observations by several researchers suggest that K-feldspar is more resistant to weathering than plagioclase feldspar. In weathered granite from Stone Mountain in
Georgia, USA, Grant (1963) reported that microcline persisted to more advanced stages of weathering than plagioclase. In weathered granite in Fairfax County, Virginia, Pavich
49 et al. (1989) observed that plagioclase and epidote are less abundant upward in the
saprolite, but potassium feldspar persists to within 4m of the surface. In the 30 m thick
argillaceous horizon beneath Triassic clastic sedimentary rocks developed from
granitoids of the South Mountain Batholith of southwestern Nova Scotia described by
O’Beirne-Ryan and Zentilli (2003), plagioclase is weathered to clay minerals, whereas
there is extensive alteration of K-feldspar to clay minerals only at higher levels within the profile. In profiles of weathered granite that ranged to about 5 m depth in the Central
Hoggar in Algeria, phenocrysts of pink K-feldspar appeared relatively fresh to the naked eye displaying a certain resistance to crushing while the plagioclase became white and powdery (Esteoule-Choux et al., 1993).
All alkali feldspars are highly heterogeneous materials whose chemical composition and microtextures can vary on a submicrometer scale (Lee and Parsons, 1995). Lee and
Parsons further stated that “by the time a typical igneous or metamorphic alkali feldspar crystal enters the weathering regime, it has a number of distinct microtextural components, each of which may have a different reactivity”. Robertson and Eggleton
(1991) examined potassium feldspars in weathered granite at the Trial Hill Tin Mine in east Queensland. Robertson and Eggleton noted that in the perthitic potassium feldspars,
13 only the potassium feldspar component (Ab3-5An0Or95-97) of the original perthite
remained, whereas the plagioclase component of the perthite had completely converted to
a clay.
13 Ab: mole percent albite; Or: mole percent orthoclase. 50 2.8 PREVIOUS WORK ON QUANTIFICATION OF WEATHERING
A review of the literature indicates that quantification of weathering has been approached in three different ways. These can be classified as (1) measurement of the chemical flux within a watershed at the catchment scale, (2) the use of various chemical indices as surrogates for chemical alteration, and (3) the use of minerals that are highly resistant to chemical weathering.
In studies of weathering at the catchment scale, the weathering rate is determined in terms of a mass balance equation such as solute in outflow = solutes from atmosphere + solutes from weathering
± solutes from change in biomass ± change in exchange pool
(Drever and Clow, 1995, p. 464). Due to the difficulty of determining the biomass and exchange terms in the above expression, these two terms are commonly ignored (Drever
& Clow, 1995, p. 468). An alternative approach is to look at the budget of an element that is not significantly affected by ion exchange or biomass uptake, such as sodium and silicon (Stauffer and Wittchen, 1991). Silica, however, is variably retained in secondary minerals and may be affected by adsorption-desorption reactions and plant uptake, and thus the silica flux is not a simple direct indicator of the weathering of primary minerals
(Drever and Clow, 1995, p. 468).
Abrasion pH is one the many chemical indices that have been proposed as a surrogate for chemical weathering. Based on a study of granite weathering in Georgia, USA, Grant
(1963) found that abrasion pH ranged from 5.0 in saprolite to 9.3 in fresh rock, and was
51 directly related to bulk density and the amount of clay minerals. According to Grant
(1969), abrasion pH ≈ f [ (Na + K + Ca + Mg)/(Clay mineral)]. Based on a study of
granite in southwest Nigeria, Malmo (1980) stated that abrasion pH of feldspars can be
used for the characterization of weathered granite for engineering purposes. Read et al.
(1996) developed a feldspar weathering index (IFW), and applied it to study a buried soil
sequence. The index is based upon the assignment of individual grains to weathering
classes defined in terms of progressive changes in surface morphology identifiable under
a polarizing microscope. The index is defined as
IFW = [(LX1) + (ML X 2) + (MH X 4) + (H X 8)] / n,
where L = low weathering class; ML = medium-low weathering class; MH = medium-
high weathering class; H = High weathering class; and n = number of grains.
Chittleborough (1991) proposed a weathering index based on resistant heavy minerals
(WR) in the 20 – 90 µm fraction, defined as
WR = [(CaO + MgO + Na2O) / (ZrO2)].
Additional indices that have been proposed include the Chemical Index of Weathering
(CIW) of Harnois (1988)
CIW = [Al2O3/(Al2O3 + CaO + Na2O)] X 100; the Chemical Index of Alteration of Nesbitt and Young (1982)
CIA = [Al2O3/(Al2O3 + CaO + Na2O + K2O)] X 100);
the Weathering Index of Parker (1970)
WI = [(2Na2O/0.35) + (MgO/0.09) + (2K2O/0.25) + (CaO/0.7)] X 100;
and the Ruxton Ratio of Ruxton (1968)
R = SiO2/ Al2O3
52 Although these indices may give a semiquantitative estimate of the mass altered during weathering, they do not quantify the actual mineral mass chemically altered in a fixed volume of regolith during weathering.
The third approach for quantifying weathering uses minerals that are highly resistant to chemical alteration. Such minerals are termed index minerals (Marshall, 1940).
Marshall (1940) recommended zircon, tourmaline, garnet, anastase or rutile for use as index minerals. Marshall (1940) used index minerals to quantify the development of soil profiles. He chose the C horizon as the parent material and stressed the importance of parent material uniformity, which, if uniform, would “show constancy in amount of the index mineral at various depths and from place to place” (Marshall, 1940). Marshall and
Haseman (1943) proposed a method for measuring gains, losses or other changes that may occur during soil formation using index minerals. According to Marshall and
Haseman, if the percentages of the immobile indicators in the parent rock and the weathering product are respectively Rp and Ra, then Wa = Ra/Rp, where Wa is the mass of the original rock that gave rise to 1 g of the present-day weathering product. Barshad
(1964) proposed a method for calculating profile development to determine the “intensity of soil development”. Barshad assumed that clay is formed from the nonclay fraction, and that in any one horizon, the amount of clay formed is proportional to the loss of the nonclay fraction. Barshad considered the nonclay fraction in the C horizon to be the parent material for clay formation, and Rp was measured in this parent material. Barshad applied his analysis of profile development to a column of soil of unit cross-sectional area. The analysis required the determination of thickness, bulk density, and the weight
53 concentration of an immobile element for each horizon within the column of soil.
Barshad calculated the mass of the parent materials using Marshall and Haseman’s
(1943) statement that Wa = Ra/Rp. Barshad recognized the errors introduced in
calculations of profile development due to the migration of clay between horizons.
Barshad stated that changes due to soil formation can be evaluated with the greatest
certainty in profiles in which the clay distribution with depth indicates that the assumed
parent materials or what appear to be the preserved parent materials, have gained no clay
through migration, and in which any clay found in parent materials was there when soil
formation began.
The drawback with the index mineral methods of Marshall and Haseman (1943) and
Barshad (1964) is the difficulty of accurately measuring the concentration of the index mineral, which usually is zircon. Two methods are employed for the estimation of zircon in weathering studies. Zircon grains can be counted in the nonmagnetic heavy mineral fraction (Haseman and Marshall, 1945). The other method is the analysis for elemental zirconium using X-ray fluorescence (Chapman and Horn, 1967; Chittleborough et al.,
1984). The problem with the former method is that error arising from small quantities of zircon often make these results unreliable, and the isolation of the counting fraction is tedious and each step compounds analytical error (Moran et al., 1988). The problem with the second approach is that it is not possible to identify the source of Zr as it has been detected in the light mineral fraction (Khangarot et al., 1970), in clays (Carroll, 1953), and in relatively unstable minerals (Smeck and Wilding, 1980). In addition, metamict zircons may be sensitive to weathering (Colin et al., 1993).
54 The index mineral methods have been further developed. Brimhall and Dietrich (1987), assuming an absence of lateral fluxes, used the index mineral method to develop an expression for one-dimensional strain (εi,w) such that
(εi,w) = (Bi,w – Bi,p)/Bi,p , where B represents the columnar height of an elementary representative volume of protore (p) and its weathered equivalent (w). Applying this method, they were able to show a soil of the Mendocino Coast of California experienced a soil column collapse of
60 percent by dissolution of silicate minerals in the albic horizon and 70 percent dilation in the overlying organic-rich layer by root growth. Chadwick et al.(1990) derived an expression for the enrichment of an element during pedogenesis due to residual enrichment (resulting from the density changes due to dissolution and removal of mobile elements with a corresponding increase in porosity), strain (volume changes that may be associated with the density changes), and mass transport (an “open-system” contribution that results from mass movement of the element across the sample volume).
Their equation is
Cj,w ρp 1 ___ = [ ___ ] [ ______] (1+ τj,w) Cj,p ρw (εi,w + 1)
where Cj,w and Cj,p refer to the concentration of an element j in the weathered residues and parent materials respectively, ρw and ρp refer to the dry bulk density of weathered residues and parent materials respectively, εi,w is the strain term of Brimhall and Dietrich
(1987), and τj,w is an open chemical system transport function. According to Chadwick et al., knowledge of the concentration and density terms and knowledge of the strain term
55 allows the calculation of the transport function, which allows useful inferences about the involvement of pedogenic material from internal versus external source regions.
56 CHAPTER 3
A MASS BALANCE APPROACH OF WEATHERING
3.1 MASS ALTERATION, RETENTION AND LOSS
Chemical weathering of igneous and metamorphic rocks can be viewed as the processes
of alteration of primary mineral mass formed at high temperatures and pressures into
secondary minerals stable at the lower temperatures and lower pressures found at the earth’s surface (Harris & Adams, 1966; Clayton et al., 1979; Twidale, 1982; Aleva, 1983;
Nahon, 1991; Evans, 1992, p. 107; Johnsson, 1992). The altered mass partitions between
the weathering system and its environment. Although the partitioning is distinct from the
alteration of primary mineral mass, it influences the progress of weathering as well as
some of the physical and chemical characteristics of the resulting regolith, and therefore
can be viewed as an important aspect of chemical weathering.
As volume is conserved during the initial stages of weathering (Nahon, 1991, p. 97;
Grant, 1963; Pavich and Obermeier, 1985; Velbel, 1990), the chemical weathering status
of a unit volume of isovolumetrically weathered regolith (VT) can be characterized by
mA/VT = (mAR + mAL )/ VT (1)
where mA, mAR and mAL are mass altered, altered mass retained, and altered mass lost,
respectively. Despite the potential use of these parameters to quantify isovolumetric
weathering, there have been, to the author’s knowledge, no previous attempts at
quantifying isovolumetric weathering in terms of these three specific parameters. A
depiction of isovolumetric weathering expressed in terms of these three parameters is
57 schematically shown in Figure 6. Definitions and symbols used in the text following
Figure 6 are shown in Figure 7.
UNWEATHERED ISOVOLUMETRICALLY WEATHERED ROCK ROCK
altered mass lost altered mass lost
per unit volume per unit volume
mass altered mAL/VT mAL/VT
per unit volume
mA/VT altered mass retained
Primary Minerals per unit volume
ρs mAR/VT bulk density
ρb
unaltered mass unaltered mass
per unit volume per unit volume
o o m1 R/VT m1 R/VT
Figure 6 . Schematic depiction of the alteration of primary mineral mass and its potential partitioning between the sample and its environment during isovolumetric weathering.
58
ρs density of original rock
ρb bulk density of regolith o ρb1 R bulk density of primary minerals remaining in regolith o ρb2 bulk density of secondary minerals in regolith
VT volume of regolith
o m1 R mass of primary minerals remaining
m2o mass of secondary minerals
mA altered mass
mAR altered mass retained
mAL altered mass lost
PM primary minerals
SM secondary minerals
wt % PM weight percent of primary minerals
wt % SM weight percent of secondary minerals
Figure 7. Definition of symbols used in the following text.
Rocks weather in systems that are open to mass. Mass introduced into a weathering system includes water, carbon dioxide, various forms of organic matter including organic exudates from plants, and inorganic matter such as ions and clay-sized particles from adjacent weathering volumes, some of which might even be of eolian origin. In order for the conceptualization of weathering schematically depicted in Figure 6 to be valid we assume that the introduced mass retained in weathering products is minor compared to the initial mass contained in a unit volume of rock. Furthermore, the addition of organic matter to the weathering system can be considered minimal in the case of saprolite or isovolumetrically weathered rock, as the roots of most plants are generally concentrated
59 in the soil horizons above saprolite. It should be noted that it is conceivable that ions and
clay minerals translocate between volumes of saprolite due to downward and or lateral
water movement. Therefore, the method proposed here for the quantification of
weathering can be considered to be most applicable for saprolites that have experienced
no net gain in illuvial mass and for saprolite with a low content of clay-sized minerals.
For such regolith, Equation (1) can be considered an expression of altered mass balance.
If we assumed that an isovolumetrically weathered volume of rock experienced no gain
in illuvial mass, then such a volume can be viewed as being composed of primary
minerals inherited from the original rock that is chemically unchanged but may be
o reduced in size due to chemical alteration (denoted as m1 R / VT), mAR, and mAL. An
expression of mass balance for such a volume (VT) of isovolumetrically weathered rock can be written as:
o ρs = (m1 R / VT) + (mAR / VT) + (mAL / VT) (2)
where ρs symbolizes density of the unweathered rock. Equation (2) can be considered the
fundamental equation of mass balance in isovolumetrically weathered regolith.
Substituting Equation (1) in Equation (2) leads to an alternate expression for mass altered per unit volume,
o mA/VT = ρs - m1 R / VT (3)
It should be noted that Equation (3) is valid for isovolumetrically weathered regoliths that
have experienced no net illuvial gain as well as for saprolites that have gained illuvial
mass devoid of primary minerals.
60 Using Equation (3) to calculate mA/VT for an isovolumetrically weathered regolith
o formed from a parent rock with a density ρs requires the determination of m1 R / VT. It is, however, not easy to determine the separate mass of primary minerals remaining
o (m1 R) [as well as altered mass retained (mAR)] within a fixed volume of regolith. It can
be assumed that most of the primary minerals remaining in an isovolumetrically
weathered regolith formed from a coarse grained rock such as a granite would be located
in rock fragments and in the sand-sized fractions, with the clay-sized fraction composed predominantly of secondary minerals. Some secondary minerals may occur as pseudomorphs within the sand-sized fraction as well (e.g., Southard and Southard, 1987).
It is difficult to generalize about the relative abundance of primary and secondary
minerals in the silt-sized fraction of saprolite. It is therefore preferable to use
mineralogical analysis of all three size fractions to estimate its primary and secondary
mineral content.
Equation (3) can also be obtained by applying to isovolumetric weathering concepts
developed by Marshall and Haseman (1943) and Barshad (1964). Consider a column of
-3 saprolite X cm thick of unit cross-sectional area with a bulk density ρb (g cm ) that
-3 formed by the isovolumetric weathering of rock with a density ρs (g cm ). The following
parameters are used in the analysis:
Ra = percentage of an immobile indicator in altered material
Rp = percentage of an immobile indicator in parent material
Wa = mass of rock that gave rise to 1 g of the present day weathering product
3 VS = volume of a saprolite column (cm ), X cm long with unit cross-sectional area
61 3 VR = volume of rock from which the saprolite column formed (cm )
mS = mass of saprolite in volume VS (g)
mR = mass of rock in volume VR (g)
(m % NC)saprolite = mass percent of ‘non clay’ in saprolite
mNC = mass of nonclay in saprolite (g)
mC = mass of clay formed during isovolumetric weathering (g)
mS = (ρb X)
Since Wa = Ra/Rp (Marshall and Haseman, 1943), mR = (ρb X)Wa
=(ρb X)( Ra/Rp)
VR = [(ρb X)( Ra/Rp) / ρs]
If weathering is isovolumetric, then
VR = VS.
Therefore,
VS = [(ρb X)( Ra/Rp) / ρs]
mS = ρb [(ρb X)( Ra/Rp) / ρs]
mNC = mS (m % NC)saprolite
= {ρb [(ρb X)( Ra/Rp) / ρs ]} (m % NC)saprolite
Since the mass loss of nonclay equals the mass of clay formed (Barshad, 1964),
mC = mR – mass of nonclay in saprolite
= (ρb X)(Ra/Rp) – {ρb [(ρb X)( Ra/Rp) / ρs ]} (m % NC)saprolite
62 = (ρb X) (Ra/Rp) [1 - ρb(m % NC)saprolite / ρs]
Loss of nonclay in 1 cm3 of rock
= mC / VR
= ρs [1 - ρb(m % NC)saprolite / ρs]
= ρs - ρb(m % NC)saprolite
This term is equivalent to the expression used in the present study as
o mA/VT = ρs - m1 R / VT (3)
Mass that eluviates from isovolumetrically weathering systems (mAL / VT) can take the
form of ions, secondary minerals, as well as fine-grained primary minerals. Ions released
during the weathering of aluminosilicate rocks include cations of alkali elements, alkaline
earth elements, Si4+, Al3+ and others. These leaching (or eluviating) cations will usually
- be accompanied by anions such as bicarbonate (HCO3 ) to maintain charge balance (see
Bluth and Kump, 1994). A useful expression for mAL/VT is derived below in terms of
bulk density (ρb) and initial rock density (ρs).
Bulk density of a weathered rock is equal to the mass of primary and secondary minerals
contained in some volume (VT), and can be expressed as
o ρb = (m1 R / VT) + (mAR / VT) (4)
Equation (4) is valid irrespective of the movement of solute or mineral mass into an
isovolumetrically weathering system. Substituting Equation (4) in Equation (2) leads to
the expression
(mAL / VT) = ρs - ρb (5), 63 which is valid for isovolumetrically weathered regolith that has experienced no net gain
in illuvial mass.
3.2 BULK DENSITY
Bulk density is relatively easily determined and is routinely reported in studies of
weathering. Based on a study of granite weathering in Georgia, USA, Grant (1963) stated that bulk density is a good weathering of index. According to Grant (1975, p. 18 -
19), “… bulk density of granitic rocks decrease as the amount of weathering increases, until the base of the B-horizon is reached. Above the base of the B-horizon the bulk
density and clay content increase and bulk density has no further significance as a
weathering index.” It is shown below that bulk density is not suitable for tracking the
progress of isovolumetric weathering.
Substituting Equation (1) in Equation (5) yields
ρb = ρs - [(mA/VT) - (mAR/VT)] (6)
Equations (6) shows that a given value of ρb for an isovolumetrically weathered regolith
formed from a rock with a given initial value of ρs is not associated with a unique value
of mA/VT nor mAR/VT; it is only associated with a unique value of the difference between
mA/VT and mAR/VT. Equation (6) also shows that for a given value of initial rock density,
bulk density is uniquely related to mA/VT only for a given value of mAR/VT, which limits
the use of bulk density as an indicator of mA/VT in studies of isovolumetric weathering.
64 3.3 PARTICLE SIZE DISTRIBUTION AS A TOOL IN THE STUDY OF
ISOVOLUMETRIC WEATHERING
Weathered rock is usually composed of rock fragments, individual primary minerals that
were contained in the unweathered rock, and newly synthesized (noncrystalline, paracrystalline and crystalline) secondary minerals. Particle-size distribution of regolith
when performed on a mass basis is the relative mass distribution of particles of certain
size classes contained per unit mass of regolith. Particle-size distribution is perhaps the
most commonly performed test on regolith. Particle-size data also frequently carries with
it an implicit connotation of the degree of alteration, with finer particle-sizes associated
with more advanced weathering. It is therefore useful to rigorously consider the
evolution of particle-size distribution during isovolumetric weathering and its
relationships to the weathering parameters mA/VT, mAR/VT, and mAL/VT.
The particle-size distributions of igneous and metamorphic rocks change during weathering. The grain sizes of igneous and metamorphic rocks vary greatly, ranging from the extremes of tens of cm to aphanitic14. The degree of crystallinity and the grain
size of any igneous rock depend mainly on its cooling history during the period of
solidification and partly on the chemical composition of the magma (Williams et al.,
1982, p. 54). Acid plutonic rocks – which include granite, granodiorite and tonalite – are
of medium15 to coarse16 grain, and have a subhedral17 granular texture (Williams et al.,
1982, p. 161). Crystal size of metamorphic rocks increase with metamorphic grade,
14 Most constituents are so small as not to be visible to the unaided eye (Williams et al., 1982, p. 53). 15 Average diameter of an individual grain is between 1 mm and 5 mm (Williams et al., 1982, p. 54). 16 Average diameter of an individual grain is between 5 mm and 3 cm (Williams et al., 1982, p. 54). 17 Grains are only partly bounded by crystal faces (Williams et al., 1982, p. 56). 65 supported by the common observation of the increase in grain size in the order slate,
phyllite, schist, and gneiss (Williams et al., 1982, p. 448). The intercrystalline textures in
plutonic rocks are less varied than in volcanic rocks because of the much smaller range of cooling rates (Brown and Parsons, 1994). Individual minerals in igneous and metamorphic may within themselves host other minerals of different grain sizes. In granites, granite pegmatites18 and granophyres19, quartz is intergrown with alkali feldspar
(Williams et al., 1982, p. 61). Plagioclase feldspar, which constitutes 35% of the exposed
crust of the earth (Nesbitt and Young, 1984), forms a series having not only a wide range
of chemical composition but also a diversity of structural states, and is also characterized
by chemical zonation and submicroscopic unmixing phenomena (Bowser and Jones,
2002). In addition, the dissolution rate of plagioclase increases markedly with increasing
Ca content, with a marked increase in the rate above An75 (Blum, 1994). In studies of
weathering, a pedologist may not consider that spatial variation in crystal size and
chemical zonation is a possible variable that is difficult to quantify within a given igneous
or metamorphic rock.
Most of the secondary minerals synthesized during weathering are of clay (<2µm) size
(Norrish and Pickering, 1983). Secondary minerals pseudomorphed after primary
minerals, for example kaolinite and gibbsite pseudomorphed after feldspar, can be of the
same coarse size as the precursor mineral. Some of these pseudomorphs could be
18 An extremely coarse-grained rock enriched in minerals with fugitive components (H2O, CO2, F, and others) formed during the final stages of consolidation of a melt (Williams et al., 1982, p. 55). 19 An unusually sodic member of the granite family with an unusually high FeO/(FeO+MgO) ratio (Williams et al., 1982, p. 171). 66 expected to break into silt- or clay-sized particles in the process of sample preparation and sieving.
In addition to the mass distribution of regolith particles based on size, the mass distribution of regolith minerals based on mode of genesis can also be considered. The mass percent of primary minerals and the mass percent of secondary minerals would be such a distribution. The size intervals of rock fragments, sand, silt and clay are arbitrarily and differently defined in the professions of soil science, geology and engineering geology. Primary and secondary minerals, however, because of their genetic relationship to weathering, are defined solely based on their mode of genesis and are therefore devoid of the arbitrariness prone to the definition of particle-size intervals. Because of the genetic relationship, they can also be expected to show better correlation with the regolith’s mode of weathering than the arbitrarily defined particle-size intervals.
This section evaluates the relationship in regolith of the mass percent of primary minerals, mass percent of secondary minerals and the conventionally measured mass percentages of sand, silt and clay to mass altered per unit volume (mA/VT), altered mass
retained per unit volume (mAR/VT), and regolith bulk density (ρb).
Consider a volume of isovolumetrically altered regolith (VT) with a bulk density of ρb that is composed of rock fragments, and particles of sand-, silt- and clay-sizes. The total mass contained in this volume is (VT.ρb). The mass percent of primary minerals in volume VT
can be expressed as
o mass % primary minerals = 100 (m1 R ) / (VT.ρb) (7)
67 Substituting Equation (3) in Equation (7) yields
mass % primary minerals = 100 [ρs - (mA/VT)] / ρb (8)
Equation (8) shows that the mass percent of primary minerals in isovolumetrically weathered regolith is uniquely related to mA/VT only when ρs and ρb are held constant.
Therefore, the particle size distribution of primary minerals in isovolumetrically
weathering regolith is of limited value as an indicator of mass altered per unit volume.
Secondary minerals formed by the weathering of igneous and metamorphic rock are
usually concentrated in the clay-sized fraction of regolith. Larger aggregates of
secondary minerals such as those formed by the pseudomorphism of sand-sized or larger
aluminosilicate grains usually break into silt- or clay-sized particles in the grinding or
disaggregation step of sample preparation (e.g., Anand et al., 1985). The relationships
between the mass percent of secondary minerals, ρs, ρb, mA/VT and mAL/VT in isovolumetrically weathered regolith are discussed below.
Consider a volume (VT) of isovolumetrically weathered regolith with a bulk density of ρb
with the mass of secondary minerals denoted by mAR. The mass percentage of secondary minerals in VT is expressed as mass % secondary minerals = 100 mAR / (VT.ρb) (9)
Substituting Equation (1) in (9) yields
mass % secondary minerals = 100 [(mA/VT) – (mAL/VT)] / ρb (10)
Substituting Equation (5) in Equation (10) yields
mass % secondary minerals = 100 [(mA/VT) – (ρs – ρb )] / ρb (11)
68 Equations (10) and (11) show that the mass percentage of secondary minerals is uniquely
associated with mA/VT only when mAL/VT is invariant. Since mAL/VT usually is a
variable during isovolumetric weathering, the mass percent of secondary minerals is also
of limited value as an indicator of mA/VT.
3.4 INTERPRETING PARTICLE SIZE DISTRIBUTIONS OF
ISOVOLUMETRICALLY WEATHERED REGOLITH IN TERMS OF
ALTERATION OF PRIMARY MINERAL MASS
As a rock weathers isovolumetrically, the mass of primary minerals contained within a unit volume of regolith decreases. The particle-size distribution of isovolumetrically weathered regolith can be related to mA/VT if several assumptions are made. These
assumptions are:
(1) Primary minerals do not eluviate during weathering. That is, mass is lost only by the
eluviation of ions and secondary minerals.
(2) Mass that illuviates to a volume of regolith in the form of secondary minerals or
ions is considered to be negligible.
Under these conditions, the values of mA/VT required to obtain a given mass distribution
of primary and secondary minerals at a given value of bulk density and initial rock
density can be calculated using the Equations (8) and (11).
Values of mA/VT required to obtain some specified mass distributions of primary and
secondary minerals for isovolumetrically weathered regolith at selected values of ρb in the
69 range of 2.65 - 1.59 g cm-3 are shown in Table 1. It is assumed that the regolith formed by the weathering of an igneous (or metamorphic) rock with a density of 2.65 g cm-3, a value comparable to granites composed predominantly of feldspars and quartz with minor biotite. Examination of Table 1 shows that:
(1) In the bulk density interval 2.65 to 1.59 g cm- 3, high values in mass percent of
primary minerals require relatively low values of mA/VT. The range in the
permissible values of mA/VT is, however, large. For example, a mass distribution of
80 percent primary minerals and 20 percent secondary minerals can be obtained
- 3 with values of mA/VT ranging from 0.53 to 1.38 g cm . This constitutes a range in
- 3 mA/VT of 0.85 g cm .
(2) In the bulk density interval 2.65 to 1.59 g cm- 3, high values in mass percent
of secondary minerals require relatively high values of mA/VT. The range of
permissible values of mA/VT, however, are small. For example, a mass distribution
of 20 percent primary minerals and 80 percent secondary minerals can be obtained
- 3 with values of mA/VT ranging from 2.12 to 2.33 g cm . This constitutes a range in
- 3 mA/VT of only 0.21 g cm , which is much narrower than the range of permissible
values for regoliths with similarly high values in mass percent of primary minerals.
70 Table 1. Calculated values of mass altered per unit volume (mA/VT), altered mass lost per unit volume (mAL/VT) and altered mass retained per unit volume (mAR/VT) required for selected mass distributions of primary minerals (PM) and secondary minerals (SM) at selected values of bulk density in the range 2.65 - 1.59 g cm-3.
Calculations are based on isovolumetric weathering of a crystalline rock with a density of -3 -3 2.65 g cm . Units of mA/VT, mAL/VT, and mAR/VT are in g cm .
Mass % PM 100 90 80 70 60 50 40 30 20 10 0 Mass % SM 0 10 20 30 40 50 60 70 80 90 100
BULK DENSITY 2.65
mA/VT 0.00 0.26 0.53 0.80 1.06 1.32 1.59 1.86 2.12 2.38 2.65 mAL/VT 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 mAR/VT 0.00 0.26 0.53 0.80 1.06 1.32 1.59 1.86 2.12 2.38 2.65
BULK DENSITY 2.12
mA/VT 0.53 0.74 0.95 1.17 1.38 1.59 1.80 2.01 2.23 2.44 2.65 mAL/VT 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 0.53 mAR/VT 0.00 0.21 0.42 0.64 0.85 1.06 1.27 1.48 1.70 1.91 2.12
BULK DENSITY 1.59
mA/VT 1.06 1.22 1.38 1.54 1.70 1.86 2.01 2.17 2.33 2.49 2.65 mAL/VT 1.06 1.06 1.06 1.06 1.06 1.06 1.06 1.06 1.06 1.06 1.06 mAR/VT 0.00 0.16 0.32 0.48 0.64 0.80 0.95 1.11 1.27 1.43 1.59
The variation in the permissible values of mA/VT for obtaining different mass
distributions of primary minerals for isovolumetrically weathered regolith in the bulk
density range 2.65 to 1.59 g cm-3 is shown in Figure 8. The large range in the permissible
values of mA/VT for obtaining high values of mass percent primary minerals described in
(1) above can be explained as follows. The coupling of progressively higher values of mA/VT with progressively higher values of mAL/VT permits the regolith to maintain a high 71 Range in permissible values of mA/VT for different mass distributions of primary minerals
100
90
80
70 Minimum Mass 60 permissible percent 50 primary Maximum permissible minerals 40 30
20
10
0 00.511.522.53
-3 mA/VT (g cm )
Figure 8. Ranges in the calculated values of mass altered per unit volume of isovolumetrically weathered regolith (mA/VT) required to obtain specified distributions of primary minerals in the bulk density range 2.65 - 1.59 g cm- 3. Initial rock density is taken as 2.65 g cm-3.
mass percent of primary minerals. The requirement of high values of mA/VT for
obtaining high values of mass percent of secondary minerals discussed in (2) above can
be explained as follows. If it is assumed that primary minerals do not eluviate from the
weathering system, then the only mechanism by which the mass percent of primary
minerals can be decreased (and thus the mass percent of secondary minerals increased) is
by their conversion to secondary minerals, that is, by mass alteration.
72 Examination of Table 1 also shows that the value of mA/VT required to maintain a
particular mass distribution of primary and secondary minerals increases with decreasing
values of bulk density. This is due to several factors. Progressively lower values of bulk density require progressively larger values of mAL/VT. Since it is assumed that only
altered mass eluviates, the eluvial mass required to lower the bulk density has to be
created by mass alteration, accounting for a component of the increase in mA/VT. The increased removal of altered mass shifts the mass distribution in favor of primary minerals. If the mass distribution of primary and secondary minerals is to be restored, additional altered mass has to be created and retained, which accounts for the remaining component of the increase in mA/VT.
73 CHAPTER 4
STUDY SITE
The study site (35o 48.5’ N, 78o 29.9’ W) was located at the Wake Stone Corporation's
quarry at Knightdale in the eastern Piedmont of North Carolina (Figure 9), about 16 km east of the Raleigh city limit. The study site is located within the Rolesville granitic batholith. The mineral modes (volume percent) for samples from this quarry are given in
Table 2, based on the data of Kosecki and Fodor (1997). Plagioclase is An22-14 and K-
feldspar is Or88-92. Biotites have 100 [MgO/(MgO+FeO)] values ranging from 39 to 46.
All mineral modes, compositions and textures described here for the unweathered rock at
the study site are also from Kosecki and Fodor (1997).
At the study site, Kosecki and Fodor (1997) identified foliated granodiorite, foliated
granite, nonfoliated granite, granite dikes, and quartz monzonite dikes. They categorized
these rocks into three groups - foliated biotite-rich granitoid, nonfoliated granite, and late-
stage granitic dikes. Examination of Table 2 shows that the foliated rocks have a higher
biotite content (>5 volume %) than the other rock types. The late-stage dikes are
generally leucogranitic, and compositions are granite and quartz monzonite. They range
in thickness from 2 to 10 cm, and penetrate both foliated and nonfoliated granitoids.
None of the samples used in this study are from the dikes. Although the samples used in
the study showed minor foliations in the field, it was difficult to determine whether the
samples belong to the foliated or nonfoliated categories identified by Kosecki and Fodor
(1997).
74
Figure 9. Location of study site. The study site () is located within the Rolesville granitic batholith.
The main minerals at the study site are plagioclase, quartz, K-feldspar, biotite, and Fe-Ti
oxides. Minor minerals include chlorite, white mica, and apatite. Kosecki and Fodor
(1997) determined that the chlorite formed from the alteration of biotite. Accessory
minerals are monazite, allanite, and zircon. Plagioclase is subhedral to anhedral, and
quartz and K-feldspar - chiefly microcline, occur as anhedral grains interstitial to
plagioclase. The K-feldspar commonly contains inclusions of plagioclase and quartz.
Some plagioclase is myrmekitic20.
20 A texture characterized by minute wormlike or fingerlike bodies of quartz enclosed in sodic plagioclase (Williams et al., 1982, p. 61) 75 Table 2. Modal compositions (volume percent) for Rolesville granitoids from Wake Stone Corporation’s quarry at Knightdale, Wake County, North Carolina.
Grano- Granite Granite Quartz Granite diorite foliated nonfoliated Monzonite dike foliated dike Quartz 24.9 24.2 29.9 35.6 31.3 34.5 12.1 41.0 36.2 K-feldspar 17.0 25.9 22.9 22.6 26.1 26.3 35.7 21.4 48.9 plagioclase 44.2 39.9 36.6 29.5 37.9 31.6 48.5 30.3 14.1 Biotite 8.5 7.6 6.9 1.6 0.6 0.8 2.0 0.1 <0.1 Muscovite 1.3 0.9 0.4 0.2 2.6 2.1 0.3 3.7 0.2 Chlorite 0.3 0.1 0.6 0.5 0.7 1.0 0.4 0.7 <0.1 Opaques 0.6 0.5 0.8 0.4 0.2 0.4 <0.1 0.1 0.1 Zircon <0.1 tr <0.10.0 tr tr tr tr tr Allanite 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0.0 0.0 Apatite 0.4 0.2 0.4 0.0 0.0 <0.1 0.2 0.0 0.1 Monazite tr 0.0 0.0 0.0 tr tr 0.0 0.0 0.0 alteration 2.6 0.7 1.0 9.6 0.5 3.1 0.7 2.6 0.1
Data are from Kosecki and Fodor (1997). Each column represents analysis from a single sample. tr = trace.
Grain sizes of major minerals in the foliated granitoid and nonfoliated granite are mainly
0.5 to 3 mm. Grain sizes occasionally reach ~ 7 mm in the latter group. Grain sizes of
the late stage dikes reach 8 - 10 mm, or are aplitic21 with 1-mm sized grains.
21 Almost all of the constituents are anhedral (Williams et al., 1982, p. 59). 76 CHAPTER 5
MATERIALS AND METHODS
5.1 SAMPLE SELECTION AND PREPARATION
Saprolite samples that appeared to have developed from granite with contrasting rock structure were collected from the quarry in which active mining operations were being carried out. The Quarry management preimposed the conditions that under no circumstances were the mining operations to be interfered with nor safety conditions violated. This required that samples were collected quickly only in approved areas and in a manner acceptable to the Quarry management.
Eight samples were collected from saprolite developed from granite with steeply-dipping joints. In this type of saprolite, very steeply-dipping relict joints were visible. Samples were collected at 1 m, 2 m, 3 m and 4 m depths below the soil surface from two profiles that were located approximately 2 m apart (Fig. 10). The letter A follows sample numbers from one profile, and the letter B follows sample numbers from the other profile. The samples (4 of A type and 4 of B type) were analyzed separately in the laboratory.
77
Figure 10. Saprolite developed from granite with steeply-dipping joints. View is at 3 m depth of A (left, finer-grained) and B (right, coarser-grained) types of saprolite samples used in the study. The weak compositional banding is oriented vertically.
Three samples (numbered 300, 301, and 304) were collected from saprolite developed from granite with horizontally- or nearly horizontally-oriented unloading joints. This type of saprolite was sampled from a location about 100 m away from where the A and B saprolite samples were collected. Steeply-dipping relict joints were not visible in this type of saprolite. As this type of saprolite was not easily accessible on the walls of the quarry, it was collected by exploding the regolith with dynamite. Safety rules at the
Quarry precluded direct sampling and observation from within the craters caused by the explosions. As the samples were recovered from blocks the size of a few cubic meters in volume that were thrown up by the explosions, it was not possible to precisely establish the depths of the samples in the field. Judging from the depths of the cavities that 78 resulted from the explosions, and the presence of similar material in the walls of the
cavities when viewed from a few feet away from the mouth of the craters, the depth of
the samples in the field was estimated to be anywhere from the soil surface down to about
4 m. This type of saprolite was composed of laminae of about 1-2 cm in thickness (Fig.
11). The laminae were alternately colored red and gray. Each of the three samples that
were collected was manually disaggregated in the laboratory into their gray-colored
components (G) and the red-colored components (R). This resulted in six samples -
300G, 300R, 301G, 301R, 304G, and 304R. Each of these six samples was analyzed
separately in the laboratory.
Figure 11. Saprolite developed from granite with unloading joints. The regolith is composed of alternating gray-colored (G layers) and red-colored layers (R layers) on the scale of about 1-2 cm. These layers are parallel to the horizontally oriented unloading joints (not shown in the figure).
79 Samples collected in the field weighed approximately 2 kg each. The samples were
carefully crushed by hand, air-dried for two weeks inside the laboratory, and split into
two fractions by passing through a riffle with 14 chutes, each chute 0.5 inches wide. A
subsample of approximately 1.0 kg of this was passed through a 2-mm sieve after
carefully crushing by hand. This sieved material was further air-dried for 7 days and
stored in cardboard containers. The mass of the > 2mm and < 2 mm fractions was
determined for each sample.
Unless otherwise specified, all quantitative analyses were performed on air-dry materials.
The water content was determined by gravimetric weight loss at 110oC of a 10.0 g air-
dried sample, and the air-dry values were adjusted to corresponding oven-dry weights.
The oven-dry weight was not determined for the > 2 mm fraction.
5.2 SOIL REACTION
The pH was determined using an Orion Research pH meter on suspensions prepared by mixing 1 g of air-dried saprolite with 5 g deionized water to make a 1:5 dilution. The 1:5 ratio was adopted instead of a 1:1 ratio as some of the samples with a very high clay content (samples 300G, 301G and 304G) formed very thick slurries, which attached to the electrodes of the pH meter.
80 5.3 ANALYSIS OF FREE IRON
Sodium citrate-bicarbonate-dithionite (CBD) extractions were performed on triplicate 3-
to 5-g samples of air-dried whole saprolite (< 2 mm) following the procedure of Jackson
et al. (1986). The extracts were analyzed for Fe by atomic absorption spectroscopy.
5.4 EXTRACTABLE CATIONS
Exactly 2.5 g of each saprolite sample was placed into extraction syringes packed with a
1 g pad of compressed Schleicher and Schuell No. 289 Ash-Free Analytical Filter Pulp.
Each sample was leached with 35 ml of 1.0M ammonium acetate (pH 7) using a
Mechanical Vacuum Extractor adjusted for an extraction time of 8 to 10 hours as
described by Holmgren et al. (1977). The preweighed extraction tubes were weighed
again to determine the quantity of NH4OAc retained by the sample and pulp pad. The
+ samples were then washed three or more times with ethanol until no NH4 was detectable
in the leachate using Nessler’s reagent. The extractant was diluted and analyzed for
Ca, Mg, K, and Na using a Perkin-Elmer 5000 Atomic absorption spectrophotometer.
The saprolite samples were saved and used to determine cation exchange capacity.
5.5 CATION EXCHANGE CAPACITY
Cation exchange capacity (CEC) at pH 7 was determined with a Kjeltec System 1003
distilling unit using 1 N NaOH alkali solution (USDA-NRCS 1996, method 5A1a).
Before digestion, 6 g of NaCl was added to each sample to reduce knocking. The distlillate was titrated with KI2 solution and the CEC (pH 7) calculated.
81 5.6 PARTICLE SIZE DISTRIBUTION
Particle-size distribution was performed on samples using a modification of the pipet method described by Kilmer and Alexander (1949) and Soil Survey Staff (1984).
Samples were pretreated with hydrogen peroxide to remove organic matter. Samples were not filtered to remove dissolved mineral material and overnight shaking was replaced by mixing for 3 minutes on a milk shake mixer. Silt content was determined as the difference between the sample weight and the weight of the clay and sand fractions.
The total sand fraction was further separated by dry sieving through a nest of sieves having opening of 1000, 500, 250, 100, and 50 microns.
5.7 BULK DENSITY
Bulk density of saprolite and rock density was determined by the clod method (Blake and
Hartge, 1986). The volumes of the air-dry clods of saprolite ranged in size from 10.49 mL to 232.19 mL, with a mean and standard deviation of 89.87 ± 55.47 mL. Rock density was determined using 27 samples. The volume ( X ± s) of the rock samples was
51.89 ± 11.38 mL.
5.8 MINERALOGICAL ANALYSES OF RANDOMLY-ORIENTED SPECIMENS
OF SAND- AND SILT-SIZED FRACTIONS AND ORIENTED SPECIMENS
OF CLAY-SIZED FRACTIONS OF SAPROLITE USING X-RAY
DIFFRACTION
Organic matter in the fine-earth fraction of air-dried saprolite was destroyed using NaOCl and heating in a water bath for 15 minutes at 80oC. The samples were subsequently 82 deferrated by heating with a premixed solution of Na-citrate/bicarbonate at 75oC-80oC for several minutes. The deferrated sand-sized fraction was ground in a mortar and pestle to pass a 170 - mesh (90 µm) sieve. The size of the deferrated silt-sized fraction was not reduced by grinding. Randomly-oriented grain mounts of the silt-sized fraction and the ground-up sand-sized fraction were prepared by pouring sample on a glass slide that had double sided sticky tape attached. The slides were X-rayed at 25oC over the 2θ interval 0
to 60 degrees.
Duplicate samples of the deferrated clay-sized fraction were saturated with K or Mg prior to analysis. One sample was washed in 25 mL of 1 mol L-1 KCl, its duplicate in 25 mL
-1 of 1 mol L MgCl2. In each case, the sample was dispersed using sonication, centrifuged at 7500 RPM for 10 minutes, and the supernatant discarded. This was repeated thrice. The saturated clay was washed free of salt using distilled water. Three to five washings were generally necessary, the actual number determined by using
- AgNO3 as a Cl indicator. When washing was complete, the clays were dispersed in
deionized water using a sonicator, and part of the resulting suspension was pipetted onto
a 25 X 75 mm glass microscope slide and allowed to air-dry. The slides thus prepared are oriented specimens as the clay minerals orient themselves with their long axes parallel to the surface of the glass slide upon drying in air. The orientation tends to result in the strong expression of basal peaks.
The K-saturated samples were analyzed at room temperature, and after heating to 350oC, and 550oC, with the same slide being used for the different heat treatments for a given
83 specimen. The Mg-saturated samples were analyzed without further treatment, and also
after saturating with glycerol. Glycerol-saturated samples were prepared by spraying
glycerol onto a separate glass slide containing air-dried Mg-saturated specimen. The
glycerol was sprayed through a sieve to ensure a fine spray until a glossy surface was
present and was subsequently air-dried. The clay-sized samples were X-rayed from 0 to
30 degrees 2θ.
X-ray diffraction analyses were performed on a Rigaku diffractometer employing Ni-
o filtered Cu Kα radiation. A 1 beam divergence slit, a medium resolution Soller slit, and
a diffraction beam monochromator were used in conjunction with a gas-sealed proportional counter. The X-ray tube was operated at 40 kv and 20 ma for all samples.
In all cases, a one-second time constant and a 1000 count-per-second range factor were employed. All diffractograms were recorded at a scanning speed of 2o 2θ per minute and
a recorder speed of 1 inch per minute.
5.9 PETROGRAPHIC EXAMINATION OF GRAIN MOUNTS OF THE SAND –
SIZED FRACTION OF SAPROLITE
A subsample of the whole-sand-sized fraction of each saprolite sample was coverslipped
and immersed in an oil with a refractive index of 1.540 and examined under plane and
cross-polarized light using a 10 magnification occular and 10 magnification objective.
Three hundred grains were counted per specimen. The method used is the line method,
where only mineral grains that intersect with the microscope’s view finder’s cross-hairs
84 during a linear traverse of the grain mount are counted. The traverses were
approximately 2-mm apart. Minerals were identified using the criteria listed below.
Colorless minerals with high relief and a becke line that moved out of the grain when the
microscope’s stage was racked up were identified as the potassium feldspar orthoclase, as
K-feldspar in the Rolesville batholith have been determined to be Or 88-92 by Kosecki and
Fodor (1997). The high relief and the direction of movement of the becke line are due to
the refractive index of orthoclase being significantly lower than that of the immersion oil.
