'A
THESIS
entitled
REGIONAL GEOCHEMICAL VARIATIONS RELATED
TO BASE METAL MINERALIZATION IN WALES
submitted for the degree of
DOCTOR OF PHILOSOPHY in the FACULTY OF SCIENCE OF THE UNIVERSITY OF LONDON
by
FERNANDO URQUIDI-BARRAU
Royal School of Mines June 1973 Imperial College of Science and Technology (I)
ABSTRACT
Regional geochemical variations from a multi-element stream- sediment reconnaissance survey carried out in the Principality of Wales are described and investigated in relation to base-metal mineralization. A total of 9,910 drainage sediment samples collected at a density of one sample per square mile were analysed by a direct reading emission spectrophotometer, atomic absorption and colorimetric methods for more than twenty elements, of which sixteen were selected as possible indicators of mineralized areas.
A moving average technique was employed to smooth errors in- herent in the data. The use of percentile class limits was evaluated as a means of data presentation and filter mapping techniques were also applied in delineating anomalous areas.
It was recognized that the trace-element distribution reflected known geological and secondary features, as well as mining and mineralization. R-mode factor analysis was applied as a method of elucidating element associations from which the various controlling features were interpreted. R-scores were plotted as smooth map- forms with percentile class limits, delineating the distribution of these controlling features as defined by the element associations.
Selection of areas for detailed study was based on the coincidence of favourable geological environments for mineralization with low-order regional geochemical anomalies for single elements, or combinations of metals. Detailed geochemical studies in North Pembrokeshire and Carmarthenshire related marginal regional anomalies of copper, lead and zinc to the presence of undisturbed mineralization, and in Anglesey, glacial dispersion was found to contribute to the size of the anomaly due to the Parys-Mona mineralization.
It was shown that multi-element reconnaissance geochemical drainage surveys could be successfully used as mineral exploration tool in areas remote from former mining and industrial activities provided that the interpretation was made on smoothed data. Interpretation based on the geological environment and smoothed element maps was aided by the use of R-mode factor analysis for the classification of metal associations in terms of the controlling features. ( i i
ACKNOWLEDGEMENTS
The project described in this thesis forms part of an
Applied Geochemistry Research Group programme on the interpretation
of the Geochemical Atlas of England and Wales, financed by the
Wolfson Foundation.
Grateful thanks are given to the British Council for
providing the writer with generous financial support.
The author particularly expresses his gratitude to
Mr. W.T. Meyer, under whose supervision and encouragement this
project was carried out, and to Professor J.S. Webb for his
co-operation and helpful advice.
Sincere thanks are also given to the members of the staff
and students at AGRG for their advice and friendship throughout
the duration of this project. Members of the data-control room
are specially thanked. '
My special gratitude and love to my wife Virginia for her
encouragement and help, also to my parents and wife's parents,
relatives and friends who assisted in the course of my studies.
Miss C. Williams of the Soil Survey is thanked for
providing the regional soil data of North Pembrokeshire.
Lastly the author would like to thank Miss M. Goddard for
her patient typing of the manuscript.
Computer time on the CDC 6400 and CDC 6600 machines was
made available by the Imperial College and University of London
Computer Centres.
to TABLE OF CONTENTS
.22.9.2.1 ABSTRACT ( 1 )
ACKNOWLEDGEMENTS (ii)
TABLE OF CONTENTS (iii)
CHAPTER I INTRODUCTION 1
1.1 BACKGROUND AND SCOPE OF RESEARCH 1
1.1.1 Regional Geochemical Reconnaissance 1 Surveys
1.1.2 Regional Geochemical Reconnaissance 2 in Mineral Exploration
1.1.3 Scope of the Present Research 2
1.2 REGIONAL GEOCHEMICAL RECONNAISSANCE IN WALES 3
1.3 LAYOUT OF THESIS 4
CHAPTER II DESCRIPTION OF FIELD AREA 6
2.1 INTRODUCTION 6
2.2 REGIONAL GEOLOGY 7
2.2.1 Introduction 7
2.2.2 Pre-Cambrian 7
2.2.3 Cambrian 10
2.2.4 Ordovician 11
2.2.5 Silurian 12
2.2.6 Devonian - Old Red Sandstone 13
2.2.•7 Carboniferous 14
2.2.8 Triassic and Lower Jurassic 15
2.2.9 Pleistocene and Recent 15
II Page 2.3 DESCRIPTION OF PREDOMINANT TYPE OF ROCKS 17
2.4 REGIONAL STRUCTURE 26
2.5 PHYSIOGRAPHY AND DRAINAGE 27
2.6 PEDOLOGY 32
2.7 CLIMATE 32
CHAPTER III BASE-METAL MINERALIZATION IN WALES 35
3.1 INTRODUCTION 35
3.2 ORE DEPOSITS 35
3.2.1 The Southern Caledonides Metollogenic District of Wales 35
3.2.2 Pennine-type Metallogenic District of Wales 39
3.2.3 Temperature of Ore Deposition 40
3.2.4 Depth of Ore Deposits 40
3.2.5 Metallogenic Epochs 41
3.3 METALLOGENESIS- 41
3.4 MINING HISTORY 42
CHAPTER IV FIELD SAMPLING, SAMPLE PREPARATION, ANALYTICAL 47 TECHNIQUES AND DATA PROCESSING
4.1 INTRODUCTION 1+7
4.2 FIELD SAMPLING 47
4.2.1 Stream Sediment Sampling 47
4.2.2 Soil and Bed-rock Sampling 48
4.2.3 Sample Preparation 48
4.2.4 Sampling Variability 49
4.3 ANALYTICAL TECHNIQUES 49
4.3.1 Introduction 49
4.3.2 Direct Reading Emission Spectrometer 50 (Quantometer)
4.3.3 Matrix Effects and Corrections 51 (v)
4.3.4 Analytical Control and Precision 52
4.3.5 Emission Spectrograph 54
4.3.6 Analytical Control 57
4.3.7 Atomic Absorption Spectrophotometer 57
4.3.8 Analytical Control 61
4.3.9 Mercury Determination 61
4.4 MICROWAVE-INDUCED PLASMA EMISSION 63
4.5 DATA HANDLING 63
4.5.1 Introduction 63
4.5.2 Statistical Techniques 64
CHAPTER V RESULTS OF THE REGIONAL RECONNAISSANCE SURVEY 67
5.1 INTRODUCTION 67
5.2 FREQUENCY DISTRIBUTION ANALYSIS 69
5.3 REGIONAL DISTRIBUTION OF THE ELEMENTS SHOWN BY MOVING-AVERAGE ANALYSIS 70
5.3.1 Arsenic 70
5.3.2 Barium 74
5.3.3 Cadmium 77
5.3.4 Chromium 77
5.3.5 Cobalt 80
5.3.6 Copper 85
5.3.7 Gallium 86
5.3.8 Iron 86
5.3.9 Lead 91
5.3.10 Manganese 91
5.3.11 Molybdenum 96
5.3.12 Nickel 99
5.3.13 Tin 99
5.3.14 Titanium 102
5.3.15 Vanadium 107
5.3.16 Zinc 110 Page 5.4 INTEGRATED SUMMARY OF THE REGIONAL • 110 GEOCHEMICAL VARIATION
5.5 RELATIONSHIP BETWEEN THE GEOCHEMICAL 113 PATTERNS AND THE GEOLOGY
5.5.1 Introduction 113
• 5.5.2 Correlation with Regional 113 Stratigraphical units
5.5.3 Correlation with Predominant Type 118 of Rock
5.6 RELATION OF GEOCHEMICAL VARIATIONS TO 120 MINERALIZATION
5.6.1 Introduction 120
5.6.2 Possible Significant Anomalies of Copper 122
5.6.3 Possible Significant Anomalies of Lead 122 a 5.6.4 Possible Significant Anomalies of Zinc 123
5.6.5 Possible Significant Anomalies of 124 Molybdenum
5.6.6 Possible Significant Anomalies of Tin 124
INTERPRETATION OF THE GEOCHEMICAL RECONNAISSANCE CHAPTER VI 131 DATA USING R-MODE FACTOR ANALYSIS
6.1 INTRODUCTION 131
6.2 OUTLINE OF PRINCIPAL COMPONENT FACTOR ANALYSIS 132
6.3 PROCEDURE 133
6.3.1 Results of R-mode Factor Analysis 139
6.4 REGIONAL DISTRIBUTION OF FACTOR SCORES 139
6.4.1 Factor 1 Ni-Ga-V-Co-Fe Association 140
6.4.2 Factor 2 Ba-Fe-Zn Association 140
6.4.3 Factor 3 Cr-Ti Association 141
6.4.4 Factor 4 Sn Association 145 Page 6.4.5 Factor 5 Mn-Fe-Zn Association 145
6.4.6 Factor 6 Cu-Pb-Zn-Ba Association 148
6.4.7 Factor 7 Mo-Co Association 151
6.5 R-SCORE ASSOCIATIONS IN THE REGIONAL 151 GEOLOGICAL STRATIGRAPHICAL UNITS
6.5.1 Associations with fourteen elements 153
6.5.2 Associations with sixteen elements 155
6.6 SUMMARY AND CONCLUSIONS 158
CHAPTER VII COPPER, LEAD, ZINC AND TIN ANOMALIES 161 IN NORTH PEMBROKESHIRE
7.1 INTRODUCTION 161
7.2 DESCRIPTION OF FIELD AREA 162
7.2.1 Location 162
7.2.2 Geology and Mineralization 162
7.2.3 Soils 165
7.3 GEOCHEMICAL DATA 165
7.4 RECONNAISSANCE STREAM-SEDIMENT DATA 166
7.4.1 Anomalous Area I - SOLVA 166
7.4.2 Anomalous Area II - MAENCLOCHOG 168
7.4.3 Anomalous Area III - GWM GWAUN 174
7.4.4 Anomalous Area IV - TRECWN 174
7.4.5 Anomalous Area V - LLANFYRNACH WEST 174
7.4.6 Anomalous Area VI - HAYCASTLE 174
7.5 DETAILED INVESTIGATION OF THE ANOMALIES 175
7.5.1 Anomalous Area I 175
7.5.2 Anomalous Area II 175
7.5.3 Anomalous Area III 181
3
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7.5.4 Anomalous Area IV 181
7.5.5 Anomalous Area V 181
7.5.6 Anomalous Area VI 183
7.6 COMPARISON OF REGIONAL SOIL AND STREAM- 183 SEDIMENT SAMPLING
7.7 SUMMARY OF THE GEOCHEMISTRY OF STREAM- 185 SEDIMENTS, ROCKS AND SOILS
7.8 ASSESSMENT OF MINERAL POTENTIAL ON THE BASIS 190 OF GEOCHEMICAL DATA
INTERPRETATION OF GEOCHEMICAL ANOMALIES, CHAPTER VIII 201 ANGLESEY
8.1 INTRODUCTION 201
8.2 DESCRIPTION OF FIELD AREA 201
8.2.1 Location 201
8.2.2 Geology 202
8.2.3 Mineralization 203
8.2.4 Soils 203
8.3 GEOCHEMICAL DATA 204
8.3.1 Reconnaissance stream-sediment results 204
8.3.2 Stream-sediment results 205
8.3.3 Soil results 205
8.3.4 Lateral Distribution of Trace- 206 elements in Soils
8.3.5 Vertical distribution in Soils and Drift 209
8.4 SUMMARY AND CONCLUSIONS OF THE GEOCHEMICAL DATA 213
8.5 ASSESSMENT OF THE MINERAL POTENTIAL OF THE AREA 215 ON THE BASIS OF GEOCHEMICAL DATA
0 ix)
Page
CHAPTER IX LEAD ANOMALIES IN CARMARTHENSHIRE 217
9.1 INTRODUCTION 217
9.2 DESCRIPTION OF FIELD AREA 218
9.2.1 Location 218
9.2.2 Geology and Mineralization 218
9.2.3 Soils 220
9.3 GEOCHEMICAL DATA 222
9.4 RECONNAISSANCE STREAM-SEDIMENT RESULTS 222
9.4.1 Anomalous Area I - DREFACH-VELINDRE 223
9.4.2 Anomalous Area II - CWRT-NEWYDD 223
9.4.3 Anomalous Area III - MYNYDD LLANBYTHER 225
9.5 DETAILED FIELD INVESTIGATION OF THE ANOMALIES 225
9.5.1 Anomalous Area I - DREFACH-VELINDRE 225
9.5.2 Geochemical interpretation of the Lead Anomaly by Identification of Trace- 228 Elements Forms
9.5.3 Anomalous Areas II and III 231
9.6 SUMMARY AND CONCLUSIONS OF THE GEOCHEMICAL DATA 231
ASSESSMENT OF MINERAL POTENTIAL ON THE BASIS OF 9.7 232 GEOCHEMICAL DATA
CHAPTER X SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 238 FOR FUTURE WORK
10.1 SUMMARY AND CONCLUSIONS 238
10.1,1 Regional geochemical Reconnaissance 238 Survey
(i) Sampling and analytical techniques 238
(ii) Data handling 238
(iii) Regional geochemical variation 239
Relationship between geochemical (iv) 240 patterns and geology (x)
Page
(v) Correlation with predominant type of rocks 240
(vi) Relation of geochemical variation ' 241 to mineralization
(vii) Application of the reconnaissance 242 survey of Wales
10.1.2 R-mode Factor Analysis of the 243 Stream-Sediment Reconnaissance Data
(i) R-mode factor analysis of the regional 243 reconnaissance data
(ii) R-mode factor analysis of the regional 2144 stratigraphical units
(iii) The use of R-mode factor analysis in 245 follow-up areas
(iv) Potential usage of factor analysis in 247 mineral exploration projects
10.1.3 Detailed Follow-Up of Some Anomalous 247 Areas
(i) North Pembrokeshire 247
(ii) Anglesey 248
(iii) Newcastle Emlyn (Carmarthenshire) 248
(iv) Other areas investigated 249.
(v) Potential of follow-up areas 250
10.2 RECOMMENDATIONS FOR FUTURE WORK 250
REFERENCES
(xi
LIST OF TABLES
Table Title Page No.
CHAPTER II
2.1 Geological sequence, modified after Pringle 8 and Neville George (1948)
2.2 Structural regions of Wales; Key reference to 25 • Figure 2.6 (after Brown, 1960)
2.3 Relief regions of Wales; Key reference 30 to Figure 2.7 (after Brown, 1960)
Soils of Wales; Key reference to 2.4 34 Figure 2.4, after Min. of Agric. and Fisheries 1970.
CHAPTER III
3.1 Mineral productions of Wales. Years of 44 production from 1845 to 1954.
CHAPTER IV
4.1 Trace element with interfering major elements in direct reading spectrometer 53
4.2 Comparison of population mean and analytical variance and precision for stream sediments 55 based on low-precision spectrographic analyses (after Howarth and Lowenstein, 1971)
4.3 Analytical precisions based on ten replicate 56 analyses, (USGS standards)
Analytical precision (%) for Hilger and Watts 4.4 59 spectrograph, based on 25 replicate analyses
4.5 Operating conditions on the Perkin-Elmer 6o atomic absorption spectrophotometer, Model 403
4.6 Analytical precision (%), all at 95% confidence level, calculated from 34 duplicate 60 pairs of samples analysed in the Perkin-Elmer 403
fu
CHAPTER V Page 5.1 Range and mean content of minor elements in stream-sediments associated with regional 113 geological stratigraphica systems
5.2 Mean Trace-element content from predominant 119 types of rocks in Wales
5.3 Threshold and anomaly levels for log 10 121 • transformed reconnaissance data
CHAPTER VI
6.1 Correlations coefficients of minor elements from reconnaissance data 135
6.2 Rotated factor matrix of the seven factors (associations), selected using Catell's 137 'scree test'
6.3 Minor element associations and loadings of R-mode factor models 0 6.4 Selected associations with fourteen elements 154 of regional and selected sets of data
Selected associations with sixteen elements 6.5 156 of selected sets of data
CHAPTER VII
7.1 Spectrographic analysis of diorites from 176 North Pembrokeshire and Dolgellau
7.2 Comparison of semiquantitative XRF results, Soil Survey of Great Britain, for USGS 186 standard rocks with means of published values
7.3 Element associations, loadings and percentage data correlations accounted for by each 187 factor from regional soil and stream-sediment data
7.4 Trace element content in rocks from North 189 Pembrokeshire CHAPTER VIII Page
8.1 Background and threshold values for arsenic, copper, lead and zinc in stream 204 sediments of Anglesey, based on log- transformed data
8.2 Mean values of metal content in soils along Traverses a-a', b-b', c-c', d-d' and 207 Llanerchymedd anomaly
8.3 Mean values of metal content in soil profiles (sample sites A-B and H) over 208 . known mineralization
• 8.4 Mean values of metal content in soil profiles (D and E) on transported anomaly, 210 not related to known mineralization
8.5 Mean values of metal content in soil profiles (C) on transported anomaly, near 211 known mineralization
8.6 Soil profile (F) on Llanerchymedd anomaly 212
• LIST OF FIGURES
Figure Page No.
2.1 Major political and physical regions of Wales 6
2.2 Geological map of Wales 9
2.3 Glacial flow in Wales 16
2.4 Predominant types of rocks 18
2.5 Structural map of Wales 23
2.6 Structural regions of Wales, modified after Brown (1960) 24
2.7 Relief regions of Wales, modified after Brown (1960) 29
2.8 Drainage map of Wales 31
2.9 Soil map of Wales, modified after Min. of Agric. and Fisheries, 1970 33
3.1 Base-metal mining sites 37
4.1 Standard element variation per analytical day 58
4.2 Precision control chart for duplicate results (zinc and cadmium) 62
5.1 Probability plots of regional reconnaissance data (Co-Cr-Cu-Ba-Fe-Pb) 71
5.2 Probability plots of regional reconnaissance data (Mn-Ni-Ti-Zn-Ga-V) 72
5.3 Arsenic geochemical map 73
5.4 Barium geochemical map 75
5.5 Barium geochemical map, percentile class limits 76
5.6 Cadmium geochemical map 78
5.7 Chromium geochemical map 79
5.8 Chromium geochemical map, percentile class limits 80
5.9 Cobalt geochemical map 81 Page
5.10 Cobalt geochemical map, percentile class limits 82
5.11 Copper geochemical map 83
5.12 Copper geochemical map, percentile class limits 84
5.13 Gallium geochemical map 87
5.14 Gallium geochemical map, percentile class limits 88
5.15 Iron geochemical map 89
5.16 Iron geochemical map, percentile class limits 90
5.17 Lead geochemical map 92
5.18 Lead geochemical map, percentile class limits 93
5.19 Manganese geochemical map 94
5.20 Manganese geochemical map, percentile class limits 95
5.21 Molybdenum geochemical map 97
5.22 Molybdenum geochemical map, percentile class limits 98
5.23 Nickel geochemical map 100
5.24 Nickel geochemical map, percentile class limits 101
5.25 Tin geochemical map 103
5.26 Tin geochemical map, percentile class limits 104
5.27 Titanium geochemical map 105
5.28 Titanium geochemical map, percentile class limits 106
5.29 Vanadium geochemical map 108
5.30 Vanadium geochemical map, percentile class limits 109
5.31 Zinc geochemical map 111
5.32 Distribution of metal content in relation to the thickness of the strata 115
5.33 Copper geochemical map with 2.0 std. deviations above annulus mean 126
5.34 Lead geochemical map with 2.0 std. deviations above annulus mean 127
5.35 Zinc geochemical map with 2.0 std. deviations above annulus mean 128
5.36 Molybdenum geochemical map with 2.0 std. • deviation above annulus mean 129
(vi)
Page
5.37 Tin geochemical map with 2.0 std. deviation above annulus mean 130
6.1 Catell's 'scree test' for selection of suitable Factor Models (Associations) to be extracted 138
6.2 Frequency distribution of grey-scale levels in maps shown in Figs. 6.3 to 6.7 142
6.3 Factor Score percentile map of Factor 1 143
6.4 Factor score percentile map of Factor 2 144
6.5 Factor score percentile map of Factor 3 146
6.6 Factor score percentile map of Factor 4 147
6.7 Factor score percentile map of Factor 5 149
6.8 Factor score percentile map of Factor 6 150
6.9 Factor score percentile map of Factor 7 152
7.1 Geological map of North Pembrokeshire. After IGS 164
7.2 Copper content in -80 mesh fraction in stream- sediments from North Pembrokeshire 167
7.3 Lead content in -80 mesh fraction in stream- sediments from North Pembrokeshire 169
7.4 Zinc content in -80 mesh fraction in stream- sediments from North Pembrokeshire 170
7.5 Arsenic content in -80 mesh fraction in stream- sediments from North Pembrokeshire 171
7.6 Tin content in -80 mesh fraction in stream- sediments from North Pembrokeshire 172
7.7 Locations of anomalous areas, soil sampling traverses and rock sampling sites,N.Pembrokeshire 173
7.8 Copper, nickel, iron content in soils along Traverse PP', North Pembrokeshire• 178
7.9 Copper, nickel, iron content in soils along Traverse SS', North Pembrokeshire 179
7.10 Copper, nickel, iron content in soils along Traverse RR'; North Pembrokeshire 180
4$
Page
7.11 Tin content in soils and stream sediments in
the Maenclochog anomalous area 182
7.12 Copper content in topsoils, regional soil survey of North Pembrokeshire (after S.S. of G.B.) 184
7.13 Factor scohe percentile map of Factor 1, North 193 Pembrokes rrei 7.14 Factor score percentile map of Factor 2, North 194 Pembrokeshire 7.15 Factor score percentile map of Factor 3, North 195 Pembr oke shi re 7.16 Factor score percentile map of Factor 4, North 196 •Pembrokeshire 7.17 Factor score percentile map of Factor 5, North 197 Pembrokeshire 7.18 Facto r score percentile map of Factor 6, North 198 Pemb oke shi re 7.19 a cto s ore percentile map of Factor 7, North 199 FPembrrokecsh i re 8.1 Geology map of Anglesey and location of detailed 202 followed up area. After IGS. 8.2 Map of Soils, Anglesey, after Roberts, 203 1958
8.3 Copper content in -80 mesh fraction in stream sediments from Anglesey 204(a)
8.4 Lead content in -80 mesh fraction in stream sediments from Anglesey 204(b)
8.5 Zinc content in -80 mesh fraction in stream sediments from Anglesey 204(c)
8.6 Arsenic content in -80 mesh fraction in stream sediments from Anglesey 204(d)
8.7 Distribution of copper, lead, zinc and arsenic in -80 mesh fraction in stream sediments, log 10 transformed data, Anglesey 204(e)
8.8 Contoured spatial distribution of copper in subsoil, Anglesey . 206
8.9 Factor score percentile map of Factor 1, Anglesey 216(a)
8.10 Factor score percentile map of Factor 2, Anglesey 216(b)
8.11 Factor score percentile map of Factor 3, Anglesey 216(c)
R.
Page
8.12 Factor score percentile map of Factor 4, Anglesey 216(d)
8.13 Factor score percentile map of Factor 5, Anglesey 216(e)
8.14 Factor score percentile map of Factor 6, Anglesey 216(f) Geology map of Newcastle Emlyn and stream sediments 9.1 219 sample sites 9.2 Location of anomalous areas and soil traverses, 221 Newcastle Emlyn 9.3 Copper content in -80 mesh fraction in stream- sediments from Newcastle Emlyn 224
9.4 Lead content in -80 mesh fraction in stream- sediments from Newcastle Emlyn 225
9.5 Zinc content in -80 mesh fraction in stream- sediments from Newcastle Emlyn 226
9.6 Lead content in soils along Traverses A-A', B-B', C-C', D-D' , Drefach Velindre 229
9.7 Linear lead anomaly in soils, south of Drefach-Velindre and lead content in stream sediments. 230
9.8 Lead and zinc results in soils collected across axis of the linear anomaly, Drefach Velindre 231(a)
9.9 Thermal evolution profiles for lead from controlled heating of PbO, PbSO4 and PbS in rock base and soil from linear anomaly 231(a) Newcastle 1 234 9.10 Factor score percentile map of Factor -' Emlyn , Newcastle 9.11 Factor score percentile map of Factor 4,Emlyn 235
236 9.12 Factor score percentile map of Factor 5,NecastleEmwlyn Newcastle 9.13 Factor score percentile map of Factor 6, Emlyn 237 CHAPTER 1
INTRODUCTION
1.1 BACKGROUND AND SCOPE OF RESEARCH
1.1.1 Regional Geochemical Reconnaissance Surveys
Regional geochemical reconnaissance surveys aimed at delineating variations in the concentrations of chemical elements in stream sediments related to broad-scale geological and geo-
chemical features have been carried out since the early 1950's.
Review of the progress and development of this technique has . been thoroughly covered by several authors (Hawkes 6- Webb, 1962;
Hawkes, 1972, etc.).
Regional geochemical stream-sediment reconnaissance surveys involve the compilations of maps based on the distribution of major, minor and trace-elements in active stream-sediment, sampled at spatial densities ranging from one sample per square mile'
(Nichol and others, 1970; Young, 1971; Davies, 1971), to one sample to one hundred square miles (Armour-Brown and Nichol, 1970;
Garret and Nichol, 1967; Govett, 1968; Harden, 1962). This technique is designed to locate, at minimum cost, areas suitable for detailed follow-up investigations. Sampling procedure, density, analytical accuracy and precision, and productivity are selected to obtain maximum information at•optimum cost-efficiency.
Geochemical reconnaissance surveys using stream-sediments rely on the fact that under normal conditions the products of rock weathering tend to be channelled into the surface drainage system. In appropriate circumstances and subject to weathering
in the lithosphere, the patterns of metal distribution in rocks 2.
and soils should be reflected to a certain degree by corresponding variations in the composition of the stream-sediment.
1.1.2 Re ional Geochemical Reconnaissance in Mineral Exploration
Exploration projects and programmes based on analyses of stream-sediments with the purpose of detecting anomalous concentrations of metals derived from the weathering and dispersion of primary components of mineral deposits is a standard practice with national surveys and mining companies (Boyle, 1967).
The outstanding areas of applicability in mineral exploration of a regional geochemical appraisal are:
1. Primary reconnaissance, as a method of locating both entire
mineralized districts and individual deposits, and
2. evaluating the mineral potential of favourable geological
features.
These two aspects are the basis of the present research.
1.1.3 Scope of the Present Research
Research in this thesis examines the regional geochemical variations in the stream-sediment reconnaissance data of Wales.
This data is part of a larger programme initiated in 1969, aimed to produce a multi-element geochemical Atlas of England and Wales.
The Geochemical Atlas is produced by the Applied Geochemistry
Research Group (R.S.M.), under the direction of Prof. J.S. Webb.
Over ten thousand stream-sediment samples with over
400,000 bits of information (analytical results and field observations), forms the Welsh data. The samples were collected at a spatial average density of one per square mile, and analysed for a total of twenty major, Minor and trace-elements. 3.
The aims of this research are to:
1. Interpret the element variations in terms of geological
features which may localise mineralization.
2. Elucidate inter-element associations of mineral potential
and determine their distribution and provenance using a
combination of areal plotting and statistical techniques.
3. Delineate areas of possible mineral potential, as entire
geochemical provinces and/or individual deposits.
4. Investigate in detail anomalous patterns in order to
determine the nature of the factors controlling the dispersion
of the trace-elements from the bedrock metal source.
1.2 REGIONAL GEOCHEMICAL RECONNAISSANCE IN WALES
There has not been any previous regional reconnaissance in
Wales, although strategic and tactical surveys in smaller scale
with a wide variety of sampling media have been carried out. The
first trials of geochemical methods in Wales were made in 1939 by
the Swedish Prospecting Co. Analysis of plant ashes for Pb and Zn
were used as guide to prospecting (Brundin, 1939). Webb (1959),
summarizes the results of a number of prospecting operations
carried out mainly in England and refers to a trail survey over a
presumed extension of the Pb/Zn vein at the Mynyddgorddu Mine,
Cardiganshire.
Subsequent research was executed by members of AGRG in
stream-sediment reconnaissance surveys, not all aimed to delineate
geochemical variations related to geology, mineralization and
secondary environment, but also to delineate variations related to
trace-element induced agricultural problems and to trace-element
pollution of the environment (Webb, 1968).
111 4.
To demonstrate the applicability of a regional geochemical survey in Britain, AGRG selected three areas in England and Wales as trial survey-areas. In Wales an area covering 850 square miles of east Caernarvonshire, north Denbighshire and Flintshire was selected (Horsnail, 1968; Khaleelee, 1969; Taylor, 1968).
Nichol and others (1970), published the conclusions of this preliminary survey, concluding that geochemical prospecting in mining areas is severly restricted by contamination from extensive mining, milling and smelting activities, with a low probability of finding new economic deposits.
Research at Welsh universities and other institutions in relation to Welsh geology and allied sciences is well documented in the work of Basset (1961-1964). The works of Kakar (1971), and Harries(per. comm.), related to mineral exploration in relation to primary and secondary dispersion in Welsh geological environments are worth mentioning.
1.3 LAYOUT OF THESIS
The layout of this thesis falls into four main natural sections and are as follows:
1. The first section (chapters 1, 2, 3), contains background
information. It provides and introduction which deals with
the scope and previous research in Wales. Geological and
mineralization background found in Wales is given in Chapters
2 and 3 respectively.
2. The second section (chapters 4, 5, 6), incorporates field
sampling, analytical techniques, data handling and
statistical methods in chapter 4; the results of the
regional reconnaissance survey (largely descriptive) ) in
chapter 5; and the application and results of factor analysis
in chapter 6. 5.
3. The third section (chapter 7 to 9) deals with the detailed
follow up work in the areas of: North Pembrokeshire in
Chapter 7; Anglesey in Chapter 8; and Newcastle Emlyn in
Chapter 9.
4. The fourth section (Chapter 10) contains the summary and
. conclusions of the results with suggested future work.
•
•
••
• • ▪ 6.
CHAPTER II
DESCRIPTION OF FIELD AREA
2.1 INTRODUCTION
The geographical limits of the field area covered by the
geochemical reconnaissance survey are the politico-geographic
boundaries of the Principality of Wales (Fig. 2.1), extended
over an area of 8,018 sq. miles (20,767 sq. Kms.).
Monmouthshire is considered in this thesis as a Welsh county.
IRISH S E A
Great Ormcs Head Holyhead-6, 11":31,:.E ovdoun0 • Ehyl 1/4a Hot % Eit.nmarts 41;) Island 13,111r ,- aft.:12;,(- 1,
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INSET AT UPPER LEFT SHOWS COUNTIES Fig. 2.1 7. 2.2 REGIONAL GEOLOGY 2.2.1 Introduction A brief account of the main geological features of Wales follows. This account is compiled mainly from Regional Memoirs of the I.G.S.; Smith and Neville-George (1961), Pringle and Neville-George (1948); and Wood (1969). Where other sources have been used they are detailed in the text. Wales is essentially a region of Paleozoic rocks, having a very good sequence of Cambrian, Ordovician, Silurian, Devonian and Carboniferous strata. Harper {1966) described collectively the Lower Paleozoic systems southeast of the Highland Boundary fault (Scotland), as the Southern Caledonides, Of the remaining geological systems, the underlying Pre-Cambrian is well displayed. Mesozoic and Tertiary sediments cover minor areas. The Paleozoic grouped together, outcrop over an area covering three-fourths of the country, with an estimated thickness of over 60,000 feet. The full geological sequence is detailed on Table 2.1, and the regional geological map of this sequence is shown in Fig. 2.2. 2.2.2 Pre-Cambrian (4)* The most extensive tract of Pre-Cambrian rocks in Wales is the Monian-Complex of Anglesey (Greenly, 1923). Comprises of several series of highly altered intricately folded and deformed rocks, which are divided into three groups of rock-type: 3. Acid intrusive rocks (Coedana granite) 2. Bedded Series (geosynclinal sediments) 1. Basal gneisses * Reference to figure 2.2 • 8. Table No. 2.1. Geological Sequence, modified after Pringle & Neville George (1948) ABUNDANT MINERALS ACCESSORY MINERALS L_,•••• • .. I PLEISTOCENE GLACIAL DRIFT 1 rniTilASSIC - JURASSIC KEUPER MARLS - LOWER LIA, UPPER COAL SERIES .. •••• • .. .. PENNANT SERIES •••• --...- OZOIC _ ,_ _ 1 CARBONIFEROUS LOWER COAL SERIES E ;:i;--- ' •..*:"..**• - - MILLSTONE GRIT ALA •::-: . -...,1 CARBONIFEROUS LIMESTONE Pb - Zn - Pb(2)-Zrt(2) Cu - Pv3)-cu(2)- mn (a) Ii. ..Y4":1 UPPER OLD RED SANDSTONE . . . . 0 . ER P . .' . DEVONIAN LOWER OLD RED SANSTONE Cu? . . ° UPP . . . _.=-...... :-, LUDLOW SERIES Pb-Zn-Cu (b) WENLOCK SERIES ,2-7:4--"' ---- - SILURIAN LLANDOVERY SERIES Pb-Zn- Cu-Fe(1) (c) ZOIC — - O ASHGILL SERIES Pb- Zn - Cu (d) CARADOC SERIES ---== =72.. ORDOVICIAN LLANDEILO SERIES • LLANYIRN SERIES Pb - Zn- Cu (e) PALAE ---:"` . v':;::i'Ll: ARENIG SERIES ....,,,..—...7 .—.-J TREtdADOC SERIES . Pb -7n- FrAs- Foil) Fern- re(T) __ LINGULA FLAGS Cu-Au (f) - --E--,---,---_ _ r mENEYIAn sEgics cru- Ff.(1)- r,t.” -At, Fe'3) - SO - PI, -Zr, 17: 7 -.." 7 =-.- .2.-7; CAMBRIAN .=.'.' 7 : SOLVA SERIES a CAE RFAI SERIES LOVE R ------.L1 . 1 -..,.-..v.z:...., ...._ "' V Pi-; MONIAN SERIES ritT.:"-B-T PRE-CAMBRIAN PEBIDIAN VOLCANIC SERIES ,• ", *40-- , * , DIMETIAN ,,* * App. vertical scale 1:10000 ft. Pb: Galena Sources: (a) Dewey & Smith (1922) Pb(2): Cerussite (b) to (e) Jones (1941) Pb(3): Anglesite Lewis (1967) Zn: Sphalerite Kakar (1971) Zn(2): Smithsonite Gilbey (1969) Cu: Chalcopyrite Mn: Pyrolusite Fe(1): Pyrite Fe(2): Pyrrhotite Fe(3): Marcasite Fe(4): Pyrite Co-rich (3%) 9. GEOLOGICAL MAP OF WALES NN JAN 1-2 NNNN JURASSIC NNN NNN 1 1-i TRIASSIC CARBONIFEROUS DEVONIAN SILURIAN ORDOVICIAN CAMBRIAN PR E-CAMBRIAN 0,1 Trwit Igneous rocks 11111! ,, , i ..;1:•" VV VV ;,:,-_-_----' ___';,;?: 4- IVUVV R EXTRUSIVE I r ...c"./N "1,79—_,., -- A • '' , Or. ...',„''''' 1,1 N "NNNe " ''''''' i ^--. ,'?j . NIV .... '‘i;I .;' •.' INTRUSIVE PROJECT 34 A.G. R.G. .:- .,::• 1/// ...... )Y ,...... t.c:S: /14 I / ...... 1/ ./ ...... : ... : ...... •::: .. •, ...... • • 0 0 0 0 0 0 0 0 0 0 o 0 0 o o o 0 0 0 o 0 o 0 op o 0 0 ° " • " ^-1.1 ...... • • • • • • • • .... ° 0 10 5 0 miles 10 20 1 10 5 0 Kms 10 20 30 B B 1 2 3 L 5 G 7 'CI 1 2 3 4 5 I I I I I I I I I I • FIGURE 2.2 , 1 0. In South Wales the Pre-Cambrian is confined to Pembrokeshire. Here the rocks are products of a period of great igneous activity and have been classified into two groups: 1. Volcanic group (Pebidian volcanic series), consisting of rhyolitic and trachytic tuffs interbedded with acid lava flows. 2. Intrusive group (Dimetian), which include masses of granite, granophyre, quartz-porphyry and quartz-diorite. The whole system was highly folded and extensively denuded before Cambrian times. 2.2.3 Cambrian (a 1-3) The earliest Cambrian sediments found in Wales rest upon Pre-Cambrian rocks with a marked unconformity. In the lower formations of the system the rocks are principally sandstones and at the very base there is a thick bed of conglomerate. Flaggy mudstones form the middle formations, indicating a slight deeping of the basin. A return to shallow-water conditions is suggested by the sandy character of the beds of the upper formations. The general succesion is as follows: 1. Lower Cambrian: Caerfai series, with a red basal conglomerate followed by fine-grained greenish and redish feldspathic sandstones. 2. Middle Cambrian: Solve beds, consisting of coarse pebbly sandstones overlain by micaceous sandstones. Menevian series, consisting of striped shales and dark mudstones. • 3. Upper Cambrian: Clogau shales, overlain by fine-grained flaggy beds. The two series are classified as the Lingula Flags. Tremadoc beds, occupying the upper most position in the Cambrian sequence, consist of a succesion of grey and blue mudstones and shales metamorphosed to slates. 2.2.1+ Ordovician (b1-3) The Ordovician system is divided, showing the rythms of change in conditions of deposition, into four principal series: 1. Arenig: The earliest Arenig rocks of Wales are a series of volcanic lavas and tuffs (andesitic), resting • discordant with Cambrian formations. These rocks are overlain with the coarse-grained sandy and conglomeratic Garth grit followed by graptolitic shales in the higher beds. 2. Llanvirn: This series, consisting of shales and mudstones, was deposited under pelagic conditions, although some interbedded coarse-grained layers are found. Two separate series of volcanic rocks, consisting of andesitic and rhyolitic tuffs and agglomerates, can be also distinguished. 3. Llandeilo: The conditions which produced the uniform lithological character of the Arenig and Llanvirn rocks, were greatly modified by an uplift at the beginning of Llandeilo times which led to the deposition of different types of sediments. The Llandeilo strata is composed of sediments deposited 12. under neritic conditions, giving a succession of flags, shales and mudstones. Throughout the succession there are numerous interbedded bands of acid tuffs and spillitic lavas, reflecting a mild volcanic activity. 4. Bala: Divided into: Upper Bala: Ashgill Series Lower Bala: Caradoc Series During Caradoc times, a number of volcanoes erupted centred mainly in north-western Wales, their products form the Bala Volcanic Series; rhyolites and rhyolitic tuffs (ignimbrites), were poured-out in great quantities over extensive areas. In South Wales a deposition of a fairly uniform succession of black shales took place; an impure limestone is frequently found at the base. By the.beginning of the Ashfill times, all the volcanoes had become quiescent, if not extinct. 2.2.5 Silurian (0-7) The Silurian sediments show much variation in lithology and were affected by earth-movements continuing from late-Ordovician times, In the north-eastern part of Wales, there is a visible unconformity between the Silurian and the underlying Bala Series, with coarse sandy and conglomeratic beds. Elsewhere, however, fine-grained sediments continue uninterrupted across the contact between the Ordovician and the Ordovician and the Silurian. The difference between Ordovician and Silurian rocks, is that the latter ones do not show signs of contemporaneous volcanic activity. 13. The Silurian rocks are classified into three series reflecting geosynclinal conditions with three rock facies: 1. Valentian or Llandovery Series: The Valentian basement beds consist of coarse grits and sandstones, overlain by a thick pack of flags and mudstones with a shelly fauna. 