Orthoclase in the samples almost always demonstrated very good 90o cleavage. This
group of minerals occasionally demonstrated microcline twinning indicating the presence
of microcline, which is a potassium feldspar that forms at a lower temperature than
orthoclase. The orthoclase and microcline grains were counted as one category. The potassium feldspar grains showed some alteration along cleavage planes.
Grains with low relief that demonstrated polysynthetic twinning were counted as definitive plagioclase feldspar. The low relief is due to the similar refractive indices
(1.540) of plagioclase and the immersion oil. Plagioclase at the study site was determined to be An 22-14 by Kosecki and Fodor (1997), which is in the range of
oligoclase. The plagioclase feldspar grains almost always demonstrated 90o cleavage.
The outlines of the grains frequently showed differential embayment that corresponded to the different twin lamellae, perhaps reflecting differential susceptibility to weathering related to compositional differences in twin laminae. These grains however, showed no internal alteration as was seen in orthoclase grains. This grain morphology may indicate congruent dissolution of plagioclase during weathering.
85 Colorless minerals with low relief that did not demonstrate polysynthetic twinning were
recognized as potential quartz and potential untwinned plagioclase feldspar (low albite).
From this category of minerals, probable plagioclase was identified by the presence of
90o cleavage, a property of feldspars. Quartz does not possess cleavage. The number of
probable quartz grains was taken as the difference in number between the grains with low relief with an absence of twinning and the probable plagioclase grains. This procedure could overestimate the number of quartz grains as it is possible that untwinned plagioclase grains with no evidence of cleavage could be mistaken for probable quartz.
The total plagioclase content was taken as the sum of the definitive plagioclase grains and probable plagioclase grains. The total plagioclase count could be an underestimate over the true amount of plagioclase by the same amount by which probable quartz is an overestimate over the true quartz amount. Quartz was not identified using its uniaxial positive optical nature because of the time consuming nature of that determination.
Biotite was identified as a brown-colored mineral with a platy habit, while muscovite was identified as a colorless mineral with a platy habit. The XRD analysis revealed that the mineral identified as biotite with the polarizing microscope to be one or more of the minerals biotite, vermiculite or hydroxy-interlayered vermiculite (HIV), randomly or regularly interstratified mica-vermiculite or mica-HIV. As the Na-saturated sand-sized fraction was analyzed by XRD at 25oC, vermiculite could not be distinguished from HIV.
A mineral grain was counted as a pseudomorph when alteration had proceeded to the
point that the identity of the original mineral could not be established. Although
86 pseudomorphs can be detected with the aid of a petrographic microscope, the constituents of pseudomorphs cannot be determined with the aid of a petrographic microscope due to the limits of optical resolution, and therefore XRD must be utilized for this purpose.
5.10 STATISTICAL ANALYSES
The population means at the α confidence level (µ α ) were calculated from sample data
using the relationship
1/2 µ α = X ± { (t α/2) s / [(n) ] }
at n - 1 degrees of freedom, where X represents sample mean, t represents the Student t
distribution, s represents sample standard deviation, and n represents sample size (Keller
and Warrack, 2003, p. 356). Differences between population means were investigated
utilizing the t statistic (assuming equal population variance), aided by statistical software
in the Microsoft® Excel 2000 computer program.
87 CHAPTER 6
PHYSICAL CHARACTERISTICS OF REGOLITH
6.1 MASS DISTRIBUTION OF SAND-, SILT-, AND CLAY-SIZED PARTICLES
The mass distribution of sand-, silt- and clay-sized particles in saprolite is shown in Table
3 and Table 4. Statistical attributes of the particle-size distribution are given in Appendix
II (p. 199).
The mass percent of the > 2 mm air-dry fraction is similar in the A, G and R samples,
whereas it is much higher in the B samples. In the field, the > 2 mm minerals in the B
samples were identified as pink-colored potassium feldspar grains. The content of sand-
sized (2 mm – 0.50 mm) particles – both as a fraction of the fine-earth fraction and as a
fraction of the whole saprolite – is very much higher in the A, B, and R samples than in
the G samples. The content of clay-sized particles is highest in the G samples. The
difference between the mean contents of sand-, silt-, and clay-sized particles of the A and
B population and the G and R population in the fine-earth fraction as well as in the whole
saprolite is statistically significant at α = 0.001. The differences between the means of
the particle-size ratios (sand/silt, sand/clay, and silt/clay – all on a whole saprolite basis)
of the A and B population and the G and R population are also statistically significant at
the α ≤ 0.05 level of significance, with the difference most significant for the ratio of
sand to silt (α = 0.001).
88 Table 3. Particle size distribution of saprolite (mass percent).
≤ 2 mm fraction Sample Depth >2 mm fraction sand silt clay number (m) 123A 1 0.0 79.1 11.2 9.7 124A 2 0.1 86.6 10.8 2.4 125A 3 0.1 87.0 11.7 1.3 126A 4 0.1 84.7 14.1 1.1
123B 1 8.8 82.2 8.5 0.5 124B 2 10.8 79.3 8.6 1.2 125B 3 10.5 81.0 7.3 1.2 126B 4 9.0 79.6 10.2 1.2
300G * 0.0 10.5 0.3 89.2 301G * 0.1 15.4 0.8 83.7 304G * 0.1 7.7 0.1 92.1
300R * 0.0 79.6 5.4 15.0 301R * 0.0 78.7 4.4 16.8 304R * 0.3 71.1 5.0 23.5
* Sample depth ranged from the surface to about 4m as the samples were collected after exploding the regolith with dynamite.
The differences in the particle size distributions between the groups of saprolite samples
could potentially reflect mineralogical and or textural heterogeneities in the parent rocks or result from differences in weathering. The kaolinite (and or halloysite) abundant in the
G samples (see Chapter 9, and Appendix V-A) could not have been inherited from an unmetamorphosed sedimentary parent material residing within the Rolesville granitic batholith. The differences in the clay contents between the G and R samples cannot be attributed to a variation in the content of primary aluminosilicates in the parent rocks as the gray- and red-colored saprolite layers were horizontally oriented in the field whereas the weak micaceous foliation in the rocks dipped steeply. For that same reason, it is unlikely that the differences in sand / silt reflect parent rock heterogeneity.
89 Table 4. Ratios between masses of selected particle-size fractions on a whole saprolite basis.
Sample Depth Sand / silt Sand / clay Silt / clay number (m) 123A 1 7.1 8.2 1.2 124A 2 8.0 36.1 4.5 125A 3 7.4 66.9 9.0 126A 4 6.0 77.1 12.8
123B 1 9.7 180.4 18.6 124B 2 9.2 63.5 6.9 125B 3 11.0 69.6 6.3 126B 4 7.8 67.3 8.6
300G * 35.0 0.1 0.0 301G * 19.2 0.2 0.0 304G * 77.0 0.1 0.0
300R * 14.7 5.3 0.4 301R * 17.9 4.7 0.3 304R * 14.3 3.0 0.2
* Sample depth ranged from the surface to about 4m as the samples were collected after exploding the regolith with dynamite.
Sample mineralogy (see Chapter 9) provides additional evidence for the similarity in
parent materials of all saprolite samples. The dominant primary minerals in all saprolite samples were potassium feldspar, plagioclase feldspar and quartz – all of which were the main primary minerals identified in the granite at the study site by Kosecki and Fodor
(1997) (see Table 2, page 76). Small amounts of apatite and monazite were also detected
in one or more size fractions in most saprolite samples (See Table 22, p. 139). In
addition, petrographic examination of the sand-sized fractions of saprolite (See Table 14,
page 115) revealed that zircon was absent in all samples except for a very minor amount
90 (0.3 number percent) in one sample. Primary mineralogy therefore suggests similarity of parent materials.
The variation in the silt content as well as sand / silt ratio can be interpreted in terms of weathering rate. A fundamental variable that is central in any (chemical) rate law whether at the atomic scale or the field scale is reactive surface area (Lasaga, 1995, p.
33). For a given primary mineral phase, a silt-sized primary mineral can be considered to be more reactive per unit mass than a sand-sized primary mineral if identical particle shapes are assumed. This is due to increasing surface area per unit mass with decreasing particle size. For a spherical particle, the dependence of the solubility of a particle
(c, arbitrary units) relative to the bulk solubility of the substance (co, arbitrary units) in terms of the radius of the particle (r, cm), surface free energy (σ, erg cm-2), volume of the solid (V, cm3), geometric factor (B, 16.8 for spheres), Universal gas constant (R), and temperature (T) is given by ln (c/co) = [(2/3) 10-7 σ V B] / (rRT)
(Dove, 1995, p. 247). Thus, the distribution of silt-sized particles can be considered to be a sensitive indicator of the regolith’s water content. The mean content of silt-sized particles in saprolite developed from granite with steeply-dipping joints is higher than in saprolite developed from granite with horizontally-oriented unloading joints (see
Table 3). The higher silt content in the former saprolite suggests decreased water availability in that weathering environment. Unlike sand / silt ratio, it is more difficult to interpret silt / clay ratio as it would depend not only on water availability, but also on mass eluviation from the weathering environment. Radwanski and Ollier (1959, p. 159)
91 stated that “very low silt contents are a characteristic shared by many tropical soils, in which rapid and intense weathering seems to result in a more or less direct transformation of feldspars to clay with insignificant proportions of silt being formed”.
6.2 PARTICLE SIZE DISTRIBUTION OF SAND SUBFRACTIONS
The particle size distribution within the sand-sized fraction of saprolite is shown in
Table 5 (see also Appendix II-C through II-G). The distribution is unimodal for the A,
B, and R samples, and is essentially unimodal distribution for the G samples. The mode of the A sample group is in the fine-sand particle size-interval, whereas for the B sample group it is in the coarse-sand particle-size interval. Within saprolite developed from granite with unloading joints, the dominant mode of the sand-sized subfractions for the gray-colored samples is in the fine-sand particle-size interval, with a minor mode in the coarse-sand particle-size interval. In the red-colored samples – which have also developed from granite with horizontally oriented unloading joints, the mode of the sand- sized subfractions is in the coarse-sand particle-size interval.
The difference in the means of the sand subfractions as a fraction of the weight of the sand-sized fraction between the population from which the A and B samples were collected and the population from which the G and R samples were collected are not statistically significant at the α = 0.05 level except for the coarse sand fraction.
However, when the sand subfractions are expressed as a fraction of both the fine-earth fraction of saprolite as well as on a whole saprolite basis, the difference between the
92 means of the sand subfractions is statistically significant at the α ≥ 0.05 level for the medium sand, fine sand, and very fine sand subfractions.
Table 5. Particle size distribution within the sand-sized fraction of saprolite expressed as mass percent of the total sand-sized fraction of saprolite.
Sand-sized fraction (2.0 mm – 0.50 mm)
Sample Depth number (m) Very Coarse Coarse Medium Fine Very Fine Sand Sand Sand Sand Sand 2.0 -1.0 1.0 - 0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm
123A 1 0.9 17.4 34.1 33.6 14.1 124A 2 1.5 23.6 29.5 32.1 13.3 125A 3 0.6 15.8 35.9 35.1 12.7 126A 4 0.8 16.8 29.7 35.1 17.6
123B 1 21.4 26.3 24.9 18.8 8.7 124B 2 19.4 28.1 22.9 18.5 11.3 125B 3 24.6 30.4 22.3 15.0 7.5 126B 4 21.1 29.6 20.7 17.2 11.4
300G * 9.0 21.7 22.6 28.1 18.6 301G * 9.1 24.8 24.1 26.0 16.1 304G * 15.7 19.6 18.9 26.0 19.7 * 300R 13.5 34.0 25.5 18.7 8.3 301R * 14.1 31.8 25.8 19.3 9.0 304R * 14.5 32.6 26.1 18.5 8.2
* Sample depth ranged from the surface to about 4m as the samples were collected after exploding the regolith with dynamite.
6.3 BULK DENSITY
Bulk density of saprolite is shown in Table 6. Bulk density (g cm-3) of saprolite developed from granite with steeply-dipping joints ranged from 1.57 to 1.78, and the bulk density of saprolite developed from granite with horizontally-oriented unloading joints 93 Table 6. Bulk density of saprolite. Bulk Density Sample Depth Number of samples (oven dry), g/ cm3 number (m) analyzed
X ± s µ α 0.05
123A 1 3 1.58 ± 0.03 124A 2 3 1.57 ± 0.02 125A 3 3 1.60 ± 0.03 1.61 ± 0.09 126A 4 3 1.69 ± 0.04
123B 1 2 1.71 ± 0.02 124B 2 3 1.78 ± 0.01 125B 3 3 1.68 ± 0.01 1.71 ± 0.08 126B 4 3 1.68 ± 0.01
300G * 3 1.50 ± 0.00 301G * 3 1.49 ± 0.01 304G * 4 1.52 ± 0.01 1.50 ± 0.04
Red (R) samples * **6 1.57 ± 0.02 1.57 ± 0.02
A and B 1.66 ± 0.06
G and R * ***6 1.55 ± 0.00 1.55 ± 0.01
COMPARISON OF POPULATION MEANS
µA&B ≠ µG&R (A&B) vs (G&R)* (α 0.01)
X =sample mean; s = sample standard deviation; µ α 0.05 = population mean at 95 % confidence level; * Sample depth ranged from the surface to about 4 m as the samples were collected after exploding the regolith with dynamite. ** Due to the fragile nature of the thin (1 – 2 cm) sandy textured R samples, bulk density for the R samples was determined using the 6 clods identified as *** which contained gray-colored and red-colored layers. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed. *** Samples different from samples 300, 301, and 304. These were clods composed of multiple gray-colored and red-colored layers.
94 ranged from 1.49 (for a gray-colored layer) to 1.57 (for the red-colored layers). The mean value of bulk density for the A and B population is higher than that of the G and R population, and the difference between the population means is statistically significant at
α = 0.01.
The physical properties of regolith developed from granite with contrasting joint patterns are dissimilar. Saprolite developed from granite with steeply-dipping joints is composed predominantly of sand-sized particles. In contrast, saprolite layers developed from granite with horizontally oriented unloading joints shows strong textural contrasts. In addition, bulk density values of the former regolith are higher. These observations would
suggest that the former saprolite may be chemically less altered. Mass alteration and its
partitioning between the saprolite and its environment are quantified in the next chapter.
Although differences in bulk density between saprolite developed from granite with
contrasting joint patterns were found to differ at α = 0.01, results presented in the next
chapter show that differences in mA/VT are greater than the difference in bulk density
would suggest.
95 CHAPTER 7
MASS ALTERATION AND ITS PARTITIONING BETWEEN
SAPROLITE AND ITS ENVIRONMENT
It is hypothesized in this study that isovolumetrically weathered regolith formed in
weathering environments characterized by different joint patterns can be expected to vary in the amount of mass altered per unit volume (mA/VT) as well as in how the altered mass
is partitioned (mAL/VT and mAR/VT) between the weathering system and its environment, leading to variation in altered mass lost per unit mass altered (mAL/mA) as well as in
altered mass retained per unit mass altered (mAR/mA). This chapter discusses these
parameters for the saprolite investigated in this study.
7.1 CALCULATING MASS ALTERED PER UNIT VOLUME
The particle-size distribution of isovolumetrically weathered regolith can be related to
mass altered per unit volume (mA/VT) if the following assumptions are made:
(1) Primary minerals do not elluviate during the course of weathering. Mass is lost
from a weathering system only by the eluviation of ions and secondary minerals.
(2) Mass that illuviates to the weathering system in the form of secondary minerals or
ions is negligible.
Under these conditions, the value of mA/VT required to obtain a given mass distribution of primary and secondary minerals at a given value of bulk density (ρb) for a rock with a
given initial density (ρs) can be calculated using the following equations that were
developed in Chapter 3:
96 mass % primary minerals = 100 [ρs - (mA/VT)] / ρb (8) and mass % secondary minerals = 100 [(mA/VT) - (ρs - ρb)] / ρb (11)
Determining the mass of primary minerals and the mass of secondary minerals
can be difficult for regolith that contains primary phyllosilicates that are regularly- or
randomly-interstratified with secondary phyllosilicates, contains clay-sized primary
minerals as well as and sand-sized pseudomorphs of primary minerals. In view of this, it
is profitable to consider under what conditions the mass distribution of primary and
secondary minerals is approximated by the particle-size distribution of the whole regolith.
Under the following conditions, the mass distribution (percent) of primary minerals is
approximated by the mass distribution of sand-sized and larger fractions, and the mass
distribution (percent) of secondary minerals is approximated by the mass distribution of
the clay-sized fraction:
(1) Primary minerals in the unweathered rock are all of sand-size (2 mm - 0.05) or larger.
(2) Mass of secondary minerals occurring in the sand-sized and larger fractions in
the form of pseudomorphs is minimal.
(3) The clay-sized fraction is composed mostly of secondary minerals.
(4) Mass of the silt sized fraction is minor compared to that of the sand-sized and clay-
sized fractions.
The grain sizes of major modal minerals in the foliated biotite-rich granitoid and
nonfoliated granite found at the study site are mainly 0.5 to 3 mm (Kosecki and Fodor,
97 1997), which places these minerals in the coarse sand or larger size fractions, complying
with condition (1). The pseudomorph number percent (Table 7 ) within the sand-sized fraction for the A and B samples ranges from 5.0 to 13.0, except for one sample with a value of 19.1. For the G and R samples as a whole, the number is lower, ranging from
0.7 to 4.0, with one value of 6.7. As discussed in Section 9.1, it is difficult to establish a relationship between number percent of a mineral and its abundance in terms of mass percent (or volume percent) due to different sizes, shapes and densities of minerals.
Condition (2) can be considered to be approximately satisfied for the A and B samples and fairly well met for the G and R samples.
Condition (3) is satisfied by the satisfaction of condition (1) coupled with the rapid transformation of sand-sized primary minerals into clay-sized secondary minerals.
X-ray diffraction revealed that the clay-sized fraction of all samples is composed predominantly of kaolinite and / or halloysite and or either or both of these minerals randomly interstratified with hydroxy-interlayered vermiculite (see Section 9.6). In addition, examination of the particle-size data (Table 3, p. 89) shows that the mass percent silt in the fine-earth fraction for the A and B samples ranges from 8.5 to 14.1.
For the R samples, mass percentage of silt ranges from 4.4 to 5.4, whereas for the G samples, the mass percent silt ranges from 0.1 to 0.8 percent. Condition (4) can therefore be considered to be approximately satisfied by the A and B samples, satisfied to a greater degree by the R samples, and even more completely satisfied by the G samples.
98 Table 7. Pseudomorph distribution in the sand-sized fraction of saprolite.
Sample number Depth (m) Pseudomorphs (number %) 123A 1 19.1 124A 2 12.4 125A 3 11.4 126A 4 5.0
123B 1 9.9 124B 2 8.9 125B 3 13.0 126B 4 11.6
300G * 3.7 301G * 3.3 304G * 6.7
300R * 0.7 301R * 4.0 304R * 1.0
COMPARISON OF POPULATION MEANS
(A&B) vs (G&R) µA&B ≠ µG&R (α 0.01)
(A&B)** vs (G&R) µA&B ≠ µG& (α 0.001 )
* Specific sample depth is not known. Probable depths ranged from the surface to 4 m as these samples were collected after exploding the regolith with dynamite. ** Excluding sample 123A
Mass altered per unit volume calculated using the equation
mass % primary minerals = 100 [ρs - (mA/VT)] / ρb (8) in conjunction with the whole-saprolite particle-size data presented in Table 3 is shown in
Table 8 .
99 Table 8. Mass altered per unit volume (mA/VT) of isovolumetrically weathered regolith.
-3 Calculation is based on an initial rock density of 2.62 g cm (µ α 0.05 = 2.62 ± 0.01).
-3 Sample Depth mA/VT (g cm ) Number (m) Sample values µ and Group X (± s) α 0.05
123A 1 1.37 124A 2 1.26 1.26 ± 0.08 1.26± 0.12 125A 3 1.23 126A 4 1.18
123B 1 1.07 124B 2 1.02 1.08 ± 0.05 1.08 ±0.08 125B 3 1.09 126B 4 1.14
300G * 2.47 301G * 2.39 2.46 ± 0.06 2.46 ±0.17 304G * 2.50
300R * 1.37 301R * 1.38 1.42 ± 0.07 1.42 ±0.22 304R * 1.50
A & B 1.17 ±0.13 1.17 ±0.12
G & R** 1.85 ±0.06 1.85 ±0.15
X =sample mean; s = sample standard deviation; µ α 0.05 = population mean at 95 % confidence level;
* Samples were collected after exploding regolith with dynamite. Probable sample depths ranged from the soil surface to 4 m. ** Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
100 7.2 CALCULATING ALTERED MASS LOST PER UNIT VOLUME
Altered mass lost per unit volume (mAL/VT) was calculated using the equation
(mAL / VT) = ρs - ρb (5)
Calculated values of mAL / VT and mAL / mA are shown in Table 9.
7.3 CALCULATING ALTERED MASS RETAINED PER UNIT VOLUME
Altered mass retained per unit volume (mAR/VT) was calculated using the equation
mA/VT = (mAR + mAL )/ VT (1) by substituting values for mA / VT from equation (8) and values for mAL / VT from equation(5). Calculated values of mAR/VT and mAR/mA are shown in Table 10.
101 Table 9. Altered mass lost per unit volume (mAL/VT) and altered mass lost per unit mass altered (mAL/ mA) in isovolumetrically weathered regolith.
-3 Calculations are based on an initial rock density of 2.62 g cm (µ α 0.05 = 2.62 ± 0.01).
mAL/VT mAL/ mA Sample Depth g cm-3 g g -1 cm3 cm-3 Number (m) Sample X ± s µ α 0.05 Sample X ± s µ α 0.05 and Group values values
123A 1 1.04 0.76 124A 2 1.05 1.01 1.01 0.83 0.80 0.80 125A 3 1.03 ±0.06 ±0.09 0.83 ±0.04 ±0.06 126A 4 0.93 0.78
123B 1 0.92 0.86 124B 2 0.85 0.91 0.91 0.83 0.85 0.85 125B 3 0.94 ±0.05 ±0.08 0.87 ±0.02 ±0.03 126B 4 0.95 0.83
300G * 1.13 1.12 1.12 0.46 301G * 1.13 ±0.02 ±0.04 0.47 0.46 0.46 304G * 1.10 0.44 ±0.02 ±0.04
300R * 1.04 1.04 1.04 0.76 301R * 1.04 ±0.02** ±0.04 0.76 0.74 0.74 304R * 1.04 0.70 ±0.04 ±0.09
A & B 0.96 0.96 0.82 0.82 ±0.07 ±0.06 ±0.04 ±0.03
G & R*** 1.08 1.08 0.58 0.58 ±0.01 ±0.02 ±0.02 ±0.06
X =sample mean; s = sample standard deviation; µ α 0.05 = population mean at 95 % confidence level;
* Samples were collected after exploding regolith with dynamite. Probable sample depths range from the surface to 4 m. ** The average value of bulk density determined using six red colored samples other than 300R, 301R, and 304R was used to calculate mAL/VT. It is assumed that the standard deviation of mAL/VT is equal to the standard deviation of bulk density. *** Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
102 Table 10. Altered mass retained per unit volume (mAR/VT) and altered mass retained per unit mass altered (mAR/ mA) in isovolumetrically weathered regolith.
mAR/VT mAR/ mA Sample Depth g cm-3 g g –1cm3 cm-3 Number (m) Sample X ± s µ α 0.05 Sample X ± s µ α 0.05 and values values Group
123A 1 0.33 0.24 124A 2 0.21 0.25 0.25 0.17 0.20 0.20 125A 3 0.21 ±0.06 ±0.09 0.17 ±0.04 ±0.06 126A 4 0.28 0.22
123B 1 0.15 0.14 124B 2 0.18 0.17 0.17 0.17 0.15 0.15 125B 3 0.14 ±0.02 ±0.04 0.13 ±0.02 ±0.03 126B 4 0.19 0.17
300G * 1.34 1.33 1.33 0.54 0.54 0.54 301G * 1.26 ±0.07 ±0.18 0.52 ±0.02 ±0.04 304G * 1.40 0.56
300R * 0.32 0.63 0.63 0.24 0.26 0.26 301R * 0.34 ±0.07 ±0.18 0.24 ±0.04 ±0.09 304R * 0.45 0.30
A & B 0.21 0.21 0.18 0.18 ±0.06 ±0.05 ±0.04 ±0.03
G & R 0.77 0.77 0.42 0.42 ** ±0.07 ±0.17 ±0.02 ±0.06
X =sample mean; s = sample standard deviation; µ α 0.05 = population mean at 95 % confidence level;
* Samples were collected after exploding regolith with dynamite. Probable sample depths ranged from surface to 4 m. ** Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
103 7.4 VARIATION OF mA/VT, mAL/VT, mAR/VT, mAL/mA AND mAR/mA WITH
WEATHERING ENVIRONMENT
The A and B samples are from a weathering environment characterized by the presence
of relict, steeply-dipping joints. The G and R samples are from a weathering
environment characterized by the presence of horizontally-oriented unloading joints. The
A, B, G and R sample groups can be considered as representing different weathering
subenvironments, where as A and B samples taken together and G and R samples taken
together can be considered as representing different weathering environments. Table 11
shows the statistical significances associated with differences between the population
means of several weathering characteristics within weathering subenvironments and
between weathering environments. Comparison of population means between
weathering subenvironments (such as A vs B, and G vs R) helps elucidate heterogeneity within a weathering environment. Comparison of population means between weathering
environments (such as [A and B] vs [G and R]) helps elucidate heterogeneity between weathering environments.
For each of the five parameters shown in Table 11, the difference between the population means of the A and B weathering subenvironments is statistically less significant than those between the G and R weathering subenvironment. This suggests that the A and B weathering environment can be considered as being more homogeneous than the G and R weathering environment.
104 Table 11. Comparison of population means for the parameters mA/VT, mAL/VT, mAR/VT, mAL/ mA and mAR/ mA within weathering subenvironments and between weathering environments.
Weathering Population mA/VT mAL/VT mAR/VT mAL/ mA mAR/ mA Environment
A and B A vs B µA ≠ µB µA ≠ µB µA ≠ µB µA ≠ µB µA ≠ µB (α 0.05) (α 0.05) (α 0.05) (α 0.10) (α 0.05)
G and R G vs R µG ≠ µR µG ≠ µR µG ≠ µR µG ≠ µR µG ≠ µR (α 0.001) (α 0.01) (α 0.001) (α 0.001) (α 0.001)
µA&B µA&B µA&B µA&B µA&B (A&B) (A&B) ≠ ≠ ≠ ≠ ≠ and vs µG&R µG&R µG&R µG&R µG&R (G&R*) (G&R*) (α 0.001) (α 0.05) (α 0.001) (α 0.001) (α 0.001)
* Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
The data in the table shows that the population means for the parameters mA/VT, mAR/VT, mAL/ mA, and mAR/ mA of the A and B samples taken together differ from those of the G
and R samples at the 99.9 % probability level (α 0.001). However, between these two
population groups, the difference between the means for mAL/VT is statistically less
significant. This suggests that, of all the weathering parameters shown in Table 11, mAL/VT is the least sensitive indicator for distinguishing between the two weathering
environments.
105 The statistical comparison of the population means between the weathering environments
as well as within the G and R weathering subenvironment would be influenced by errors in the determination of the volumetric ratio in which the gray-colored and red-colored
layers constitute the saprolite. The population means were compared for the range of
saprolite compositions ranging from 90 % by volume red layers and 10 % by volume
gray layers, to 10 % by volume red layers and 90 % by volume gray layers. The
statistical significance of the differences between the means was found to be unaffected for the parameters mA/VT, mAR/VT, mAL/mA, and mAR/ mA. However, the statistical
significance of the difference between the population means for mAL/ VT ranged from
0.10 to 0.01. This suggests that although mAL/VT is the least sensitive indicator for
distinguishing between the two weathering environments of all the parameters shown in
Table 11, it is also the most sensitive to errors in the determination of the volumetric
distribution of gray- and red-colored layers.
Sandy-textured saprolite has been interpreted by some researchers to indicate a relatively
unaltered regolith. For example, Dixon and Young (1981) described deep arenaceous
weathering mantles on granites and granodiorites of the Bega batholith in southeastern
Australia in which the sand-sized (> 63 µm) content of the grus ranged from 54 – 86%.
They recognized the original granitic composition with the naked eye and stated that the
rock seemed to have undergone little chemical alteration. However, estimates of
chemical alteration based purely on textural criteria can be misleading. For example, the calculated value of mA/ VT in the sandy-textured A and B saprolite samples investigated
in this study was ( X ± s) of 1.17 ±0.13 g cm-3. Taking the original rock density as 2.62
106 g cm-3 (see Table 8, p. 100) indicates that 44.7 % of the original mass has been altered.
-3 The mAL/mA value of 0.82± 0.04 g cm ( X ± s) for this group of samples indicates that
82% of altered mass has been leached, resulting in the sandy-texture
107 CHAPTER 8
CHEMICAL CHARACTERISTICS OF REGOLITH
Chemical characteristics determined for the saprolite are shown in Table 12. Statistical attributes of the chemical characteristics are shown in Table 13.
Table 12. Chemical characteristics of the untreated fine-earth fraction.
Sample Depth pH Extractable Bases CEC % Mass Mass % (m) ___ cmol+ kg-1 cmol+ BS % Free Iron -1 1:5 H2O ______kg pH 7.0 Clay (Fe2O3) Ca Mg Na K pH 7.0 <2 ( X ± s)** µm 123A 1 5.2 0.4 0.7 0.1 0.2 6.0 23.4 9.7 0.46 ± 0.00 124A 2 5.7 0.2 0.5 0.1 0.1 4.5 22.4 2.4 0.24 ± 0.01 125A 3 5.8 0.8 0.6 0.1 0.1 3.5 44.2 1.3 0.22 ± 0.00 126A 4 5.9 1.4 0.5 0.1 0.1 4.5 47.4 1.1 0.11 ± 0.00
123B 1 5.7 0.4 0.4 0.1 0.1 4.1 22.9 0.5 0.17 ± 0.00 124B 2 5.8 0.4 0.5 0.1 0.1 2.9 37.6 1.4 0.14 ± 0.00 125B 3 6.0 0.6 0.6 0.1 0.1 2.9 48.4 1.3 0.16 ± 0.01 126B 4 5.9 0.9 0.5 0.1 0.1 3.3 47.0 1.3 0.15 ± 0.00
300G * 4.8 1.4 1.0 0.1 0.2 12.8 21.3 89.2 2.25 ± 0.06 301G * 5.0 0.9 0.9 0.1 0.2 11.7 18.2 83.8 1.90 ± 0.29 304G * 5.0 1.8 1.1 0.1 0.3 12.5 26.7 92.2 2.40 ± 0.32
300R * 5.1 0.4 0.3 0.1 0.1 5.3 15.9 15.0 2.86 ± 0.07 301R * 5.2 0.3 0.3 0.1 0.1 5.3 13.4 16.8 3.09 ± 0.13 304R * 5.3 0.6 0.4 0.1 0.1 5.9 19.3 23.6 3.20 ± 0.07
X =sample mean; s = sample standard deviation; * samples were collected after exploding regolith with dynamite. Probable sample depths ranged from the surface to 4 m. ** Standard deviation is based on the analysis of triplicate samples, except for sample 304R, which is based on a duplicate analysis.
108 Table 13. Statistical attributes of chemical characteristics of the untreated fine-earth fraction.
Sam pH CEC Extractable Bases (cmol+ kg-1) Mass % -ple pH 7.0 Free
Group cmol+ kg-1 Iron Ca Mg Na K % BS (Fe O ) pH 7.0 2 3 X 5.6 4.62 0.70 0.59 0.10 0.13 34.35 0.26 A s 0.3 1.03 0.51 0.11 0.01 0.04 13.31 0.15 µ 5.6 4.62 0.70 0.59 0.10 0.13 34.35 0.26 ± 0.5 ± 1.63 ± 0.82 ± 0.17 ± 0.01 ± 0.06 ± 21.17 ± 0.24 α 0.05 X 5.8 3.28 0.58 0.48 0.07 0.11 38.87 0.15 B s 0.1 0.56 0.24 0.09 0.00 0.02 11.74 0.01 µ 5.8 3.28 0.58 0.48 0.07 0.11 38.87 0.15 ± 0.2 ± 0.91 ± 0.38 ± 0.15 ± 0.01 ± 0.02 ± 18.67 ± 0.02 α 0.05
X 4.9 12.34 1.39 0.97 0.13 0.24 22.06 2.18 G s 0.1 0.55 0.46 0.11 0.00 0.04 4.28 0.25 µ 4.9 12.34 1.39 0.97 0.13 0.24 22.06 2.18 ± 0.3 ± 1.37 ± 1.14 ± 0.28 ± 0.01 ± 0.10 ± 10.64 ± 0.63 α 0.05 X 5.2 5.52 0.43 0.30 0.08 0.09 16.19 3.05 R s 0.1 0.36 0.15 0.05 0.01 0.02 2.93 0.18 µ 5.2 5.52 0.43 0.30 0.08 0.09 16.19 3.05 ± 0.2 ± 0.90 ± 0.37 ± 0.13 ± 0.02 ± 0.05 ± 7.28 ± 0.44 α 0.05
X 5.8 3.95 0.64 0.53 0.09 0.12 36.66 0.21 A&B s 0.2 1.05 0.38 0.11 0.02 0.03 11.88 0.11 µ 5.8 3.95 0.64 0.53 0.09 0.12 36.66 0.21 ± 0.2 ± 0.88 ± 0.32 ± 0.09 ± 0.01 ± 0.02 ± 9.93 ± 0.09 α 0.05
X 5.1 8.28 0.82 0.57 0.10 0.15 19.73 2.68 G&R* s 0.2 0.37 0.28 0.07 0.01 0.03 3.71 0.11 µ 5.1 8.28 0.82 0.57 0.10 0.15 19.73 2.68 ± 0.2 ± 0.91 ± 0.69 ± 0.19 ± 0.02 ± 0.07 ± 9.22 ± 0.28 α 0.05
COMPARISON OF POPULATION MEANS
Cannot Cannot Cannot Cannot reject reject reject reject
(A&B) µA&B µA&B µA&B µA&B µA&B µA&B µA&B µA&B vs ≠ ≠ = = = = ≠ ≠ (G&R) µG&R µG&R µG&R µG&R µG&R µG&R µG&R µG&R * α α 0.001 α 0.05 α 0.05 α 0.05 α 0.05 α 0.05 α 0.001 0.001
X = sample mean; s = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. * Except for pH, adjusted to represent the volumetric ratio in which the R and G samples were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed. 109 8.1 SOIL REACTION (pH)
The pH values of gray layers are always slightly less than the pH values of the red layers.
In the A samples, pH increases with depth. In the B samples pH values increases with depth from 1 to 3 m, then decreases very slightly at 4 m. The A and B samples are less acidic than the G and R samples. The mean pH values of the A and B population differs from the mean pH values of the G and R population at the α = 0.001 level of significance.
8.2 CATION EXCHANGE CAPACITY
Cation exchange capacity (CEC, in cmol+ kg -1 fine-earth fraction) at pH 7.0 for both A
and B samples are similar and shows no apparent trend with depth, although at any given
depth, the CEC of the A sample is slightly higher than that of the B sample. In the
saprolite developed from granite with horizontally-oriented unloading joints, the CEC of
each gray layers is always higher than that of the associated red layer. The mean CEC of
the A and B population differs from that of the G and R population at the α = 0.001 level
of significance.
The high values of CEC given the low content of clay-sized particles in the A and B
samples cannot be attributed to the presence of organic matter as organic matter was
removed from all samples prior to analysis. Therefore, a significant component of the
CEC in these samples must reside in the silt- and sand-sized fractions. Amoozegar et al.
(1993) made similar observations in various saprolites of North Carolina. A component
of the CEC in the sandy-textured A and B samples can be attributed to the presence of
110 pseudomorphs (see Table 7, page 99) located within the sand-sized fractions of these
samples. Ruxton and Berry (1957) reported that in the Zone 11 of their granite in Hong
Kong, which often contained roughly equal amounts of core stones, gruss, and residual
debris, although clay-sized grains seldom exceed 5 percent, the weathered granite
contained abundant clay minerals – dominantly sericite and kaolinite. In a Charlton soil
in Connecticut, Hill and Sawhney (1969) observed that although weathered biotite sand
grains constituted only 1.6% of the whole soil, they contributed about 15% of the total
exchange capacity. In saprolite developed from a mylonite developed from a biotite –
garnet gneiss near Quebec City, Canada, the CEC ranged from 9.5 to 47.2 mequiv / 100 g
of the <2 mm material (De Kimpe et al., 1985). They did not observe a correlation
between the CEC and the clay content. They noted that silt and sand fractions of samples
that contained vermiculitized mica flakes had high CEC values.
8.3 EXTRACTABLE BASES
The extractable base content is highest in the G samples. The extractable Ca increases with depth in the A and B samples from 2 m to 4 m whereas the extractable Mg and K
values are fairly constant with depth. In all saprolite samples, extractable Na is very low
(e.g., 0.1 cmol+ kg-1). This can be attributed to the extremely high solubility of Na+. The
differences between the mean values of individual extractable bases of the A and B
population do not differ from those of the G and R population at the α = 0.05 level of
significance.
111 8.4 PERCENT BASE SATURATION (% BS)
With some minor exceptions, the % BS in both the A and B samples shows a general
increase with depth. The % BS in any gray-colored sample is higher than in the
associated red-colored sample. However, the difference in the mean of % BS of the G population is not different from that of the R population at the α = 0.05 level of significance. The mean value of % BS in the A and B samples is higher than in the G and R samples and the mean value of % BS of the A and B population differs from that of the G and R population at the α = 0.05 level of significance.
8.5 MASS PERCENTAGE OF CITRATE-BICARBONATE-DITHIONITE
EXTRACTABLE (FREE) IRON
The mass percent of Fe2O3 shows a clear decrease with depth in the A samples, whereas
it is fairly constant with depth in the B samples. The mass percent of Fe2O3 in the A and
B samples is much less than in the G and R samples, and the mean mass percent of Fe2O3
of the A and B population differs from that of the G and R population at the α = 0.001
level of significance.
The mass percentage of Fe2O3 in the red-colored samples (R samples) is higher than in the associated gray-colored samples (G samples), and the difference in the means between the G and R populations is statistically significant at the α = 0.01 level of significance. However, the difference in the content of Fe2O3 between the red- and gray- colored layers is less than expected given the difference in color (see Figure 11, page 79).
This can be attributed to the difference in the clay contents between these two groups of 112 samples and the resulting difference in surface area per unit volume of saprolite. The
clay content ( X ± s) (mass percent) of the fine-earth fraction of the G samples is 88.3 ±
7.3 and that of the R samples is 18.4 ± 4.5 (see Appendix II-A, page 199). The slightly
lower content of Fe2O3 in the G samples spread over a larger surface due to the higher
clay content results in less intense staining of the particle than is expected for the given
concentration of Fe2O3. The intense red coloration in the R layers can be attributed to the
distribution of a slightly higher (though statistically significant) concentration of Fe2O3
over a smaller surface area. However, a generalization between color and texture of
saprolite cannot be made due to variation in the content of Fe-containing minerals in rocks as well as due to variation in redox conditions between different weathering environments.
113 CHAPTER 9
REGOLITH MINERALOGY
The mineralogy of the saprolite samples was investigated in order to determine if any
mineralogical differences exist between the saprolites developed from granite with
different joint orientations. The (whole) sand-sized fraction was examined by polarizing
microscope, and all three size fractions of the fine-earth portion of saprolite were
analyzed by X-ray diffraction.
9.1 PETROGRAPHIC EXAMINATION OF GRAIN MOUNTS OF THE SAND –
SIZED FRACTION OF SAPROLITE
The number percentages of various minerals and particles encountered in the
petrographic examination of the whole sand-sized fraction based on a count of 300 grains by the line method are presented in Table 14. It is important to recognize that a correlation does not exist between number percent of a mineral and its weight percent owing to the absence of a correlation between number percent and volume percent coupled with variations in mineral density.
The very high proportion of biotite listed in Table 14 results from two factors. One is the platy habit of the mineral, which results in biotite grains occupying a relatively large area per grain in the plane of examination. The second factor is the relative ease with which biotite flakes exfoliate and break in the course of sample handling. Exaggerated as the
114 biotite count may be, it is useful in establishing the presence of this mineral in the sand- sized fraction of saprolite.
Table 14. Minerals and particles identified using petrographic microscope and their number percent in the (whole) sand-sized fraction of saprolite.
Number percent is based on a count of 300 grains using the line method.
Plagioclase feldspar Sample Quartz K- Felds Biot2 Musc PSM Opaq Zir number Prob1 Twin Prob1 Total felds Total
123A 18.5 2.6 3.4 6.0 8.3 14.3 47.3 0.8 19.1 0.0 0.0 124A 20.0 1.3 10.5 11.8 11.5 23.3 42.3 1.6 12.4 0.3 0.0 125A 22.5 2.3 13.7 16.0 12.4 28.4 34.3 2.6 11.4 0.6 0.0 126A 21.7 3.4 11.5 14.9 15.5 30.4 41.6 0.9 5.0 0.3 0.0 X ± s 20.7 12.2 11.9 24.1 41.4 1.5 12.0 0.3 0.0 ± 1.8 ± 4.5 ± 3.0 ± 7.2 ± 5.4 ± 0.8 ± 5.8 ± 0.2 ± 0.0
123B 12.2 4.6 21.1 25.7 8.9 34.6 39.9 2.6 9.9 0.7 0.0 124B 20.4 6.6 10.5 17.1 13.2 30.3 36.8 3.3 8.9 0.3 0.0 125B 19.8 4.0 12.5 16.5 7.9 24.4 37.3 5.0 13.0 0.0 0.0 126B 25.2 6.0 10.0 16.0 10.0 26.0 32.6 4.0 11.6 0.3 0.3 X ± s 19.4 18.8 10.0 28.8 36.7 3.7 10.9 0.3 0.1 ± 5.4 ± 4.6 ± 2.3 ± 4.6 ± 3.0 ± 1.0 ± 1.8 ± 0.3 ± 0.2
300G 5.3 1.0 3.3 4.3 39.0 43.3 41.3 3.3 3.7 3.0 0.0 301G 4.3 0.7 1.7 2.4 40.3 42.7 47.3 1.0 3.3 1.3 0.0 304G 7.0 2.3 4.3 6.6 38.7 45.3 37.7 2.0 6.7 1.3 0.0 X ± s 5.5 4.4 39.3 43.8 42.1 2.1 4.6 1.9 0.0 ± 1.7 ± 2.1 ± 0.8 ± 1.4 ± 4.8 ± 1.2 ± 1.9 ± 1.0 ± 0.0
300R 10.3 2.0 3.3 5.3 33.0 38.3 49.0 1.7 0.7 0.0 0.0 301R 8.0 2.0 1.7 3.7 33.0 36.7 49.3 2.0 4.0 0.0 0.0 304R 6.0 1.6 1.0 2.6 34.1 36.7 54.0 2.3 1.0 0.0 0.0 X ± s 8.1 3.9 33.4 37.2 50.8 2.0 1.9 0.0 0.0 ± 2.2 ± 1.4 ± 0.6 ± 0.9 ± 2.8 ± 0.3 ± 1.8 ± 0.0 ± 0.0
(Prob = probable; Twin = twinned; K-felds = potassium feldspar; Biot = biotite; Musc = muscovite; PSM = Pseudomorphs; Opaq = opaques; Zir = zircon). X =sample mean; s = sample standard deviation; 1 See Section 5.9 for definition. 2 Petrographically identified biotite was revealed by XRD analysis to be composed of one or more of the minerals biotite, vermiculite, HIV, or regularly or randomly interstratified mica- vermiculite or mica-HIV (See Sections 9.4 and 9.5). Vermiculite could not be distinguished from HIV in the Na-saturated samples of this size fraction that were analyzed at 25oC.
115 The data in the Table 14 show that the sand fraction of saprolite is composed of quartz, plagioclase feldspar, potassium feldspar, biotite, muscovite, pseudomorphs and a minor amount of opaque minerals. Except for the pseudomorphs, all the other minerals were identified as major constituents in the granitoids at the study site by Kosecki and
Fodor (1997) (see Table 2, page 76). This suggests that the saprolite samples investigated in this study are all derived from granitic parent materials.
The following observations pertain to the data in Table 14:
(1) The number percent of quartz22 is much higher in saprolite developed from granite
with steeply-dipping joints than in the saprolite developed from granite with
horizontally-oriented unloading joints.
(2) The number percentage of (total) plagioclase feldspar is higher in saprolite developed
from granite with steeply-dipping joints than in saprolite developed from granite with
unloading joints.
(3) The number percentage of potassium feldspar is much higher in saprolite developed
from granite with unloading joints than in the saprolite derived from granite with
steeply dipping joints.
(4) The total feldspar number percent is higher in the saprolite developed from granite
with unloading joints than in saprolite developed from granite with steeply-dipping
joints. This is due to the high number percent of K-feldspar in the former than in the
latter.
(5) The number percent of biotite and muscovite is similar in all saprolite samples.
22 Quartz is listed in table 14 as probable quartz. See section 5.9 for definition. 116 (6) The pseudomorph number percent is higher in saprolite developed from
granite with steeply-dipping joints than in saprolite developed from granite with
horizontally-oriented unloading, with the exceptions of samples 126A and 304G. The
A and B population mean (µ) differed from that of the G and R population at α = 0.01
(and at α = 0.001 when sample 123A was excluded).
(7) The number percent of opaque minerals is highest in the red-colored saprolite
samples developed with granite with horizontally-oriented unloading joints.
(8) The number percent of zircon is extremely low in all saprolite samples.
9.2 X-RAY DIFFRACTION
The abundance in the number of primary and secondary mineral phases in the sand- and silt-sized fractions of saprolite lead to an abundance of X-ray diffraction (XRD) peaks in their diffractograms. For example, the X-ray diffractogram of the sand-sized fraction of sample 123A (Appendix III-A, p. 206) contains over 35 peaks in the 2θ range of 0 to 60 degrees. This often lead to an overlap of XRD peaks, making definitive mineral identification difficult sometimes.
The XRD diffractograms for the sand-, silt- and clay-sized fractions of saprolite are presented Appendices III-A, IV-A and V-A, respectively. The XRD peaks for specific minerals identified in the sand-, silt- and clay-sized fractions of saprolite are presented in the remainders of Appendices III, IV, and IV, respectively. Minerals identified using
XRD are shown in Tables 15 –19 and 21 – 22.
117 Interpreting particle-size data (Table 3, p. 89) in conjunction with XRD data (in
Appendices III-A, IV-A, and V-A) indicated that the dominant mineral group in the A, B, and R samples is feldspar, whereas the dominant mineral group in the G samples is kaolinite and / or halloysite.
9.3 DISTRIBUTION OF QUARTZ AND FELDSPAR
The distribution of quartz in saprolite is shown in Table 15. Quartz was petrographically
identified in the sand-sized fraction of every A, B, G and R sample. However, using
XRD, quartz was not detected in several samples. In these samples, it is possible that
either quartz is absent, or is present in levels insufficient to be detectable by XRD.
Quartz does not show a systematic variation with depth or sample fraction in the A and B
samples. However, quartz does show a systematic variation in the G and R samples. In
these samples, quartz was detected in the clay-sized fraction of R samples, but not in that
size fraction of the G samples.
Examination of Table 15 shows that the number percent (in the sand-sized fraction) of
quartz in the A and B samples is about 3 to 4 times higher than in the G and R samples.
If all samples evolved from the weathering of granite with a similar composition, then the
lower number percent of quartz in the G and R samples would indicate greater alteration
of quartz in the G and R samples. Bennett et al. (1988) studied the dissolution of quartz
in dilute aqueous solutions of organic acids at 25oC and standard pressure. They found
that simple organic acids at concentrations encountered in organic rich soils and
weathering zones complex silica in aqueous solution at neutral pH. The formation of a
118 Table 15. Distribution of quartz in saprolite.
Sample Sample Depth sand sand silt clay Number (m) petrographic XRD (number %) 123 A 1 18.5 + -- + 124 A 2 20.0 ------125 A 3 22.5 -- + -- 126 A 4 21.7 + -- +
123 B 1 12.2 + + + 124 B 2 20.4 ------125 B 3 19.8 ------126 B 4 25.2 -- + +
300 G * 5.3 + -- -- 300 R * 10.3 -- -- + 301 G * 4.3 ------301 R * 8.0 -- -- + 304 G * 7.0 -- + -- 304 R * 6.0 -- + +
* Specific sample depth is not known. Probable depth ranged from the surface to 4m as these samples were collected after exploding regolith with dynamite. + definitively identified -- not detected ? identification not definitive
silica-organic acid complex lowered the activity of free monomeric silica in solution, allowing continued dissolution of quartz until equilibrium is reestablished. Using the batch dissolution method, they found after 1750 hours at pH 7 that the concentration of dissolved silica in citrate solution was 167 µmole/Kg compared to 50 µmole/Kg in water. The G and R samples were collected from saprolite developed from massive granite with horizontally-oriented unloading joints. Roots – fresh and decayed – were commonly observed in this saprolite, also oriented parallel to these joints. It is plausible
119 that organic acids exuded from roots concentrated within the weathered zones about the unloading joints enhanced the dissolution of quartz and provided a component of the Si for the synthesis of the kaolinite and or halloysite which is the dominant mineral group in the G samples.
The distribution of feldspar in saprolite is shown in Table 16. Using XRD, plagioclase feldspar and K-feldspar were detected in one or more size fractions in every A, B, G and
R sample. Plagioclase feldspar and K-feldspar were detected in the clay-sized fraction of
R samples but not in that size fraction in the G samples. This suggests that the G samples formed in an environment characterized by intense chemical alteration in contrast to that in which the A, B, and R samples formed.
When all three size fractions are considered, plagioclase feldspar and potassium-feldspar as separate phases were more commonly detected by XRD than quartz. Feldspars were detected in samples in which quartz was not detected by XRD. This variability is probably reflective of the variation of the quartz content in the parent rock, as quartz is very resistant to chemical weathering in the pH range below 9 (e.g., McBride, 1994, p.
219). Particle-size data in conjunction with XRD data indicated that feldspars are the predominant mineral group in the A, B and R samples.
Examination of Table 16 also shows that the number percent (in the sand-sized fraction) of plagioclase feldspar in the G and R samples is about three times less than in the A and
B samples whereas the number percent of potassium-feldspar in the G and R samples is
120 about three times higher than in the A and B samples. If all samples evolved from the weathering of granite with a similar composition, then the observed distribution of feldspars indicates that potassium-feldspar is markedly more stable than plagioclase feldspar in the G and R samples. This suggests that plagioclase feldspar provided a major portion of the Si and Al required for synthesis of the high content of kaolinite and or halloysite, which is the predominant mineral in the G samples.
Table 16. Distribution of feldspar in saprolite.
Plagioclase feldspar Potassium-feldspar Sample Sample (Low Albite) (Orthoclase and Microcline) number Depth (m) sand sand silt clay sand sand silt clay
petrographic XRD petrographic XRD (number %) (number %) 123 A 1 6.0 + + -- 8.3 + + -- 124 A 2 11.8 -- -- + 11.5 + + + 125 A 3 16.0 + + + 12.4 + -- -- 126 A 4 14.9 + + + 15.5 + + +
123 B 1 25.7 + + + 8.9 + + + 124 B 2 17.1 + + + 13.2 + + + 125 B 3 16.5 -- + + 7.9 + -- + 126 B 4 16.0 + + + 10.0 + -- +
300 G * 4.3 + + -- 39.0 + + -- 300 R * 5.3 -- + + 33.0 + + + 301 G * 2.4 + + -- 40.3 + + -- 301 R * 3.7 + + + 33.0 + + + 304 G * 6.6 + + -- 38.7 + + -- 304 R * 2.6 + + + 34.1 + + +
* Specific sample depth is not known. Probable depth ranged from the surface to 4 m as these samples were collected after exploding the regolith with dynamite. + definitively identified -- not detected ? identification not definitive
121 The above observations can be explained based on experimental observations on feldspar
dissolution. Blum and Stillings (1995) compiled feldspar dissolution data as a function of
pH from various studies. Their compilations (their Figures 4 and 5) show that the
dissolution rates of both albite and K-feldspar are similar at pH 6, having log values of
about –16.5 (mol/cm2/s-1). However, experimental data suggest that feldspar dissolution
rate is influenced by the solution saturation state. Burch et al. (1993) studied the free
energy dependence of albite dissolution kinetics at 80oC, pH 8.8. They found that far
from equilibrium, the dissolution rate attained a constant maximum value independent of
23 -1 -1 ∆Gr for undersaturations ≤ -9 kcal mol . Between –6 and –9 kcal mol , the dissolution
-1 rate increased sharply with decreasing ∆Gr. Between –0.4 and –6 kcal mol the
dissolution rate increased with decreasing ∆Gr but to a much lesser extent. Near
-1 equilibrium, -0.9 kcal mol ≤ ∆Gr ≤ 0, the dependence of dissolution rate on solution
saturation state was approximately linear. Their results suggest that weathering solution
within the G and R saprolite samples may be closer to saturation (and closer to
equilibrium) with respect to K-feldspar and far from saturation with respect to plagioclase
feldspar. In contrast, application of their results suggests that the weathering solution
within the A and B saprolite samples is far from equilibrium with respect to both the plagioclase and K-feldspar. Taylor et al. (2000) also made similar observations with
labradorite24. They investigated the dependence of labradorite dissolution at 25oC at pH
3.08 to 3.20. They found that at conditions far from equilibrium with the labradorite, the
log of the overall labradorite dissolution reaction rate was –10.6±0.1 (mol mineral/m2/s).
23 Free energy change of the reaction. 24 A plagioclase feldspar of composition An50 – An70 (Phillips and Griffen, 1981, p. 337). 122 As the saturation state of the solution increased from –16 to –4.5 kcal/mol, the labradorite
dissolution rate decreased by a factor of ~ 4.5.
Nesbitt et al. (1997) also followed a similar line of reasoning when they conceptualized
the simulated weathering of a granite dominated by plagioclase, K-feldspar and quartz.
They stated that both thermodynamic and kinetic stability are responsible for the
retention of quartz and K-feldspar in weathering profiles. They stated that when the
solution is saturated with respect to quartz by the dissolution of plagioclase and K- feldspar, quartz no longer dissolves. Potassium feldspar saturation generally precedes
plagioclase saturation, and following K-feldspar saturation, only plagioclase dissolves.
They further stated that depending upon the reaction period, quartz saturation may not
even be achieved (short reaction period), whereas for others plagioclase saturation may
be approached (prolonged reaction period). The soil porewater chemistry is closer to saturation with respect to potassium feldspar than albite (Blum and Stillings, 1995, p.
306).
The inferred unsaturation with respect to both plagioclase- and K-feldspar in the A and B
samples indicates a short residence time of weathering fluids within the A and B samples,
which is compatible with the steeply-oriented joints found in that saprolite. In contrast,
the inferred saturation with respect to K-feldspar in the G and R samples indicates a
longer residence time of weathering fluids in the G and R samples, which is compatible
with the horizontally-oriented unloading joints found in that saprolite. White et al.
(2001) also attributed the preservation of K-feldspar in the bedrock relative to the
123 extensive weathering of plagioclase in the low –permeability Panola granitic regolith in the Georgia Piedmont Province to the saturation state of the groundwater.
The apparent instability of plagioclase feldspar in the G and R samples can also be
attributed to the presence of organic acids exuded by roots concentrated within the
unloading joints. The rates of plagioclase feldspar dissolution in solutions containing
organic acids are up to ten times greater than the rates determined in solutions containing inorganic acids at the same acidity (Welch and Ullman, 1993). Welch and Ullman found that the polyfunctional acids (oxalate, citrate, succinate pyruvate, and 2-ketoglutarate) to be the most effective at promoting dissolution. The effect of these organic acids on the dissolution of potassium feldspar is however not known.
9.4 DISTRIBUTION OF NON-INTERSTRATIFIED 2:1 PHYLLOSILICATES
The distribution of non-interstratified 2:1 phyllosilicates in saprolite is shown in Table
17. The petrographically determined mica content is very likely an exaggeration due to
the flaking of mica grains during sample preparation. Mica was detected using XRD
more frequently in the A and B samples than in the G and R samples. Muscovite and/or
biotite was detected using XRD in one or more size fractions in all samples except 300G,
304G and 301R. Mica was not detected in the silt-sized fraction in the G and R samples, and was detected in a few samples in the clay-sized fraction.
124 Table 17. Distribution of non-interstratified 2:1 phyllosilicates in saprolite.
Muscovite & or Biotite1 Vc & or HIV Vc HIV Sample Sample number Depth sand sand silt clay sand silt clay (m) petrographic XRD XRD (number %) 123 A 1 48.1 + ------+ + 124 A 2 43.9 -- + + + ------125 A 3 36.9 -- + + ------126 A 4 42.5 + -- + + ------
123 B 1 42.5 + -- + ------124 B 2 40.1 + + + ------125 B 3 42.3 -- + + + ------126 B 4 36.6 + + + ------
300 G * 44.6 ------+ -- + 300 R * 50.7 + -- + ------+ 301 G * 48.3 -- -- + ------+ 301 R * 51.3 ------+ -- + 304 G * 39.7 ------? ? + 304 R * 56.3 + -- + ------+
Vc = vermiculite; HIV = hydroxy-interlayered vermiculite
* Specific sample depth is not known. Probable depth ranged from the surface to 4 m as these samples were collected after exploding regolith with dynamite.
+ definitively identified -- not detected ? identification not definitive
1 Petrographically identified number percent of biotite is revealed by XRD analysis to be composed of one or more of the minerals biotite, vermiculite or HIV, and regularly or randomly interstratified mica-vermiculite or mica-HIV. Vermiculite could not be distinguished from HIV in the Na-saturated samples of this size fraction that were analyzed at 25oC. Number percent is elevated by exfoliation of mica flakes during sample preparation.
Vermiculite and hydroxy-interlayered vermiculite (HIV) cannot be determined petrographically. These minerals are usually counted as biotite when examined by
125 petrographic microscopy. The identification of vermiculite and HIV must therefore rely
on XRD. Vermiculite cannot be distinguished from HIV using XRD in the Na-saturated specimens of the sand- and silt-sized fractions.
Vermiculite and/or HIV did not show any systematic variation with depth in the A and B samples. Vermiculite and/or HIV was rare in the sand-sized fraction of the A and B samples, and was not detected in the silt-sized fraction in these samples. Except for sample 123A, vermiculite and HIV were very rare in the clay-sized fraction of the A and
B samples. HIV and/or vermiculite were absent in the sand-sized fraction of all G and R
samples. However, HIV was found in the clay-sized fraction of all G and R samples.
9.5 DISTRIBUTION OF INTERSTRATIFIED 2:1 PHYLLOSILICATES
The distribution of interstratified 2:1 phyllosilicates is shown in Table 18. Regularly
interstratified 2:1 phyllosilicates (vermiculite-hydrobiotite, see also Appendices III-C and
IV-C) were found in one or more size fractions in all samples except in 126B and 301G.
Randomly interstratified 2:1 phyllosilicates were found in one or more size fractions in
all samples except 125A. In the Na-saturated fractions, XRD peaks (nm) attributable to
random interstratification ranged from 1.111 to 1.186 in the sand-sized fractions (see
Appendix III-C) and from 1.071 to 1.170 in the silt-sized fractions (see Appendix IV-C).
These peaks suggest the random interstratification of mica with vermiculite and or with
hydroxy interlayered vermiculite.
126 Table 18. Distribution of interstratified 2:1 phyllosilicates in saprolite.
Regularly interstratified1 Randomly interstratified Sample Sample 2:1 phyllosilicates 2:1 phyllosilicates number Depth Mica - Vc Mica -HIV (m) sand silt clay sand silt clay 123 A 1 -- -- + + + -- + 124 A 2 + -- ? -- + -- + 125 A 3 + ------? 126 A 4 + -- + + + -- +
123 B 1 -- -- + -- + -- + 124 B 2 + -- + ------+ 125 B 3 + -- + ------+ 126 B 4 ------+
300 G * + -- + + -- + -- 300 R * + -- + -- + -- + 301 G * -- -- ? + + -- + 301 R * -- + ? -- + -- + 304 G * + ? + + + -- + 304 R * -- + + + + -- +
Vc = vermiculite; HIV = Hydroxy-interlayered vermiculite;
* Specific sample depth is not known. Probable depth ranged from the surface to 4 m as these samples were collected after exploding regolith with dynamite.
+ definitively identified -- not detected ? identification not definitive
1 Identification was based on d-spacings attributable to vermiculite-hydrobiotite peaks at 0.450(6) nm and 0.340(4)nm listed in JCPDS card 13-465.
In the clay-sized fractions, it was possible to distinguish between randomly-interstratified mica-vermiculite and mica-HIV due to the various sample treatments. In Mg-saturated clay-sized fractions, the most frequently detected XRD peak attributable to randomly interstratified 2:1 phyllosilicates was at 1.170 nm, and this peak was detected in 5
127 specimens. In this size fraction, randomly-interstratified mica-HIV was much more
commonly detected than randomly-interstratified mica-vermiculite. The former species
was detected in 12 of 16 samples whereas the latter was detected in only 1 of 16 samples.
The XRD peaks attributable to randomly-interstratified mica-HIV showed a progressive
decrease of the peaks near 1.4 nm that was found in Mg saturated specimens when K-
saturated and progressively heated (see Appendix V-B).
9.6 DISTRIBUTION OF HALLOYSITE AND KAOLINITE
The distribution of halloysite and kaolinite in the saprolite is shown in Table 19.
Halloysite was of very restricted occurrence in the sand-sized fraction and was detected
in only 1 (sample 123A) of the 14 samples that were analyzed. Halloysite was detected
more frequently in the silt-sized fraction and was found in 5 of 14 samples analyzed.
Kaolinite was of more widespread occurrence than halloysite in the sand- and silt-sized
fraction of all samples, and was detected more often in the silt-sized fraction (in 10 of 14
samples) than in the sand-sized fraction (in 5 of 10 samples). Halloysite and/or kaolinite
was detected in the clay-sized fraction of every sample and was the predominant mineral
in this size fraction in every sample. Particle-size data taken in conjunction with the
XRD data indicated that kaolinite and/or halloysite is the main mineral constituent in the
G samples.
128 Title 19. Distribution of halloysite and kaolinite in saprolite based on X-ray diffraction..
Sample Sample Halloysite Kaolinite Halloysite and / number Depth or Kaolinite1 (m) sand silt sand silt clay
123 A 1 + -- + + + 124 A 2 ------+ + 125 A 3 ------+ + 126 A 4 -- + + ? +
123 B 1 -- + + -- + 124 B 2 -- + + + + 125 B 3 -- -- + + + 126 B 4 -- + -- + +
300 G * ------+ + 300 R * -- -- + + + 301 G * ------+ 301 R * -- + -- -- + 304 G * -- -- + + + 304 R * ------+ +
* Specific sample depth is not known. Probable depth ranged from the surface to 4 m as these samples were collected after exploding regolith with dynamite. + definitively identified -- not detected ? identification not definitive
1 Peaks attributable to the (001) reflection from the [001] plane of halloysite and kaolinite could not be confidently resolved in samples of the clay-sized fraction; see text for details.
Due to wide variations in the spacing of (001) reflection from the [001] plane (see
APPENDIX VI, page 346), it was not possible to distinguish halloysite from kaolinite based on XRD in the clay-sized fraction of all samples. Peaks attributable to this reflection were rarely detected in the randomly-oriented Na-saturated specimens of the sand-sized fraction. Similarly treated specimens of the silt-sized fraction showed XRD peaks in the interval 0.699 to 0.752 nm. In K-saturated, oriented specimens of the clay- 129 sized fraction, peaks ranged from 0.725 to 0.786 nm in air-dried samples and from 0.699
to 0.713 nm in samples heated to 350oC. In all specimens except two, the spacings of K-
saturated air-dried samples were greater than in the K-350oC samples. However, in these two specimens, the spacings were similar (i.e., the peaks ranged from 0.706 nm to 0.713 nm). This suggests that the mineral component randomly interstratified with kaolinite is not fully collapsed, making HIV a potential candidate. In general, the spacing in the Mg- saturated specimens was greater than in the Mg-glycerolated specimens (except in 2 samples), which suggests that the 2:1 mineral present in the interstratified component has no swelling properties, thus ruling out the smectite family. Further studies are required to fully identify the mineral component interstratified with the kaolinite and or halloysite.
Several researchers have reported the occurrence of clay minerals randomly interstratified with kaolinite. Corti et al. (1998) reported randomly-interstratified kaolinite-smectite from Galicia (NW Spain). Their Na-saturated clay samples showed prominent asymmetric peaks at 0.750-0.755 nm and 0.718 nm. Their air-dried K-saturated clay heated to 300oC showed a wide asymmetric peak at 0.740 nm and a minor one at 0.714 nm. Magnesium-saturated clay displayed a peak at 0.713 nm, while the peaks at 0.750-
0.755 disappeared. Kaolinite/smectite minerals were reported from Java (Nurcholis and
Tokashiki, 1998) and the Philippines (Aleta et al., 1999). Egashira (1992) reported interstratified kaolinite/vermiculite from Japan. Egashira based the identification on the detection of a 0.764 nm peak apart from a peak at 0.710 nm in K-saturated and air-dry treatments that shifted to 0.739 nm upon heating at 300oC.
130 The abundance of kaolinite and/or halloysite in the G samples indicates a long residence
time of weathering fluids within that saprolite. Aluminum required for the synthesis of
kaolinite [Al2Si2O5(OH)4] and halloysite [Al2Si2O5(OH)4.2H2O] in the granitic saprolite
was likely derived from weathering plagioclase (see Section 9.3). According to Kittrick
(1969), four factors that appear to be important in determining solution H4SiO4 levels are
(1) the rate of dissolution of unstable silicates, (2) the rate of precipitation of stable silicates, (3) the rate of movement of H4SiO4-bearing solutions out of the system, and (4)
the rate of plant uptake. If Al and Si are in solution together, they co-precipitate as
aluminosilicates in the pH range 4 to 11 lowering both their solubilities relative to either
one alone (McBride, 1994, p. 221). Siffert (1962) studied the solubility of quartz in
distilled water at room temperature (Table 20). Siffert’s data shows that for quartz
particles with diameters < 5 µm, the concentration of silica increases with residence time.
In addition, experiments of Taylor et al. (2000) conducted at 25oC and pH ranging from
3.08±0.05 to 3.20±0.05 with labrodorite showed that Si concentrations increased with
mineral-water contact times, and their Figure 4 shows that a Si concentration of
approximately 45 µm was achieved at a mineral-water contact times of about 15 X 10-4 years.
131 Table 20. Solubility of quartz in distilled water at room temperature, expressed in µg/ml. Extracted from Siffert, 1962 (page 22). Φ = particle diameter.
Quartz Time 1.5 g / 400 ml distilled water (days) 250 µm – Φ – 500 µm Φ < 5 µm 1 0 0.5 7 0 0.5 13 0 1 20 0 2.87 27 0 2.50 34 0 6.00 43 0 7.00 200 ε 7.00
9.7 DISTRIBUTION OF HYDROXIDES AND OXYHYDROXIDES OF
ALUMINUM
The distribution of hydroxides and oxyhydroxides of aluminum determined using XRD is shown in Table 21. The following observations pertain to the data in Table 21:
(1) The most frequently detected mineral in the sand fraction was nordstrandite, followed
in decreasing order by pseudoboehmite25, bayerite, diaspore, gibbsite and boehmite,
the latter two occurring an equal number of times.
(2) In the silt fraction, the most frequently detected phase was nordstrandite, followed
by diaspore, and pseudoboehmite. Gibbsite was tentatively identified in the silt-sized
fraction of 2 samples, and bayerite was tentatively identified in one sample. Boehmite
was not detected in the silt-sized fraction.
25 Pseudoboehmite is boehmite of very fine crystal size that yields XRD peaks in the range of 0.64 to 0.69 nm (Hsu, 1989). 132 Table 21. Distribution of hydroxides and oxyhydroxides of aluminum in saprolite based on XRD.
Sample Sample Aluminum hydroxides Aluminum oxyhydroxides number Depth (m) sand silt clay sand silt clay
123 A 1 + + + + + -- 124 A 2 + -- + + + + 125 A 3 + -- + + + -- 126 A 4 + -- + + -- +
123 B 1 + + + + -- + 124 B 2 + + + ? + + 125 B 3 + + + + + + 126B 4 + + + + -- +
300 G * + + -- + -- -- 300 R * + -- + ------301 G * + + + ? + -- 301 R * + + + -- + -- 304 G * + + + ? -- -- 304 R * + + + + -- +
* Specific sample depth is not known. Probable depth ranged from the surface to 4m as these samples were collected after exploding regolith with dynamite. + definitively identified -- not detected ? identification not definitive
(3) In the clay-sized fraction, the most frequently detected phase was nordstrandite,
followed in decreasing order by diaspore and gibbsite. Pseudoboehmite and
boehmite were not detected in the clay-sized fraction. The analysis of the clay-sized
specimens in the restricted 2θ range of 0 to 30 degrees did not allow for the detection
of the 0.222 nm (most intense) peak necessary for the identification of bayerite.
133 (4) When all size subfractions of all 14 samples are considered (that is, out of a total of
42), the most frequently detected phase by far was nordstrandite (24 occurrences),
followed by diaspore (15) and pseudoboehmite (8), gibbsite (6), bayerite (5), and
boehmite (1).
(5) Diaspore is of very rare occurrence in saprolite developed from granite with
horizontally-oriented unloading joints (G and R samples). In this type of sample, it
was detected in only one sample. Diaspore was much more common in the A and B
samples which have developed from granite with steeply-dipping joints and was
detected in the sand-sized fractions of 3 samples, silt-sized fractions of 5 samples and
clay-sized fractions of 6 samples.
Several difficulties are encountered in the detection of aluminum hydroxides and
aluminum oxyhydroxides using XRD. Gibbsite will not be detected by XRD if its
content is 50 g kg-1 or less (Jackson, 1969). The identification of small amounts of diaspore, with its major diffraction lines among those of common soil components would be even more difficult than the identification of gibbsite (Taylor, 1987, p. 169). The detection of pseudoboehmite has also been reported to be difficult. Violante and Huang
(1994) found it difficult to detect pseudoboehmite by XRD in a randomly oriented sample containing 40% of pseudoboehmite when the sample also contained kaolinite and montmorillonite. In oriented samples containing kaolinite and montmorillonite, they found that pseudoboehmite was detectable only when present in amounts >30%, at 1000 -
400 counts per second. In addition, they found that the identification of pseudoboehmite
by differential thermal analysis, infrared absorption or transmission electron microscopy
134 failed even in samples containing 50% pseudoboehmite in the presence of kaolinite or
montmorillonite.
Violante and Jackson (1979) hypothesized that the presence in soils of clay and organic
matter with its carboxylic and amine groups inhibit the crystallization of bayerite by
favoring the formation of gibbsite and/or nordstrandite. Barnhisel and Rich (1965)
investigated the formation of crystalline Al(OH)3 polymorphs from Al-interlayers and/or
hydroxy-Al polymers and found that gibbsite crystallized better in acid environments,
nordstrandite in slightly acid to neutral, and bayerite in basic environments. They also
found that nordstrandite also crystallized under acid conditions in systems having
relatively low amounts of Na+ and Cl- ions. Based on a review of the literature, Dani et
al. (2001) stated that high alkali concentrations and neutral to basic solutions seem to be
the most important factors that promote nordstrandite formation in preference to other
aluminum hydroxides. In the present study, the distribution of aluminum hydroxides and
aluminum oxyhydroxides did not appear to vary with pH or exchangeable base content.
Gibbsite, bayerite, nordstrandite and doyleite are four polymorphs of aluminum
hydroxide that have been described in natural environments (Dani et al., 2001). Gibbsite
is the most common and the others are rare (Schoen and Roberson, 1970; Dani et al.,
2001). Gibbsite has been reported as a common product in the very early stages of
isovolumetric weathering (Calvert et al., 1980; Fritz, 1988). Gibbsite is the most
common pedogenic form of Al(OH)3, is often the principal mineral in bauxite deposits and commonly occurs in laterites (Taylor, 1987, p. 163). Gibbsite has been reported as a
135 product of feldspar alteration in granitic saprolite or weathered granite by several authors
(e.g., Eswaran and Bin, 1978b; Anand et al., 1985; Green and Eden, 1971; Hall et al.,
1989; Melfi et al., 1983; Wilke and Schwertmann, 1977; Verheye and Stoops, 1975).
Nordstrandite has been reported from Miocene limestone on Guam (Hathaway and
Schlanger, 1962), in a red soil found at the edge of a sink-hole developed from limestone in Borneo (Wall et al., 1962), in thin fissure fillings in dolomitic marlstones and oil shale of the Green River Formation in northwestern Colorado (Milton, 1975), and along fractures and at contacts between inner spheroids and internal fresh rock of a feldspathic alkaline country rock rich in nepheline, sodalite, nosean, analcime and natrolite (Dani et al., 2001). Milton (1975) reported the first discovery of nordstrandite in the United
States. Dani et al. (2001) also cited the reported geological occurrences of nordstrandite.
The occurrence of nordstrandite in the saprolite samples used in this study is noteworthy as it has not been previously reported from granitic saprolite. Bayerite has not been reported in soils (Taylor, 1987, p. 165). Bentor et al. (1963) reported the occurrence of bayerite in Hatrurim (Israel) in veins associated with calcite and gypsum.
Boehmite and diaspore are known to exist in many bauxites (Hsu, 1989, p. 362). Young bauxites are gibbsitic, and with age, gibbsite gives way to boehmite and diaspore (Evans,
1986, p. 179). Boehmite is more common in nature than bayerite and nordstrandite, but much less common than gibbsite, especially in soils (Taylor, 1987, p. 167).
The presence of gibbsite, boehmite, diaspore, and corundum in lateritic soils and near- surface bauxites suggests the absence of thermodynamic equilibrium (Peryea and
136 Kittrick, 1988). Assuming solid phase and activities of unity, Peryea and Kittrick (1988) investigated the stability of corundum, gibbsite, boehmite, and diaspore in aqueous solutions at 298 K and one atmosphere pressure. They found that the relative thermodynamic stabilities were corundum < gibbsite < boehmite < diaspore. The occurrence of gibbsite, bayerite, nordstrandite, boehmite, pseudoboehmite and diaspore in the saprolite samples investigated in this study may indicate the existence of diverse microenvironments with respect to these aluminum-bearing minerals or the lack of thermodynamic equilibrium. Essene et al. (1994) stated that geological systems at or near the earth’s surface usually do not approach either stable or metastable equilibrium, and therefore equilibrium models can have only limited applicability. Kittrick (1969) stated that given that gibbsite is less stable than boehmite or diaspore and yet is much more common in soils, it appears that on a geological times scale gibbsite is a metastable fast-former that alters to more stable forms relatively slowly.
9.8 DISTRIBUTION OF HYDROXY APATITE, MONAZITE, ALLANITE AND
ZIRCON
In fresh granite at the study site Kosecki & Fodor (1997) detected several primary minerals that occur in low concentrations (Table 2, page 76). These include hydroxy apatite (minor), monazite (accessory), zircon (accessory) and allanite (accessory).
Apatite accounts for 950 g kg-1 or more of the total P in igneous rocks (Lindsay et al.,
1989, p. 1103) and is therefore pertinent to the natural fertility of saprolite and soil developed from granite. Monazite also contains phosphorus in addition to rare-earth elements. Hydroxy apatite, monazite and zircon resist weathering. Of these,
137 zircon is exceedingly resistant to weathering and solution and individual grains appear to survive through successive cycles of sedimentation (Williams et al., 1982, p. 337). In quantitative studies of pedogenesis Zr has been used as a strain marker (e.g., Brimhall et al., 1991) and as an index element in stable index calculations (e.g., Busacca and Singer,
1989). Allanite contains calcium and weathers rather easily to a mixture of limonite, silica and alumina (Phillips and Griffen, 1981).
Hydroxy apatite, monazite and allanite were not detected petrographically in the sand- sized fractions. Zircon was detected petrographically in the sand-sized fraction in only
one sample. Using XRD, hydroxy apatite and monazite were detected in several samples
and in all three size fractions (Table 22). These two minerals were more common in the
sand- and silt-sized fractions than in the clay-sized fractions, perhaps reflecting their
greater resistance to weathering. In the Panola adamellite26 located 25 km southeast of
Atlanta, Georgia, Grant (1975) found that all interstitial apatite had dissolved by the time
the bulk density (g cm-3) had dropped to 2.2, mica-included apatite persisted till bulk
density reached about 1.5, and quartz-included apatite persisted into the A-
horizon and alluvium. In the present study, the location of apatite crystals
(i.e., interstitial, mica-included, quartz-included) is not known. Allanite and zircon27
could not be detected in the clay-sized fractions owing to a lack of suitable XRD peaks in
26 Synonymous with quartz monzonite, with modal quartz between 5 % and 20 % of the felsic component (Williams et al., 1982, p. 160). 27 The zircon 0.330(x) nm peak is extremely close to those of orthoclase 0.331(x) nm, gibbsite 0.331(2) nm, intermediate microcline 0.329(x,5) nm, maximum microcline 0.329(5) nm, orthoclase 0.329(6) nm and monazite 0.329(4) nm. The zircon peak at 0.252(5) nm is very close to the vermiculite peak at 0.253(5), and the zircon peak at 0.171(4) nm overlaps that of diaspore 0.171(2) nm. The zircon peak at 0.207(2) nm is very close to the peak of diaspore at 0.208(5) nm.
138 the granitic saprolite caused by the overlapping of XRD peaks from different minerals and also due to the analysis over a restricted range (0 – 30 degrees) of 2θ.
Table 22. Distribution of hydroxy apatite and monazite in saprolite.
Hydroxy apatite Monazite Sample Sample number Depth sand sand silt clay sand sand silt clay (m) petrographic XRD petrographic XRD (number %) (number %) 123 A 1 0.0 + + -- 0.0 -- + -- 124 A 2 0.0 ------0.0 + -- -- 125 A 3 0.0 ------0.0 + -- -- 126 A 4 0.0 + -- -- 0.0 ? -- +
123 B 1 0.0 -- -- + 0.0 ? -- -- 124 B 2 0.0 + + -- 0.0 ------125 B 3 0.0 ------0.0 + + -- 126 B 4 0.0 -- -- + 0.0 ? + --
300 G * 0.0 + -- -- 0.0 ------300 R * 0.0 ------0.0 -- + -- 301 G * 0.0 ------0.0 + + -- 301 R * 0.0 -- + -- 0.0 + -- -- 304 G * 0.0 ------0.0 ? + -- 304 R * 0.0 + -- -- 0.0 ? + --
* Specific sample depth is not known. Probable depth ranges from the surface to 4m as these samples were collected after exploding regolith with dynamite. + definitively identified -- not detected ? identification not definitive
139 9.9 PSEUDOMORPHS AND THEIR CONTRIBUTION TO THE CATION
EXCHANGE CAPACITY OF SAPROLITE
The presence of pseudomorphs28 in the sand-sized fractions of saprolite offers an explanation for the relatively high values of cation exchange capacity (CEC) observed in the sandy-textured saprolite samples (Table 23). Pseudomorphs may still retain the shape of the original primary mineral but appear altered beyond recognition when observed by a petrographic microscope. Depending on mineralogical composition, pseudomorphs can be expected to possess permanent or variable charge and high specific surface areas
(SSA).
Secondary minerals identified in the sand-sized fractions by XRD include vermiculite- hydrobiotite, mica randomly interstratified with vermiculite and or with HIV, vermiculite and / or HIV, halloysite, kaolinite, gibbsite, bayerite, nordstrandite, pseudoboehmite, boehmite and diaspore. Although anion exchange capacity (AEC) was not measured in this study, given that aluminum hydroxides generates AEC as a result of the adsorption of hydroxyl ions (McBride, 1994, p. 96), the saprolite might possess an anion exchange capacity (AEC) as well. In particular, phosphate – an anion of great importance to plant growth - is adsorped on the surface of Al(OH)3 (Parfitt, 1978).
28 The mean (µ ) of the A and B population differed from that of the G and R at α=0.01, and at α=0.001 when sample 123A was excluded. 140 Table 23. Cation Exchange Capacity (CEC), particle-size distribution, and abundance of pseudomorphs in saprolite.
Sample Depth CEC Mass percent in CEC Pseudo (m) cmol+ kg -1 fine-earth1 fraction cmol+ -morph (pH 7.0) kg -1 number sand silt clay clay** % 2
123A 1 6.0 79.1 11.2 9.7 61.6 19.1 124A 2 4.5 86.7 10.8 2.4 187.7 12.4 125A 3 3.5 87.0 11.7 1.3 267.9 11.4 126A 4 4.5 84.8 14.1 1.1 409.2 5.0
123B 1 4.1 90.2 9.3 0.5 819.5 9.9 124B 2 2.9 88.9 9.7 1.4 205.9 8.9 125B 3 2.9 90.5 8.2 1.3 221.0 13.0 126B 4 3.3 87.5 11.2 1.3 252.8 11.6
300G * 12.8 10.5 0.3 89.2 14.3 3.7 300R * 5.3 79.6 5.4 15.0 35.3 0.7 301G * 11.7 15.4 0.8 83.8 14.0 3.3 301R * 5.3 78.7 4.4 16.8 31.7 4.0 304G * 12.5 7.7 0.1 92.2 13.6 6.7 304R * 5.9 71.3 5.0 23.6 25.2 1.0
1 < 2 mm-sized fraction 2 Based on a count of 300 grains by the line method. * samples were collected after exploding regolith with dynamite. Probable sample depths ranged from 0 to 4 m. ** Apparent cation exchange capacity. Equivalent to meq per 100g clay.
It was frequently observed during the petrographic examination of the whole sand-sized fractions of saprolite that plagioclase feldspars showed no internal alteration. The grain boundaries were usually bay-shaped at the juncture between selected twinned zones. The
K-feldspar grains, on the other hand, showed no noticeable undulation of grain boundaries, but frequently showed internal alteration along cleavage planes. This suggests that the pseudomorphs may have formed from K-feldspar and not from plagioclase feldspar. The correlation coefficient between the number percents of pseudomorphs and K-feldspar in the A, B, G and R samples is - 0.998, - 0.775, - 0.723
141 and - 0.427, respectively. When sample 123B from 1 m depth is excluded, the correlation coefficient for the B samples also is - 0.998. The correlation values suggest that pseudomorphs may have formed from the alteration of K-feldspar in the A and B saprolite samples, which have formed from granite with steeply-dipping joints.
142 CHAPTER 10
A CLASSIFICATION FRAMEWORK FOR
ISOVOLUMETRICALLY WEATHERED REGOLITH
A classification of isovolumetrically weathered regolith could aid communication and technology transfer, comparison of regolith from different weathering environments, help determine suitability of saprolite for specific engineering, agricultural, and environmental uses, and would reflect our understanding of the genesis of this material as well. It is the author’s opinion that a successful classification must not only provide useful information about what is being classified, but also be easy to use, thus encouraging its adoption by a wide group of users. Although not an objective of the study, the author has proposed a conceptual classification framework for saprolite to promote further study. The aim of the proposed classification framework is to highlight mass alteration and its partitioning between the saprolite and its environment during saprolite genesis.
The choices of parameters for the classification of isovolumetrically weathered regolith are many and depend on the intended use of the classification. Quantities defined in this study such as mass altered per unit volume (mA/VT), altered mass retained per unit volume (mAR/VT), and altered mass lost per unit volume (mAL/VT), have applications in the classification of isovolumetrically weathered regolith. A classification of saprolite based on these three parameters themselves or quantities derived from these parameters would provide users of saprolite with direct information contained in the parameters and also enable the inference of other properties of saprolite.
143 The main contributors to the compressive and shear strength of regolith are likely the
unaltered mass (primary minerals), with minor contributions made by altered mass that is
retained within the weathering rock. The structural integrity of a rock can be expected to
show a strong positive correlation with the mass of primary minerals remaining within a
o unit volume of isovolumetrically weathered regolith (m1 R/VT), and show a strong
negative correlation with mA/VT. A weaker positive correlation can be expected with
mAR/VT. The strength of the correlations can be expected to depend on the original rock
o fabric. Therefore, there are benefits to the inclusion of mA/VT (or m1 R/VT) and mAR/VT
as parameters in the classification of isovolumetrically weathered regolith.
o The parameters m1 R/VT and mAR/VT provide other information about regolith as well.
The former quantity can potentially provide information on nutrients still available in the rock, albeit in an unexchangeable form. The latter quantity is likely to be correlated with the regolith’s capacity to exchange cations (CEC) and anions (AEC) depending on the secondary mineral phases present.
Bulk density of isovolumetrically weathered regolith (and of nonisovolumetrically weathered regolith) can be separated into the contributions made by primary and secondary minerals as shown by the equation
o ρb = (m1 R / VT) + (mAR / VT) (4)
Equation (4) shows that a given value of bulk density can be associated with different masses of primary and secondary minerals per unit volume of regolith. Therefore, in
144 isovolumetrically weathered regolith, a given value of bulk density can be associated
with different values of mA/VT because the equation
o mA/VT = ρs - m1 R / VT (3)
is valid for isovolumetrically weathered regolith. Bulk density, therefore, is of limited
value as an indicator of the distribution of primary and secondary minerals and of properties associated with them, and can therefore be considered unsuitable as a
classifier.
Given that Si4+ is mobile within weathering environments in comparison to Al3+
(Middleburg et al., 1988), the ratio mAR/mA can be expected to place stoichiometric limits
on the structure of secondary minerals that can be synthesized during the isovolumetric weathering of aluminosilicate rocks. The relative stabilities of aluminum hydroxides/oxyhydroxides, kandites and smectites may parallel increasing values of
4+ 3+ mAR/mA reflecting increasing molar Si /Al in the altered mass retained and may
provide an indication of the mineral composition of the altered mass retained in the saprolite. Thus the inclusion of mAR/VT and mA/VT as classifiers may provide some
indication of the regolith’s secondary mineralogy and the leaching intensity of the
weathering environment as well.
145 10.1 CLASSIFICATION FRAMEWORK PROPOSED FOR
ISOVOLUMETRICALLY WEATHERED REGOLITH
A classification framework proposed for isovolumetrically weathered regolith based on
o mass of primary minerals remaining per unit volume (m1 R/VT), altered mass retained per
unit volume (mAR/VT), and altered mass lost per unit volume (mAL/VT), all expressed as a
percentage of the mass originally present in the unweathered rock (ρs) is shown in Figure
12. Thus the classification framework can be considered to be an expression of the
fundamental equation of mass balance in isovolumetrically weathered regolith,
o ρs = (m1 R/ VT) + (mAR/ VT) + (mAL/ VT) (2)
reexpressed as
o 100 (m1 R/VT) 100 (mAR/VT) 100 (mAL/VT) 100 = [ ______] + [ ______] + [ ______] ρs ρs ρs
Although a rectangular diagram using any two parameters is possible and more adaptable to mathematical representation, the classification framework proposed is a ternary diagram in keeping with the established tradition of classifying earth materials using
ternary diagrams [e.g.: sandstones (McBride, 1963; Folk, 1974); ophiolitic sands
(Garzanti et al., 2002); limestone (Folk, 1959); plutonic igneous rocks (Le Maitre et al.,
1989; Le Bas and Streckeisen, 1991), feldspar (Deer et al., 1962, p. 2); soil textural
classes (Soil Survey Manual, 1993)]. An additional benefit of ternary diagrams is “their
ability to demonstrate subtleties of variation not obvious in the more comprehensive
rectangular diagrams” (Williams et al. 1982, p. 26).
146
o m1 R 100 ______[ ] VT ρs 100
Slightly altered ρb = (3/4) ρs
……………… 66 1 2 3 4
Moderately altered ρb = (1/2) ρs 8 5 6 7
………… 33
Severely ρb = (1/4) ρs altered 9 10 11 12
100 100
mAR 100 100 mAL [ ______] ______[ ______] VT ρs ρs VT
← retentive saprolite → ← leached saprolite →
Figure 12. Classification framework for isovolumetrically weathered regolith. Dotted lines represent lines of equal bulk density.
The classification framework places isovolumetrically weathered regolith into 12 fields, numbered 1 through 12. The fields are based on the extent of chemical alteration of primary minerals that were present in the rock and on how the altered mass is partitioned between the weathering system and its environment. 147 The classification position of a regolith with respect to the vertical line connecting the top
corner of the classification triangle to its base indicates the mass of primary minerals
remaining per unit volume of isovolumetrically weathered regolith as a percent of initial
rock density, with the top of the line representing 100 and the point of intersection with
the bottom horizontal line of the triangle representing 0. Conversely, when measured
from the bottom of the triangle to its top corner, the same line also represents mass
altered per unit volume (mA/ VT) as a percent of original rock density, with the top corner representing 0 and the point of intersection with the base of the triangle representing 100.
Fields 1, 2, 3, and 4 can be considered to represent slightly altered regolith, characterized
o by values of (100/ρs)(m1 R/VT) ranging from 100 to 66 percent. The corresponding
values of mA/VT range from 0 to 33 percent of original mass. Fields 5, 6, 7, and 8 can be
considered to represent moderately altered regolith, characterized by values of
o (100/ρs)(m1 R/VT) ranging from 66 to 33 percent values of mA/VT ranging from 33 to 66
percent of original mass. Fields 9, 10, 11, and 12 can be considered to represent severely
o altered regolith, characterized by values of (100/ρs)(m1 R/VT) ranging from 33 to 0
percent and values of mA/VT ranging from 66 to 100 percent of original mass.
Isovolumetrically weathered regolith differs not only in the amount of mass altered per
unit volume of regolith (mA/VT), but also in how the altered mass is partitioned between an isovolumetrically weathering rock and its environment. The classification framework takes into consideration this important aspect of weathering.
148 Regolith that plots to the left of the vertical line in the classification framework is
characterized by (mAR/VT) > (1/2) (mA/VT) and is termed retentive saprolite.