2. Wenlock Series: The rocks of the Wenlock and Ludlock 3. Ludlow Series: Series are litollogically, members of the sames facies, and consist of mudstones and shales alternating with flags, sandstones and grits. The separation of the two series • depended in the detailed mapping of the graptolite zone. 2.2.6 Devonian - Old Red Sandstone (c1-3) The Old Red Sandstone laid down in deltaic conditions. Consists of non-marine and largely unfossiliferous marls, sand- stones, breccias and conglomerates, normally stained red by haematite in the cement. The rock sequence is broken and falls into two distinct formations separated by an unconformity. Conditions of deposition were similar in both. The stratigraphical sequence could be summarized as follows: 1. Lower Old Red Sandstone: (a) Downton Series: Dominantly marls with some minor sand- stone beds. Somewhat calcareous soft rock. • 14. (b) Ditton Series: Interbedded marls and sandstones in approximately equal proportions. Contains also conglomeratic cornstones, which could be calcareous and/or phosphatic. . (c) Breconian Series: (Brownstones), consist of purple-grey micaceous sandstones. 2. Upper Old Red Sandstone: Consists of a group of sandstones, grits and conglomerates. In South Wales the beds comprise of quartz conglomerates and of the Grey Grit. 2-6 2.2.7 Carboniferous (d ) The Carboniferous rocks of Wales rest with great unconformity upon Lower Paleozoic rocks. This system has been divided into three broad groups, indicating from base to top a gradual silting•-up of the sea in which they were deposited. 1. Carboniferous Consists mainly of a thick series of Limestones: relatively pure limestones with a basal sequence of sandstones, conglomerates and shales of variable thickness. 2. Millstone Grits: Is largely formed by sediments of terrigenous origin, comprises of black shales overlain by sandstones and some impure limestones. 3. Coal Measures: Are typical grey measures including coal seams in the lower part with localized red beds (iron beds), at the top. 15. 1-6 1-2 2.2.8 Triassic and Lower Jurassic (f and g ) The Mesozoic strata in Wales is confined to districts adjacent to the margins of the coalfields. Comprises of Triassic and Jurassic rocks. The Triassic is represented in North Wales by the Bunter Series and in South Wales by the Keuper Series, whilst the Jurassic includes the Rhaetic Series ? and a portion of the Lias. 1. Bunter and Keuper Series: Both Series consist mainly of reddish sandstones (New Red Sand- stone), and pebble beds with local conglomerates and breccias, over- lain by sandy and/or calcareous marls (Red and Green Marls). 2. Rhaetic and Lias Series: Both series are formed by black shales at their base overlain by marls and bands of limestones and grits, all deposited under marine conditions. 2.2.9 Pleistocene and Recent The only extensive deposits in Wales younger than the Lias, are tracts of unconsolidated glacial drift that mask much of the solid rock in the uplands and greater parts of the lowlands. The ice that accumulated at the summits of the mountain ranges flowed downhill as glaciers, with their chief glacial outlets along valley courses. These ice-flows have been described as 'Local Welsh Ice' (Fig. 2.3). The Welsh till is a blue-grey stony loam weathering yellow and consisting of material derived from Paleozoic rocks. 16. GLACIAL FLOW IN WALES FLOW OF LOCAL WELSH ICE P 10 5 0 miles 10 lir I 10 5 0 Kms. 10 FIGURE 2.3 • 17. Contemporaneous with the local glaciers, a great mer-de-glace, known as the Irish Sea (Northern) Ice, debouched southwards onto coasts of Wales. The landmass of North Wales split the ice-flow into two main streams, one branch was diverted south-westwards flowing across Anglesey and the Lleyn Penninsula into Cardigan Bay and overflowing over most of Pembrokeshire. The other branch moved towards the southeast invading the Vale of Clwyd, the estuary of the river Dee and the Shropshire - Cheshire plains. The till derived from this ice-flow is similar to the Welsh till in the south-west branch, and reddish silty clay largely derived from Triassic material in the south-east branch. 2.3 DESCRIPTION OF THE PREDOMINANT TYPES OF ROCK I A brief description of the predominant types of rock found in Wales is given in the following paragrphs and illustrated in Figure 2.4. . It is probable that many lithological boundaries are diachronous, as different lithofacies were developing contemporaneously at different locations. However, lithological based division are adequate for purposes of regional geochemistry, as the geochemical maps based on stream sediment analysis (Chapter V), reflect primarily the lithological-chemical variations within the rocks. (A 0) Black Shales These rocks are dark-grey to dark-brown siltstones, owing their dark colour to a reducing environment at the time of deposition of organic matter, sulphides and fine-grained material (Thomson, 1971). s 18. PREDOMINANT TYPES of ROCK AO BLACK SHALE S EMAl CLAYS MUDSTONES A3 AND SHALES SLATES AND A5 GREYWACKES FRIABLE SANDSTONES HARD SANDSTONES QUARTZITES 1:7:t1B4 MASIYE LIMESTONES 17,772 D GNEISS F VOLCANIC ROCK G INTRUSIYES PROJECT Si A. G. R. G. I •B3 • — • • • • i it 7_] 10 miles 10 20 pceF=9.namcs...F oR 10 5 0 Kms. 10 20 30 30 • FIGURE 2.4 19. (A 1) Clays A thick series of red-brown silty mudstones, calcareous mudstones and dark-grey, fissile, micaceous silty mudstones with occasional sandy lenses, all of them of continental environment (Davies, 1971). (A 3) Mudstones and Shales The mudstones are dark-grey, decomposed shales formed of microscopic particles of quartz and clays. Some of them are very calcareous. The shales consist mostly of a monotonous series of grey, blue and sandy shales, often imperfectly laminated and containing fine flakes of mica. • (A 5) Slates and greywackes (grits) The term slate is used in this regional appraisal to define a series of metamorphic turbidite rocks with typical slaty cleavage that cover most of the country of Wales. The cleavage of some of these rocks is sufficiently intense to render them workable. The colour varies from black, dark-grey, dark-blue, blue-grey to olivine-green, according to impurities in the clay groundmass. Black slates are commonly impregnated with pyrite, weathering to rusty surfaces; the olivine-green colour is due to volcanic ash. Interbedded with the slates, bands of massive greywackes (grits) are commonly founded. These are rocks composed of sub- angular and subrounded quartz-grains and small fragments of siliceous slates, igneous rocks and other materials, all bound in a groundmass of clay and silica. • 20. (B 2) Friable sandstones The friable sandstones consist mainly of bright red and mottled continental sandstones containing frosted and well-rounded quartz grains, poorly cemented with iron rich clays, (Sherlock, 1947). Some rythmic sedimentation can be seen, with each bed • typically grading from pebbly conglomerate through pebbly sandstone to red-brown sandstone and mudstones without pebbles. (B 3) Hard sandstones A group of sandstones, grits and conglomerates interbedded with red marls is classified as hard sandstones. The sandstones are formed by well-rounded quartz-grains cemented by clay mineral and some silica of reddish colour due to iron oxides and green sandstones • due to glaucophane. The conglomerates consist of pebbles of sand- stones, quartzite and white quartz in a red marly or sandy cement. Concretionary cornstone is very common all along the sequence. Locally outcrops of green micaceous sandstones with bands of green and grey marl and grey conglomeratic cornstones are found. (B 4) Quarzites The turbidite metasediments are interbedded with thin, coarse massively bedded quarzites composed mainly be recrystallized quartz. • Some of these quarzites show an intergrowth of quartz and authigenic tourmaline, the cause of the tourmalinization is unknown. (C 4) Massive limestones Classified as massive limestone is a thick series of relatively pure limestones, ranging in colour from black to white, with very little variation in their chemical composition. Black limestones are fine, muddy limestones. They grey limestones contain some quartz-grains and pebbles and the white limestones a lesser proportion of non-calcareous material. • Some dolomitic limestones are developed locally. 21. (D) Gneiss The gneiss group is represented by quartz-feldespathic phyllites, schists and gneisses with a roughly banded structure- and are highly foliated and interbedded with ignimbrites and orthoquarzites. The metamorphism suffered by these rocks varies from low to high grade, all within short distances. The metamorphic facies found by Shackleton (1969), in these rocks are: (a) Greenschists facies: muscovite-chlorite-subfacies. (b) Glaucophane - schist facies: ? (c) Albite-epidote-schist facies (d) Amphibolite facies: sillimanite-almandine subfacies. • (F) Volcanic rocks This rock-group is formed by tuffs, ashes and a volcanic sequence of lava, flows of a potassium-rich rhyolitic composition. Roberts (1969) describes these rocks as ignimbrites, formed mainly by glass particles (shards), with phenocrysts of quartz and feldspars. Rhyolites are of widespread occurrence within the volcanic series. They are composed of a fine matrix with feldspars pheno- crysts, predominantly anorthoclase (now perthitic) with rather less andesine (An 30-37). Thomas (1956) mentioned the existence of some sodium-rich spillitic lavas with a pillow structure, accompanied by chlorite, calcite, epidote and quartz. Andesitic lava-flows are very common in Wales and are generally associated with thick, well-bedded tuffs and bands of volcanic conglomerates (Thomas and Cox, 1924). 22. The mineralogy of the andesites consists predominantly of phenocrysts of albite, andesine and some rhombic pyroxene set in a pilotaxitic or occasional orthophyric matrix. (G) Intrusive rocks The intrusive rocks of Wales according to their chemical composition have been classified broadly as granites, granophyrs, microgranites and quartz-porphyr/ies in the acid composition and as diorites, dolerites, greenstones, basalts (intrusive), in the basic composition. Unfortunately, the scale of the map in Fig. 2.4 does not permit the inclusion of all the basic rocks. Granites are represented by plutonic intrusions, some highly altered. Their mineralogy is composed of coarse grains of quartz, • orthoclase and microcline; muscovite and occasionally biotite are also present. Sills and shallow laccoliths of microgranites of equigranular texture are also present, composed of quartz, albite-oligoclase, alkali feldspars and chloritized biotite. These rocks form local aureoles of brecciated and tourmalinized rocks. The granophyres are of the same composition as the microgranites. Although often badly altered, the granophyres never show any indication of the large scale autometasomatism which has affected the microgranites. The basic intrusions are emplaced in three forms: 1. Sills, sheet-like, which form the largest group. 2. Larger and thicker intrusions in the form of laccoliths. 3. Dykes. • 23. STRUCTURAL MAP OF WALES PROJECT 54 A. G. R. G. 10 5 0 miles 10 pacy=pumzemee9==prreme 10 5 10 Kms.10 20 30 FIGURE 2.5 4 25. Table 2.2 Structural Regions of Wales; Key reference to Figure 2.6, after Brown (1960) Alluvium and other Recent Deposits (A) A. 1. Dec Estuary A. 6. Laugharne Burrows and East Marsh A.2. Morfa Harlcch A. 7. Towyn and Pcmbrey Burrows A. 3. Morfa Dyffryn A. 8. Baglan, Abcrafan, Margam, and Ken- A. 4. RO Wen fig Burrows A. 5. Borth Bog (Cors Fochno)- A. 9. Wentlloog and Caldicot Levels Mesozoic Rocks with well-developed Flexures (B) B. I. Vale of Clwyd rift 13. 4. Severn Valley basin B. 2. Cheshire basin B. 5'. Vale of Glamorgan Lias B. 3. Mid-Staffordshire syncline Upper Palaeozoic Rocks with Gentle or Moderate Uniclinal Dips (C) C. 1. Carboniferous Limestone on the western flank of the vale of Clwyd C. 2. North Wales coalfield C. 3. Forest of Dean syncline C. 4. Old Red Sandstone cuesta, Black Mountains-Brecon Beacons-Fforest Fawn:- Mynydd Du• • South Wales coalfield syncline, north flank C. 5. • Upper Palaeozoic Prci,c Ilith well-developed Flexures. Includes sotne Mesozoic Rocks (D) D. I. Red Wharf- MallIraeth syncline D. 11. Titterstone Clcc Carboniferous out- D. 2. Menai Straits syncline her D. 3. Hanwood coalfield D. 12. Woolhopc anticline D. 4. Lccbotwood coalfield D. 13. May Hill anticline D. 5. Clun Forest basin D. 14. Usk Silurian inlier D. 6. Silurian Limestone scarplands D. 15. South Wales coalfield, south flank D. 7. Coalbrookdale and Wyre Forest D. 16. Cowbridgc-Cardiff anticline coalfield D. 17. Armorican folds of the Gower D. 8. Mynydd Epynt and the Abcredw D. 18. Upper l'alacozoic scarplands of Car- cucsta marthenshire D. 9. Old Red Sandstone of the plain of D. 19. Pembrokeshire coalfield syncline Hereford D. 20. Armorican folds of south Pembroke- D. 10. Brown Clee Carbonifcrous outlier shire Areas of complex structures in Lower Palaeozoic and pre-Cam.hrian Rocks (E) • E. 1. Mona pre-Cambrian complex E. 16. Breidden hills anticline E. 2. Bangor and Padarn anticlines E. 17. Long Mountain syncline E. 3. Llim pre-Cambrian complex E. 18. Shelve anticline and Ritton Castle E. 4. Snowdon synclinorium syncline E. 5. , Denbighshire syncline E. 19. Longmynd pre-Cambrian E. 6. Cl.vdian anticlinal range E. 20. Cacr Caradoc-Wrckin uplift E. 7. Harlcch dome E. 21. Cardigan Coast synclinal tract E. 8. Ordovician volcanic 'Ring oT Firc' E. 22. Mill anticline E. 9. Derwen anticline E. 23. Central Wales syncline (south) E. 10. Cyrn y Brain anticline E. 24. Tywi anticline E. 11. Llangollen syncline E. 25. Builth anticline E. 12. Berwyn dome E. 26. Old Radnor inlier E. 13. Central Wales syncline (north) E. 27. St. David's and Hayscastle anticlines E. 14. Machynllcth, Plynlimon, and Van E. 28. Presely and Strumble Head intrusions domes E. 29. Malvern uplift E. 15. Meifod fold belt • 26. The diorites range in texture from fine grained to medium grained, are highly altered making petrographic study difficult. Their mineralogy is largely hornblendic and the feldspares are albite set in a microcrystalline matrix. The hornblende has been replaced by chlorite, epidote, scisite, calcite and some secondary quartz. An interesting feature of these rocks is the presence of sulphides in some of them, mainly pyritic cubes and different amounts of chalcopyrite (Williams, 1927). Sills of dolerite intruding Lower Paleozoic rocks are very common, they are usually exposed as 'Carps'. Their texture varies from fine-grained to gabbroid quartz-dolerites. The primary minerals are andesine to labradorite as plagioclase, and augite, suffering uralitization to hornblende and actinolite. Secondary minerals are epidote, quartz, calcite, apatite and ilmenite. The author collected samples from the Carn - wen quarry in Pembrokeshire containing disseminated pyrrhotite. 2.4 REGIONAL STRUCTURE During the Caledonian orogeny, the sediments of the Lower Paleozoic geosyncline suffered a repeated regional oscillation and compression coming from the south-west. The rocks were thrown into folds, squeezed and cleaved, faulted and overthrust against older rocks. The final result was to produce two main synclinal tracts, complex in detail, with subsidiary minor folds: the Snowdon syncline to the north-west and the Central Wales syncline. Figure 2.5 shows the regional trend of the axes of folding which is in a north-east to south-west direction. Central Wales is traversed by the axes of two major anticlines separated by a broad syncline with a north-south direction. The axial regional trend was modified by movements at the close of the Carboniferous period a and as a result, the axes curve and range east to west. 27. The Caledonian folds were accompanied by major faulting in a direction almost perpendicular to the main axis. At the close of the Coal Measures, intense pressures from the south, known as the Hercynian orogeny, caused the buckling of the Upper Paleozoic rocks against already folded sediments of the Caledonian orogeny. North Wales suffered relatively gentle folds, with little crumpling and thrusting and no cleagege. There was, however, much fracturing, including the accentuation of Caledonian faults. In South Wales the Hercynian oregen is obviously featured by the synclinical depression of the coalfields, consisting of a number of flexures in echelon. The Hercynian fields are frequently broken by faults, some of considerable magnitude. Figure 2.6 shows the structural regions and Table 2.2 gives the explanatory key to it. 2.5 PHYSIOGRAPHY AND DRAINAGE Brown (1960), suggests a certain degree of geological control in the physiography of Wales, which is defined as a block out on three sides by the sea and for the greater part of the fourth side by a sharp break of slope. To study the complexity of the relief, Brown (opp,cit.) divides Wales into six major physiographical regions. Figure 2.7 outlines the regions and Table 2.3 provides the geographical key to these regions. The Lower Paleozoic rocks, consisting largely of hard metamorphic and igneous rocks make up the rugged mountain masses (M). 28. The dissected plateaux, (DP), extending from north to south of the Principality, are also composed of Lower Paleozoic rocks (Cambrian Mountains). Gentler outlines formed by.Carboniferous sediments are found in the South Wales Coalfields. The regions classified as hills (H) are elevations rising abruptly and are formed mainly by local resistant rocks, consisting mainly of igneous rocks. Numerous subsequent lowland valleys (L) penetrate deep into the highlands, separating them into well defined blocks. Along much of the coast, the physiographical features do not correspond with the geological structure, and are mainly the product of marine and glacial erosion. These features are represented by the coastal plateaux (CP). The coastal flats (CF) are all features resulting from the action of waves and wind. Wales is drained by many rivers and streams which have incised their valleys into the dissected plateaux to give considerable relief. The overall picture is one of complexity, with many streams being influenced by the effects of glaciation, river capture and superimposition. A simplification of the drainage pattern shows two dominant trends (Figure 2.8). One lying in a general north-west to south- east direction, the other at right angles to it. Many consequent rivers flow in a radial pattern to the south- east or south-south-east from a centre which lies about Snowdon. Jones (1952), suggests this pattern as the original drainage system of Wales, several obvious cols support this idea. 30. Table No. 2.3. Relief Regions of Wales, Key reference to Figure 2.7. after Brown (1960) Mountains (M) NI. 1. lIchog mass M. 9. Berwyn mass M. 2. Snowdon „ M. 10. I'lynlimon M. 3. Glydcr „ 'Snowdonia' M. 11. Radnor Forest M. 4. Llywelyn „ M. 12. Mynydd Du M. 5. Arcnnig „ M. 13. Fforest Fawr M. 6. Rhinog N. 14. Brecon Beacons M. 7. Cadair Idris mass M. 15. Black Mountains M. 8.' Aran mass Dissected Plateaux (I)) D. 1. Halkyn Mountain D. 14. Aymcstry D. 2. Denbighshire Moors D. 15. Clcc hills Fringe D. 3. Cyrn y Brain D. 16. Bromyard D. 4. Pen y Gv.cly D. 17. Rcd hill D. 5. Yr Allt Borth D. IS. Mynydd Epynt D. 6. Garret; llir D. 19. Tcifi-Tywi intcriluve D. 7. Long Mountain D. 20. South Cardiganshire D. 8. Central Wales D. 21. Mynydd Sylcn D. 9. Trannon D. 22. Western coalfield D. 10. Rhyd Ilywel D. 23. Central coalfield D. 11. Kerry hills and Chin Forest D. 24. Eastern coalfield D. 12. Deacon hill D. 25. Forest of Dean D. 13. Wenlock Edge . • Ifills (H) • • H. 1. Clwydian range H. 9. Carncddau H. 2. LIS7n H. 10. Burton and Westhopo 1-1. 3. Brcidden H. 11. Woolhope H. 4. Wrckin H. 12. Malvern H. 5. Ccfn Coed H. 13. Monnow H. 6. Shelve and Longmynd H. 14. Mynydd Bach H. 7. Cacr Caradoc H. 15. Prcscly . H. 8. Clce H. 16. Mynydd Llangyndeyrn Valley Lowlands (L) L. 1. Vale of Clwyd L. 11. Builth lowland L. 2. Vale of Conway L. 12. Ape Dale L. 3. Vale of Ffestiniog L. 13. Corvc Dale L. 4. Trawsfynydd lowland L. 14. Plain of Hereford L. 5. Mawddach lowland L. 15. Vale of Wye L. b. Upper Dce • L. 16. Upper Usk L. 7. Cheshire plain L. 17. Vale of Tywl L. 8. Dyfi valley L. 18. Lower Usk L. 9. Vale of Pawls L. 19. Vale of Gloucester L. 10. Vale of Teill Coastal Plateaux (C.P.) C.P. 1. Flintshire C.P. 7. North 1;embrokcshire and north C.P. 2. Denbighshire Carmarthenshire C.P. 3. Arvon C.P. 8. South Pembrokeshire C.P. 4. Anglesey C.P. 9. Sv.ansca district C.P. 5. Ll'am C.P. 10. Gower C.P. 6. Cardiganshire C.P. 11. Vale of Glamorgan C.P. 12. Forest of Dean Coastal Flats (C.F.) C.F. 1. Dec Estuary C.F. 6. Laugharnc Burrows and East Marsh C.F. 2. Morfa Ilarlech C.F. 7. Towyn and Pembrcy Burrows C.F. 3. Morfa Dyffryn C.F. 8. Baglan, Aherafan, Margam, and C.F. 4. Ro Wcn Kenfig Burrows C.F. 5. Borth Dog (Cons Fochno) C.F. 9. Wcntlloog and Caldicot Lents • ▪• 31. DRAINAGE MAP OF WALES MAIN WATER PARTINGS MAIN CATCHMENT AREAS 1 CONWAY 2 CLWYD 3 DEE 4 GLASLYN DWYRYD 5 HAWODACH DOVEY 7 SEVERN RHEUM - YSTWYTH - AERON 9 T EIFI 10 TYWI 11 WYE 12 LUGG - TEME 13 CLEDDAU 14 TAF 15 GWENDRAETH 16 LOUGHOR 17 TAWE 16 HEATH - AVAN 19 TAFF - ELY - THAW 20 RHYMNEY - EBBW 21 USK 22 OGMORE PROJECT 94 8 10 5 0 miles 10 10 5 0 Kms. 10 2 30 FIGURE 2.8 411 32. A dendritic pattern is shown by consequent and subsequent rivers, the latter in accordance with the dominant Caledonian structure. The stream banks fall into two categories, alluvial and colluvial. Alluvial banks are not usually steep and are formed by a large range of alluvial material in size and origin. Colluvial banks are usually steeper and consist of local soil material. Streams are often bounded by both bank types, specially noticeable at bends of streams. Piedmont type alluvials and glacial alluvials are common on the mountain areas and consist largely of pebbles of all sizes and very little silt in the first case and of fluvio- glacial debris in the second. 2.6 PEDOLOGY The regional soil types of Wales are controlled by physiography, rainfall and on localised basis by the geology. On these terms the Ministry of Agriculture, Fisheries and Food (1970) has classified the Welsh soils into ten main types. Figure 2.9 shows the generalised distribution and Table 2.4 gives the soil classification. 2.7 CLIMATE The general patterns of the climate of Wales is influenced by its maritime location and by its situation in the region of dominantly Atlantic air masses. In addition the height and general geomorphology cause marked local difference in climate. Air movement is principally from the west and south-west making the climate maritime in character with consequently moderate temperatures, ample and evenly distributed rainfall, low amounts of sunshine and frequently hill and some coastal fog. 34. Table 2.4. Soils of Wales; Key reference to Figure 2.4 after Ministry of Agriculture, Fisheries and Food (1970). • A. Coastal sand and shingle with little soil development. 1 Coastal sand and shingle. 13. Soils of the drier (sub-humid)" lowlands with a• significant summer moisture deficit, 2 Deep;' medium` or heavy texturedd soils in alluvium, with ground-water at variable depths; calcareous or non-calcareous. 3 Peat' or peaty mineral' soils with ground-water at variable depths. 4 Well drained, naturally calcareoud, medium or heavy textured soils, often shallow over chalk or limestone. 5 Medium or heavy textured, well drained or moderately well drained, naturally non-calcareous soils. 6 Deep coarse textured5soils, including sandy podzols;h usually well drained, but locally with ground-water • at variable depths. 7 Deep, heavy or medium textured soils with impeded drainage, including naturally non-calcareous and calcareous variants. • C. Soils of the uplands and humid' lowlands with no significant summer moisture deficit. 8 Shallow, stony and/or peaty soils of the higher mountains, with much bare rock and scree. ' 9 Peaty soils of the uplands, with impeded drainage and/or excessive surface wetness. 10 Medium textured mineral soils of the wetter lowlands, high plateaux and upland valleys, often shallow and/ or stony; drainage variable depending on site and substratum; naturally non-calcareous except very locally over limestone. 11 Medium or heavy textured, non-calcareous soils in alluvium, locally peaty, with ground-water at variable depths. ri Footnotes Sub-humid (Drier lowlands, mostly below 800 ft.). Potential soil-moisture deficit (accumulated) exceeding 3 in: in some month (normally Juno or July) in most years. b Deep (soil). No hard rock or other layer impenetrable to roots at less than 20 in. (50 cm.). Medium textured soils. Loams, silt loams, sandy loams (more than 10% clay); sandy clay loams, clay learns and silty clay loams with less than 35% clay; loamy very fine sands and very fine sandy learns. d Heavy textured soils. Clays, sandy clays, silty clays; heavy clay learns and silty clay learns with more than 35% clay. Peat soils. More than 40% organic matter. Peaty mineral soils. More than 25% organic mattor. g Coarse textured soils. sands, loamy sands and sandy loams with less than 10% clay (excluding loamy very fine sands and very fine sandy loams). h Podzols Soils, usually sandy, with an iron7deficient (bleached) sub-surface horizon over a horizon enriched in humus am or iron, often cemented. Humid (Wetter lowlands and uplands). Potential soil-moisture (accumulated) deficit not exceeding 3 in. In any month I • most years. 35. CHAPTER III BASE-METAL MINERALIZATION IN WALES 3.1 INTRODUCTION In recent years several investigations have been made of the geology, geochemistry and ore deposits of Wales. These studies have led to some revisions as to the nature of these deposits, a very important aspect for mineral exploration. The base-metal mineralization under consideration in the present research, comprises deposits extending from the Parys- Mona mines (Anglesey) in the north, to the lead prospects of Glamorganshire in the south. These ore deposits may be assigned to two metallogenetic districts, belonging to different metallogenetic provinces: 1. A district of the Southern Caledonides Metallogenetic Province with copper-lead-zinc mineralization occurring in the Lower Paleozoic rocks, and 2. Lead-zinc ore bodies found in the Carboniferous Limestone Series, belonging to the same province as those of the Pennine ore- field (Jones, 1922; Dunham, 1948). The geological framework in which the .ore deposits are set was described in the previous chapter. 3.2 ORE DEPOSITS 3.2.1 The Southern Caledonides Metallogenetic District of Wales The Southern Caledonides Metallogenetic Province forms a group of mineral deposits within the Caledonian mobile belt of Western 36. Europe; some aspects of its metallogenesis have been described by Wheatley (1971). The Welsh Metallogenctic District is part of this province, and is formed by nineteen mining districts. Figure 3.1 shows these districts, as well as the most important isolated mines. The ore deposits within this district are similar to those in other geosynclinal belts. Two generalizations concerning these deposits are: (a) Predominance of vein type, lead-zinc replacement deposits with reduced cross-section, and (b) Copper stockworks and vein-type deposits of subordinate economic importance, though recently, copper-molybdenite disseminated mineralization in intermediate igneous rocks of Caledonian age have been discovered. . The mining districts formed by the copper-rich deposits are Parys-Mona, Bethesda, Snowdonia-Llanllyfni, Trawsfynydd-Deudraeth, and Harlech Dome (Dolgellau Gold Belt). The lead-zinc mining districts are Llanrwst, Llanfair-Talhairn-Llansanna, Llanyngon, Plynlimon (Cardiganshire-Montgomerywhire), Cwmystwyth, Llandovery, Lampeter, Llanfyrnach and Carmarthen (Fig. 3.1). The copper deposits, as a rule, are located within conformable pyritic zones, closely associated with acid volcanic sequences. Lead-zinc ore deposits are closely related to tectono-stratigraphic controls, influenced by the coincidence of prominent domal features coinciding with pyritic shale horizons. The pyrite is possibly originated by bacterial reduction of sulphates (Mohr, 1955). • 38. Chalcopyrite-pyrite-quartz and galena-sphalerite-quartz are the predominant ore types. Marcasite, arsenopyrite, pyromorphite, orpiment, tellurides, and native gold are locally subordinate. Quartz is the main gangue mineral; calcite, witherite, baryte, and fluorite also exist as gangue in some deposits. The wall-rock alteration consists mainly of silicification, with weak sericitation and chloritisation in some deposits. The paragenetic sequence of the deposits in the district may be summarized as follows: quartz-pyrite-base metal sulphides (Sphalerite, galena, chalcopyrite, etc.)-calcite-marcasite (James, 1955; Rodgers, 1953). An example of this sequence, based on the prevailing chemical elements is given by Gilbey (1968), for the a Dolgellau Gold Belt: 1. Early Vein Stage. Major: Cu, Fe, S, Si02 Minor: Co, As, CO 3 2. Base-metal Sulphides Stage. Major: Pb, Zn, S Minor: Cu, Fe, CO 3 later heavy elements include: (a) Cu, Ag, Sb, S, As, Te, Bi (b) Au, Ag, Sb, Pb, S 3. Late Veinlets. Major: Zn, Fe, CO3 Minor: Cu, Pb The spatial distribution of the ore deposits shows some regional metal-zoning, with an axial copper-rich belt bordered by areas rich in lead-zinc (Wheatley, 1971). Jones (1922) indicates a vertical zoning in some deposits of Cardiganshire, characterised by an upwards decrease in sphalerite, and a downwards enrichment in chalcopyrite. • 39. 3.2.2 Pennine-type Metalloqenetic District of Wales The lead-zinc ores of the Pennine-type metallogenetic district of Wales, are restricted to the Carboniferous Limestones Series, with the exception of the Bryn-celyn mine, where ore was worked from the Lower Coal Measures (Smith, 1922). The mining districts forming this metallogenetic district are Holywell, Halkyn, and Minera. (Fig. 3.1). Three geological factors control the distribution of ore shoots within the district, these are: 1. A conjugate vein and crosscourse system of minor fractures. 2. The presence of shale bands to act as impermeable roof beds. 3. Primary hypogene mineral zoning. The minerallogy is simple and similar to 'the Southern Caledonides deposits, with galena and sphalerite as main ores. Calcite or quartz are the gangue minerals and cerussite and smithsonite exist as secondary minerals at shallOw depths. Chalcopyrite, baryte, fluorite, anglesite, malachite and pyrolusite are rarely found (Dewey & Smith, 1922). Smith (op.cit.), set a two stage mineralization model in these deposits: 1. Fluorite, sphalerite, galena and baryte 2. Chalcopyrite, galena, and possibly baryte. The dominance of Calcite over quartz in the gangue indicates that a lateral zoning similar to that of the Pennine ore-field (Dunham, 1948), is absent; though their relative lead/zinc proportion displays a detectable lateral zoning (Taylor, 1968). • 4o. 3.2.3 Temperature of Ore Deposition The temperature of ore deposition can only be indirectly inferred from the ore mineral associations, and from their trace-elements content. El Shazly & Others (1958), suggested an apparent antipathetic variation with temperature in the content of Ga, Ge, and Sb in sphalerite, and an apparent sympathetic variation in the Ag, Bi and Sn content in galena. Both trends support a medium-temperature of formation, probably between 200° and 250°C. Gilbey (1968), gives similar temperature of deposition for the Harlech Dome deposits. The high concentration of Ag in sphalerites of Cardiganshire is also interpreted by Kakar (1971) as indicative of a mesothermal mineralization. Investigations in crystalline pyrites of the Parys-Mona district, indicate a rise in temperature in the sequence of mineralization from less that o 100°C to 200-300 C iin the stockwork zones at lower levels (Wheatley, 1971). Schellmann (1939), considers the lead-zinc deposits of Halkyn to be mesothermal, as does Dunham (1934) for similar deposits in the North Pennines ore-field. In summary, the base-metal mineralization of Wales was formed at medium-temperature and may be classified as mesothermal. 3.2.4 Depth of Ore Deposits It is difficult to translate general depth-terms into specific figures for the thickness of cover overlying the ores when they were formed. On the basis of the geological history of the Paleozoic rocks in Wales, of the mineralogy of the ore deposits and on a dynamic model of the fault system of Cardiganshire Lii. (Philips, 1970). A depth of 600 to 1500 feet is suggested for the lead-zinc deposits, and of 2000 to 3000 feet for the copper-rich ones (Wheatley, op,cit.; Gilbey, op.cit.). 3.2.5 Metallogenetic Epochs The ore deposits as a group were formerly assigned to a single metallogenic epoch, either Caledonian or Hercynian (Jones, 1922; Archer, 1959). However, Moorbath (1962), according to lead- isotopic studies of deposits within the British Isles, distinguishes six metallogenetic epochs, ranging in age from Caledonian to Upper Mesozoic, indicating that the mineralization was of a pulsatory nature, spanning over the period 470 to 150 M.Y. • Of the six metallogetic epochs, only four are recorded in the base-metal deposits of Wales. Fairbain (1971), based on results of isotopic dating of intrusive rocks in the Southern Caledonides, shows a good correlation between deformation and plutonism, and a continuous polyphasic deformation contemporaneous with magmatism occurring 470 to 370 M.Y. ago, according to this, the Southern Caledonides deposits were formed pre-dating periods of plutonic crystalli- zation (Wheatley, 1971). 3.3. METALLOGENESIS The base-metal deposits of Wales were formed by Hydrothermal fluids. The metasediment/volcanic sequence present in Wales is quartzo-feldspathic in character and rich in trace-element content (Kakar, 1971; Thomson, 1971). The onset of the Caledonian- Hercynian orogenies following lithification, caused folding, s 42. fracturing and igneous activity. K-Na chloride-rich connate waters became active due to a rise in the geothermobaric gradients, leaching metals from the sedimentary pile and becoming potential ore-forming fluids. The migrating hydrothermal fluids rose to surface through channelways percolating through pyrite-rich horizons and precipitating copper-pyrite and complex lead-zinc- pyrite stockworks and veins. In the case of the mineralization in the limestones, the hydrothermal fluids found shale bands that acted as impermeable roof beds, precipitating the mineralizing solutions in fractures cutting across the limestone. The high amount of silica as gangue mineral in the deposits of the Southern Caledonides district, may be attributed to a felsic magma at depth or possibly to hydrothermal leaching of the walls of the channelways which the fluids migrated to the near- surface environment. 3.4. MINING HISTORY Mining in Wales was a rural industry in the moors that failed to weather the economic storms of the late 19th and early 20th century (Lewis, 1967). The boom period of the industry was from 1850-1870, with most of the base-metal mining ceasing some 80 years ago. Foreign competition and gradual exhaustion of the ore-reserves were the prime reasons for the decline; other factors that also hastened the end included lack of capital and the absence of exploration. During the first and Second World wars the revival of the industry in some areas of Wales was • 43. attempted without much success. After a long period of activity lead mining was resumed in 1952 at the Parc mine (Llanrwst district), lasting until 1954 when work became uneconomic hence forcing the close of one of the last base-metal operations in Wales. Today, thanks to government aid, several mineral exploration projects • are being carried out by private enterprise. The total mineral production of dressed-ore in Wales is given in Table 3.1. 