Regolith that plots to the right of that line is characterized by (mAL/VT) > (1/2) (mA/VT)
and is termed leached saprolite.
The 12 classification fields can be characterized by the amount of mass altered and mobility of the altered mass (Table 25).
Table 24. Saprolite classification fields.
Field 1 slightly altered, highly retained Field 2 slightly altered, moderately retained Field 3 slightly altered, moderately leached Field 4 slightly altered, highly leached Field 5 moderately altered, highly retained Field 6 moderately altered, moderately retained Field 7 moderately altered, moderately leached Field 8 moderately altered, highly leached Field 9 severely altered, highly retained Field 10 severely altered, moderately retained Field 11 severely altered, moderately leached Field 12 severely altered, highly leached
The position of a regolith within the classification framework may provide general information on the expected secondary minerals present in saprolite. For saprolites developed from similar parent materials, the use of the classification framework may highlight systematic changes in mineralogy. For example, it maybe found that in saprolite evolved from granitic materials, gibbsitic saprolite may plot exclusively within
149 the leached saprolite field, smectitic saprolites may plot exclusively within the retained
saprolite field, and kaolinitic saprolite may plot within contiguous parts of both fields.
Bulk density of the materials to be classified is an essential input in the classification.
However, the bulk density (ρb) of isovolumetrically weathered regolith classified within
the classification framework can easily be visualized from knowledge of its position within the classification triangle. This is because bulk density equals the masses of primary minerals and altered mass contained within a unit volume of regolith and therefore be expressed using the classifiers as
o o ρs 100 (m1 R/VT) 100 (m2 R/VT) ______ρb = { + } (12) 100 [ ρs ] [ ρs ]
The ability to easily visualize the bulk density of the classified regoliths can be
considered an advantage of the proposed classification framework. Bulk density of
saprolite varies systematically with position within the classification framework. Bulk
density progressively decreases from the left border of the triangle towards the right apex,
with lines representing values of equal bulk density being oriented parallel to the left side of the triangle. It is because some of the proposed classification fields encompass
unrealistically low values of bulk density for isovolumetrically weathered regolith that the term classification framework is used, instead of the term classification29.
29 A similar situation occurs in ternary classifications of feldspars (e.g., Deer et al., 1962) due to restricted solid solution between the feldspar endmembers. 150 10.2 COMPARISON OF PROPOSED CLASSIFICATION FRAMEWORK TO
BUOL ’S (1994) SAPROLITE CLASSIFICATION
Buol (1994) proposed a classification of saprolite-regolith materials, defined as materials
with an unconfined compressive strength of less than 100 Mpa that are either not
penetrated by plant roots, except at intervals greater than 100 cm, or occur more than 200
cm below the soil surface. These materials were classified using a four-category
hierarchical system. The classification recognized four taxa in the first or highest
category, namely alluvium, colluvium, petrosediments, and saprolite. Saprolite was
defined as materials that have become less hard because of processes occurring near the
earth’s surface. Hardness and bulk density were used as criteria for the second category
separation of saprolites (and petrosediments). It is the second category separation of
saprolite that can best be compared to the classification framework proposed in this
study.
At the second category, Buol separates saprolites into Arap (hard saprolite), Idap
(saprolite of mid hardness), and Earap (earthy saprolite). Arap is defined as saprolite
with an unconfined compressive strength between 25 and 100 MPa and bulk density greater than 2.3 Mg m-3 that cannot be broken by hand, have no roots except in cracks
which average more than 10 cm apart, and biotite (if present) showing only slight
weathering. Idap is defined as saprolite with an unconfined compressive strength less than 25 MPa and bulk density (moist) greater than 1.8 Mg m-3 such that roots can
penetrate between individual sand grains, feldspars (if present) are opaque, and biotite (if
151 present) is clearly altered by weathering. All other saprolite is defined as Earap (or earthy saprolite).
Buol’s (1994) second category saprolites cannot be completely tied in with the classification fields proposed in this study. Buol’s classification can be considered an absolute classification in that at least some of the criteria used to separate saprolites are based on specific values of unconfined compressive strength and bulk density. The classification framework proposed in the present study can be considered a relative classification, in that the (three) classification parameters used are all expressed as weight percent of mass present in the original (unweathered) rock. Thus Buol’s classification can be considered to be better suited than the classification framework proposed here for the characterization of saprolite for specific engineering uses, whereas the classification framework proposed here can be considered to be better suited for modeling the evolution of rocks with progressive isovolumetric weathering, and hence a better research tool than Buol’s for the study of the isovolumetric weathering process.
Saprolite categories defined by Buol (1994) as Arap, Idap, and Earap do not completely overlap any of the classification fields within the classification framework proposed here.
This is mainly due to the use of bulk density in Buol’s classification. Figure 12 shows that lines of equal bulk density can cut across lines with equal values of mass of
o [(100/ρs) (m1 R/VT)], and thus cut across lines of equal values mA/VT. That is, the classification fields that encompass slightly-, moderately-, and severely altered saprolite are not associated with unique ranges in bulk density values. This is because the present
152 study recognizes that bulk density of isovolumetrically weathered regolith developed
from a rock of a specified density (ρs) is uniquely related to mAL/VT, but not to mA/VT.
This recognition is based on the expressions
o mA/VT = ρs - m1 R / VT (3),
o ρb = (m1 R / VT) + (mAR / VT) (4),
and (mAL / VT) = ρs - ρb (5)
10.3 CLASSIFICATION OF SAPROLITE INVESTIGATED IN THIS STUDY
USING THE PROPOSED CLASSIFICATION FRAMEWORK
The saprolite investigated in this study was plotted on the classification framework
proposed here (Figure 13). The classification positions were determined by computing
o the values of the classifiers [100 (m1 R/VT)/ ρs], [100 (mAR/VT)/ ρs] and [100 (mAL/VT)/ ρs] using particle-size and bulk density data that was presented in Chapter 6. Using averaged data for the A and B saprolite samples, the values of the classifiers were 55.35, 7.94 and
36.71 respectively. This saprolite falls within classification field 8, which is ‘moderately altered, highly leached’. The G and R saprolite was plotted after constructing a hypothetical 1 cm 3 sample using a volumetric proportion30 ( X ± s) of 58.2 ± 0.7 (%) red
layers and 41.8 ± 0.5 (%) gray layers. The classification parameters for the averaged G
and R saprolite were 29.41, 29.47 and 41.12, respectively. This saprolite falls within
classification field 11, which is ‘severely altered, moderately leached’.
30 Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. The volumetric ratio was determined using two samples (clods) from which a total of 9 subsamples were analyzed. 153
o m1 R 100 ______[ ] VT ρs 100
Slightly altered
1 2 3 4 66 …………………………
Moderately 5 6 7 8 altered *
33 …………………
+ Severely 9 10 11 12 altered
100 100 50
mAR 100 100 mAL [ ______] ______[ ______] VT ρs ρs VT
← retentive saprolite → ← leached saprolite →
Figure 13. Classification position of the A and B saprolite (*) and the G and R saprolite (+) within the classification framework proposed for isovolumetrically weathered regolith.
154 CHAPTER 11
VARIATION OF ISOVOLUMETRIC WEATHERING WITH
VARIATION IN JOINT ORIENTATION
Physical, chemical and mineralogical properties of saprolites investigated in this study that were developed from granite with contrasting joint orientations differed markedly.
The population means (µ) of mA/VT, mAR/VT, mAL/mA, mAR/mA and mass percents of
sand-, silt- and clay-sized particles (on a whole-saprolite and fine-earth basis) differed at
α = 0.001. The population means of bulk density and mAL/VT differed at α = 0.01 and
0.05, respectively, pH, CEC and mass percent free iron (Fe2O3) differed at α = 0.001, and
percent base saturation differed at α = 0.05. The presence of quartz, plagioclase feldspar,
K-feldspar, biotite, muscovite, hydroxy apatite and monazite as well as the almost total absence of zircon in the saprolites suggests formation from similar parent materials. The weak compositional banding observed in the slightly weathered rock hosting the horizontally-oriented G and R saprolite samples was nearly vertical, suggesting that the horizontally-oriented color- and textural zonation in that saprolite was most likely related
to the pattern of unloading joints and not to any compositional (and/or textural) banding
in the parent rock. The observed variation in saprolite properties can be explained by the
interaction of the different joint orientations with meteorology. This chapter proposes
mechanisms for the development of saprolite in granite with contrasting joint patterns and
a classification of isovolumetric weathering environments. The reader should be fully
aware that spatial variation in the composition of granitic rock is a paramount
consideration that may alter several of the interpretations stated. 155 11.1 EFFECT OF JOINT ORIENTATION ON THE RESIDENCE TIMES OF
WEATHERING FLUIDS
Saprolite with steeply-dipping joints is characterize by enhanced internal drainage, as
suggested by higher values of mAL/mA, low clay contents and approximately equal number percents of plagioclase- and K-feldspar (see Section 9.3). Due to the enhanced internal drainage, the saprolite retains water within joints for short periods and remains dry for extended periods between rainfall events. Owing to the extended dry spells, the saprolite is slightly altered and is characterized by lower values of mA/VT. The extensive
leaching of altered mass results in a residue composed of a high weight percent of
primary minerals, which, in the present study, was found to be composed mainly of sand-
sized feldspar grains. The inability of the slightly-weathered, coarse-grained primary
minerals to retain water against gravity during unsaturated flow conditions attending dry
spells further restricts mass alteration.
Saprolite formed from granite with nearly horizontally-oriented unloading joints is
characterized by poor internal drainage. This is suggested by lower values of mAL/mA, high contents of halloysite and or kaolinite (see section 9.6) and an elevated ratio in the number percent of K-feldspar to plagioclase feldspar (see section 9.3). Owing to the poor internal drainage, the saprolite retains water within joints for longer periods than the saprolite formed from granite with steeply-dipping joints. Weathering reactions therefore proceed for longer durations in this environment and values of mA/VT. The enhanced
capacity of fine-grained products of weathering (mainly halloysite and or kaolinite in this
study) to retain water against gravity during unsaturated flow conditions than coarse-
156 textured primary mineral grains further contributes to the alteration of primary minerals
between rainfall events.
The concentration of plant roots in the restricted rooting volumes between the unloading joints likely further contributes to increased mass alteration as (1) soil PCO2 is 1 to 2
orders of magnitude higher than atmospheric CO2 (White, 1995, p. 454 - 455),
+ (2) plant respiration CO2 is the main source of H that drives the silicate hydrolysis
reaction responsible for soil weathering (White, 1995, p. 455), and (3) the rates of
plagioclase feldspar dissolution in solutions containing organic acids (oxalate, citrate,
succinate pyruvate, and 2-ketoglutarate) are up to ten times greater than the rates
determined in solutions containing inorganic acids at the same acidity (Welch and
Ullman, 1993). At experiments conducted at 80oC and near-neutral pH, Blake and
Walters (1999) found that oxalate and citrate (2 – 20 mM) increased the rate of quartz
dissolution by up to a factor of 2.5. Blake and Walters found that the rates of dissolution and the amounts of Si and Al released from three feldspars (labradorite, orthoclase, and albite) increased regularly with increasing organic acid concentrations. Total dissolved
Al concentrations in the feldspar dissolution experiments increased by 1-2 orders of magnitude in the presence of oxalate and citrate, and reached values as high as 43 mg/L
(1.6 mM). Silicon concentrations reached values up to 65 mg/L (2.3 mM) in feldspar- organic acid experiments. Due to these factors, the saprolite is composed of a lower content of sand-sized primary minerals and a higher content of clay-sized secondary
minerals than saprolite formed from granite with steeply-dipping joints.
157 The distribution of silt-sized particles between the weathering environments also supports the characterization of the weathering environments in terms of water availability conjectured above. The mean (µα 0.05) content (on a whole saprolite basis) of silt-sized particles in saprolite developed from granite with steeply-dipping joints and in saprolite developed from granite with horizontally-oriented unloading joints was 10.3 ± 1.8 % and
3.1 ± 0.5 %, respectively (see Appendix II-A). The higher content of silt-sized particles in the former saprolite was attributed to decreased water availability in the former weathering environment (see page 91).
11.2 THE ORIGIN OF RED- AND GRAY-COLORED SAPROLITE
Saprolite composed of alternating gray-colored and red-colored layers developed from granite with horizontally-oriented unloading joints shows strong differences in particle- size distribution (Appendix II-A), CBD-extractable Fe content (Table 13), mineralogy
(see Chapter 9) as well in calculated values of mA/VT, mAL/VT, mAR/VT, mAL/mA and mAR/mA (Table 11). This section attempts to explain the mechanism by which these differences could have developed.
Unloading close to the surface causes sheeting of layers of rock from about 6 inches to a few feet thick with little or no indication of chemical weathering (Ollier, 1965). Joints that are approximately parallel to the earth’s surface form in environments of high differential stress resulting from several natural agents, including contemporary tectonic forces, vertical unloading of a rock mass that formed at depth under high triaxial compression, and suppression of expansion that would otherwise result from temperature 158 increases or chemical alteration of the rock (Holzhausen, 1989). According to
Holzhausen, opposing surfaces of sheet fractures are typically in contact, and damage, if
any, to rock adjacent to sheet fractures is generally limited to a zone less than one cm wide. It is proposed that the red- and gray colored saprolite has formed from massive
granite by the processes described below.
High differential stress near the earth’s surface (Holzhausen, 1989) leads to the
development of horizontally-oriented joints in the massive granite creating pathways for
the entry of weathering fluids. The weathering fluids react with the minerals in the
granite, solvating Si4+, Al3+, Fe2+ as well as other cations and anions from chemical
constituents in the rock. As the joint volume oscillates between saturated and unsaturated
conditions, water movement alternates from saturated flow to unsaturated flow. Under unsaturated flow conditions, weathering fluids move from the larger pore volumes defined by the joint volume into the smaller pore volumes located within the matrix of the isovolumetrically weathering rock. This permits weathering over longer duration
within the matrix of the weathering rock than immediately adjacent to the unloading
joints, leading to more chemical alteration within the matrix. The gray-colored saprolite
-3 samples, characterized by mA/VT values ( X ± s) of 2.46 ± 0.06 g cm , likely formed within
the matrix of the weathering rock, whereas the red-colored saprolite, characterized by
-3 mA/VT values of 1.42 ± 0.07 g cm , likely formed immediately adjacent to the unloading
joints. The difference in the population means (µ) of mA/VT is significant at α = 0.001.
In addition, quartz, plagioclase feldspar and K-feldspar were not detected by XRD in the clay-sized fraction of the G samples, whereas these minerals were detected in the clay-
159 sized fractions of the R samples, indicating more extensive chemical alteration in the G
samples than in the R samples.
It is likely that some of the chemical components of the clay minerals within the gray- colored saprolite were drawn from its environment and not generated in-situ. Under
unsaturated flow conditions, weathering fluids move from the larger pores defined by the
joint volume into the smaller pores located within the matrix of the isovolumetrically
weathering rock taking with it dissolved ions. As the water content decreases, the
concentrations of dissolved Si4+ and Al3+ increase, leading to the precipitation of Al-
silicate clays (kaolinite). Repeated saturation and drying cycles provide additional
components for the synthesis of clay minerals. The development of higher clay contents
within the matrix of the saprolite further enhances its ability to pull in weathering fluids
with their dissolved constituents from the coarser-grained saprolite during unsaturated
flow conditions, promoting further chemical alteration as well as providing additional
components for the synthesis of clay-sized minerals. The movement of a portion of the
altered mass from the coarser-grained red-colored layers to the finer-grained gray-colored
layers is supported by calculated mean ( X ±s) mAL/mA values of 0.74 ± 0.04 for the red-
colored saprolite samples and 0.46 ± 0.02 for the gray-colored saprolite samples. The
difference in the population means (µ) of mAL/mA is significant at α = 0.001. Over the
duration of weathering, the processes described above would result in the development of a coarser-grained layer closer to the original joint surface and a finer-grained (kaolinite- rich) layer or zone within the matrix of the isovolumetrically weathering rock further from the joint surface. 160 A mechanism for the development of the higher Fe2O3 concentrations within the red-
colored layers is proposed below, that is compatible with that proposed for the development of high clay contents within the gray-colored layers. Mean ( X ±s) CBD-
extractable Fe values (mass percent) of 2.18 ± 0.25 and 3.05 ± 0.18 were calculated for
the gray-colored and red-colored saprolite samples respectively. The difference in the
population means is significant at α = 0.01. The development of differences in the CBD-
extractable Fe contents and color can be explained as follows. During periods of
saturation, which are also likely associated with low oxygen contents in joint and pore
fluids, divalent structural Fe released from weathering reactions of biotite would remain
2+ in the Fe state. However, during periods of unsaturation, O2 diffuses from the joint
volume into the weathering rock, oxidizing some of the dissolved Fe2+. A higher level of
red pigmentation can be expected to develop in the coarser-grained layers than in the
finer-grained layers, as the former can be expected to have larger pores filled with air,
and also because they are located closer to the original joint – the entry point for oxygen
into the weathering rock. The red-colored saprolite zones can be considered analogous to
the pore lining type of redox concretions of Vepraskas (1992).
In contrast to the coarser-grained red-colored saprolite, the finer-grained material located
more distant from the joint would remain moist for longer durations than the coarser-
grained materials located closer to the joint surface, and anoxic conditions would thus be
maintained for longer durations than in the coarser-grained material. Divalent structural
Fe released from weathering reactions would migrate along a Fe2+ concentration gradient
by diffusion to oxidized water and be subject to removal or precipitation in the coarse- 161 textured material. This would result in greater depletion of Fe in the finer-grained layers compared to the coarser-grained layers, analogous to the redox depletions described by
Vepraskas (1992).
The color difference between the gray-colored and red-colored saprolites is heightened by differences in surface area per unit volume of saprolite. The coarser-grained red- colored saprolite has a much lower surface area per unit volume than the finer-grained gray-colored saprolite. The distribution of the higher extractable Fe content on a smaller surface area can be attributed to the development of a strong red hue in the coarser- grained saprolite, and the distribution of a lower extractable Fe content on a higher surface area can be attributed to the lack of red pigmentation in the finer-grained saprolite.
11.3 A CLASSIFICATION OF ISOVOLUMETRIC WEATHERING
ENVIRONMENTS
The present study shows that the interaction in weathering rocks between joint orientation with meteorological conditions leads to differences in drainage conditions within weathering rocks. It is likely that similar joint orientations in rock will lead to different drainage regimes in areas with different meteorological conditions. A classification of weathering environments based on the interaction of joint orientation and meteorological conditions is shown in Table 25. As weathering is influenced by the drainage regime as well as by chemical and textural properties of rock, the reader should be fully aware that compositional variation in rock may alter several of the interpretations stated. Effects of
162 rock joint orientation on weathering are discussed in the context of the present climate in
North Carolina’s eastern Piedmont which receives approximately 45 inches of rainfall annually (North Carolina Agricultural Extension Service AG-375, Fig. 9).
Table 25. A Classification of weathering environments based on the interaction of joint orientation of rocks with meteorology.
The table is intended to be applicable in the present climate found in the eastern Piedmont of North Carolina, which receives approximately 45 inches of rain per year.
Weathering environment
moisture-limited, moisture-unlimited, drainage unlimited 1 drainage limited 2
Orientation of joints steeply – dipping horizontally – oriented
Moisture availability low high
Mass altered per unit volume low high (mA/VT)
Altered mass lost per unit mass altered high low (mAL/mA)
[Si]4+ in weathering fluids low high
mol (Si/Al) in altered mass retained low high
Altered mass retained per unit mass low high altered (mAR/mA)
Weight percent secondary minerals low high
1 Corresponds to A and B samples in this study; 2 Corresponds to G and R samples in this study.
163 Drainage influences the availability of water as a chemical reactant and availability of
water for the leaching of ions and illuviation of fine-grained minerals. The residence
time of water in the weathering environment influences the Si4+ concentration of
weathering fluids (e.g., Siffert, 1962; Taylor et al., 2000). As water is essential for the
progress of chemical reactions at the low temperatures characteristic of regolith
(e.g., Ruxton & Berry, 1957; Helgeson et al., 1969), its availability can be expected to have a large impact on the extent of mass altered per unit volume of isovolumetrically weathered regolith (mA/VT) over a specified weathering duration. Pavich (1990) stated
that since water movement is dependent on rock structure, the rock weathering rate may
be more dependent on soil water balance and rock structure than it is on mineral
dissolution kinetics if the rock contains at least one mineral phase that reacts rapidly with dilute, acidic solutions.
Weathering is favored when water availability is coupled with enhanced drainage.
Wake County in North Carolina at present receives approximately 45 inches of rain annually. The highest groundwater recharge occurs in the months of January through
March, and the lowest groundwater recharge occurs during the months of June through
September (Daniel and Sharpless, 1983). In saprolite with enhanced internal drainage, such as in saprolite developed from granite with steeply-dipping joints, the rapid removal of weathering products during periods of saturation would create conditions far from chemical equilibrium. The work of Burch et al. (1993) with albite at 80oC and Taylor et
al. (2000) with labradorite at 25oC show increased dissolution rates with increasing
solution undersaturation. A highly undersaturated solution condition speeds up mineral
164 dissolution because the back-reaction is negligible (McBride, 1994, p. 227). Weathering
would be rapid in this type of saprolite during saturation. However, this type of saprolite
likely remains dry most of the year due to the enhanced drainage, thereby limiting the
cumulative annual mA/VT. This type of weathering environment can be characterized
under present meteorological conditions as being moisture-limited, drainage unlimited.
In saprolite with poor internal drainage developed from granite with horizontally-oriented unloading joints, water would be available for weathering reactions over longer annual durations, leading to longer mineral-solution contact times and higher solution saturation states (e.g., Siffert, 1962; Taylor et al., 2000). In such environments, the experimental work of Burch et al. (1993) and Taylor et al. (2000) suggest slower mineral dissolution rates than found in the moisture-limited, drainage unlimited environment. However, as weathering can proceed for longer durations annually, cumulative mA/VT is likely greater.
Such an environment can be characterized as being drainage-limited, moisture unlimited.
However, the relative extent of mass alteration on a bulk volume or landscape scale in the two weathering environments could also depend on joint spacing.
Due to the effects of residence time of water on mineral dissolution as demonstrated by
Siffert (1962) with quartz and Taylor et al.(2000) with labradorite, the Si4+ concentrations
that develop in weathering fluids within quartz- and aluminosilicate-bearing rocks with
steeply-dipping joints would be lower than in rocks with horizontally-oriented joints. In
addition, dissolved constituents in saprolite with steeply-dipping joints would also have
less time to chemically react and precipitate as clay minerals. These factors could result
165 in the synthesis of lower amounts of clay minerals in saprolite with steeply-dipping
joints. For example, the growth rate of kaolinite shows a linear dependence on the
solution saturation state (Nagy et al. 1990, 1991; Nagy and Lasaga, 1993). As a result,
higher values of mAL/mA and lower values of mAR/mA can be expected in saprolite
developed from rocks with steeply-dipping joints than in saprolite developed from granite
with horizontally-oriented unloading joints.
Weathered residues that develop in rocks with steeply-dipping joints are likely to have
lower molar Si/Al than the residues that develop in rocks with horizontally-oriented joints
due to lower values of mAL/mA in the former weathering environment as shown in the present study and due to the enhanced mobility of Si in comparison to Al (e.g., Gislason et al., 1996; Middleburg et al., 1988). Gibbsite, kaolinite, and montmorillonite are stable
at very low, moderate, and high H4SiO4 activity, respectively (Rai and Kittrick, 1989,
page 185). As a result, secondary mineralogy is also likely to vary between the two
weathering environments.
It must be recognized that the classification of the internal environment of saprolite as
being moisture-limited or drainage-limited is valid only under specified meteorological
conditions. If the meteorological conditions in North Carolina’s atmosphere became
more humid, the difference in the average annual weathering rate between the
environments classified today as being moisture-limited and drainage-limited would
narrow, and beyond some unknown threshold value in rainfall, the annual weathering rate
in today’s moisture-limited environment could conceivably exceed that found in today’s
166 drainage-limited environment, owing to the rapid removal of weathering products in the former. Similarly, if the climate of North Carolina were to become more arid, the difference in annual weathering rate between the present moisture-limited and drainage- limited environments would widen due to the enhanced capacity of the drainage-limited environment to retain captured rainfall.
167 CHAPTER 12
SUMMARY OF CONCLUSIONS
From observing excavation activities proceeding at a granite quarry located on the
Rolesville granitic batholith in Knightdale, North Carolina over the span of about six
months, the author observed that saprolite developed from granite with steeply-dipping
joints differed markedly in geometric, physical and mineralogical properties from saprolite developed from granite with horizontally-oriented unloading joints.
Commercial operations at the site precluded detailed observations and protracted investigation of all but a few saprolite exposures. Blasting was usually required prior to removing overburden in areas underlain by granite with horizontal joints, whereas it was not required in areas underlain by granite with steeply dipping joints. Field and laboratory investigation revealed differences in the distribution of weathering zones in space, particle-size distribution, bulk density, pH, cation exchange capacity (CEC), citrate-bicarbonate-dithionite (CBD) extractable Fe, percent base saturation (% BS), mass altered per unit volume (mA/VT), altered mass lost per unit volume (mAL/VT), altered
mass retained per unit volume (mAR/VT), altered mass lost per unit mass altered
(mAL/mA), altered mass retained per unit mass altered (mAR/mA), as well as in the stability
of quartz and feldspar and in the amounts of secondary minerals synthesized. The
assumption that all conditions were similar except for joint orientation is made
throughout the study. This assumption is supported by the presence of quartz,
plagioclase feldspar, K-feldspar, biotite, muscovite, hydroxy apatite and allanite in the
168 saprolite – all of which were detected in the parent granitic rocks at the study site by
Kosecki and Fodor (1997).
Saprolite developed from granite with steeply-dipping joints was sandy textured in the
1 m to 4 m depth interval, and showed no core stones within this depth interval. The
distribution (µ α 0.05, in mass percent) of sand-, silt-, and clay-sized particles was
82.4 ± 2.7, 10.3 ± 1.8, and 2.3 ± 2.5, respectively, in the whole saprolite and 86.8 ± 3.1,
10.8 ± 1.5 and 2.4 ± 2.5, respectively, in the fine-earth (< 2 mm) fraction. Bulk density
-3 (µ α 0.05) was 1.66 ± 0.06 (g cm ). In contrast, saprolite developed from granite with
horizontally-oriented unloading joints showed an irregular distribution of weathering
zones. Extensively weathered, horizontally-oriented saprolite zones that were easily
excavated with a hand shovel alternated with horizontally oriented weathered rock that
resisted breakage with a hand shovel. The saprolite zones were composed of alternating,
horizontally-oriented, gray-colored and red-colored layers on the scale of about 1 to 2
cm, whereas the weakly defined foliation in the rock was nearly vertical. This type of
saprolite was less sandy. The distribution (µ α 0.05, in mass percent) of sand-, silt-, and
clay-sized particles was 50.1 ± 10.4, 3.1 ± 0.5, and 46.8 ± 10.5, respectively, in the whole
saprolite and 50.1 ± 10.3, 3.1 ± 0.5, and 46.8 ± 10.4, respectively, in the fine-earth
-3 fraction. Bulk density (µ α 0.05) was 1.55 ± 0.01 (g cm ). The difference between the
mean contents of sand-, silt-, and clay-sized particles of the saprolite developed from granite with contrasting joint patterns in the fine-earth fraction as well as in the whole
169 saprolite differed statistically at α = 0.001. The mean values of bulk density differed
statistically at α = 0.01.
The fine-earth fraction of saprolite developed from granite with steeply dipping joints was characterized (µ α 0.05) by pH values of 5.8 ± 0.2, mass percent Fe2O3 of 0.21 ± 0.09,
CEC (at pH 7.0) of 3.95 ± 0.88 (cmol+ kg -1) and % BS of 36.66 ± 9.93. In contrast, the
fine-earth fraction of saprolite developed from granite with horizontally-oriented
unloading joints was characterized (µ α 0.05) by pH values of 5.1 ± 0.2, mass percent
+ -1 Fe2O3 of 2.68 ± 0.28, CEC (at pH 7.0) of 8.28 ± 0.91 (cmol kg ) and % BS of
19.73 ± 9.22. The mean values of pH, mass percent Fe2O3, and CEC between the two
saprolite populations differed at α = 0.001. The mean values of % BS differed at
α = 0.05. However, the differences between the mean values of extractable bases
(Ca, Mg, Na, and K) were not different at α = 0.05. Given the low content of clay-sized
particles in the saprolite developed from granite with steeply-dipping joints, it is inferred
that a significant component of its CEC resides within sand- and silt-sized particles that
are completely or partially pseudomorphed by secondary minerals.
Mass altered per unit volume (mA/VT), altered mass lost per unit volume (mAL/VT), and altered mass retained per unit volume (mAR/VT) were calculated for the whole saprolite using the equations mass % primary minerals = 100 [ρs - (mA/VT)] / ρb (8)
(mAL / VT) = ρs - ρb (5)
170 and
mA/VT = (mAR + mAL)/ VT (1) respectively. The density (ρs) of the parent granite was measured (µ 0.05) to be
2.62 ± 0.01 g cm-3. In saprolite developed from granite with steeply-dipping joints,
-3 calculated mean (µ α 0.05) values (g cm ) of mA/VT, mAL / VT, and mAR / VT were
1.17 ± 0.12, 0.96 ± 0.06 and 0.21 ± 0.05, respectively. The corresponding values in
saprolite developed from granite with horizontally-oriented unloading joints were
1.85 ± 0.15, 1.08 ± 0.02 and 0.77 ± 0.17, respectively. Calculated mean (µ α 0.05) values of mAL/mA were 0.82 ± 0.03 for the former saprolite and 0.58 ± 0.06 for the latter,
indicating greater leaching in the former saprolite. The differences in the calculated population means of mA/VT, mAR/VT, mAR/mA and mAL/mA were statistically significant at α = 0.001. The difference between the population means of mAL/VT was statistically
significant only at α = 0.05.
The predominant mineral in saprolite developed from granite with steeply dipping joints
was feldspar, composed of approximately equal amounts of plagioclase feldspar and
potassium feldspar. The predominant mineral in the red colored saprolite developed from
granite with horizontally oriented unloading joints was potassium feldspar. Kaolinite
and/or halloysite was the predominant mineral in the gray colored layers developed from
granite with horizontally oriented joints, suggesting longer residence times of weathering
fluids within the saprolite, allowing for greater mineral alteration, as well as the
development of high concentrations of Si4+ necessary for the precipitation of the clay
171 minerals. Potassium feldspar, plagioclase feldspar, and quartz were not detected by XRD in the clay-sized fraction of the gray colored samples, indicating more extensive mineral alteration. The clay-sized fraction of all samples developed from granite with steeply- dipping joints was dominated by kaolinite, whereas the clay-sized fraction of all samples derived from granite with horizontally-oriented joints was dominated by kaolinite and / or halloysite.
Potassium-saturated, oriented, air-dried specimens of the clay-sized fraction from several
A, B, G and R samples showed XRD peaks in the interval 0.725 to 0.786 nm. When heated to 350oC, the spacings ranged from 0.699 to 0.713 nm. Magnesium-saturated specimens rarely showed increased XRD spacings upon treatment with glycerol, thus
ruling out the presence of an interstratified expandable 2:1 mineral. The reduction of the
spacing upon heating suggested that the kaolinite and or halloysite are interstratified with
hydroxy interlayered vermiculite.
The sand-sized fractions of saprolite developed from granite with horizontally oriented
unloading joints (both the gray colored and red colored saprolites) were particularly
enriched in K-feldspar relative to plagioclase feldspar. In contrast, the contents of
plagioclase feldspar and K-feldspars were similar in the sand-sized fractions of saprolite
developed from granite with steeply dipping joints. This suggested thermodynamically
inhibited dissolution of K-feldspar and kinetically controlled plagioclase dissolution in
the former saprolite and kinetically controlled dissolution of both K-feldspar and
plagioclase in the latter, indicating longer residence times of weathering fluids in the
172 former saprolite. The quartz content was lower in the saprolite developed from granite with horizontally oriented joints. It is plausible that organic acids exuded from roots concentrated within the weathered zones about the unloading joints enhanced the dissolution of quartz as well as plagioclase feldspar. These findings suggest that the alteration of plagioclase feldspar and quartz provided most of the chemical constituents for the synthesis of kaolinite and/or halloysite in the gray-colored saprolite.
One or more of the aluminum hydroxides (gibbsite, bayerite, nordstrandite) and aluminum oxyhydroxides (boehmite, pseudoboehmite, diaspore) were detected in one or more particle size fractions in every saprolite sample. Of these, in all three particle size fractions, the most frequently detected mineral phase was nordstrandite. It was not possible to detect differences in the quantities of these minerals in the saprolites developed from granite with different joint orientations due to the semiquantitative nature of the mineral investigation. These minerals would be capable of imparting to the saprolite a capacity to exchange anions at pH values more acidic than their point of zero charge (PZC).
Saprolite examined in this study was classified based on the relative proportions of
0 † (m1 R/VT) 100/ρs , (mAR/VT) 100/ρs, and (mAL/VT) 100/ρs. The calculated values of these parameters for the saprolite developed from granite with steeply-dipping joints were
55.35, 7.94 and 36.71, respectively, and was classified as ‘moderately altered, highly leached’. The respective classification parameters for saprolite developed from granite
† 0 (m1 R/VT) is the mass of primary minerals remaining per unit volume of saprolite. 173 with horizontally-oriented unloading joints were 29.41, 29.47 and 41.12, respectively,
and was classified as ‘severely altered, moderately leached’.
The differences in the distribution of weathering zones in space, particle-size distribution,
mA/VT, mAL/VT, mAR/VT, as well as mAL/mA and mAR/mA in saprolite developed from
granite with contrasting joint patterns can be explained by the influence of joint
orientation on the flux of weathering fluids through rock. Saprolite developed from
granite with steeply-dipping joints, on account of enhanced internal drainage, remains dry
for extended periods between rainfall events. Owing to the extended dry spells, the
saprolite is slightly altered, characterized by low values of mA/VT. The enhanced internal
drainage removes much the alteration products from the weathering environment in the
form of ions during and immediately following rainfall events, leading to high values of
mAL/mA and low values of mAR/mA, leaving behind a residue composed of a high mass
percent of primary minerals. In this study, the residues were of a sandy texture, as the parent rock was coarse-grained (2 to 0.05 mm). The inability of the slightly-weathered,
coarse-grained primary minerals to retain water against gravity during dry spells further
restricts mass alteration.
In contrast, saprolite formed from granite with horizontally-oriented unloading joints
retains water within the joints for longer periods. Weathering reactions therefore likely
proceed for longer durations, leading to higher values of mA/VT. The flux of weathering
fluids within the weathering rock is low owing to the low hydraulic gradient within the
joints, resulting in low mAL/mA values and high mAR/mA values, leading to the synthesis
174 of a high content of clay-sized secondary minerals. The enhanced capacity of the fine-
grained products of weathering (mainly halloysite and/or kaolinite in this study) to retain
water against gravity under unsaturated flow conditions over coarser-textured primary
mineral grains furthers the alteration of primary minerals, contributing further to mA/VT.
The resulting saprolite has a lower content of sand-sized primary minerals and a higher
content of clay-sized secondary minerals compared to saprolite developed from granite
with steeply-dipping joints.
As silt-sized primary mineral particles are more chemically reactive per unit mass than sand-sized particles for a given mineral type, the ratio of sand- to silt-sized particles can be expected to be different in the two types of saprolite due to differences in water availability. In this study, the silt content (mass percent) for saprolite developed from granite with steeply-dipping joints was higher than in saprolite developed from granite with unloading joints, supporting the characterization of the weathering environments in terms of water availability conjectured above based on joint orientation and supported by differences in calculated values of mA/VT, mAL/mA, and mAR/mA as well as the
distribution of feldspars and kandites.
Saprolite developed from granite with horizontally-oriented unloading joints that is composed of alternating gray-colored and red-colored layers showed strong differences in particle-size distribution, CBD-extractable Fe, mineralogy, CEC, as well in calculated values of mA/VT, mAR/VT, mAL/mA and mAR/mA. The origin of these differences can be
explained by the movement of weathering fluids during unsaturated flow conditions from
175 the coarser-grained unloading joint volumes into the adjacent, finer-grained rock, taking
with it dissolved chemical constituents as well. This prolonged the duration of
weathering reactions within the matrix of the weathering rock, leading to higher values of
mA/VT, and also allowed the precipitation of high contents of kaolinite and/or halloysite
as well due to the higher concentrations of Si4+ and Al3+ in the weathering fluids.
The movement of a portion of the altered mass from the coarser-grained red-colored
layers to the finer-grained gray-colored layers is supported by calculated mean ( X ± s) mAL/mA values of 0.74 ± 0.04 for the red-colored saprolite samples and 0.46 ± 0.02 for the gray-colored saprolite samples. The difference in the population means (µ 0.05) of mAL/mA between the red-colored and gray-colored layers is significant at α = 0.001. The
less altered, sandy-textured, red-colored saprolite likely formed near the walls of
unloading joints and the more altered, finer-grained, gray-colored saprolite likely formed
inside the weathering rock further from the walls of unloading joints.
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197 APPENDIX I
EQUATIONS DEVELOPED IN THE TEXT
mA/VT = (mAR + mAL )/ VT (1)
o ρs = (m1 R / VT) + (mAR / VT) + (mAL / VT) (2)
o mA/VT = ρs – m1 R / VT (3)
o ρb = (m1 R / VT) + (mAR / VT) (4)
(mAL / VT) = ρs – ρb (5)
ρb = ρs – [(mA/VT) – (mAR/VT)] (6)
o mass % primary minerals = 100 (m1 R ) / (VT.ρb) (7)
mass % primary minerals = 100 [ρs – (mA/VT)] / ρb (8)
mass % secondary minerals = 100 mAR / (VT.ρb) (9)
mass % secondary minerals = 100 [(mA/VT) – (mAL/VT)] / ρb (10)
mass % secondary minerals = 100 [(mA/VT) – (ρs – ρb )] / ρb (11)
o o ρs 100 (m1 R/VT) 100 (m2 R/VT) ______ρb = { + } (12) 100 [ ρs ] [ ρs ]
198 APPENDIX II ATTRIBUTES OF PARTICLE-SIZE DISTRIBUTION
APPENDIX II –A Statistical attributes of the particle size distribution of saprolite (mass percent).
Fine-earth basis Whole saprolite basis SAMPLE GROUP sand silt clay sand silt clay
X 84.4 12.0 3.6 84.3 11.9 3.6 A s 3.7 1.5 4.1 3.6 1.5 4.1
µ α 0.05 84.4±5.8 12.0±2.4 3.6±6.5 84.3±5.8 11.9±2.4 3.62±6.5
X 89.3 9.6 1.1 80.5 8.7 1.0 B s 1.4 1.2 0.4 1.4 1.2 0.4
µ α 0.05 89.3±2.2 9.9±2.0 1.1±0.7 80.5±2.2 8.7±1.9 1.0±0.6
X 11.2 0.4 88.4 11.2 0.4 88.3 G s 3.9 0.4 4.2 3.9 0.4 7.3
µ α 0.05 11.2±9.7 0.4±0.9 88.4±10.6 11.2±9.7 0.4±0.9 88.3±10.6
X R 76.5 4.9 18.5 76.4 4.9 18.4 s 4.6 0.5 4.5 4.7 0.5 4.5
µ α 0.05 76.5±11.3 4.9±1.2 18.5±11.3 76.4±11.6 4.9±1.2 18.4±11.2
X 86.8 10.8 2.4 82.4 10.3 2.3 A&B s 3.6 1.8 3.1 3.3 2.1 3.0
µ α 0.05 86.8±3.1 10.8±1.5 2.4±2.5 82.4±2.7 10.3±1.8 2.3±2.5
X 50.1 3.1 46.8 50.1 3.1 46.8 s 4.2 0.2 4.2 4.2 0.2 4.2 R & G* µ α 0.05 50.1±10.3 3.1±0.5 46.8±10.4 50.1±10.4 3.1±0.5 46.8±10.5
COMPARISON OF POPULATION MEANS
µA&B µA&B µA&B µA&B µA&B µA&B (A&B) ≠ ≠ ≠ ≠ ≠ ≠
vs µG&R µG&R µG&R µG&R µG&R µG&R (G&R)* (α 0.001) (α0.001) (α 0.001) (α 0.001) (α0.001) (α 0.001)
X = sample mean; S = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. * Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
199 APPENDIX II-B
Statistical attributes of the ratios between masses of selected particle-size fractions on a whole saprolite basis.
Sample Group Sand / silt Sand / clay Silt / clay X 7.1 47.1 6.9 A s 0.8 31.2 5.1
µ α 0.05 7.1±1.4 47.1±49.7 6.9±8.1
X 9.4 95.2 10.1 B s 1.3 56.8 5.7
µ α 0.05 9.4±2.1 95.2±90.4 10.1±9.1
X 43.8 0.1 0.0 G s 29.9 0.0 0.0
µ α 0.05 43.8±74.2 0.1±0.1 0.0±0.0
X 15.6 4.3 0.3 R s 2.0 1.2 0.1
µ α 0.05 15.6±4.9 4.3±2.9 0.3±0.2
X 8.3 71.1 8.5 A&B s 1.6 49.6 5.3
µ α 0.05 8.3±1.3 71.1±41.5 8.5±4.4
X 16.2 1.1 0.1 G&R* s 1.6 0.2 0.0
µ α 0.05 16.2±4.0 1.1±0.4 0.1±0.0
COMPARISON OF POPULATION MEANS
µA&B µA&B µA&B (A&B) ≠ ≠ ≠
vs µG&R µG&R µG&R (G&R*) (α 0.001) (α 0.05) (α 0.05)
A vs B µA ≠ µB (α 0.05) G vs R Cannot reject
µG ≠ µR (α 0.05)
(A&B) vs R µA&B ≠ µR (α 0.001)
X = sample mean; S = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. * Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed. 200 APPENDIX II-C
Statistical attributes of subfractions of the sand-sized fraction of saprolite (2.0 mm – 0.50 mm) as mass percent of the total sand-sized fraction.
Very Coarse Coarse Medium Fine Very Fine Sample Sand Sand Sand Sand Sand number 2.0 -1.0 1.0 - 0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm X 0.9 18.4 32.3 34.0 14.4 A s 0.4 3.6 3.2 1.4 2.2 µ α 0.05 0.9±0.7 18.4±5.7 32.3±5.1 34.0±2.3 14.4±3.5
X 21.6 28.6 22.7 17.3 9.7
s 2.2 1.8 1.7 1.7 1.9 B µ α 0.05 21.6±3.5 28.6±2.9 22.7±2.8 17.3±2.6 9.7±3.1
X 11.3 22.0 21.8 26.7 18.2
s 3.9 2.6 2.7 1.2 1.9 G µ α 0.05 11.3±9.6 22.0±6.5 21.8±6.6 26.7±3.0 18.2±4.7
X 14.0 32.8 25.8 18.8 8.5 R s 0.5 1.1 0.3 0.4 0.4 µ α 0.05 14.0±1.3 32.8±2.8 25.8±0.8 18.8±1.0 8.5±1.1
X 11.3 23.5 27.5 25.6 12.1 A&B s 11.1 6.1 5.6 9.0 3.2 µ α 0.05 11.3±9.3 23.5±5.1 27.5±4.7 25.6±7.5 12.1±2.6
X 13.8 31.9 25.5 19.5 9.3 R & G* s 0.8 1.0 0.2 0.5 0.4 µ α 0.05 13.8±2.0 31.9±2.6 25.5±0.5 19.5±1.3 9.3±1.1
COMPARISON OF POPULATION MEANS
Cannot Cannot Cannot Cannot reject reject reject reject (A&B) µA&B µA&B µA&B µA&B µA&B vs = ≠ = = = (G&R)* µG&R µG&R µG&R µG&R µG&R (α 0.05) (α 0.05) (α 0.05) (α 0.05) (α 0.05)
X = sample mean; S = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. * Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed.
201 APPENDIX II-D
Particle size distribution within the sand-sized fraction expressed as mass percent of the fine-earth fraction of saprolite.
Sample Depth Sand subfractions as a fraction of the number (m) fine-earth (< 2 mm) fraction (mass percent)
Very Coarse Medium Fine Very Fine Coarse Sand Sand Sand Sand Sand
2.0 - 1.0 1.0 - 0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm
123A 1 0.7 13.7 26.9 26.6 11.1 124A 2 1.3 20.5 25.5 27.8 11.5 125A 3 0.5 13.7 31.2 30.5 11.0 126A 4 0.7 14.2 25.2 29.8 15.0
123B 1 19.3 23.8 22.4 16.9 7.8 124B 2 17.2 25.0 20.4 16.3 10.0 125B 3 22.3 27.6 20.2 13.6 6.8 126B 4 18.4 25.9 18.1 15.0 10.0
300G * 0.9 2.3 2.4 3.0 2.0 300R * 10.7 27.1 20.3 14.9 6.6 301G * 1.4 3.8 3.7 4.0 2.5 301R * 11.1 25.0 20.3 15.2 7.1 304G * 1.2 1.5 1.4 2.0 1.5 304R * 10.7 23.2 18.6 13.2 5.8
* Sample depth ranged from the surface to about 4m as the samples were collected after exploding the regolith with dynamite.
202 APPENDIX II-E
Statistical attributes of sand subfractions (2.0 mm – 0.50 mm) in the fine-earth (<2 mm) fraction of saprolite (mass percent).
Very Coarse Coarse Medium Fine Very Fine Sample Sand Sand Sand Sand Sand number 2.0 -1.0 1.0 - 0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm X 0.8 15.5 27.2 28.7 12.2 s 0.4 3.3 2.8 1.8 1.9
A µ α 0.05 0.8±0.6 15.5±5.3 27.2±4.4 28.7±2.9 12.2±3.0
X 19.3 25.6 20.3 15.5 8.7 B s 2.2 1.6 1.8 1.5 1.6
µ α 0.05 19.3±3.4 25.6±2.6 20.3±2.8 15.5±2.3 8.7±2.6
X 1.2 2.5 2.5 3.0 2.0
s 0.2 1.2 1.1 1.0 0.5 G µ α 0.05 1.2±0.6 2.5±2.9 2.5±2.8 3.0±2.5 2.0±1.2
X 10.7 25.2 19.7 14.4 6.5 s 0.4 1.9 1.0 1.0 0.6
R µ α 0.05 10.7±0.9 25.2±4.8 19.7±2.4 14.4±2.7 6.5±1.5
X 10.1 20.6 23.8 22.1 10.4 A&B s 10.0 5.9 4.3 7.2 2.5 µ α 0.05 10.1±8.4 20.6±4.9 23.8±3.6 22.1±6.0 10.4±2.1
X 6.9 15.9 12.7 9.8 4.7 R & G* s 0.3 1.4 1.0 1.0 0.6 µ α 0.05 6.9±0.7 15.9±3.5 12.7±2.6 9.8±2.6 4.7±1.4
COMPARISON OF POPULATION MEANS
Cannot Cannot reject reject (A&B) µA&B µA&B µA&B µA&B µA&B vs = = ≠ ≠ ≠
(G&R)* µG&R µG&R µG&R µG&R µG&R (α 0.05) (α 0.05) (α 0.01) (α 0.02) (α 0.01)
X = sample mean; s = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed. 203 APPENDIX II-F
Particle size distribution within the sand-sized fraction expressed as mass percent of whole saprolite.
Sand subfractions as a fraction of whole-saprolite (mass percent)
Sample Depth Very Coarse Medium Fine Very Fine number (m) Coarse Sand Sand Sand Sand Sand
2.0 -1.0 1.0 -0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm
123A 1 0.7 13.7 26.9 26.6 11.1 124A 2 1.3 20.5 25.5 27.8 11.5 125A 3 0.5 13.7 31.2 30.5 11.0 126A 4 0.7 14.2 25.1 29.7 15.0
123B 1 17.6 21.7 20.5 15.4 7.1 124B 2 15.4 22.3 18.2 14.6 8.9 125B 3 20.0 24.7 18.1 12.2 6.1 126B 4 16.8 23.6 16.4 13.7 9.1
300G * 0.9 2.3 2.4 3.0 2.0 300R * 10.7 27.1 20.3 14.9 6.6 301G * 1.4 3.8 3.7 4.0 2.5 301R * 11.1 25.0 20.3 15.2 7.1 304G * 1.2 1.5 1.4 2.0 1.5 304R * 10.3 23.2 18.6 13.2 5.8
* Sample depth ranged from the surface to about 4m as the samples were collected after exploding the regolith with dynamite.
204 APPENDIX II-G
Statistical attributes of sand subfractions (2.0 mm – 0.50 mm) on a whole-saprolite basis (mass percent).
Very Coarse Coarse Medium Fine Very Fine Sample Sand Sand Sand Sand Sand Group 2.0 -1.0 1.0 - 0.5 0.5 - 0.25 0.25 - 0.10 0.10 - 0.05 mm mm mm mm mm X 0.8 15.5 27.2 28.6 12.2 A s 0.4 3.3 2.8 1.8 1.9
µ α 0.05 0.8±0.6 15.5±5.2 27.2±4.4 28.6±2.9 12.2±3.0
X 17.4 24.0 18.3 14.0 7.8 B s 1.9 1.3 1.6 1.4 1.5
µ α 0.05 17.4±3.1 24.0±2.1 18.3±2.6 14.0±2.2 7.8±2.3
X 1.2 2.5 2.5 3.0 2.0 G s 0.2 1.2 1.1 1.0 0.5 µ α 0.05 1.2±0.6 2.5±2.9 2.5±2.8 3.0±2.5 2.0±1.2
X 10.7 25.1 19.7 14.4 6.5 R s 0.4 1.9 1.0 1.1 0.6
µ α 0.05 10.7±1.0 25.1±4.8 19.7±2.5 14.4±2.7 6.5±1.6
X 9.1 19.3 22.7 21.3 10.0 A&B s 9.0 4.6 5.2 8.0 2.8
µ α 0.05 9.1±7.5 19.3±3.9 22.7±4.4 21.3±6.7 10.0±2.3
X 6.8 15.9 12.7 9.8 4.7 R & G* s 0.3 1.4 1.0 1.1 0.6
µ α 0.05 6.8±0.8 15.9±3.5 12.7±2.6 9.8±2.6 4.7±1.4
COMPARISON OF POPULATION MEANS
Cannot Cannot reject reject (A&B) µA&B µA&B µA&B µA&B µA&B vs = = ≠ ≠ ≠ (G&R*) µG&R µG&R µG&R µG&R µG&R (α 0.05) (α 0.05) (α 0.02) (α 0.05) (α 0.02)
X = sample mean; s = sample standard deviation; µ α 0.05 = population mean at the 95 % confidence level. * Adjusted to represent the volumetric ratio in which these two types of layers were determined to occur in the field. A volumetric ratio ( X ± s) of 58.2 ± 0.7 % red layers and 41.8 ± 0.5 % gray layers was determined using two samples (clods) from which a total of 9 subsamples were analyzed. 205 APPENDIX III
X-RAY DIFFRACTION DATA FOR THE SAND-SIZED FRACTION
APPENDIX III-A
X-ray diffractograms of Na-saturated randomly-oriented specimens of the sand-sized fraction at 25oC
600
500 126A
400
125A 300 intensity
200 124A
100
123A
0 0 10203040506070 degrees 2 theta
206 APPENDIX III-A continued
600
500
400 126B
300
intensity 125B
200
124B
100
123B
0 0 10203040506070 degrees 2 theta
207 APPENDIX III-A continued
600
304R
500
304G
400
301R
300
intensity 301G
200
300R 100
300G
0 0 10203040506070 degrees 2 theta
208 APPENDIX III-B
XRD peaks (nm) indicative of muscovite and biotite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Biot = biotite; Ms = muscovite; Vc-Hb = vermiculite-hydrobiotite; Qtz = quartz; MC(I) = intermediate microcline; All = allanite: HA = hydroxy apatite; Or = orthoclase; Gibb = gibbsite; Bay = bayerite; Kaol = kaolinite; Vc = vermiculite.
Refe- Biot Biot Biot Biot Biot Biot Biot Ms Ms rence 1.01(x) 0.5 0.337(x) 0.266(8) 0.218(8) 0.167(8) 0.154(8) 0.332(x) 0.150 XRD Ms (weak) All Qtz (3) peaks 0.995(x) Ms 0.218(4) 0.154(2) [060] → 0.497(3) Sample Number Vc-Hb All Bay Zir Kaol Qtz ↓ 0.340(4) 0.271(7) 0.222(x) 0.171(4) 0.159(6) 0.334(x) Qtz HA MC(I) Dias Vc MC(I) Nord 0.334(x) 0.263(2) 0.216(3) 0.171(2) 0.153(7) 0.334(5) 0.151 MC(I) All Gibb Or (1) 0.334(5) 0.263(4) 0.169(1) 0.331(x) Kaol Hall Gibb 0.149 0.168(2) 0.331(2) (3) Bm 0.166(1) Zir 0.165(1)
123 A 1.021 0.594 --- 0.265 0.217 0.167 0.154 0.335 0.149 shared 0.166 * *** with MC(I) 0.216(3) 124 A ------0.155 0.331 --- * ***
125 A ------0.170 0.155 ------
126 A 0.998 0.586 ------0.167 0.157 0.333 --- 0.166 ***
209 APPENDIX III-B continued.
Reference Biot Biot Biot Biot Biot Biot Biot Ms Ms XRD 1.01(x) 0.5 0.337(x) 0.266(8) 0.218(8) 0.167(8) 0.154(8) 0.332(x) 0.150 peaks Ms (weak) All Qtz (3) → 0.995(x) Ms 0.218(4) 0.154(2) [060] Sample 0.497(3) Number ↓ Vc-Hb All Bay Zir Kaol Qtz 0.340(4) 0.271(7) 0.222(x) 0.171(4) 0.159(6) 0.334(x) Nord Qtz HA MC(I) Dias Vc MC(I) 0.151 0.334(x) 0.263(2) 0.216(3) 0.171(2) 0.153(7) 0.334(5) (1) MC(I) All Gibb Or Kaol 0.334(5) 0.263(4) 0.169(1) 0.331(x) 0.149 Hall Gibb (3) 0.168(2) 0.331(2) Bm 0.166(1) Zir 0.165(1)
123 B 0.993 ------0.222 0.166 0.158 0.332 --- 0.165 0.154 *** * 124 B 0.955 ------0.158 ------0.153
125 B ------0.155 0.331 --- * ***
126 B 0.955 ------0.222 --- 0.156 ------* 0.153
300 G ------0.167 0.154 0.334 --- * * ***
300 R ------0.336 --- 0.219 0.167 0.157 0.331 --- * * 0.155 ** 0.168 *** 0.169 301 G ------0.222 0.166 0.153 ------* * *
301 R ------0.222 0.166 0.154 0.331 --- * ** ***
304 G ------0.222 0.166 0.156 0.331 --- 0.165 0.154 *** * 304 R 0.982 ------0.167 0.154 0.332 --- * * *** 0.165
210 APPENDIX III-C
XRD peaks (nm) indicative of 2:1 phyllosilicates (excluding muscovite and biotite) in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Reg. Int. = muscovite and or biotite regularly interstratified with vermiculite and or HIV; Vc-Hb = vermiculite-hydrobiotite; Vc = vermiculite; Hall = halloysite; HA = hydroxy apatite; Nord = nordstrandite; Biot = biotite; Rand. Int. = muscovite and or biotite randomly interstratified with vermiculite and or HIV; HIV = hydroxy-interlayered vermiculite; Bay = bayerite; Dias = diaspore; All = allanite; Ms = muscovite; Kaol = kaolinite; Zir = Zircon.
Reference Reg. Vc-Hb Vc-Hb Vc-Hb Rand. (002) Vc Vc Vc Vc Vc XRD Int. 0.450(6) 0.340 0.275 Int. of 1.4 0.457 0.262(5) 0.253 0.153(7) peaks 2:1 (4) (2) 2:1 Rand. HIV (6) Vc (5) → Int. 1.4 0.260(4) Sample 2:1 Number Bay HA Kaol Qtz ↓ Vc HA HA 0.471 0.263(2) 0.255 0.154(2) 0.457(6) 0.345 0.278 (9) All (3) Biot Hall (4) (3) Dias 0.263(4) Zir 0.154(8) 0.445 Nord HA 0.471(1) Ms 0.252 Nord 0.345 0.273 Vc-Hb 0.257(6) (5) 0.151(1) (1) (8) 0.450(6) Vc Ms Biot 0.257(5) 0.150(3) 0.337 (x)
123 A ------1.147 0.594 ------0.154 *
124 A ------0.341 ------0.261 --- 0.155 *** * *
125 A ------0.341 ------0.155 **
126 A ------0.277 1.132 0.586 ------0.259 ------0.276
211 APPENDIX III-C continued.
Refe- Reg. Vc-Hb Vc-Hb Vc-Hb Rand. (002) Vc Vc Vc Vc Vc rence Int. 0.450 0.340 0.275 Int. of 1.4 0.457 0.262(5) 0.253(5) 0.153(7) XRD 2:1 (6) (4) (2) 2:1 Rand. HIV (6) Vc peaks Int. 1.4 0.260(4) → 2:1 Sample Bay HA Kaol Qtz Number Vc HA HA 0.471 0.263(2) 0.255(3) 0.154(2) ↓ 0.457 0.345 0.278 (9) All Zir Biot (6) (4) (3) Dias 0.263(4) 0.252(5) 0.154(8) Hall Nord HA 0.471(1) Ms Nord 0.445 0.345 0.273 Vc-Hb 0.257(6) 0.151(1) (1) (8) 0.450(6) Vc Ms Biot 0.257(5) 0.150(3) 0.337 (x)
123 B ------0.154 *
124 B --- 0.452 ------0.153
125 B ------0.341 ------0.260 --- 0.155 *** ** *
126 B ------0.156 0.153
300 G 2.386 ------1.186 ------0.154 * *
300 R ------0.341 ------0.155 *** ***
301 G ------1.132 ------0.153 1.111 *
301 R ------0.154 **
304 G ------0.275 1.125 ------0.156 1.115 0.154 * 304 R ------1.111 ------0.253 0.154 * * *
212 APPENDIX III-D
XRD peaks (nm) indicative of halloysite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75- 100%; ** 50-75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Hall = halloysite; Vc-Hb = vermiculite-hydrobiotite; Zir = zircon; Kaol = kaolinite; Psbm = pseudo boehmite; Gibb = gibbsite.
Reference Hall Hall Hall XRD peaks 0.730 0.445 0.442 → (7) (x) Sample Kaol Number 0.441 ↓ (6)
Vc-Hb Zir 0.450(6) 0.443(5) Zir Kaol 0.443(5) 0.437(6) Gibb 0.437(5)
123 A 0.734 ------
124 A ------
125 A ------
126 A ------
213 APPENDIX III-D continued.
Refe Hall Hall Hall Reference 0.730 0.445 0.442 XRD peaks (7) (x) → Kaol Sample 0.441 Number (6) ↓ Vc-Hb Zir 0.450(6) 0.443(5) Zir Kaol 0.443(5) 0.437(6) Gibb 0.437(5)
123 B ------0.442
124 B ------
125 B ------0.437 ***
126 B ------
300 G ------
300 R ------
301 G ------
301 R ------
304 G ------
304 R ------
214 APPENDIX VIII-E
XRD peaks (nm) indicative of kaolinite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2 θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Kaol = kaolinite; Hall = halloysite; Psbm = pseudo boehmite; Zir = zircon; Gibb = gibbsite; MC(I) = intermediate microcline; MC(M) = maximum microcline; Or = orthoclase; Nord = nordstrandite; Mona = monazite; All = allanite; Bay = bayerite; Qtz = quartz; Biot = biotite.
Refe Kaol Kaol Kaol Kaol Kaol Kaol Kaol Kaol Kaol -rence 0.717 0.441 0.419(5) 0.358 0.250 0.233(4) 0.159(6) 0.149(3) 0.437(6) XRD (x) (6) (8) (5) [060] Gibb peaks 0.710 Hall 0.356 Kaol 0.437(5) → (x) 0.442 (x) 0.249 Sample (x) (3) Number ↓ Hall Zir MC(I) Nord Zir Bm Nord Nord Kaol 0.730 0.443 0.422(5) 0.360 0.252 0.235(6) 0.160(1) 0.151(1) 0.441(6) (7) (5) MC(M) (1) (5) Dias Bay Ms Bay Psbm Kaol 0.422(x) All Nord 0.232(5) 0.160(1) 0.150(3) 0.435(7) 0.64- 0.437 Or 0.353 0.248 Qtz Hall Nord 0.69 (6) 0.422(7) (5) (2) 0.154(2) 0.148(3) 0.433(2) Gibb Nord Biot Nord Gibb 0.437 0.422(2) 0.154(8) 0.148(1) (5) Mona Dias 0.432(2) 0.417(3) 0.148(2) Nord 0.416(2)
123 A 0.734 ------0.358 --- 0.233 --- 0.149 --- 0.650
124 A 0.660 ------0.434 --- **
125 A ------0.249 ------0.433 *
126 A ------0.421 0.359 0.251 --- 0.157 ------* shared shared with with Nord Zir 0.360(1) 0.252(5) 215 APPENDIX VIII-E continued.
Refe Kaol Kaol Kaol Kaol Kaol Kaol Kaol Kaol Kaol -rence 0.717 0.441 0.419(5) 0.358 0.250 0.233 0.159(6) 0.149 0.437 XRD (x) (6) (8) (5) (4) (3) (6) peaks 0.710 Hall 0.356 Kaol [060] Gibb → (x) 0.442 (x) 0.249 0.437(5) Sample (x) (3) Number ↓ Hall Zir MC(I) Nord Zir Bm Nord Nord Kaol 0.730 0.443 0.422(5) 0.360 0.252 0.235 0.160(1) 0.151(1) 0.441(6) (7) (5) MC(M) (1) (5) (6) Bay Ms Bay Psbm Kaol 0.422(x) All Nord Dias 0.160(1) 0.150(3) 0.435(7) 0.64- 0.437 Or 0.353 0.248 0.232 Qtz Hall Nord 0.69 (6) 0.422(7) (5) (2) (5) 0.154(2) 0.148(3) 0.433(2) Gibb Nord Biot Nord Gibb 0.437 0.422(2) 0.154(8) 0.148(1) 0.432(2) (5) Mona Dias 0.417(3) 0.148(2) Nord 0.416(2)
123 B 0.650 0.442 0.421 ------0.158 ------**
124 B ------0.419 0.356 ------0.158 ------* * 0.416 * 125 B 0.673 0.437 ------0.250 0.231 ------0.437 * *** ** * *** 0.249 0.432 * * 126 B ------0.417 ------***
300 G 0.646 ------
300 R ------0.250 0.231 0.157 --- 0.436 ** * *** shared with Bay 0.435(7) 301 G ------0.417 ------**
301 R ------0.421 0.360 ------**
304 G ------0.420 ------** 0.417 * 304 R 0.646 --- 0.421 ------***
216 APPENDIX III-F
XRD peaks (nm) indicative of the plagioclase feldspar low albite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
AbL = low albite; Psbm = pseudo boehmite; Bm = boehmite; Nord = nordstrandite; Dias = diaspore; MC(I) = intermediate microcline; Or = orthoclase; Hall = halloysite; Ms = muscovite; All = allanite; Mona = monazite; Qtz = quartz; Biot = biotite; Gibb = gibbsite.
Refe AbL AbL AbL AbL AbL AbL AbL AbL AbL -rence 0.639 0.403 0.378(3) 0.368(2) 0.297(2) 0.322(7) 0.321(6) 0.320 0.244(4) XRD (2) (x,6,2) 0.366 Dias (x,6) Mona peaks (6,3,2) 0.293(3,2) 0.321(1) Bay 0.244(3) → 0.320(3) Sample Number Psbm Nord MC(I) MC(I) Or Or AbL Qtz ↓ 0.64- 0.416(2) 0.380(2) 0.375(4) 0.299(5) 0.324(7) 0.319 0.246(1) 0.69 Dias 0.379(4) 0.374(1) Ms MC(I) (x,6) Biot Bm 0.399(x) Or Hall 0.299(4) 0.324 (x) Ms 0.245(8) 0.611 0.377(8) 0.362(6) MC(I) 0.319(3) Gibb (x) 0.298(3) Gibb 0.245(2) All 0.319(1) Nord 0.292(x) 0.245(1) Dias 0.243(1) Gibb 0.242(2) [004] 123 A --- 0.405 ------0.298 0.321 ------* 0.399 124 A ------0.298 ------
125 A ------0.367 --- 0.323 0.321 ------*** * shared with Or 0.324(7) & MC(I) 0.324(x) 126 A 0.637 0.403 ------0.298 0.323 --- 0.319 0.245 ** 0.295 ** *** * 0.293 shared with Or 0.324(7) & MC(I) 0.324(x) 217 APPENDIX III-F continued.
Refe AbL AbL AbL AbL AbL AbL AbL AbL AbL -rence 0.639(2) 0.403 0.378(3) 0.368(2) 0.297(2) 0.322(7) 0.321 0.320 0.244(4) XRD (x,6,2) 0.366(6,3,2) (6) (x,6) Mona peaks 0.293(3,2) Dias Bay 0.244(3) → 0.321 Sample (1) 0.320(3) Number ↓ Psbm Nord MC(I) MC(I) Or Or AbL Qtz 0.64- 0.416(2) 0.380(2) 0.375(4) 0.299(5) 0.324(7) 0.319 0.246(1) 0.69 Dias 0.379(4) 0.374(1) Ms MC(I) (x,6) Biot Bm 0.399(x) Or Hall 0.299(4) 0.324 Ms 0.245(8) 0.611 0.377(8) 0.362(6) MC(I) (x) Gibb (x) 0.298(3) 0.319(3) 0.245(2) All Gibb Nord 0.292(x) 0.245(1) 0.319(1) Dias 0.243(1) Gibb 0.242(2) [004]
123 B --- 0.401 ------0.298 --- 0.321 --- 0.244 shared * ** *** with Dias 0.399(x) 124 B ------0.378 --- 0.294 ------0.320 0.244 ** 0.292 ** ** 0.243 *** 125 B ------
126 B ------0.371 0.296 ------0.320 0.243 ** ** *** **
300 G ------0.321 --- 0.245 *** *
300 R ------
301 G 0.639 ------0.371 ------0.321 --- 0.243 0.370 ** *
301 R 0.639 --- 0.370 0.297 0.322 --- 0.319 0.244 --- 0.364 ** * * shared with Hall 0.362(6) 304 G ------0.366 0.295 0.322 ------0.244 * ** 304 R ------0.374 ------0.321 --- 0.244 * ** *
218 APPENDIX III-G
XRD peaks (nm) indicative of potassium feldspars orthoclase, intermediate microcline and maximum microcline in Na-saturated, randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
MC(I) = intermediate microcline; MC(M) = maximum microcline; Or = orthoclase; AbL = low albite; Nord = nordstrandite; Mona = monazite; HA = hydroxy apatite; Gibb = gibbsite; Zir = zircon; Biot = biotite; Ms = muscovite; Qtz = quartz; Kaol = kaolinite; All = allanite; Dias = diaspore.
Reference MC(I) MC(I) MC(I) MC(M) MC(I) MC(I) MC(I) XRD 0.375(4) 0.380(2) 0.348(2) 0.326(8) 0.329(x,5) 0.334(5) 0.423(6) peaks 0.374(1) 0.379(4) 0.347(5) 0.325(x,8) MC(M) Qtz 0.422(5) → Or Or 0.329(5) 0.334(x) MC(M) Sample 0.347(5) 0.324(7) Or 0.422(x) Number MC(I) 0.329(6) 0.421(5) ↓ 0.324(x) Or 0.422(7) Nord Mona 0.422(2) Or 0.329(4) AbL Nord AbL 0.329(6) Biot Qtz 0.378(3) 0.390(2) 0.351(1) MC(M) Or 0.337(x) 0.426(4) Or AbL Mona 0.329(5) 0.331(x) Ms Kaol 0.377(8) 0.378(3) 0.351(3) MC(I) Gibb 0.332(x) 0.419(5) AbL HA 0.329(x,5) 0.331(2) 0.368(2) 0.345(4) Mona Zir Nord 0.329(4) 0.330(x) 0.345(1) AbL MC(M) 0.322(7) 0.326(8) 123 A --- 0.382 0.349 0.325 --- 0.335 --- *** *** 124 A ------0.325 0.328 ------0.331 *** 125 A --- 0.381 --- 0.323 ------* *** shared with AbL 0.322(7) 126 A 0.375 0.380 0.348 0.323 0.328 0.333 0.421 * ** * *** * 0.346 shared with shared with AbL 0.322(7) HA 0.345(4) & Nord 0.345(1) 219 APPENDIX III-G continued.
Reference MC(I) MC(I) Or Or Or XRD 0.180(3) 0.216(3) 0.377(8) 0.290(3) 0.331(x) peaks Gibb All → 0.180(1) 0.216(3) Gibb Sample 0.331(2) Number Qtz ↓ Qtz Biot AbL AbL 0.334(x) 0.182(2) 0.218(8) 0.378(3) 0.293(3,2) MC(I) Nord All MC(I) All 0.334(5) 0.178(2) 0.218(4) 0.375(4) 0.292(x) Ms Mona 0.374(1) All 0.332(x) 0.215(3,4) 0.289(3) Qtz Mona Zir 0.213(1) 0.287(7) 0.330(x) Mona Mona MC(I) 0.213(3) 0.286(x) 0.329(x,5) Dias MC(M) 0.213(5) 0.329(5) Or 0.329(6) Mona 0.329(4) 123 A 0.182 0.217 --- 0.291 0.335 * 0.213 *** 0.180 124 A ------0.331 *** 0.328 125 A ------
126 A 0.182 0.215 0.375 0.293 0.333 0.212 0.291 *** * 0.328
220 APPENDIX III-G continued.
Reference MC(I) MC(I) MC(I) MC(M) MC(I) MC(I) MC(I) XRD peaks 0.375(4) 0.380(2) 0.348(2) 0.326(8) 0.329(x,5) 0.334(5) 0.423(6) → 0.374(1) MC(I) 0.347(5) 0.325(x,8) MC(M) Qtz 0.422(5) Sample 0.379(4) Or Or 0.329(5) 0.334(x) MC(M) Number 0.347(5) 0.324(7) Or 0.422(x) ↓ MC(I) 0.329(6) 0.421(5) 0.324(x) Or 0.422(7) Mona Nord 0.329(4) 0.422(2) Or AbL Nord AbL Or 0.331(x) Biot Qtz 0.378(3) 0.390(2) 0.351(1) 0.329(6) Gibb 0.337(x) 0.426(4) Or AbL Mona MC(M) 0.331(2) Ms Kaol 0.377(8) 0.378(3) 0.351(3) 0.329(5) Zir 0.332(x) 0.419(5) AbL HA MC(I) 0.330(x) 0.368(2) 0.345(4) 0.329(x,5) Nord Mona MC(M) 0.345(1) 0.329(4) 0.326(8) 0.325(x,8) AbL Or 0.322(7) 0.324(7) MC(I) 0.324 (x)
123 B 0.374 0.381 ------0.328 --- 0.421 * * ** 124 B 0.378 ------0.325 0.329 --- 0.419 ** *** *** *
125 B ------0.331 ------*** 126 B 0.371 ------0.329 ------** *** shared with AbL 0.368(2)
300 G ------0.348 0.324 0.328 0.334 --- * * ** ***
300 R ------0.331 0.336 --- **
301 G 0.374 ------0.329 ------* ***
301 R 0.374 0.381 ------0.331 --- 0.421 *** **
304 G ------0.331 --- 0.420 *** **
304 R 0.374 ------0.329 --- 0.421 * * ***
221 APPENDIX III-G continued.
Reference MC(I) MC(I) Or Or Or XRD 0.180(3) 0.216(3) 0.377(8) 0.290(3) 0.331(x) peaks Gibb All → 0.180(1) 0.216(3) Gibb Sample 0.331(2) Number ↓ Qtz Biot AbL AbL Qtz 0.182(2) 0.218(8) 0.378(3) 0.293(3,2) 0.334(x) Nord All MC(I) All MC(I) 0.178(2) 0.218(4) 0.375(4) 0.292(x) 0.334(5) Mona 0.374(1) All Ms 0.215(3,4) 0.289(3) 0.332(x) Qtz Mona 0.213(1) 0.287(7) Mona Mona Zir 0.213(3) 0.286(x) 0.330(x) Dias MC(I) 0.213(5) 0.329(x,5) MC(M) 0.329(5) Or 0.329(6) Mona 0.329(4) 123 B 0.181 0.212 0.374 0.291 0.332 * * * * *** 0.179 0.288 0.328* * 124 B 0.181 0.214 0.378 0.294 0.329 0.180 ** 0.292 *** * 125 B --- 0.216 ------0.331 * *** 126 B 0.181 0.214 ------0.329 0.180 * *** **
300 G 0.182 0.216 --- 0.290 0.334 ** 0.212 *** ** 0.328 ** 300 R --- 0.219 ------0.331 * ** 0.215 * 301 G 0.181 0.214 0.374 0.287 0.329 * 0.211 * *** 0.179 ** 301 R 0.181 0.215 0.374 0.287 0.331 0.180 *** 0.177 304 G 0.181 ------0.331 * *** 0.179 304 R 0.181 0.215 0.374 --- 0.332 ** * * *** 0.329* 222 APPENDIX III-H
XRD peaks (nm) indicative of quartz in Na-saturated randomly oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Qtz = quartz; MC(I) = intermediate microcline; Biot = biotite; Ms = muscovite; Gibb = gibbsite; Or = orthoclase; Nord = Nordstrandite; Dias = diaspore; HA = hydroxy apatite; All = allanite; Mona = monazite; Zir = zircon; Kaol = kaolinite; Vc = vermiculite.
Reference Qtz Qtz Qtz Qtz Qtz Qtz XRD 0.334(x) 0.426(4) 0.228(1) 0.182(2) 0.213(1) 0.154(2) peaks MC(I) Mona Biot → 0.334(5) 0.213(3) 0.154(8) Sample Dias Number 0.213(5) ↓ Biot Gibb Dias HA MC(I) Kaol 0.337(x) 0.432(2) 0.232(6) 0.184(5) 0.216(3) 0.159(6) Ms Or Nord Gibb All Vc 0.332(x) 0.422(7) 0.226(4) 0.180(1) 0.216(3) 0.153(7) Or Nord MC(I) Mona 0.331(x) 0.422(2) 0.180(3) 0.215(3,4) Gibb Dias 0.331(2) 0.208(5) Zir 0.207(2)
123 A 0.335 0.428 0.229 0.182 0.213 0.154 *** * * * * 0.180 124 A 0.331 ------0.183 --- 0.155 *** ** * shared with HA 0.184(5) 125 A ------0.184 --- 0.155
126 A 0.333 0.425 0.228 0.182 0.215 0.157 *** ** 0.212 shared with * MC(I) 0.207 0.334(5) & Ms 0.332(x)
223 APPENDIX III-H continued.
Reference Qtz Qtz Qtz Qtz Qtz Qtz XRD 0.334(x) 0.426(4) 0.228(1) 0.182(2) 0.213(1) 0.154(2) peaks MC(I) Mona Biot → 0.334(5) 0.213(3) 0.154(8) Sample Dias Number 0.213(5) ↓ Biot Gibb Dias HA MC(I) Kaol 0.337(x) 0.432(2) 0.232(6) 0.184(5) 0.216(3) 0.159(6) Ms Or Nord Gibb All Vc 0.332(x) 0.422(7) 0.226(4) 0.180(1) 0.216(3) 0.153(7) Or Nord MC(I) Mona 0.331(x) 0.422(2) 0.180(3) 0.215(3,4) Gibb Dias 0.331(2) 0.208(5) Zir 0.207(2)
123 B 0.332 0.228 0.181 0.212 0.158 *** --- 0.227 * * 0.154 shared with * Gibb 0.180(1) & MC(I) 0.180(3) 124 B ------0.226 0.181 0.214 0.158 shared with shared with 0.153 Gibb 0.180(1) Mona & 0.213(3), MC(I) Dias 0.213(5) 0.180(3) & Mona 0.215(3,4)
0.208 125 B 0.331 ------0.216 0.155 *** * *
126 B ------0.226 0.181 0.214 0.156 * shared with * 0.153 Gibb 0.180(1) 0.210 & * MC(I) 0.180(3)
224 APPENDIX III-H continued.
Reference Qtz Qtz Qtz Qtz Qtz Qtz XRD 0.334(x) 0.426(4) 0.228(1) 0.182(2) 0.213(1) 0.154(2) peaks MC(I) Mona Biot → 0.334(5) 0.213(3) 0.154(8) Sample Dias Number 0.213(5) ↓ Biot Gibb Dias HA MC(I) Kaol 0.337(x) 0.432(2) 0.232(6) 0.184(5) 0.216(3) 0.159(6) Ms Or Nord Gibb All Vc 0.332(x) 0.422(7) 0.226(4) 0.180(1) 0.216(3) 0.153(7) Or Nord MC(I) Mona 0.331(x) 0.422(2) 0.180(3) 0.215(3,4) Gibb 0.331(2) Dias 0.208(5) Zir 0.207(2)
300 G 0.334 0.425 0.228 0.182 0.212 0.154 *** ** * ** ** * 0.216
300 R 0.336 ------0.183 0.215 0.157 0.331 * * 0.155 ** shared with *** HA 0.184(5)
301 G ------0.226 0.181 0.214 0.153 * * 0.211 * shared with Gibb 0.180(1) & MC(I) 0.180(3) 301 R 0.331 --- 0.227 0.181 0.215 0.154 *** * shared with 0.212 ** shared with Gibb 0.180(1) * Nord 0.226(4) & MC(I) 0.180(3) 304 G 0.331 --- 0.227 0.181 0.212 0.156 *** shared with * * 0.154 Nord 0.226(4) shared with * Gibb 0.180(1) & MC(I) 0.180(3) 304 R 0.332 --- 0.227 0.181 0.215 0.154 *** * ** * * shared with shared with 0.211 Nord 0.226(4) Gibb 0.180(1) ** & MC(I) 0.180(3)
225 APPENDIX III-I
XRD peaks (nm) indicative of gibbsite, bayerite and nordstrandite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Gibb = gibbsite; Biot = biotite; Ms = muscovite; Nord = Nordstrandite; Bay = bayerite; HA = hydroxy apatite; Zir = zircon; Kaol = kaolinite; All = allanite; Mona = monazite; Dias = diaspore; MC(I) = intermediate microcline; AbL = low albite; Or = orthoclase; Qtz = quartz; Hall = halloysite; Vc-Hb = Vermiculite-hydrobiotite.
Reference Gibb Gibb Gibb Gibb Gibb Bay Bay XRD [002] 0.224(1) 0.192(1) 0.437(5) 0.331(2) 0.222(x) 0.172(4) peaks 0.485(x) Kaol Or → 0.437(6) 0.331(x) Sample Number Biot Nord HA Kaol Qtz Gibb Gibb ↓ 0.5 (weak) 0.226(4) 0.195(3) 0.441(6) 0.334(x) 0.224(1) 0.175(2) Ms Bay Zirc Bay MC(I) Biot Zir 0.497(3) 0.222(x) 0.191(1) 0.435(7) 0.334(5) 0.218(8) 0.175(1) Nord Nord Ms All Mona 0.479(x) 0.190(2) 0.332(x) 0.218(4) 0.174(4) [002] Zir Zir 0.330(x) 0.171(4) Dias 0.171(2) 123 A --- 0.224 0.193 --- 0.335 ------*** 124 A ------0.331 ------*** 125 A ------126 A --- 0.223 ------0.333 0.223 0.173 shared with *** shared with shared Bay 0.222(x) Gibb with 0.224(1) Mona 0.174(4) 0.172
123 B ------0.192 --- 0.332 0.222 0.172 * *** 124 B ------
125 B ------0.437 0.331 ------*** *** 126 B ------0.222 0.175 * 226 APPENDIX III-I continued.
Reference Nord Nord Nord Nord Nord Nord Nord Nord XRD [002] 0.390(2) 0.302(2) 0.226(4) 0.178(2) 0.416(2) 0.360(1) 0.345(1) peaks 0.479 (x) HA → 0.345(4) Sample Number Ms Dias Mona Qtz Gibb MC(M) Hall MC(I) ↓ 0.497(3) 0.399(x) 0.308(8) 0.228(1) 0.180(1) 0.421(5) 0.362(6) 0.348(2) Biot MC(I) Or Gibb MC(I) Kaol Kaol 0.347(5) 0.5(weak) 0.380(2) 0.299(5) 0.224(1) 0.180(3) 0.419(5) 0.358(8) Or Bay 0.379(4) Ms Gibb Mona 0.356(x) 0.347(5) 0.471(9) AbL 0.299(4) 0.175(2) 0.417(3) Vc-Hb Dias 0.378(3) Zir AbL 0.340(4) 0.471(1) 0.175(1) 0.403 (x,6,2)
123 A ------0.229 0.180 --- 0.358 --- * 0.224
124 A ------0.305 ------0.412 --- 0.341 0.304 * ***
125 A 0.481 0.386 ------0.413 --- 0.341 **
126 A --- 0.393 --- 0.228 ------0.359 0.348 0.223 shared * with Kaol 0.346 0.358(8)
123 B ------0.228 0.179 ------0.344 0.227 shared with Gibb 0.180(1) MC(I) 0.180(3) 124 B --- 0.394 --- 0.226 0.181 0.419 0.356 --- ** 0.180 * * * 0.416 * 125 B ------0.304 ------0.342 * ** 0.341 *** 126 B ------0.226 0.181 0.417 ------* 0.180 *** ** 0.175 *
227 APPENDIX III-I continued.
Reference Gibb Bay Nord Bay [001] XRD 0.146(1) 0.435(7) 0.239(4) 0.471(9) peaks Bm Nord Gibb Dias [020] → 0.145(2) 0.433(2) 0.239(2) 0.471(1) Sample Nord Gibb Number 0.144(2) 0.432(2) ↓
Hall Kaol Gibb Nord [002] 0.148(3) 0.437(6) 0.242(2) 0.479(x) Nord Gibb Vc Vc 0.148(1) 0.437(5) 0.238(4) 0.457(6) Dias Qtz 0.148(2) 0.426(4) Bm 0.143(1) [002]
123 A 0.145 --- 0.239 ---
124 A 0.146 0.434 ------* **
125 A --- 0.433 ------*
126 A ------
123 B 0.147 ------shared with Hall 0.148(3) Nord 0.148(1) Dias 0.148(2)
124 B ------
125 B --- 0.432 ------* 126 B ------
228 APPENDIX III-I continued.
Reference Gibb Gibb Gibb Gibb Gibb Bay Bay XRD [002] 0.224(1) 0.192(1) 0.437(5) 0.331(2) 0.222(x) 0.172(4) peaks 0.485(x) Kaol Or → 0.437(6) 0.331(x) Sample Number Biot Nord HA Kaol Qtz Gibb Gibb ↓ 0.5 (weak) 0.226(4) 0.195(3) 0.441(6) 0.334(x) 0.224(1) 0.175(2) Ms Bay Zir Bay MC(I) Biot Zir 0.497(3) 0.222(x) 0.191(1) 0.435(7) 0.334(5) 0.218(8) 0.175(1) Nord Nord Ms All Mona 0.479 (x) 0.190(2) 0.332(x) 0.218(4) 0.174(4) [002] Zir Zir 0.330(x) 0.171(4) Dias 0.171(2)
300 G --- 0.223 ------0.223 --- * * shared with shared with Bay Gibb 0.222(x) 0.224(1) 300 R ------0.436 0.331 --- 0.173 *** ** * shared with shared Bay with 0.435(7) Mona 0.174(4) 301 G ------0.222 --- *
301 R ------0.191 --- 0.331 0.222 0.173 *** * ** shared with Mona 0.174(4) 304 G ------0.331 0.222 --- ***
304 R --- 0.223 ------0.332 0.223 --- * *** * shared with shared with Bay Gibb 0.222(x) 0.224(1)
229 APPENDIX III-I continued.
Reference Nord Nord Nord Nord Nord Nord Nord Nord XRD peaks [002] 0.390(2) 0.302(2) 0.226(4) 0.178(2) 0.416(2) 0.360(1) 0.345(1) → 0.479 (x) HA Sample 0.345(4) Number ↓ Ms Dias Mona Qtz Gibb MC(M) Hall MC(I) 0.497(3) 0.399(x) 0.308(8) 0.228(1) 0.180(1) 0.421(5) 0.362(6) 0.348(2) Biot 0.5 MC(I) Or Gibb MC(I) Kaol Kaol 0.347(5) (weak) 0.380(2) 0.299(5) 0.224(1) 0.180(3) 0.419(5) 0.358(8) Or Bay 0.379(4) Ms Gibb Mona 0.356(x) 0.347(5) 0.471(9) AbL 0.299(4) 0.175(2) 0.417(3) Vc-Hb Dias 0.378(3) Zir AbL 0.340(4) 0.471(1) 0.175(1) 0.403 (x,6,2)
300 G --- 0.394 --- 0.228 ------0.348 0.393 * * 0.223 * 300 R ------0.341 ***
301 G --- 0.390 --- 0.226 0.181 0.417 ------* * ** 0.179 ** 301 R ------0.227 0.181 --- 0.360 0.343 * 0.180 shared 0.177 with Qtz 0.228(1) 304 G ------0.227 0.181 0.420 --- 0.344 shared * ** * with 0.179 0.417 Qtz * 0.228(1) 304 R --- 0.391 --- 0.227 0.181 ------0.345 0.390 * ** shared with Qtz 0.228(1)
0.223 *
230 APPENDIX III-I continued.
Reference Gibb Bay Nord Bay [001] XRD 0.146(1) 0.435(7) 0.239(4) 0.471(9) peaks Bm Nord Gibb Dias [020] → 0.145(2) 0.433(2) 0.239(2) 0.471(1) Sample Nord Gibb Number 0.144(2) 0.432(2) ↓
Hall Kaol Gibb Nord [002] 0.148(3) 0.437(6) 0.242(2) 0.479(x) Nord Gibb Vc Vc 0.148(1) 0.437(5) 0.238(4) 0.457(6) Dias Qtz 0.148(2) 0.426(4) Bm 0.143(1) [002]
300 G ------
300 R --- 0.436 0.240 --- *** shared with Gibb 0.437(5) Kaol 0.437(6)
301 G 0.145 ------
301 R ------
304 G 0.145 ------
304 R 0.145 ------
231 APPENDIX III-J
XRD peaks (nm) indicative of pseudo boehmite and boehmite in Na-saturated randomly- oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold. Reflections attributed to randomly interstratified 2:1 phyllosilicates are shown to help evaluate presence of pseudo boehmite.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Rand. Int. = randomly interstratified phyllosilicates; Psbm = pseudoboehmite; Kaol = kaolinite; AbL = low albite; Bm = boehmite; Biot = biotite; Ms = muscovite; Gibb = gibbsite; HA = hydroxy apatite; Mona = monazite; Zir = zircon; Hall =halloysite; Nord = nordstrandite; Dias = diaspore.
Reference Rand. Psbm Bm Bm Bm Bm Bm Bm XRD peaks Int. 0.64-0.69 0.611 0.316(6) 0.186(3), 0.166(1) 0.145(2) 0.235(6) → [020] 0.185 Gibb Sample (x) [200] (2) 0.146(1) Number Nord ↓ 0.144(2)
Hall AbL AbL Mona Biot Hall Gibb 0.730(7) 0.639(2) 0.319 0.188(3) 0.167(8) 0.148(3) 0.239(2) Kaol Rand. (x,6) HA Zir Nord Nord 0.717(x) Int. (002) Ms 0.184(5) 0.165(1) 0.148(1) 0.239(4) 0.710(x) Biot 0.319(3) Dias Vc AbL 0.5 Gibb 0.148(2) 0.238(4) 0.639(2) (weak) 0.319(1) Bm Vc Bm Ms AbL 0.143(1) 0.237(4) 0.611(x) 0.497(3) 0.315 [002] Hall [020] (5,3) 0.237(1) HA Kaol 0.311(2) 0.233(4)
123 A 1.147 0.734 ------0.167 0.145 0.239 0.650 0.166 0.233 0.594 124 A --- 0.660 ------0.187 --- 0.146 --- ** * shared with Mona 0.188(3) 125 A ------
126 A 1.132 0.637 --- 0.319 0.185 0.167 ------0.586 *** ** 0.166 232 APPENDIX III-J continued.
Reference Rand. Psbm Bm Bm Bm Bm Bm Bm XRD peaks Int. 0.64-0.69 0.611 0.316(6) 0.186(3), 0.166(1) 0.145(2) 0.235(6) → [020] 0.185 Gibb Sample (x) [200] (2) 0.146(1) Number Nord ↓ 0.144(2)
Hall AbL AbL Mona Biot Hall Gibb 0.730(7) 0.639(2) 0.319 0.188(3) 0.167(8) 0.148(3) 0.239(2) Kaol Rand. (x,6) HA Zir Nord Nord 0.717(x) Int. (002) Ms 0.184(5) 0.165(1) 0.148(1) 0.239(4) 0.710(x) Biot 0.319(3) Dias Vc AbL 0.5 Gibb 0.148(2) 0.238(4) 0.639(2) (weak) 0.319(1) Bm Vc Bm Ms AbL 0.143(1) 0.237(4) 0.611(x) 0.497(3) 0.315 [002] Hall [020] (5,3) 0.237(1) HA Kaol 0.311(2) 0.233(4)
123 B --- 0.650 --- 0.316 0.187 0.166 ------0.625 ** * 0.165 shared with Mona 0.188(3) 124 B --- 0.623 --- 0.320 ------** 0.315 * 0.313 * 125 B --- 0.673 ------*
126 B --- 0.628 --- 0.320 ------***
300 G 1.186 0.646 ------0.186 ------*
300 R ------
301 G 1.132 0.639 --- 0.316 --- 0.166 0.145 --- 1.111 0.632 *
301 R --- 0.639 --- 0.319 --- 0.166 ------*
304 G 1.125 ------0.316 0.185 0.166 0.145 --- 1.115 * 0.165
304 R 1.111 0.646 --- 0.316 --- 0.165 0.145 --- * *
233 APPENDIX III-K
XRD peaks (nm) indicative of diaspore in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Dias = diaspore; AbL = low albite; Nord = nordstrandite; Mona = monazite; Gibb = gibbsite; Qtz = quartz; Zir = zircon; Kaol = kaolinite; Vc = vermiculite; Bay = bayerite.