0 • • • TABLE 3.1 Mineral Productions of Wales, Figures are of dressed ore in tons. Years of production from 1845 to 1954. No.of No.of No.of No.of Copper Lead Zinc Gold References Mines Mines Mines Mines Southern over 115,314 Dewey & 24 49,620 35 25,688 35 10 NORTH Coledonides 3,000,000 oz Smith 1922 WALES Carboniferous 23,538 1 658,000 113 341,000 113 Dunham,1959 Limestones O.T. Jones Van formation 720 16 113,889 16 38,508 16 1922 Gwestyn 3,000 15 7,568 15 530 15 Formation CENTRAL Gwestyn- WALES Frongoch 2,638 6 49,886 6 5,812 6 Formation Frongoch 502 95 252,479 95 81,693 95 Formation Gwymyswyth 32,912 1 1 Formation 1 8,925 SOUTH 927 Hal1,1972 272 69,400 20 4,191 9 3 oz 1 WALES 47. CHAPTER IV FIELD SAMPLING, SAMPLE PREPARATION, ANALYTICAL TECHNIQUES AND DATA PROCESSING 4.1 INTRODUCTION The regional geochemical reconnaissance of Wales, as part of the United Kingdom Geochemical Atlas being prepared by AGRG, comprised the sampling of active stream-sediments, the chemical analysis of the sediments for six majors and twenty trace- elements, and the compilation of maps based on the distribution of these elements. The sampling procedure and density, in * conjunction with the analytical techniques used, have been tested and assessed on previous reccnnaissance surveys (Nichol and others, 1970; Young, 1971; Davies, 1971). The chemical analysis yielded over 250,000 analytical determinations, the processing of this data and the compilation of maps were carried out by computerised methods. Selected stream-sediment anomalies were followed-up with detailed stream sediment, soil and rock sampling. A more precise analysis for a lesser number of chemical elements was performed on the follow-up samples. 4.2 FIELD SAMPLING 4.2.1 Stream Sediment Sampling During the summer of 1969, over 10,000 stream-sediment samples were collected by eleven (two-man) teams. Duplicate samples were taken at stream/road intersections at a spatial • 48. 2 density of one sample per square mile (1 sample/2.59 Km 1 Over high ground the density is lower due to difficulty of access and to lack of silt and fines on the stream beds. Only active stream- sediment was collected and special care was taken to avoid collapsed bank material and organic-rich ooze. The samples were stored in pre-numbered kraft paper bags. In the follow-up survey, stream-sediment samples were collected at close intervals along the 'anomalous' streams and at critical points. The sampling was performed in the same manner as described above, with the exception that duplicate sampling was not carried out. 4.2.2 Soil and Bed-rock Sampling Soil and bed-rock samples were only collected in the follow-up survey. Soil samples were collected using a manual 'T' soil auger; pertinent notes were recorded, such as depth, colour, texture, moisture and organic content of the soil, and relief, drainage and vegetation of the sample site. Bed-rock was sampled wherever outcrops permitted; altered rock was avoided and the best specimens were obtained at the inumerable queries that cover the Welsh countryside. 4.2.3 Sample Preparation Stream-sediment and soil samples were oven dried overnight, in the collecting kraft bag, at about 60°C using a collapsible field oven. Samples for Hg analysis were air-dried at room temperature. The dried samples were gently dissaggregated by pestle action in a porcelain mortar and sieved through an 80-mesh 49. nylon bolting cloth (nominal aperture size of 0.204 mm, corresponding to 82 threads per inch). The minus 80-mesh fraction was retained and placed in appropriately numbered paper envelopes. Rock samples were air dried and reduced to gravel size by hammering, the chips were then fed into a stainless steel 'chipmunk' jaw-crusher. The crushed sample was recycled as the jaw's openings were progressively reduced to the finest setting to produce a pulverized sample that was quartered. Two portions were ground on agate mortars and sieved through 80-mesh sieves. 4.2.4 Sampling Variability Miesch (1967), discussed at length the major sources of geochemical sampling variability. Howarth and Lowenstein (1971), assessed the sampling variability for the stream-sediment reconnaissance survey of England and Wales in comparison with the analytical variability of the ARL 29000B Quantometer used in the analysis of the samples (see sec. 4.3.2), The concluded that: 'The sampling error is generally less that the low-precision spectrographic analytical error for all the elements considered (Al, Ca, Fe, K, Si, Ba, Co, Cr, Cu, Ga, Li, Mn, Ni, Pb, Sc, Sn, Sr, V, 'Zn), and only in a few cases such as the occurrence of mineralization (or contamination), does the ratio of sampling to analytical variance exceed a factor of about three'. 4.3 ANALYTICAL TECHNIQUES 4.3.1 Introduction The analytical techniques used on most of the samples of this project are standard methods employed at AGRG, these techniques have been developed for rapid routine analyses of geochemical .■.■■ ■.■ 50. samples. Accuracy and precision have to some extent been sacrificed in favour of increased productivity. The 10,000 stream sediment samples of the reconnaissance survey were analysed using a direct reading emission spectrometer (Quantometer). Atomic absorption and colorimetric techniques were used on the same samples to analyse As, Cd, Mo and Zn. Over 2,000 reconnaissance samples forming the follow-up areas were re- analysed using a semi-quantitative spectrographic method. Stream-sediment and soil samples from the follow-up stage were analysed according to the element forming the anomaly by atomic absorption (Pb-Zn) and/or emission spectrography (Cu-Sn). All rock samples were analysed spectrographically. Other analytical techniques such as X-Ray diffraction, micro- wave plasma emission and Hg-determination were used on specific samples. 4.3.2 Direct Reading Emission Spectrometer (Quantometer) The principles and practice of spectrochemical analysis are thoroughly covered by many other authors (e.g. Ahrens and Taylor, 1962; Brode, 1962; Harrison, 1962; Sawyer, 1963) and the use of direct reading emission spectrometers in geochemistry is also accounted by many others (e.g. Cameron and Horton, 1967; Celenk, 1972; Cruft and Giles, 1968; Davenport, 1970; Tenant and Sewell, 1969). The technique and a detailed description of the ARL 2900B direct reader spectrometer used at AGRG is given by Newman and Foster (1968) and Young (1971). Only a brief outline of the technique (pre-analysis sample preparation and analysis), is described: 51. In order to remove moisture and oxidise organic matter, a weight of 10 gms. of each minus 80-mesh sample was ignited for 3 hours at 450°C. The ignited sample was then thoroughly mixed with a buffer at a 2:3 ratio. The buffer consists of a mixture of sodium fluoride with two parts of carbon powder. The resulting mixture was packed into a pre-drilled electrode by tamping it onto the mixture, maintaining this way a constant volume in all samples. A small hole was made with a pin down the centre of the packed electrode to prevent splitting of the sample during arcing. 9.5 Amps and an integrated time of 90 seconds with an electrode gap of 3 mm are the arcing conditions. Calibration was performed with synthetic standards, resembling an intermediate igneous rock with various levels of trace-elements. 4.3.3 Matrix Effects and Corrections A major disadvantage in the use of direct readers (quantometers) in the analysis of geochemical samples, is the need for 'background' corrections, understanding as 'background' in this section, as the effect of enhancement or depletion of some elements analysed as a result of the matrix composition of the sample; an effect easily corrected on photographic methods, but, impractical in direct readers. At AGRG, the spectrometer is fitted with two 'background' channels (4116.0 A and 2008.0 :210 to check possible fluctuations. Ca, Si, Al, Fe and Mg (in order of importance) have been found as the major elements causing interference with trace-element values. Regression lines were calculated for the effect of each major- element on each trace-element and a three phase computer program for these corrections was developed; Phase 0 : corrections for • 52. bias in calibration; Phase 1: corrections for background and arc effect, 'and Phase 2: corrections for line interference Thompson(per. comm.) . Table 4.1 gives the affected trace- elements used in this thesis with the interfering major elements. The corrections applied are of the type Y = aX + b, where Y is the trace-element and X is the interfering major element. 4.3.4 Analytical Control and Precision Analytical control was maintained by three methods: (i) During the course of an analytical day, a set of eight standard bulk-samples of natural stream-sediments (streams draining the main type of rocks in Wales and England), were analysed as analytical controls. To act as an additional check, two synthetic standards with high and low levels of trace-elements were repeatedly analysed.' Analytical precision, mean zero point offset, absolute change in zero point and correlations were calculated daily using a computer program. When the calculated results were not satisfactory, the analyses for the day were repeated (Thompson, AJAX, pers. comm.). Analytical precisions were calculated as + 1.96 s/X ; where s is the sample standard deviation and X is the arithmetic mean. Table 4.2 gives the precisions calculated by Howarth and Lowenstein (1971), for the stream-sediment standards. Table 4.3 gives the analytical precisions of six international rock standards analysed by the author through five analytical days. Elements in concentration near to the detection limits show poorer precisions compared * with the elements at higher concentration levels. 53. Table 4.1. Trace-element with interfering major elements in direct reading spectrometer. Trace Wavelength Approximate Interfering Major Element (A) Range settings Elements (PPm) Ba 4554. 20-500 Al, Ca (Proportion) Co 3453.5 3-1000 Ca, Mg Cr 3438.0 2-5000 Ca; Al, Ca (Prop) Cu 3274.5 2-1500 Ca Mo 3170.4 .3-200 Ca Sn 2840.0 4-5000 Al, Fe, Si Ti 3653.5 100-25000 Al, Ca, Si Zn 2138.6 50-1500 Al, Ca, K, Mg, Si • • 54. (ii) The day to day analytical variations were checked using a daily map plot of the element Ge (internal standard, 1000 ppm), with the map plots of the different elements analysed. Bad analytical days were easily spotted and the analyses for the day were repeated. The disadvantage with this procedure lies in the need of several analytical days already plotted in map form to detect a bad run. (iii) A graphical method for a second control on the day to day analytical variation was also used, and consisted in the plotting of the Percentage Relative Deviations for each element, at one standard deviation against the number of the analytical day, and was calculated as: Max - Min/1.96sx 7; • where Max: is the maximum value of the standard, Min: is the minimum value of the same standard and is the arithmetic mean (Howarth, pers.comm.). An example of the resultant graph for copper, lead and zinc is shown in Fig. 4.1. As a conclusion of the calculations and graphs of the analytical controls, it is obvious that the method is semi-quantitative with a low precision and with a relatively erratic day to day variation. Parameters sacrificed to some extent in order to achieve a large number of analyses in a short period of time. 4.3.5 Emission Spectrograph The semi-quantitative method used with the AGRG Hilger and Watts E-492 spectrograph, was developed by Nichol and Henderson-Hamilton (1965). The pre-burn sample preparation, type of electrode and packing procedure are similar to the ones described for the direct reading spectrometer. The difference • 0 Table 4.2 Comparison of population mean and analytical variance ratio (r) and precision (S) for stream sediments based on low-precision spectrographic analyses Element Sandstonea Sandstone' Shales Shales Limestone° Basic igneousf Basic igneousg Granite" Granite' Detection r k r 0 S6 S6 r s6 s6 r r Al - 29 (2.0) 26 30 30 - 22 - 39 - 39 10 - 30 3.1 - 18 0.15% Ca - 101 38 38 1 09 (2.9) 45 (1.5) 49 - 49 - 109 - - 164 0.2% Fe - 44 20 (1.2) 17 48 - 21 - 35 - 35 - - 48 - 32 36 0.1% K - 24 (1 -7) 14 (2.0) 12 (1-5) 27 - 14 - 58 - 58 3.9 (2.3) 27 (1.1) 7.2 30 0.01% Si - 35 15 15 40 - 11 - 20 - 20 - - 40 - - 26 0.5% Ba - 32 4.5 40 2.0 23 28 - 31 - 38 - 38 28 - - 66 10 Co - 75 21 5.0 10 51 n.d. n.d. - 47 - 47 - .51 20 279 20 3 Cr - 246 62 67 85 - 73 - 43 - 43 85 n.d. n.d. n.d. 10 Cu - 32 (2.0) 27 120 44 n.d. n.d. - 63 631 63 (2.6) - 44 16 76 16 3 Ga - 46 47 30 40 n.d. n.d. - 32 - 32 2.0 (2.0) 40 - 6.0 40 1 Li - 38 45 32 80 - 39 - 36 2.3 86 80 - 2.3 27 5 Mn (3.9) 42 (1-3) 25 2.0 34 56 6.0 17 - 56 - 56 -- - 56 - 35 17 5 .Ni - 88 61 2.3 17 (1 -7) 50 n.d. n.d. - 24 - 24 n.d. n.d. n.d. n.d. n.d. n.d. 5 Pb - 68 22 2.5 17 30 n.d. n.d. - 52 19 52 30 10 30 21 3 Sc - 8 29 48 72 24 (1.2) 53 - 53 1.8 - 70 - - 57 2 Sn 65 641 186 299 26 652 n.d. n.d. 228 140 1.8 151 548 151 120 158 1540 - - 224 5 Sr - 46 (2.2) 37 32 1-5 50 - 33 - 35 - 35 (1.4) - 50 - - 49 6 V n.d. n.d. 48 39 71 n.d. n.d. - 52 - 52 71 n.d. n.d. n.d. 10 n 20 20 18 21 21 8 12 30 8 10 5 r. Ratio of population mean/analytical variance : r is less than 1.: 3. r when within-site 0 Limestone. South Cadbury. Somerset (36311248). random error component differs from zero at 0.05 level of significance; (3.). r wheri f Basic igneous. Cudlipptown, Devon (25210788). within-site random error component is not different from zero at the 0.05 level of g Basic igneous (with possible contamination from adjacent mine dumps). Zoar. near significance : s6. analytical precision (1 per cent). based on 10 replicate analyses; n.d., Horndon. Devon (25270808). population mean below detection limit; n. number of localities sampled in duplicate. h Granite. Devon (25640917). a Permo-Triassic sandstone, Copplestone. Devon (Nat. Grid ref. 27621019). i Granite (with trace-element enhancement caused by secondary environment controlled b New Red Sandstone. Osmaston. Derbyshire (41913434). manganese-iron precipitation), northwest Dartmoor. Devon (26080891). C Shale. Upper Cotton. Staffordshire (40583475). i Detection limits after Dr. M. Thompson (personal communication, 1971) ; values in d Shale (known to have high trace-element values). Onecote Grange, Derbyshire ppm unless stated otherwise. (40473558). k Bulk samples. (after Howarth and Lowenstein, 1971) $ Table 4.3 Analytical precisions 00, based on 10 replicate analyses, (USGS standards). A : Range and arithmetic mean (Flanagan, 1968); B : Arithmetic means; . C : Analytical precision 00. G - 2 GSP - 1 AGV - 1 PCC - 1 DTS - 1 BCR - 1 USGS AGRG USGS AGRG USGS AGRG USGS AGRG USGS AGRG . USGS AGRG A B C A B C A B C • A B C A B C A B C Fe(%) (1.49) 1.73 0.15 (3.33) 2.50 0.23 (4.99) 3.59 0.29 (6.43) 4.64 0.72 (6.96) 5.16 (10.61) 5.11 0.66 1800- 855- 1047- 480 - Ba 3000 1570 142.3 2000 962.8 128,9 2700 880.4 30.9 1.07 3.2 1230 425 32.5 (1950) (1360) (1420) (6.89) (6.3) (790) • 2-21 <3-22 10- 30 80- 300 96-200 29-60 Co 4.2 1.0 6.15 1.03 11.1 2.34 59.9 10.8 85.91 18.1 3.8 (4.9) (7.5) (15.5) (112) (132) 15.3 (35.5) • 5-29 5 -18 8.-45 1840 - 2840 - 8-45 Cr 1.45 0.07 1.81 1.10 1.54 1.57 4730 620.1 5560 210 1.3 1.8 (9.0) (12.9) 77.1 908.7 (16.3) (3090) (4230) <2 - 17 15 - 54 5 2-83 5-16 Cu 6.3 1.7 24.01 10.47 39.1 4.03 4.84 1.68 <2-15 3.64 2.0 7-33 12.05 2.1 (10.7) (35.2) (63.7) (10.4) (7.9) (22.4) 16 - 31 12-35 14-24 16 - 30 Ga 9.9 1.9 10.84. 1.45 10.23 1.82 10.7 1.4 (20.2) (18.8) (18.4) (12.4) (12.5). (21.6) 180 - 360 260 450 640-870 610-1430 526 800-1460 1040-1600 mn 178.2 57.5 554.4 916.1 669.6 83.5 . 113 2144 720 (265) (326) (728) (889) (963) 468 132 (1350) Mo 1.00 0.55 0.93 0.8 1.75 1.0 0.3 0.7 (6.6) 0.6 0.6 (1 2) (1.6) (3.7) (5.5) (3.9) 2 11-27 1750 - 1770 - 8-3o Hi 0.56 4.3 3.43 5.01 5.86 7.2 3400 1227 275 194 (6.4) (10.7) (17.8) 3300 1420 (15.0) (2430) (2330) 15 - 43 14-80 18-48 Pb 6.6 2.0 21.6 3.17 14.2 4.03 9.5 2.2 12.5 5-35 2.1 1.7 (28.7) (52.4) (35.4) (13.3) (14.9) 2.5 (18.0) Sn (1.0) (6.5) (3.2) (1.8) (2.6) (1.4) TI 2305 155.0 3416 288.9 4805 352 19.4 (3200) (4100) (6500) (100) 36.13 (100) 24.7 9030 674 40.8 (13300) 26-60 38-67 V 7.8 6.o 18.5 5.42 70 - 171 52.4 10.4 21-55 6-52 120-700 (37.0) (52.0) (121) (31.2) 171.5 23.0 (18.9) (384) 54 - 340 Zn 42-138 167.2 64-304 24 - 100 38.5 7.9 ( 143) 96.6 (112) 53.8 83.5 22 - 140 94-278 (74.9) (53) (61) (132) 59.9 19.7 57. lies in the buffer used and its mixing ration (1:1) with the sample. The buffer is prepared as a 1:1 mixture of lithium carbonate and carbon powder. Ge (400 ppm) is added as an internal standard. The spectrographic equipment and arcing conditions are also described by Nichol and Henderson-Hamilton (op.cit.). 4.3.6 Analytical control Analytical control of the method was retained by comparing observed values of the USGS standards G-1 and W-1 with accepted values in literature (Stevens, 1960). The two international standard rocks were analysed in every plate with fifteen unknown samples. Precisions were estimated using a computer program written by Armour-Brown (1971) and are shown in Table 4.4. A second analytical control was confirmed by a visual reading of the internal standard Ge: (3039.1R) line, and if it departed markedly from the added concentration (400 ppm) the sample was re-analysed. 4.3.7 Atomic Absorption Spectrophotometer Samples of the reconnaissance survey were analysed for Cd and Zn by atomic absorption analyses. Follow-up stream-sediments and soil samples, covering Pb/Zn patterns, were also analysed by the same method for Cu, Pb, Zn and Cd and a few were analysed for Fe and Ni., All the analyses were performed on the Perkin-Elmer (double- beam) atomic absorption spectrophotometer, Model 403. Table 4.5 shows the operating conditions used with the instrument. Two methods of sample digestion were used: HNO digestion with 3 the reconnaissance samples and HNO3/HC104 digestion with the follow- up samples. Previous work at AGRG has shown that the results 58. COPPER 0 O 0 O O• O 0 O LIAO 0 O 20 to O O 0 0 0 oo .Fig. 4.T.• Standard element variation per analytical day. 59. G - 1 W - 1 USGS AGRG 0 USGS AGRG 0 52 Co 2* <5 - 5080-100 39 1 6 1 40 Cr 23 120 53 10-20 51 100-200 1 1 00 13 110 46 Cu 1083o-I 53 6o- 8o 22 20 18 44 16 36 Ga 10-40 10-80 Fe 0 1.6 11.0 2 3 1.58 26 10.8. 47 1.4-1.8 8.o-14.0 (%) 15 0 10 Mu 238 42 1320 40 100- 200 1200-140800 Mo <2 <5 <2 <5 120 2 <5 80 35 Ni 60-150 50 5 49 8 53 Pb 3o-4o 37 3-10 Sn 2 <5 - 2 <5 - 1400 7000 Ti 1500 464 6400 40 800-2000 5000-9000 25 360 V 16 49 240 53 10-40 200-500 50 75 Zn 40 51 82 48 40-100 50-150 Table 4.4 Analytical precisions (%) for Hilger and Watts spectrograph, based on 25 replicate analyses. USGS: arithmetic mean values (Fleischer & Stevens, 1962). AGRG: arithmetic mean and range 0 : precision (%) at 95% confidence limit * : PPM e 60. SPECTRAL WAVELENGTH ELEMENT SLIT FLAME INTERFERENCE (mm) (molecular absorption) Cd 228.8 4 Oxidising Cu, Na, Fe Cu 324.7 4 Oxidising NONE Fe 371.9 3 Oxidising NONE Ni 232.0 3 Oxidising Ca, Na, Fe Pb 283.3 4 Oxidising Ca Zn 213.8 5 Oxidising Ca, Na Table 4.5 Operating conditions on the Perkin-Elmer atomic absorption spectrophotometer, Model 403 ELEMENT PRECISION (7,;)* Cu 18.9 Fe 15.0 Ni 20.0 Pb 7.6 Zn 16.6 Table 4.6 Analytical precisions (%), all at 95% confidence level, calculated from 34. duplicate pairs of samples, analysed in the Perkin-Elmer 403. • 61. obtained by HNO digestion for Cd and Zn in stream-sediments do 3 not show any appreciable difference, compared with those obtained by HNO3/HC104 (Leen, pers.comm.), the HNO3 digestion method is a rapid method of attack. ' The deuterium background correction was used in the determination of Cd, Pb, Ni and Zn for non-atomic interference (molecular absorption plus light scattering). 4.3.8 Analytical Control Analytical control for the rapid determination of Cd and Zn in reconnaissance samples was kept with a statistical series of four samples (Stanton, 1966). The high-end of the series consisted of a soil with high levels of trace elements and the low-end of pure silver sand. These series were analysed in duplicate within every analytical batch (250 samples) and the precision were estimated graphically at the 95% confidence level. Figure 4.2 is an illustration of this method of control (Thompson and Howarth, 1973). Precisions given in Table 4.6 for Cu, Pb, Zn, Ni and Fe in the follow-up samples were estimated from duplicate pair samples, analysed every thirty samples. 4.3.9 Mercury Determination Mercury analyses of follow-up soil samples over Pb/Zn patterns was performed on a double-cell flameless atomic absorption spectro- photometer developed by James and Webb (1964). The description and discussion of this analytical technique is given by Evans (1971) and James and Webb (opp.cit.). • 8 62. 6 5 Ii 3 2 en ~ 1 ::l en 8 u. ~ 6 5 Z W 4 1.11 ~ 3 ...w co 2 • w U ~ 1 ~ w 8 (.,).(e u. V u. / / 6 V I C 5 v / 4 / .IV V 3 ~/ I(~ 2 / V @ @ 2 3 4 56 8 1 2 3 4 .5 6 8 2 3 4 56 8 1 MEAN OF RESULTS ZINC • 8 (,,) V 6 / 1/ 5 .I / .I 4 V 3 t----+----lr-t-+--t-iH-+-+---~- t PER C E N T / /f---II-+-+-l-++-I 10 PERCENT L /. 2 ~ 1 -J 8 ::l (!) 6 W· Il:. 5 / / 2' 4 w w 3 • ~ I- w 2 en w u z 1 w ~ w u. u. C 2345681 2 3 4 56 8 1 2 3 4 56 B 1 MEAN O~ RESULTS CADMIUM Figu re 4.2 PRECISION CONTROL CHART FOR DUPLICATE RESULTS In a set of duplicate measurements on many samples where for each sample the precision • of measurement is 10 per cent at the 95 per cent confidence limit (i.e. crill = 0.05) the indicated proportion of points will fall above the diagonals. The scale of the means mU5t be 10 tim~s greater than the scale of the differences. 63. 4.4.0 Microwave-Induced Plasma Emission The microwave-induced argon plasma emission system described and developed by Meyer and Lam Shang Leen (1973), was used in follow-up soil and rock samples for the qualitative analysis of Pb vapour evolved as thermal evolution profiles from controlled heating in an induction furnace. This method provided information of metal-forms in the samples by comparison with synthetic and natural standards. 4.5 DATA HANDLING AND STATISTICAL TECHNIQUES 4.5.1 Introduction In recent years as a result of data explosion there has been a considerable need in the adaptation of statistical and computer techniques in the interpretation of data. The system of recording, storage and retrieval of data is of primary importance. The system adapted for the two types of data of the reconnaissance survey was designed by Howarth and Nichol (pers. comm.). (i) Field sampling observations were completed by the field teams in 80 column forms with a specific format. This data was transferred to punched cards and thence to magnetic tape. (ii) Analytical data, output by the direct-reading spectro- meter in typed form and punched cards, was corrected and thence transferred onto magnetic tape. Three punched cards were produced for each sample and all of them contained the sample number, easting and northing coordinates. The wet chemical data for As, Cd, Mo and Zn was recorded directly on coding forms, thence punched onto cards and read onto magnetic tape. 64. 4.5.2 Statistical techniques As mentioned previously, the over-all objective of the interpretation of the reconnaisance data is to distinguish 'anomalous' metal variations (patterns), derived from mineralization in relation to other features. The procedure employed are of two types; (i) Univariate, which deals with the data on the basis of single variables; and (ii) Multivariate, which considers the data on several variables. All frequency distributions, means and standard deviations measurements from single variables have been plotted and calculated using computer program (GESTAT) compiled by Grret (1967). This programme also has a number of options, including logarithmic transformation of the data, a Chi-square test for normality on the plotted histograms, a computation of a product-moment correlation matrix, a matrix of Student's t values; and several other options such as scattergrams and listings of anomalous samples with values greater than two standard deviations. Trace-element values, moving-average values and factor scores were all plotted using a computer program (PLTLP) compiled by Howarth (1971). This grey-scale program is designed to deal with large numbers of irregularly spaced data. The scale of the output map can be varied at will by specifying the bounds of the map. Class intervals are specified for each element and all values falling within these classes are represented by a particular grey overprint symbol. The symbols are plotted at the location of the sampling point (easting, northing). The symbols have a finite • 65. size and thus in larger scales the symbols may overlap, in these cases the geometric or arithmetic mean of the values is calculated and is placed in the appropriate concentration class. The resultant maps are smoothed to an extent dependent on the number of overlapping symbols. In order to delineate the overall variations (patterns) of element distribution, in the context that the knowledge of relative values of adjoining groups of samples is important for comparison with the precise value of anomalous trains at any specific location, smoothing of the raw data by use of a spatial moving-average technique has been employed. The technique reduces noise produced by analytical and sampling errors and enhances the spatial geochemical trends or variations present. Howarth and Lowenstein (1971), discuss the use of this technique on data similar to that of the reconnaissance survey of Wales. The window size used is of 10 sq. Kms. with one cell overlap. Each window position will average all points lying within 9 adjacent cells in the original map (raw data). The average is of 3.7 samples per cell in the plotted maps (1:1,000,000). One of the main difficulties in plotting geochemical data in mapform, is the somewhat arbitrary procedure of grouping the concentration values in different class limits in order to obtain a normal-Gaussain distribution. In this context, without prior knowledge of the number of groups needed to achieve this distribution, the regional data has been distributed in percentiles (deciles). A sub-routine was adapted to the Grey-scale computer programme to calculate the deciles on the total data range, new deciles were recalculated using a new range, from the minimum data value to the 99th percentile of the total data. This new • 66. distribution was plotted in map-form with the frequency distribution of the grey-levels in the map tending towards a normal-Gaussian distribution. The moving-average technique was also applied to this distribution. The multivariate analysis applied to the data is based on a principal component factor analysis (R-mode). Calculated factor scores were plotted in map-form with the percentile moving-average version. The univariate analysis is dealt with in Chapter V and the multivariate analysis in Chapter VI. 0 0 0 67. CHAPTER V RESULTS OF THE REGIONAL GEOCHEMICAL RECONNAISSANCE SURVEY 5.1 INTRODUCTION The variation of trace-element content observed in the stream- sediment.geochemical survey of Wales is described in terms of geochemical relief known as geochemical patterns. The description of these patterns is based on the spatial distribution of single- element data. Arsenic, barium, cadmium, cobalt, chromium, copper, gallium, iron, lead, manganese, molybdenum, nickel, tin, titanium, vanadium and zinc have been selected With the objective of delineating background and anomalous metal variations related to the metallogenic districts previously described in Chapter III. In order to have a better understanding of the distribution and behaviour of the trace-elements selected, other features such as relief, lithology and stratigraphy, secondary environmental and contamination effects also had to be interpreted. The reconnaissance data is noisy due to sampling and analytical errors and to natural variations related to geological controls. For this reason a moving average analysis was used to smooth the raw data producing in this way, generalised trends. To interpret and outline only regional trends, three different scales of maps have been investigated: 1:250,000 (4 miles to 1 inch); 1: 625,000 (10 miles to 1 inch app.); and 1: 1,000,000 (16 miles to 1 inch app.); the latter have been found most suitable and are thus included in this thesis and the regional analysis is based on them. Concentration limits have been selected on the basis of a • 68. rigorous examination of the data and on the scale of the map to be plotted. Maps with their concentration limits based on percentiles (deciles) have also been plotted. These maps outline relevant features that tend to be Masked in the low and/or high background concentration patterns. The wet chemical data does not have percentile maps, as it does not form a continuous distribution and the values were only recorded to the nearest standard value. The procedure adopted for the interpretation of the geo- chemical maps is as follows: (a) According to the metal distribution, regional trends are ' classified into three groups of patterns: low, medium and high. (h) Low patterns are detailed only briefly, as their use in mineral exploration is limited. (c) Medium and high patterns are interpreted on the basis of (i) Physiography and drainage (ii) Geology (iii) Known mineralization (iv) Pedology (v) Contamination The present chapter also reviews a univariate analysis of the sixteen elements, in large groups of samples selected from the regional data. These sets were obtained from areas covering regional geological stratigraphic units. Each set of samples was processed individually using the GESTAT program compiled by Garret (1967), and for each set both untransformed and log 10 transformed data were examined. r 69. 5.2 FREQUENCY DISTRIBUTION ANALYSIS Developing an effective system of interpretation of geochemical data involves the consideration of multiple population. Potential mineralization is only one of a host of genetic factors that may play a part in the development of the overall geochemical variation. The simplest interpretative procedure is to classify or investigate the variation of each element on the basis of the statistical polulation that it may represent. This approach is least successful when large sets of samples are used and when the contrast of the elements analysed is low. Probability plots have been successfully used in classific- ation of geochemical data (Tennant and White, 1959; Lepeltier, 1969; Meyer, 1969; Celenk, 1971). Figs. 5.1 and 5.2 show the probability plots of twelve elements out of the sixteen used in the analysis, as only these display a distinct distribution in the 9,910 samples that form the regional data. Arsenic, cadmium, molybdenum and tin do not show a definite distribution. The plots of gallium and vanadium are on normal-probability paper as they tend towards a normalTGaussain distribution. Barium, chromium, cobalt, copper, iron, manganese, nickel, lead, titanium and zinc are plotted on log-probability paper as they tend towards a log normal distribution. An analysis of the curves reveals that manganese and titanium show three distinct slopes, Copper, lead and zinc display two distinct slopes and the rest of the elements display continuous curves without sharp breaks and without contrasting populations. Interpretation of the slopes as individual populations is not necessarily justified as more than one combination of populations can give rise to • similar probability plots. • Fig. 5.1. Probability plots of regional reconnaissance data (Co - Cr - Cu - Ba - Fe - Pb). 0 11 PI . MI . 4 DO 0 01 OM fffff 4 Al m m MOO...... ft • . •• •••., •. .. 0.1.111 . 04 .0 iM . WWWWW MI MI T..; .7_-[ 77 '7— Fi— ; -7— I:" I-1— 1—: 7- T77:7 : r 7" . . 1 1J1 fmta10.1. on.... -. .. - I - - . I I - ourvano.1 or CCITIM 312:1074. DATD1 - - L— - : r----' --ozzrersAice Cr LT 1 . -- 1..- I . ' ■ 1 _ I , L. • ; 1 i 1 i i I • _ •• 171 I — 1 , ■ 7 r . —/ —I, — — 7i; _ • ....I, - I • • I , I- -1. 1 : - i •. I 1 • 1 .. 1*. :1.-j -1- -- - • -- • . - , -.I-I- -j--- --i--- 7" --1 ------: = ..._ _. - ..._— ^.- ^ •I I:- —.;— I I I I •, - : • ; - • i ; ' . ..• . . I . r • I I • : : I .1; 4. In I. 44 i0 I0 M es PP __•0 ■•• 4.4 PS .40., NM .1 • OA OM MI 01 10 40 1111 Mk 4. sr P. 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I - 1 -- -i-r--1--.1-1, - 1--- • - I- --1- -- -..1 1, • " li 1 I - • I - .1.1 1 • • -,--_, -,,,.:,------7-1-1-7 ! -- • I- 11., . • . I : . --• I .." 1 ! ' - :1- - ' ' .. . 1 t•••. I . I I• • , : : • I : . I I /. i : •t ;:: :.• * . I ' 1 : • 1 10 'OS • -i- 1. ' ' 40 •• NI 40 10 M. 4.4 MI 0•4 441044. • ... .. 441, 4•• 1•••• • 1. LI Lb La m . MI ma 011 10 ••• MOMO •••• Distribution of Manganese Distribution of Nickel Distribution of Titanium •.• ••• •• 10 •• to LI ... M •• • 11 • •• •11 •• PM •I1, • M•4 ------7 . : --- 7' 7 --T-1-- --r-T - . -- -r-•r- 1*); "...'-.--1 -I I. .• -'- f -1 - --. ' .• III. 7:111714 :74.447I- ....7.17 1a+. 4: :±Hi i i -11 : • - -21/3:3 1 710/1 01 .ZIPC. III 9.74 C.1.1. OLTL •-: -I -1 - - - I- I -I"- I - - • _ I.. ' ' - - L -- -11-ier.ti ..:s.L.. ------• - -its,. - - r . - 1". L.--. 1_,_ ..__!•• .. : • •. L r - rif --r-r.:---11 1-.1--.--,-, -- --- F.: :I .' - •* 7- 7 - .--, , 1 : . I: _1_• -it •-••• • •* - •:. • •,-: ' I - ••••:•-•1 .•-t - - -. - •-:-- i,...... 1. H 1 TT . •41 _L_ _I 120 F-_ ._-7_ r_ .. . __ _.i . ._i. A_ . ir _ i __.1 __, - t--t-I - • ,: -,,--,---1-, 1 • I T : - __ __, 4_ - -- - .-- 1'.:TTC7.17C7: lSr10.710111$ TO W.:01...W. WV • • • - ,, : . :. I _l____i_l__i_l_4- • .,• :: • :: I "•:: ; J.:, •: . , ;• "• .: ": .:,• : : 5910151'Citil I • 25 100 I . 1 -.-1---- -T-7 ---. 4a 7 - .1 - - . '.. • - 1-- 1 • 11 i • ; I . I I . - 10 5‘.11 09 - -r ------__I• ....-1 . i •--• , I • :• • : • - • - 171- • • :11 I I -- • • . 1- - - • • - *• _J 1: ''' .2:1;...-- (.1 , • 1 i , --1t1: 1 ...-4-1 .. .. 1----:,- T T.:1- . • ..e‹ • • Li : • • -.4 4. -• -4. - ,-.4. 1 ,.._ -4 .4 •• 4 .4 I • ■ ---7.--11-- - ..:-. "•- I . I •• • 1-1--• i . ' :11 . ...1..1] . /- 7 '- . - • 1 - - i : . I ' • II• . : '' ' •* • . . l• .* . : 1 , 25 .-.." --.--1 i•IA - .1...._Ki. ..,...,:...... J__,••_: ,.. __. • ,..• •• :,_ ...: .....,...... ___.4_• i_ H.:_,...±..,...... „.....,__,..,,._r ._.__. __• ..._._, ,... _, • i .: . .. 7 1 •••• • . 1 %I - 1 •:. :.; :. • : :11.,.i;::. :.:t .:•.• j:ii:17.,: .1•:;f::•.] •:::, ::,*: i . ::....i. p- • : ... •:. : :,.,, . • ..,,,, ••• • OM: 04•11 • • ••• ra• ..... Distr'bution of Zinc Distribution of Gallium Distribution of Vanadium 72. 