Reference Dias Dias Dias Dias Dias Dias XRD 0.399(x) 0.243(1) 0.208(5) 0.232(5) 0.471(1) 0.321(1) peaks [020] AbL → Bay 0.321(6) Sample 0.471(9) Number [001] ↓
AbL AbL Dias Kaol Nord AbL 0.403(x,6,2) 0.244(4) 0.213(5) 0.233(4) 0.479 (x) 0.322(7) Nord Mona Qtz Qtz [002] AbL 0.390(2) 0.244(3) 0.213(1) 0.228(1) Vc 0.320 (x,6) Gibb Mona 0.457(6) Bay 0.242(2) 0.213(3) 0.320(3) [004] Zir 0.207(2)
123 A 0.405 ------0.233 --- 0.321 0.399 0.229 * 124 A ------
125 A 0.395 ------0.321 0.386 *
126 A 0.403 --- 0.212 0.228 ------** * 0.207
234 APPENDIX III-K continued.
Reference Dias Dias Dias Dias Dias Dias XRD 0.399(x) 0.243(1) 0.208(5) 0.232(5) 0.471(1) 0.321(1) peaks [020] AbL → Bay 0.321(6) Sample 0.471(9) Number [001] ↓
AbL AbL Dias Kaol Nord AbL 0.403(x,6,2) 0.244(4) 0.213(5) 0.233(4) 0.479(x) 0.322(7) Nord Mona Qtz Qtz [002] AbL 0.390(2) 0.244(3) 0.213(1) 0.228(1) Vc 0.320 (x,6) Gibb Mona 0.457(6) Bay 0.242(2) 0.213(3) 0.320(3) [004] Zir 0.207(2)
123 0.401 0.244 --- 0.228 --- 0.321 B shared with *** ** AbL 0.403(x,6,2)
124 0.394 0.243 0.214 ------0.320 B ** *** 0.208 ** 0.244 ** 125 ------0.231 ------B *
126 0.395 0.243 0.214 ------0.320 B * ** * *** 0.210 *
300 0.394 ------0.228 --- 0.321 G 0.393 * ***
300 ------0.231 ------R *
301 --- 0.243 ------0.321 G * **
301 --- 0.244 --- 0.227 --- 0.322 R * * **
304 --- 0.244 --- 0.227 --- 0.322 G **
304 0.244 --- 0.227 --- 0.321 R --- * * **
235 APPENDIX III-L
XRD peaks (nm) indicative of hydroxy apatite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
HA = hydroxy apatite; AbL = low albite; Mona = monazite; Vc-Hb = vermiculite-hydrobiotite; All = allanite; Biot = biotite; Vc = vermiculite; Nord = nordstrandite; MC(I) = intermediate microcline; Or = orthoclase.
Reference HA HA HA HA HA XRD 0.311(2) 0.283(x) 0.273(8) 0.263(2) 0.345(4) peaks 0.278(3) All Nord → 0.263(4) 0.345(1) Sample Number ↓ AbL Mona Vc-Hb Biot MC(I) 0.315(5,3) 0.286(x) 0.275(2) 0.266(8) 0.348(2) Mona Vc-Hb All Vc 0.347(5) 0.309(x) 0.275(2) 0.271(7) 0.262(5) Or Vc 0.347(5) 0.260(4) Vc-Hb 0.340(4)
123 A --- 0.277 --- 0.265 ---
124 A ------0.261 0.341 * ***
125 A ------0.341 **
126 A --- 0.284 --- 0.263 0.348 0.277 0.259 * 0.276 0.346
236 APPENDIX III-L continued.
Reference HA HA HA HA HA XRD 0.311(2) 0.283(x) 0.273(8) 0.263(2) 0.345(4) peaks 0.278(3) All Nord → 0.263(4) 0.345(1) Sample Number ↓ AbL Mona Vc-Hb Biot MC(I) 0.315(5,3) 0.286(x) 0.275(2) 0.266(8) 0.348(2) Mona Vc-Hb All Vc 0.347(5) 0.309(x) 0.275(2) 0.271(7) 0.262(5) Or Vc 0.347(5) 0.260(4) Vc-Hb 0.340(4)
123 B ------0.344
124 B 0.313 ------* 0.315 * 125 B ------0.260 0.342 ** ** 0.341 *** 126 B ------
300 G --- 0.277 ------0.348 *
300 R ------0.341 ***
301 G ------
301 R ------0.343
304 G ------0.275 --- 0.344 *
304 R --- 0.284 ------0.345
237 APPENDIX III-M
XRD peaks (nm) indicative of monazite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Mona = monazite; HA = hydroxy apatite; Nord = nordstrandite; All = allanite; Ms = muscovite; Gibb = gibbsite; Zir = zircon; Bay = bayerite; Kaol = kaolinite; AbL = low albite.
Reference Mona Mona Mona Mona Mona XRD peaks 0.309(x) 0.287(7) 0.196(5,3) 0.174(4) 0.417(3) → 0.308(8) 0.286(x) Sample Number ↓ HA All Ms Gibb Kaol 0.311(2) 0.289(3) 0.199(5) 0.175(2) 0.419(5) Nord HA Gibb Zir Nord 0.302(2) 0.283(x) 0.199(1) 0.175(1) 0.416(2) HA Bay AbL 0.195(3) 0.172(4) 0.403 (x,6,2)
123 A ------
124 A 0.305 ------0.412 0.304 *
125 A 0.307 ------0.413
126 A ------0.197 0.173 --- 0.172
238 APPENDIX III-M continued.
Reference Mona Mona Mona Mona Mona XRD 0.309(x) 0.287(7) 0.196(5,3) 0.174(4) 0.417(3) peaks 0.308(8) 0.286(x) → Sample Number ↓ HA All Ms Gibb Kaol 0.311(2) 0.289(3) 0.199(5) 0.175(2) 0.419(5) Nord HA Gibb Zir Nord 0.302(2) 0.283(x) 0.199(1) 0.175(1) 0.416(2) HA Bay AbL 0.195(3) 0.172(4) 0.403 (x,6,2)
123 B --- 0.288 0.197 0.172 --- * * shared with All 0.289(3) 124 B ------0.419 * 0.416 * 125 B 0.307 ------*
126 B ------0.196 0.175 0.417 ** * ***
300 G ------
300 R ------0.173 --- *
301 G --- 0.287 0.197 --- 0.417 **
301 R --- 0.287 0.197 0.173 --- * **
304 G ------0.197 --- 0.420 * ** 0.417 * 304 R ------0.197 ------*
239 APPENDIX III-N
XRD peaks (nm) indicative of allanite in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 -75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
All = allanite; AbL = low albite; Or = orthoclase; Mona = monazite; HA = hydroxy apatite; Biot = biotite; Kaol = kaolinite.
Reference All All All All All XRD 0.292(x) 0.289(3) 0.271(7) 0.353(5) 0.216(3) peaks MC(I) → 0.216(3) Sample Number AbL Or HA Kaol Biot ↓ 0.297(2) 0.290(3) 0.273(8) 0.356(x) 0.218(8) AbL Mona Biot AbL All 0.293(3,2) 0.287(7) 0.266(8) 0.351(1) 0.218(4) Or Mona Mona 0.290(3) 0.351(3) 0.215(3,4) Qtz 0.213(1) Mona 0.213(3) Dias 0.213(5) 123 A 0.291 ------0.217 shared with 0.213 Or 0.290(3) 124 A ------
125 A ------0.353 ---
126 A 0.293 ------0.215 0.291 0.212 shared with * Or 0.290(3)
123 B 0.291 0.288 ------0.212 * * * shared with shared with Or 0.290(3) Mona 0.287(7) 124 B 0.294 ------0.214 0.292 125 B ------0.216 * 126 B ------0.214 * 240 APPENDIX III-N continued.
Refe All All All All All Reference 0.292(x) 0.289(3) 0.271(7) 0.353(5) 0.216(3) XRD MC(I) peaks 0.216(3) → Sample AbL Or HA Kaol Biot Number 0.297(2) 0.290(3) 0.273(8) 0.356(x) 0.218(8) ↓ AbL Mona Biot AbL All 0.293(3,2) 0.287(7) 0.266(8) 0.351(1) 0.218(4) Or Mona Mona 0.290(3) 0.351(3) 0.215(3,4) Qtz 0.213(1) Mona 0.213(3) Dias 0.213(5)
300 G 0.290 ------0.216 0.212 **
300 R ------0.219 * 0.215 * 301 G ------0.214 0.211
301 R ------0.215
304 G ------
304 R ------0.215 *
241 APPENDIX III-O
XRD peaks (nm) indicative of zircon in Na-saturated randomly-oriented powder mounts of the sand-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Zir = zircon; Hall = halloysite; Kaol = kaolinite; Ms = muscovite; Or = orthoclase; Gibb = gibbsite; MC(I) = intermediate microcline; MC(M) = maximum microcline; Mona = monazite; Vc = vermiculite; Dias = diaspore; Nord = nordstrandite; Bay = bayerite; Biot = biotite; Bm = boehmite.
Reference Zir Zir Zir Zir Zir Zir Zir Zir XRD 0.443(5) 0.330(x) 0.252(5) 0.207(2) 0.191(1) 0.175(1) 0.171(4) 0.165(1) peaks Gibb Dias → 0.175(2) 0.171(2) Sample Number Hall Ms Vc Dias Gibb Nord Bay Biot ↓ 0.445 0.332(x) 0.253(5) 0.208(5) 0.192(1) 0.178(2) 0.172(4) 0.167(8) Hall Or Kaol Gibb Nord Mona Gibb Bm 0.442(x) 0.331(x) 0.250(5) 0.204(2) 0.190(2) 0.174(4) 0.169(1) 0.166(1) Kaol Gibb Kaol Hall Dias 0.441(6) 0.331(2) 0.249(3) 0.168(2) 0.163(4) MC(I) Kaol 0.329(x,5) 0.162(7) MC(M) 0.329(5) Or 0.329(6) Mona 0.329(4)
123 A ------0.193 ------0.167 0.189 0.166 0.162 124 A --- 0.331 ------***
125 A ------0.249 ------0.170 ---
126 A --- 0.333 0.251 0.207 --- 0.173 0.173 0.167 *** shared 0.172 0.172 0.166 with kaol 0.250(5) 242 APPENDIX III-O continued.
Reference Zir Zir Zir Zir Zir Zir Zir Zir XRD 0.443(5) 0.330(x) 0.252(5) 0.207(2) 0.191(1) 0.175(1) 0.171(4) 0.165(1) peaks Gibb Dias → 0.175(2) 0.171(2) Sample Number Hall Ms Vc Dias Gibb Nord Bay Biot ↓ 0.445 0.332(x) 0.253(5) 0.208(5) 0.192(1) 0.178(2) 0.172(4) 0.167(8) Hall Or Kaol Gibb Nord Mona Gibb Bm 0.442(x) 0.331(x) 0.250(5) 0.204(2) 0.190(2) 0.174(4) 0.169(1) 0.166(1) Kaol Gibb Kaol Hall Dias 0.441(6) 0.331(2) 0.249(3) 0.168(2) 0.163(4) MC(I) Kaol 0.329(x,5) 0.162(7) MC(M) 0.329(5) Or 0..329(6) Mona 0.329(4)
123 B 0.442 0.332 ------0.192 0.179 0.172 0.166 *** * 0.172 0.165
124 B --- 0.329 --- 0.208 ------***
125 B --- 0.331 0.250 ------*** ** 0.249 * 126 B --- 0.329 0.252 0.210 --- 0.175 ------*** * * *
300 G ------0.167 * 300 R --- 0.331 0.250 ------0.173 0.173 0.167 ** ** * * * 0.168 0.164 0.169 shared with Dias 0.163(4) 301 G --- 0.329 ------0.179 --- 0.166 *** ** * 301 R --- 0.331 ------0.191 0.177 0.173 0.166 *** 0.173 ** ** 304 G --- 0.331 ------0.179 --- 0.166 *** 0.165 304 R --- 0.332 0.253 ------0.167 *** * * 0.165
243 APPENDIX IV
X-RAY DIFFRACTION DATA FOR THE SILT-SIZED FRACTION APPENDIX IV-A X-ray diffractograms of Na-saturated, randomly-oriented specimens of the silt-sized fraction of saprolite at 25oC.
600
500 126A
400
125A
300 intensity
124A 200
100 123A
0 0 10203040506070 degrees 2 theta
244 APPENDIX IV-A continued
600
500
126B
400
125B
300 intensity
124B 200
100
123B
0 0 10203040506070 degrees 2 theta
245 APPENDIX IV-A continued
600
304R
500
304G
400
301R
300 intensity
301G
200
300R
100
300G 0 0 10203040506070 degrees 2 theta
246 APPENDIX IV-B
XRD peaks (nm) indicative of muscovite and biotite detected in Na-saturated randomly oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50-75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Biot = biotite; Ms = muscovite; Vc-Hb = vermiculite-hydrobiotite; Qtz = quartz; MC(I) = Intermediate microcline: All = Allanite; HA = hydroxy apatite; Bay = Bayerite; Or = orthoclase; Gibb = gibbsite; Hall = halloysite; Bm = boehmite; Zir = zircon; Kaol = kaolinite; Vc = vermiculite; Nord = nordstrandite.
Refe Biot Biot Biot Biot Biot Biot Biot Ms Ms -rence 1.01 0.5 0.337(x) 0.266(8) 0.218(8) 0.167(8) 0.154(8) 0.332(x) 0.150(3) XRD (x) (weak) All Qtz peaks Ms Ms 0.218(4) 0.154(2) → 0.995 0.497(3) Sample (x) Number ↓ Vc-Hb All Bay Gibb Kaol Qtz Nord 0.340(4) 0.271(7) 0.222(x) 0.169(1) 0.159(6) 0.334(x) 0.151(1) Qtz HA MC(I) Hall Vc MC(I) Kaol 0.334(x) 0.263(2) 0.216(3) 0.168(2) 0.153(7) 0.334(5) 0.149(3) MC(I) All Bm Or 0.334(5) 0.263(4) 0.166(1) 0.331(x) Zir Gibb 0.165(1) 0.331(2)
123 A ------0.335 0.268 ------0.331 0.149 * * * 124 A 0.955 ------0.331 ---
125 A 0.966 ------0.155 0.331 0.149 * --- ** * 126 A ------0.333 ------0.168 --- 0.333 --- ** **
247 APPENDIX IV-B continued.
Reference Biot Biot Biot Biot Biot Biot Biot Ms Ms XRD 1.01(x) 0.5 0.337(x) 0.266(8) 0.218(8) 0.167(8) 0.154(8) 0.332(x) 0.150(3) peaks Ms (weak) All Qtz → 0.995(x) Ms 0.218(4) 0.154(2) Sample 0.497(3) Number ↓ Vc-Hb All Bay Gibb Kaol Qtz Nord 0.340(4) 0.271(7) 0.222(x) 0.169(1) 0.159(6) 0.334(x) 0.151(1) Qtz HA MC(I) Hall Vc MC(I) Kaol 0.334(x) 0.263(2) 0.216(3) 0.168(2) 0.153(7) 0.334(5) 0.149(3) MC(I) All Bm Or 0.334(5) 0.263(4) 0.166(1) 0.331(x) Zir Gibb 0.165(1) 0.331(2)
123 B --- 0.499 0.334 ------0.334 --- 0.498 * *
124 B 0.955 ------0.167 ------
125 B 0.960 0.492 ------
126 B 1.010 0.501 0.334 ------0.334 --- * *** ***
300 G ------0.167 --- 0.332 --- ***
300 R ------0.342 ------0.166 ------
301 G ------
301 R ------0.340 ------0.168 --- 0.334 --- *** * 0.334 * 304 G ------0.218 0.166 0.153 0.331 0.149 * * ** *
304 R ------0.341 ------**
248 APPENDIX IV-C
XRD peaks (nm) indicative of 2:1 phyllosilicates (excluding muscovite and biotite) detected in Na-saturated randomly oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Reg. Int. = muscovite and or biotite regularly interstratified with vermiculite and or HIV; Rand. Int. = muscovite and or biotite randomly interstratified with vermiculite and or HIV; Vc-Hb = vermiculite-hydrobiotite; HA = hydroxy apatite; Nord = Nordstrandite; Biot = biotite; Vc = vermiculite; Bay = Bayerite; Dias = Diaspore; All = Allanite; Ms = muscovite; Kaol = Kaolinite; Zir = Zircon.
Reference Reg. Vc-Hb Vc-Hb Vc-Hb Rand. (002) Vc Vc Vc Vc XRD Int. 0.450(6) 0.340(4) 0.275(2) Int. of 1.4 0.457(6) 0.262(5) 0.253(5) peaks Rand. HIV 0.260(4) → Int. 1.4 Sample Number HA HA Bay HA Kaol ↓ 0.345(4) 0.278(3) 0.263(2) 0.255(3) Nord HA 0.471(9) All Zir 0.345(1) 0.273(8) Dias 0.263(4) 0.252(5) Biot 0.471(1) Ms 0.337(x) Vc-Hb 0.257(6) 0.450(6) Vc 0.257(5)
123 A ------1.104 ------1.084
124 A ------1.097 ------
125 A ------0.254 ** shared with Kaol 0.255(3) 126 A ------1.125 ------**
249 APPENDIX IV-C continued.
Reference Reg. Vc-Hb Vc-Hb Vc-Hb Rand. (002) Vc Vc Vc Vc XRD Int. 0.450(6) 0.340(4) 0.275(2) Int. of 1.4 0.457(6) 0.262(5) 0.253(5) peaks Rand. HIV 0.260(4) → Int. 1.4 Sample Number HA HA Bay HA Kaol ↓ 0.345(4) 0.278(3) 0.263(2) 0.255(3) Nord HA 0.471(9) All Zir 0.345(1) 0.273(8) Dias 0.263(4) 0.252(5) Biot 0.471(1) Ms 0.337(x) Vc-Hb 0.257(6) 0.450(6) Vc 0.257(5)
123 B ------1.170 ------
124 B ------
125 B ------0.253
126 B ------0.586 ------0.569 0.547 0.527
300 G ------0.261 ---
300 R ------0.342 --- 1.10 ------**
301 G ------1.071 ------*
301 R ------0.340 --- 1.21 ------0.456 0.259 --- *** * *
304 G ------0.274 1.14 ------0.259 0.254 *** * ** ** shared 1.12 shared with HA * with 0.273(8) 1.10 Kaol * 0.255(3) 304 R ------0.341 --- 1.11 ------0.255 ** * * 1.09 0.254 * *
250 APPENDIX IV-D
XRD peaks (nm) indicative of halloysite in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Hall = halloysite; Vc-Hb = vermiculite-hydrobiotite; Zir = zircon; AbL = albite low; Nord = nordstrandite; Bm = boehmite; Kaol = kaolinite; Gibb = gibbsite.
Reference Hall Hall Hall Hall Hall XRD peaks 0.730(7) 0.445 0.362(6) 0.237(1) 0.442(x) → Vc 0.237(4) Kaol Sample 0.441(6) Number Vc ↓ Vc-Hb AbL 0.238(4) Zir 0.450(6) 0.366 (6,3,2) Bm 0.443(5) Zir Nord 0.235(6) Kaol 0.443(5) 0.360(1) 0.437(6) Gibb 0.437(5)
123 A ------
124 A ------0.439 *** shared with Kaol 0.437(6) & gibb 0.437(5)
125 A ------
126 A 0.737 --- 0.364 0.236 0.442 *** * shared with Bm *** shared with AbL 0.235(6) 0.366(6,3,2)
251 APPENDIX IV-D continued.
Reference Hall Hall Hall Hall Hall XRD peaks 0.730(7) 0.445 0.362(6) 0.237(1) 0.442(x) → Vc 0.237(4) Kaol Sample 0.441(6) Number ↓ Vc Vc-Hb AbL 0.238(4) Zir 0.450(6) 0.366 Bm 0.443(5) Zir (6,3,2) 0.235(6) Kaol 0.443(5) Nord 0.437(6) 0.360(1) Gibb 0.437(5)
123 B 0.743 0.445 ------0.440 *** *** ** 0.740 0.444 *** *** 0.731 shared with Zir *** 0.443(5)
124 B ------0.362 0.236 --- ** shared with Bm 0.360 0.235(6) *
125 B ------0.236 --- shared with Bm 0.235(6)
126 B 0.737 0.444 0.364 ------*** *** * shared with shared with AbL Zirc 0.443(5) 0.366(6,3,2)
300 G ------
300 R ------
301 G ------
301 R 0.752 --- 0.364 ------* shared with 0.743 AbL * 0.366(6,3,2) 304 G ------0.238 --- 0.237
304 R ------
252 APPENDIX IV-E
XRD peaks (nm) indicative of kaolinite in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Kaol = kaolinite; Hall = halloysite; Psbm = pseudo boehmite; Zir = zircon; Gibb = gibbsite; Or = orthoclase; Nord = nordstrandite; Mona = monazite; All = allanite; AbL = albite low.
Reference Kaol Kaol Kaol Kaol Kaol Kaol XRD peaks 0.717(x) 0.441(6) 0.419(5) 0.358(8) 0.159(6) 0.437(6) → 0.710(x) Hall 0.356(x) Gibb Sample 0.442(x) 0.437(5) Number ↓ Hall Zir Or Nord Bay Kaol 0.730(7) 0.443(5) 0.422(7) 0.360(1) 0.160(1) 0.441(6) Psbm Kaol Nord All Nord Bay 0.435(7) 0.64-0.69 0.437(6) 0.422(2) 0.353(5) 0.160(1) Gibb Mona AbL Qtz 0.437(5) 0.417(3) 0.351(1) 0.154(2) Mona Biot 0.351(3) 0.154(8)
123 A 0.713 ------0.353 --- 0.438 *** ** ***
124 A 0.713 0.439 0.420 0.353 --- 0.439 *** *** ** *** shared with shared with Kaol Kaol 0.441(6) 0.437(6) & gibb 0.437(5)
125 A 0.707 --- 0.418 0.354 0.155 0.438 *** ** ** *** shared with mona 0.417(3)
126 A --- 0.442 0.420 0.355 --- 0.442 *** * * *** 0.436 ** 253 APPENDIX IV-E continued.
Reference Kaol Kaol Kaol Kaol Kaol Kaol XRD peaks 0.717(x) 0.441(6) 0.419(5) 0.358(8) 0.159(6) 0.437(6) → 0.710(x) Hall 0.356(x) Gibb Sample 0.442(x) 0.437(5) Number ↓ Hall Zir Or Nord Bay Kaol 0.730(7) 0.443(5) 0.422(7) 0.360(1) 0.160(1) 0.441(6) Psbm Kaol Nord All Nord Bay 0.64-0.69 0.437(6) 0.422(2) 0.353(5) 0.160(1) 0.435(7) Gibb Mona AbL Qtz 0.437(5) 0.417(3) 0.351(1) 0.154(2) Mona Biot 0.351(3) 0.154(8)
123 B --- 0.440 ------0.440 ** ** 124 B 0.719 ------0.360 --- 0.437 ** * *** 0.702 0.356 ** 0.354
125 B 0.708 ------0.352 --- 0.437 ** * ** 126 B ------0.356 ------*
300 G 0.713 --- 0.418 0.357 --- 0.434 *** *** ** *** 0.702 shared with *** Mona 0.417(3)
300 R 0.710 --- 0.418 ------** shared with Mona 0.417(3)
301 G ------
301 R ------0.353 --- 0.435 * * 304 G 0.713 --- 0.418 0.357 --- 0.435 *** ** ** *** 0.708 shared with *** Mona 0.705 0.417(3) ***
304 R 0.705 ------* 0.699 *
254 APPENDIX IV-F
XRD peaks (nm) indicative of the plagioclase feldspar low albite in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
AbL = low albite; Psbm = pseudo boehmite; Bm = boehmite; Nord = nordstrandite; Dias = diaspore; MC(I) intermediate microcline; Hall = halloysite; Or = orthoclase; Bay = bayerite; Ms = muscovite; Gibb = gibbsite; HA = hydroxy apatite.
Reference AbL AbL AbL AbL AbL AbL AbL AbL AbL XRD 0.639(2) 0.403 0.368(2) 0.322(7) 0.321(6) 0.320 0.319 0.315 0.297 peaks (x,6,2) 0.366(6,3,2) Dias (x,6) (x,6) (5,3) (2) → 0.321(1) Bay Ms AbL Sample 0.320(3) 0.319(3) 0.293 Number Gibb (3,2) ↓ 0.319(1)
Psbm Nord MC(I) MC(I) Bm MC(I) 0.64- 0.416(2) 0.374(1) 0.324(x) 0.316(6) 0.298 0.69 Dias Hall Or HA (3) Bm 0.399(x) 0.362(6) 0.324(7) 0.311(2) All [020] 0.292 0.611(x) (x) 123 A ------0.320 --- 0.315 0.296 * *** ** 0.312 * 124 A ------0.315 --- *** 125 A ------0.370 ------0.320 --- 0.316 --- * *** 126 A --- 0.402 0.364 ------0.320 --- 0.315 --- * *** ** shared with Hall 0.362(6)
255 APPENDIX IV-F continued.
Reference AbL AbL AbL AbL AbL AbL AbL AbL AbL XRD 0.639(2) 0.403 0.368(2) 0.322(7) 0.321(6) 0.320 0.319 0.315 0.297 peaks (x,6,2) 0.366(6,3,2) Dias (x,6) (x,6) (5,3) (2) → 0.321(1) Bay Ms AbL Sample 0.320(3) 0.319(3) 0.293 Number Gibb (3,2) ↓ 0.319(1)
Psbm Nord MC(I) MC(I) Bm MC(I) 0.64- 0.416(2) 0.374(1) 0.324(x) 0.316(6) 0.298(3) 0.69 Dias Hall Or HA All Bm 0.399(x) 0.362(6) 0.324(7) 0.311(2) 0.292(x) [020] 0.611(x) 123 B --- 0.404 0.365 --- 0.321 --- 0.318 --- 0.293 * ** *** *** 124 B --- 0.400 0.362 ------0.314 0.297 0.397 ** *** ** 0.311 0.395 *** ** 125 B ------0.370 ------0.316 --- *** 126 B --- 0.403 0.364 --- 0.321 ------0.316 0.293 ** * *** ** ** shared with Hall 0.362(6)
300 G --- 0.408 --- 0.322 ------0.296 **
300 R 0.632 --- 0.365 --- 0.321 ------0.298 ***
301 G ------0.319 ------*** 0.318 *** 301 R --- 0.404 0.364 0.323 ------0.298 shared with * ** Hall shared 0.294 0.362(6) with * MC(I) 0.324(x) & Or 0.324(7) 304 G ------0.370 --- 0.321 ------0.313 0.296 * *** 304 R ------0.370 0.323 --- 0.320 ------0.295 * *** * shared with MC(I) 0.324(x) & Or 0.324(7)
256 APPENDIX IV-G
XRD peaks (nm) indicative of the potassium feldspars orthoclase, intermediate microcline and maximum microcline in Na-saturated randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
MC(I) = intermediate microcline; MC(M) = maximum microcline; Or = orthoclase; Nord = nordstrandite ; Qtz = quartz; Kaol = kaolinite; AbL = low albite; Mona = monazite; HA = hydroxy apatite; Biot = biotite; Ms = muscovite; Zir = zircon; All = allanite; Dias = diaspore.
Refe MC(I) MC(I) MC(I) MC(M) MC(I) MC(I) MC(I) -rence 0.380(2) 0.375(4) 0.348(2) 0.326(8) 0.329(x,5) 0.423(6) 0.334(5) XRD peaks 0.379(4) 0.374(1) 0.347(5) 0.325(x,8) MC(M) 0.422(5) Qtz → Or MC(I) 0.329(5) MC(M) 0.334(x) Sample 0.347(5) 0.324(x) Or 0.422(x) Number Or 0.329(6) 0.421(5) ↓ 0.324(7) Or Mona 0.422(7) 0.329(4) Nord 0.422(2)
Nord Or AbL MC(I) Qtz Biot 0.390(2) 0.377(8) 0.351(1) 0.329(x,5) Zir 0.426(4) 0.337(x) AbL AbL Mona MC(M) 0.330(x) Kaol Ms 0.378(3) 0.368(2) 0.351(3) 0.329(5) MC(M) 0.419(5) 0.332(x) Or HA Or 0.326(8) 0.377(8) 0.345(4) 0.329(6) 0.325(x,8) Nord Mona MC(I) 0.345(1) 0.329(4) 0.324(x) AbL Or 0.322(7) 0.324(7)
123 A ------0.328 --- 0.335 * * 124 A --- 0.372 ------0.420 ---
125 A ------
126 A --- 0.376 ------0.420 0.333 * * ** shared with Or 0.377(8) 257 APPENDIX IV-G continued.
Reference MC(I) MC(I) Or Or Or Or XRD peaks 0.216(3) 0.180(3) 0.377(8) 0.331 0.299 0.290(3) → All Gibb (x) (5) Sample 0.216(3) 0.180(1) Ms Number Gibb 0.299 ↓ 0.331(2) (4)
Biot Qtz AbL Ms Nord All 0.218(8) 0.182(2) 0.378(3) 0.332 0.302 0.292(x) All Nord MC(I) (x) (2) All 0.218(4) 0.178(2) 0.375(4) Zir MC(I) 0.289(3) 0.374(1) 0.330 0.298 Mona Mona (x) (3) 0.287(7) 0.215(3,4) Mona Qtz 0.286(x) 0.213(1) Mona 0.213(3) Dias 0.213(5)
123 A --- 0.179 --- 0.331 --- 0.287 ** * * 0.177 ** 124 A ------0.331 ------
125 A 0.212 0.182 --- 0.331 --- 0.290 * **
126 A 0.215 0.180 0.376 ------* shared with MC(I) 0.375(4)
258 APPENDIX IV-G continued.
Reference MC(I) MC(I) MC(I) MC(M) MC(I) MC(I) MC(I) XRD peaks 0.380(2) 0.375(4) 0.348(2) 0.326(8) 0.329(x,5) 0.423(6) 0.334(5) → 0.379(4) 0.374(1) 0.347(5) 0.325(x,8) MC(M) 0.422(5) Qtz Sample Or MC(I) 0.329(5) MC(M) 0.334(x) Number 0.347(5) 0.324(x) Or 0.422(x) ↓ Or 0.329(6) 0.421(5) 0.324(7) Mona Or 0.329(4) 0.422(7) Nord 0.422(2)
Nord Or AbL MC(I) Zir Qtz Biot 0.390(2) 0.377(8) 0.351(1) 0.329(x,5) 0.330(x) 0.426(4) 0.337(x) AbL AbL Mona MC(M) MC(M) Kaol Ms 0.378(3) 0.368(2 0.351(3) 0.329(5) 0.326(8) 0.419(5) 0.332(x) Or HA Or 0.325(x,8) 0.377(8) 0.345(4) 0.329(6) MC(I) Nord Mona 0.324(x) 0.345(1) 0.329(4) Or AbL 0.324(7) 0.322(7) 123 B 0.387 --- 0.348 ------0.334 ** ** * 0.377 * 124 B --- 0.375 ------0.330** ------Shared with Or 0.331(x) 125 B ------0.330* ------Shared with Or 0.331(x) 126 B ------0.425 0.334 ***
300 G 0.390 0.375 0.348 0.326 0.330** 0.422 0.332 * * * 0.332 ** *** *** 300 R ------0.325 0.330*** ------* Shared with Or 0.331(x) 301 G ------0.328* ------
301 R 0.386 ------0.323 0.329 --- 0.334 ** * *** * shared with AbL 0.322(7)
304 G 0.389 ------0.325 0.331 ------* * *** 304 R 0.389 ------0.323 0.329 ------* ** shared with AbL 0.322(7)
259 APPENDIX IV-G continued.
Reference MC(I) MC(I) Or Or Or Or XRD peaks 0.216(3) 0.180(3) 0.377(8) 0.331(x) 0.299(5) 0.290(3) → All Gibb Ms Sample 0.216(3) 0.180(1) 0.299(4) Number Gibb ↓ 0.331(2)
Biot Qtz AbL Qtz Nord All 0.218(8) 0.182(2) 0.378(3) 0.334(x) 0.302 0.292(x) All Nord MC(I) MC(I) (2) All 0.218(4) 0.178(2) 0.375(4) 0.334(5) MC(I) 0.289(3) 0.374(1 0.298 Mona Mona Ms (3) 0.287(7) 0.215 0.332 Mona (3,4) (x) 0.286(x) Qtz Zir 0.213(1) 0.330 Mona (x) 0.213(3) Dias 0.213(5)
123 B --- 0.178 0.377 ------** *
124 B ------0.330 ** --- 0.291 Shared with MC(I)0.329(x,5) MC(M)0.329(5) Or 0.329(6) 125 B ------0.330* --- 0.291 Shared with 0.286 MC(I)0.329(x,5) MC(M)0.329(5) Or 0.329(6) 126 B ------0.299 0.285 *
300 G ------0.332 --- 0.288 *** * 0.330 **
300 R 0.214 ------0.330 *** 0.298 0.287 ** Shared with MC(I)0.329(x,5) MC(M)0.329(5) Or 0.329(6) 301 G 0.214 0.180 --- 0.328 --- 0.285 ** * 301 R ------0.329 0.298 --- *** ** 304 G 0.218 0.181 --- 0.331 --- 0.285 * * ** 304 R 0.214 0.182 --- 0.329 --- 0.286 ** ** ** * 0.179 ** 260 APPENDIX IV-H
XRD peaks (nm) indicative of quartz in Na-saturated, randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100% ; **50-75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Qtz = quartz; Or = orthoclase; Nord = nordstrandite; Gibb = gibbsite; Dias = diaspore; HA = hydroxy apatite; MC(I) = intermediate microcline.
Reference Qtz Qtz Qtz Qtz Qtz XRD 0.426(4) 0.334(x) 0.228(1) 0.182(2) 0.154(2) peaks MC(I) Biot → 0.334(5) 0.154(8) Sample Number ↓ Nord Biot Dias HA Kaol 0.433(2) 0.337(x) 0.232(6) 0.184(5) 0.159(6) Gibb Ms Nord Gibb Vc 0.432(2) 0.332(x) 0.226(4) 0.180(1) 0.153(7) MC(I) MC(I) 0.423(6) 0.180(3)
123 A --- 0.335 ------* 0.331 * 124 A --- 0.331 ------
125 A --- 0.331 0.182 0.155 ** --- 126 A --- 0.333 ------** shared with Ms 0.332(x)
123 B 0.427 0.334 ------*** *
124 B 0.429 ------* shared with Gibb 0.432(2) 125 B ------
126 B 0.425 0.334 ------***
261 APPENDIX IV-H continued.
Reference Qtz Qtz Qtz Qtz Qtz XRD peaks 0.426(4) 0.334(x) 0.228(1) 0.182(2) 0.154(2) → MC(I) Biot Sample 0.334(5) 0.154(8) Number ↓ Nord Biot Dias HA Kaol 0.433(2) 0.337(x) 0.232(6) 0.184(5) 0.159(6) Gibb Ms Nord Gibb Vc 0.432(2) 0.332(x) 0.226(4) 0.180(1) 0.153(7) MC(I) MC(I) 0.423(6) 0.180(3)
300 G --- 0.332 ------***
300 R ------
301 G ------
301 R --- 0.334 ------*
304 G 0.428 0.331 --- 0.153 ** ** --- *
304 R ------0.227 0.182 --- * ** shared with Nord 0.226(4)
262 APPENDIX IV-I
XRD peaks (nm) indicative of gibbsite, bayerite and nordstrandite in Na-saturated, randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed
Gibb = gibbsite; Biot = biotite; Ms = muscovite; Nord = nordstrandite; Zir = zircon; HA = hydroxy apatite; Mona = monazite; Bay = bayerite; All = allanite; Dias = diaspore; MC(I) = intermediate microcline; AbL = low albite; Kaol = kaolinite; Or = orthoclase; Qtz = quartz; Bm = boehmite; Hall = halloysite; Vc = vermiculite.
Reference Gibb Gibb Gibb Gibb Bay XRD [002] 0.224(1) 0.192(1) 0.437(5) 0.222(x) peaks 0.485(x) Zirc Kaol → 0.191(1) 0.437(6) Sample Nord Number 0.190(2) ↓ Biot 0.5 Nord HA Kaol Gibb (weak) 0.226(4) 0.195(3) 0.441(6) 0.224(1) Ms Bay Mona Bay Biot 0.497(3) 0.222(x) 0.188(3) 0.435(7) 0.218(8) Nord All 0.479 (x) 0.218(4) [002] 123 A ------0.438 --- *** 124 A ------0.439 --- *** shared with Kaol 0.441 (6) 125 A ------0.438 --- *** 126 A ------0.436 --- ** shared with Bay 0.435(7)
123 B ------0.440 --- ** 124 B ------0.437 --- *** 125 B ------0.437 --- ** 126 B ------
263 APPENDIX IV-I continued.
Reference Nord Nord Nord Nord Nord Nord Nord XRD [002] 0.390(2) 0.360(1) 0.302(2) 0.226(4) 0.178(2) 0.416(2) peaks 0.479(x) → Sample Number Ms Dias Hall Mona Qtz Gibb Kaol ↓ 0.497(3) 0.399(x) 0.362(6) 0.308(8) 0.228(1) 0.180(1) 0.419(5) Biot MC(I) Kaol Or Gibb MC(I) Mona 0.5 0.380(2) 0.358(8) 0.299(5) 0.224(1) 0.180(3) 0.417(3) (weak) 0.379(4) 0.356(x) Ms Gibb AbL Bay AbL 0.299(4) 0.175(2) 0.403 0.471(9) 0.378(3) Zir (x,6,2) Dias 0.175(1) 0.471(1)
123 A ------0.177 --- **
124 A ------
125 A ------0.418 ** shared with Kaol 0.419(5) 126 A ------
123 B --- 0.387 ------0.178 0.404 * ** *
124 B --- 0.397 0.362 ------0.417 ** ** * 0.395 0.360 0.400 * * 0.356 125 B ------
126 B --- 0.393 ------0.403 **
264 APPENDIX IV-I continued.
Reference Gibb Bay Gibb Bay [001] XRD 0.146(1) 0.435(7) 0.239(2) 0.471(9) peaks Bm Nord Nord Dias [020] → 0.145(2) 0.433(2) 0.239(4) 0.471(1) Sample Nord Gibb Number 0.144(2) 0.432(2) ↓ Bm [002] 0.143(1)
Hall Kaol Gibb Nord[002] 0.148(3) 0.437(6) 0.242(2) 0.479(x) Nord Gibb [004] Vc 0.148(1) 0.437(5) Vc 0.457(6) Dias Qtz 0.238(4) 0.148(2) 0.426(4)
123 A --- 0.438 0.239 --- ***
124 A 0.148 0.439 ------***
125 A --- 0.438 ------***
126 A --- 0.436 ------** shared with Kaol 0.437(6) & Gibb 0.437(5)
123 B --- 0.427 ------***
124 B --- 0.437 ------*** 0.429 * 125 B --- 0.437 ------** 0.432
126 B --- 0.425 0.239 0.473 0.470
265 APPENDIX IV-I continued.
Reference Gibb Gibb Gibb Gibb Bay XRD [002] 0.224(1) 0.192(1) 0.437(5) 0.222(x) peaks 0.485(x) Zirc Kaol → 0.191(1) 0.437(6) Sample Nord Number 0.190(2) ↓ Biot Nord HA Kaol Gibb 0.5 0.226(4) 0.195(3) 0.441(6) 0.224(1) (weak) Bay Mona Bay Biot Ms 0.222(x) 0.188(3) 0.435(7) 0.218(8) 0.497(3) All Nord 0.218(4) 0.479 (x) [002]
300 G ------
300 R ------
301 G ------0.191 ------
301 R ------0.435 --- * 304 G --- 0.226 --- 0.435 0.218 *** * 304 R ------
266 APPENDIX IV-I continued.
Reference Nord Nord Nord Nord Nord Nord Nord XRD [002] 0.390(2) 0.360(1) 0.302(2) 0.226(4) 0.178(2) 0.416(2) peaks 0.479(x) → Sample Number ↓ Ms Dias Hall Mona Qtz Gibb Kaol 0.497(3) 0.399(x) 0.362(6) 0.308(8) 0.228(1) 0.180(1) 0.419(5) Biot MC(I) Kaol Or Gibb MC(I) Mona 0.5 0.380(2) 0.358(8) 0.299(5) 0.224(1) 0.180(3) 0.417(3) (weak) 0.379(4) 0.356(x) Ms Gibb AbL Bay AbL 0.299(4) 0.175(2) 0.403 0.471(9) 0.378(3) Zir (x,6,2) Dias 0.175(1) 0.471(1)
300 G --- 0.390 ------0.418 *** shared with Kaol 0.419(5) 0.408 300 R ------0.418 ** shared with Kaol 0.419(5) 301 G --- 0.394 ------0.416 ***
301 R --- 0.386 --- 0.303 ------0.411 * 0.404
304 G --- 0.389 ------0.226 --- 0.418 * ** shared with Kaol 0.419(5)
304 R --- 0.389 ------0.227 0.179 0.414 * ** ** shared with shared with Qtz Gibb & 0.228(1) MC(I) 0.180(3)
267 APPENDIX IV-I continued.
Reference Gibb Bay Gibb Bay [001] XRD 0.146(1) 0.435(7) 0.239(2) 0.471(9) peaks Bm Nord Nord Dias [020] → 0.145(2) 0.433(2) 0.239(4) 0.471(1) Sample Nord Gibb Number 0.144(2) 0.432(2) ↓ Bm 0.143(1) [002]
Hall Kaol Gibb [004] Nord[002] 0.148(3) 0.437(6) 0.242(2) 0.479(x) Nord Gibb Vc Vc 0.148(1) 0.437(5) 0.238(4) 0.457(6) Dias Qtz 0.148(2) 0.426(4)
300 G --- 0.434 0.240 --- *** shared with Nord 0.433(2)
300 R ------0.239 ---
301 G ------
301 R --- 0.435 ------* 0.430 ***
304 G --- 0.435 0.238 --- *** 0.428 **
304 R ------
268 APPENDIX IV-J
XRD peaks (nm) indicative of pseudoboehmite and boehmite in Na-saturated, randomly oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold. Selected reference XRD peaks for randomly-interstratified phyllosilicates, biotite and kaolinite are also shown to help evaluate peaks attributed to pseudo-boehmite.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; **50-75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Rand. Int = randomly-interstratified phyllosilicates; Biot = biotite; Ms = muscovite; Psbm = pseudo boehmite; Kaol = kaolinite; AbL = low albite; Bm = boehmite; Gibb = gibbsite; HA = hydroxy apatite; Vc = vermiculite; Hall = halloysite; Mona = monazite; Zir = zircon; Dias = diaspore; Nord = nordstrandite.
Refe Rand. Biot Psbm Bm Bm Bm Bm Bm Bm Bm -rence Int. 1.01(x) 0.64- [020] 0.316(6) 0.235(6) 0.186(3) 0.166(1) 0.145(2) 0.143 XRD Ms 0.69 0.611(x) Bm (1) peaks 0.995(x) 0.185(2) [002] → [200] Sample AbL Number Kaol AbL 0.319 Vc Mona Hall Gibb Nord ↓ 0.717(x) 0.639(2) (x,6) 0.237(4) 0.188(3) 0.168(2) 0.146(1) 0.144 0.710(x) Biot Ms Hall HA Biot Nord (2) AbL 0.5Weak 0.319(3) 0.237(1) 0.184(5) 0.167(8) 0.144(2) Dias 0.639(2) Ms Gibb Kaol Zir 0.142 0.497(3) 0.319(1) 0.233(4) 0.165(1) (1) AbL Dias [002] 0.315 0.163(4) (5,3) HA 0.311(2) 123 A 1.104 --- 0.713 --- 0.315 ------1.084 *** *** 124 A 1.097 0.955 0.713 --- 0.315 ------*** *** 125 A --- 0.966 0.707 --- 0.317 ------* *** *** 126 A 1.125 ------0.315 0.236 --- 0.168 ------** ** shared with Vc 0.237(4) & Hall 0.237(1)
0.234 shared with Kaol 0.233(4) 269 APPENDIX IV-J continued.