5.3 REGIONAL DISTRIBUTION OF THE ELEMENTS SHOWN BY MOVING-AVERAGE ANALYSIS The contoured moving average grey-scale maps are illustrated in Figures 5.3 to 5.32 and show the following regional features: 5.3.1 Arsenic (Fig. 5.3) The regional distribution of arsenic shows that background values below 8 ppm are located mostly in the eastern boundaries of Wales, along the lowlands of Cheshire and Herefored, and the Welsh Marches. Similar patterns appear in Anglesey, Lleyn, Pembrokeshire and the plateaux of the coastline of Cardiganshire. Background values below 30 ppm are concentrated along the dissected plateaux and mountain areas. Background values above 30 ppm are concentrated on the mountain areas of North Wales and on the dissected plateaux of the coalfields of South Wales. The catchment areas with high background concentration patterns are Conway, the heads' of the Dee, Mawddach, Rheidol, the heads of the Teifi and Tywi, Loughor, the heads of the Wye, Tawe, Neath-Arran and the heads of the Taff and Ogmore. There is a distinct distribution of higher concentration of arsenic over Lower Paleozoic and Upper Carboniferous sediments in relation to Devonian, Triassic and Jurassic sediments, that show a lower concentration. Lithologically, pellitic rocks have a higher background concentration over the rest. Unlike the Pb/Zn mining districts in Carboniferous lime- stones, most of the mining areas of the Southern Caledonides metallogenic district show high background levels of arsenic. • Nli~ E X WALES - URQUIDI - /~RSEN I C COL. GEOCHEH I CAL f1AP 1/1000000 OLOW-PASS FILTER U~ING EFF~CTIVE RAUIUS OF 1 CELLS ARSENIC -- --- • <4.0 + 4.0 - 7.9 = 8.0 - 14.9 B 15.0 - 29.9 e 30.0 - 59.9 in p.p.m. • Fig. 5.3 7I+ Peaty soils of the uplands show high background concentrations of arsenic. On a SW-NE direction from the industrial area of Swansea towards the Brecon Beacons, a very extensive high pattern is caused by pollution. 5.3.2 Barium (Figs. 5.4 and 5.5) Barium shows an even distribution over most of Wales with an average background of 200 to 300 ppm. Its regional distribution with selected class limits is shown in Fig. 5.4 and Fig. 5.5 shows the percentile limits. Background concentration patterns of below 200 ppm occur over Pre-Cambrian and Upper Paleozoic sediments. An extensive low background pattern occurs on Lower Paleozoic rocks on the main water shed between the Afon Teifi and the Afon Aeron; this pattern is suspected to be a natural one enhanced by a day-analytical error. The higher background concentration patterns greater than 500 ppm, occur over Triassic formations on the Cheshire Plains, outside the boundaries of Wales, coinciding with known mineralization in the Mid-Cheshire ridge (Davies, 1971), and over that which occurs in North and South Wales, showing considerable difference of low background patterns in Central Wales. The Shelve-Habberley mining district (Shropshire) shows an interesting pattern spreading into Montgomeryshire. A major background concentration of barium occurs over Ordovician sediments of South Wales, with the highest background concentration over the Pb/Zn mining districts of Llanfyrnach and Carmarthen. There is no apparent regional variation of barium in relation co relief or soils. '\ HINEX WALES - URQUIDI - BARIUM GEOCHEMICAL MAP 1/1000000 OLOH-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS BARIUM • <100.0 + 100.0 - 199.9 = 200.0 - 299.9 B 300.0 - 399.9 0 400.0 - 499.9 B >500.0 values in p.p.m. • MINEX WALES - URQUIDI - BARIUM GEOCHOICAL MAP 1/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 I I BARIUM I BBB EE I I <139.5 BM:13E81:B= BBE EjBE 09@ I BEEEEfg: +- EEEE BEE t)00 =+1,,j+++ f EE , 139.5 - 168.4 =BEE (4 =++=B @0 II BEEE3-+-.E3 EBBE EE=='+'7,1-4-11 EBB E00 OCA4 dEBB + 168.4 91 BEE-EB--=BEC EE 00gEBBEEE=-+.1. 1+-= £000E100 0I I - 190.5 EBEBEF===3B3B3E400EBEEEE====--=-- 1 =1109 1:g000000J EEB30== E,OgEBBEE 0 - E.-2_=_4EEBA- 4- -=== 380000000 I .- 210.5 • BBBBI0 E EE3=-- OfME3BEE gEF' BE00tE3- ==== 3(gOgg = 210.5 E ==BE00gEBBEEE gOIDEBg063 '4--00@00(gg I - 228.6 BBEE=--==EEEEEEEEEEEg.EBEEF - i----- BB gOlg0000 BBBBB=---=EUZEEBB33EL.EBBBBEFAIEA-3=3FQ4001111M101 I B 228.6 - 246.4 775 • BEE■==--++=3BrIf.EMrFFEIJF3BBBE Er3=B3FtEEg€10ENtiC1 33B +--4.6 DEB BBBBE EE=B gP:=EgtOOF;mEn. I .E 246.4 - 269.4 EEEEBd==- 33, 333E £ =B ,'EEE300M28 I - 302.4 33BEEEEE === gr. EEE331===BE33B1.3,-IEERFOOB00001 269.4 BELOOgAEE=== 00g EEEBBBBEB3E EEBBEBB 'JgOE000.91 E24000009I e 302.4 - 379.3 3fe0GOEB 3fp0000 00gEECEEEEE I, EmBe 3 I dEig -=EgE34000MO@EEEgggIEE EEEEB 3E00 000t +++-- BB BEgE3g0012MOEEEE"#00gbEEBEEEP BBBEg@OWIT,I I ■ >379.3 --++ BBB =3 B3g000D0gEEE40@gEEEe).BBBBBEP0000, I +4- +-- gg§[email protected] values in p.p.m. +-=‘Dg(400 EEEr , - .E, -. _ - EEBEEEEtogP001 CLASS --::00@*C)EEEe,i11- £B9r7,EBt331:3t3P6F.BgBEE£Et. uz.+0J- ,PERCENTILE BGOODOglOggFEFFEEBBBFEEEBEE0tEriBEEFIgg042 I LIMITS 00000gotaiEEEE333BBBEdogt'g OgEF-13EEdi3E::E: I 0000000:Er.E EEBBBBBBOOGOOgEEE'==3,33 000 tE3EESAEEEEEEEE00g00009 0 I 004E3BB3EEgLE3EEEEEg00400nr,00000LE3=-B3 I .ELBBBBBELf;E3BEEEE0000M2P@PO0 B =BEE3) I =BEE3DM.33EEEE33B3EEEgOS000flE0003ECFogciEi • I -=BEEBIEJIEBET4gE3BEBEE00000E110000 003q,e;E31 --3EEB33 EEP*E3BBEEgt)g000gP000000hL33. == 3E£E3i3Egf.i]E£EBBBBEE6-331-1w=.1::@OPF,B1-3UPi ===-BEEB3=3BBE333EEBBE3311 3ELgEE-S,-1 B=---3: 0 33 =BEEB391==-==3EEE - ====l1Lj=i I £m ==.---+, 8 =3BEEEBOBEBB33133E3R ------i I BB=---=--++-BEE3 -33EEEB333BBBBB6EI43BBBT3 I I BB==----==-=-41013334LgkEEd3EBB3B 3BEBEE - ===I -====-++-=6BN=EiggjEE300WEEEEF9B BREBEBw-==I I +++----+ 12 +-3BBJ=BEEEE3g0000ggIEEF@EB==-=B -==+-- I ++41, 9,1 1 ,1 +-=--=BEEEE3000,004006" , =--+=BE=- +++3 ++++++++;), .71 +--+--=B3EB3EEEEEIgQ4P =----=EE3=+-- 9-17,-++++ --+ /WY,.---+++-=ZE=33BB;lEii:ile=- __17. ... 2,715"+"-= is .. ...7.= == 1333=-- -=u6OF g0g000 Sj===BBE33LIEBB=-+LI ,,,,,+++++=E 3---===--=--+- = = BBEg088g000 B====- =3EEEEEEE= -++++++1, +--- FOO F-+++ BEEE tmonm £65-= -33E3B'3i3E£Ei:EB==------=,7, ==BbE3+1,111+----+++ ••••=.7- EF,a33300001 ++-= EB=J FEEEEEEC3EBB==-31331=-= 366 8 3====-+ . . I 7 1 9 7 4----+ 45+-= E QP201P-J=11: B++-= 00E33EggogggEED333==3EE33BE5N=11==--12...,211++1,„" ++==fAtiCfr-TiH EBB=== ggE.,:00000gEE333==BEELIEBB33A=---++, 177111 9 ,7 BBB gg4OgggggOOttE.EEP.B.d3EEtE33===-++++17//./ 1.-+::Hlfijt-: ::3 B=3E 8 000000MflOg gnEEFAIDC)====-+5++--++„ •• 7 7 7 11 +-==--.1---= I =BE00000ggOMOUG0000n000gFEEi=----+r2+--=-+ , 9 11-1---++1.1-4---7:=1 P()Pt:),/e.10t1G00051MA1400gE 333d==+---+, -=L;---=--==- 1 , ,I ++---+„j+--1 EEEEEEJ==-133ggtttggOgg =-+-=--++--== BB=---==+--++ +-7.- -3-- -f--j 11..J3 t;L3E8e.f L ++++ -=1171 Bt3===- ++++T4+T---++-4B6=- I --==--+---==3331a=-=1BBB==-++++ = 34 B= 31-3 = ---=-I=J7p1+-=3ttE3EUE I +--++++-- 33E3B ==---+---+I---= +-EEB33E:3==-==B33=EBIE===30 =-4=WE31 +++++++---93EIT =-4.--===---=-+ 2 ++= = 33EEEB33EDEBEEJEEE12,E= --==1 ++=-++-=-= -+ ub- =-+.,,,)+--==33 3E339Egoggq3 .-==i +=--- EB===-+,f++++--=- --==3E331FJEP - I -4-17;1++- _-+-=3E71E3 60E1 'YAJ--== - 1 • 7 ,L1: ....r.:-. 4.s.; ++:=3EEL-401i170t,-- - 1 117 -1- "==-11===EOOtiOf0E1==-- i =_=er,„:= 3El6 CE14€100 EMEB I =-=400 GL3B7) GM000 I 000000F.B3r:0600 3 ,4 ‘4r.T3....=3: I I EB=d 3BE I 7.+ B==BEEE I I I I 1 I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 Fig. 5.5 • 77. The catchment areas with high background concentration of barium in their streams are: west of Conway (Llanrwst mining district), the water sheds of the Glaslyn Dwyryd, Mawddach and Dee, the heads of the Wye, Cleddau, Taf and Rhymney - Ebbw. 5.3.3 Cadmium (Fig. 5.6) The regional patterns of cadmium with background values below the detection limit of 0.5 ppm are located over the Devonian and Carboniferous rocks of South Wales. Similar distribution occur over Ordovician rocks with extensive coverage of igneous rocks, especially in Pembrokeshire and around the Harlech Dome. Background values between 1 and 3 ppm of cadmium are found mainly over Ordovician-Silurian sediments along the dissected plateaux. Patterns with background concentration above 3 ppm are located over known Pb/Zn mineralization. Higher background concentrations occur over Upper Carboniferous sediments running in a NE-SW direction, covering the catchment areas of the rivers Loughor, Tawe and Neath. This interesting pattern is due to airborne contamination from fumes of the smelters of the Swansea- Rhonda industrial area, enhanced by a natural high concentration of trace elements in the anthracitic and steam coal seams. The catchment areas showing high background concentration of cadmium, other than those already mentioned are the Conway and the Taff. 5.3.4 Chromium (Figs. 5.7 and 5.8) Neither in the map of selected class limits, nor in the percentile map does chromium show any regional trend, its distribution overlaps geological, pedological and physiographical boundaries. MINLX WALES - URQUIDI - CADMIUM GEOCHEMICAL MAP A. A. 1/1000000 GLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I I I ++++1,J4 I I CADMIUM +4.61++++ SI Bri. B 60 I I ' ++1+++++ IMO 01,J+4-1b0L-IgI I ; <0.5 +++++++++ 0 'MO.. Li eu,' I ++++++++ ..+ i3131:4- + 6 60 SOS +++I - b3j6++++++L I + 0.5 - 0.9 ++++++++Ju+TT+,-.) . IO 0600 +++++ ++B++I I ++++++133b+±±+k+BB36Bb+++0++3d 60663 ++++++++.1++TI I b 1.0 - 2.9 +@++,idt++1J++-+-+Ig++1J6B+++5+++++-13b0 ++++.+++.I I +++Ub++++++++bl++-Hob++++++++++++1jobb+ ++.+++ I 1 0 3.0 - 3.9 b+++++++±ab3 6B+++babb+++++ilbab++:14.."-+ ++++++ I I ' 336++++Odb0 005.6+douddb++++++PLid++..+ +++++++I • I § >4.0 dbbb++++bba000jBbbab 0+++++++++++..4 +++++++I I -11- udd +++++i 000Jbd2du u+++++++odu++++ +++i .1 I values in p.p.m. • .1++ +++++++dJu• dObbiT+++6,3 +++dbLidubd++++++++ .I I ' +++7+++++ tbt366bUi3ft++++++ f++ UBOOBO+++ ++++++ I I .+++.+++... li+dti_SEsbb+++++bo++++Obbdodo+++ t+++++ I I ...++++++..+++++++++Bob+++++jo g +++++11 I ...... ++++++.. ++ +++++b-T-T++++ jdb++ ++f l=+:++ ++113 I I 00000 ...++,3+.. +111 t++++++36J 3u33 +++++++ +++++3I I ' J.71 • • ++++b++++++jObdib6b ++++++++ +++-.11±i I . 41,2_411••• .. ++++Bob++++dBbbOudb0+++++++ +++4-.1 I +++.4.„ .. ++++ +L++++3j0b.++++fj±++++ ++++++.-FI I ' .. ++++ bob++33bbf++++oob+++++ ++0+. +f I - ++0+ ++66Addri++++++++6O+++++ +++++I I ' ++++ +++uoubJ+++++++++u +4... +1,++Di I . +++ +++,3-foo++ +++++job+..++++++++I I - ++++ +++++++++++++ ++++jobb+t++++..+++I I • +++4-4 +++++ ++++ +++++++++ojojoj+++ GOO II . I • b +++ ++++1) ++++0+++++++++ jj600+ I I ++ dB LibBb++3313+++++++++0.0bb I •I • b +003o+ 666 d+++++++++++d3013o I J3663 6J LiBBED u++ ++I I b3dBMB++ ++61.366 ++ E,.fl I +ootid3O+ t+ob o++-, *'1 114; .. I .t. 3b[a3'++++dD uti+ +++ re I I ...f.+131- +++0++++ ++ ...I I 1.++UU ++++.1_,L* 4.4_ ....I 1 b+++++++++ ++++++ + ...T712 +++++ . • . I 1.4. . .1+=4. I ++++j ++3E3 ++qadb+++++++++++++++ I .+++++++++dubbb+++++++++++++ +++++I .....+++++++++ ++++++++++++ ++1 I ++++jbob++i-+ ++4- 4 .6+1 I +-X-L3J03+1 ++++A.+ ... I I I ++ ++++ddb33313,1 ++ +++f+++ 7L.cs,+++. 1 I +++++ ++++Ibb3b60:3++ +++4+++ +++4++++4.1 I +. +++t+++ + +++++,d3604,...... 1- ...... , I I •fj ..,•• +6,4.+4 4-f++..++...„+++++++++++++++++±/ tif T++.04-udui 1 +++,,,, +,...,..... ++u+++++...... +++++,,,,I I +++033du+t++3+++ id ubo+ ++ ++ f+++++++++I I ubddbubub+3+++3d6b130 ++++ +++ l++J I I +i-uujTubbidu3+1g+didubd + ++ + +++ a I I +4++,33656F1+t+i itit3Li • 0 • I I " TT ,++++++++++++++++++Ud .. 41--4=13+ +: I ' OW++ 01-4-1( * )i. +...+++ 000000A-3t1+4 I ....4-+++ _J+++..+++3,,.. 7 ..1...71DM0004ad ..++ I MG* .++++ +++++++++++ua ojDOL500J+.. ++++ I ++++ it ** ++++++++++++++1 ..+6) I .• • • . ....+11372+++ObH++++++++ ...+ I • ++•.. ...++udJubdiodu+ ++ I +++. ++ 3LibUu430 +LS+ I buoduuOUT3b6L+++ I ++11disUd 1000u+ 3 b3L+++. +M++IbMpb 0OBLi,f +++. + + •...++. I .1++ 4+++ ++,J++ + I +++ ++0 u++D I +++++ ++13 I 3 + ++ I 11.)+• • I- •+ • i. I lib++ +-I se ++ I Bo+++ ...+ I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 • Fig. 5.6 MINEX WALES - URQUIDI - CHROMIUM GEOCHEMICAL MAP 1/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I I I I I CHROMIUM ==-,3B B BB BU 0g3 I ==BBBBn @OP@FiB I I . <10.0 ==913B333 === 9.4 04 === I Bi==BF33Q3-33391: ===9 I + 10.0 - 19.9 0101== BB P Bel3BBBL, Iii. 9_15-600 01======BB-Bi==19BBBBBBB - I - 20.0 - 39.9 8I7-9 B &== 9B9BBBBBOBBB9 -- =1":T.(Till1=1" 33338BB3B131iBB== - 393 I = 40.0 - 59.9 -1.BBOBE3E3BBBB3B _ ....--] -ti 19E39E939bl -- • I B 60.0 - 79.9 ___j ------__ ====7 _ _ ------=== --I I e 80.0 - 99.9 a ------=-1,J=- -1 BEIBP, ----- E I I 0 100.0 - 119.9 BBBBB ------1 993B9 I U >120.0 9 33B 3E131- 331= -- I values in p.p.m. t3B3B9B3---- 9B013993[3===--- B9B391== 1888BR9F'-- I (BBB BBB-999989-- I -7-DB3391339RBBBB====BBaj I BBB9C:133P'=Oth39 I BBBBBB3E,S3- ..,- - I BB==9BE3BP39 fo88. = - I BB=39B3BBEIBE'. 1, BB 3 913,33B I E3 ==3BB8BBBBB3c336===39:3B3BBB3P I ====..'en . , , ==== BFIRBP • I 96395 3BBB3B==== 9935BE I =====39BBB BBBEBBE=== 39F3308B5= -1 I == n9E313 B '19 BaBBABi3H----- r391,3C3BH I BB 38Bj=== 9BBBFIBB==OBBBB39B33BB9===.1)0I I BBB====RBOBBBBBB 3SBB9RIE,=B9BBBP-==!J9 OT I BB 1(1119PPRBBSPBMB93BB9e7 3099Q. I =BBBBB PBBBBBBBBRBRBBBBeBBOBBBB 23PW' I ==3B3839==qBBBBBBOBBBBBB3BB33BBI39 i t "r I ===3BBB====9011BOBBBBBB0593B9331329 3'233 1 I ====330B BBBBB9B3BB338953BBB 383BT I ===3.99B - - - - -ij -7=3BBBB9PBB9139B3B017 k3H--2.f. .J.I. I =17.1!.]- - -k - - -0 B9,I ''PBBBBB33E3E3Bt3== r .i'..=-3-5:1, I 81-4'3Firirn I [38 FIC-21.-4DE3B3===,3r.;.-Ci gliFf I JI-St.3:33B====E3n,q_%. a n :3--== E:itj3000±-91 1 • 11 3931389P9.3(39r11-31'. , 'EDnor1577, 7-5 I BB====39B- 3 3BPn•99P9BEIBBB8BB3 -19 E.*.i.:ie.`-' ''', .`--)-14f-)I I BE11- -1==== 1339B :_39939===:31413BB9BABB950===eln_L3"ali1J.ii-M I 9BL3f3".." 33 BB 9:4 === 9 E tv= -38E313= 3 BBr =4@- -703C.11_': -' 91.1-f. ,.3... -1= 7.1131 • I F3 ==33E3c---71b3l3F3E3B3=== 3 313 IP `1933.99===3n#J3c3===3n"4090t:II="?. "j-=.P.L=\_=4 I e -k ivl 8 1-0.313 B 13 fl B F-1 Eir3 !I 0 ) 3 3 3 ° q [ = 3 PSC. '3 '3 E3 = = = = 13 r; .EI, -.?, n = = = -3 (3 z1 a t, 0 0 0 0 _69 ° 7 3, 2 :-:fcr 0 Ch4 I B=1389-=3":IB3=1.5=939339BE31333BfEl -33B3BBP .....9.-39n =3138[3i.-33BRBBBB9.3 31r= -30-L;DLTO-eL: .):,-q30 -1)1 I ==12B(33===3!:31.3 `[email protected].', 3nP 3E3298B:39999 3 31.-3B:_';L-2J 3983 3 b' BB 3813:3;:-.5',3 BC:133PLERIEE''" -DW:Ci--f_TIf: DCrAt'3FC I====InnR === 33'3 Qa‘'±.3933E33[39'3913333(33BE3D3=== 13:-2 BB:38 DE':,139-381 :-,54P1:1SOM:r1E -3ei:11.4 0 I t3I333n?n239B5B r3[3 9= 939BBRB===9 =Bf==q3BPBRE9E4q 3:3 3"=000gI17.. 40 I L3:1=-93BBB3B36,3939BBB--,31 399Pe99 3[ ,'=1) 00r?(-:00- I = = 33(3= - 33393B33d3339E 91331 =-- 0== === - 3n - :i`;0t44 -:-J -3' I 8tJ31 98_9€11-----1313388333.= == BB= BBB ===BBBB3= 4`0 -;::I .Of,'20;=w== I t3IBP93= 1BBBBP==== 8E3E30 3 3tilte.Let4= 3= Ben ====nallpstl.: .- ..-)@3d...1B==- I °IB .3B =-= 43 '3 = = = = 9 '3 B B BB 3 3 4 4 CV4 3 ii ...ifir 9 3 Ell 9 B t-ABBn99 r'='#° jc= I ===333B ===.13 E----FEL ;4Pp,...6;::3===r3F RFAR9e2P9 F...e.P ,-)0'g ==== I == 39933 = :-1= 1_3 631 3 33,31 3 J. •--=4-9 I =9339 13J-43 (3 -3E1= .74pG6 BB,-.31gi-,. lirfa==== O- ,, f4,t:, I --- I 338 (2., --'4E1-1 , 1 ----111 wapai 1 I 3EIBB I ==.3BB I I ==-:, I Elrj I BJ I I I+++++++++++++.+4+1-4-1-++4-4-+1-1-4-+++-1-4- +++++++++++++++++++++++++++++++++++++++++++I Fig. 5.7 • 9▪ • MINEX WALES - UROUIDI - CHROMIUM -GEDCHEMICAL MAP i/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++f++++++++++++++++++++++++t++++++++++++++++++++++++++++++++++++++++++ I 1 I CHROMIUM --99RFT:=-7, 1,01;1 Ofgefli I . <30.9 ==BEEE91 -++ EIPPe eg -+++- r 151==.999BF=,? = B=+ ... FFR ++■+ I , 30.9 - 41.8 00==LIFEEr=n= P-+ ++er -=ETBnEr= - =;', EflPF, =--++' I -==FEF9= 1 =R+ RFFEBFFP 7777717 Ft414PCj'9 PI B== - I + 41.8 - 49.1 =-9P6FP =••••• •■fi. 4.....== P n frfFEp FP , „It t„_neeeennrinn= - I -1EP1Pr..- 4---rnrff 1 esatat- P=-+ 7 9 9 7y = `11:..F2 f ==== I - 49.1 - 55.1 jwi +-+-1FP9RFFFIef===- 7 9 9 9 T 9 ++== =4...... =■4. _ _n____9nfo'n====4 I -111 ,,I+++,411-=+++.•”+ I = 55.1 - 60.1 n ---.+ 977 99977 "+'''' + ...Eff1== ... +++■■-++-.+...”=-..+ t,++”■....4 51 +■+ ++,==pnp===n9_ • I t3 60.1 - 65.9 ++ +- 7++=-=° ITirt+ ++--.-====pc.E_ -- + ++-+++ 9 9 9611.- I £ 65.9 - 72.5 FEFP- _ +++. 4- Jr +-= = = - I 444_ =---======“=•••■••++ 91"-2- 41- I 0 72.5 - 80.5 =;7 1--==90p=1.++-= I --,,+-==gB9R-i, --+ - nEEERP-++, Woo I + II I o 80.5 - 96.8 4--++++-+ ==== . ==PPFECER= + 7 'Yes, 9'0 =„77..----4-1-+ E- 74.- + +====--=BPEEEEEP-+ + + N====-4. I ei >96.8 =--1990----- EfECEF.R , , 9 f f;9 ; : ; 416,:j I R =On === nfq9==--+ +Jr+ (1.m I =frEEPRRPEIFFTER ====RE1==-+++++++;;;',1+-+ /7 1 values in p.p.m. BREBEIFFPPeeEP ==-=-=---++++--- , , I —, .„ I , 89PREPF OOPEr - +- = - 9 f 9 °'' 0 +•• 1 PERCENTILE CLASS RR P,Dpener,_-_ - -9FER -Til,++++-=n, I LIMITS 9B 9EfFTiee4E_ R===f_Ff,P' 4411171 +-R131 I 99RFEffIPEFFIn==-= ''.4- jj4777 +" I = ---=9RPPPFPEFERP ---= 9 9 9 9 9 9+ + I ---==3EFON PEEFFP= --- 9 9 9 7 9++ I ---==1FEEF rfFFEER ---n9RRPF P RF= 5 ,....) • I ---r-rin===n figgEFEDP ==sREEFill=leFFR = + 4- -=j571, I =_E-7E--= =--- FfEEF9R nPFFETTLTF -4++ rui.fl BB9- -RFFEFFPRB .74-4-7 4, Jg2 I RB9REFFEFFEFRFFQPF9=9F c- FFF = +- -43 ==BBR9R98BRFEFEFFEREFPPt=RRFFEEE R = 4- + r :4900_ I = -=BEFEP= --PREFEFEEREFSeetitl teEpn=i E:FFc 1 I =- 9FEE= - + P9EFFCFE R FEafE f FR =-- BREE ' +-+-=E91=-++-R RREFFRFPF9REFFFEBR ==-== I • ++=-9 1 11 == --+P=P9R RFPF9BPP EFFFFFQ ==--= + +- ,5112F..:ERn;pngtp,pnno=-+- F.L.r 4E I +++ ___-__nTooseFFP r5:1 4+°4'71" + PPP I-1,===1 --- PoOMeFF -==r?;g=1,314 I , qaPARF1===FMTP= q==-4...==______-4.4.--==af:AEFEFPPRF.e,nflF= ====mkgICTInNr. I n9==-===-++++++ -9EPt!FflelFEEEFFPP= nnr, 4 I q9En===-1 -+--++-== RFI P ==-9F?).PFFFfFEFRP!F r F n Itfl f:1 1:', I += c.cfn=-PPPOIFFFp Pflpc)00fIqfP71 771,1 1 ' =4- +-=.19BEEPR=99E 4'EP ==e0 990 -= ..4.F:E==-EF-10PER R11;401fl7ridtIFF OMn1 I =-4.4.=:.d9RFEEPEEFFf40.FBRRRFFF9p= :DeEP====.--9F 3PP,qP IF•'nuP(1 -2V! -I;lrie I =--=9 -Fe Wl#Pflgf)PEFFEFFFERFE, Fn ==r1 PfEcnnn RfPflePT:963f)M InM1 • I --====-==Bn;7,9,000fFeaf4egt:pErT.PilfrEc F9 R (Ifffa- nFOO1Per=17:L,IIT:! 1 If-- ___ RFf-fifj.*:FC-PPPeeFEFRERFEEFE,1 pc1F9Rff- F4Fp, er-IfFneLIMT-Tun, 'I9t.if7- 7;)o '3 I IIQP,gfRWTggeeesPr-n9FEEn RFI7ERnP,EFEE'in,14- Pi Pnen0gF - _.;--.4.4. I 4-...... ==lannr--.1=FF F=-= 9 FFFPB RfeERa5=4127:AnOeq221TE.) I rInFIRR.igc_FEFf==.f[a2pep,f9f=ff Piz- flt-T-=r.--=n7inorAnnoa==.4-) I 9- __ R9R99-E-EPDRFFFRBPiPPO=aF P- BRP= 1RFJ7R:5:11ggeOPPOOW=- 1 I EF9 99 REPFB==RR tPtlIEEPFPE1 000g=+ PRE=- +7,minnr:VIEFffaqeepa9e.orp=4. I 'fif,B9= -=39L=.;==RBFF PI ,n ''E1 4--==r79,Er..= 00 0-_-„,p I = 9999R===0 1199FRF:211=7= 1-- 1 ===nnn9=== .:...7. FE3== ... F A111:T;q41;; ;; BBERB - 9n_ 1 _ I .1.4.----- m ncFe.e:]=+-+- ';" +__i_cf.20e1=4.4. I .1---====- --++++ --- tt, 4.--....1.4.+-4_+_-=_p 11,-.71:114. I =P I ,,----4--4-419 mEMO 0001DF 1 I ,••=”++++19,=EnEf I 7.11,142)+,, EITTP,RE -=E I ++197+ I ,A+++++-=np I „14.--4.41.-=BE 1 1 Itl-+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++W Fig. 5.8 80. Background concentrations below 60 ppm occur irregularly over all the geological formations. Higher background concentrations (greater than 100 ppm) appear over the Devonian system relatively much higher than those encountered over Pre- Cambrian and Lower Paleozoic, which are in the range of 40 to 80 ppm. Localized background patterns of higher values occur over Pre-Cambrian rocks in Anglesey and over the Prescelly's intrusions in Ordovician rocks and similarly over the western flank of the coalfields in South Wales. The catchment areas with high background concentration of chromium are: Dowey, Lugg - Teme, Wye, Usk, Cleddau and Loughor. 5.3.5 Cobalt (Figs. 5.9 and 5.10) The regional distribution of cobalt is well displayed by the percentile map and background values higher than 20 ppm occur in streams over Lower Paleozoic rocks, Forming a very distinct regional pattern compared with the distribution occuring over Devonian and Lower Carboniferous rocks and similar patterns cover the Upper Carboniferous of South Wales. Back- ground values below 20 ppm are distributed over Devonian, Triassic and Jurassic rocks. Within the Lower Paleozoic rocks, patterns of higher background values (above 50 ppm), are found over the mountain areas, with slightly lower values (20 to 50 ppm) over the dissected plateaux. Mynnyd Du, Fforest Fawr, Brecon Beacon and Black Mountain are lower in cobalt concentrations mostly below 19 ppm, similarly valley lowlands and coastal plateaux. • MINEX WALES - URQUIDI - COBALT GEOCHEMICAL MAP OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I ++++++ I COBALT 5+++++++ ++ ++ I +++++++42 ,74++ +++1... I I . <15.0 ++1+++. T+++ ++ M.] I +++++ ++.i..o+L. +411.14 I + 15.0 - 29.9 ++++++ ++.+++.. == +++++++ I ++++++++++++ +==== +++++++ I = 30.0 - 69.9 ++++++++++++ 4++ I ++++++0+++++ ++ . . • • I B 70.0 - 99.9 ++++++ 3R - + ...+++++++ I +++ BB5B.3 +++„+++++41.- I 0 100.0 - 149.9 +++,--- r3Brilzu3 BB ++++ ++++++ I +++=L TR o9OBBBB + ===+++++++++++++++ • I ill >150.0 ++++csi00,3 09.3R300nBOBB0 ++===+++++++++++++++ I +++++ 3c1000nooel0er3P +++++o++++ +++r . I. values in p.p.m. ++-!-E=1 ,-,' 011PLIQO 0ff +++++++++ ++ I ++++====BBi3BH-9ThEl,nE0 ++++++ I ....If++ BBBf3BP0 +++++++ +++ I 1+++ 1++1) B3B9RBBBB ===++ +++++++ I ++=r3BB-=1BB B9B9 2 ++++ === 3 3y ---- +++ 3 I +A+.7 P1F-74- ++==B--===BBB rEn . I +++++++ ++ BOBBBBBB ++++ I ++ aBBBBB=== +++++++ 44+44++ • • •E) I + ti3B9BBF3= ++++++++++++++++++ I•••4 . I Lq8 -3B ++++++++++1+++++++ •• f • I +++++++++++ ++++++++ •• I) I ---313 P +++++++++++++++++++ I 4+4+++++++44+++++ 1 I ++++++++++++++4+ I BO +++++++++++++++ 3 1 I BBB ++++++++++0+++++..-F-+ 1 I ++ = BBB ++++++++++++++++,-++++: . I ++ ==c3 +++++++++++++++++++1;) ++ ++++++++++++++++++++T3 qiiR3B BB 0+++++++++++++++++++3 I ++++++++++++++++++++3 I B3F = B BB ++++++++++++++++++++I I FIR.92 I-+++++++++++++++++++ 3 I 3401=1R 0 +++++++++,,++++++++ I I 3SOC...,7103 ++++++++.„.++++++++) I +Li _ Pineey- 39 ++++++++.„,++++++++) I +++++===.4+++==n015 -, 9p +++++++++.„„++ ++++:1 I +++++++++++++=00000 ln=+=+++++++++++ OOOOO + +++1 I ++++++++++++++== 306 3B==+++++++++++++++6...++ ++ ) ++ I ++++++++++4-++++7-313J-99R ==f++++++++++++++++++..+++ I _0++++++++++++++++++=33q j+++++++++++++++++++++++ ++ I 8 ,44++++++++++++++++++ R9==-++++++++++++++++++++++++++++ + I + "4+++++++++++++++++++++++++++++++++++++++++++++++ + I .. +++,++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++ I „F+++++++++++÷+++ +++0++++++++++++++++++++...++++++++11+++++ I ++ ++++=++++++++44 +++++++++4++++++++++++ ++++++++++ +++ * I ++++,++ ++++++ +++++++++++++7T++++++++ f++++++,"+++ I +++++++ +4 f+++++++++++++++ +4+, 4 ++++ +++,+ I+++++++++++++ ++ +++++++++44+41- ++++++++ 4+ I +++++++++ + +++++++++++++ ++++++++++++' +++6.0 ..... 1 ++++++++++===++====+++++++++++ +++ 4+4+++++++++ +++++ I ++++++++++++++++++++++++++++++++++++ Ett+++++++++_!1+++ . )++ 4 . ,ff77-+ I +++++++++++++++++++++++++++++++++++= BE==+++++++++++++++ t+++++++ .g:7 + I +++++++++++++++++++++ ++++++++++++++= ne,==+± ++4 ++ I ++++++++++++++++ +++++++++++++ ++=-- - +++ + +51++++++++++ L+++++++++ +++ +++++++++ I ,+++++++++ id+ ===++++++4) =+++===++++++++ ..+Ei+++ I +++++ +++ ++ + . ++++++++ se +++++ .iii+++++ +++4+4 +++ ..... 000 I 4,, +++++ ++4++++ +4' 114-0/0 +4 41:==++++++++++ +++I.++ -++++++++++ +4 +++++ I =44+4+1 +++ I +4+ I I I I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Fig. 5.9 MINEX WALcS - URUUIOI - GOuALT GEOGHEMICAL MAP OLOd-PASS 1-1LTER USINU EFFLGT1VE RADIUS OF 1 CELLS It++++++++++++++++++++.+++++++++++++++++++++++++++++++++++++++++++++ +++++++++ I I 0= 4BEE COBALT -= ++1, I ddlidEE88 ++ I lidEEEET:= ++++ ====±±)-, I dE4t9E=+ , jj• • ++++ =g W. <9.71 =--= WO I ' ==18E to +1 ..111/711 7/, -==WdBEE- +++, 00==-F3EBEEEL-, 1$17/1U± / 1 / f 1 / 7 • • • I 17•71 •■ 3.3.74 40gtLi3i..$EEEEEE- + I I -==li.liEd -+ --.- + = 7+ 11 1 1 7 • I 1+ /11/71///11 ++"++/7,1,9,17fl, ===b8=r1-0E00004EEE0E000E- 7/111 I 3.3.74 + 16077 / // +++-='.+++,.,,WF / LiE3b=dd E0004EE00000t;E= ,++++-=-•4-1-1- =-31.33O=EE 001100000000 EE== + /1///77 I - 1.6.77 - 19.31 9 ++++--'+++'' I .1---= 304g-65(5a11000g00( EOU =++ /WW1 .- ):.tJtJonEn110000e0004r:,=-++++++--+++- //1/// I = 1901 - 21.86 = EA0000tralilliflan 000E-Li= --- - - + :: : I * B- di, namonnstimiaone JoG.baqduri=-4LT=--+: ; : • I 13 21.86 - 24.97 1 :41duziocgunannonoutionee ook:ii.)-1oLIEJ --- + 1767/7 - I £ 24.97 - 28.99 =13EWOOLACCIEGHOUillinGB000000EE8b==== - =-+ • • • • • f t. - I. -=-BL0040E0OCUMWOUGU01100000000E8====- =-•••••••1:1 7 • • / t 1 I . .0 28.99 - 35.51 1,,J+==a1A004g1 goori,milananoeeogoo6.m4Ed.„, 9 , I ,,J+++--8E4000'=E4000NUflOUB00000000 Flin00EEu=--+++1..,1, ++++--- 0-a0efir100000000000TfirleciW,L;=++++ .*00,406 I 0 35.51 - 51.66 -+++++ I - '''++ • 00110000000n000110000 50000t 11 I g >51.66 -u4otacJgogoODOOnon0000tgowLu-+++++-++ ,, I --t05000000 neneaoociio,iLiiEu- + -++ ,,,, 050000@0000000000 Et3o386 - 1 7,_- I values in p.p.m. I 00000000U00000000E88 80EEI-a-+- =- 111, oofmmonougot-idad dEE8-- ///1 I PERCENTILE CLASS I 00000000000000000E883881===u8Edu=---++ Mt LIMITS I " 0040t)000000000000EEJJULiu888obdo.3;=-- 7 I 1 I ' 0000000000000000000 - 3888888tio830=-+: • * : : I • t0000000000000000000Euodb8E1888Eo=-+ ,+, I ' 000000000 000000000Eb3u8138888Eu=-++++ + ' I UtdS00(1000 00000000tEEEOO888861.1=-===--+++ * I 813"3M11200 0000000000EE830B8088o +++ I ' EuEoannn 0000000040EE0do 8 3 +++ I 0 #1Jgonannootmeow,r:Eaa 1 . 000uElg000gnommoo8EEd------+++-- I - 00C:1000400000000000000E88 ++++--== I - 0@@40000000011000000000E88=--.- ++----= I 0000#0000BM000000000EE8===--+++++--==== I - 4000000000110BUBB4040400E8oa;==--+++++ : I 88)=0004000010.URBaR00404d0E88O==-+++++ I ==-== 0EE - 0030013000 EEEbisTL==--++++++++++- I B8 ;yEE ormaummo EtEEEBO====+-++7+++++n++- I ==d8Eu =-=8dEEE0o 4rinpauo EEEEEEEb8====--++,++--+++- I B===38EE3 = 8EE 4t)oorineoo dE6EdEEEL3===--+-++T+-==+++1.?_ I +-8883,38EE8 86E0000400gEoE8EoO ++-__ I +-++- 08A-aluouLid8 === u00000000t L36 ++--=-+++- I -+-++-=_1(388odo I ++ ---+++--==8,i30888oJ=JoEE I -+++== ==----=-880EEEEEEEtCgaso-Eud , ====--++++---==-+ +-==--+-+++---- B-++- 8072E68 888..3L;EEp00s0_0)EEE0E8LitE ===-++-,-++-++-=--++, p++.".=+.1.....+++.1.- -++= 0E(04461EEEEEEpL000001tEEEEELWE = "11- 4. pi +4--1. 1- pplppli- +++++++ -1- =oEtEt00040EE 00EEEkus0EEEEE08o --++++++T4+-++ +,,„...,++++++.1„,„ =L)8ELWE40000EEEEEEE88== JEE8 ==.--.../ 41--- -1,1141, 7++++fr/0,17/ ++,, ==O8dOE40006.01E - ELJ',;=== s' - + + / + ---"-k/ 1 / / 1 1 1 1 J33oEEEEEEE EEEEE =--===--+++--- =__ ___E, =- , ,+++++4:t c,„ o8o J88J- =-+--====-== 888388 0==== ---- ====-+--== JE0 00 i =Li00 ====-+ , • , , , , +++-• +- - 3t3, ===368-'=--+--+ ----===8EEEof1R0 E11300 EasEE8E ••••• ++ ++-- I - 3EL - += ==oEEE8EE000000eEE00 EE +-=1.38=dEEEoEE,00000 tut: 00EL I • +m++-++-=buu _.:E..7.7.= :i-H1:::-:::+. - - + -=61-E 000t u 11••••, I ,ft+ 4 +- fagE8BEEJEE0EE - 4.4- 4f 4gIL LE LE0s;g000EJDE==--+++.--=- - , , , • • • • 7 11 go(50000..6E=4.1-„„0-+, I ,11.4.4==. @ ew0.6,bid,=-4-„,.,0f-t-1-41,,• .....„ 8E00Euu=== ==-+ /7117 --"4'74-1, -=4a- I B t- ±±/// = Eb= -++++-+-q„4++ -7. I 11•1/1////1/1.1'= I ••••111,,, I 71, I 1//• I J 1+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I Fig. 5.10 • HINEX WALES - URSUIDI - COPPER GEOCHEMICAL MAP 1/1000000 OLOH-PASS FILTER SING EFFECTIVE R4DIUS OF 1 CELLS COPPER +I--l=... • <10.0 + 10.0 - 19.9 20.0 - 29.9 = 30.0 - 39.9 B 40.0 - 59.9 • e 60.0 - 79.9 c· >80.0 values in p.p.m • • • • • MINEX WALES - URQUIDI - COPPER GEOCHEMICAL MAP 1/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I ONO COPPER 0@t401111 0000000 ==T .5E0 f40 P f= ==.3 EPO PP@ I ▪ <11.0 EEEE6= +- 0 =-++ =3=8 0 7:- -E1883r=-9 00000@ POPE -++-E .-=43-B -+++ I ' 11.0 - 15.0 - 30--+--- EE0A010900EE0 F =4.+-3q= +-==-+ ++-.-- = BEEgaLPAELPJF0EPE3=+ +=3E1=-=3==--+T)-(BR6 + 15.0 - 17.8 +-=0BB==-=-==99BEEEEEE14003S =-4. -===--3EE3==--+=f755 I BB= 333 REE0CEEAOPE3=t--- =BOBEEEE=--+-=713 I 17.8 - 20.1 -- 1-EE3E050EBE E3=5=----==BE Bi3g===----= 0001 OPEEr] UEE5==a3=+++--BEE I = 20.1 - 22.4 E000G FO 011A-- 35==1i1===-++-39 c,i--- 1:7417- • I += 000000 EtEE3B---=--+-====BB=-=EgEEEB- ..1 -- B 22.4 - 24.8 ++-=.0 00E100E00E3 --+-==BEEBBEE.E031=- 1, -=- ++---BEPOOP000P EB --+-=-13BEBEBIOJEE131-+,,+-- f. £ 24.8 - 27.9 1++++-=EPE4POPUO 114333)=--====EEEBEEB=--++, --=-11 IP,' " 33BqB000nMO 3==--====_=BB,=1.13D=BL3,-__++,===— 0 27.9 - 32.6 4--..-==- --- • 111, EE3 P00000====--=--==B BE5E "'TY, 00E000 f :=17 -ffai41,3E=== 9 I 0 32.6 - 43.2 PLBEPO -=WE3==-404 PEE B B 61-31-4- T= =g -=3EBE00004L143EE000, PEEBEE BE I N >43.2 -=BEtAOCEUL30000WEEEE EE03BOBE I 8300UMWO OPOPPEE35 3====1BE I values in p.p.m. 0 Ot,0 00000POPIrf033 -===BE 000EtEPP0000040.3 3==E; 00 I PERCENTILE CLASS OEBEE00000000033====-3392 08 3 LIMITS 00E0E0000P0004PEEE9==3EEEEof PP EBB =- 1 4- 11, @EP 00000000044EEB==3EEE0000 PEEE00000080000333EBEEEC0017C1 E= -+,,,; I PEBEE000000000011050PBE =-+++++ OPEBBE09000000000000000 - E0 Do===-- (PEEEEEEN000000000PEJ3CE 1 0 E33883 BEIBBEBB 000000000 111==4-3E 00 ‘0PGEEBEBB3 I EEEEEEEEPO 000010 - 3- --Bi0 0OOPEEBBBB3 EBB PEPOOPPEEEEfP BE EEEEEBBB[==- - I EEE r.f000EtEEBEE3- + -5 EEEE3EBBBUBla £[=== 00@En BEEERIBBE .4.1..-= EE833333EBB9 I B=== €JO@C===E81.33:33B ,4-- BBBBB-BEREE =-+-= 000E-£ t 3E1333=- - - = -v-- EEEB33 I --J7+=1E0PE=-, £f E 3BEEJ==-=--====-=21--71 9B11,=7 E=4- 71,4--13 LQLEJ6Et EE= BBEEEE3BBBB===-- I =IBBB-+ + 3E4E2ij=- 3033,13P 3BE3-- -+ -=--++++-3 ,,3=-===BBEI BEE,-.,- LIEE 33 I B =■■■== 3-++-=-++---=3EttBa--=3BBB=== =-331=-=JBEE BE _ -=3E3=---== E6=---+++--==EEBB93---=390== ---- =EEEddEOP E3EEE ++=9B--==== 3E3-+++++-= B;3EEBBB3 = EEEB3F0 659'33 I -++++-11336031==,- 3E3=+51+++--B33-- B. , 3BEEPEEEP0000= I B==+---=-==FFF63L=. 3r3q- -C++-==B==-+-=9-33B ===95693BEE0OPEEAPP40 I • f =E33 13E000 , :3 --+ -++-=3333 =6335E5EBBf4PEEEEELELBEE I 3EEE3369EAfj10000000000E == EB -5333 ==9BB3BB3=BBPEEEEBBB=43E I =4-t--i3EHOP033EE00000000f5 - EEC3===.3==- ---= E3 333 3BBB-= DBEBBBEB=-+-E1B • I 11=13B EEE0aWEE0400 111004 -AB1===-1T33=--- = ===33306=3B4=++-= 33vB3=-+++- I =3=BBBE0000000000g00PP000JEE3BBA===3333=--= =--"q)EF=-===_4. 4__ 8Bo==-+ ++ EBEEPPPE PPP E000EE,S,E53===--=3EEE33 +7714.--=+++--++ - BK=-+ +-- ,3_FAPPEB PP ....,,..1)++++ +-a0:5==- ++++ E.13f0tEEEEEEOPEE(9.1EEE -- BEP - LA IBEEEEE-'FfEEEE333EEEPPpE 0 + +===— -==p3B9A=-++-= I -== 3E, EEEEEEFEE:ZlEEEEEEEEE00000000 000=-+H. +-=13EL-lb- 3E3B=71=, I =-== ££r,£ £333=3£0 FBD3EEEBEEL0JEEE0000000 00n0q hiVAtIg000 -++-=333B=33 I === BB 3 EEEE33EE 3111,33D0000r, . ElOPIOS4:0400000(30F.F.,-++--==--==== -==== 33.3,1 33, BBEEEE1000000n0000 000011MMR006PEE0€3 ++- --= 3EDPIE31= 113 000000MP0000C00000000P0PVE3nu==,=- +-- I -= 3BE SOGS0200400E00509000KEEEE3030=- ++ I P060000 00000008000033= 71,3e- I £l0000000 (3000P00007000EB= 3-==E3 00g 00000400Effit.,38-=-==W,B0===5- I WIWEE3E3EB9====- f0 15-041O1£ I 004g04E3B93= 3 0I3F-l338 3LE I =-++-=3B3B I+--===EEFA@ I -0.1-====8 00 I I 1+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Fig. 5.12 • 85. Cobalt outlines the Lower Paleozoic rocks, host rocks of the Southern Caledonides metallogenic district, and values above 40 ppm occur over known mineralization. The catchment areas with high background concentration of cobalt are: Conway, Glaslyn Dwynyd, the heads of the Dee, Rheidol and the heads of the Teifi, Tiwy and Wye. 5.3.6 Copper (Figs. 5.11 and 5.12) The past mining and smelting activities in Wales have distorted the true natural variation of copper and no regional distribution can be defined. Background concentrations of high copper values (above 30 ppm), are found over most of the geological systems with the exception of the Upper Devonian and the Triassic where background values are low (<20 ppm). There are some higher background value patterns scattered over Cambrian, Ordovician and Upper Carboniferous sediments, Super- imposed on these variations in background,.there are a number of high concentrations with mean values above 150 ppm, localized in Cambrian and Ordovician rocks in North Wales, and also over Pre-Cambrian and Ordovician-Silurian in Anglesey. These high background values coincide with known copper mineralization. In South Wales, Ordovician rocks show a good contrast in relation to the low background pattern shown by the Silurian rocks, forming the structure of the Central Wales syncline. The Upper Carboniferous rocks with the higher values in the Swansea - Rhonda area display similar patterns to those of the Paleozoic rocks. There is no definite correlation in copper distribution with relief or soils. The catchment areas with high background concentration are: Glaslyn Dwnydd, Mawddach, Tawe and Neath. 86. 5.3.7 Gallium (Figs. 5.13 and 5.14) The distribution of gallium displayed on both maps, shows a distinctive contrast of concentration between Lower Paleozoic and younger rocks. Background values of above 15 ppm occur over Pre-Cambrian and Lower Paleozoic sediments, while background values of less than 10 ppm are found over the rest of the geological systems. Patterns of high background values (>20 ppm) occur over andesitic lavas of North and South Wales, with the exception of similar rocks in the Lleyn Peninsula. A similar pattern east of Aberystwyth is suspected to be an analytical day-error. The dissected and coastal plateaux formed on Lower Paleozoic rocks are well outlined. 5.3.8 Iron (Figs. 5.15 and 5.16) Iron shows a good contrast and a comparable distribution to cobalt, gallium and vanadium in so far as the low background values lower than 3.0% occur over Upper Paleozoic, Triassic and Jurassic rocks. Background values higher than 3.0% occur over Pre-Cambrian and Lower Paleozoic rocks. The Ordovician in South Wales tends to be the system with the lowest background concentration of iron in respect to the rest of the Lower Paleozoic.. Ordovician rocks of North Wales show an enhancement of iron especially on areas covered by igneous rocks. Within the Silurian system there is a slight differentiation of back- ground values over the Upper Silurian (4.0%), in respect to the rest of the system. 1/1000 U 0 0 • + 5,0 - = 10.0 - B 15.0 - 19.9 G 20.0 24.9 [1 >25.0 values in p.p.m~ ====== Fig. 5.13 • MINEX WALES - URQUIDI - uALLIUM GEOCHEMICAL MAP 1/1U000U0 OLOW-PASS FILlER USING EFFECTIVE RADIUS OF 1 CELLS I++++++++++f++f++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I a=3.=-ALlu GALLIUM oticiddii== ++ I 3BLJELU=-+ 411+ I < 5.14 r:ELEEo=f+ ++++ 111 • =70BEE6 =++-=-+ + 7•77776 +4+ • • , EEE et • • • 7 't 5.1k - 7.11 -=-LiodEu=---=-+ =3 I7EiE- _7= j E •777••77 +++ u8b6------==336BE4wEEEL:6+ 77777•771 + 4 + 7717 f 11 ' I . + 7.11 - 8.69 ===i3bduJUb=-===dULJE4004044Z- 1 , Me' f 17 1 741 I ===kibubji cA04/;4000040Wi=- + f 77 7 + 1- • I - 8.69 - 10.23 =====utiEt:044L404044 Lu ===- +-++::: ++ -==Jui:Et:Ef,40E.I.0404Lhouut,-++-++ 7711 7 I '= 10.23 - 12.1L -== t:44041:Et:i, 40 EbibbE:it:=-11+ 17 7 f 17 - • af0,3100UE::- 1EfOGILLJULSUUf.4E 1---'''' 7f 7 7 • 'b 12.11 - 14.00 udJ,;40000441404446dw'ELuEt:e.Et: ==- 7 7 ft I dEEt400000W(M)00000WdtAJw r:.::-:hEuu= 7 7 I E . 14.00 - 16.00 LE444400004d000Er000000004W i=1:Er:uL,=+++=== 71 9 7 9 'I' =6Li:400444wr440000tIORfl00000463EuLi;E=--+-+ • • • • I '0 16.00 - 18.08 +1,1+-thJig000r,,u.,tatmaboonmsne000 ..---+ 9 f 9 I ++T--==E 400 =-=o - 4/W04000CUUD50000 DV0004 7777 I 0 18.08 - "="- = +=41; o4000nntm0000nrnnao00 20.99 ---1- = WEEUE4000R2M10400r112EMMM4r I N >20.99 =.13E0b1Aomilunmeocnuaoe0 • I - - f,004om ripole.aotmo, 1 values in p.p.m. - 14t)t)00U1rhind-Wadda04.-it.; 1 ' WOOn0-10n7nnO0WWW4LE0d0buriu I PERCENTILE CLASS uorinnr=noneodoelpiit:dEbbLit:o I mananonntiocaottEt:EEEEd I LIMITS imaaoorlfAnn0000at wEEEEE33 1 000000m1nunuoneoof0EEILLid I OWWWWOCUMGOP0000E, Egbu I @WWWWOUna Un000W4444Litu====-++++ + 1 t:L4ncarl0 OMM00a0040EEEEbu -- „ 4 1 L3E4000040 ocinnam0000atli:EzzEd-- -U I 400000WOE 00a00M00044bt:EBB66l====u3 I GETIMM00040P130000004 I CrATV10000R0000000w440IL I MEMEM10000000000044wE I 00171134=040d000000000-ELbub======-- I 000=00044400000000044WEu6o I 4 00UU0000WW4000000004030-- I BEL 40400000000000444wtb3tEutio=- - + I ====0 44L4000 0040-? 4EJLWUULiOu== ++++ I --=b1====oELELt;4400000 JuLIE3tiu= - +++++ I ---:.=_OUdiLitEi;I:U,440044004,7:Et:EU33b3ddrib==-+++-==-++ - I • =---=uti:Lii)iztRititA404440004'7.6Lidoi_ibdchil==--+-++= -++-= IBELt=-=,EuLf.i:Er:LbgJu444Juww000r;i5 +---+- =-=== I ' ==--==o614==IBUi:Liii3UbatitaddOw/iE220 = - ++ I ==,==--=-13..uuduJJJ,iduW;i:L400wEEEEr:=E- I ++ --===UL3ubLEfiit.=tEE).:4000=1::Eou0P + ++ - ++ - I • +,+-==-Juif.4o0-14)if4444440isEE60004EkA=--+++++----+++++++++++++---== I =++/+-=LWEE4000000044000404w L400 4===++++++++-+-++ „ 1 ++++++-++++++-. • I ===-- -:--/./.403(501":1300J0dt.30.,344figc-7006LL)=---+T+++++++,, 17 7 17 i-ii-t i-i-fi-- I "----4.36L3E409W)nr10000:jdiA04WW500CF,0=--•-++7++++777 7++++--77717 1+1-"“-==j,30,itiE4OnnDOOR500.10041,4400C1 =--r74- 1- 741--4-,177 , 7 7 f++++,,o,,, I -=-=66.13uEt-W600n000U0d0t4E,bot. dx.ti'=--++,++++++---+++111 flftt+ 71•877, 1- Mi. , I -==ibJLiDE L'00.-, r.Jc.,==ii0.3L -1-4---=-7 ++4 4 ++ - „,m,, , = + 1' -== if===AUJuo,,tuLL.J ++---++ 4 +17 , • „ ++t+ +1. 1 71 i 7- I - EbU- +---+ --Tb.,1;7+-++,,,, +- = = =0 Eb E -+ +- -t,,,,f +5,,,, 1 ++--__=___=. + = 613EL - urf„„++, I += + + -- --,-- ,,,- I ++------== TN -+++++--++s 6660=-+--__-++-++==-f+, I +++ -- --mt:JbOo3u =++----:-57-,14- =-+ , I +++++ =u6dub=----++,17,1-=-+ I , I”)+++++++ -+--=++, 7 .. ,+-++ , , e I +++ +-+ ++ _++,,.,+==+7., I ++-+++++ ff, ++77 + t; -lidE0 I +++4'7 7 7 717 1 7 7 7+- 1 7 7 7 7 f 7 9 7 7 ) ••_, I 77 • • 1 7 7 7jf + ,meeljt++++- 1 ...7IT4-4-4-4-- I 1 . 1 Ii-F+++++++++++++++++++++TM+++t++++++++++++++++++444- 4- 4- f++++++++++++++++++44 Fig. 5.14 • • MINEX WALES - URQUIDI - IRON GEOCHEMICAL MAP i/i000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 I I I BBBBBB I IRON BBBB BBB -- -__ I I BBB +14-- <1.0 BBB 3 7 ___ tr;;;..1 I == B' B 1 „1-- I_ Br.r.= -I- +4, 1 + 1.0 - 1.9 91====3(3BB====--: td3r1=BBBBBRE--:L "ith I • B EgBIEEEBBBBBBBBB- _ I 2.0 2.9 8BEEEE3BBBBBBB- P-t I ===IBBBB08813898EUEBBBBBR88=17E=11.7 I = 3.0 BBBBBROBB 4P14£B80B8813888 I 3.9 8 3Bn PPn4E999BEEE0aBB I 'a 4.0 4.9 BB 3 £££ P PEEFf PEPEFIBB===:'---.. ' 191B cREf4PEE , .:EitEEBEIBB99 £ 5.0 5.9 ==9Bf-..P@PP ;400P@PP3PC£££E3BRB9==== ---03£4eOPPPPPPOPPLEEEEEEEBB003B I o 6.0 - 6.9 ==3809EPPfag6640005PP00£££££££E989311 I _ 33EF.Ei'Pl1L'. 0 00pOPPIPPOPq£CE£E3BB-- I ID 7.0 7.9 ____ ====RECE398PE4P4— PPOPePPPKEEEPF3B I I BEFBIEr7B9EPOPPPOPOAPPPPE 4PP 38 I I 1 >8.0 =3BEEEMP4PPr.'41a(PE g@flER= I .1- == =BB EE'PPPEPPoPPePEc,10eEEB /7...., I values in percent -s- ==BBEEEEP@WEPPPPPPEEEEEEEB I £€££££ ppyr£££EFEEB8== I B £££££ EE'PEEEEEN0803883. -- I £ ££££ FEEEE£N3d1383888833B= I BE 3£EEF E£E3B8883813 81338- 8RfBBBEEE E£E£988BBBB9 BBQ £Ett 33££££££££E2E3BBBB ===BB== £££2 LE£££Z££££EEBBBBBB BBBB 03B££££££££££TOBBB8838833BE BE ££££E£4 £££££E£9,8BBB BBBEE£38E4=== BBREEEEEI@ £££££££ BBB BBEEE£E£E38 B3Eav6EE ££££££££EBOB 9BP.F.E£E£E39 £££M££ ££££££££ BBB BBBBBBIEE,L3 ££££P,21££££££££££££92B8 Blifr £££££E££££££££££££3B3B 90P EEEEREE£££££££££££ El' A PEE£E, EEPSEEE3E PPP40 440@EF0PEEBBB FEEEPOP@Of4flOPP@PEE£F3B3B 908 4P 9PPg 99OPPEPFBBE38 B3B38 PPEEEE=100@d@EF:IBBBE 9 99133,39tE £££££ f-41PP£Y0888BE 89 EBBBB93E£E£E£E£CEPPAPEEBEIB8880BB £8889BB9E££££EFER PeEE£!1(399B3BEI m1930B8988RR3,3EFE031E ECEEEt. 3B=/--- 0 -----138BBBBEE£38 —80E ££££££££ 3B-F-.-- BBB99EEP33838BIEEEEEEEE£39FE 99 I =,- m..=,---B8118138t£E.5098983PLEEEWEEPBEB I 1-1====P817:=3BBBBBBEEE33B133B ££££LEF39 3 8-=-1..-J===t-4BBB8398B3B£££E801383130PEFI4P)C£99 ----DBBBRB 388 3£E EFBAB338199££EP3r--- , -1 38gWPF-,4E-MV3338:1£EPBN------:3 8£44PaPJC£££££3388BB ------MINgEPFIDUB3561B------iin ££W138------_ R'' ==BBB 4. 0•411M ==39R --P I 1 I I 1/1000000 • On4Ani-HLTE.Mill6 VeMETATAHAbF "Pi CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I I IRON I II< •. 2.20 == 1, I === 0 dBBEE131+ If 1 2 2.22 - 2.74 --==b0=-==-+ EJEE 00EB3BEEEEd-,,+ WEE0000EEEEEEEE=+ + I .+ 2.74 - 3.13 =1Add8EUEL,0000EEEEEEEE==-+ I - = =dEdEE 00000 f••EEEEEEELSd - + = ++ .1 .- 3.13 - 3.53 ==dEEE'0000000EEEEEggEE _-+ + ,,.,....I ===F0000S01511100000 -EZE EEEda.+ -+++ + ---++ .1 .= 3.53 - 3.98 -Ji: - U0004003000000dEE gEEE81-- + _++ I ==8E001.10000000000BOOEEE0 04d0 E dd=+--= + 1.,,,..I. f .13 3.98 - 4.45 • =71a0E0flU0000600000110000 vgogggE EE==-= +,.,,,, I -= ==4- WWI I I .E 4.45 - 4.95 --tiEuE.(4auwoodausaanneociestedot:t:EEci i---=OZE '4 OrMa23M10000an00043EEEdd -g ==== +,11,151±I lef + --= d GGEautsEdaoaanaanamflateaeoGg -Eo------+",..,„I I '0 4.93 - 5.50 1 • ',II, +-=1:i 014Lsr--bi,V3Ogeelle0ebalih3C1000 11000E,E==-+ , • •• • • t.,11". I e 5,50 - 6.31 -+ + ++ +u -08000110000M30000@o000gEd-++ , ,. , , 1 , ...I I - --+ --++ =8 aowilegoomoomowmaeaz------,,,,...1 1 4 >6.31 - + -SE0000000 00Ht100000090000gE=--+ WWI I —600000040 OU000000040000d0 ++ , , , , try. I values in percent =E0130040000000000040ELEEEddd -- •,,+ I I 0000 000 00000WEEEEEEdddEESE=+++=-+,,,,I I PERCENTILE CLASS 0000 400 000ELEEEEuddL300uEd =--- =-- ,,,,I I 0040 Od 040EEEdEEEdo U dobjE= + -- 1, +I +,,,++I I LIMITS 00 gd0000000EEEEEEibd dy== ---- I 00440000000000000EE130138 dud-- + ..+ I I 00000000000000400ZEEE130dOdEEE ---- ,,, I I EE 0005000 0000000EEEB8386E0001Ed== --+ --+1,i I BEE0000000 00000000EEBAE-76Egt0000E6= • r E 0000000 000000000EEb===.4E0000400u=--+,,j 0000000 00000040EEE6====1Oodd40406=-++„I 000000000000000040dB65 dLLL6-+++++1 I 00000040000000004036d- =++++I 00000010(10000O 00E4,-- ++ ++ +--T 0000000000000000040E8 = - + + I I • 0000000000000000000EE0== + ++---==== I 0000000000080000000EEtlEu===---+++++-====---I . 8n000t001:1013600000,glEEE0EE868.== +++ + -- ++I tkiddEOCM0002t1130001001EdEE0 1:Ej%== +++ +++1 +++++--4.4.R++1. I EE3BEE ut0000000001300EL88EftE8 rj4EEEdE 400000000A00000EEdoui.E3_L,- - ++++---+'V+ 1 ++---++++-I I Or;LEEEE'0000,0000000000000EEBidddq= + BEIg,;EEEE - 0000006 -'000000400100Eddu== -++++++ -- ++ -1 I +1- I BEEEEE ggEtEEEEE0000000e1 00000Ed%=-++++ -T I dd'0EEigugEEEEEE 0000n0EEE40 Ed----+++ - ++++ - +++ 'I ++ udBEEE0000tEEEEEEod000000EEdEu + -I I • +++ --= 4 d LJEEBUEE00tEEEEEEE0000300Et 36 u +++ ++++++----++--I I • =+++-=== 36EEEEdb0000EEEEEEE0000000E =-4--=-= ---++--==-++++++ ----+++++ I ++++++---++++++I lo I EE- D-Ji EZE 00000EEEE.JddE0400 - ++++-= f+ I I E -=-=-== EE 4- 0000004E0EJLIEEE000E -+++ -++++--=--++++----+ ----++ I8 00EE6--+--== LO0000000u4OL:EEE 0 I +++-+-+++ + -- 1 +--=-++,+++++++ + -- + T--==1 I E =-=-=--= EL EE0000:)0000000EZuuuu=-+ ++++--- + --+ f---.7--+++-===-I =---=== --- -- ___-_- I ++----- +++++- f+++++ + 0- ==- I ti-i---==--+----++++-++ 91+++++- EEd--+++++-+du1000 =-+,,, I / ++++---++--==-++ .1.---f.1.-==--===-=EEE +- = =="==-+,,,,,,,, du I ++++++++--=- +++---= =+--= --380 - + tg= =+ , 1 , 1, If , , ++++++--.-- ++ E - -++ -- - I A++++ tdB= == - -- - , , 1 i----+-4-+ , , , ,, , ++ I I ==Ejtj====-4--4-+ I t , ÷ i- i- -++ , 1 ,,,,, - I I 7 7 ==d6 ===-++++,,,+ +0+ t+-4-1, I ,1711-4-1- .----===.1. J. I T6+ -==6=---+FITT,,, 1 1 I ===.-+++++$1 ,77 -= =.747tj I I -- +_±.1, 2 111,1,1,1 +== I 1, 11,/f/t1111•/ I 11 • • • • $ / t 9 , 1 I 1 I **0/1,,,rtij4-i. I I 1,4.41,,,, I I I I i+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Fig. 5.16 • 91. Iron pattern with values of more than 5.0% occur over most of the mining areas of the Southern Caledonides metallogenic district with a noticeable difference in respect to the low background values found on the mining districts in Carboniferous limestones. Most of the catchment areas draining Lower Paleozoic rocks display patterns of high concentration of iron. 5.3.9 Lead (Figs. 5.17 and 5.18) Lead regionally does not show any pattern distribution in relation to relief or geology. A low background pattern of values below 20 ppm over Devonian sediments and over Silurian rocks in South Cardiganshire, erratic distribution over most of the geological systems with background patterns of 20 to 50 ppm without any regular trend, background patterns of 50 to 100 ppm over Carboniferous rocks and higher background values of greater than 100 -ppm over known PbiZn mineralization. Locally lead content rises to values over 6000 ppm in known mining districts. The catchment areas with anomalous background values of lead are Conway, Glaslyn-Dwynydd, Mawddach and the heads of the Lugg. 5.3.10 Manganese (Figs. 5.19 and 5.20) Manganese background content is slightly lower in streams draining Triassic rocks of the lowlands in the Vale of Clwyd the Cheshire Plains and the Vale of Wye and Upper Usk. Back- ground values of 400 to 500 ppm are found over the eastern dissected plateaux and valley lowlands, overlapping geological boundaries. ▪ • MINEX.WALES URQUIDI - LEAD GEOCHEMICAL MAP 1/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I I I LEAD =-1.4.=== I ==-1-4-==== J3 BB 5.113 77. =IB BB 013531=== I I . <20.0 .70.1-===4. . 000 BB3B BB ++++I ,I++(===++ ++++ 3B == 680_77 f= ++++1 I + 20.0 — 29.9 0++++++++++++++ 1363B ====010000T=1C313011 4.1++++I .1+++++++++++ tijMyBEI ====BBB B .++ I = 30.0 — 1+9.9 +++++++++++++======r1Bn ==c1Bc2 OBI? _ RBB==++===I ++++++ +++++ )30009000 9P==+=== I B 50.0 — 99.9 ===3B133 f+++-P3d000 tiB8B I • 93PriBB 1++++=-3000'3B +++++===I I 100.0 - 199.9 +++=;?E 13393nBE +++++==3BBP 3E1 ++++++=+I ==== 3Bn033,j1393: +++++++==xleuefiRp ++++++++I • I 11 >200.0 +===3BBfAOP 3 ==++++++++++=+====mloo 3 +11++4Q++I +++==330r1033BBi3 +++++++++++===i0 33 + +++++ I - values in p.p.m. ==+++++++++====3BL ,1P3 +++++++ I I . • 4 ++++ Bb10003BBB ::=+++++ ====33Bi3[33E +++++1===I +-I- -1339BBRBB ++++++ 3 ++ t+++ I ++ -EIJ - -- 193B0P +..1 + +++ -- Es ++++++++++I I + +4111s3 +++++++++Et: ++.++-FT: + ___+==13Bn=._"383BBBBE3 + ++++++++++I I +++==l3BB3== BBBBBI- ++4. ++++++4, ==7 =OBBBBB ID +_=-= +++4- ==== +++++== 3 I BBBBBB +++++++++++ I BB 4- ---8-+++.,++++++++ 3 4(--:-,, I B 4 + == = ++4- s s +++++++==BB=3BB=T++ 4-+1_ I 3313++ =++++++++++++=== 3[31493c).== +++++i I 39=++ - +++++++++==B3F003==+++++ I I =13:1 +++++++++==1 000 n=++++++ I I B -- n R BBB -=++++++ =+==12.BO I =+++++= I I BBBP, O ===0 BBC ++=== m..)====+====i • I =BP30n == =OBBB ++++= 3BB3= == +++I I 30E1300 3 B----p, ++++++ 3013 J+++I I 00051DZIOSBE3==+-(3B9=+++== +a:±++ I 4550;1300f3B=+-1- ====++++= +00++++++:===l+.1..... +.4. .,1 I 0600000 3BE3==+++===+++++++ ++++++ I EIBBI:100003RB +9++1s++:++++++++++++++ ==. +4- s + I I ++=='-33003e1==4 = ++ + + ++++++++++ i- + I .I ++++=39c, DI: 293BBB==+++++++ +++++++++++++ „ „I - I +7+ ==3B3B3P,PB3BB==++++++ +++++++1E+.. +++.. .T. I +++,+ ------w---r3K --+++ ----i+++ +++++T++ T I + --+ -8 ---3=-4- +++ -- 14- + +R.++++++. I +++++===3====+.++++=++++ iiFj++++++++., i I ii +++===9B3BP=++.„++++++++++++++++Q+ == +..+ti I 29+++ ...:1-+===-3B1== ==++++++ . +c++++" .. +++ +====++++1 I ++++++ ++++ .„ ++++===&+++++++ .+ -+ ++++ ===++. • i I 4-1,'++++++++++++++++ s 0,4j, ...0===+++ 9+.. .++ +++++++=p== I I . , =++1 ++++++++++++++++++ ... +++ cf)... • ++++ =- ==Li 1 +.74-841==+T++ = ++ ++.. sf-+'*=e+7===+++ ++ 1 I +++.++++++ 4-1--- ++++--+--+++++ +++++++ =1. • I •I+++ • +1-4-++ --- -- +==.4-4 ===++++==++++++ + + +=I I ++++++. s +++++ ++++++ --++ ---T+++++++ + I I .I+++++ 4 , o 4-++ + +++ ++++++++++++===++Fs s , ++++ 1. 4. I I ++++++4-++++++++++++++++++++++++- +++++ --++. + + -1-1-+T I ++++++ ++++++++++++++++++++++1= 192- - + VIL,++++++ ++++T I +4-+ +4-++++++0+4j====l++++ 3BBB BBB=+-++++++++ -r. 14- 1- i. I •:+++ ===+++++++++1===f+++++++ 31 EFIB9 ++--++++ +: . +-F ,-i 4 I I +To +++==+q++4;:=1_-4-±++1=== ++++ ====03339 Beli13_==B3B3 =B=63333-++ I ++. 4-++==+ ++==== ;1++ ,39B3B--11933BE4-33BBBB9=P8 FIX + %___,++===I 1 T++++++(------.1++===l3B6131,119-3F3-39P5J----393RP-- -! i. + = 1 ++ ii;=B A '43=-1-+ + +--- T I ++++++I== 8 ELL) 0 LOUD 4- I +++++ Bi30 00 31=3=3BB 3 f- ± Ij. I 0136 3L=13 9B B=3BBB9 == +=+++.. +-1-+= I + - +++++== I BIC) 3 9 3B BB 13 E=9BBC L -- I I ® BB==BBB 3 I I 3BP A 69br-n ffr3gTff I I BB OBBBF3==a1SI=B3BBB T I OBBBB ===3B151BRY I BBBLI-s===3[313 I I ES-=-1B = B B I1 U. I I :11==-IB=- BBI0000 I I T. I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++T Fig. 5.17 ▪ - 1/1000000 • ONJ FTLTEPT2P46 EFfrEgAE° HiTe0FMAP1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I - 1 I . l3B-=dFE I I LEAD -7 F.3 @ti 00 Ogg I - I UftrIdEL=-11 0000 1100t)Ut:E I • <11.77 7guLidd=-T DOM 000t) 00 ==I I dEty=-+++- = 15()00 AO0E4OWS 000 I 11. fl+-- -d- 000@PEEE cilscJE4onnom EE044 1 1 ' .77 - 15.77 -===-+++-- -=LIA0O@EEWE 0000t4tJacinno QE4oGE*7-==ku I -i- 15.77 - 19.24 DEE4006dLiE oiaLadt:to40W100go400GLidr=lidui I d bEEL3Et:EbBLif 0tEdE3JdE0050000000tdo68EE I J Ed=dEgold7JEEE 00EE0 ===-i OP00004eEdEEEEE 1 I - 19.24 - 23.10 == © I LidEEEU6 0 04000'EE 006£££L=--=r0UOMOdELaddaBdEE1 add'400000P0000g sodEEudo- === 000004=-==10Jd01 I = 23.10 - 27.12 I EJEM OOM400gEttod === =-Lif0000000r=+---AgEl ==-==3 3a/:toonnoe4-0+---F--I I Es 27.32 - 31..96 BEEE44t0 00Ed400E8b0d I --=dbE000004E04g0EEdd duf,0 OB110 0 0E--t+-÷+- / I .£ 31..96 - 3909 +-=Jd3i10 otnUoaeeblEBdti dtit31,00 0 00000 0-+-=-++ 7 -I 7 A+-=JudEEL onnoatme 0 ==== Li3ui.0004000tr:d uuEI -++-=Jf4 EJBEJE0OUd00000cidd =-- agOEEE000m.EEddriuudOLEd1 I @ 39.39 - 54.28 7 */ I + I/ ++--6Gi; JO3U60/00000Edddb === JLIEEE000466BJEidddLiddOI I e 54.28 - 100.90 =:++r = t_0 313uJ040EEBEBEUFEEJbLiEEt EEdtild a - L0g000EEEY 40EEEEELEti, EEudu I m == Lib Ed0000Ego0 0d00tELiddLiEEEEDU I >100.90 --= BEJ1i00f4t-g 00*d0J4i:t;itqE dUEE8Liddis EE1 values in p.p.m. b000000EEE EEEt:00Eddibd====o8aBEE- dd=d4RI I 00400r:dafitbadEtrA=--====---6BELIdOEEEd= LJEEI I PERCENTILE CLASS, 000bEEdBbEbBUB(3g-+---===--='0'EEE gEEB3EEI 400E40Eb3bEEB-- U 000t001-= =1 I - LIMITS kEEEL000E6dO13ub = = = = gt1g0600r,o===-61 I ' 8UUJIst:40,3BOEEEEL3 ====dddBuE 000MQEdo ==== I EddEEEEEEEEEEdJd ====b0doEt 000OR DJ === T I ' @ObEEEJBEW 00E,E8d iddddUEt 40000t:bdd==36 I I ??VaNL,12 . uonnnime (JEEEE-'0EJdEd=---=11,00040jEEdd-=-I 000000M00006=tdEgE B=-++-dt:ELr.Er:LI=.7+-+I I 1106=100000u--2u4E====-++=363dLIEEy--+++I •I fl 40@0000jEL--=636-- ,d0BUJUEd----+I I • 0 00000800PEb- +-41 I • Li OnOMO0EE6 - --364== I I - ++-dE00004t0000E +-+ +- EEEdo Ot:D-m--===d3Lddudd==-=---+++ I Ift+++77 +== 00000t=-Ellte I - 9,711,7771 +-== odE0t0u-+-+== =-==EEdL)==-=+--==- - 1 /477,/,177 gI • I dUE00000E13- + + ++ dEEd=-- ++4' LJEEgELiu= =- ---+++-+++--===u336--++I I - Lig 0£==-U 9 .1 +++++ + -Jt5Ed= I I , 7 j/j=== j== L) t:Eb==- ,....2: +---+++ ---===ti =_ZJEI Er;i: EI,Bli==,/ 77 +-++ 77 ++-+--=6 -Lit0I g-+W+===jiddJuEEEdoddEEdL= EEE -WU= , ,t+++,,,,++++++- Z;I I ++-+++-(Odd3dZEEE4gEodJdu === OEE d===3JU1.131.) ===- e*77 6 •7277***,77 ++++-1- tf,ty t:i I +---,==dLit,ELEEEEEJ dE JLodEElfi -- --- 7, 17 4 77 771""77777" 1 I-E---+--++-113)=3EEdudOEd JJJjuEEL=--++===+ ++ 7,77 4 • 6 7777 ++++ 7 4 I9 --" 1 U ■-) 6dr:Li.1=---GliE=- +--1- "7717 +++,,..+-==1 - - -== JouEE,.:EEEJ tJg0J--+=---+-+ ,,,,,,++,,, .,+-=-I -= dd JEJEtEEgg 000Edo= =--==_ UE3 -==1.3 ==-4JUJ--- i 0000000E 000E.EEEE ==JEJ: I 30Ed=+-EEEb=- dBLI --== d 410000E 000tEE 4040 LEE 003,7,.,++ +=oE1AI I -+++--=idEEL +=Jzt:4ozooad000taeo 4060 EduEE4OCIEd-+ + ++- = J001E. eeeeenouiti oc,) 0 '.EEEE1:300f1()JEE=- Jul I -=-= sem NO 151E0 0000'04 LErE dbEEELiE=+ -- M000000 1:04000000 EEEEEu EE ==++ -.G. onoottee EEEEEr;t:E g14Lj =---==jj I Iwo 'Qcw0000 EEEEEEdE 00000r,0 4004y16 00000 I 40000000 EJJdE 00000 I 000004 0 0004 00 4440a I El;i-A,AU00000 I dEEOW000000 I I I 1 1+ + + + + + + + + ++ +++ ++ +++ + ++ + + + + + + + ++ + + -I ++ + + ++ + ++ + ++ + + + + ++ ++ + + + ++ + + + ++ + +4. ++ +4. + ++ I Fig. 5.18 • MINEX WI\LES - URSUlDI - f1ANGANESE. GEOCHEi'llCAL 11AP 1/1000000 OLOW-PASS FILTER SING EFFECTIVE RADIUS OF 1 CELLS + 100.0 - 199.9 - 200.0 - 399.9 = 400.0 - 799.9 800.0 - 1599.9 • "£J >6400.0 values in p.p.~. • ----- • 1/1000000 • • Fig. 5.20 96. Background values of 800 to 6000 ppm occur mostly over Lower Paleozoic rocks of North and Central Wales with a discontiniuty of the pattern over Silurian rocks in Carmarthenshire and Cardiganshire, Upper Carboniferous rocks display similar patterns. High background values of greater than 6000 ppm occur over all the mountain masses with the exception of the Black Mountains. The same patterns coincide with known mineralization of the Southern Caledonides metallogenic district. 5.3.11 Molybdenum (Figs. 5.21 and 5.22) The regional distribution of molybdenum is better outlined by the percentile map and displays very little correlation with the relief or geology. Large low background patterns (below 2 ppm, detection limit), occur on stream-sediments draining Pre-Cambrian, part of the Ordovician, Silurian, Devonian and Lower Carboniferous rocks, most of them displayed in South Wales. There is a marked concentration of high background values (up to 70 ppm), in sediments derived from the Ordovician rocks interbedded or intruded by igneous rocks. Similar values occur over the coalfields of South Wales with an E-W trend. High background concentration of molybdenum is displayed over most of the known copper mineralization. The anomalous ring around the Harlech Dome and the anomalous patterns in Snowdonia are significant as they may be related to diseminated copper mineralization. The catchment areas with high background concentration of molybdenum are: Conway, the water sheds of the Clwyd and Dee, Glaslyn Dwynyd, Mawddach and in South Wales the catchment areas draining the coalfields. ▪ • MINEX WALES URQUIDI MOLYBDENUA GEOCHEMICAL MAP 1/1000000 OLOWPASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I ++++++++++++++++++++++++++++++++ ++++++++ + + +++++++++++++++++ +4- +++ +++ ++ + +++ ++I I I I MOLYBDENUM 17 I I ...+++++ 44. +4- *00 I I 4444 44444 4.44-.4 8i++1 . . . . I I . <2.0 •• • . ++1. • • • • E.+• ++++ ++ • • • •I I ++++ • ++4- •• ..I I + 2.0 -. 3.9 +++++++++++ ++12 1.1577.. ...ITTI I 11++++++++++++ ++++ ++++++1 I 13 4.0 •- 5.9 +++++++++++++++++ +++.+++++++++ ++++++I I + ..++++-i9,3++++++++++++++.++++++++++ ++++ I I e 6.0 - 7.9 .++0o0W3++++,++++++++++++++++++++ ++++ I I 4.3334013e+++DBBB++++++.„5:++++++ ++++TI ++++ 91 I 3q:++++38I++++++++++++++...++++++ +++++i I values in p.p.m. 3r,n 393+++++++++++++++++++++..++0+++ ++++1 • I 3B 001339+++++++++++++++++++.+++++ ++ I 000T3BBB +++++++++++++++++++++ RBB0000339R3 +++++++++++++++++++++ +++ +I +3333B3RENB ++++++++++++1;+++++++++++++++I 339397?09(3+ ++4+. + +++++++++++++++I B393B90)B+ +++.,++ '+++++11++++..,I 331BP90.39+ ++++ ++++ ++++ ++...I 3D9PB++ + ++++ ++ +++. ..1 13993._+++ + +++ • ++++++++1. . +....1 313833 ++++++++++ ▪ +++++ +++++±.1 I BB- 3+++++ + • + o s ++++++++++++ I BBB93+++++ +++++++++++++++ 0 • • (+++1....1 I +++BB+++ ++++++++++++++ I +++BB++++++ +++++++++++++R I +++BB+++ ++++++++ I I ++BBB+++ ++ + • ++++++++++ I I ++4+4+4+ + ++++++++++++++ ...... 7...++++. I ..44441444 4444444444444-. 44 .0 .4 4- 4 444444.4 i 40 I 4•4+44 44- 14.44-444.444444 4-44444..]: I • ++++++++++++ 4 44+4- +4414' • ++ 81719+++.ti ..0++++++ . ++++ ++++I 1 e ++++++++++ 1++++ ++ ++++I 1 +++++++++++ +++I 1 ++++,,,,1++++ ++ ++ I 1 +++• 000'V++++ ++ + + O• I I ++4'4 ,„+++0B++ •• .6 +44+ +++++ 4+ ...I :I +++++ • +++++++++ +++ ++++ I 6..4.4+ 4+ BBBBB91+ ++0++++::i I OS BBBB3T+ O 041 -F++++ ..]: I SOO BBBBB++ O 09 +++4+4+ 4* +++P++++ O 400 +++ +++I I 44 44404+ I +++++r— ... 4.4-4-1:1100 +1 I ++-1:f I I 04 ++ I 401141 0 + r+ + +-J. 4+ • . CI , I +.4...+++++ 0000+++++ I ...++.1-f. ++++++....+++++ • I +++.... ++++373++... ++++r ++ I„+++++++++,.+++++:1A++ a +++++ I +++++++..++++++++++ ++++++ I ++++++,.++++++++++ju n. +++++++ I ++++0000 + +++ +++++++ +++++ + ++++++++++++ I .++++++ ++++++++++., ++++++ BBB ++++++++ ++4 I +++++ .+++ ++++++. +++++++ B9B+++++++++ ++44 •F ••• I :,]+++45- +++++.+++++++++0e0 ++++++++8 +++ 4- ••• .. I f++ ++++++45—e+TBRR 0c1+++ +++.2,4-41- -41- + I +++ .4- BBB++3BlaB3136Fq +++++++++++1J- I B++ 33 OBB+B +++++++++++ I +TB ++ +++B +++++++++ I ++ B B+++ +4- B++g+++++++ .4- I ++B +++++++++.+++++++,...... r±4.• I ++++++++T+++++++++++ .+03, I ++1; I++++++ I —1++++ I I I I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I Fig. 5.21 • MINEX WALES - URQUIDI - MOLYBDENUM GEOCHEMICAL MAP 1/1000000 OLOW-PASS FILTER JSING EFFECTIVE RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I I BEF I / MOLYBDENUM =-BEgOJE I ====EEElk LEE 651E --- I I 5.3.12 Nickel (Figs. 5.23 and 5.24) Nickel shows low background concentrations (less than 20 ppm) in sediments of the coastal plateaux, and valleys of the lowlands that are not influenced by drift of the local Welsh ice. Nickel is present with higher background • concentrations in the mountainous areas with the exception of the Black Mountains. Nickel is present in somewhat higher background concentrations in streams associated with Lower Paleozoic rocks (greater than 30 ppm) than with streams draining Upper Paleozoic and younger rocks(less than 30 ppm). Ordovician sediments show a higher background concentration when they are interbedded or intruded by igneous rocks. Within Devonian rocks there is a difference between Lower (30 to 40 ppm) and Upper (less than 30 ppm) Devonian. Patterns of high background concentration of nickel are also displayed by sediments of the Upper Carboniferous in South Wales, with some higher values in sediments carried by the river Tawe. I A high background concentration pattern appears over Ordovician-Silurian rocks on the Mynydd Epunt, this area is covered by a series of basic intrusive and extrusive igneous rocks. 5.3.13 Tin (Figs. 5.25 and 5.26) Tin does not display any obvious distribution patterns, being below detection limit in most of the samples. The interesting feature of tin is the concentration of higher background values (greater than 6 ppm), in the whole 0 of North Wales in contrast with the low concentration patterns in most of South Wales. '1 I NE X HAL E S - UR QUID I - NI eKE L GE 0 C HEM I CAL f1 AP 1/1000000 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS NICKEL • (1.0 + 10.0 - 19.9 20.0 - 29.9 = 30.0 - 39.9 '8 40.0 - 49.9 e 50.0 - 59.9 e ,60.0 - 99.9 D >100.0 values in p.p.m. • Fig. 5.23 1/1000U00 ot5J1.:0An'FYLTd RELV; EFEW,Luk,MYEI8PL PCELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 I I 1 +Lir-- I I NICKEL +- EW 9,, I I ----==-4- ++.4.1. £u£1-119, I I • <15.08 --====-+, OE I I --,„ + /SW', 3 =+1,1+:7: -::::=--+ I I . 15:08 - 22.95 0161-++ ---+ 1,,,, E0EaZEW&"61,1"1 -- +++++ I I ' . +,+---+++++, -3BEOODEOtig0000-++ --- -++++919.9,1F41 I + 22.95 .' 280.8 ,0--=--++„-=JoBJLIEW0000000=+++ --++=--++99991+++I I 1 ++---+,,,--=-Of4 0000000E=+ +---+-=-+ ,,,,,.++ I I .. 280.8 - 32.79 +++,„,--Jtho c3 d0000003 =--+ --+ „,++++ 1 I 99 91-++---LIEWWwWw0ggWg0gLEL - + 7+++,, +++ 91 I = 32.79 - 36.99 ,,,j----1--.LJEGoGouaGEEt -41X1Au=+-+++++,++- „ ,1 I P-iElfai==BEt4th4WWWEJOUEEEEJb==++11++-++-++ 1111 ,' 1 u 36.99 - 40.68 ----oE0EOOELo004tgEO OtiEiEdo=--T+-(34=-+,.. 9 ,9 9I • I --.17,==E.g45OLEJUO-L'WOEB36dOEEEBIBELJu---===-,,..,,, I I £ 4o.68 - 44.76 +-=O[aziOE01107E Wat —EaBbEEEEEE =4- 1 , 1 ./ ' +++-=LibuEEEu4OODO-udbEEOEEEB . 4EEEE-Q=-+9 ,19 ,1 1-I I @ 44.76 - 49.94 1 , ,?-1.;+-113F,E0-=1A0000==lEt:4G- 1:Edz: -4 F ' .E0-====-1-, , , 1 7ff"- I I 199,9fl +--=LiJO-+=E30.-JEO==-1E0W4wEEL 000,E13==-++9999999999I I e 1+9.94 - 58.68 +, , , 7 , I _Vit3EbE4=7.3==lEdWEEEEEWOTE6--+++„..,,,,..i I -1- td+++1,, =ts BOEBOBFWWwTE'4wou4 ELJ-++++ +„„,...I I 1 >58.68 ++T+++1, +-L7t, JdBuGEGe EE 4404t0=-@+++-+ 99999++I I s=, -GLi- Ou E.POGEEEEEELI =--t t ,11, -=1 I i-alues in p.pon. • th33,36EBW E=WE3OBO - f 'I"' I tgIFE6JudEOGLEELA ----=cF,117,-+-1---+ Mt/ I PERCENTILE CLASS UWEE6EC00000Edd ----LsEgu=--==- 999.I I GtEdEEEg000E0 OdEa0E=----++91,•1 I LIMITS tEELIBEE1 8400EEdio=uJouudE440WE==-+919999I I EEEdbEEEEcJWOOOGEE,,=JEEEEE,; =- ''.-=-+ I EE3dE'44GEW000W4uF=3bEgG0g;.'- Lti,o0= — + ""1 f I BoEEEWOOEZ 0000W0 JEEg4Ogth4 -udu=- ,+---+ I I DOOEEd05ZE W000000::;E4WOW00w6EOL5=+ ++---++I • I OdEE00E13 0-111:00o0B0000006=-+++===++I I EdJoEOWE gOW04000440000 000WEL= ++ I I OWEEEEJo WOOOd!dn!0-00 ;0:4 W0000Eo--++-===I I - EEEEUBOLIBEW00000WOWOWNW ta&WWWEd ---=-=-i I bETRKOODOEW000000000'bOnOWOW)WE0=+--====-I I BBEWUEEEEE000WW0000050000000WEE==+--==-- I I LibEACJAEOW0W000004-3:3000WWWEE6ddo I I ==JuitGJEEE4W00WW4044.144WWLEo do3p=--=---I I =JEEEEEc;OWT,000:40EE'4Wk4W WEEt 1±:Er1 +I --++-=OEELIEFa-EEE0gWE030JdutEEEEMEd4=AA=- +++1 I - uEEEEEJWEEEWOWJL----7405JEtbu=---=-+ +++I I ----===douEEEEEo4t3b300 u uEtouou=-+-= =-++= I I --+--==uUEEEUUEEgOAE3ou,OM;EWduuEEWEu=-=--+-= =-= 'CI I +--=----==s0EEEEttouE,DbulaWCTIO0OwEioJEBu=-===--dEEELJJuti I , ++--=----==36JOJubOJESEEEu8WEWUnnMr1;:wEbd6==-====--=0EEUE:3dI I + + -===uuq===iddubbEEEEEOL3s-bOnnrnr2OE uot3=--==uOliu 1 I „ ,,j+++- --==oEbd1===3EEEOEL4WALO=-EWIIM1006t)== z= oBti==-===JOIELJEI I 1 ,1T-=---++----==uoodu3JOEEEEE tOWEEu=-EWCODCKt== --===o==-====ouuoI I =+ 99 t udtiEudE Etd0OWEBB--0,-500.7-ju-- =d== -d =.7.1 I --=-+ +-==i3E.EA736E33=3ELEid.OEt 40fat3===--,L)AWOEt: +++ --o- =I • I ++-==- +--==EOGEOOEE,;EEdo3bELE aGdOgLO - ttqliT =-++,:::+4::::!T++ + III++-d =++-==OzOGEE GE,i130=B3uL,WWEJL3=-+=LiOb=3E0407==-+ I ==-+--== 31:100Gwt.ELs==-=3EEEELiu==-++ UOO=JE0Wqr: = 9 ,,... ,-MM=- 1 ++---,====oEEELIO4EEL =+-iEEEEOO==--- EEE====lEtiJ-- 99 . .. -===-- ,„I I ++-====--=duEJ0J,E):Eb=-+-=E.5GwIEEL177 EIGL=---===--+---+I:::.;--==- ++-'I I - --d3O131-- -,-lOcid- --uECA000oE IgnO --- __-+ , +--++-==. 1 I +--=-=----=uEEEE=--== ===-==ufenB000 nOrigEuo==-3-Mullil =+...99++ +== I I + ++++=bEEEE -==o3OptJ000040[100WEEEEEEo = -+,, , ,,•,+-4-1 I +++--+++-bEE +--LEE-040000000WEE'wwErIgEEEur= + -+•9...9+-1 I +++ -- zjI4 -4gd000940 EI:401:L,Li_g=-+-==-=++ ,....,;I I 7,10 BO i410i3ti000i,Jot:E== 1 ++=-13=- 'g m., I I ++-Db.EU W 0000WE=EEE-+ 9999+-=-+ I I ,I+--==lur=" EE W0wWtis=JoE=- 9.99-++++99-. I I ++- EIBBEEEE0-==0==++„ -=+---+, I I 131=- - ++ 9 + -5 -==P= I I -- ,I tttY1Fi I I TTTTM- ,,,,,-=u 1 1 •• • • 1111111 1 I 1111 I I • •111•• 1111 I I I I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 Fig. 5.24 102. Background values of greater than 10 ppm occur over Triassic rocks in the north-east boundary of Wales. Higher concentrations of above 25 ppm occur over Pre-Cambrian, Cambrian and Ordovician rocks. In South Wales a high background pattern occurs over the western flank of the coalfields spreading into Lower Paleozoic rocks, its direction suggestsa similar airborne contamination as mentioned before around the industrial complex of Swansea Bay. According to Hill and Parker (1970) quoting Parker (pers. comm.), high tin values found in detrital minerals along Swansea bay, come from small fragments of tin metal, commonly in thin slivers which have been rolled into cylindrical shapes, coming from tin-smelting works along the Tawe, transported by the prevailing winds and deposited on the shores. 5.3.14 Titanium (Figs. 5.27 and 5.28) Titanium displays a better contrast in the percentile map, with a large percentage of the data in the 4000 - 5000 ppm range. Titanium background patterns neither follow the topography nor the soil formations. The north-eastern boundary of Wales is covered by a large low background pattern (less than 3700 ppm), most of it on Carboniferous and Triassic rocks. Slightly higher background patterns (3700 to 4600 ppm), are found in Devonian and younger rocks. Cambrian rocks display a similar distribution pattern. 1/10000 G0 TIN ' , ++ • <5.0 • • • r,+++, , , t 5.0 9.9 , , , + 10.0 14.9 15.0 19.9 = 20.0 24.9 13. 25.0 29.9 £ 30.0 39.9 40.0 49.9 50.0 99.9 )100.0 I values in p.p.m. I , I , , , , ·. • G • 9 • 1 • • 1 • • 1 • • • • • • • • • • • • • • • 1 • • 0 • • • • • • • to 0 * .01 II • • • I ·•••• · · · ·00 · ·•• · ·c ..••••••••••••• · · · '0' · · · · · · o ••• 1 • • • • .. • • • • • • • • • • • • .. • • • • • • • • 1 ••••••••••••••••••••• eo •• I ••••• G •••• " ••••••••••••••• 1 • • • • • • • • I: 1 • • I Q • J. • • • 1 • • 1 •••• • • • • ••••• ----..... ·c ...... •••••••••••• eo ••••• . • • • • • c • .. • • 0 • • e , 1 • • • • • , , 1 o •• II ••• , ~ ,(II • ••••• ,[;], I •• e ,++, I • ••• ,-1-+,,1 • , 01 •••••••• 1 .... • I • • • I • • • •• 1 • I •• I • I I • I •••••• 1 •r;-;-;,. i .. • .fHJ- I I .L • • e • • • • • • • 1 • • • • • • • 0 • • • 1 • • • • • • • • • • • I 1 Fig. 5.25 MIN E X Hi\ L E S - U R U UI 0 I - f II~ G E uC HL t1 I GAL 11 AP 1/ 1 (J 0 lJ ij u 0 OLOII-PA~::> F!LrEf~ u~l['JG lFFEGrlVE RAlJIU~ OF 1 CELLS TIN cennon u €J0nORrjD !:;H~~060CO(] • C' + (2.32 2.32 - 4.29 , .. - 4.29 - 6.08 .£ 6.08 - 7.91 B 7.91 - 10.09 e 10.09 - 14.34 .0 14.34 - 29.31 n >29.31 values in p.p.m. PERCENTILE CLASS LIHITS 1 1 1 1 1 I 1 1 I 1 Fig. 5.26 1/1001)000 ll'OrU4AnLHLTEPHih6 EFilffl yeaffgEUFAL1 IlffLLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++I I 1 I Utiihk1.1 I I TITANIUM 6831313063 ======I I J 3Libt3J ======bl 1 . =1 _ _ I . <700.0 613o313,31.31- ======E1 I ' 13136036415UBL L %-- B -7-S3 LF. ====i I + 700.0 - 1499.9 =, 0 Jg==1,,- meiii-01Jula J - Lio6138 3===EI I = _00 ti 000ME.3b0U0dUo - - -3L3o331.33ou::gib I - 1500.0 - 2999.9 OW3030'000'3, 00trrne33bOub&JO3b==== -----====u == Li I Bdu500000000000 06bobc3uuLidd, _ == I I = 5000.0 - 3999.9 0EgitOW• wJapou•- B31301313613 JuJJb=== rill === I I 83133u 000000 , LIBUboUu OOJJob - I-I _A. I a 4000.0 - 4999.9 OJIJOL,00_3000 I 00oL339300 JobbObbOd , - 000 LJJ ===- _ --I I 0 5000.0 - 6999.9 00).3O130000000 u3L,313oJ 0000Dbob - • I 000J0J0300010OUJBBOL 00000000JuJOOO - I I 0 >7000.0 3R60 3313 .3 30 03 61, 0000000'ibt3013 oo ___II - I • 131600003JouuJ 0 ouu L36 00 0003ouLidd 30 I values in p.p.m. 1-b-1.1-=c3u00000o3dt300jo Jii ouo 0 3obuot30o ===30 I I -----6b000000==oJjudJ60 diSuocido JuLibdou ==EI I abBoBud 3133J- BLIBB3133663J130B ====I B3dOlidod 12--=-1313361 Ob00663d0J3Lido uu " I LiBLA0000 ob3' 0ocidob3U LiJuu 0,3 13 - = 1313 000 BUBL3133133,3.315J0 13 JI Li • 3 ouOrtiq-00JutTqL33ButidOBUB =;.=.1313b is UI I ea'd ea100id13613336J313063WOOD -.1===0,1 me, 500000360o3d0o3UudOodubduu .00 au 00000fOU6133130duLid1=== -1 dOdOUU J O S Of3u a 10 9 Oduddo J33L33L3Bduo133613 331 13 L., 03JodbL3Lidouoti 3 I I ' Ud3r0 '3obi3600J UJ3bLidt3buL:0003Ju I I 38031) 0 ,00 +20 5633131-30o630i366BUdOpAtit3O -=4-3 I I BUdLO 000 C3oU13333J3o6Bdo000:1R1!300.3JOOOL3I - • I 013u 03 00 0000631333631053"0000300u613JBUI I BO' oddo' 000dubBOJou10.0aodu009000t3d6uouI I udJUIJUJJ1.3U 0 JUddou0000(036ouoo J0ouJdoLsdI I B3330000313 dLUi3Ut;y 000(0033Jubd,0_1003oLiouu,i1 I 613131)00pgB331333363u0000:)013130J3O0000ubbarithI I dbadl_3 03uibLibdaubooa0W300JOudLOoJuoodo00 I I 8B31)1i0030=0363oUd3buOJudoOduuuthiddubo u30 1 I 3libB.306.03u,_=.1UBBE3030B413.03130360oL3B13363B6o0Juool I 13d13BUB3L23 L3db6333(1000J6633136136333,360uLa3ut3131 I 631j===lgJouo Jeu0-gu(300_.tpuoLibuuobbouoduc301 I B83136 -1J--2,33bLiLW0(303,0000Vii3313OuddOJoJobig361===I I ' 13303___1 33BL3000Obily000ddul3U663133036L313 I I 00000uJOJ03L J3bOr,0o0363,3 30000buodbOuJuoudLo0101 I B13"0000000 OJJ4,===06Ju33d‘Ou03363uou 0MuooL3JJu0000daJogI I RWBLIBb000000000o3oC.------66333100003 33i3L3 313613336Fau000 JoI I 61.36c313100J000001333ddUbaJt43000000 11,3' JJdUBUOUIDOBUOJIDO6 Esd I I 33 100 J00000000 00ouuJo00000000 ou udOUudciuo3dOodu oul _ I IJOBj0117000000600000tOSOOD00013u000000tOu JUL. JOOLiddiJod_ioddLiddodI 1 asEaitnulnlameabootaaaaaaaJ,Dao-aaauo, 13,30uOdbOoljodoU3136t3dB3u4I I BBUO36347,1"7170=135000000ua0b0000000000000S1 333L ouud0Oodudodooj0I • I OJOBB3JoD-J7r7Inflr-jJ00050007,0D00000000000001301Judu Juut33oLidbduOuo0 I ILWOdO3_3303100.3n0500000.80iu05000:000000060Fuu0Jouu 3 ouoLidobduouLiOu0 I I 333ouu10030::11000010000000;3J300000000010bLibuti000du Jo6U30130ouoddu3aI I D3366,3J0000000006ij0000313-03000pullalo bOuouda0efraTRo uddLioJu000louI I Lism00000aaoaaeof c fi0i.L,,:L..JubOa Juu.3 0JoOdou0000t0 uthibuouulEJJoodul I 0000000030000000'0 6,00003.33JJu0oJuuD Odboodbioddid o ',idoduudddoE I I clapaaa0000paaawa Bu 'o 00333Uu033U0 JE3c31:7-111jJob ou 00 Jouudob0o= 1 I 000000000 30 000 d 0 tiBUJJL3830BUL3bdul _ U3BOU JL3 000000 ri3uLiBoJUI I =IJi0000iUuuo - 000 JoUL33,31.3uLidbu0133JJJibuJoo - 000003r JuJoduul I 3d300Jaid0 == d dLiddurbiddoOLIdi JududOdd 00000 Lizio,L13oddI I b.Ot)60 === 313 ==bObbuoJJuL JUdd,4==_, 00000 JJtAll == I I OddRibis =---=7 0t3t336t3- 3uddlg 00300c3,30or-7- - I I douodboli ===d6dou ===.3t3Ouauo,LJOJud000 I I doff ===o0uJu====iooduuog0JdoJbou I I 7-1==2gUAL-3 - buti 0 ald,360 I I I I Fl I I -7+ +1, I I +++ i I ++ 1 1 I I I I++++++++++++++++++++++++++++++++++++++++++++++++++++++f+++++++++++tt+tftfttI • Fig. 5.27 MINE X WALLS - URQUIO I - I II ANIUM GL ()CHEMICAL MAP 1/100UOUU OLO,i- PASS FILTER USING Li' r EU Ti Vt. RADIUS OF 1 CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I TITANIUM ++ +++ I 1 ===-...--.-i 7 ++4•+++ I • 9 <3700 711/ +-++ +1; I f• 7 • +•- + 3700 - 4096 _+ I d-- g • y y • • • • ==-"-"' .."-1771 - 4.3g047- Egt guork;=-= 7•/ +--==..-+===+1, I - 4096 - 4387 = . 2 1-7;2=AE=M[1:: = -+ +4 7•••71 7 +-+ , +=-+ I = 4387 - 4652 EEEEEEE Ogggr5 t-+ 77••17 +I--; ++- 1- I 1+896 iitJUOEF 00. ibo 7•77, • fl f• ++ 797 u 4652 - EEEEb 7 1•• 7 /1 +,„,++,,, dtiAlenaga _- 7 •• 77 7 111-++,1*.1 • E 4896 - 5170 EEE_WOE00040W ==L EKEL4g4,6. EL = - - 7•7 =+ • E ,3 't)Wgr - =CgOUg4gdg ;BO ft/ ::::::::" • 5170 - 5494 I -- }-.,g0Oggggt4iu =-+ 77/ 777 •• • =---=LJEEagaEL)', =- 771• 7 7 I o 51+94 - 6o68 E6o---=odEE,0 ELAM = 57 =ucie,t, EboduJ=- p+/- ,••• a >6068 1ir7.1.. + EbEbddEL 51 t••• •++ 3 -1(....- -.-..==-== EEEbOdEJ .1 values in p.p.m. 1717717 ••1 -++ .I.-1-=LwollA4==-=-= OEE 3bUOO 755171111 is -+ ++-+-1 PERCENTILE CLASS LIMITS Ls t:I.E;4000600- + + + -3--++--+T+++2 D EttJ0000L.3 ---==--==----+ -=0= -++ ---, + ++ I OE.EEEgggt)EEEIril3 EJLEEcEEBBL E3OUEE EoLib Lib ===jbljoc ===----=j6,1 --+++ +- I b JbEi33638t3t.:,== 3,133bi3=--=uk:40_,=---+ B =ob£i;EE£ o.iJobo == = • I === EEL==odt.SJOBLioLiotgOOrlf?Jet;L: ===- === EblinoE" @t; E Ei-JOLid.$ r4_,,-===- I --= Erio=JE Ejgg EoottI,E ,-.:Ez:utiou6E/JOE ------== OL,f,o_ioBEELEEEEoiEggUEoff,. ==-'LB[- ot1- -++ - 1 I bu .:,EREEEEEf.EEoci6E,ggEtio == -=000EgE..) ----=Jol tiboi:Elt:Ei3EEE6O0EEEiggEEOLi === L3oBEL,' Er_===looE I EbULtEEEE6B LW' JoE4 Z9LLIOL)==Thiu4=1-- „,i6Zi. I Ls- l itEli EE Liu 36EliEEL; =-===-====-=Je.fAZ I I o= - LEE ibt;:-..:z.'1.t_ =--===-==-':;-)f,t3EDE 1 =--=Lit3E6 1..3.£titili );:e.±;Li - - 6 L.) Etibf==.1 I =-++++---==t3EEEOEjEEEE,Eilgo=--- ,, E.,,j) = - - - BOO= -+++++++++-=Lb LiEEEEEEEEc.EE,_, I ....$1:.-+++ ---z=o,-.---+ - 1 131361.36=-+++++++++-===Eii:EEL3E(yggg12-:c3 === z ,-.., I 47A,:.4,-,ELI],=--+++++++- -,EEEffEo o,ggg ( gi,:==== .ioo -+ - =16) ==1.:-044vP4U4 i.-=---++1:a+---====k,i,Ef.t.L.J=-= ,J,L.t.1 ====,..3...) Jouz-=--=p J I 0B1=== bEgw0000@t. , --- +++ -tooi.)Ez•eiggEE =- ++ -= Bi,E -.p-= I -+ +-=L,EELL;==0,1,j;L(:',1:$L2,---+---":j t3f oi g'-3000;4E ,,,..____===--==EEEI:g0Ogg lit. tiEtiJubc:tii;I IJ'1400goEI:r:EEBLI6t,utI44060 -=1:.r: ?tp.7,.2f- =-7= 40,-1g04g61:-,filZ.0,=i0;3t1461000(51EziLlz:1044*00[20 -EL:- f::::Iciii- ) • I -i= -Joonnnrn7Joaut)wggolgggd000bT.l00000ec • I • of,o--r--+= a OrICIC717:"J;r1flar3 0 90 E Ef.,7:0,3000;J'4460d406%-, -+++++-==j l --+ -+++ n u 0 LP:I zif:Et3 =-= DOJOET.;000000006:Eu.Ji0000000dgdgit ==--+++++f ,I Of ILA= LIdi.3 iOCiidti0ggug±:;:tiiagOntgeggg;r 4 ili ------+R -- ++ -5"3t_i r1 1 a== 3UUri OziLltioElOtit300.7>F,1;Ift.14404zidtgE.J.- ,,L.t,L,L:Lit)Li t)0,10 .0,3L-q+ --- ++ -outtit,1 - I ilii:or:tgoon-m360-90atioggt:L.L.:).14gour:._;t3E.ei. bub =3/..noorkE- ++4 - - -,- I- -'Eli 6 J. I ;.-1 ..;E, 4 g00110E1C90 ,44tt-W4r-4 1.EOci iElit.140u== Oa Ed -+= 4490;--F-+++++ - @ Er]; Egg900Di7C500g[EE::10gEE,, ,A===)uELL z--LE Eu, =-+- Eoio_f=- +++ + - o3oo6oto===- - OggErggggiggUO0OUGLoo LEEEoi6J -,7 otio db.