Refe Rand. Biot Psbm Bm Bm Bm Bm Bm Bm Bm -rence Int. 1.01(x) 0.64- [020] 0.316(6) 0.235(6) 0.186(3) 0.166(1) 0.145(2) 0.143 XRD Ms 0.69 0.611(x) Bm (1) peaks 0.995(x) 0.185(2) [002] → [200] Sample Number Kaol AbL AbL Vc Mona Hall Gibb Nord ↓ 0.717(x) 0.639(2) 0.319 0.237(4) 0.188(3) 0.168(2) 0.146(1) 0.144 0.710(x) Biot (x,6) Hall HA Biot Nord (2) AbL 0.5Weak Ms 0.237(1) 0.184(5) 0.167(8) 0.144(2) Dias 0.639(2) Ms 0.319(3) Kaol Zir 0.142 0.497(3) Gibb 0.233(4) 0.165(1) (1) 0.319(1) Dias [002] AbL 0.163(4) 0.315 (5,3) HA 0.311(2)
123 B 1.170 ------0.318 0.233 ------*** *
124 B --- 0.955 0.719 0.621 0.314 0.236 0.187 0.167 ------** * *** shared shared 0.702 with Vc with ** 0.237(4) Mona & Hall 0.188(3) 0.237(1) 125 B --- 0.960 0.708 --- 0.316 0.236 ------** *** shared with Vc 0.237(4) & Hall 0.237(1) 126 B --- 1.010 ------0.316 ------* **
270 APPENDIX IV-J continued.
Refe Rand. Biot Psbm Bm Bm Bm Bm Bm Bm Bm -rence Int. 1.01(x) 0.64- [020] 0.316(6) 0.235(6) 0.186(3) 0.166(1) 0.145(2) 0.143 XRD Ms 0.69 0.611(x) Bm (1) peaks 0.995(x) 0.185(2) [002] → [200] Sample Number ↓ Kaol AbL AbL Vc Mona Hall Gibb Nord 0.717(x) 0.639(2) 0.319 0.237(4) 0.188(3) 0.168(2) 0.146(1) 0.144 0.710(x) Biot (x,6) Hall HA Biot Nord (2) AbL 0.5Weak Ms 0.237(1) 0.184(5) 0.167(8) 0.144(2) Dias 0.639(2) Ms 0.319(3) Kaol Zir 0.142 0.497(3) Gibb 0.233(4 0.165(1) (1) 0.319(1) Dias [002] AbL 0.163(4) 0.315 (5,3) HA 0.311(2)
300 G ------0.713 ------0.233 --- 0.167 ------*** 0.702 *** 300 R 1.10 --- 0.710 ------0.166 ------** 0.632
301 G 1.071 --- 0.688 --- 0.319 ------* * *** 0.318 *** 301 R 1.21 --- 0.668 0.604 ------0.168 ------* *
304 G 1.14 --- 0.713 --- 0.313 0.237 --- 0.166 ------* *** *** 0.163 1.12 0.708 * *** 1.10 0.705 * *** 304 1.11 --- 0.699 ------R * * 1.09 0.705 * *
271 APPENDIX IV-K
XRD peaks (nm) indicative of diaspore in Na-saturated, randomly oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; **50- 75%; *15-50*. Intensities of less than 15% are not followed by any asterisks.
Psbm = pseudo boehmite; Bm = boehmite; Kaol = kaolinite; AbL = low albite; Biot = biotite; Ms = muscovite; Dias = diaspore; Bay = bayerite; Nord = nordstrandite; Vc = vermiculite.
Reference Dias Dias Dias Dias Dias [020] Dias XRD 0.399(x) 0.243(1) 0.232(6) 0.208(5) 0.471(1) 0.321(1) peaks Bay [001] AbL → 0.471(9) 0.321(6) Sample Number AbL ↓ AbL AbL Kaol Qtz Nord 0.322(7) 0.403(x,6.2) 0.244(4) 0.233(4) 0.213(1) 0.479(x) AbL Nord Mona Qtz Mona Vc 0.320 (x,6) 0.390(2) 0.244(3) 0.228(1) 0.213(3) 0.457(6) Bay 0.320(3) Gibb Dias 0.242(2) 0.213(5) [004] Zir 0.207(2)
123 A 0.397 --- 0.232 ------0.320 *** * * 124 A 0.398 ------*** 125 A 0.398 --- 0.232 0.212 --- 0.320 ** * * 126 A 0.402 0.244 0.231 ------0.320 0.234 ***
123 B 0.404 --- 0.233 ------0.321 * * ** 124 B 0.400 ------0.397 * 0.395 * 125 B 0.397 --- 0.232 ------* 126 B 0.403 ------0.473 0.321 ** 0.470 *** 272 APPENDIX IV-K continued.
Reference Dias Dias Dias Dias Dias [020] Dias XRD 0.399(x) 0.243(1) 0.232(6) 0.208(5) 0.471(1) 0.321(1) peaks Bay [001] AbL → 0.471(9) 0.321(6) Sample Number ↓ AbL AbL Kaol Qtz Nord AbL 0.403(x,6.2) 0.244(4) 0.233(4) 0.213(1) 0.479(x) 0.322(7) Nord Mona Qtz Mona Vc AbL 0.390(2) 0.244(3) 0.228(1) 0.213(3) 0.457(6) 0.320 (x,6) Gibb Dias Bay 0.320(3) 0.242(2) 0.213(5) [004] Zir 0.207(2)
300 G ------0.233 ------0.322 **
300 R ------0.214 --- 0.321 ** ***
301 G ------0.214 ------**
301 R 0.404 ------0.323 *
304 G ------0.321 *
304 R ------0.227 0.214 --- 0.323 * ** * 0.320 ***
273 APPENDIX IV-L
XRD peaks (nm) indicative of hydroxy apatite in Na saturated, randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
HA = hydroxy apatite; AbL = low albite; Mona = monazite; Vc-Hb = vermiculite-hydrobiotite; All = allanite; Nord = nordstrandite; MC(I) = intermediate microcline; Or = orthoclase; Biot = biotite.
Reference HA HA HA HA HA XRD 0.311(2) 0.283(x) 0.273(8) 0.345(4) 0.263(2) peaks HA Nord All → 0.278(3) 0.345(1) 0.263(4) Sample Number AbL Mona Vc-Hb MC(I) Biot ↓ 0.315 0.286(x) 0.275(2) 0.348(2) 0.266(8) (5,3) Vc-Hb All 0.347(5) Vc Mona 0.275(2) 0.271(7) Or 0.262(5) 0.309(x) 0.347(5) Mona Vc-Hb 0.308(8) 0.340(4)
123 A 0.315 0.284 ------0.268 *** * * 0.312 0.263 * * 124 A 0.315 ------*** 125 A ------
126 A 0.315 ------**
123 B ------0.348 --- ** 124 B 0.314 0.279 ------*** 0.281 0.311 *** 125 B ------
126 B ------0.345 ---
274 APPENDIX IV-L continued.
Reference HA HA HA HA HA XRD 0.311(2) 0.283(x) 0.273(8) 0.345(4) 0.263(2) peaks HA Nord All → 0.278(3) 0.345(1) 0.263(4) Sample Number AbL Mona Vc-Hb MC(I) Biot ↓ 0.315 0.286(x) 0.275(2) 0.348(2) 0.266(8) (5,3) Vc-Hb All 0.347(5) Vc Mona 0.275(2) 0.271(7) Or 0.262(5) 0.309(x) 0.347(5) Mona Vc-Hb 0.308(8) 0.340(4)
300 G ------0.348 0.261 * 0.344 * 300 R ------0.342 ---
301 G ------
301 R --- 0.280 --- 0.340 0.264 * *** *
304 G 0.313 --- 0.274 0.344 --- *** *** shared with shared with AbL 0.315(5,3) Vc-Hb 0.275(2)
304 R ------
275 APPENDIX IV-M
XRD peaks (nm) indicative of monazite in Na saturated, randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Mona = monazite; Kaol = kaolinite; Nord = nordstrandite; HA = hydroxy apatite; All = allanite; MC(I) = intermediate microcline; Qtz = quartz; Dias = diaspore; Ms -= muscovite; Gibb = gibbsite; Zir = zircon; Bay = bayerite.
Refe Mona Mona Mona Mona Mona Mona -rence 0.417(3) 0.309(x) 0.287(7) 0.215(3,4) 0.196(5,3) 0.174(4) XRD Mona Mona peaks 0.308(8) 0.286(x) → Sample Kaol HA All Biot Ms Nord Number 0.419(5) 0.311(2) 0.289(3) 0.218(8) 0.199(5) 0.178(2) ↓ Nord Nord HA All Gibb Gibb 0.416(2) 0.302(2) 0.283(x) 0.218(4) 0.199(1 0.175(2) MC(I) HA Zir 0.216(3) 0.195(3) 0.175(1) All Gibb Bay 0.216(3) 0.192(1) 0.172(4) Qtz 0.213(1) Mona 0.213(3) Dias 0.213(5) 123 A ------0.287 ------0.177 * ** 124 A ------125 A 0.418 ------0.199 --- ** shared with Kaol 0.419(5) 126 A ------0.215 ------
123 B ------0.178 ** 124 B 0.417 0.311 ------* *** 125 B ------0.286 ------126 B ------0.285 ------* 276 APPENDIX IV-M continued.
Reference Mona Mona Mona Mona Mona Mona XRD 0.417(3) 0.309(x) 0.287(7) 0.215(3,4) 0.196(5,3) 0.174(4) peaks Mona Mona → 0.308(8) 0.286(x) Biot Sample 0.218(8) Number Kaol HA All All Ms Nord ↓ 0.419(5) 0.311(2) 0.289(3) 0.218(4) 0.199(5) 0.178(2) Nord Nord HA MC(I) Gibb Gibb 0.416(2) 0.302(2) 0.283(x) 0.216(3) 0.199(1 0.175(2) All HA Zir 0.216(3) 0.195(3) 0.175(1) Gibb Bay Qtz 0.192(1) 0.172(4) 0.213(1) Mona 0.213(3) Dias 0.213(5)
300 G 0.418 --- 0.288 ------*** * shared with shared with Kaol All 0.289(3) 0.419(5)
300 R 0.418 --- 0.287 0.214 0.198 --- ** ** * shared with shared with Kaol Qtz0.213(1) 0.419(5) Mona0.213(3) & Dias0.213(5) 301 G 0.416 --- 0.285 0.214 ------** shared with Qtz0.213(1) Mona0.213(3) & Dias0.213(5) 301 R 0.411 0.303 ------
304 G 0.418 0.285 0.218 0.194 --- ** * * shared with Kaol 0.419(5)
304 R 0.414 --- 0.286 0.214 ------** * ** shared with Qtz0.213(1) Mona0.213(3) & Dias0.213(5)
277 APPENDIX IV-N
XRD peaks (nm) indicative of allanite in Na saturated, randomly-oriented specimens of the silt-sized fraction of saprolite.
Peaks in the samples that are considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
All = allanite; Or = orthoclase; AbL = low albite; HA = hydroxy apatite; Biot = biotite; Kaol = kaolinite; Mona = monazite; Biot = Biotite; Vc = vermiculite; MC(I) = intermediate microcline; Qtz = quartz; Dias = diaspore.
Reference All All All All All All XRD 0.292(x) 0.271(7) 0.353(5) 0.289(3) 0.263(4) 0.216(3) peaks HA MC(I) → 0.263(2) 0.216(3) Sample Number AbL HA Kaol All Biot Biot ↓ 0.293(3,2) 0.273(8) 0.358(8) 0.292(x) 0.266(8) 0.218(8) Or Biot 0.356(x) Or Vc All 0.290(3) 0.266(8) AbL 0.290(3) 0.262(5) 0.218(4) 0.351(1) Mona Mona Mona 0.287(7) 0.215(3,4) 0.351(3) Qtz 0.213(1) Mona 0.213(3) Dias 0.213(5)
123 A ------0.353 0.287 0.268 --- ** * * 0.263 * 124 A ------0.353 ------** 125 A 0.290 0.269 0.354 0.290 ------** 126 A ------0.355 ------0.215 *
123 B 0.293 ------*** 124 B 0.291 --- 0.356 0.291 ------0.354 125 B 0.291 --- 0.352 0.291 ------* 126 B 0.293 --- 0.356 ------** * 278 APPENDIX IV-N continued.
Reference All All All All All All XRD 0.292(x) 0.271(7) 0.353(5) 0.289(3) 0.263(4) 0.216(3) peaks HA MC(I) → 0.263(2) 0.216(3) Sample Number AbL HA Kaol All Biot Biot ↓ 0.293(3,2) 0.273(8) 0.358(8) 0.292(x) 0.266(8) 0.218(8) Or Biot 0.356(x) Or Vc All 0.290(3) 0.266(8) AbL 0.290(3) 0.262(5) 0.218(4) 0.351(1) Mona Mona Mona 0.287(7) 0.215(3,4) 0.351(3) Qtz 0.213(1) Mona 0.213(3) Dias 0.213(5)
300 G 0.288 --- 0.357 0.288 0.261 --- * ** * 300 R ------0.287 --- 0.214 ** 301 G ------0.214 ** 301 R 0.294 --- 0.353 --- 0.264 --- * * * 304 G ------0.357 ------0.218 ** * 304 R 0.295 ------0.214 * **
279 APPENDIX IV-O
XRD peaks (nm) indicative of zircon in Na saturated, randomly-oriented powder mounts of the silt-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; **50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Zir = zircon; Hall = halloysite; Kaol = kaolinite; Ms = muscovite; Or = orthoclase; Gibb = gibbsite; MC(I) = intermediate microcline; MC(M) = maximum microcline; Mona = monazite; Vc = vermiculite; Dias = diaspore; Nord = nordstrandite; Bay = bayerite; Biot = biotite; Bm = boehmite.
Reference Zir Zir Zir Zir Zir Zir Zir Zir XRD 0.443(5) 0.330(x) 0.252(5) 0.207(2) 0.191(1) 0.175(1) 0.171(4) 0.165(1) peaks Gibb Dias → 0.175(2) 0.171(2) Sample Number Hall Ms Vc Dias Gibb Nord Bay Bm ↓ 0.445 0.332(x) 0.253(5) 0.208(5) 0.192(1) 0.178(2) 0.172(4) 0.166(1) Hall Or Gibb Nord Mona Gibb Dias 0.442(x) 0.331(x) Kaol 0.204(2) 0.190(2) 0.174(4) 0.169(1) 0.163(4) Kaol Gibb 0.250(5) Hall 0.441(6) 0.331(2) Kaol 0.168(2) MC(I) 0.249(3) Biot 0.329(x,5) 0.167(8) MC(M) 0.329(5) Or 0.329(6) Mona 0.329(4)
123 --- 0.331 0.252 ------0.177 ------A * ** 0.328 * 124 --- 0.331 0.249 ------A
125 --- 0.331 0.254 0.212 ------A ** ** *
0.249 * 126 0.442 0.333 ------0.168 0.168 A *** **
280 APPENDIX IV-O continued.
Reference Zir Zir Zir Zir Zir Zir Zir Zir XRD 0.443(5) 0.330(x) 0.252(5) 0.207(2) 0.191(1) 0.175(1) 0.171(4) 0.165(1) peaks Gibb Dias → 0.175(2) 0.171(2) Sample Number Hall Ms Vc Dias Gibb Nord Bay Bm ↓ 0.445 0.332(x) 0.253(5) 0.208(5) 0.192(1) 0.178(2) 0.172(4) 0.166(1) Hall Or Gibb Nord Mona Gibb Dias 0.442(x) 0.331(x) Kaol 0.204(2) 0.190(2) 0.174(4) 0.169(1) 0.163(4) Kaol Gibb 0.250(5) Hall 0.441(6) 0.331(2) Kaol 0.168(2) MC(I) 0.249(3) Biot 0.329(x,5) 0.167(8) MC(M) 0.329(5) Or 0.329(6) Mona 0.329(4)
123 0.445 --- 0.252 ------0.178 ------B *** * ** 0.444 *** 0.440 ** 124 --- 0.330 0.252 --- 0.189 --- 0.167 0.167 B ** *
125 --- 0.330 0.253 ------B * 126 0.444 ------B ***
300 --- 0.330 ------0.167 0.167 G ** 0.332 *** 300 --- 0.330 --- 0.214 ------0.166 R *** **
301 --- 0.328 0.252 0.214 0.191 ------G * **
301 --- 0.329 0.249 ------0.168 0.168 R *** *
304 --- 0.331 0.254 ------0.166 G ** ** 0.163
304 --- 0.329 0.254 0.214 --- 0.179 ------R ** * ** ** 0.249 *
281 APPENDIX V
X-RAY DIFFRACTION DATA FOR THE CLAY-SIZED FRACTION
APPENDIX V-A
800 M 700 g
600 Mg-Gly 500
400
intensity K,25oC 300
200 K, 350oC
100 K, 550oC 0 0 10203040 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 123A.
282 APPENDIX V-A continued.
800
Mg- 700
600
500 Mg-Gly
400
o intensity K, 25 C 300
200 K, 350oC
100 K, 550 oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 124A.
283 APPENDIX V-A continued.
800
700 Mg-
600
500 Mg-Gly
400 o
intensity K-25 C
300
o 200 K-350 C
100 K-550oC*
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 125A.
284 APPENDIX V-A continued.
800
700
Mg-
600
Mg-Gly 500
400 intensity K-25oC
300
200 K-350oC
100 K- 550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 126A. 285 APPENDIX V-A continued.
800
700 Mg-
600
500 Mg-Gly
400 intensity
K-25oC 300
200 K-350oC
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 123B.
286 APPENDIX V-A continued.
800 Mg-
700
600
Mg-Gly
500
400 K-25oC intensity
300
K-350oC
200
o 100 K-550 C
0 0 5 10 15 20 25 30 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 124B. 287 APPENDIX V-A continued.
800
700
Mg- 600
500 Mg-Gly
400 intensity
K-25oC 300
200 K-350oC
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 125B. 288 APPENDIX V-A continued.
800
700 Mg-
600
Mg-Gly 500
400 intensity K-25oC
300
o 200 K-350 C
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 126B.
289 APPENDIX V-A continued.
750
650 Mg-
550
Mg-Gly
450
350 K-25oC intensity
250
K-350oC
150
K-550oC 50
0 5 10 15 20 25 30 35 -50 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 300G. 290 APPENDIX V-A continued.
800
700 Mg-
600
500 Mg-Gly
400 intensity K-25oC
300
K-350oC 200
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 300R.
291 APPENDIX V-A continued.
800
700
Mg-
600
Mg-Gly 500
400
intensity K-25oC
300
o 200 K-350 C
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 301G.
292 APPENDIX V-A continued.
700
Mg- 600
500 Mg-Gly
400 K-25oC intensity 300
o 200 K-350 C
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 301R. 293 APPENDIX V-A continued.
700
600 Mg-
Mg-Gly 500
400
K-25oC intensity
300
K-350oC 200
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 304G. 294 APPENDIX V-A continued.
700
Mg- 600
500 Mg-Gly
400
o
intensity K-25 C
300
o 200 K-350 C
100 K-550oC
0 0 5 10 15 20 25 30 35 degrees 2 theta
X-ray diffractograms of deferrated, K-saturated clays at 25oC, 350oC, and 550oC, and of Mg- and Mg-glycerolated clays from sample 304R.
295 APPENDIX V-B
XRD peaks (nm) indicative of 2:1 phyllosilicates in oriented specimens of the clay-sized fraction of saprolite.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
The reference XRD peak for vermiculite [0.457(6)] is for Na-saturated specimens, from JCPDS card 16-613. The reference peaks for vermiculite-hydrobiotite [0.450(6), 0.340(4)] are for Na- saturated specimens from JCPDS cards 13-465.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50-75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Reg. Int. = regularly interstratified phyllosilicates; Biot = biotite; Ms = muscovite; Bay = bayerite; Dias = diaspore; Vc-Hb = vermiculite-hydrobiotite; Vc = vermiculite; Hall = halloysite; HA = hydroxy apatite; Nord = nordstrandite; Qtz = quartz; MC(I) = intermediate microcline; Or = orthoclase; Gibb = gibbsite.
Reference Reg. 1.635- 1.298- 1.099- peaks → Int. 1.299 1.100 0.940 Sample Number & Treatments ↓ 123A Mg --- 1.509 1.271 --- Mg-Gly --- 1.348 1.155* --- K(RT) --- 1.420 1.210 0.99 K350oC ------1.033 K550oC ------1.045*** 124A Mg --- 1.401 1.170* 0.971 Mg-Gly ------1.218* 1.021 K(RT) ------1.194 1.021 K350oC ------1.016,1.004 K550oC ------1.033***,1.021*** 125A Mg ------1.155 0.981 Mg-Gly ------1.155,1.140 1.064,1.004,0.971 K(RT) --- 1.563 --- 1.021,0.998,0.987,0.976 K350oC ------0.971* K550oC ------0.998*** 126A Mg ------1.186*** 0.982 Mg-Gly ------1.147*** 0.960* K(RT) --- 1.620 1.178*** 0.998* K350oC ------1.027*,0.971 K550oC ------0.993***
296 APPENDIX V-B continued
Reference Reg. 1.635- 1.298- 1.099- peaks → Int. 1.299 1.100 0.940 Sample Number & Treatments ↓ 123B Mg ------1.147* 0.966* Mg-Gly ------1.227,1.132** 0.955* K(RT) ------1.124* 1.05* K350oC ------0.998*,0.966* K550oC ------0.998*** 124B Mg ------1.170,1.104 0.971* Mg-Gly ------1.147 0.971* K(RT) ------1.084*,1.064* 1.046* K350oC ------0.998,0.960*,0.950 K550oC ------0.993** 125B Mg ------1.147* 0.966* Mg-Gly ------1.262* 1.039* K(RT) ------1.104 0.960* K350oC ------0.950* K550oC --- 1.348 --- 0.976*** 126B Mg --- 1.380 1.170* 0.976* Mg-Gly ------1.155* 0.971* K(RT) --- 1.635,1.402 1.155* 1.010*,0.987* K350oC ------0.982* K550oC ------1.004***
297 APPENDIX V-B continued
Reference Reg. 1.635- 1.298- 1.099- peaks → Int. 1.299 1.100 0.940 Sample Number & Treatments ↓ 300G Mg --- 1.413,1.380,1.348 1.155 --- Mg-Gly --- 1.369 1.147 --- K(RT) --- 1.535,1.436 1.244 1.021,0.940 K350oC ------1.091,1.077 K550oC ------1.091***,1.071*** 300R Mg 2.386 1.402,1.380,1.359 1.186*** 0.982,0.807 Mg-Gly 2.264 1.338* 1.140*** 0.955 K(RT) --- 1.484,1.436,1.380 1.235** 1.051,1.021 K350oC ------1.052*,1.016,0.993,0.971 K550oC ------0.993*** 301G Mg --- 1.380 1.170 --- Mg-Gly --- 1.413,1.318 1.170 0.976* K(RT) --- 1.348 1.186,1.140 0.976 K350oC ------1.033 K550oC ------301R Mg --- 1.380* 1.186*,1.170* --- Mg-Gly --- 1.424,1.391 1.178* --- K(RT) --- 1.299 1.125* --- K350oC ------1.202,1.104 1.052,0.998 K550oC ------1.021*** 304G Mg --- 1.510 1.289 --- Mg-Gly --- 1.563 1.218 --- K(RT) --- 1.369,1.359,1.318 1.125 0.960 K350oC ------1.052,0.987 K550oC ------1.033** 304R Mg --- 1.591,1.563,1.510,1.369 1.289* 1.058 Mg-Gly --- 1.497, 1.359 1.155* 0.960 K(RT) --- 1.380 1.162* 0.976 K350oC ------1.058,0.987 K550oC ------1.046***,1.021***
298 APPENDIX V-B continued
Reference (002)? Biot Vc Vc- Vc-Hb Biot Ms peaks → 0.5 weak 0.457(6) Hb 0.340(4) 0.337(x) 0.332(x) Sample Ms 0.450(6) Number & 0.497(3) Treatments Bay Vc HA Vc-Hb Qtz ↓ 0.471(9) 0.457(6) 0.345(4) 0.340(4) 0.334(x) Dias Hall Nord Qtz MC(I) 0.471(1) 0.445 0.345(1) 0.334(x) 0.334(5) Vc-Hb Biot MC(I) Or 0.450(6) 0.337(x) 0.334(5) 0.331(x) Gibb 0.331(2)
123A Mg --- 0.492 --- 0.449 ------Mg-Gly ------K(RT) ------K350oC ------K550oC --- 0.508 ------0.337**,0.335** --- 124A Mg --- 0.494 ------0.336 --- Mg-Gly --- 0.502 --- 0.448* --- 0.337 --- K(RT) --- 0.504,0.499 ------0.335 --- K350oC ------K550oC --- 0.509 ------0.337** 0.332* 125A Mg --- 0.498,0.494 ------0.335 --- Mg-Gly ------K(RT) --- 0.494 ------0.332 K350oC ------K550oC ------126A Mg ------0.333 Mg-Gly ------0.340* ------K(RT) --- 0.499 ------0.339 0.336 --- K350oC --- 0.492 ------K550oC ------0.334**
299 APPENDIX V-B continued
Reference (002)? Biot Vc Vc- Vc-Hb Biot Ms peaks → 0.5 weak 0.457(6) Hb 0.340(4) 0.337(x) 0.332(x) Sample Ms 0.450(6) Number & 0.497(3) Treatments Bay Vc HA Vc-Hb Qtz ↓ 0.471(9) 0.457(6) 0.345(4) 0.340(4) 0.334(x) Dias Hall Nord Qtz MC(I) 0.471(1) 0.445 0.345(1) 0.334(x) 0.334(5) Vc-Hb Biot MC(I) Or 0.450(6) 0.337(x) 0.334(5) 0.331(x) Gibb 0.331(2)
123B Mg --- 0.491 ------Mg-Gly 0.545,0.518 ------0.340 0.338 --- K(RT) 0.512 0.509,0.494* --- 0.452** 0.339* ------K350oC --- 0.492 ------K550oC --- 0.498 ------0.334** 124B Mg --- 0.495,0.493,0.492 ------Mg-Gly --- 0.492 ------K(RT) 0.511 ------0.452* 0.339* ------K350oC ------K550oC --- 0.496 ------0.333* 125B Mg ------Mg-Gly --- 0.506 --- 0.452** 0.339* 0.337 --- K(RT) --- 0.491 ------0.335 0.333 K350oC ------K550oC --- 0.496 ------126B Mg --- 0.496,0.495,0.494,0.492 ------0.332* Mg-Gly --- 0.492 ------K(RT) --- 0.498,0.496 ------0.335*, 0.334* K350oC --- 0.491 ------K550oC --- 0.499 ------0.335** ---
300 APPENDIX V-B continued
Reference (002)? Biot Vc Vc- Vc-Hb Biot Ms peaks → 0.5 weak 0.457(6) Hb 0.340(4) 0.337(x) 0.332(x) Sample Ms 0.450(6) Number & 0.497(3) Treatments ↓ Bay Vc HA Qtz Qtz 0.471(9) 0.457(6) 0.345(4) 0.334(x) 0.334(x) Dias Hall Nord MC(I) MC(I) 0.471(1) 0.445 0.345(1) 0.334(5) 0.334(5) Vc-Hb Biot Or 0.450(6) 0.337(x) 0.331(x) Gibb 0.331(2)
300G Mg ------Mg-Gly ------K(RT) --- 0.506 --- 0.449 --- 0.337 --- K350oC ------K550oC ------0.340* 0.337* --- 300R Mg ------0.333 Mg-Gly ------0.340* --- 0.334* K(RT) 0.594 0.503 --- 0.452*,0.448* 0.339* 0.338* --- K350oC --- 0.495 ------0.335* 0.334*,0.332 K550oC --- 0.496 ------0.332*** 301G Mg ------Mg-Gly ------0.342 ------K(RT) ------K350oC ------K550oC ------0.334*** 301R Mg ------Mg-Gly ------0.342 --- 0.333 K(RT) ------0.458 ------0.337 --- K350oC ------0.335 0.332 K550oC ------0.336*** --- 304G Mg ------0.452 ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------0.336*** --- 304R Mg --- 0.503,0.498 0.457 --- 0.342 ------Mg-Gly ------0.341* ------K(RT) --- 0.495 ------K350oC --- 0.496,0.495 ------0.334 K550oC --- 0.503 ------0.336*** ---
301 APPENDIX V-C
XRD peaks (nm) indicative of halloysite and kaolinite in oriented specimens of the clay- sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Hall = halloysite; Hall(10A) = 10 angstrom halloysite; Kaol = kaolinite; Psbm = pseudoboehmite; Vc-Hb = vermiculite-hydrobiotite; Zirc = zircon; Gibb = gibbsite; Bay = bayerite; MC(M) = maximum microcline; Mona = monazite; Nord = nordstrandite; MC(I) = intermediate microcline; AbL = low albite; All = allanite; Qtz = quartz; Biot = biotite; Ms = muscovite.
Reference Hall Hall Kaol peaks → 1.01(9) 0.730(7) 0.717(x) Sample 1.00(x) 0.710(x) Number & Hall Treatments 0.730(7) ↓ Psbm 0.64-0.69
123A Mg --- 0.745***, 0.737*** --- Mg-Gly ------0.708*** K(RT) 0.99 0.727*** --- K350oC 1.033 --- 0.699*** K550oC 1.045*** ------124A Mg 0.971 --- 0.719***,0.713***,0.706*** Mg-Gly 1.021 0.740***0.734*** --- K(RT) 1.021 0.734*** --- K350oC 1.016,1.004 --- 0.702*** K550oC 1.033***,1.021*** ------125A Mg 0.981 --- 0.722*** Mg-Gly 1.064,1.004,0.971 --- 0.705*** K(RT) 1.021,0.998,0.987,0.976 --- 0.713*** K350oC 0.971* --- 0.702*** K550oC 0.998*** ------126A Mg 0.982 0.728** --- Mg-Gly 0.960* --- 0.713***,0.710***,0.705*** K(RT) 0.998* 0.737*** --- K350oC 1.027*,0.971 --- 0.713*** K550oC 0.993*** ------302 APPENDIX V-C continued
Reference Hall (10A) Hall Kaol peaks → 1.01(9) 0.730(7) 0.717(x) Sample 1.00(x) 0.710(x) Number & Hall Treatments 0.730(7) ↓ Psbm 0.64-0.69
123B Mg 0.966* --- 0.722***,0.710*** Mg-Gly 0.955* --- 0.710*** K(RT) 1.05* 0.786***,0.766***,0.746*** --- K350oC 0.998*,0.966* --- 0.708*** K550oC 0.998*** ------124B Mg 0.971* --- 0.716*** Mg-Gly 0.971* --- 0.713*** K(RT) 1.046* 0.772***,0.756*** --- K350oC 0.998,0.960*,0.950 --- 0.708*** K550oC 0.993** ------125B Mg 0.966* --- 0.716***,0.708*** Mg-Gly 1.039* 0.756***,0.752*** --- K(RT) 0.960* 0.725*** 0.713***,0.702*** K350oC 0.950* --- 0.705*** K550oC 0.976*** ------126B Mg 0.976* --- 0.716*** Mg-Gly 0.971* --- 0.713*** K(RT) 1.010*,0.987* 0.728*** --- K350oC 0.982* --- 0.708*** K550oC 1.004*** ------
303 APPENDIX V-C continued
Reference Hall (10A) Hall Kaol peaks → 1.01 0.730 0.717(x) Sample (9) (7) 0.710(x) Number & 1.00 (x) Hall Treatments 0.730(7) ↓ Hall 0.730(7)
300G Mg ------0.710*** Mg-Gly ------0.713*** K(RT) 1.021,0.940 0.736** --- K350oC 1.091,1.077 0.734*** --- K550oC 1.091***,1.071*** ------300R Mg 0.982,0.807 --- 0.716*** Mg-Gly 0.955 --- 0.708*** K(RT) 1.051,1.021 0.749***,0.740*** --- K350oC 1.052*,1.016,0.993,0.971 --- 0.708*** K550oC 0.993*** ------301G Mg ------0.719***,0.716***,0.710*** Mg-Gly 0.976* --- 0.708*** K(RT) 0.976 --- 0.716***,0.708*** K350oC 1.033 --- 0.708*** K550oC ------301R Mg ------0.713*** Mg-Gly ------0.710*** K(RT) ------0.708*** K350oC 1.052,0.998 --- 0.713***,0.710*** K550oC 1.021*** ------304G Mg --- 0.759*** --- Mg-Gly --- 0.728*** --- K(RT) 0.960 --- 0.706*** K350oC 1.052,0.987 --- 0.713*** K550oC 1.033** ------304R Mg 1.058 0.752*** --- Mg-Gly 0.960 --- 0.702*** K(RT) 0.976 --- 0.716*** K350oC 1.058,0.987 --- 0.713*** K550oC 1.046***,1.021*** ------
304 APPENDIX V-C continued
Reference peaks Hall Hall Kaol → 0.445 0.442(x) 0.437(6) Sample Kaol Gibb Number & 0.441(6) 0.437(5) Hall (10A) Treatments ↓ Zirc 0.436(7) Vc-Hb 0.443(5) 0.450(6) Kaol Kaol Zirc 0.437(6) 0.441(6) 0.443(5) Gibb Bay 0.437(5) 0.435(7)
123A Mg 0.449,0.444 ------Mg-Gly ------K(RT) 0.446 0.443 --- K350oC ------K550oC ------124A Mg --- 0.439* 0.439* Mg-Gly 0.448* ------K(RT) 0.447* ------K350oC ------0.435* K550oC ------125A Mg --- 0.440* --- Mg-Gly --- 0.439** 0.439**,0.437**,0.435** K(RT) --- 0.439* 0.439* K350oC ------0.435* K550oC --- 0.440 --- 126A Mg --- 0.441** --- Mg-Gly ------0.438** K(RT) 0.446** ------K350oC ------0.438** K550oC ------0.437
305 APPENDIX V-C continued
Reference peaks Hall Hall Kaol → 0.445 0.442(x) 0.437(6) Sample Kaol Gibb Number 0.441(6) 0.437(5) Hall (10A) & 0.436(7) Treatments ↓ Vc-Hb Zirc Kaol 0.450(6) 0.443(5) 0.441(6) Zirc Kaol Bay 0.443(5) 0.437(6) 0.435(7) Gibb 0.437(5)
123B Mg ------0.435** Mg-Gly ------K(RT) 0.447**,0.445** 0.441* --- K350oC ------0.436* K550oC --- 0.439 0.439 124B Mg ------0.437** Mg-Gly ------0.438** K(RT) --- 0.442 --- K350oC ------0.436* K550oC ------125B Mg ------0.437*,0.435* Mg-Gly ------0.434* K(RT) ------0.434** K350oC ------0.434** K550oC --- 0.439** 0.439**,0.435 126B Mg ------Mg-Gly --- 0.440** 0.436** K(RT) 0.445** 0.441** --- K350oC ------0.437* K550oC 0.445 ------
306 APPENDIX V-C continued
Reference Hall Hall Kaol peaks → 0.445 0.442(x) 0.437(6) Sample Kaol Gibb Number 0.441(6) 0.437(5) Hall(10A) & 0.436(7) Treatments ↓ Vc- Zirc Kaol Hb 0.443(5) 0.441(6) 0.450(6) Kaol Bay Zirc 0.437(6) 0.435(7) 0.443(5) Gibb 0.437(5)
300G Mg ------0.438 Mg-Gly ------0.438* K(RT) ------K350oC 0.445 ------K550oC ------300R Mg --- 0.442 --- Mg-Gly ------0.438* K(RT) ------K350oC ------0.438* K550oC ------0.438 301G Mg --- 0.440* --- Mg-Gly --- 0.439* 0.439* K(RT) ------0.435* K350oC ------0.437* K550oC ------301R Mg ------0.438 Mg-Gly --- 0.439* 0.439* K(RT) ------0.435 K350oC ------0.437 K550oC ------304G Mg ------Mg-Gly 0.446* ------K(RT) --- 0.439 0.439 K350oC --- 0.439 0.439 K550oC ------304R Mg ------Mg-Gly ------0.438,0.436 K(RT) --- 0.441 --- K350oC --- 0.439 0.439 K550oC ------
307 APPENDIX V-C continued
Reference Kaol Kaol Hall Kaol Hall (10Å) peaks → 0.419 0.384 0.362(6) 0.358(8) 0.335(4) Sample (5) 0.363(9) 0.356(x) 0.334(9) Number
& Qtz MC(M) Nord AbL Nord 0.334(x) Treatments 0.421(5) 0.390(2) 0.366(6,3,2) 0.360(1) MC(I) ↓ Mona MC(I) Nord All 0.334(5) 0.417(3) 0.380(2) 0.360(1) 0.353(5) Biot 0.337(x) Ms 0.332(x)
123A Mg ------0.362** ------Mg-Gly ------0.356** --- K(RT) ------0.358** --- K350oC ------0.352** --- K550oC ------0.337**,0.335** 124A Mg ------0.355** 0.336 Mg-Gly ------0.362** --- 0.337 K(RT) ------0.359** 0.335 K350oC ------0.352** --- K550oC ------0.337**,0.332* 125A Mg ------0.357** 0.335 Mg-Gly ------0.354** --- K(RT) ------0.354** 0.332 K350oC ------0.352** --- K550oC ------0.364 ------126A Mg ------0.359* 0.359*,0.355* 0.333 Mg-Gly 0.417 ------0.354** --- K(RT) ------0.357** 0.336 K350oC ------0.353**,0.352** --- K550oC 0.418 ------0.334**
308 APPENDIX V-C continued
Reference Kaol Kaol Hall Kaol Hall (10Å) peaks → 0.419 0.384 0.362(6) 0.358(8) 0.335(4) Sample (5) 0.363(9) 0.356(x) 0.334(9) Number
& Qtz MC(M) Nord AbL Nord 0.334(x) Treatments 0.421(5) 0.390(2) 0.366(6,3,2) 0.360(1) MC(I) ↓ Mona MC(I) Nord All 0.334(5) 0.417(3) 0.380(2) 0.360(1) 0.353(5) Biot 0.337(x) Ms 0.332(x)
123B Mg ------0.352** --- Mg-Gly ------0.361** 0.355** 0.338 K(RT) ------0.361** ------K350oC ------0.354** --- K550oC ------0.334** 124B Mg ------0.354** --- Mg-Gly ------0.354** --- K(RT) --- 0.383 0.363 0.353**,0.352** --- K350oC ------K550oC ------0.363 --- 0.333* 125B Mg 0.418 ------0.354 --- Mg-Gly 0.420 0.387 0.363** 0.354 0.337 K(RT) 0.418 ------0.358*, 0.354* 0.335, 0.333 K350oC ------0.352** --- K550oC 0.420* ------126B Mg ------0.355** 0.332* Mg-Gly 0.420 --- 0.362** 0.357**,0.356** --- K(RT) ------0.357** 0.335*,0.334* o ------K350 C ------0.353** --- K550oC ------0.335**
309 APPENDIX V-C continued
Reference Kaol Kaol Hall Kaol Hall (10Å) peaks → 0.419 0.384 0.362(6) 0.358(8) 0.335(4) Sample (5) 0.356(x) 0.334(9) Number Nord AbL Qtz MC(M) 0.390 0.366(6,3,2) Nord & 0.334(x) 0.421(5) (2) Nord 0.360(1) MC(I) Treatments Mona MC(I) 0.360(1) All 0.334(5) ↓ 0.417 0.380(2) 0.353(5) (3) Biot 0.337(x) Ms 0.332(x)
300G Mg ------0.354** --- Mg-Gly ------0.354** --- K(RT) ------0.361** --- 0.337 K350oC ------0.361** ------K550oC ------0.337* 300R Mg ------0.356** 0.333 Mg-Gly ------0.352** --- K(RT) ------0.362*** --- 0.338* K350oC 0.419,0.417 0.381 --- 0.356** 0.335*,0.334*,0.332 K550oC 0.420* 0.382 ------0.332, 0.332*** 301G Mg ------0.354** --- Mg-Gly ------0.354** --- K(RT) ------0.354** --- K350oC ------0.354** --- K550oC ------0.334*** 301R Mg 0.419 ------0.354** --- Mg-Gly ------0.356** 0.333 K(RT) ------0.353** 0.337 K350oC ------0.355** 0.335, 0.332 K550oC --- 0.387 ------0.336*** 304G Mg ------0.364** ------Mg-Gly ------0.360** 0.360** --- K(RT) ------0.354** --- K350oC ------0.356** --- K550oC ------0.336*** 304R Mg ------0.354* --- Mg-Gly ------0.354** --- K(RT) 0.420* ------0.355* --- K350oC ------0.356** 0.334 K550oC --- 0.387 --- 0.355, 0.353 0.336***
310 APPENDIX V-D
(overleaf). XRD peaks (nm) indicative of gibbsite in oriented specimens of the clay- sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Gibb = gibbsite; Biot = biotite; Ms = muscovite; Nord = nordstrandite; Bay = bayerite; Kaol = kaolinite; Qtz = quartz; Or = orthoclase; Zir = zircon; MC(I) = intermediate microcline; MC(M) = maximum microcline; Mona = monazite.
311 APPENDIX V-D continued.
Reference Gibb [002] Gibb Gibb Gibb peaks → 0.485(x) 0.432(2) 0.437(5) 0.331(2) Sample Nord Kaol Or Number 0.433(2) 0.437(6) 0.331(x) & Bay Treatments 0.435(7) ↓ Biot Kaol Kaol Ms 0.5 (weak) 0.441(6) 0.441(6) 0.332(x) Ms Kaol Bay Zir 0.497(3) 0.437(6) 0.435(7) 0.330(x) Gibb Nord Or Nord [002] 0.437(5) 0.433(2) 0.329(6) 0.479(x) Qtz Gibb MC(I) Bay [001] 0.426(4) 0.432(2) 0.329(x,5) 0.471(9) MC(M) Dias [020] 0.329(5) 0.471(1) Mona 0.329(4)
123A Mg 0.492 ------Mg-Gly 0.478 0.434 0.434 0.331 K(RT) 0.484 ------K350oC --- 0.434 0.434 --- K550oC 0.508 ------124A Mg 0.494 0.439* 0.439* 0.331 Mg-Gly 0.502,0.484,0.482 ------K(RT) 0.504,0.499 ------K350oC --- 0.435* 0.435* 0.329 K550oC 0.509 0.430 0.430 0.332* 125A Mg 0.498,0.494 0.440* 0.440* --- Mg-Gly 0.482 0.439**,0.437**,0.435** 0.439**,0.437**,0.435** --- K(RT) 0.494 0.439* 0.439* 0.332 K350oC --- 0.435* 0.435* 0.330 K550oC --- 0.440 0.440 0.331** 126A Mg --- 0.441** 0.441** --- Mg-Gly --- 0.438** 0.438** 0.330* K(RT) 0.499 ------0.329 K350oC 0.492 0.438** 0.438** 0.331* K550oC --- 0.437 0.437 ---
312 APPENDIX V-D continued.
Reference Gibb [002] Gibb Gibb Gibb peaks → 0.485(x) 0.432(2) 0.437(5) 0.331(2) Sample Nord Kaol Or Number 0.433(2) 0.437(6) 0.331(x) & Bay Treatments 0.435(7) ↓
Biot Kaol Kaol Ms 0.5 (weak) 0.441(6) 0.441(6) 0.332(x) Ms Kaol Bay Zir 0.497(3) 0.437(6) 0.435(7) 0.330(x) Gibb Nord Or Nord [002] 0.437(5) 0.433(2) 0.329(6) 0.479(x) Qtz Gibb MC(I) Bay [001] 0.426(4) 0.432(2) 0.329(x,5) 0.471(9) MC(M) Dias [020] 0.329(5) 0.471(1) Mona 0.329(4)
123B Mg 0.491 0.435** 0.435** 0.329* Mg-Gly --- 0.431** 0.431** 0.328* K(RT) 0.509,0.494* 0.441*,0.431* 0.441*,0.431* 0.328 K350oC 0.492 0.436* 0.436* 0.330* K550oC 0.498,0.478 0.439, 0.433 0.439, 0.433 --- 124B Mg 0.495,0.493,0.492 0.437** 0.437** 0.330** Mg-Gly 0.492 0.438** 0.438** 0.331* K(RT) --- 0.433 0.433 0.328 K350oC 0.487 0.436* 0.436* 0.330 K550oC 0.496 ------125B Mg 0.488,0.475 0.437*,0.435*,0.432* 0.437*,0.435*,0.432* 0.329 Mg-Gly 0.506 0.434* 0.434 --- K(RT) 0.491,0.487 0.434**,0.429* 0.434** 0.329** K350oC 0.487 0.434** 0.434** 0.329* K550oC 0.496 0.439**,0.435 0.439**,0.435 0.331** 126B Mg 0.496,0.495,0.494,0.492 ------0.332* Mg-Gly 0.492 0.440**,0.436**,0.434**,0.429 0.440**,0.436**,0.434** 0.331* K(RT) 0.498,0.496 0.441** 0.441** --- K350oC 0.491 0.437* 0.437* 0.331* K550oC 0.499 ------
313 APPENDIX V-D continued.
Reference Gibb [002] Gibb Gibb Gibb peaks → 0.485(x) 0.432(2) 0.437(5) 0.331(2) Sample Nord Kaol Or Number 0.433(2) 0.437(6) 0.331(x) & Bay Treatments 0.435(7) ↓
Biot Kaol Kaol Ms 0.5 0.441(6) 0.441(6) 0.332(x) (weak) Kaol Bay Zir Ms 0.437(6) 0.435(7) 0.330(x) 0.497(3) Gibb Nord Or 0.437(5) 0.433(2) 0..329(6) Nord [002] Qtz Gibb MC(I) 0.479(x) 0.426(4) 0.432(2) 0.329(x,5) Bay [001] MC(M) 0.471(9) 0.329(5) Dias [020] Mona 0.471(1) 0.329(4)
300G Mg --- 0.438 0.438 --- Mg-Gly --- 0.438* 0.438* --- K(RT) 0.506 ------K350oC ------K550oC ------300R Mg 0.482 ------0.331, 0.328 Mg-Gly --- 0.438* 0.438* 0.330, 0.328 K(RT) 0.503 0.429 --- 0.328* K350oC 0.495 0.438* 0.438* 0.332, 0.330 K550oC 0.496 0.438 0.438 0.332*** 301G Mg --- 0.440* 0.440* --- Mg-Gly --- 0.439* 0.439* 0.330* K(RT) --- 0.435* 0.435* --- K350oC --- 0.437* 0.437* --- K550oC ------301R Mg 0.482,0.480,0.479 0.438 0.438 0.330 Mg-Gly 0.480,0.479 0.439* 0.439* --- K(RT) 0.477 0.435 0.435 0.330 K350oC --- 0.437 0.437 0.332 K550oC ------304G Mg ------Mg-Gly 0.484 ------K(RT) --- 0.439, 0.433 0.439, 0.433 --- K350oC --- 0.439 0.439 --- K550oC ------304R Mg 0.503,0.498, 0.478,0.477 ------0.331 Mg-Gly --- 0.438,0.436 0.438,0.436 0.331 K(RT) 0.495, 0.479 0.441 0.441 --- K350oC 0.496,0.495 0.439 0.439 --- K550oC 0.503 0.431 0.431 ---
314 APPENDIX V-E
XRD peaks (nm) indicative of nordstrandite in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50-75%; *15-50*. Intensities of less than 15% are not followed by any asterisks.