= -+++= -= - - -++EI- 7--- L, EEEEE::E6o -1)00gg gr.:EE-40at30 dELso_w =--==0E ==+++ =- ooE 4E2,4g LI,Jo I = = I =11.1-:J guE i i t.: L r.: ===i1i3ii) + a a I i:.L.AP JEcii:i ++ =++ - - - - + --- ___ --= f. ggg EEEEE• = =. I F.,404e. +++ -= + -... - - -= - -+ - .000GELJL:..3 E +12 I +4 -===+ =,:goggLE= = - I. I -=-====- + ++++-==-+ -+ O60 77? --++++++—“•-= 3ti I +--++++++ -=-101, +-41.1ELI .1 1 1 + -- I • • • 7 7 7 7 l• • 1 I I 1 1+++++++++++++++++++++1+++++++++++++++++++++++++++++++++++++++++++4+++++++++j • Fig. 5.28 107. A higher concentration of background values (up to 5000 ppm) is shown on Ordovician and Silurian sediments.' A marked contrast of high background values (greater than 7000 ppm) occur over Ordovician sediments interbedded or intruded by basic and acid igneous rocks. High background values of titanium coincide with areas of known mineralization, but this may not reflect the mineralization, but the geochemistry of the rocks in which these are found (Southern Caledonides rocks). The catchment areas with high background content of titanium are: Conway, the heads of the Clwyd, Glaslyn Dwynyd, Mawddach, Dovey, the heads of the Wye, the Tywi and the Teifi, Cleddau and the heads of theTawe and Taff. 5.3.13 Vanadium (Figs. 5.29 and 5.30) Vanadium is an element that does not show any distribution in relation to variations in relation to variations in relief. Regional patterns show high contrast coinciding mainly with lithological units. Vanadium shows a similar distribution to gallium, iron and cobalt and to a certain extent to manganese, nickel and titanium. The contrast displayed by the percentile map is slightly better than the one displayed by the selected class limits. Patte'rns of low background concentration (less than 60 ppm), occur over Cambrian, Devonian, Carboniferous and younger strata. Vanadium outlines the Lower Paleozoic rocks very well, with high values ranging from 60 to 130 ppm. Higher background values of greater than 130 ppm are concentrated over the Cadair Idris mass. • onffihnLPILTLWThg EFWAUm abhgLWAL im8ELLs i/1001.101:1U I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 VANADIUM I Hi-LOdE±:JD■ -1= ++L, I . <15.0 Lijr:k: Eijd c.3 I - Lit.listiod==- --== -=== 1 '+ 15.0 - 29.9 Attld Lid = = - =1 -r 4.3 ++++ ' == - 44.9 -===t3tilitit3 ,...i3ls== E. u a-3 wi:E EEE Et, +++++ II - 0.0 -=,..L3t3t38Li.idt3L= :=L) 40Et:EiiEEEEEE:: ===.1 I = 45.0 - 59.9 =z-jt.it Er:lb....Ado r.: el 40 E40 000tiE Jr: I Lidlse.E.1.;EolluDit-_,i, 40r,_00000p,t;i- +++--+ 13 60.0 - 74.9 Etiiidb tur.E0 4t2'04004EEdiu- I i.s ,.f 3 b e, E u i. 0 4 E E E r: t-.; ::: E i:is:. LE). - ++f I £ 75.0 - 89.9 ==. L-E ,E 0t= EEtiobJ6sEEED- -++ I AlsouE0000z.EEL LEEduotioZEL,..y I e 90.0 - 109.9 briuubt:Gto4okgr,LL:ELEEJutibe,LJ...ibiii==- I EibLit.iiiii-;l1-:. .40J0040EEEEEEEi.EEE330101.)is I 0 110.0 - 129.9 =3bLi.iutiEt:1,4.7. 4E,Et:Ei.144::E,LLio_iibuo I . - =3uto,Ei:EuEt40040E.F.3jEEEEEEE- Jbduts I i >130.0 +++J-==jor:LA:1)Lis==JALgo4EL,=bEEZEed,4E1..t_Idat..) I -di.sOutjuf====*EEEe.i. ==bEEEEEE.6.J0GLEE I ' =74----g 3=LiJuutili--.:f.t.,,L;EF.EEE.EE04G7)Ei.x: 1 values in p.p.m. --LidutiLilf,4::DJEE1ELEEE0400EEELI I 17:4==11511)== -----t3ts-4,:, '140E.r.:EEEE,E,400tr: 'E.D' - I :=1-y--tjit.:Els#: .IEL,00EZEZi:;ti-dtsu==- I olE.E '-:3.C.TICIP,40)r:EEELL3LiLit3130==== I ' E1000fAt'finCid4LEf:...3631.3,3b3===1.3.., I 040[]AOrflii:b4E..3th33(.3L3c3Lit3.- - L.5u I OS40 '000.00LY.54E.RicidJUJbLithitiu I 40 (330000f)Jt:..ith3E3t.33313t3tiLit3tJuLix.: J==== I 0040000000(k-z Ef..r:f.r.,116.i_ibt3L3Lit3i.niEr: d,==== I 00000000000.00000t:t:13bar:t;t3E3i3LE,i3uttLi== I 0000030000 040000e.7../!...i.:EEd Eibe.f.i.2.:aibLi I 40t30000 Ot100000401::EE.x.: 'Lir.:k.A404Gr.:Lot,==. • I 0000013044 000g00400PiEEEELEEf000,0120i.E36==E I 00400 400 000000004EC6iult;ELi000045 - - - - I 0000000001300000000z.)-;t:E t3013thst:000L5------I 000000-000L9000000404L'i;Et; 361.331.; e..t:Li- I 00000000V1300€144gr.r: 668133da- I 00003000005:000000000E 3U,3c3U iBB I 1:,000 000r;t:E400i:r.400r;: I E1,1504G40't:EE400t:Et:1400E.i. .1 L3t3)::/: 4tit.::--9 0F,000EEEEr.;..z.EL■initi I L3i=L.A.r.,r;EEt;d400000r:Et...t:2;t..300L.s '-u I LiEt-Its3LiEk:t:E.,1t.3t30:-.00000t:Bi3z:EE.LithitiLibLi I ,==13 'e,Ei.:thit_itiLiciutiboE40 00F.EEr:EEE:f.i-Jdu = = I EJV--= LEELLS11.3,.A.50 t:Et:EtgGEE):Et:i.I.:1JutiLl Ur...L. = =Id I =Liao JLJUe. tr:Ju.00duEt404E0000Ego.Joibobu = = = DEEEbyT; I 6===1.3ELEL-toZLEEJj_JutipoLE0d0E04040EuF=1, ..s..so,si.s01.: I figu =Litiz_1:4a0i.i.t:LiLit:t, slit r:)_:404004001. F1- 6 Lk.: i.: I == el==.73oult,t40000tEt.tht.t.r.t.- 044000t.i..tit.; ibbudooll.:E I ===A_Jitt:3;_30,-.f.,Ec400000i440400t;k:t:;:i0 401,!.t:C 1.1d3uti I t0 0E3404400 EE - DO 0 r:Lii: I i3 Lk_ 644)00000€10000U404000400000r t7!r Sod • I fit3t361====JcLI 0110aL()000-00at)000400400F54 I 6 333.tti40g40000W3U_t)400'0-Ailif300 I =0302:)ri:k::1;444 400u0(4 - Lir,:4)001 I =3)::LEe.E ,''i:gi,i.:fgi-440 .7- dJ;j 1:r,tI Li- - I =.:StEk.r.) _Idr:r;Z:toiLl oL3== JJdUc===faaa 1 ==33t.E3D3jjJbuJOUJ6JdO3 = = = ..LidtJuJoUd 1 -===d6E3LHUBLibC561361)F1-1 ==== 1.3 LibV: LK= =[3b==Litiuu === EL)u---===bUuJ u= I -===.3666di3ti6OUd .6 0 .3L3 --JL z.L3 Q 3,2Ati I =1s1 ttoouga BbLitidt.ibb0 6b6o 1 I I 11= I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++ttfttt+t+fiThtfit Fig. 5.29 • MINE X WALES - URCIUIDI - uANALI1U(1 GEM-U.11(3AL MAP 1/1.6013u60 • OLUA -PASS FILTER USING LH- ECTIVE NAUIUS OF I. CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I Bi3i3L3LIU VANADIUM +- ' L.) u i.: £ E .3j= ++ 0,, I i.; LiL3Liwo = i- ++-- I . <26.7 LSBEL3L3L.3=+1 -++ +--- • • 6 , ===u I • -711=U==_7._=f--ijr_i- -4"7,1f++.1, -++ • • I 7 CI 0175.k, E E = ,• •It] •I • 26.7 - 39.0 . ++--- 888 ul====-1- + 77 711717 ++11/J+ I $ + -=LibLiJJELit --- -L).E003E+2.414c4gdwz. ,,,,,,,, +++F++, Ittlttl 1, ..I++++++ I + 39.0 - 48.7 -..- L.W2E,L;Edu -,=0E0Dgi4Ed04t)owE = 177 W W 1) I = BUT:: 1;;;?:-36,SEUlabi.,00013.t 000001.3 -4- ? 7 777/7 + + + •1 79 ) 1 I •-• 48.7 - 57.2 ft.ij==JJL313i3E1.,40=0E 1-44 140 Ei3 =- +-++ , , , , , , , „ , • I . === JULEtUbL4EGLEEEELJbEu-4-1-- +++,,,,f+,,, ',.,. -=:::=,Eff0VOL3L3f =r.:LibEELi±d1.113o...:E =-0+, 7 91 tttf 771 I . = 57.2 - 63.4 I ' -==UEGOOLIELsECL, 1.)EZ. ==-- .9, ++,,,,:::: j I 13 65.4 - 74.6 ====d1;4300 47,-40 0;r4LEEI:13.13.-3:_,,IEEz:E it == -1- 777--"77•419777 • I ----- DEO;;;OUEJUdEEfgr:4e.EEEe.E31,...id' = +, ++ 4- ,,,..,,, I .E 74.6 - 83.7 --bEt.L-,6EgE 4000040EE):,44;;it;L;1E,P....3isbLidt3=+ =-- , 1 - I . + --=LIEL.).DEEELJEt..)}.)040i=)E,=,..E0EEe.E_JEJLiuu - , i+3 I - (31 83.7 - 94.9 ,,.1--=UE0E4===ob4#)00 == '04gEi.:EEEbbd - 1"7177,÷ 1 I - +1,193 -11- 603i3EU=-=.3EEE4Rr.0 -1JEEEEI:ZE C.1 1 44EED --+ 77,410 •777713 I ® 94.9 - 111.2 -f+t+4 1- + -----7113r..)b13C, =E0t-lEEEE4EjtJ04i= E= ,,...,,,..) I ++ ofAtJr:Z.r..E4J0d0t;t0* - 9 7 ,,,.,,,..,20 I 2 >111.2 --===++----4_,11f3g(4ttJeEEE44EEtT.0- u1- 9 7,777711-1 I ' ++- bElocnn 000wEEt.:4*.:E06 = -+- r+-++,,,,L+ I • -=EE4gOnnMn000t;r:060EiL===- ==== --ii4T-19,0--) 1 tpuoporPnnoouLitA3Lwoub===-=13Ei:=-++--+,,,,a I values in p.p.m. aomErnmNnoot:Lso3obbis,===-=Doalu-F+===v1",) CM00611Er.f:7PETOO ta5Liitit_iuu 0E'_-++-_-++-+2 I PERCMILE CLASS I go4ocinnnr-innoo EED8883 3L-5.:1.>====8Ei.=---- f-+ ++; 1 LIMITS IntP3Or( ;77;:r11100 141.:t:E03%.30136 ==== 3ELLi =--++ + 3 I (30IJi)0111.M3r1000;-.o';g0E3,30bEEDIa-albLIELI - ===-- 1 == +--- ''i I ElOabe(;17151:7E1 (10e3 00 E r:r.: ZEE Litiiii L 1-3E, - 2 .1 go400rionclg 1.100000040-'Et:EELO-Li.44o-JOG, r.::::7 17 1 °OW:X00GO (1=15000 E E EEt: t.-,z)1900060 fib 1 0000Eleao OnM00002,E.EbbuTZa4_,Olatt r.....% I IIMEMEO-I.300t9 0000E1090tat0014 Et_js-- = LI Liti LIG i) I I snumn000nnoom000LE..-=uad3Et;-=-+---+1 I fincinnimoo En ow at:ma r.; t;t30 === = thiti ti o I 00150Rnn-30000W44000Eibti,====81==--+--==-= j I 000011004fr:00 000.4 40 0 ELL-s- - ___ j I - [email protected])00t4r,0445.Df.L.-- - 3 I ' i.it3Et1L---4t04dW454000Zt,40)Li.E.. ++,1 ++++) I ' iila="7.=ED1 '40EE ,;JP00000GEEt,4?..E hits -- - I - ==E1.3._1==I0EEK;t:in. 1,00000t4Litii:Ek: trio ====----++----++++ I • ===dEi:E1-33bEtitiLib Jr,40001-7.EEEr.:2:::::f.d.i,)===----+--z3u-z++- 3 I ' EuL:a:131:4g;.i,:.EiEbb=,ioULit,J00/Out; Lzi,.;i:LiBili- iii:E= =-01 .I --E3E, ELUL) Et.-D-oiit:i. === EE4G0e000f. I: 33u1==== ----==--Lidr_o63i/;1= 301 I --+-LEGf,.:311Eti,i;i33tiLbouvV004t0000g +++ I =-=-.J0th:EE3ii;ELd;ELgOOCdtidt4dOr.- , Lic; 3 +++++ ---- I -- ===-=(10::f4OJEOLL%, J3L/iEt'g00300tELob=--- 1 13 11:: .. 3 ++- =lb Lt -...r:L.3 Li ' G L. i5f../O'JOOdt.-7 74 GU -000 1.1: i Eiri0Eit,'/,i;1, ---- +++++ +++ ++ -- + -1 I ' g-f+--,4-31' 4G.,:,;300001.1[9f311E70€1b00 ?)00G .0(;r204z4z;b1-++++-++++ „ I iji==--+-000009066F17,nrIrli.V.30000-300000t3IVIE.4==-+-;++-+.+++if„ ++i-----==-++++--3 • I - 3i.. .,'.)011:I-'ElorrIn.flilno(50-Jti..)0360Orkwl.jz= ++, + +, „ ... 11 , 1 ++ if, , , t+ 3 .1+- 433:.L 40 00;.ThEifiL.rifirillOo.3000f13 ' 0 vlr.L.,F++ +- ++ ++-= - 7,1 7 7 • •• .77 7 4.----+7/ / 7 4- t 3 I =18,3,.:EEE.t:/.,:a01-J.GooLlithioGr.,.,,,,,,o19,-;,Gt..2_0.,=-+-C1++++++-=-+++-11, „ .... , +---++ „Ft-- --3 I ..-7.:. t:r;).".1.).:1-; 46- Lt,10000,90P r:b1-30/..i.i.rtr + ++++++-=-==----1 +h. . , +-- -- +i,ff - - -+3 t, „++--- -+r+- --+ I 'it:Et:LE 33EL 3bou ,LE 1.3,..,==-:-I)u__s •==-=-= U ++ === -=== +---==-+=++ ++++1++1, I 6j.)siiL,=u) - iiJJ db = 9 0 I +-- =cEEi E ' 13o .,.1E)03i, _ = LE = - .77aZOi -7710-1-G'q I +--=- ==01= -====„711--=13Le. . Jsuou Li,)- ,,,,,, - f I --- __- __ ... _ _ _ +-- .;J_,== --++ - DE,L). == ---=3 3L,o4=== -+ 171.9 • 4, 17ft1 DuLdujo=-+++===+f -+++T+,,,...,,,J I =-47D= t+ --=-+---f+ I --- -= -agr:uji_idD=-+++---i ++-++,, A++++-- 8 ii==-Lib=-++-++ ++++ I i===---=-+---++ I ' 071-+---- L . I +1-,1+ ++ + 1-1.. i ++--+++-++++I I I -,1++++++++5;, , , .1 I 777/177777/7 0 .I I 1117177 ++, +--- I I ;1+ 1 ++++---- I 3 3 I I I++++++++++++ 1. 4-++++++++++ +++++++1•++++++++++++++t+tttttt• ttttttt tttttttttttttt j Fig. 5.30 • 110. 5.3.14 Zinc (Fig. 5.31) Excluding high background values greater than 300 ppm, due mainly to contamination from past mining activities, high zinc patterns (100 to 300 ppm) tend to concentrate on areas of Pre-Cambrian, Ordovician, Silurian and Carboniferous rocks, Devonian and younger rocks display lower background values (50 to 100 ppm). Zinc tends to follow mountain areas and dissected plateaux, with the exception of the mountain areas of South Wales. High background patterns (greater than 300 ppm), are present over know mineralization and around the Swansea-Rhonda industrial area. 5.4 INTEGRATED SUMMARY OF THE REGIONAL GEOCHEMICAL VARIATION Considering the reconnaissance data as a whole, while there are certain similarities in the regional distribution of several elements, there are also wide variations in detail'. The regional composite patterns are as follows: 1. The outstanding regional geochemical feature is the general decrease in trace-element content on passing from Lower Paleozoic to Upper Paleozoic along the line of the Silurian and Carboniferous-Triassic contact west of the Vale of Clwyd in North Wales; the Church Stretton fault in Central and South Wales; and along the line of Ordovician-Silurian and Devonian contact in South Wales. This feature is strongly shown by gallium,cobalt, iron, nickel, manganese, vanadium, titanium and zinc. 2. The second outstanding geochemical feature is within the Upper Paleozoic, with a sharp increase in trace-element content from Devonian to Carboniferous along the line of contact of both formations. This feature is strongly 1/1000000 ZINC • <50.0 + 50.0 - 99.9 = 100.0 199.9 B 200.0 - 299.9 o 300.0 - 399.9 [J >400.0 in p.p.m. I I I I I I I I I I I I I I 1 I 1 I 1 I 1 I 1 I 1 1+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 Fig. 5 .. 31 • 11Z. outlined by arsenic, cobalt, copper, lead, manganese, molybdenum, nickel, and to a lesser extent, by zinc. 3. Background patterns of high base-metal content associated with other elements occur over, and adjacent to, known mining areas within the metallogenic districts encountered in Wales, and this is discussed in detail in Section 5.5. 4. Arsenic, cadmium, iron, manganese, nickel and to a lesser extent, zinc and cobalt display patterns of higher values over mountain areas and dissected plateaux cored by Lower Paleozoic rocks, coinciding with areas of peaty soils with impended drainage of the uplands. de 5. Lithologically there is an 4mcrease in the metal content from argillites to sandstones with the exception shown by chromium. Enrichment of sediments by organic matter is conducive to an increase of most of the trace-elements, with the exception of barium, chromium, gallium, titanium and vanadium. 6. Smaller scale background patterns include: (a) the association of barium gallium, manganese, titanium, and to a lesser extent chromium and tin with Ordovician intrusive and extrusive rocks. (b) the association of molybdenum with black shales of Cambrian, Ordovician and Silurian age. (c) the decrease of barium, copper, chromium, gallium, lead, titanium, and to a lesser extent, cobalt,over the Silurian in the Cardigan coast synclinical tract. (south of Aberystwyth). (d) the association of chromium with Devonian sediments. 113. 5.5 RELATIONSHIP BETWEEN THE GEOCHEMICAL PATTERNS AND THE GEOLOGY 5.5.1 Introduction Large sets of samples covering regional geological strati- graphic units have been examined. These sets have been selected from the 9910 samples that form the regional reconnaissance data. 124 samples draining Pre-Cambrian sediments have been selected from the Monian complex of Anglesey and the Lleyn peninsula; 126 samples draining Cambrian sediments from the Harlech Dome and Cader Idris range; 201 samples from six smaller areas draining Ordovician sediments; 382 samples selected from five smaller areas draining Silurian sediments; 385 from Devonian sediments (Downton and Ditton Series); and 261 samples from Carboniferous sediments, only those from the Culm and Coal Measures and Millstone Grits (South Wales Coalfields) being considered. Samples from the Triassic have not been treated as this system was thoroughly investigated by Davies (1971). Supporting rock and soil data has been compiled from the follow-up areas that the author has covered and from the very few references available. 5.5.2 Correlation with Regional Geological Stratigraphic Units The geochemical characteristics of the stream-sediments derived from the regional geological stratigraphic units are summarized in Table 5.1 and Figure 5.32 illustrates the distribution of the metal content in relation to the thickness of the strata found in Wales (Table 2.1). 114. Table 5.1 Range and Mean Content of Minor Elements In Stream-Sediments Associated with Regional Geological Stratigraphic Systems Minor Devonian(I) (2) Element Pre-Cambrian Cambrian Ordovician Silurian Carboniferous (ppm) Downton Ditton 12 43 24 14 29 As * 7 5 <4 - 30 1 - 250 2- 113 2-59 1 - 36 <4 - 15 <4 - 57 200 325 250 257 182 Ba + 11 - 469 109 - 967 141 - 447 150 - 44o - 78 - 423 Cd 1.11 1.51 1.04 1.89 0.46 0.15 2.38 28 36 25 2; 22 20 31 Cu + <2 - 606 5 - 249 7 - 89 II - 48 8 - 61 N.D. - 80 7 - 133 * 12 18 16 16 9 5 10 Ga 5 - 18 9 - 33 7 - 34 9 - 27 3 - 22 NAL - 11 • :5 - 19 Fo(%) * 4.02 5.98 5.36 4.89 3.17 3.07 3.58 0.76 - 7.27 3.5 - 11.01 3.5 - 9.2 3.0 - 8.0 2.1 - 5.3 1.0 - 5.0 0.51 - 6.65 40 31 30 18 10 Pb + 57 N.D. - 196 5 - 324 6 - 156 7 - 127 3 - 29 N.D. - 65 7 - 455 826 1029 + 1400 1710 1036 876 570 Mn 1 17 - 9064 310 - 9452 157 - 6861 134 - 5748 277 - 2462 N.D. - 1144 117 - 9064 * 4 no 1 5 4 3 2 _ 3 <3 - 4 1 - 15 1 - 31 I - 7 1 - io <3 - 6 <3 - 9 43 Ni + 20 41 39 43 35 28 3-49 13 - 131 18 - 85 19- 101 8 - 145 ; - 62 7 - 258 24 12 27 Sn 36 8 3 33 <4 - 158 1 - 1600 1 - 89 I - 156 1 - 7 N.D. - 120 <4 - 153 Ti * 4599 4688 4754 4495 4492 4296 4143 1164 - 8034 1868 - >9000 2829 - 7587 2975 -6561 1510 - 8500 1345 - 7247 2203 - 6083 * 67 88 85 76 61 44 57 V 14 - 119 27 - 226 39 - 166 41 - 134 II - 250 N.D. - 92 N.D. - 113 116 315 190 197 82 68 315 Zn <50 - 941 <50 - >9000 <50 - 1133 <50 - 1173 21 - 286 <50 - 488 <50 - 1533 * Normal distribution + Log normal distribution * Geometric Mean + Arithmetic Mean Background Range . Mean (log + 2 std, dev. (log) • COPPER NICKEL 50 30 IC COBALT VANADIUM CHROMIUM 0 20- GALLIUM MOLYBDENUM 2 MANGANESE 2 TITANIUM IRON (V.) 10 24 49 .0 0 5 D CF App. horizontal scale 1 inch: 100,000 feet Fig. 5.32. Distribution of metal content in relation to the thickness of the strata, (Table 2.1). Pc: Pre-Cambrian; C: Cambrian; 0: Ordovician; S: Silurian; D: Devonian; CF: Carboniferous 116. Comparison of the mean values shows: 1. The marked enrichment of all the elements, with the exception of chromium, in sediments derived from Pre- Cambrian and Lower Paleozoid rocks, compared with those from the Upper Paleozoic. 2. The continuous increase of metal content in sediments derived from Pre-Cambrian to those derived from Cambrian rocks, and the continuous decrease from sediments derived from Cambrian rocks to those derived from Ordovician, Silurian and Devonian rocks. 3. With the exception of chromium, there is a sharp increase of all elements in sediments from Carboniferous rocks, compared with those derived from Devonian rocks. This increase reaches similar concentration levels as those in the Lower Paleozoic bedrock. 4. Although most variations in the trace-element content of stream-sediments within a single regional geological system principally reflect analytical and sampling errors, thus some regional trends are difficult to explain. Within the areas underlain by Pre-Cambrian and Cambrian no distinct variation is detected. Within the area underlain by Ordovician rocks, higher levels of arsenic, cadmium, manganese, molybdenum, nickel and to a lesser extent iron, lead and tin, are found in North Wales compared with mean levels in South Wales. Barium, cobalt, copper, gallium, titanium, vanadium and zinc show no variation. Chromium is the only element with higher mean content in the south. This metal distributioh reflects to some extent the sedimentation facies, shelly and graptolitic, described by Williams (1969), and to the difference in origin of the sediments, Baltic Providence in the north and Anglo-Welsh in the south (Williams, op.cit.). 117. 5. Over Silurian bedrock the mean levels of arsenic, iron, lead, manganese and molybdenum, and to a lesser extent, nickel and tin, show a higher content in the Lower Silurian. Chromium is the only element showing higher mean level in Upper Silurian sediments, the rest of the elements show the lowest mean levels in the system. Titanium and zinc, and to a lesser - extent, vanadium, show lower mean levels over the Middle Silurian. This metal distribution reflects, somewhat the patterns of sedimentation described by Cummins (1969), with the turbidite facies in the Lower Silurian (Llandovery), the graptolitic facies in the Middle Silurian (Wenlock), and the shelly facies in the Upper Silurian (Ludlow). 6. Within the Devonian strata, the mean levels of arsenic, cobalt, copper, gallium, lead, manganese, vanadium and zinc are twice as high in the Lower Devonian (Downton), than in the Middle Devonian (Ditton). The conditions of sedimentation in both Series are similar, excepting that the former is more argillaceous in character (red marls) than the latter, that tends to be more arenaceous. This lithological difference is reflected in the trace-elements content. 7. Over Carboniferous rocks (Millstone Grits, Culm and Coal Measures), the trace-element content reflects the lithology of the Series and the high concentration of them in the coalseams. The central and western flank of the coalfields display higher mean levels of arsenic, cadmium, cobalt, copper, lead, manganese, molybdenum, nickel, tin and zinc compared with the southern and eastern flank. These 118. variations follow to some extent the distribution of the different types of coals forming the coalfield, that is anthracite towards the northwest, steam coals in the centre of the coalfield and bituminous coal in the southern and eastern side of the coal field (Rowland, 1965). This high natural concentration is also enhanced by the airbone contamination as previously described. 5.5.3 Correlation with Predominant type of rock Limited rock sampling was restricted to follow-up studies concerned mainly with the relation of geochemical variation to base-metal mineralization. Other sources of rock data in Wales are limited, and an entire picture. of their geochemistry is incomplete. However, it is possible to examine and compare the stream-sediment data with that of the predominant type of rock (Fig. 2.4), considering both groups of data as true to broad regional variations and not to local and detailed variations. Rock data is summarised in Table 5.2 and compared with the summary of stream-sediment data of Table 5.1, the Following composite correlation can be drawn: 1. Barium, chromium, copper, gallium, lead, molybdenum, nickel, and vanadium display similar mean values in the stream- sediments and the underlying bedrocks. 2. Cobalt, iron, manganese, tin, titanium and zinc show a slight enhancement of mean levels in the stream-sediments compared with values in the bedrocks. Secondary environmental features as absorbing and scavenging of cobalt and zinc by precipitation of manganese-iron oxides 119. S Table 5.2 Mean trace-clement-content from Predominant Types of Rocks In Wales Hard Volcanic Volcanic Anthracite Low Volatile Black Mudstones Slates & Intruslves Intrusives & Shales Greywackes Sandstones Rock Rock Coal & Bituminous Shales Acid Basic. (A0) (A3) (A5) (83) Rhyolites Andesltes (organic) Coal (Org.) As <5* n.a. <5* n.a. 9* n.a. n.a. n.e. n.a. n.a. --- Ba n.e. n.a. 350 n.e. 820 n.a. floci* n.e. n.a. Cdn.a. n.a. n.a. n.a, n.a. n.e. n.a. n.e. n.e. n.e. Cr 45 79* 58 135* 14 80 20:, 192 n.e. n.a. Co 6 22 28 18 6 45 5 56 360+ 360+ Cu 44 29 35 22 18 40 26 330 560 460 Ga 23 20 16 18 20 27 31 27 48 45 Fe(%) 3.4 3.9 2.7 3.3 1.5 1.2 2.5 10.2 12.3 9.6 Pb 24 13 33 22 29 10 27 10 520 280 Mn 210 1700 600 650 350 1200 610 5000 2000 1350 Mo 8 <2 3 <2 3 <5 <5 <5 318 220 NI 23 6o 38 25 10 60 8 55 842 865 Su n.e. <5 <5 <5 5 <5 10 5 37 25 Ti 2950 3000 3250 3000 740 n.a. 2100 >10000 10000 9300 V 100 - 85 117 65 26 160 30 210 232 283 Zn 80 225 130 90 120 100 80 85 603 322 No.of 36 15 63 12 41 5 5 30 12 23 samples a b + c 4. p d +p b f • s • e P P P g 9 f + e Sources: a: Thomson (1971) b: Wood (pers. comm.) c: Holmes (pers. comm.) d: Kakar (1971) e: Horsnall (1968) f: Jenkins (1964) g: Rowlands (1965) p: author * geometric mean + arithmetic mean 120. in the strewn beds due to increase of ph and Eh, has been thoroughly covered in the literature (Canney, 1966; Horsnail, 1968). The high mean content of tin and titanium in the stream-sediment data could be due to sedimentation and/or sorting of heavy minerals cassiterite and ilmenite in stream beds. 5.6 RELATION OF GEOCHEMICAL VARIATIONS TO MINERALIZATION 5.6.1 Introduction Undoubtedly most of the lead, zinc and copper anomalies are related to past mining and smelting activity. The metal patterns from buried mineralization tend to be masked by anomalously high concentrations derived From contamination and it is unlikely that regional reconnaissance surveys will lead to the discovery of new deposits in former mining districts. However, in view of the importance of base-metal mineralization in Wales, particularly in the Southern Caledonides Metallo- genic District, marginal and possibly anomalous patterns are assessed. A number of elements have been recorded at anomalous levels, but, only copper, lead, zinc, molybdenum and tin are considered likely to have any immediate economic significance. Threshold + 2s), and 'probably anomalous' levels + 3s ) have been calculated for each regional stratigraphic unit and for the regional data as a whole (Table 5.3). A modified version of the PLTLP Grey-Scale computer program has been used to plot maps of samples with 2 standard deviation above annulus mean inside a filter frame covered by an aperture of 5 cells. These maps outline possibly significant anomalies • s • 111 Table 5.3 Threshold and anomaly levels for log 10 transformed reconnaissance data. No. Cu ppm Pb ppm Zn ppm Mo ppm Sn ppm SYSTEM of Samples M* T* A* M T A II T A M T A M T A CARBONIFEROUS 261 31 133 57 455 315 1500 3 9 27 153 DITTON 200 20 95 131 10 65 91 68 187 247 2 6 8 33 280 426 DEVONIAN DOWNTON 185 22 61 100 18 101 235 82 187 300 4 10 17 3 7 15 SILURIAN 382 23 48 70 30 127 258 197 335 430 3 7 12 12 238 1800 ORDOVICIAN 201 25 89 168 31 156 348 190 1130 1500 4 9 20 8 113 315 CAMBRIAN 126 36 249 665 40 320 920 185 350 500 5 15 28 24 220 430 PRE-CAMBRIAN 142 28 606 875 196 273 166 941 1329 1 4 6 36 159 220 REGIONAL 9910 21 40 54 23 74 90 90 180 330 4 18 24 M* : geometric mean 1-* : Threshold A* : Probably anomalous 122. are illustrated in Figures 5.33 to 5.37 and the following description is based on them. 5.6.2 Possibly Significant Anomalies of Copper (Fig. 5.33) As stated before most of the larger anomalies of copper coincide with known mining districts, the exception being those over the coalfields of South Wales. I. Anomalies from 'A' to 'H' coincide with known mining districts. 2. Anomalies from 'K' to 'M' are basically related to type of rock and high concentration of metal content in the coalsearns (Sections 5.4.2 and 5.4.3) 3. Anomaly 'A' is in streams over Ordovician rocks in contact with the Coedana granite and Pre-Cambrian gneisses south- west of the Parys-Mona mine. The anomaly is interesting as it is located in a favourable tecto-stratigraphic setting. 4. Anomaly 'I' occurs over Ordovician-Silurian rocks and it is interesting as it follows favourable structures and is located near the Ogofau gold mine. 5. Anomaly 'J' is located in North Pembrokeshire. The area here has a number of similarities with the geology of the area north of Dolgellau (Dolgellau gold belt), where disseminated copper ore has been recently located in flags and intrusive rocks. 5.6.3 Possibly Significant Anomalies of Lead (Fig. 5.34) The anomalies of lead show similar distribution to those of copper, with the larger anomalies overlaying known mineralization. • 123. 1. Anomalies 'A' to 'H','J', 'P' and 'R' coincide with mining districts ('R' coincides with the Shelve-Habberley mining district of Shropshire). 2. Anomalies 'L' to 'N' and partly 'K' coincide with Carboniferous rocks forming the coalfields of South Wales. • 3 Anomaly 'I' is in streams draining Silurian rocks and is located between known mining districts, with no contamination sources. The tecto-stratigraphical controls are favourable for possible mineralization. 4. Anomalies 'K' and '0' occur over Ordovician and Silurian rocks with favourable structures and they could reflect true mineralization, 'although further investigation • is necessary. 5.6.4 .Possibly Significant Anomalies of Zinc (Fig. 5.35) The distribution of zinc anomalies is similar to some extent to those of lead. Larger and more prominent anomalies occur over lead/zinc mining districts. It is important here to consider the effects of secondary environment in the dispersion 4 of zinc though this effect is not reflected in the map, as the high levels of zinc found in the mountain areas reflect back- ground and not variation above annulus mean. 1. Anomalies 'A' to 'D', 'I' to 'K' and 'M' are in streams contaminated by old mine workings. 2. Anomalies 'I' to 'H' are in streams over Carboniferous Limestones and Upper Carboniferous rocks. Lead/zinc mineralization is found in the limestones and high zinc concentrations are also found in the anthracitic coalseams 124. of the coalfield (Rowland, 1965). 3. Anomaly 'L' is located over favourable geological settings, and becomes interesting as no source of contamination is known. 5.6.5 Possibly Significant Anomalies of Molybdenum (Fig. 5.36) Although molybdenum mineralization is not recorded in Wales, this element is reviewed as core drillhole samples from Coed-y-Brenin (anomaly 'D') show small flakes of molybdenite in flags (Cambrian) and iorites (Ordovician) associated with disseminated chalcopyrite (RTZ, 1971). Similar geological conditions are found in anomalies 'K' and 'L'. 1. Anomalies 'B' and 'C' are associated to Ordovician rocks intruded by dolerites anddiorites of the same age. 2. Anomaly 'H' by its shape and size, although over favourable geological settings, is an analytical day- error. 3. Anomalies 'M' to '0' over Carboniferous rocks have a similar origin to those of lead, copper and zinc already reviewed. 5.6.6 Possibly Significant Anomalies of Tin (Fig. 5.37) Mineralization of tin has never been found in Wales, and the review of this element is made since the reconnaissance survey has produced a series of anomalies that need further investigation. Although the precision of tin is very poor, in the analytical method employed, several anomalies cannot be explained by this factor. 1 25. 1. Anomalies 'B' and 'H' occur over acid intrusives and extrusives of Pre-Cambrian and Caradocian age. Oxidised veins in Ordovician rhyolites have been recorded with tin values up to 200 ppm (Jenkins, 1964). 2. Anomalies 'I' to 'M' are airborne contamination from industrial fumes and spread by prevailing winds (see Sec. 5.3.13). 3. Anomaly 'G' could have the same origin as the molybdenum 'H' anomaly. MINEX WALES •• URQUIDI COPPER GEOCHEMICAL MAP 1/1000000 PICTURE FRAME FILTER. 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I I I 1 • I I I 11-1- ++++++++++++ ++++++++++++++++1-+++ ++++++++++++++++++++++++++++++++++++++++ Fig. 5.37 1.31. CHAPTER VI INTERPRETATION OF THE GEOCHEMICAL RECONNAISSANCE DATA USING R-MODE FACTOR ANALYSIS 6.1 INTRODUCTION The application of univariate techniques to the reconnaissance data of Wales as presented in the previous chapter, has revealed certain correlations and associations of variables (elements), with the inevitable result of some data redundancy. Furthermore, the overall geochemical variation shown by a multivariate data analysis is more likely to respond to and preserve the underlying causal effects (geology, mineralization, secondary environment, etc.), which may not be adequately described by the variation of a single variable. As the intercorrelations between chemical elements in geochemical environments are normally complex and difficult to recognize, a Factor Analysis has been employed in order to outline these intercorrelations as single associations or factors. Factor analysis is one of the most common and relatively successful multivariate techniques used in geological and geochemical exploration projects (Khaleelee, 1969; Nichol and others, 1969; Armour-Brown, 1971; Celenk, 1972; and several others). The present chapter deals with the application of R-Mode Principal Component Factor Analysis applied to the regional data as a whole and to the selected data sets of the regional stratigraphic systems. The.use of factor analysis on follow-up areas will be discussed in their respective chapters. A brief 1 32. outline of the method is given with a review of Garret's (1967), computer program used, followed by the different steps taken in the selection of suitable sets of associations and by the description of the spatial distribution of the calculated factor scores for each example. Analyses of fourteen elements were used in the computation, namely barium, chromium, cobalt, copper, gallium, iron, lead, manganese, molybdenum, nickel, tin, titanium, vanadium and zinc. 6.2 OUTLINE OF PRINCIPAL COMPONENT FACTOR ANALYSIS Factor analysis is a statistical technique developed with the aim of analysing the interrelations inherent in multi- variate data. A full account of the technique is given by Harman (1967), and a comprehensive one is given by Child (1970). Davis (1973) gives comprehensive examples with geological and geochemical data. The prime objective of factor analysis is to simplify a complex set of variables by expressing the total variance of the set in as few factors or theoretical variables as possible. The analysis may proceed by examining the relationship between variables (R-mode analysis) or between samples (Q-mode analysis). In this thesis only the relation between variables has been examined using a R-mode principal component factor analysis. This technique has its basic starting point in a product- moment correlation matrix of the variables with units in its principal diagonal. The product-moment correlation coefficient is computed from a covariance matrix of cross- products. 133. Principal components are obtained from the product of the eigenvectors of the correlation matrix and the square root of the associated eigenvalues. This product is the initial factor matrix or solution. The initial matrix is rotated (orthogonal data transformation) using the Kaiser's Varimax criteria. The varimax rotation is used in an attempt to maximise the variance between the loadings on the separated factors while minimizing the variance of the loadings within each factor. The R-mode factor scores computed as vectors for each sample are determined by Harman's method of ideal variables, and are only approximate. 6.3 PROCEDURE As a result of the univariate analysis the regional data has been transformed to the logarithm base 10. This transformation produces a close approximation to a normal- gaussain distribution with the product-moment correlation coefficient matrix statistically more meaningful. As a comparison, the untransformed data was similarly processed and compared with the log 10 transformed data, the associations produced with krmsforpt_A. the 1-01.44-e-F—st.oe are geochemically more significant. The correlation matrix to be factored is given in Table 6.1, the values shown are product-moment correlation coefficient, as previously defined. Taking a correlation coefficient of 0.6 and greater (over 99% confidence level), three distinct associations are formed, namely: Ga - V - Ni - Co; V - Ni; and Co - Ni. These associations are on four elements only of the fourteen computed showing that correlations between 134. the rest of the data are difficult to define. R-mode factor analysis overcomes this problem. The correlation coefficient matrix was factor analysed with unities in the leading diagonal. 3 to 14 factor models (associations), have been extracted from the unrotated and rotated factor matrix. In order to maximise the few high loadings of each of the factors, these were rotated orthogonally (Varimax rotation), and obliquely (Promax rotation). The resulting loadings of the elements on the oblique axes showed similar results. The associations extracted are listed in Table 6.2. Only those elements with factor loadings of 0.3 or greater are listed in this table. The arbitrary limit of 0.3 was selected on the basis that this factor loading value represents more or less 10% of the variance (Child, 1970). Armour-Brown (1971), Young (1971) and Davies (1971) also use this arbitrary limit with significant results. The rotated factor matrix of seven factors explaining approximately 81.6 per cent of the total variation in the data was selected using Catell's 'scree test' (Child, 1970), and are shown in Table 6.3 and Figure 6.1. The headed communality indicates what proportion of the variability of any particular variable has been explained by the seven factors selected. The low communality of zinc suggests that this variable is probably better contained in the 12th factor or higher. Negative signs have been neglected except where a variable has a significant loading value of opposed sign to the dominant variables in the same association, indicating a strong negative correlation. Table 6.1 Correlations coefficients of minor elements from reconnaissance data MATRIX TO BE FACTORED VARIABLE NO. NAME 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 Fe 1.000 _2 Ga .436 1.000 3 Mo .147 .298 1.000 4 Cu .224 .332 .239 1.000 5 Pb .167 .473 .250 .440 1.000 6 v .331 .791 .331 .334 .473 1.000 7 Ba .326 .217 .152 .239 .289 .177 1.000 8 Co .337 .649 .403 .352 .359 .561 :174 1.000 9 Cr .150 .263 .097 .268 .064 .327 .062 .217 1.000 10 Ni .277 .653 .329 .329 .368 .638 .156 .733 .277 1.000 11 Mn .223 .266 .226 .269 .246 .244 .105 .402 .128 .213 1.000 12 Sn .091 .148 .311 .184 .195 .166 .098 .183 .080 .165 .151 1.000 13 Ti .283 .272 .205 .202 .031 .329 .190 .312 .434 .265 .166 .145 1.000 14 Zn .348 .341 .236 .365 .398 .318 .255 .325 .087 .264 .352 .108 .183 1.000 Table 6.2 Minor element associations and loadings of R-mode factor models 3 4 5 6 7 8 9 10 II 12 13 14 • Factors Co.31 V .66 Co.81 V.61 NI.85 V .82 V.85 Fe.77 NI.85 Ga.85 Ga.85 Ga.84 V .85 V .87 •• Pb.43 Fe.77 2n.54 V .79 Ga.82 NI.83 NI.84 NI.82 Ga.82 Ga.83 Ga.76 Mn.73 Pb.33 Fe.45 V .80 Ga.78 1 Ga.76 Cu.39 V .80 v .82 V .81 Co.73 Fe.57 N1.42 N1.38 Ca.71 Mo.32 Ga.82 N1.85 Ni.39 Kn '69 Zn •61 Co.74 Co.71 Co.73 Ga.39 NI.398 Co.37 Co.33 Ni.67 NI.64 Cu.30 Co.73 Mo.37 Fe.49 Fe.49 Fe.L,9 Fe.33 Fe.36 Fe.32 M0.34 Co.33 Pb.74 V .84 Sn.63 Ba.74 Pb.63 Ba.73 Cu.77 Ba-.82 Pb.78 Fe.46 Cu.60 Zn.76 2 Ba.62 Pb.71 Pb.78 Fe-.67 Cu.71 NI.39 Cu.91 Cu.91 Cu.91 Cu.92 Cu.54 Zn.52 Cu.60 Zn.45 Zn-.33 Zn.68 v.31 V .31 Pb.39 Mo.5I Zn.55 ea.31 Co.32 Ga.3I Cr. 79 Cr.77 11.74 Cr 86 71.76 Cr.81 11.74 Cr-.85 • V .51 Cu.43 Cr.93 Cr.94 Cr.95 Cr.95 Cr.96 Cr.96 3 v.46 71.79 Cr.84 Ti-.75 Ni.38 NI.41 Ti.3) Ga.40 Sn-.86 Sn-.86 4. Mo-.6/ Sn.96 Sfl-.97 Sn-.97 Mo-.64 Mo-.68 Sn-.86 Sn-.97 Sn-.97 Sn-.97 Sn-.97 Sn-.97 Mn-.88 Mn-.88 Mn-.92 Mn-.92 Mn.85 Mn-.92 Mn-.93 Mn-.94 Mn-.94 mn- 94 Fe-.67 Fe-.67 Fa.68 Fe-.61 Fe-.52 5 Co-,44 Fe-.62 Fe-.55 Fe-.32 Fe-.33 Zn-.53 Zn-.53 Zn.53 Co-.43 Co-.40 Co-.39 Co-.31 ' Fe-.32 Co-.42 Co-.43 Co.31 Zn-.33 Zn-.41 Co-.31 Cu-.73 Pb-.73 6 Ba.92 ea.97 Ba.98 8a.97 8a.98 Ba.98 Ba.98 Zn.30 Zn-.39 Ba.97 Ba-.30 No.80 Mo.91 Mo.92 Mo.93 Mo.94 Mo.94 7 Co.30 M0.94 M0.94 71.82 TI.87 Ti.88 Zn.89 Zn.89 8 Zn.37 Pb-.36 Fe.30 Zn.89 Zn.90 Fe.3I Cu-.92 Cu-.08... T1-.94 TI-.94 TI-.94 Ti-.94 9 Pb-.40 NNi-.83 Zn-.88 NI-.83 l0 C o-.74 Co-.77 Cr-.61 Co-.72 Pb-.53 Ga-.35 Ga-.39 II . Pb.87 Pb.90 V.9 Pb.90 12 Fe-.77 Fe-.78 Fe-.79 NI.84 13 Co.74 Ga-.39 NI.84 14 Co.39 I • • • • V Table 6.3 Rotated Factor Matrix of the seven factors (associations), selected using Catell's 'Scree test'. ROTATED FACTOR MATRIX COMMUNALITY VARIABLE 1 2 3 4 5 6 7 7 FACTORS Fe .803 .369 -.670 -.128 .130 .678 .144 -.224 Ga .836 .864 -.182 -.093 .062 .116 -.174 -.024 Mo .848 .261 -.078 -.048 .191 .139 -.081 .843 Cu .706 .16o -.079 -.278 .067 .223 -.733 .077 Pb .766 .205 -.134 .176 .116 .091 -.727 .039 v .775 .817 -.092 -.192 .077 .050 -.231 .027 Ba .816 .021 -.817 -,053 -.033 -.079 -.304 .211 Co .766 .744 -.052 -.121 .013 .316 -.067 .301 Cr .803 .192 .088 -.847 .014 -.007 -.183 -.086 Ni .761 .826 -.011 -.144. .010 .053 -.132 .196 Mn .802 .142 .050 -.080 .061 .861 -.110 .124 Sn .976 .075 -.024 -.057 .963 .048 .110 .181 Zn .627 .178 -.332 .004 -.019 .576 -.389 .029 Ti .737 .178 -.266 -.755 .065 .122 .110 .181 ■ E I GENV ALUES . Fig.6.1. 1 2345 67891011 Catell's 'scree test'forselection ofsuitableFactor Model (Associations), to beextracted. Factor Models(Associations) 139. 6.3.1 Results of R-mode Factor Analysis An examination of the loadings on Table 6.3 of the Varimax rotated components reveals the following associations: (a) Factor 1, represented by the association of Ga - Ni - V - Co - Fe, explaining 44.3% of the total variation. (b) Factor 2, represented by the negative association of Ba - Fe - Zn, explaining 12.0% of the total variation. (c) Factor 3, represented by the negative association of Cr - Ti, explaining 10.8% of the total variation. (d) Factor 4, represented by the association of Sn, explaining 10.1% of the total variation. (e) Factor 5, represented by the association of Mn - Fe - Zn - Co, explaining 8.4% of the total variation. (f) Factor 6, represented by the negative association of Cu - Pb - Zn - Ba, explaining 8.4% of the total variation. (g) Factor 7, represented by the association of Mo - Co, explaining 6.2% of the total variation. The spatial distribution of these associations may reflect environmental and geological factors. 6.4 REGIONAL DISTRIBUTION OF FACTOR SCORES The computed R-scores of each sample in each association have been plotted in map-form using the percentile moving- average of the PLTLP Grey-scale computer program. The R-score 0 data was smorthed (moving average), as only the regional features controlling the element correlation are needed to be interpreted. The percentile version has been used as no prior knowledge of the R-score grouping is needed with it; two or 140. three deciles have been pooled together as their spatial distribution is compatable. The frequency distribution of the grey-levels in the maps is displayed in Fig. 6.2. 6.4.1 Factor 1 Ni - Ga - V - Co - Fe Association Gallium, nickel and vanadium are associated with the same high loading of 0.8; cobalt has a loading of 0.7 and iron has a lower loading of 0.4. The spatial distribution of the R-score of this association given in Fig. 6.3 shows a distinctive high RTscore pattern over Ordovician and Silurian rocks, an exception being over Ordovician rocks outcroping in the Lleyn peninsula and Pembroke- shire, which show low patterns. The higher R-score patterns are located in the turbidite facies of the Silurian. Samples from younger formations display low R-score patterns. This association is undoubtedly a reflection of the high correlation of high values of these elements in argillitic rocks. 6.4.2 Factor 2 Ba - Fe - Zn Association Barium and iron are associated with negative loadings of 0.8 and 0.6 respectively, and a somewhat lower negative loading of 0.3 for zinc. Since this factor is represented by a negative association, the high R-score patterns indicate low concentration of these elements, and vice-versa the low R-score patterns indicate high concentrations. 141. The spatial distribution of R-scores from this association is given in Fig. 6.4 with high R-scores over Pre-Cambrian, Cambrian and post-Silurian rocks, with the higher values in the streams of the Usk catchment area draining Devonian sediments and over Carboniferous rocks in the Gowen penninsula. An inspection of the regional distribution of the lowest R-scores group shows that the samples from Ordovician and Silurian rocks are dominated by this group. Following in South Wales the structure of the Tiwy anticline. This association outlines with its low R-scores (high concentrations of the elements), known and possibly mineralized areas of lead/zinc in the Southern Caledonide metallogenic district. 6.4.3 Factor 3 Cr - Ti Association Chromium and titanium are associated with negative loadings of 0.8 and 0.7 respectively. The spatial distribution of this association given in Fig. 6.5, displays high R-score values (low concentrations), mainly over Carboniferous, Triassic and Liassic rocks, with the highest values over the Carboniferous Limestone Series of North Wales, similar values are found over Ordovician rocks intruded or interbedded with acid igneous rocks and over Silurian rocks of Central Wales. Low R-score values (high concentrations), are distributed over Devonian sediments and over Ordovician rocks intruded or interbedded by basic igneous rocks. The lowest value of this factor are found in the Usk catchment area; the Mynydd Prescelly; the Ordovician volcanic 'ring of fire', along the FREQUENCY DISTRIBUTION OF GREY-LEVELS IN HAP FREQUENCY DISTRIBUTION OF GREY-LEVELS IN MAP PERCENT= 10 2 30 4 PFPCFNT= 0 10 20 30 40' LEVEL I I I.I I .. I LEVEL I I I I 1 1 -III 2.87 1 -III . 2.6: 2 -IIIIIIIII 9.39 -IIIIII F.03 3 -IIIIIIIIIIIIII 14.31 3 -IIIIIIIITI 10.41 4 -I/TITTTITIIIIIII/II 18.67 4 -IIIIIITITTIIII/ 14.52 FACTOR 1 9 -IIIIIIIIIIII 12.11 FACTOR 5 5 -IIIIII/TITITIIIII 16.66 6 -IIIIIIIII 8.87 6 -IIIIIIIIIIIIIII 15.20 -II/IIITIT 9.02 7 -IIIIIIIIIII 11.16 8 -IIIIIIIIIII 11.22 8 -IIII/IIIIII 10.88 9 -IIIIIIIIII 10.20 9 -ITU= 8.44 /0 3.34 in I-IIII 4.08 LEVEL I I I I...-. I LEVEL I I q ..I FREQUENCY DISTRIBUTION OF GREY-LEVELS IN,M&P PERCENT= 0 10 20 3n . 40 LEVEL I I I 'I .. 1 1 -I 1.30 2 -IIIIIIII 7.94 mAP 3 -ITITTITTITITI 12.98 FREQUENCY DISTRIBUTION OF GREY-LEVELS IN 4 -III/IIIIIIIIIIII 15.98 9 -IIIIIIIIIIIIII PERCENT= I 1 2 3 4P 14.26 I I FACTOR 2 6 -/IT/IIIIIIIII 12.70 LEVEL I I 7 -MIMI= 11.90 1 -TI 1.73 8 -IIIIIIIIIIII/, 12.8? 2 -IIIIIII 7.45 9 - IIIIII 3 -IIIIIIITTTI 10.75 7.66 4 -IIIITITTIITTI 13.26 • 10 -I II •T 2.87 5 -IIIIII/IIIIIITIIII 18.39 LEVEL I I 1 I FACTOR 6 6 -IIIIIIIIIIII/IIIIIII 20.3A 7 -IIIIIIIIIIIIIIII 15.8? 'I -IIIIIIII 7.97 FREQUENCY DISTRIBUTION OF GREY-LEVELS IN MAP 9 -IIII 3.92 10 -I .74 PERCENT= 0 10 20 30 40 I I I I LEVEL I I I 'I I LEVEL I 1 - I 1.11 2 -HMI . - 6.62 3 -IIIIIII/II 9.56 4 -IIIIIIIIIIIII 13.07 FACTOR 3 5 -IITITIIIIIIIIIIII 17.00 6 -IIIIIITTIIII/III 16.35 7 -Hu-III:m/1m 14.80 A -11111111111 11.50 9 -ITIIIIII 8.44 FREQUENCY DISTRIBUTION OF GREY-LEVELS IN MAP 10 -II/ ' 2.53 LEVEL 1 I I. 'I 1 PERCENT= 0 10 20 30 40 LEVEL I I I 'T I 1 -II FREQUENCY DISTRIBUTION OF GREY-LEVELS IN MAP 2 -IIIITITIT 3 -III-III:ITT/I PERCENT= 0 10 20 30 40 4 -IIIIIIIIIIIIIII +2''.5.7 LEVEL I I 1 'I I 5 -IITIIIIIIIIIIII 0.00 FACTOR 7 6 -IIIIIIIIIIIIIIIII I-2 -III 2.60 7 -IIIIIIIIIIIIII iiiii 3 -ITIIIIIIIIIIII 14.:'R 1 -IIIII IIIIIII 4 -TTTTTIIIIIIIIIIIIIIIIT 22.00 9 -ITIII 14.712 9 -IIII/IIIIIIIIIIII/I 16.04 10 - .43 FACTOR 4 6 -IIIIIIII/IIIIIII ' 15.61 LEVEL I I I I 1 -IIIIIIIT/II 11.2'; A -IIIIIIIII 9.05 9 -IIIIII 5.78 10 - .49 LEVEL I I T .1 I Fig. 6;2. Frequency distribution of grey-scale levels in maps shown in Figs. 6.3 to 6.7. MINER-WALES*FROJFCT94* FACTOR SCORE (LOG) PERCENTILE MAP * • FACTOR]. OLOW-PASS FILTER USING EFFECTIVE RADIUS CF 1. CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I FACTOR LOADINGS ++.4. 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This association is reflecting detrital accumulation of heavy minerals, as ilmenite and chromite, in arenaceous sediments of the Old Red Sandstone, and the presence of basic igneous rocks (andesite, diorite, dolerite and basalt) in the Ordovician sequence. 6.4.4 Factor 4 Sn Association A single association with a loading of 0.96 on tin is extracted. Armour-Brown (1971) and Celenk (1971), have also found similar single association in geochemical data of Zambia and Turkey. The reason 'that tin stands so strongly as an individual factor is probably due to the limitation of the analytical technique used (spectrographic in all cases), and the high sampling error found for this element (Lowenstein and Howarth, 1971), due perhaps to uneven distribution of cassiterite in streams. The spatial distribution of factor 4 is given in Fig. 6.6, and is identical to the distribution given in Figs. 5.25 and 5.26 (see Sec. 5.2.13). 6.4.5 Factor 5 Mn - Fe - Zn - Co Association Manganese and iron are associated with loadings of 0.8 and 0.6 respectively, with a somewhat lower loading of 0.5 and 0.3 for zinc and cobalt respectively. The spatial distribution of R-scores for this association given in Fig. 6.7 shows a distinctive concentration of high R-score values over mountain ▪ MINEX-WALES*PROJECT94* FACTOR SCORE (LOG) PERCENTILE MAP * FACTOR3 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++T I I I NE*E I I FACTOR LOADINGS lipf REEF I I t.B=RPEFC ERB EFE =F I I Cr o.8 B ===flf en EfRE BEB n PT 1 RB === 1,1 F MRR mentions BE • F RR on I 1 Ti 0.7 Efq===-= _== ==.4u=11 == MODOBOD4 E===g== DI I EE =--+===== ++++- - nosnonnnon c-- FACTOR SCORES =-ie =+---== -+++ +-==--== eeennonnnone =RFP!I ,I .=le 01-4,1-:Jf --II . P==-=== Feennonnunenoe ri,eeRR fi <-o.8 ---EM 4 RR rif ffenensennn enonaceRfoi m . B AA.• BR BRFCRBBBREERBEEFADODOVWIDDOOPEFFPI Toe Bp--=REBRrffgEILMIERREEPMORGOOMODOOOP. PODI 1 ' 1 -0.8 - -0.5 APP,E3?--9nRPFMgV/1‘e,fc!PPF.FMerlEflVtie,Pet)@@gS051"( fa. 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Pl==FFOADAARERRFRR: 19,,,,,::=,1 .v I +++---++-==--++ +4------= AFBRFOeR 77::,)::,: I mt--4-4-+-== =Em.-+++-BE PRcPf Eff PR'VW --= -3] I ==-++-==IBF RB -=Rf EFFIORAFEFERaRffR RRB=9"-::::::::' ===-1 I =44++ EB-PFREPIFFEFFFNEDFFFFIRRBER=-++11,..,=,p I I t'AIEEODF, ffEEFAPEBPFP1=10Bri-- yoe.?9,++'4 I I ANFREEEE ff - fkAeFfFPApAAFF=- fl, + := I I Eeg OtECF cae.,ea ER-4 :; I I EDE PPCPPt0A0A E(1== ---+- I I eceocnomonenon RR=- I I 00011080DOODARI== i I 0000M000(90 I I BOB000050061 I I BEIG00600000 I I I I 1 I++++++++++++++++++++++++++++++,44++++++++++++++++++++++++++++++++++++++++++I Fig. 6.5 • MINEX-WALES*PROJECT94* FACTOR SCORE CLOG) PERCENTILE MAP * FACTOR4 GLOW-PASS FILTER USING EFFECTIVE RADIUS CF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++T I 1 000 I I FACTOR LOADINGS A@WItItA I I ' Ongetlf "1 0 000 elE8 +=- I ' Sn o.9 00FEE-Ef00 0C4A 01E1 --=I I1 ' 0400N:3E00110W ERBN=-= COIEE ER ++ I I - 0000tl)gEF001000 91:1f f BE B-==--L 01BrIt-._=4,-= mmaI 1 - FACTOR SCORES otoopr.logone =9,Erl Bp 89EB1 == -- ==F ,98R_-+=9F eal I ' 000000001009--19 EREER-===---R fEEFR9=-=E0000I I • <-1.7 notalamelmr=::mmgR=191------EffInf 0===fgOO 4I - I -==-=-==88f MOPR8 eneei I - , -1.7 - -1.5 taitineRRN.,---= R 1 =-=E9==e00e1REEFF 00I I romoF -- 988 =p_emnF =EFt-)00I I + -1.5 - 0.1 gef30mFB -1.4.4.--===.4.-====EFF8 _-++= .0E--===FF@I • I 1 - 0.1 - 0.3 Olgr9147f::!-+-- 8888BERUIVI:+-=Eri:I::"Ti 1 t000ePEB REE=--==. 28EBEBBRE99 =-+++==f1c 1 • 1' 0.3 - 0.4 Bpoule R E E==RffB9BEEBEffrIBB9=-+-=FF I 1 R= Cp00800 9 EE===I - FEEEEREE 9R9P-=-=9 00000 I D 044 - 0.5 E9-=1 ft 00C4 FEERP1tFF9BFEBRE. R199ERFF000000000 CIp--= E0 BBB 889 RfFEIEFR9889BREPPP,A0P0000M0 I £ 0.5 - 0.6 0og BE BR BBB Ff8 ==l8BEIRR-=9Pfl 00000M0@ E = 0 (3 91 6 ===aEff5==f eeccgeomnneo 1 0 0.6- 0.7 rit, o BB 9E9 F ---88P==9E EEFg0M000009 I EREEf9REF tr-Tk-===BOP= nrifeeeoeume 1 ® 0.7 - 1.2 PO7p eFil2c- P Ogesg0 1 0000CE @OGOCEREE9B999==+-= NEEE,01 I li >1.2 tOnSeeeenelEERBPREER PEP .9-qLEI I 09g£ 00017EEEEEIFIgEE91R9BEE =--- 9999BEERI EEEE 00eFFEREEEEREFEEER8R88 =---= 9998-0 I ERE 000@FF 9=9RP1BREER====+-++--=== E I I gF@@440406f==-====-====-=--+++++ ---- =17=-1 ttlieee e cle=-++ ------=-+41,991 • I @OM@ ,12_,E8P 9-----+--==---==-= 0000 BtM On ---+++-== ----- =-+ +---+++„,' I 0000pFFFMR=+--++--===++--=-+++-++ tY +T-1 I 0@opemo0FFFp ++++++++”•4...... •+.1.4.114.4-1-1.ft 4.-•I 00000009EFF9-++---+++---+----++N++++ ++-i I e9mp000OF88p--++---++++++----++++++++,F+++Ifl 00000f4P0F,•8R +++++-+---+-+++++---++++'+4+W I e egteeeee9,-==-+++++++--==n + +4-T 8 f eeoe,Fp , I ==EEPPP9- = =REPP---- 11 I ++-1FV)faE1- - -- ++ 'I +++=9REE1= ------=- I 4.+--==.98 ++--REB_ + -- + ==+ + T RBBR-- + ++-I I -18F=- e +++- - RERPRP 4-==--===-4.4.4.+I 9e1=9fr19--+-+---=--++++------= BFB98P=+ 4 =- + I EMI - ++ -+ +++ 9E38M=+-- 900BP-++ 4. ____ I ER9BEE9R9R=-+++ + +++ ;RV -- ++5,13prRR=4-4. A.+ +4.--=-I = 97E9999--= ++ - + ++7 0 n =-++-(999B9f5-+51+++++-===== ++'++-=i • / = = 9s1R9 -===--+---+ -+++-:-...E000E -++++------++T++++1------+-===-I =Bn =9981= +++ pEpt 9 I = BBBP-1911E1B BP +++=fpf19 ----- == 99 I ===ABBR199 -+++=Raff BREBRELaI =----4.--==-----1+=9E9-00PF.B -++ ttf, ++++++++--Rfr 9P ERFIFI ..71 1 9999FIR9 ------+---+=E--:F0000eEE +.'"4" ,,,,+---+--- F.-- - ..trEEFE4I. BfEfEEEEE9 ==-===918=-+++++=PoppFEB -==4-'9,1 4.--4.4.---0.==--++++-=919 I -=EER ,,,9 4.--4.4. _.- ++++*8 J. I EREEFFP ___ +-- EF f.10e 0,EP ++----aPfEEE99 ----+'WV,, ++--,=_=--+-++++-==Bilq=i I 00EEE9Rn • 4-•■•■==-19ELIft:=7.Er 4" if,' +---3==+++++++-=='Egjgi 00 EB9B9= Fll=-==Ep=--==- 9 -++++++-'9FE=9 91 I 0 E£ ==-=BEBB=nEr.--... -++=a-++---+-828-98 I +*+++-= PP- ...tg- +-=---1RE=E I I +--+++-= -=== ---- == -- ==...... ===_"__".7-E:- n I I +*+ ..,=7 4. ---++ +++== I I R=---++---++ + ++++- I I £=-++++++++ I I +++++++----+ I I ++++++++-+ I I ++4.-4.-4. I I ++4.-4.-4. I I I I I I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++1 • Fig. 6.6 148. areas, dissected plateaux (Cambrian Mountains), and hills cored by Lower Paleozoic rocks. Similar concentrations are found in patterns over the dissected plateaux of the coalfields (Carboniferous, Culm and Coal Measures). The highest values are found over Snowdonia and the Drygarn Fawr (waterheads of the river Wye). Smaller high patterns are also found over the Lower Devonian (Downton), and over Carboniferous and Liassic rocks in Monmouthshire, this last pattern it is not known precicisely what it is due to. This association is undoubtedly a reflection of the secondary environmental feature, already discussed in Section 5.5.3. 6.4.6 Factor 6 Cu Pb - Zn - Ba Association Copper and lead are strongly associated with high negative loadings of 0.7, zinc and barium have a lower negative loading of 0.3. The spatial distribution of the R-score values of this association given in Fig. .8 shows surprisingly, most of the high patterns (Low concentrations), over large portions of the Ordovician and Silurian, but comparing these patterns with the base-metal mining sites map (Fig. 3.1), they are located over areas barren of known deposits. Similar patterns occur over Devonian, Triassic and Liassic reflecting the association of low concentration of these four elements. Patterns of Low R-score values (high concentration of the elements forming the association), are located over known mining districts and over Carboniferous rocks of the Culm and Coal Measures. Some low patterns are also located over areas of possible mineralization, MINEX-WALES*PROJECT94* FACTOR SCORE (LOG) PERCENTILE MAP * :, FACTORS OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ I I EF.F. FACTOR LOADINGS PtliFIFF IltIFfleFF:774 *If 91++ ++19 Mn 0.8 ,g00 0, == I'M -- +99: CE,la E= 'eel: ==-==1= 99,41 =LT • Fe 0.6 -aOFEER= PRB= LB BBP==--P-- 99 '9/ 99•911.1.2"a 9999 I., Zn 0.5 =RFRE8=- + 79,, EPERR9==+++===-- co i I 0.3 +----R-- 7++ =- EP:,Peoe QOPRRHFEET1===- 4.--==r1=-+ ,0480, +-- • I FACTOR SCORES - -,41A0MtinnEFFFEEFFt=-+ ++..•"=+++ 99: F 000001111000P40000019==-+ ++4 +++7.04,067; I • <-0.9 erg7InnnonummeeeeeTurlit+++ ...... "'=++ eoemo.: I nErnmannactimInfilaneofef@FP-4---= P91a++.•'=”4- 9111.61,7: I -0.9 - -0.6 ECF.ICTMOOE0110q0D2090gFFEEFP=--= 9EFPR=•='14- 777767; rgegeotmuonomwrionnonegfEeP==--= P R E„9.=...=...+9 9 9 9 9 • : I- + -0.9 - -0.4 ilgene-ecne(1911E2HuuunclogeRREPJ11=,+•••==■=1L 5===■,.. o p p , • .; •x 1:::::::::::::::1--- f, - -0.4 - -0.2 +.---=F (111E04F EFOOF3060000000ePWA 6IFERR1-++++: I ++-===91- -q40011E1O@WICOOOPPOGEMOOOFF9-++++P+ •I = -0.2 - -0.1 +-4.==== mannoggnneoeonewleown-++++v+ I =--4-===- ennoopeetmeonoueounneewn+---+m+ I • B -0.1 - 0.03 4+ = 000n0000000000PflOOBERRN.7.1.--=+-+++ onneoecoo epootioD'crl + I 0.03- 0.3 OpoommoecceepooeP-+++----= 00000@e00e0gAnOORR=-++++-.+ 4.•+"'"4.1 I e 0.3 - 0.8 (4000ggMSDgFR=--+++-++++----+++++ 'I I: 09aPOPPPOePCOOOPRI%-...--++++++++--++ 9 9 I/ Y 9: ' e o.8 - 1.4 9JEPT4P000000000P FR=-+---++++++ 799,11 e9! Epplpeflee0P00000At4F - +++++ 99,9,7-1 >1.1+ FEflgP@P f40000gOOPR + 991,r: BEFP0 9,00MegeerIER---++-== • RBEPOO .',Of_af).gAEFI •+-++.■==== B8ReOrf. @g1FOFFNFFF= r=9B PQCOOMERFEF9OR I FEIL-BRE.F9PCOOPPMEZT!raER EBRE9RPC00000t4EFER I EFFRBEgC@OOOOPPEF9PER + + + -9QPI===1 EFEEE.410P00000OPPPe_yri === +--== ... =F3B17nr3 flEpoorpegooiltiongfffpr------BP£RER£. =9E400:EEnOORT1117:00EEEPRP RREERR9B7 RFaPt4ESFP0741c3NnOOFEBPRR FILEJBL7.-=REtnefigOOLI=POOPEFFERR -+++++-=IBEFEB==== I BERREle===RFEFf4P0090nCOMERRERPRR ------11671=--=1 BB999911F 0RTIEREEP.e00,9000e ===-= =P ==-+++-EfIREE FCP I -++ Mnyerlo.nrIfevmeeee -+++++ -PEREFtPR PFPBBR I -++- -.R-- ---BFEET9ejERP- 44; + (6p9====--= RRRC -4.4.4.--=-=,RFR=-+----=BREEFE9FEPR==-=epj=-- - -La I ---r-1- -RFRT51------IREBBREBR9===REIN==--= ==--+++--==T]====--=: I B EFR. -- -REEFR PREERRBE99-E-B=P----- =++++Ei++-=RBRN=---_ I ePa 'RRRBE9 1P. Rs EFEFERTIRRREPORRPRR - - -±FT+++,+++-===-+++-2 I PECFR = 9RERRPL Lle..---=EFFIIR===?RRTIRR= R====ETT--- +++--+,"±51±,, ++--+++-+ 3 I BE@FPaRrIN=-=ROP-17--=BRR=---==911BR JPRFR p==-4- ++,,.,79 ,9 ++++ 4..-= I 1£R=--+++ --spilm_====APP=--==9.98 F.g fRB ..•4.47,., I R=++++++--==v2=-4--pErn PARR ge000flA0.4 =.-1t9,9/67 " I fff=+1.--+++-+----+-=RERrigeRBRREFFR 000000Ae0OP REIn==•4-1,,, 9 4-”4- I ====--==-+--+++++-== RROEJR999Rf=FREFER 0000MeeFOOOFEEE9=--++,+--+++=== : -----++--====9REFF"eRFE -- oeneaeFfnuleFRE _ =.4. 4.41==...... = A RBI- =REM7MFFE)OFEFa eeee upaeqp _fpiq ---==qpprknE: +4 RRE= RET.1FFPP8RE+71eeeeP REREFFER =-= 9"FR===.7„:=1,3E +++++ BEE BE OeCOEFERFFFFRFEIFRRBB -=== I +.1-T;1+ 001FFERBFat„gt)eFFBEFP=--=3P=--=-= Qt9.0:101 PfflIPMP BEr'Big@CIfl 8913 in::::EiEFiiiitTe " 1 =9=B---===- 3 I -=--++++-++ -=e 3 -+ ++++ ] I -=- ] I 7,-,==...= I I +1--=R+E==+- 3 I 1 I++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.0 Fig. 6. 7 - MINER -WALES*PROJECT94* FACTOR SrCRE (LOG) PERCENTILE MAP FACTOR6 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS I+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++j I. I I + 99 1 / FACTOR LOADINGS 4.•+ el / - - + ".,14 ? Y •e+ 7 I Cu 0.7 9 Pt +4 + i, 4 4--) ===-== RREEER e*Iff=++ ++ ft W I 1 I Pb 0.7 --== 9R===EEERP ,,i+--- --+++---+,, Zn 0.3 99=-=911f9 E -v*--=== ----- ===+,... :::=7/CEPal 1I oc EBB 9P,Ful.r.E.------nEB -==Bp===-+„„+++--...RnEp--=a 1 Ba 0.3 e@ EB - P=17EIREEE99R== fEf===BB===-%7c , ++=-==EP+++1 I = = P===IRRI19 9== EEE BB====- ,,, + + + = P===I I FACTOR SCORES R=---=13BR----9BER = 9R99===, , 99 ++---=grTga7 I BB=--==t1==---=BP=BBE PEEBRE3+ 9 91 ---+RRBBEREfi I . <-1.0 en==++-=R9r3===P.f]t-41EEE OP.E.BB=- 99 -=--REFBEIRREI • I ' f==+=-=-=REEFEEFfro (4 •egFEBB-+ 9 60, ++-POt:EERBP) I - 1 -1.0 - -0.5 0(488----+-3ffte(1000e000P0eF,Prf.-+ l ess +=f3BE9E91 I .. . gO@CF====-=-==RaPP00000___ePAOPEP=-++s to . 2pae22112 I I . + -0.5 - -0.2 nflnOtlenE==g3=- =EPenOtlESP@PER=-++ R74gEERPRECI I @On0000PvE98R== -=aeCTTgOflgPOPORg===- -=90av, 98===BH - -0.2 - -0.07 E POODEID891181-+ -==:EgEffIgEOPOPP ERRR=---=B9fna,---,--- I EEE 0e0 0f-++- ==-PeFE0g.00geFfEEEB=-+--==r39==PPR*,: I = -0.07 - 0.09 F. FEE 3 --+_£B -+=fEtEaeafiaefR9BRR=-+7+-==PERBREFTP =199£EB-= B 0.09 - 0.2 ==-9F===g9 -++ 7!PlaW=1::2c1::%::7=NA1 I/ ==-++ J++1 BEB EEFEBEEP-4.1 I £ 0.2 - 0.3 +-+=--====lf. BBBFEEPR EEFFREEQ19-+ I ' --9.99139Pc4f=-= EEBBRE = REP === RLR I Q 0.3 - 0.5 ,- B FEBE9EPER= BEEEFEEP ++== -4-- BEBEEli J=BErn===,i-JEFEB=RREBBER===----+M++++--j I 0 0.5 - 0.8 BREFEEE==PBBRPEE===--+++Y+1-1 ,0-= EV00f4.7 BEFE999PEEB=PREFEPR _--+4+7;.-+-4== BEE I El >o.8 11FEBE9B RBEEBR4R==-+++, 17 + BRBER9BI REFZE FIRn P990PEP =---+1,9 -- RP,P=-==T • I -----=EP FEB E.PfEcE9==-+,,,++-= B---=T I ---=-==.0 prg lc,4PtI4ER9=-4, ++++-_- I I -++----R9f4ER-==r40110n, t4FP-+++ - --1 ---+++++=EF.C9===2c7,0nrinmeoci_+ ---+ ++--9ffErc0e8164[31300noeC=---.==---;:* -ft- +-=PFREER- FPP00000000 --====-=-===1 I EEB-+ +-9aFFF6t4 cn00nonetin=== BP-- J I gab 2= ++pP=12f6140fiieEEFEEE fER9R11,9====90.3 I 8 00e E=- REffEBEE 0 BREEERREEBBREEEEPR=RREIT I -Rf000e E====-FEFEEEER r JRBEERRR9REPERBP91.19) e8B8:2, BOse EFFRPEEPPPEEPEPRRREEE3===-==BRRRREPrIF-SJ I OPOFEF100aP EEEF4EFEEEFJETRTEE9BfqE291-).=--==r1pr.=-=_I E 000Pgt,P,Pnfi EE2n 2r9PEEE11.9eaERBRE3EPEEP=--===-++--=--I eee CEEe0000e ', fee PERrl£c.t:Enf £EM:-BRERC-9 FgE£...,P T,0-10--; fee cErneeeeFfnEtIo!, n9BR BB=-141RBRBBBEEEBPJ==--++++,,,,++-3 I BEFaLIGI# PEEEFEEE539F00061 600 EFRPER9=-=RBRERRR9,1,==--++++-+19 , 97 + a RBBEEEEEPfl EBRRPRBRP9F3OMOgE; FEE ff eT,=•== E19817l = ==••■••■•.++++++ 9911 1 , 9 1 I 00A EEIP929r1BgEg==-== 99==30e000A0 EEFEE.E1==99B9ER=--+----+---+++ ++11spa - EREEETIRR1== "RPE EEEF3 EEPPF1BRBRFFEIP=------++++ +1 • I EBBREERREERP=- P3Pg9E _FP1.1=--- REPRRR9R----B- ERIS..-1 I BH9q994:9-=-19n1=9--- - PRRRP-- PREREEEPRRREP9==-4.= BF PER=9BEEPE , E9 a I EiinoEncn==-===n==- REEEFEERP==IIRR==-- 9f2, PE=1ffaf=FP1==j9REE:4be4 I 9E99 - --(4q1== -R----- pc222r1=---====-+- con cff L:ccEgc , 00„, 7_,Frp71 I nt3 n ---+--= ++-A71000Rnil.10e/FP,E"E===qPrWLE;:if I =- - WIRB OBI = ++ ++ faetMOne P n FEF.-R171 I EEEE --- 1.44++ 9 9 • t + / BEF.f. geg +••1-+---;111P------=D j 4- I BEEr3q==--199P1=---1139i- .4 ++4++ t,,,, 799 += ==...= = - 9 BBERR-----==-+- + +++++ 7 • tII7IP-;71F4PPIC 9 +-==n I 9997 '999 4-••=n=nC1pUtpip.R2 I AEER -+++ y I •• • !It 9 9 • 9 9 ++4 9 9 I E1= 97,41.0./-+T+7, +++-„+--==5100gE9131 I ++411).•■+ 11 +++-+--+ +--=0;4ef193$1 a I 410,11,1140 +++++--++,++=-Qp2,3e).-i-,- 1 I eitet,9911 ++■++”4- 11" +17 ++++++ + +-=RfEl---+ ++++++++, +++++ 9 +++51 9 f -;1++++++, 999,99 +P-+- 1 I ++If 99997 f 9 I •,,, ,,, ft, I 7991977777 I /9 9 II 9/ I goo*, I I I I I++++++++++++++++++++++++++++++*++++++++++++++++++++++++++++++++++++++++++++, Fig. 6.8 1 151. coinciding mainly with the anomalous patterns described in Sections 5.6.2 to 5.6.4 inclusive. This association could be considered as the one reflecting features due to base-metal mineralization. 6.4.7 Factor 7 Mo - Co Association Molybdenum strongly influences this association with a loading of 0.8; Cobalt is subordinated with a loading of 0.3. The spatial distribution for this association is given in Fig. 6.9 and shows patterns with high R-score values over Cambrian, Ordovician, parts of the Silurian, Carboniferous and over parts of the Triassic. The highest values are found over the Harlech Dome; the west of the Conway Valley, and over areas underlain by black shales of Ordovician age (Pembrokeshire). Similar R-score values are found over the Culm and Coal Measures, and over Devonian rocks in Monmouthshire. Some low values are located over known outcrops of black shales (Plynlymon and Tiwy anticline). This association reflects to some extent argillaceous rocks rich in organic matter. 6.5 R-SCORE ASSOCIATIONS IN THE REGIONAL GEOLOGICAL STRATIGRAPHIC UNITS R-score factor analysis has been applied to each data set comprising the different geological stratigraphic units. Associations with fourteen and sixteen elements were investigated, the results on the former association are considered in order to correlate them with the associations obtained with the reconnaissance data, and results with the MINEX-WALES*PROJECT94* FACTOR SLOPE (LOG) PERCENTILE MAP * FACTOR7 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I++++++++++++++++++++++++++++++*++++++++++++++++++++++++++++++++++++++++++++ I I £ I FACTOR LOADINGS = BB PCP I Bk.BFEf4 F Mo 0.8 I ''11 7 61 0.■.....1.= =.■...4- ... BB I Co 0.3 4.-==== -4-4-4++ PREi--- --1.--C-=--+RE +A- IF,PIL-a I + +1;9- ++= CPOOPf + - 4- -PE - --71TERP -41--=paerae000 FACTOR SCORES f =++ + +----= F n=+== nn eE =--- +,- BERBE -=---4--= F. Ea100en-++++++--=Eff9=-=n0Erl==-=*--7-fEcE --- Es,f oppn-++++++--=11 r.r1 PPER=::;:,=4.rg <-0.8 F MBE 00CF = _ -np rl =fq0NE9 I -0.8 - -0.3 ,RRBEE EMPFTIRERsaa-a--=‘",00n9PeMeeF==-=fRfEF 2 fie EffREE f-lef9F9EARR9===REEPlooempEr.--n,T4moe 389 RP=90rIRRRE legp9pq-400t ▪ -0.3 - -0.08 E f9EfgPPfEE9917 EEE9B9EafgejEP 99ePeRBRBREFFPEB-+=E E99 I - -0.08 0.06 991399PFEEBEef9 9E9999 9fffeE9===FEP= I. ERB9BEPBEE9RBEnE PE- PP9P==-=felf,E9f9f.gFPFP = 0.06 0.1 E00WEBB999fEERREfERRAPCf= --- ===-PBB=--=feE)fffff4of-4,=‘0 ,t4PAPPWEE, ,ER99EBEEEEFEE9=C4 n=--==-== = - ++-pff7eper tz)()e.e. ': I 6 0.1 Ffff,00P BM:, Pg9,f6a 2----=--4.4. + - p.fepe eeeeeera 0.3 =E--19EfAM P000Atif400f--+--=-+++++ +-9fEieeneERII 0000e0000en = I £ 0.3 - o.4 +-=IEEE@@ --- ==-4,+++ + - BT;elee ,B99P ;1- 0 000gElPflP 1)==--==------=-=n1 OPtEPMTT- 112 I o o.4 - 0.6 OgOeEEE9R- - 9 fEefERP=------0A09999=--++- B FE S,RBP12:-==--+ I • 0.6 - 0.8 EEEBBR= - +,,,--- BE EEBBEEB6==--+ B == --- ++,70----= BUIEE,E 099rIfFPFEE=== I >0.8 ==== --+++99,+-+ --=qpRRppin tippEEE 2=== --azi 77779 4." 11 I L.F-+,,,,,++4---E9 F3,E=--=11 =9P 9F,E=--======.-.411. 19171,,++ --12- BEBBB:1 - PB, RqRE I 4 "..=-. 797,9,9+++ -- - -- 99et;ERFPLI +++-==---4-0,,++++--4+--+++=99EqpBPPEEEEi; ip I ++ -11F,FEI -4--)7 , , 9 4-4-4-4-4-4-4-4.4-4- -=Rcff..-===arlps 779 4..===- f9fIff++++,7,77977 +-FIFE f=-+-1EE I 4-,,,,+■■■++1,84,0-4 ffs•aPP -- -=9EF=`9£F T 4- 997,9"" ef7,-= 4- 1....,,--==9Efan=9PEP I P,,,, ,,,, --+ 7 +-==RBEEEEP 99 4...... P4- 299+".4. 7o1D000+''==9FERPEEFn I ef==-4.7 7 1PRIle ',41+++ '9. -+ - BBREBL,TiaE, 99 ...... -.... 4" +-=9 Ef4t4PeEE9 ER =4. -==m p3ooptlER ' I I+ =atlFil::::;gg4=- ++ == = Y9 I 4-[1914-..(2PE)==4-4- f ,4. 2:-;+1-4f:FPL4-1311+1;1POR PRRWE'.t--3,Fr9), =+4-41---====-4- /7 ...... 4-=0112--EpRj5=2--- F9Prin9fB9 9 I 15-17,-) + ...... 4-4 999 -B7.-+4--=_-=_--= ,F,9999==.7-11FTFI 5ig0 5- ___ --- ++++--+ YY,-Eff==-++++1)---+-= 9BP:)g139 I BEP=2--+4--2--4.-:-====--++ --=191.1 I PY/f9 -= BE ==- ++++ -==++-=r1F9rieq.-+-=L: 99RRB-+ 919 ..---====-===-4- ,,,,, 4--=99=0=-4.-++--=+++-=REER 2-4-4-4- I -... -- I ++-=99999n9 7 oo • a 7 7 ,I3Q---.•-••====4- 1199999 - 4.101..=P===- R -+ I -4,44.-=EE9=9 • 817-=---=EP== R C • • a 7 4-=...-,114-4-4- fPf + -- "4- ii++:: r4Aidr- 251.= += r3_ = rippp 4-, + • I 00E9P9===999== 9 94 900,7+4 +114 9 7,, I , , 4- 9f,E 99745, OPEPBE99 =-9==9E 4--'4-,••,,,,,, -T --=REARPOT= ,..,+9EffEc .9e£, -EBEREEBP=REP. ED.;-1- 1",6,,T ---+++- +++-+ -plEBRPOOPi+ oe, FP.periesFBR 9991:9PROaP EE91- 0++ RESP OOQIE S= • tl -lpee00000tnn -=RclaP20000P EBB 9011c19 ---= R==-4. pc.000001:4F -=--1.,:R*eennoplEE If.E 42 1000 FR --=B9R 11 = oeounnoof:-=--„ =lp-flaeneeea(IR 9Et73t.m B=m11B9 GPPEEE=== 9M-- B oogeononnorIR=.7, n9n90Bi',FE1-11 f3! = 11.1000t4 0e---EEF99::Elar 0004Fa00000@f9=2====--=P-==pB8pp,E -==99999 000 EE9E9c,9PF4 nr30000@ Ef30000PiTEEEP,99------= B99131tEIBE00 BE tmeroneetfpip,Ei-,:?.e.t;f4eP.EPP,PPF9=-4-++-=---=- 7=,1998E 000000800ffPEEEERFaenelgEFIR--++++---++ 090P,000 frEfr47f990efif3c:f.f.(219.tg- 99 , , • 9 80t00000 EF4tonelEfrleemuf3f9 Yl 9,0 I elm f Cceeee£ErPC R c1 ==.1++-,, 00*EfgEF000%::::-= -2 I 0001BPPREee00eF0fR +++=p I 7 9 fl + I •• • f 7 9 9 f f•• I I I I++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++t+t Fig. 6.9 153. latter are used to determine the geochemical association related to base-metal mineralization. 6.5.1 Associations with Fourteen Elements The procedure of analysis for each set is identical to one described in sec. 6.3. Table 6.4 illustrates the selected factor models (associations) for each set of fourteen elements, the models were obtained using the same criteria and method as the one employed for the regional reconnaissance data. The associations found, in a broad sense, are similar to those extracted from the regional analysis (column 1, Table 6.4), and therefore, their controlling features are considered to be similar, but different in detail. Association with Ga - V - Ni — Co - Fe - Mn as dominant factor loadings, are a reflection of the argillaceous facies within the unit. Associations with Mn - Fe as dominant factor loadings, reflect secondary environmental features but, are not well defined, except in the Pre-Cambrian data and possibly Ordovician and Carboniferous data. Associations with Cu - Pb - Zn - Ba - Fe as dominant factor loadings are a reflection of possible mineralization and contamination from past mining activities. Sn as a single association in most of the sets is a reflection of the features and factors controlling the same association in the regional data. Associations with Mo as a strong factor loading, are regarded as controlled by organic matter in argillaceous sediments. Table 6.4. Selected associations with fourteen elements of regional and selected sets of data DEVONIAN DEVONIAN SILURIAN CARBONIFEROUS AREA REGIONAL PRE-CAMBRIAN CAMBRIAN ORDOVICIAN (DITTON) (DOWNTON) • POPULATION 9910 124 126 201 382 200 (-ea) 185(-Ba) 261 FACTOR MODEL Factors 7 % 8 5 % 5 % 8 Selected 7 % 6 7 total % data correlation 81.6 87.5 86.9 90.4 86.0 86.1 84.7 89.2 accounted for Factors Ga.8 Cu.8 Fe.8 Ga.9 Co.8 V.8 Fe.8 NI.8 N1.8 V.9 Ga.8 Fe.8 Cu.9 N1. NI.8 44.3 Co.7 38.1 Co.7 37.9 Co.7 . 1 43.5 . Mn.7 42.4 Ni.9 53.3 Ga.89 51.4 V.7 45.7 Co.7 Ga.7 Ba.4 Ga.6 Co.8 Pb.8 Ba.6 N1.6 Ni.5 Pb.8 Fe.4 Fc.; V.4 Ga.; Co.4 Pn.5 PA.3 V.7 Cu.3 Cr.6 Fe.3 V.8 7I.8 71.8 Cr.9 11.9 Ba.8 T1.8 Cr.8 Cr.8 V.8 Zn.8 Mn.9 Pb.8 2 Ba.6 Fe.6 12.0 Cr.7 26.0 V.8 21.6 V.8 19.0 Ga.8 16.8 Mn.7 19.1 Cr.8 21.4 16.6 • Zn.3 Ga.4 Ga.7 Ga.4 T1.6 Cu.7 Cu.4 N1.3 • Mn.3 N1.3 N1.5 Co.4 . Cu.3 2n.3 Cu.9 Mn.8 11.9 Ba.7 Fe.6 Mn.9 Cr.8 Pb.8 Cu.8 Cu.8 • Sn.9 108 10.0 Fe.6 12.9 10.1 12.2 Cr.5 13.2 11.7 Co.4 T1.7 Mo. 5 Pb.6 Pb.8 Zn.3 9.8 3 Zn.4 Ga.3 Mn.4 NI.3 Fe.3 V.3 V.3 Mn.9 Cu.8 Co.8 Pb.7 Mo.9 Fe.8 Sn.9 9.0 V.3 8.4 Zu.5 8.4 7.5 4 Sn.9 10.1 Fe.3 9.6 Fe.5 8.8 Sn.9 8.6 Zn.9 Fe.3 Ba.3 NI.3 Fe-.3 Cu.4 Mo.8 Co.7 Mn.8 Zn.9 NI.7 Fe.6 Ba.8 7.9 Sn.9 6.0 Mo.9 7.0 6.6 5 8.4 Sn.9 8.5 Fe.6 7.9 Zn.9 5.6 N1.3 Fe.5 Zn.5 Pb.3 Cu.4 Co.3 Ga.; Cu.7 Cu.7 Sn.9 1 Pb.7 Mo.9 .4 Ba.8 4.8 6.6 Zn.9 5.7 6 8.2 Pb.6 7.8 Co.C4 TI.3 Zn.3 Zn.4 Ba.; Mo.8 Cr.8 4.3 Mo.8 6.2 Sn.8 4.7 Mo.9 4.6 111.3 5.2 V.3 7 Co.3 Ti-.3 Cu.; Mn.8 71.8 3. 9 3.8 8 Co.3 Fc-.3 155. 6.5.2 Associations with sixteen elements Selected factors models from the factor analysis applied to the sixteen elements were investigated in the regional stratigraphic units and are shown in Table 6.5. The associations with high factor loadings of Cu - Pb - Zn - Cd - As - Ba - Fe are of great importance, as these represent the mineral assemblage of the predaninant ore types, especially those in the Southern Caledonides rocks of Wales (Chapter II). (i) Pre-Cambrian: Factor 6 with the association of copper, lead, zinc and cadmium and their factor loadings of 0.7, 0.5, 0.5 and 0.4 respectively, represent 6.6% of the total variation in the Pre-Cambrian data, and are mainly a reflection of the high rock background of the Bedded Series. During fieldwork in Anglesey, thin pyritic veins were observed in rocks of this series. (ii) Cambrian: Two factors representing 47.7% of the total variation of the Cambrian data, reveal two different mineral assemblage. Factor 1 with copper, lead, iron, nickel and their factor loadings of 0.7, 0.7, 0.5 and 0.3 respectively, reflect the mineral assemblage of the sulphide mineralization of the deposits forming the Dolgellau Gold Belt. Although no nickel minerals is recorded in the area, 1 56. TABLE 6.5. Selected associations with sixteen elements of selected sets of data. DEVONIAN DEVONIAN . CARBONIFEROUS AREA PRE-CAMBRIAN CAMBRIAN ORDOVICIAN SILURIAN (DITT0N) (DOWNTON) POPULATION 124 126 201 382 200(-Ba) l85(-Ba) 261 FACTOR MODEL Factor 7 8 8 7 6 9 Selected 82.3 86.7 86.5 84.4 88.2 83.2 88.5 Ga.9 Factors Co.8 Fe.8 Co.8 V .9 Fe.8 Co.7 Mn.7 Cu.9 Cu.7 Ni.9 Ga.7 NI.7 Fe.7 N1.9 TI.7 1 38.6 Pb.7 33.6 43.7 39.2 42.5 Ga.9 45.5 Mo.4 43.1 Ni.5 As.4 1,11.5 Pb.8 Pb.8 Fe.5 Mn.3 As.4 Co.8 Mn.5 Ni.3 Co.5 .3 V .3 Cd.4 ✓.7 Fe.4 ✓ Pb.3 . Ga.3 Cr.6 Fe.5 Cr.8 Cr.9 .8. 11.8 11.9 ✓ V .8 V .8 Mn.9 TI.8 Cr.8 Ga.8 Zn 8 Zn.9 19.2 Ti.819 .1 16.5 ' 18.9 tr.8 20.1 16.8 Cr.7 24.6 V.8 Ga.5 TI.6 Mn.7 Cd.3 2 8a.4 Ga.7 Cu.7 Ni.3 Nr.5 Co.4 • Ni.3 Cu.3 Ba.3 Cu.3 Cu.9 TI.9 Pb.8 Pb.8 Sn.8 Pb.8 Fe.6 Sn.8 Zn.9 14.1 Ba.4 9.7 Cu.7 11.4 Cr.5 11.6 Ba.0 9.5 3 Mo.5 8.6 Cd.8 11.7 Zn.5 Zn.4 Pb.3 Ba.3 Mn.5 Cu.6 Fe.3 ✓.3 Mn.9 Mo.9 Cu'8 8 3 Zn.9 9.2 V .3 7.1 As.9 8.7 Cr.8 7.6 Co.8 8.1 Sn.8 8.7 . Pb.6 Cd.6 As.3 Fe-.3 Mo.8 Fe.7 Mo.8 Ba.7 Zn. Zn.5 Sn.9 Ba.8 Fe.6 7.6 9 5.8 NI.3 7.3 As.9 6.7 7.5 5 Fe.3 7.2 Cd.3 Cd.4 Fe.3 6.2 Ga.3 TI-.3 Cu.4 V .3 Nt.7 Co.7 Mn.7 As.7 Mo.8 Pb.5 5.1 Sn.9 61 Sn.9 6.4 6.7 Co.8 5.2 6 6.6 As.9. 6.9 Ba.6 71.3 Cd.7 Zn.5 Cd.4 m Fe.4 Cd.4 mo.3 • Cu.3 V .8 Ga.8 Ba.5 Mn.9 As.7 7 Sn.9 6.3 5.9 Mo.9 4.3 5.6 Cd.9 4.0 Fe.4 4. 1 Co.3 Cd-.3 Cu.3 71.3 Cr.3 NI.8 Mn.7 Ba.8 Cd.8 4.6 4.0 8 Co.7 4.1 Cd.6 4.0 Ni.; Mn.4 Ba.4 Co.3 As.8 mo.5 Fe.4 3.5 9 Co.; NI.3 • 157. pyrite (major sulphide mineral), carries nickel as trace-element in various amounts (Gilbey, 1969; Mitchel, 1968). Factor 3 with the association of zinc and cadmium and their factor loadings of 0.9 and 0.8 respectively, possibly reflect the Pb/Zn mineralization in the eastern and northern flank of the Harlech Dome. (iii) Ordovician: Factor 4 with the association of copper and lead and their factor loadings of 0.8- and 0.6 respectively, represent 8.3% of the total variation of the Ordovician data and Factor 5 with the association of zinc and cadmium with their factor loading of 0.9 and 0.3 representing 5.8% of the total variation are a reflection of the associations found as background in the sequence of rocks that form this unit, and are not a reflection of mineralization. The groups forming the set were selected from unmineralized areas. (iv) Silurian: Identical associations are found in the Silurian data and the conclusions are the same as for the Ordovician set. (v) Devonian: Copper and lead are associated with elements (Ditton) forming the factor that reflects argillaceous rocks and are not related to mineralization. Zinc forms an association with manganese and probably reflects an 158. incipient association due to manganese oxide co-precipitation. Cadmium and arsenic are by themselves single associations. (vi) Devonian: Lead is well defined with the argillaceous (Downton) association. Copper forms part of two different associations with its strongest factor loading in the arenaceous factor. Zinc also shows two associations. Factor 5 with iron, zinc, cadmium and copper possibly represent some minor sulphide mineralization. (vii) Carboniferous: Factor 3 with the association of lead, barium, and copper and their factor loadings of 0.8, 0.6 and 0.6 respectively, represent- ing 9.5% of the total variation; and factor 2 with the association of zinc (0.9) and Cadmijm (0.3), representing 9.5% of the total variation; are both, a reflection of lithological background and are not related to mineralization. 