Nord = nordstrandite; Gibb = gibbsite; Bay = bayerite; Dias = dias; Kaol = kaolinite; Hall = halloysite; Mona = monazite; Or = orthoclase; MC(I) = intermediate microcline; Ms = muscovite.
Reference Nord Nord Nord Nord Nord peaks → [002] 0.433(2) 0.390(2) 0.360(1) 0.302(2) Sample 0.479(x) Number & Gibb Bay Dias Hall Mona Treatments [002] 0.435(7) 0.399(x) 0.362(6) 0.309(x) ↓ 0.485(x) Gibb Kaol Kaol Mona Bay 0.432(2) 0.384 0.358(8) 0.308(8) [001] 0.356(x) Or 0.299(5) 0.471(9) Kaol MC(I) Dias 0.441(6) 0.298(3) [020] Kaol Ms 0.471(1) 0.437(6) 0.299(4) Gibb 0.437(5) 123A Mg ------0.362** --- Mg-Gly 0.478 0.434 --- 0.356** --- K(RT) ------0.358** --- K350oC --- 0.434 ------K550oC ------124A Mg --- 0.439* --- 0.355** --- Mg-Gly 0.482 ------0.362** --- K(RT) ------0.359** --- K350oC --- 0.435* ------K550oC --- 0.430 0.397 ------125A Mg --- 0.440* --- 0.357** --- Mg-Gly 0.482 0.439**,0.437**,0.435** ------K(RT) --- 0.439* ------K350oC --- 0.435* ------K550oC --- 0.440 --- 0.364 --- 126A --- Mg --- 0.441** --- 0.359*,0.355* --- Mg-Gly --- 0.438** 0.398,0.396 0.354** 0.308,0.307,0.303,0.302, K(RT) ------0.357** 0.298 K350oC --- 0.438** ------K550oC --- 0.437 ------315 APPENDIX V-E continued.
Reference Nord Nord Nord Nord Nord peaks → [002] 0.433(2) 0.390 0.360(1) 0.302(2) Sample 0.479(x) (2) Number & Gibb Bay Dias Hall Mona Treatments [002] 0.435(7) 0.399(x) 0.362(6) 0.309(x) ↓ 0.485(x) Gibb Kaol Kaol Mona Bay 0.432(2) 0.384 0.358(8) 0.308(8) [001] 0.356(x) Or 0.471(9) Kaol 0.299(5) Dias 0.441(6) MC(I) [020] Kaol 0.298(3) 0.471(1) 0.437(6) Ms Gibb 0.299(4) 0.437(5)
123B Mg --- 0.435** 0.399,0.397 ------Mg-Gly --- 0.431** 0.396* 0.361**,0.355** --- K(RT) --- 0.441*,0.431* 0.393 0.361** --- K350oC --- 0.436* 0.397* ------K550oC 0.478 0.439, 0.433 ------124B Mg --- 0.437** 0.398 ------Mg-Gly --- 0.438** 0.398 ------K(RT) --- 0.433 0.383 0.363 0.301 K350oC --- 0.436* ------K550oC ------0.363 --- 125B Mg 0.475 0.437*,0.435*,0.432* 0.397,0.393 --- 0.303 Mg-Gly --- 0.434* 0.387 0.363** --- K(RT) --- 0.434**,0.429* 0.397,0.394 0.358* --- K350oC --- 0.434** ------K550oC --- 0.439**,0.435 0.398* ------126B Mg ------0.392 0.355** --- Mg-Gly --- 0.440**,0.436**,0.434**,0.429 --- 0.362**,.357**,0.356** 0.301 K(RT) --- 0.441** --- 0.357** 0.298 K350oC --- 0.437* 0.398 ------K550oC ------
316 APPENDIX V-E continued.
Reference Nord Nord Nord Nord Nord peaks → [002] 0.433(2) 0.390 0.360(1) 0.302(2) Sample 0.479(x) (2) number & Treatments Gibb [002] Bay Dias Hall Mona ↓ 0.485(x) 0.435(7) 0.399 0.362(6) 0.309(x) Bay [001] Gibb (x) Kaol Mona 0.471(9) 0.432(2) Kaol 0.358(8) 0.308(8) Dias [020] 0.384 0.356(x) Or 0.471(1) Kaol 0.299(5) 0.441(6) MC(I) Kaol 0.298(3) 0.437(6) Ms Gibb 0.299(4) 0.437(5)
300G Mg --- 0.438 ------Mg-Gly --- 0.438* ------K(RT) ------0.361** --- K350oC ------0.361** --- K550oC ------300R Mg 0.482 ------0.356** 0.302 Mg-Gly --- 0.438* ------K(RT) --- 0.429 --- 0.362*** --- K350oC --- 0.438* --- 0.356** --- K550oC --- 0.438 0.382 ------301G Mg --- 0.440* ------Mg-Gly --- 0.439* ------K(RT) --- 0.435* ------K350oC --- 0.437* ------K550oC ------301R Mg 0.482,0.480,0.479 0.438 ------Mg-Gly 0.480,0.479 0.439* --- 0.356** --- K(RT) 0.477 0.435 ------K350oC --- 0.437 --- 0.355** --- K550oC ------0.387 ------304G Mg ------0.364** --- Mg-Gly ------0.360** --- K(RT) --- 0.439, 0.433 ------K350oC --- 0.439 --- 0.356** --- K550oC ------304R Mg 0.478,0.477 ------Mg-Gly --- 0.438,0.436 0.397 ------K(RT) 0.479 0.441 --- 0.355* --- K350oC --- 0.439 --- 0.356** --- K550oC --- 0.431 0.387 0.355 ---
317 APPENDIX V-F
(overleaf). XRD peaks (nm) potentially indicative of more than one aluminum hydroxide or aluminum oxyhydroxide in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Data for the diaspore peak near 0.399 (x) nm are shown to help evaluate the peak at 0.471 nm.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Gibb = gibbsite; Nord = nordstrandite; Biot = biotite; Ms = muscovite; Bay = bayerite; Dias = diaspore; Kaol = kaolinite; Qtz = quartz; Vc =, vermiculite.
318 APPENDIX V-F continued.
Reference Gibb [002] Bay Bay [001] Dias peaks → 0.485(x) 0.435(7) 0.471(9) 0.399 Sample Nord [002] Nord Dias [020] (x) number 0.479(x) 0.433(2) 0.471(1) & Gibb Treatments 0.432(2) ↓ Biot Kaol Nord [002] AbL 0.5 (weak) 0.437(6) 0.479(x) 0.403 Ms Gibb Vc (x,6,2) 0.497(3) 0.437(5) 0.457(6) Nord Bay [001] Qtz 0.390(2) 0.471(9) 0.426(4) Dias [020] 0.471(1) 123A Mg 0.492 ------Mg-Gly 0.478 0.434 ------K(RT) 0.484 ------K350oC --- 0.434 ------K550oC 0.508 0.427 ------124A Mg 0.494 0.439* ------Mg-Gly 0.502,0.484,0.482 ------0.406 K(RT) 0.504,0.499 ------K350oC --- 0.435* ------K550oC 0.509 0.430 --- 0.397 125A Mg 0.498,0.494 ------Mg-Gly 0.482 0.439**,0.437**,0.435** 0.472 0.404 K(RT) 0.494 0.439* ------K350oC --- 0.435* ------K550oC ------0.402 126A Mg ------Mg-Gly --- 0.438**,0.426 --- 0.398,0.396 K(RT) 0.499 ------0.406 K350oC 0.492 0.438** ------K550oC --- 0.437 --- 0.402*
319 APPENDIX V-F continued.
Reference Gibb [002] Bay Bay [001] Dias peaks → 0.485(x) 0.435(7) 0.471(9) 0.399 Sample Nord [002] Nord Dias [020] (x) number 0.479(x) 0.433(2) 0.471(1) & Gibb Treatments 0.432(2) ↓
Biot Kaol Nord [002] AbL 0.5 (weak) 0.437(6) 0.479(x) 0.403 Ms Gibb Vc (x,6,2) 0.497(3) 0.437(5) 0.457(6) Nord 0.390(2) Bay [001] Qtz 0.471(9) 0.426(4) Dias [020] 0.471(1)
123B Mg 0.491 0.435** 0.474 0.399,0.397 Mg-Gly --- 0.431** 0.473* 0.410,0.396* K(RT) 0.509,0.494* 0.431* --- 0.410,0.400, K350oC 0.492 0.436* 0.472 0.393 K550oC 0.498, 0.478 0.439, 0.425,0.433 --- 0.397* 0.402* 124B Mg 0.495,0.493,0.492 0.437** --- 0.398 Mg-Gly 0.492 0.438** --- 0.398 K(RT) --- 0.433 --- 0.410, 0.383 K350oC 0.487 0.436* ------K550oC 0.496 ------125B Mg 0.488, 0.475 0.437*,0.435*,0.432* 0.475 0.409?,0.397, shared with 0.393 Nord 0.479(x) 0.402*,0.387 Mg-Gly 0.506 0.434* --- 0.397, 0.394 K(RT) 0.491,0.487 0.434**,0.429* ------K350oC 0.487 0.434** --- 0.401,0.398* K550oC 0.496 0.439**,0.435 --- 126B Mg 0.496,0.495,0.494,0.492 ------0.400, 0.392 Mg-Gly 0.492 0.436**,0.434**,0.429 0.474,0.473 --- K(RT) 0.498,0.496 0.426 --- 0.404,0.403 K350oC 0.491 0.437* --- 0.408,0.398 K550oC 0.499 0.426* ------
320 APPENDIX V-F continued.
Reference Gibb [002] Bay Bay [001] Dias peaks → 0.485(x) 0.435(7) 0.471(9) 0.399 Sample Nord [002] Nord Dias [020] (x) number 0.479(x) 0.433(2) 0.471(1) & Gibb Treatments 0.432(2) ↓
Biot 0.5 Kaol Nord [002] AbL (weak) 0.437(6) 0.479(x) 0.403 Ms 0.497(3) Gibb Vc (x,6,2) Bay [001] 0.437(5) 0.457(6) Nord 0.471(9) Qtz 0.390(2) Dias [020] 0.426(4) 0.471(1)
300G Mg --- 0.438 0.469 --- Mg-Gly --- 0.438* 0.469 --- K(RT) 0.506 ------K350oC ------K550oC ------300R Mg 0.482 ------Mg-Gly --- 0.438* 0.468 --- K(RT) 0.503 0.429 --- 0.403 K350oC 0.495 0.438*,0.428 --- 0.403 K550oC 0.496 0.438 --- 0.382 301G Mg ------0.474 --- Mg-Gly --- 0.439* ------K(RT) --- 0.435* ------K350oC --- 0.437* ------K550oC ------301R Mg 0.482,0.480,0.479 0.438 --- 0.402 Mg-Gly 0.480, 0.479 0.439* 0.470 --- K(RT) 0.477 0.435 ------K350oC --- 0.437 ------K550oC --- 0.425 --- 0.387 304G Mg ------Mg-Gly 0.484 --- 0.470 --- K(RT) --- 0.439, 0.433 ------K350oC --- 0.439 ------K550oC ------304R Mg 0.503,0.498, ------Mg-Gly 0.478,0.477 0.438,0.436, 0.425 --- 0.397 K(RT) ------0.467 --- K350oC 0.495, 0.479 0.439 ------K550oC 0.496,0.495 0.431, 0.426 --- 0.387 0.503
321 APPENDIX V-G
XRD peaks (nm) indicative of pseudoboehmite and boehmite in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Psbm = pseudoboehmite; Kaol = kaolinite; AbL = low albite; Bm = boehmite; Biot = biotite; Ms = muscovite; Gibb = gibbsite.
Reference peaks Psbm Bm [020] Bm → 0.64-0.69 0.611(x) 0.316(6) Sample number Kaol AbL AbL & 0.717(x) 0.639(2) 0.319 (x,6) Treatments 0.710(x) (002)? Ms ↓ AbL Biot 0.5 0.319(3) 0.639(2) (weak) Gibb (002)? 0.319(1) AbL 0.315(5,3) 123A Mg ------Mg-Gly 0.708*** ------K(RT) ------0.319 K350oC 0.699*** ------K550oC ------124A Mg 0.719***,0.713*** --- 0.316* Mg-Gly ------K(RT) ------K350oC 0.702*** ------K550oC ------125A Mg 0.722*** --- 0.317 Mg-Gly 0.705*** --- 0.318,0.316*,0.314 K(RT) 0.713*** --- 0.316 K350oC 0.702*** --- 0.314 K550oC ------0.317** 126A Mg ------0.317 Mg-Gly 0.713***,0.710***,0.705*** --- 0.316* K(RT) ------0.318** K350oC 0.713*** --- 0.317, 0.314* K550oC ------0.318*
322 APPENDIX V-G continued.
Reference Psbm Bm [020] Bm peaks → 0.64-0.69 0.611(x) 0.316(6) Sample number & Kaol AbL AbL Treatments 0.717(x) 0.639(2) 0.319 (x,6) ↓ 0.710(x) (002)? Ms AbL Biot 0.5 0.319(3) 0.639(2) (weak) Gibb (002)? 0.319(1) AbL 0.315(5,3)
123B Mg 0.722***,0.710*** --- 0.317*,0.316*,0.315*,0.314* Mg-Gly 0.710*** 0.545,0.518 0.315* K(RT) --- 0.512 0.319 K350oC 0.708*** --- 0.314* K550oC ------0.318** 124B Mg 0.716*** --- 0.316* Mg-Gly 0.713*** --- 0.317** K(RT) --- 0.511 --- K350oC 0.708*** --- 0.315* K550oC --- 0.634 0.317*** 125B Mg 0.716***,0.708*** --- 0.314** Mg-Gly ------K(RT) 0.725***,0.713***,0.702*** --- 0.314 K350oC 0.705*** --- 0.316* K550oC ------0.319*,0.317* 126B Mg 0.716*** --- 0.317* Mg-Gly 0.713*** --- 0.317*** K(RT) ------0.318* K350oC 0.708*** --- 0.318*,0.316* K550oC ------
323 APPENDIX V-G continued.
Reference peaks Psbm Bm [020] Bm → 0.64-0.69 0.611(x) 0.316(6) Sample number & Kaol AbL AbL Treatments 0.717(x) 0.639(2) 0.319 (x,6) ↓ 0.710(x) (002)? Ms AbL Biot 0.5 0.319(3) 0.639(2) (weak) Gibb (002)? 0.319(1) AbL 0.315(5,3)
300G Mg 0.710*** ------Mg-Gly 0.713*** ------K(RT) ------K350oC ------K550oC ------300R Mg 0.716*** ------Mg-Gly 0.708*** --- 0.319 K(RT) --- 0.594 --- K350oC 0.708*** ------K550oC ------0.317,0.316 301G Mg 0.719***,0.716***,0.710*** ------Mg-Gly 0.708*** ------K(RT) 0.716***,0.708*** ------K350oC 0.708*** ------K550oC ------301R Mg 0.713*** ------Mg-Gly 0.710*** --- 0.318 K(RT) 0.708*** --- 0.316 K350oC 0.713***,0.710*** ------K550oC ------304G Mg ------Mg-Gly 0.728*** ------K(RT) 0.706*** ------K350oC 0.713*** ------K550oC ------304R Mg ------Mg-Gly 0.702*** ------K(RT) 0.716*** ------K350oC 0.713*** ------K550oC ------
324 APPENDIX V-H
(overleaf). XRD peaks (nm) indicative of diaspore in oriented specimens of the clay- sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Peaks attributable to bayerite, nordstrandite and gibbsite in the interval 0.435 nm to 0.432 nm are also shown to help evaluate the peaks of diaspore and bayerite at 0.471 nm.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Gibb = gibbsite; Nord = nordstrandite; Bay = bayerite; Kaol = kaolinite; Qtz = quartz; Dias = diaspore; AbL = low albite; Vc = vermiculite.
325 APPENDIX V-H continued.
Reference peaks → Dias Dias [020] Bay Sample 0.399 0.471(1) 0.435(7) number (x) Bay [001] Nord & 0.471(9) 0.433(2) Treatments Gibb ↓ 0.432(2)
AbL Nord [002] Kaol 0.403 0.479(x) 0.441(6), 0.437(6) (x,6,2) Vc Gibb Nord 0.457(6) 0.437(5) 0.390(2) Qtz 0.426(4) 123A Mg ------Mg-Gly ------0.434 K(RT) ------K350oC ------0.434 K550oC ------124A Mg ------0.439* Mg-Gly 0.406 ------K(RT) ------K350oC ------0.435* K550oC 0.397 --- 0.430 125A Mg ------0.440* Mg-Gly 0.404 0.472 0.439**,0.437**,0.435** K(RT) ------0.439* K350oC ------0.435* K550oC 0.402 --- 0.440 126A Mg ------0.441** Mg-Gly 0.398,0.396 --- 0.438** K(RT) 0.406 ------K350oC ------0.438** K550oC 0.402* --- 0.437
326 APPENDIX V-H continued.
Reference peaks Dias Dias [020] Bay → 0.399 0.471(1) 0.435(7) Sample (x) Bay [001] Nord number 0.471(9) 0.433(2) & Gibb Treatments 0.432(2) ↓
AbL Nord [002] Kaol 0.403 0.479(x) 0.441(6), 0.437(6) (x,6,2) Vc Gibb Nord 0.457(6) 0.437(5) 0.390(2) Qtz 0.426(4)
123B Mg 0.399,0.397 0.474 0.435** Mg-Gly 0.410,0.396* 0.473* 0.431** K(RT) 0.410,0.400, 0.393 --- 0.441*,0.431* K350oC 0.397* 0.472 0.436* K550oC 0.402* --- 0.439, 0.433 124B Mg 0.398 --- 0.437** Mg-Gly 0.398 --- 0.438** K(RT) 0.410, 0.383 --- 0.433 K350oC ------0.436* K550oC ------125B Mg 0.409?,0.397, 0.393 0.475 0.437*,0.435*,0.432* Mg-Gly 0.402*,0.387 --- 0.434* K(RT) 0.397, 0.394 --- 0.434**,0.429* K350oC ------0.434** K550oC 0.401,0.398* --- 0.439**,0.435 126B Mg 0.400, 0.392 ------Mg-Gly --- 0.474,0.473 0.440**,0.436**,0.434**,0.429 K(RT) 0.404,0.403 --- 0.441** K350oC 0.408,0.398 --- 0.437* K550oC ------
327 APPENDIX V-H continued.
Reference peaks → Dias Dias [020] Bay Sample 0.399 0.471(1) 0.435(7) number (x) Bay [001] Nord & 0.471(9) 0.433(2) Treatments Gibb ↓ 0.432(2)
AbL Nord [002] Kaol 0.403 0.479(x) 0.441(6), 0.437(6) (x,6,2) Vc Gibb Nord 0.457(6) 0.437(5) 0.390(2) Qtz 0.426(4)
300G Mg --- 0.469 0.438 Mg-Gly --- 0.469 0.438* K(RT) ------K350oC ------K550oC ------300R Mg ------Mg-Gly --- 0.468 0.438* K(RT) 0.403 --- 0.429 K350oC 0.403 --- 0.438* K550oC 0.382 --- 0.438 301G Mg --- 0.474 0.440* Mg-Gly ------0.439* K(RT) ------0.435* K350oC ------0.437* K550oC ------301R Mg 0.402 --- 0.438 Mg-Gly --- 0.470 0.439* K(RT) ------0.435 K350oC ------0.437 K550oC 0.387 ------304G Mg ------Mg-Gly --- 0.470 --- K(RT) ------0.439, 0.433 K350oC ------0.439 K550oC ------304R Mg ------Mg-Gly 0.397 --- 0.438,0.436 K(RT) --- 0.467 0.441 K350oC ------0.439 K550oC 0.387 --- 0.431
328 APPENDIX V-I
XRD peaks (nm) indicative of plagioclase feldspar low albite in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: *** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
AbL = low albite; Psbm = pseudoboehmite; Bm = boehmite; Nord = Nordstrandite; Dias = diaspore; MC(I) = intermediate microcline; Or = orthoclase; Hall = halloysite; HA = hydroxy apatite.
Reference AbL AbL AbL AbL AbL peaks → 0.639(2) 0.403 0.378(3) 0.368(2) 0.315 Sample (x,6,2) 0.366 (5,3) number Psbm MC(I) (6,3,2) & 0.64-0.69 Nord 0.379(4) Bm Treatments Bm[020] 0.416(2) Or MC(I) 0.316(6) ↓ 0.611(x) Dias 0.377(8) 0.375(4) HA 0.399(x) 0.374(1) 0.311(2) Hall 0.362(6)
123A Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------124A Mg ------0.316* Mg-Gly --- 0.406 ------K(RT) ------K350oC ------K550oC --- 0.397 ------125A Mg ------0.317 Mg-Gly --- 0.404 ------0.316*,0.314 K(RT) ------0.316 K350oC ------0.314 K550oC --- 0.402 --- 0.364 0.317** 126A Mg ------0.317 Mg-Gly --- 0.398,0.396 ------0.316* K(RT) --- 0.406 0.377 ------K350oC ------0.317,0.314* K550oC --- 0.402* 0.376 ------
329 APPENDIX V-I continued
Reference AbL AbL AbL AbL AbL peaks → 0.639(2) 0.403 0.378(3) 0.368(2) 0.315 Sample (x,6,2) 0.366 (5,3) number Psbm MC(I) (6,3,2) & 0.64-0.69 Nord 0.379(4) Bm Treatments Bm[020] 0.416(2) Or MC(I) 0.316(6) ↓ 0.611(x) Dias 0.377(8) 0.375(4) HA 0.399(x) 0.374(1) 0.311(2) Hall 0.362(6)
123B Mg --- 0.399,0.397 ------0.317*,,0.316*,0.315*,0.314* Mg-Gly --- 0.410, 0.396* ------0.315* K(RT) --- 0.410*,0.400 ------0.311 K350oC --- 0.397* ------0.314* K550oC --- 0.402* 0.377 0.367 --- 124B Mg --- 0.398 --- 0.372 0.316* Mg-Gly --- 0.398 ------0.317** K(RT) --- 0.410 0.383 0.371 --- K350oC ------0.315* K550oC 0.634 ------0.367 0.317*** 125B Mg --- 0.416,0.409, ------0.314** Mg-Gly --- 0.397 --- 0.365** --- K(RT) --- 0.402* ------0.314 K350oC --- 0.397 ------0.316* K550oC ------0.366 0.317* 0.401, 0.398* 126B Mg --- 0.400 ------0.317* Mg-Gly ------0.317***,0.312* K(RT) --- 0.404,0.403 ------K350oC --- 0.408, 0.398 ------K550oC --- 0.407,0.404 0.377 ---
330 APPENDIX V-I continued
Reference AbL AbL AbL AbL AbL peaks → 0.639(2) 0.403 0.378(3) 0.368(2) 0.315 Sample (x,6,2) 0.366 (5,3) number Psbm MC(I) (6,3,2) & 0.64-0.69 Nord 0.379(4) Bm Treatments Bm [020] 0.416 Or MC(I) 0.316(6) ↓ 0.611(x) (2) 0.377(8) 0.375(4) HA Dias 0.374(1) 0.311(2) 0.399 Hall (x) 0.362(6) 300G Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------300R Mg ------Mg-Gly ------0.379 ------K(RT) --- 0.403 ------K350oC --- 0.403 0.381 ------K550oC ------0.382 --- 0.317,0.316 301G Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------301R Mg --- 0.402 ------Mg-Gly ------K(RT) ------0.316 K350oC ------K550oC ------304G Mg ------0.364** --- Mg-Gly ------K(RT) ------K350oC ------K550oC ------304R Mg ------0.365** --- Mg-Gly --- 0.397 ------K(RT) ------K350oC ------K550oC ------
331 APPENDIX V-J
(overleaf). XRD peaks (nm) indicative of potassium feldspars orthoclase and microcline in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
MC(I) = intermediate microcline; MC(M) = maximum microcline; Or = orthoclase; Nord = Nordstrandite; Qtz = quartz; Kaol = kaolinite; AbL = low albite; Mona = monazite; HA = hydroxy apatite.
332 APPENDIX V-J continued.
Reference MC(I) MC(I) Or MC(I) MC(I) MC(M) peaks → 0.423(6), 0.422(5) 0.380(2) 0.377(8) 0.375(4) 0.348(2) 0.326(8) Sample MC(M) MC(I) 0.374(1) 0.347(5) 0.325(x,8) number 0.422(x), 0.421(5) 0.379(4) Or Or & Or 0.347(5) 0.324(7) Treatments 0.422(7) MC(I) ↓ Nord 0.324(x) 0.422(2)
Qtz Kaol AbL Or AbL Or 0..329(6) 0.426(4) 0.384 0.378(3) 0.377(8) 0.351(1) MC(I) 0.329(x,5) Kaol AbL MC(I) AbL Mona Mona 0.329(4) 0.419(5) 0.378(3) 0.375(4) 0.368(2) 0.351(3) AbL 0.322(7) 0.374(1) 0.366 HA (6,3,2) 0.345(4) Nord 0.345(1)
123A Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------0.322* 124A Mg ------0.343 --- Mg-Gly ------0.326 K(RT) ------0.325 K350oC ------0.329 K550oC ------0.326* 125A Mg ------0.344 0.322 Mg-Gly ------K(RT) ------K350oC ------K550oC ------0.323* 126A Mg ------0.345* 0.323* Mg-Gly 0.426 ------0.327 K(RT) ------0.377 ------0.329,0.324 K350oC ------0.325 K550oC ------0.376 0.376 0.347 0.322*
333 APPENDIX V-J continued.
Reference MC(I) MC(I) Or MC(I) MC(I) MC(M) peaks → 0.423(6), 0.422(5) 0.380(2) 0.377(8) 0.375(4) 0.348(2) 0.326(8) Sample MC(M) MC(I) 0.374(1) 0.347(5) 0.325(x,8) number 0.422(x), 0.421(5) 0.379(4) Or Or & Or 0.347(5) 0.324(7) Treatments 0.422(7) MC(I) ↓ Nord 0.324(x) 0.422(2)
Qtz Kaol AbL Or AbL Or 0.426(4) 0.384 0.378(3) 0.377(8) 0.351(1) 0..329(6) Kaol AbL MC(I) AbL Mona MC(I) 0.419(5) 0.378(3) 0.375(4) 0.368(2) 0.351(3) 0.329(x,5) 0.374(1) 0.366 HA Mona (6,3,2) 0.345(4) 0.329(4) Nord AbL 0.345(1) 0.322(7)
123B Mg ------0.329* Mg-Gly ------0.328* K(RT) ------0.328, 0.322** K350oC ------K550oC 0.425 --- 0.377 0.375,0.374 --- 0.324, 0.322 124B Mg ------0.372 ------Mg-Gly ------K(RT) --- 0.383 --- 0.371 --- 0.323** K350oC ------K550oC 0.422 --- 0.376 0.376 --- 0.323 125B Mg ------0.329 Mg-Gly 0.420 ------0.324, 0.322 K(RT) ------0.349* 0.329** K350oC ------0.329* K550oC 0.420* ------0.374* --- 0.322 126B Mg ------Mg-Gly 0.420 ------K(RT) ------0.376 0.376 --- 0.323 K350oC ------0.374* ------K550oC ------0.377 --- 0.349 0.324*
334 APPENDIX V-J continued.
Reference MC(I) MC(I) Or MC(I) MC(I) MC(M) peaks → 0.423(6) 0.380(2) 0.377(8) 0.375(4) 0.348(2) 0.326(8) Sample 0.422(5) MC(I) 0.374(1) 0.347(5) 0.325(x,8) number MC(M) 0.379(4) Or Or & 0.422(x) 0.347(5) 0.324(7) Treatments 0.421(5) MC(I) ↓ Or 0.324(x) 0.422(7) Nord 0.422(2)
Qtz Kaol AbL Or AbL Or 0.426(4) 0.384 0.378(3) 0.377(8) 0.351(1) 0..329(6) Kaol AbL MC(I) AbL Mona MC(I) 0.419(5) 0.378(3) 0.375(4) 0.368(2) 0.351(3) 0.329(x,5) 0.374(1) 0.366 HA Mona (6,3,2) 0.345(4) 0.329(4) Nord 0.345(1) AbL 0.322(7) 300G Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------300R Mg ------0.344** 0.328,0.323* Mg-Gly --- 0.379 ------0.328 K(RT) ------0.346*,0.345* 0.328* K350oC --- 0.381 ------0.322 K550oC 0.420* 0.382 ------0.322* 301G Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC ------301R Mg ------0.344,0.343 --- Mg-Gly ------K(RT) ------K350oC ------0.323 K550oC 0.425 ------0.326* 304G Mg ------Mg-Gly ------K(RT) ------K350oC ------0.323 K550oC ------304R Mg ------Mg-Gly 0.425,0.423 ------K(RT) 0.420* ------0.323 K350oC ------0.323 K550oC 0.426 ------0.326**
335 APPENDIX V-K
XRD peaks (in nm) indicative of quartz in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 30 degrees as follows: * ** 75-100%; ** 50- 75%; *15-50. Intensities of less than 15% are not followed by any asterisks.
Qtz = quartz; Gibb = gibbsite; MC(I) = intermediate microcline; Biot = biotite; Ms = muscovite.
Reference Qtz Qtz peaks → 0.426(4) 0.334(x) Sample MC(I) number Gibb 0.334(5) & 0.432(2) Treatments MC(I) Biot ↓ 0.423(6) 0.337(x) Ms 0.332(x) 123A Mg ------Mg-Gly ------K(RT) ------K350oC 0.434 --- K550oC 0.427 0.337**,0.335** 124A Mg --- 0.336 Mg-Gly --- 0.337 K(RT) --- 0.335 K350oC ------K550oC 0.430 0.337**,0.332* 125A Mg --- 0.335 Mg-Gly ------K(RT) --- 0.332 K350oC ------K550oC ------126A Mg --- 0.333 Mg-Gly 0.426 --- K(RT) --- 0.336 K350oC ------K550oC --- 0.334**
336 APPENDIX V-K continued.
Reference Qtz Qtz peaks → 0.426(4) 0.334(x) Sample MC(I) number 0.334(5) & Treatments Gibb Biot ↓ 0.432(2) 0.337(x) MC(I) Ms 0.423(6) 0.332(x) 123B Mg ------Mg-Gly 0.431** 0.338 K(RT) 0.431* --- K350oC ------K550oC 0.433,0.425 0.334** 124B Mg ------Mg-Gly ------K(RT) 0.433 --- K350oC ------K550oC 0.422 0.333* 125B Mg 0.432* --- Mg-Gly 0.434*,0.420 0.337 K(RT) 0.434**,0.429* 0.335, 0.333 K350oC 0.434** --- K550oC 0.420* --- 126B Mg --- 0.332* Mg-Gly 0.434**,0.429,0.426,0.420 --- K(RT) --- 0.335*,0.334* K350oC ------K550oC 0.426* 0.335**
337 APPENDIX V-K continued.
Reference Qtz Qtz peaks → 0.426(4) 0.334(x) Sample MC(I) number 0.334(5) & Treatments Gibb Biot ↓ 0.432(2) 0.337(x) MC(I) Ms 0.423(6) 0.332(x) 300G Mg ------Mg-Gly ------K(RT) --- 0.337 K350oC ------K550oC --- 0.337* 300R Mg --- 0.333 Mg-Gly ------K(RT) 0.429 0.338* K350oC 0.428 0.335*,0.334*0.332 K550oC 0.420* 0.332*** 301G Mg ------Mg-Gly ------K(RT) ------K350oC ------K550oC --- 0.334*** 301R Mg ------Mg-Gly --- 0.333 K(RT) --- 0.337 K350oC --- 0.335, 0.332 K550oC 0.425 0.336*** 304G Mg ------Mg-Gly ------K(RT) 0.433 --- K350oC ------K550oC --- 0.336*** 304R Mg ------Mg-Gly 0.425, 0.423 --- K(RT) 0.420* --- K350oC --- 0.334 K550oC 0.431,0.426 0.336***
338 APPENDIX V-L
XRD peaks (nm) indicative of hydroxy apatite, monazite, and allanite in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
HA = hydroxy apatite; AbL = low albite; Mona = monazite; Nord = nordstrandite; Kaol = kaolinite; All = allanite.
Reference HA Mona Mona All peaks → 0.311(2) 0.417(3) 0.309(x) 0.353(5) Sample Mona number 0.308(8) & Treatments AbL Kaol HA Kaol ↓ 0.315 0.419(5) 0.311(2) 0.358(8) (5,3) Nord Nord 0.356(x) Mona 0.416(2) 0.302(2) AbL 0.309(x) 0.351(1) Mona Mona 0.308(8) 0.351(3)
123A Mg ------Mg-Gly ------0.356** K(RT) ------0.358** K350oC ------0.352** K550oC ------124A Mg ------0.355** Mg-Gly ------K(RT) ------0.359** K350oC ------0.352** K550oC ------125A Mg ------0.357** Mg-Gly 0.314 ------0.354** K(RT) ------0.354** K350oC 0.314 ------0.352** K550oC ------126A Mg ------0.359*,0.355* Mg-Gly --- 0.417 --- 0.354** K(RT) 0.308,0.307 --- 0.308,0.307, 0.303 0.357** K350oC 0.314* ------0.353**,0.352** K550oC --- 0.418 ------
339 APPENDIX V-L continued.
Reference HA Mona Mona All peaks → 0.311(2) 0.417(3) 0.309(x) 0.353(5) Sample Mona number 0.308(8) & Treatments AbL Kaol HA Kaol ↓ 0.315 0.419(5) 0.311(2) 0.358(8) (5,3) Nord Nord 0.356(x) Mona 0.416(2) 0.302(2) AbL 0.309(x) 0.351(1) Mona 0.351(3)
123B Mg 0.315*,0.314* ------0.352** Mg-Gly 0.315* 0.410 --- 0.355** K(RT) 0.311 0.410* 0.311 --- K350oC 0.314* ------0.354** K550oC ------124B Mg ------0.354** Mg-Gly ------0.354** K(RT) --- 0.410 0.301 0.353**,0.352** K350oC 0.315* ------K550oC ------125B Mg 0.314** 0.418,0.416, 0.303 0.354 Mg-Gly --- 0.409 --- 0.354 K(RT) 0.314 0.420 --- 0.358*,0.354* K350oC --- 0.418,0.415 --- 0.352** K550oC ------0.420* 126B Mg ------0.355** Mg-Gly 0.312* 0.420,0.416 0.312*,0.301 0.357**,0.356** K(RT) ------0.357** K350oC ------0.353** K550oC ------
340 APPENDIX V-L continued.
Reference HA Mona Mona All peaks → 0.311(2) 0.417(3) 0.309(x) 0.353(5) Sample Mona number 0.308(8) & Treatments AbL Kaol HA Kaol ↓ 0.315 0.419(5) 0.311(2) 0.358(8) (5,3) Nord Nord 0.356(x) Mona 0.416(2) 0.302(2) AbL 0.309(x) 0.351(1) Mona 0.351(3)
300G Mg ------0.354** Mg-Gly ------0.354** K(RT) ------K350oC ------K550oC ------300R Mg 0.302 --- 0.302 0.356** Mg-Gly --- 0.415 --- 0.352** K(RT) ------K350oC --- 0.419,0.417 --- 0.356** K550oC --- 0.420* ------301G Mg ------0.354** Mg-Gly ------0.354** K(RT) ------0.354** K350oC ------0.354** K550oC ------301R Mg --- 0.419 --- 0.354** Mg-Gly ------0.356** K(RT) ------0.353** K350oC ------0.355** K550oC ------304G Mg ------Mg-Gly ------K(RT) ------0.354** K350oC ------0.356** K550oC ------304R Mg ------0.354* Mg-Gly ------0.354** K(RT) --- 0.420* --- 0.355* K350oC ------0.356** K550oC ------0.355 ,0.353
341 APPENDIX V-M
(overleaf). XRD peaks (nm) indicative of zircon in oriented specimens of the clay-sized fraction of saprolite.
Peaks considered to provide definitive identification are shown in bold.
Reference XRD spacings of minerals that most closely match those of the samples are shown at the top of each column. Intensity of reference diffraction peaks as a percentage of their most intense peak approximated to the tens place is given in round parenthesis. The most intense peak is denoted as (x). Square parenthesis refers to the diffraction plane within the mineral.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range of 0 to 60 degrees as follows: * ** 75-100%; ** 50- 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
Zir = zircon; Hall = halloysite; Kaol = kaolinite; Gibb = gibbsite; Ms = muscovite; Or = orthoclase; MC(I) = intermediate microcline; MC(M) = maximum microcline; Mona = monazite.
342 APPENDIX V-M continued.
Reference Zir Zir peaks → 0.443(5) 0.330(x) Sample number Hall Ms & 0.445 0.332(x) Treatments Hall Or ↓ 0.442(x) 0.331(x) Kaol Gibb 0.441(6) 0.331(2) Kaol MC(I) 0.437(6) 0.329(x,5) Gibb MC(M) 0.437(5) 0.329(5) Or 0.329(6) Mona 0.329(4) 123A Mg 0.444 --- Mg-Gly --- 0.331 K(RT) 0.446,0.443 --- K350oC ------K550oC ------124A Mg 0.439* 0.331 Mg-Gly ------K(RT) 0.447* --- K350oC --- 0.329 K550oC --- 0.332* 125A Mg 0.440* --- Mg-Gly 0.439**, 0.437** --- K(RT) 0.439* 0.332 K350oC --- 0.330 K550oC 0.440 0.331** 126A Mg 0.441** 0.333 Mg-Gly 0.438** 0.330* K(RT) 0.446** 0.329 K350oC 0.438** 0.331* K550oC 0.437 ---
343 APPENDIX V-M continued.
Reference Zir Zir peaks → 0.443(5) 0.330(x) Sample number & Treatments Hall Ms ↓ 0.445 0.332(x) Hall Or 0.442(x) 0.331(x) Kaol Gibb 0.441(6) 0.331(2) Kaol MC(I) 0.437(6) 0.329(x,5) Gibb MC(M) 0.437(5) 0.329(5) Or 0..329(6) Mona 0.329(4)
123B Mg --- 0.329* Mg-Gly --- 0.328* K(RT) 0.447**, 0.445**, 0.441* 0.328 K350oC 0.436* 0.330* K550oC 0.439 --- 124B Mg 0.437** 0.330** Mg-Gly 0.438** 0.331* K(RT) 0.442 0.328 K350oC 0.436* 0.330 K550oC --- 0.333* 125B Mg 0.437* 0.329 Mg-Gly ------K(RT) --- 0.333, 0.329** K350oC --- 0.329* K550oC 0.439** 0.331** 126B Mg --- 0.332* Mg-Gly 0.440**, 0.436** 0.331* K(RT) 0.445**, 0.441** --- K350oC 0.437* 0.331* K550oC 0.445 ---
344 APPENDIX V-M continued.
Reference Zir Zir peaks → 0.443(5) 0.330(x) Sample number & Treatments Hall Ms ↓ 0.445 0.332(x) Hall Or 0.442(x) 0.331(x) Kaol Gibb 0.441(6) 0.331(2) Kaol MC(I) 0.437(6) 0.329(x,5) Gibb MC(M) 0.437(5) 0.329(5) Or 0. 329(6) Mona 0.329(4) 300G Mg 0.438 --- Mg-Gly 0.438* --- K(RT) ------K350oC 0.445 --- K550oC ------300R Mg 0.442 0.331, 0.328 Mg-Gly 0.438* 0.330, 0.328 K(RT) --- 0.328* K350oC 0.438* 0.330 K550oC 0.438 --- 301G Mg 0.440* --- Mg-Gly 0.439* 0.330* K(RT) ------K350oC 0.437* --- K550oC ------301R Mg 0.438 0.330 Mg-Gly 0.439* --- K(RT) --- 0.330 K350oC 0.437 --- K550oC ------304G Mg ------Mg-Gly 0.446* --- K(RT) 0.439 --- K350oC 0.439 --- K550oC ------304R Mg --- 0.331 Mg-Gly 0.438, 0.436 0.331 K(RT) 0.441 --- K350oC 0.439 --- K550oC ------
345 APPENDIX VI
(Overleaf). XRD PEAKS ATTRIBUTABLE TO PRIMARY REFLECTIONS FROM THE [001] PLANE OF HALLOYSITE AND KAOLINITE IN THE SAND-, SILT-, AND CLAY- SIZED FRACTIONS OF ISOVOLUMETRICALLY WEATHERED SAPROLITE.
Approximate peak intensities in the samples are expressed in relation to the most intense peak found in each sample in the entire 2θ range (0 to 60 degrees for sand- and silt-sized samples and 0 – 30 degrees for clay-sized samples) as follows: *** 75-100%; ** 50 - 75%; * 15-50. Intensities of less than 15% are not followed by any asterisks.
1 From randomly-oriented specimens. 2 From oriented specimens. 3 Separate slides were used for the Mg- saturated samples and the Mg-glycerolated samples. 4 Slide used for the K-550oC treatment is different from that used for the other K-RT and K- 350oC. 5 Slide used for the K(RT) treatment is different from that used for the K-350oC and K-550oC treatments.
RT = room temperature; Gly = glycerol.
346 APPENDIX VI continued.
SAND 1 SILT 1 CLAY 2,3 Treatment → Na Na Mg Mg-Gly K K K Sample (RT) 350oC 550oC Number↓ 123A 0.734 0.713 0.745 0.708 0.727 0.699 --- *** *** *** *** *** 0.737 *** 124A --- 0.713 0.719 0.740 0.734 0.702 --- *** *** *** *** *** 0.713 0.734 *** *** 0.706 ***
125A --- 0.707 0.722 0.705 0.713 0.702 --- 4 *** *** *** *** ***
126A --- 0.737 0.728 0.713 0.737 0.713 --- *** ** *** *** *** 0.710 *** 0.705 ***
123B 0.650 0.743 0.722 0.710*** 0.786 0.708 --- *** *** *** *** 0.740 0.710 0.766 *** *** *** 0.731 0.746 *** *** 124B --- 0.719 0.716 0.713 0.772 0.708 --- ** *** *** *** *** 0.702 0.756 ** *** 125B 0.673 0.708 0.716 0.756 0.725 0.705 --- * ** *** *** *** *** 0.708 0.752 0.713 *** *** *** 0.702 *** 126B --- 0.737 0.716 0.713 0.728 0.708 --- *** *** *** *** ***
347 APPENDIX VI continued.
SAND 1 SILT 1 CLAY 2
Treatment → Na Na Mg Mg-Gly K K K Sample (RT) 350oC 550oC Number↓ 300G 0.646 0.713 0.710 0.713 0.736 0.734 --- *** *** *** ** *** 0.702 ***
300R --- 0.710 0.716 0.708 0.749 0.708 --- *** *** *** *** 0.740 ***
301G ------0.719 0.708 0.716 0.708 --- *** *** *** *** 0.716 0.708 *** *** 0.710 ***
301R --- 0.752 0.713 0.710 0.708 0.713 --- * *** *** *** *** 0.743 0.710 * ***
304G --- 0.713 0.759 0.728 0.706 5 0.713 --- *** *** *** *** *** 0.708 *** 0.705 ***
304R 0.646 0.705 0.752 0.702 0.716 0.713 --- * *** *** *** *** 0.699 *
348