6.6 SUMMARY AND CONCLUSIONS The application of R-mode principal component factor analysis has revealed seven factor models (associations), describing the element-association of the fourteeen elements used in the regional analysis, reducing by half the number of interpretations needed for the whole data. The spatial distribution of the R-scores have aided in the interpretation in terms of geology, mineralization, secondary environment and pollution. The main conclusions are summarised: 159. 1. The distribution of Ga - Ni - V - Co - Fe (Factor 1), exhibits the larger and evenly distributed patterns reflecting the environment of sedimentation of the argilla- ceous rocks (graptolic facies) of the Lower Paleozoic, and the environment (terrigenous sediments deposited in shallow waters) in the Carboniferous, excluding the Lime- stone Series. 2. The distribution of Ba - Fe - Zn (Factor 2) possibly reflects Pb/Zn mineralization in the Southern Caledonides metallogenic district. 3. The distribution of Cr - Ti (Factor 3) reflects detrital sediments (Old Red Sandstone), and the distribution of basic intrusive and extrusive igneous rocks. 4. The distribution of Sn (Factor 4), reflects acid igneous rocks and airbone pollution from tin-smelting works. 5. The distribution of Mn - Fe - Zn - Co (Factor 5) is clearly a reflection of areas where secondary environmental conditions prevailed. Horsnail (1968), and Khaleelee (1969) found this same factor in the stream-sediments of North Wales. 6. The distribution of Cu - Pb - Zn - Ba (Factor 6) largely reflects patterns due to contamination from past mining activities and partially to possibly unknown areas of mineralization. 7. The distribution Mo - Co (Factor 7) reflects the argillaceous rocks rich in organic matter. 160. 8. A comparison of factor analysis applied to the reconnaissance data as a whole and to the data sets of the regional stratigraphical units show to some extent similar associations. 9. An analysis of the Cu - Pb - Zn - Cd - As - Fe - Ba i associations in each stratigraphical unit reveals mainly the high background in trace-elements of the Pre-Cambrian, Lower Paleozoic and Carboniferous rocks. Associations resembling the mineral assemblage of sulphide ores are also found but, it is difficult to correlate them as the spatial distribution of the associations is unknown. S 161. CHAPTER VII COPPER, LEAD, ZINC AND TIN ANOMALIES IN NORTH PEMBROKESHIRE S 7.1 INTRODUCTION As described in Chapter V the reconnaissance stream-sediment survey of Wales has provided geochemical information that is difficult to interpret in areas where past mining, smelting and industrial activities have taken place. The metal patterns • derived from buried mineralization tend to be masked by the anomalously high concentrations resulting from contamination and pollution, and the discovery of new mineral deposits in former mining districts is possible but highly improbable. Based on this premise, examination of the anomalous regional geochemical variations was made under the assumption that the method suitable for interpretation and offering the best chance of exploration success, would be to make detailed studies of areas with lithological and structural controls, similar to the ones controlling the mineralization in the Southern Caledonides and Carboniferous limestones, and where regional metal variations could be found that were marginally higher than the background level of the surrounding area. These criteria were met in the areas of North Pembrokeshire and Newcastle Emlyn. The present chapter deals with the geochemical data of North Pembrokeshire which is of considerable • 162. geological interest, due to the similar geological setting as that found at the Harlech Dome and Snowdonia. The reconnaissance survey also revealed marginal anomalies of copper, lead, zinc and tin that probably reflect the presence of mineralization buried under the glacial overburden, with little oxidation of the sulphides. The geochemical data from Newcastle Emlyn is dealt in Chapter IX. 7.2 DESCRIPTION OF FIELD AREA 7.2.1 Location The area investigated is located in the County of Pembroke- shire (Nat. Grid. ref. 1700-2200 and 2200 to 2400), with a total surface covered of 800 sq. Kms. The locations of places mentioned in the text are shown in Fig. 7.1. 7.2.2 Geology and Mineralization The geology of the area has been partially described by different authors (i.e. Jones, 1940; Cox and others, 1930; and Evans, 1945). Pre-Cambrian igneous rocks have been brought to the surface by two anticlines (St. David's and Haycastle), the axes of which follow the regional strike of ENE to WSW (Fig. 7.1). The earliest Pre-Cambrian rocks are volcanic in origin, mainly siliceous tuffs, intruded by acid rocks varying from quartz- diorites to alaskite in composition. The Cambrian sediments are subdivided into lower Caerfai Series of conglomerates, sandstones and red shales; the Solve and Menevian Series of sandstones and flags; and the upper Lingula Flags. A number of laccolitic and sill-like intrusions are found within the Solve, Menevian and Lingula Flags, and are particularly prevalent within the Solve Series. These intrusions • 1 63. vary in texture and are classed as horblende-diorite-porphyrites. The significance of these intrusions is based on their similarity with the diorites (greenstones) of the Harlech Dome, with which the disseminated copper mineralization at Coed-y-Brennin is associated.. This similarity was noted by Wells (1925) who suggested that the hornblendic rocks of the Solve Series had certain mineralogical and textural affinities with those of the Harlech Dome district. Shales and sandy shales, with minor thicknesses of rhyolitic lavas and thin limestones, make up the Ordovician succession of the area. These rocks have been intruded by Dolerite-norite sills, and have been extensively folded and faulted, with evidence of thrust faulting, especially in the area of the Mynydd Prescelly. Silurian shales, mudstones and grits outcrop at the north-eastern border of the area, along Newport Bay. The area has been affected by Pleistocene glaciation through the action of the Irish Sea ice which impinged on the coast and moved across the whole area towards the south-east. A thin layer of boulder clay and gravel covers the Pembrokeshire coastal plateau. The only mineralized occurrences recorded in the area, are the copper mineralization of the Ramsey Head mine and the lead- copper mineralization at the St. Elvis mine. Ramsey Head copper mine is reported to be 21 miles south- west of St. David's and was a chalcopyrite-quartz occurrence (Murchison, 1839). St. Elvis lead-copper mine is reported to be four miles south-east of St. David's with galena as the predominant sulphide mineral with quartz as gangue (Lewis, 1967). • • a 120 1 . . N. PEMBROKESHIRE STRUMPLE HEAD DINAS HEAD Coregnuostod Pe Alluvial QUATERNARY Nevern Coal Measures CARBONIFEROUS 4 Pen & • Ltandovery SILURIAN Arer-do -Caradcc EgIwysturtu ORDOVICIAN Diorites-DoleriteS Pen Burch du Andesites CAMBRIAN Granites Yngs Doullyn PRE-CAMBRIAN Tufts-Ashes Jordonston Pen Clegur 0 Mathry 0 1 2 3 mile E* • - ay CI 1 2 3 4 5Km 23 Pen tier'', S' DAVID'S HEAD er.i.err•`.". L Ion eloy Boy • 0 g:,0j1;76' 4':"" , „,,y.rco—,c;J./ 7. ay 4. • .7 • - "5” , den Cosde , •sL. Llonycefn :<1 Bratudy • „ • re-7,V ▪ 1" • " ~` f. • Walton East rn y cuene, 6, Mt . •..• •.•• r .""n o • . • . w g II Mt • • Spittol • i‘Q‘9 : yoN° CO-Ce Clorbestan Comrose 1 65. No detailed studies are available of these two deposits, but they appear to be associated with the diorites that intrude Cambrian sediments during the Caledonian orogeny. The Llanfyrnach lead mining district is located only one mile to the east of the eastern boundary of the area under study. 7.2,3 Soils The area was surveyed by Rudeforth (Rothamsted, Soil Survey) but no official publication is available. The soils in the lowlands are classed by the author as Brown Earths with gleying, with a poor definition in their profile,and as peaty soils on the hillsides. The Brown Earths with gleying are brown-reddish to dark- brown mostly silt-loam, compact and with orange mottling. 7.3 GEOCHEMICAL DATA The geochemical data assessed were the multi-element analyses of the stream-sediment reconnaissance survey; and analyses of detailed soil, sediment, and rock samples. The results of analyses of soils collected on a kilometre grid pattern over the area to the west of Nat. Grid ref. 2000 E are also considered, and it is used as a comparison of regional distribution of the same elements in different sampled media (stream-sediments/soils). The analytical methods and sampling procedures have already been described in Chapter IV. All direct reading analyses were confirmed by spectrographic analyses before detailed investigation in the field. 166. 7.4 RECONNAISSANCE STREAM-SEDIMENT RESULTS The reconnaissance data covering the area was replotted on maps of 22 miles to one inch in order to obtain the location of anomalous dispersion trains. The results for the elements considered to be of mineral exploration interest are illustrated in Figures 7.2 to 7.6 and are based on computer line-printer plots produced with the PLTLP computer program. The areas which were considered to be anomalous and of sufficient geological interest to warrant more detailed investigation are outlined and numbered from I to VI on Fig. 7.7. These regions are individually described in the following sections. 7.4.1 Anomalous Area I - SOLVA Streams draining the area to the northeast of Solva are anomalous in copper (60 to 100 ppm), lead (100 to 300 ppm), zinc (200 to 400 ppm), arsenic (15 to 30 ppm) and molybdenum (3 to 5 ppm). The coincidence of copper and molybdenum although without anomalous levels of nickel, is of particular interest in view of the close proximity of the diorite-porphyry intrusions into the Solva Series within the structure formed by the St. David's anticline. Lead and zinc values can probably be'attributed to weak mineralization possibly similar to the St. Elvis-type and are clustered along the southern limb of the anticline. The displacement of the anomaly towards the south-east probably represents a smearing due to glacial action of the Irish Sea ice. • 1, .13 1g 20 11 0 7 2 t) 0 N- PEMBROKESHIRE oo . 0 0 0 s COPPER . o :q O 0 0 0 ill--v.... .111•46...... METAL CONTEN, OF MINUS 10-MESH FRACTION OF CO 0 0 0 STREAM SECII,ENT 0 00 00 ® o o o © >100 ppm 0 0 0 9 60 - 100 0 0 o 0 0 0 S 30 .. 60 00 0 0 0 0 s 0 00 0 0 0 0 0 0 20 - 30 00 0 0 00 O to _ 20 0 0 00 0 0 o • 0 0 0 0 OS 0 0 10 ® ® ® .. u 0 0 0 0 0 0 0 0 0 0 OS o o 0 0 • • 0 1 2 3 Tde>t ® O ..—_,.....----,. O s 0 0 o Q 00 0 1 2 3 4 5 Kns 0 s o e 23 O U U 0 O 0 .0 o s o ' o 0 eo o 0 s so o o 0 • 0 0 0 0 •oo s o o s oe 0 0 0 ® I e s e s o o o 0 0 0 o 0 e o 0 ® 0 o 9 0 o OS • @ ® 0 0 6) 00 0 0 0 0 0 O 0 (D 0 00 0 9 e o o 0 • o 0 • 00 0 0 0 s 0 OS 00 0 0 O .1N 0 s o e 0 o so 0 s 0 s o 0 0 o o O. Co ® o 0 o e e e 0 0 0 o D 0 ® 0 0 -k./ - 0 0 FIGURE 7.2 1E8. 7.4.2 Anomalous Area II - MAENCLOCHOG The Maenclochog area is located on the southern edge of the Mynnydd Prescelly, in a region of complex geology with dolerite sills,rhyolites, trachytes and tuffs within Ordovician shales, slates and grits. The structure of the area is also complex, with a faulted anticlinal structure and a series of thrust faults that were recognised by Evans (1945). Stream-sediments of the area are enriched in copper (up to 350 ppm), lead (50 to 400 ppm), zinc (200 to 300 ppm), nickel (70 to 150 ppm), arsenic (15 to 30 ppm), iron (6 to 87(;) and tin values (up to 100 ppm, compared with background values of 5 ppm). The association of nickel and copper is particularly interesting with the presence of fine-grained to gabbroid quartz-dolerite sills. The lead and zinc anomaly may be related to mineralization of galena veins, similar but, on a smaller scale than the Llanfyrnach mineralization located 7 miles east of the area. Streams in the Maenclochog area have their headwaters in the Mynydd Prescelly where rhyolites, trachytes and tuffs of the Sealyham Series are found; the high tin values in the stream- sediments probably have their origin in these rocks. Jenkins (1964), describes manganese oxides veinlets in rhyolites of Snowdonia carrying high concentrations of tin. Examination of the reconnaissance data for tin (Fig. 7.6) shows that two linear zones of high tin values in stream-sediments correspond to horizons in the Ordovician rocks where the Sealyham or Fishguard acid volcanics are present. • 0 1 19 2 2 2 'a • 0 0 NI- PEMBROKESHIRE 00 0 0 0 0 LEAD . 0 24 0 META: CCN'ENT OF MINUS LO-Mt OH FRACTION OF 0 0 0 0 STREAM SEDIMENT 0 00 SO 9 0 0 O 9 >300 ppm O 0 0 C:16 100 — 300 0 0 00 O 0 0 0 0 0 O 0o b 0 50 — 0 00 0 0 0 0 0 0 0 30 .. 50 0 0 00 00 0 0 20 — 30 0 0 00 0 0 0 0O 0 0 0 0 0 0—^f! 0 0 0 . U 0 0 0 0 0 0 0 00 0 0 0 O e 0 0 0 1 2 3 mots 0 0 -ne•••,,, 0 0 ® 0 0 0 • Vr.,1,==..¢-,,-_-rsrfre 0 0 0 0 • 0 00 0 1 2 3 4 5 Itrni. 0 0 2 3 Q--- -1:7-- 0 O 075-0 O 0 ® 0 of* o 0 oo e O , 0 0 0 0 0 0 0 0 0 00 o o 0 0 00 0 0 O 0 e 0 0 0 o * 0 o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ? 00 0 0 0 • 0 0 0 / 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0 0 00 0 0 0 0 00 IlD 0 0 0 0 00 0 0 00 g"%flrr k 0 0 0 ,--rC -(--A,s 0 0 0 0 0 o o o 00 o 0 • 0 0 0 0 0 \\.0 o 0 0 o 0 0 o 0 0 0 0 :2 • FIGURE 7.3 • • S a 1 17 19 19 20 0 21 0 22 o N. PEMBROKESHIRE oo 0 0 cp o o ZINC . 0 0 24 0 0 METAL CONTENT OF MMUS 10-MESH FRACTION OF -J-N-rv- ® o s o STREAM SEniNENT 0 . ® 0 0 0 0 00 00 0 0 • >400 ppm 0 o o 300 - 400 0 0 CO 3 0 0 0 0 0 000 0 @ 200 - 300 • @ @ 00 @ o 0 0 0 100 - 200 0 000 0 0 0 o • 0 0 0 50 - 100 0 0 0 0 CO • 0 0 o @ 0 0 - 50 @ 0 o .. • 0 0 0 0 0 0 0 00 0 0 0 . o • 0 0 0 0 0 1 2 3 •.1.. 0 0 — 0 0 0 0 00 V.,21^=r3SZZA=1798711 0 0 o . 0 0 0 0 0 1 2 3 4 5 /I rt S. 0 2 3 o 0 (5-- r) 0 O o 0 0 0 ® ® co • o o 0 oo o o 0 0 00 0 s O o o 0 0 oo 0 D 0 @ 00 s 0 0 0 o 0 O 0 0 0 o o 0 0 0 oo 0 o ® ® c o o o o 0 O 0 ® o - 00 o 0 o 0 0 O s 0o) o o o • • o O 0 ®° 0 e O ° 00 o 0 • 00 0 o O s - coo jszroi .'"—t iff'''.."— ,,,r 0 0 0 ° O co oc) Q O o 0 ® o O J - o O O 0 o ® ® O o 0 0 0 o o 22 o o 0 FIGURE 7.4 • 7 1g 10 20 o 2 2 N.. PEMBROKESHIRE 00 0 0 0 ...—....,..1• j 0 • ARSENIC 2 tv 0 —, — 0 /JCTAL CONTENT OF MINUS /0-14O54 FRACTION OF 0 0 • 1S-- STREAM SEOWENT 0 6 00 00 0 ® o > 30 ppm o 0 0 0 15 _ 30 0 • 00 0 • 0 0 • 0 s_ 15 00 0 0 0 0 0 0 se • o 4_ 8 0 0 00 el 0 0 0 0 o 0 _ 4 0 *0 0 00 ® 0 0 • 0 0 o 0 0 0 - • 0 0 0 0 0 0 0 0 0 00 0 0 • 0 0 0 0 0 1 2 3 mo.s 0 0 c- 0 =..-", 0 0 0 0 0 0 •0 0 0 0 0 0 1 2 3 4 5 nms ti • C7 • w 1.9 0 0 0 0 s o 0 0 0 .o • 0 00 0 0 0 0 o • 0 0 o 0 o• 00 0 • 0 0 0 0 o 0 0 0 0 o • • 0 0 0 0 0 • .5 0 0 0 0 0 00 0 0 0 o 0 0 0 0 0 0 00 0 0 0 0, 0 e 0 0 . • e 0 0 0 * • 0 0 r.„....,\o, e 0 o 0 0 '0 0 00 00 0 . 0 ' • Q 0 • •00 0 . 0 d 0 0 0 . 0 0 00 0 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 • o 0 V2 0 0 FIGURE 7.5 f • 2 2 17 13 1 2 2 N. PEMBROKESHIRE 2 . 0 TIN .111.10,.,.. METAL CONTENT Of MINUS 80- MESH FRACTION OF 0 0 0 0 STREAM SEDIMENT 00 0 00 0 0 o so ppm 0 0 0 0 30-50 0 0 o • 0 0 20- 30 00 0 • 0 0 0 0 15 - 20 0 • 00 000 • • 000 • 0 O 10 -15 O 0 • o 0 00 • 0000 • 0 0 0 to 0 o s-10 • 0 00 0 0 • 0 • o 5 . O 00 0 000 0 0 0 0 0 • • 0 0 0 0 • 0 1 2 3 mi., 0 0 0 0 ..-=,....pwarmi= 0 0 0 SYMIT=11.751,2=a117.1 0 0 0 e 0 0 0 1 2 3 4 5 It mi. • 00 2 00 O O 0 00 0 .5.j 0 0 0 0 0 o 0 0 0 0 0 • 0 0 0 0 00 0 0 0 0 0 0 00 0 • 0 0 0 o 0 0 0 0 0 0 0 0 0 • 0 0 0 0 0 oo 0 DO 0 • • , 0 • • 0 0 0 o 0 0 000 0 • 0 0 • 0 0 • 0 • 0 0 • 0 00 0 0 • 0 • O 0 0 0 00 0 0 0 0 O 0 0 0 0 00 • 0 0 0 • oo 0 0 0 0 0 o 0 0 0 0 o 0 0 0 00 0 00 0 0 0• 2 0 0 0 0 FIGURE 7.6 1- • • • • N. PEMB RO KE S H IR E [v······} Anomalous Areas ~ ...... : Main Rivers .lnd Streams ~Cu Know Mineralization ~A' Soil Traverse .A Rock Sample Site 174. 7.4.3 Anomalous Area III - CUM GWAUN The Cum Gwaum area is geologically similar to the Maen- clochoq region, except that the Fishguard rhyolites are present instead of the Sealyham.acid volcanics. The stream-sediments of the area are marginally anomalous for nickel (70 to 150 ppm), arsenic (15 to 30 ppm), and lead (50 to 300 ppm). Zinc values in these streams are strongly anomalous (up to 1600 ppm). 7.4.4 Anomalous Area IV - TRECWN A well defined anomaly in stream-sediments (100 to 200 ppm) copper is located near Trecwn, 21 miles south of Fishguard. Streams draining from the east carry sediments from Cambrian rocks (not shown in the geological map), and from Ordovician igneous rocks of the Fishguard Series. 7.4.5 Anomalous Area V - LLANFYRNACH WEST The lead (50 to 300 ppm) and zinc (200 to 400 ppm) stream anomaly on the eastern border of the area of study is probably a reflection of similar mineralization as that found in the Llanfyrnach mining district. It is superadjacent to Ordovician rocks. Unfortunately the structure of the area is not known. 7.4.6 Anomalous Area VI - HAYSCASTLE Streams draining the Hayscastle granite core of the anticline of the same name contained 240 ppm copper and 1300 ppm tin, with an adjacent sample of 130 ppm tin. This anomaly seemed the most favourable for the occurrence of cassiterite mineralization. • 175. 7.5 DETAILED FIELD INVESTIGATION OF THE ANOMALIES 7.5.1 Anomalous Area I Detailed investigation or the.anomalous values of copper, lead, zinc, arsenic and'molybdenum in the Solva area, took the form of an examination of available outcrop and rock sampling. During this study, disseminated chalcopyrite and pyrite was discovered at the contact between a small diorite intrusion and the enclosing Solva sediments, at Middle Mill quarry. Analysis of hand specimens of this mineralization gave 0.53% copper with 50 ppm silver (Table 7.1), while samples without visible chalcopyrite gave values of 40 and 400 ppm. Comparison of the average metal content of six diorite samples from Middle Mill with samples from the Coed-y-Brenin diorite (Harlech Dome, RTZ drillholes), indicates that the Pembrokeshire diorites are generally in the same range of abundance for copper, lead, zinc, nickel, chromium, silver and gallium; but the Harlech Dome samples are higher in moly- bdenum, cobalt and vanadium, and lower in manganese and tin. The Middle Mill diorite is considerably enriched in tin compared with the expected abundance in this type of rock of 1.5 ppm (Turekian and Wedepohl, 1961). Soil traverses were carried-out over and along known dioritic outcrops with limited results, as soils of the area are earth fillings used in the building of the Whitchurch airfield, and/or very immatured. 7.5.2 Anomalous Area II Detailed investigation of the Maenclochog area took the form of soil sampling traverses (K-i<' to R-R' for location see • Fig. 7.7), rock sampling and additional stream-sediment sampling. 176. Table 7.1 Spectrographic analysis of diorites from North Pembrokeshire and Dolgellau. Results in ppm unless otherwise specified. Middle Mill Diorite Coed-y-Brenin Diorite No. of 6 3 Samples Arithmetic Arithmetic Range Range mean mean Cu 700 40-3000 450 40-1000 Pb 20 6-85 14 2-30 Zn <200 <200 <200 <200 Mo <5 <5-10 11 <5-16 Ni 30 16-40 45 30-60 Fe% 9 3-17 Co 25 . 10-40 85 40-185 Cr 70 40-100 6o 30-100 Ag <0.2 <0.2 <0.2 <0.2-0.6 Mn 2000 1000-3000 400 400 Sn 40 6-60 <5 <5 V 120 50-200 260 200-300 Ga 30 20-60 4o 3o-5o • 177. Background values for copper in soil fall between 5 and 50 ppm, and exceed the 100 ppm threshold at three locations on traverses P-P', S-S' and R-R' accompanied by a slight increase in nickel and iron. While the initial anomalous sample on traverse S-S' gave 1000 ppm copper, detailed check sampling of this area with a grid pattern gave a broad zone of copper in soils without contrast with values of 100 to 150 ppm. It is unlikely that these zones are a reflection of copper or nickel sulphide mineralization of economic interest, but they could be related to the presence of disseminated pyrrhotite that has been observed at a number of places within the dolerite sills. Comparison of the average metal content of seven dolerite samples from Carn-Wen quarry (Table 7.4) with the results of eight dolerite samples from Snowdonia (Jenkins, 1964) indicates that the Pembrokeshire dolerites are more basic in character with a higher abundance of copper, chromium, cobalt, gallium and vanadium, and the Snowdonia samples are higher in manganese; with the same range of abundance for nickel, lead, tin, zinc and molybdenum. Lead soil values were found to be consistently less than 100 ppm, except in the case of a sample towards the north-east end of the traverse R-R' which gave 850 ppm (Fig. 7.9). As this area borders of the Llanfyrnach lead mining district, this lead anomalous value could be related to hydromorphic dispersion of similar mineralization as the above mentioned. Tin results from detailed stream-sediment and soil sampling of the Maenclochog area are shown in Fig. 7.11. Tin values up to Soil Traverse P P' ppm *1. 150 100 20 50 10 Cu A—A NI Fe 0 I I I 500 700 500 FIGURE 7.8 Soil Traverse U-U' 0 500 IOC° klem=r1==m■c=vroe=::1 00 I I I Ittg YARDS 1000 1300 6 00 ppm 96 Soil Traverse S-S' 1000_ • 100 50 0 0 I 11 • YARDS 500 1000 tm -.n=ragcl FIGURE 7.10 • • • • 4 FIGURE 7.10 181. 400 ppm were located in streams draining the Mynydd Prescelly, and concentration of tin appears to be related to the change of slope at the base of the hills. Unfortunately the soil sampling did not cover the potentially tin-rich rhyolites, and the highest value was found to be 30 ppm with a background between 5 and 10 ppm. 7.5.3 Anomalous Area III The two soil traverses crossing the area (I-1' and J-J') were designed to investigate the nickel-copper potential of the dolerites, but only background values were obtained. Copper values were in the range of 5 to 60 ppm and nickel values in the range of 10 to 40 ppm: Lead and zinc values also reflect background values without any sample above threhold of 150 ppm lead and 500 ppm zinc. 7.5.4 Anomalous Area IV Investigation of this anomaly in the field indicated that the copper enrichment of the stream-sediments was due to contamination of the drainage system by the effluent from a Naval ammunition factory. Soil traverses B-B' and C-C' border in this area and show that the topper content of the soils falls well below 100 ppm; the continuation of the soil traverse B-B' to the south demonstrates the build-up of copper in soils overlying dolerite sills. 7.5.5 Anomalous Area V The anomalous area of Llanfyrnach West was not studied in great detail, but the possibility of galena-sphalerite mineralization does exist under the cover of glacial till, which was found to contain up to 850 ppm on soil traverse R-R'(Fig.7.9). 1 83. 7.5.5 Anomalous Area VI Detailed sampling of stream-sediments and soils in this area failed to detect anomalous values for copper and tin (copper soil traverses E-E' to H-H'). Failure to confirm the original reconnaissance survey may be due to a numbering error during sample preparation, as the analytical results were • confirmed on the same sample spectrographic analysis before detailed field work. 7.6 COMPARISON OF REGIONAL SOIL AND STREAM SAMPLING The set of results of 152 analyses of topsoils samples, collected on a one kilometer grid pattern over an area of 400 sq. Kms, west of the Nat. Grid 2000E, were assessed and compared with the results of the reconnaissance stream-sediment • survey covering the same area. The regional soil sampling and analytical analysis were conducted by the Soil Survey of Great Britain, and the analytical technique used was semiquantitative X-Ray flurorescence. A comparison of the method used with USGS rock standards is given in Table 7.2. The spatial distribution of the sampled sites is illustrated by the map showing the distribution of copper in Fig. 7.12. • The procedure adopted was to divide the area into blocks of 100 sq. Kms. and calculate the basic statistical parameters and frequency distribution of all the elements in each, with untransformed and log 10 transformed data. The untransformed data was selected as the distribution of most of the elements tended towards a normal-Gaussain distribution. The arithmetic means of each element showed that all the elements with the exception of arsenic, gallium and zinc are slightly higher in the soils than in the stream-sediments, but • within the range of the latter. The noticeable difference lies • l7 l 8 lg 20 N. PEMBROKESHIRE . COPPER 24 C METAL CONTENT OF SOIL • 0 0 0 > 7o PpM 0 0 0 60 _ 70 0 o o 0 50 — 60 0 0 o o 0 0 0 o 0 40_ 50 0 30 — 40 c 0 0 0 0 0 0 o 20 — 30 0 0 0 0 0 0 o 0 _ 20 0 0 o 0 o 0 o • 0 0 0 0 0 0 0 0 o 1 2 3 miles . C 0 0 0 0 o 0 1 2 3 4 5 xm . 0 0 O• 0 0 0 o 0 0 0 0 o • 0 (3) 0 o ® 0 0 0 0 o 0 0 0 o 0 o 0 0 o o o O, 0 0 0 o 0 0 0 0 0 o e o 0 o . o 0 0 0 0 0 0 0 0 o 0 0 0 0 o 0 0 0 0 0 ® • 0 0 0 o 0 0 0 0 e 0 C 0 o . 0 0 0 0 0 o 0 o 22 . o 0 FIGURE 7.12 185. in the comparison of variances, the stream-sediment variance increase in a range of 10% up to 3000%. A comparison of the spatial distribution of the two sets of data is difficult although some high stream-sediments patterns are confirmed by the soils. • An R-mode factor analysis applied to these different sample media have extracted five associations in the soil data and four in the sediments data (Table 7.3) showing very few similarities and greater differences in the element- associations found. The only similar association is the one with manganese and iron as major loadings. 7.7 SUMMARY OF THE GEOCHEMISTRY OF STREAM-SEDIMENTS, ROCKS • AND SOILS A summary compiled from the element-associations formed by the R-mode factor scores and their spatial distribution shows that the trace-element content in the stream-sediments of North Pembrokeshire is basically a reflection of the lithology; possible lead/zinc and copper mineralization; and secondary environment factors. Streams draining dolerite-diorites rocks show a high concentration and correlation of two associations: Cr-Ni-Cu-V (Factor 1 - Fig. 7.13) and Ti-V-Ga with negative Co(Factor 3 - Fig. 7.15). The former association outlines the diorites of Ramsey Head and Solve in the west and the diorites-dolerites of Fishguard and the Mynydd Prescelly in the east. The latter association is sympathetic primarily with the diorites- dolerites in the east. • 186. Table 7.2 Comparison of semiauantitative XRF results, Soil Survey of Great Britain (3) for USGS standard rocks with means of published values:- (1) Flanagan, 1969; (2) Parker, 1969. Element G-2 GSP-1 AGV-1 PCC-1 DTS-1 .BCR-1 Cr (1) 9.0 13.2 12.9 3090 4230 16.3 (2) 6.2 10 21 19 (3) 19 21 21 2600 3600 35 Cu (1) 10.7 35.2 63.7 10.1+ 7.9 22.4 (2) 12 33 57 9 <5 15.5 (3) 19 42 70 12 10 20 Ga (1) 20.2 18.8 18.4 12.4 12.5 21.6 • (2) 32.5 18 27.5 <10 <10 34.5 (3) 26 28 17 7 24 Mn (1) 265 326 728 889 ' 963 1350 (2) 275 345 878 1229 1145 1770 (3) 270 270 700 900 930 1000 Ni (1) 6.4 10.7 17.3 2430 2330 15.0 (2) 4 8.5 14 13 (3) 10 13 23 2300 2300 15 Pb (1) 28.7 52.4 35.4 13.3 14.9 18.0 • (2) 31 48 41 <10 <10 14 (3) 35 51 44 13 20 16 Sn (1) 74.9 143 112 53 61 132 (2) 89 108 93 49 49 133 (3) . 93 102 86 35 42 102 Fe0% (1) , 2.76 4.3 6.80 8.53 8.85 13.50 23 (3) 3.6 4.2 7.0 9.7 9.3 9.8 • 187. Table 7.3 . Element associations, loadings and percentage Data correlations accounted for by each factor from-regional soil and stream-sediment data. S OILS STREAM-SEDIMENTS Element Loading 0/0 Element Loading Ga 0.9 .Cu 0.8 Fe 0.4 36.8 Ga 0.7 40.2 • Cr 0.4 Zn 0.6 Pb 0.5 Pb 0.8 Cr 0.9 Zn 0.7 21.3 Ni 0.9 28.7 Cu -0.9 Mn 0.9 Cr 0.4 16.1 Fe 0.5 17.4 Zn 0.4 Ni 0.7 As 0.9 Mn 0.7 Fe 0.4 13.6 Fe 0.5 14.4 Pb 0.4 Cr 0.5 Zn 0.3 As 0.9 11.5 Total % data 78.2 72.1 accounted for No. of samples 152 125 188. Possible buried mineralization is represented by two element-associations: Zn-Cd-Fe (Factor 2 - Fig. 7.14) and As-Pb-Cu (Factor 6 - Fig. 7.18). Factor 2 is a negative association, the higher metal content and positive correlations of which are shown by the higher negative factor scores grouped in the south-west and eastern border of the area in zones adjacent to known Pb/Cu and Pb/Zn/Ag mineralization. Factor 6 outlines with its high factor scores the Solva area in the west, part of the Mynydd Prescelly, a large region in the eastern boundary of the area, and an extensive zone south of Maenclochog. This latter pattern is partially influenced by secondary environment factors affecting arsenic which carries the higher loading of the association. The single element-association of Sn (Factor 4 - Fig. 7.16) is a reflection of the acid igneous suite and the spatial distribution of its factor scores is identical to the distribution of the single element map (Fig. 7.6). The association of Ba-Mo-Ga-Cu-V-Fe (Factor 5 - Fig.7.17) is sympathetic with shales, mudstones and grits (metasediments sequence). The association of Mn-Fe-Co-Ni-Cu (Factor 7 - Fig 7.19) is influenced by the secondary environment factors affecting areas of impeded drainage and/or excessive surface water. The trace-element content of the rocks (Table 7.4) follows in general the associations found in the stream-sediments factor analysis, and relatively high contents were found in: • s • • Table 7.4 Trace-element content in rocks from North Pembrokeshire. Results in ppm unless otherwise specified. SHALES DOLERITES (EAST) DIORITES-DOLERITES (WEST) ANDESITES (TREFFGARNE) Cu 40* 20-60+ 110 85-160 600 40-3000 4o 20-100 Pb 60 20-200 <2 <2-5 22 6-85 10 <2-30 Zn <200 <200-300 <200 <200-400 <200 <200 100 <200-200 Mo 8 <5-20 <5 <5 <5 <5-10 <5 <5 Ni 40 30-60 90 50-130 50 16-60 60 50-100 Fe(%) 6.0 4.3-8.0 26.0 15.0-30.0 8.3 3.0-17.0 12.0 4.0-23.0 Co 30 20-50 70 50-85 30 10-50 45 20-60 Cr 108 85-160 260 200-400 70 40-100 30 20-200 Ag <2 <2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 Mn 900 300-2000 1500 1000-2000 3500 1000->1% 1200 850-2000 Sn <5 <5 <5 <5 40 6-60 <5 <5 V 130 75-240 310 300-400 180 75-320 160 130-300 Ga 25 20-30 23 20-30 30 20-60 27 16-50 No. of samples 11 13 8 5 * : arithmetic means + : range 190. (i) Cu, Co, Cr, Ni, Fe and V (over basic rocks) ; (ii) Ga, Mo, (Pb), and V (over shales, mudstones, grits, etc.). Anomalously high concentrations occur locally in soils due to the possible presence of buried sulphide mineralization. Amongst the elements affected are Pb, Zn, (Cu), (As), Fe and • (Mo). Superimposed upon this distribution are the effects of pedogenesis, Cu, Pb, Zn, Sn, and Mo are enhanced in organic- rich soils due to specific metabolic processes of plant accumulation or to sorption. 7.8 ASSESSMENT OF MINERAL POTENTIAL ON THE BASIS OF GEOCHEMICAL DATA • To assess the economic potential of the area on the basis of the geochemical data, it is essential first to appraise the type and size of known mineral occurrences within the area and adjacent districts. Copper mineral occurrences have been found as fissure-filling vein-type deposits emplaced in pyritic shale beds and as disseminated and streaky mineralization in diorites and metasediments within their contact zone. Lead-zinc-silver and lead-copper mineral occurrences have been • found as crosscutting vein-type infilling mineralization on a north-south direction. These mineral occurrences are of limited size and tonnage. Amongst the mines of this area, the only records of output are from The Llanfyrnach mine, showing an annual average of 150 Tons of 17% lead with 10 ounces per Ton of silver. 191. The significant geochemical values found in stream- sediments and soils could be related to secondary dispersion from similar mineral deposits. Anomalous values of copper, coinciding with high factor scores of the As-Cu-Pb association, could be considered as a secondary dispersion of copper-lead • vein-type deposits of uneconomic viability. Significant copper values with high factor scores of the Cr-Ni-Cu-V association could be the reflection of disseminated copper mineralization in igneous rocks and their contact zones. By the size and intensity of the anomalies, especially in soils, the sources are relatively small in size. This assumption however could be misconstrued as the weak dispersions may • reflect larger mineralized bodies buried under the glacial overburden with little oxidation of the sulphide minerals. The significant values of lead and zinc associated with the high factor scores. of the Zn-Cd-Fe and As-Pb-Cu associations could be the reflection of lead-zinc-silver vein-type deposits of possible economic viability. Significant values of tin in the stream-sediment data may reflect a limited cassiterite mineralization in the acid igneous a suites. Anomalous values are probably due to a hydraulically induced accumulation of this mineral in the changes of slope at the base of the hills. Although interesting from an academic point of view, this accumulation has no economic significance. In future exploration programmes in the areas outlined by the geochemical anomalies, detailed geological mapping emphasising the structure, and the precise location of pyritic shale beds • 192. and igneous sill outcrops, will be of primary importance. Geochemical follow-up should be based on soil sampling along known anomalous areas with square grids of 30 metre centres, coupled with detailed examination of available outcrop. • • • • MINEX-WALES 'PROJECT 944- - NORTH PEMBROKESHIRE FACTOR SCORES - FACT )LOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++ ++++++++++++++++++++++++ 1 . I FACTOR LOADINGS I + 0 1I, Cr - ' / f 0 I 0.3 = C... _ / B . Ni 0.7 ,> 7 £1 1- • ' - i E. I : Cu 0.3 + £ , B £ I -- B £ V 0.33 . B = I : • + --• .. B= + + B ? *BB £ I : • . 9 ,- 0 ■...... --T.s. 1 ( 0 5 0 . N = . • ...-- 1 B I + . • ....--- Eli e 8 / ' , I 0 1 ++ + BEE) 0 I ..•' • + + /=- ,. ) t ° 0 I . , e'-'s, / 0/ • -■•■ i , '' I = , t a i t N •• L 8 , . s. i 0 / .0.-N 0 / 1 1 : — = I / = i B 1 / 0 i Nei / 1/ 0 t 'I I •- 1 1 e . , \ t C £ = 1... • l 1 -: -ft. ...• to i / / (1 : == - ... /0 1 • t - / I 01 I3 + - i ..- C 1 • B f3 - + `..--. / 0 \ = £ = -I C \II )+ 9 3 BB - N 4* e" — I fl ^'\ BB ,.• 0 150 0 •`s. £ 1 C B + + % •e . B ,..."- 1 + + C g \ r" I 0 0 1 N. I V.0 / C 1 + £ - ./° 0 ) 04 ( @ i I MJ o 1 El 0 a 1 , - I , 1 / / 1 ....-- 1 • ./ I C = I 0 1 - + El /+ = . ..--- -- ) ..., ...."' I I / t ++ I I 2 . E / 0 £ la = E - = f + • == B B ..■ e 1 / £ I - .,. . / == r . B 0 1 0 I I B e'N (51 0 /E, 1 BB I ■ "..... I I ■ • 1 E E C - - + `-/ - ■ / E 0 , f£ I = B - 1 + /". + 1 = I : I Et i 4- - = = 1 r ..... ++++++ ...... +++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++1 FIGURE '7.13 • MINEX-WALES *PROJECT 94* - NORTH PEMBROKESHIRE FACTOR SCORES - FACT 2 DLOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS [+++++++++++.41.441-+++++++++ +++++++++++++++++++.1-mtttt++++ .1-1-1-1-t+++t++++++++++++++++ +++++++++++1—+++++++++++++++++++++++4-I I I FACTOR LOADINGS .... . -- -..,,,., + . + I 1 00 3 -- , .I Zn -0.8 I 9 + 7 I . Cd -0.7 C £ £ - - I I _ =MID •■•• •••= •••■ .o. .1, ££ E - 2 % • I Fe -0.3 . / f•-• - B 1140 p \ 4. B / 74 I 7 IV, I e @ £ I • I ,. I ',I+ • \ I 0 + B £ t . k` , , \ - I C B OE £ 1- -.. -. . 1 I . • , ' C 00 0 £££ El . I I 0 B 0 0 El 1 \ I c B v i 1 , I E 9 0 £ 0 - / = I I :$ 0 0 0 II i — i. I I a F. 0 • • V 1 1 ., I I . 00 0 i — I EI .--. . +.. I B 0 \ 0 0 0 E. 0 I I 7 • I =+ I 1 : •--1.. 1 E.' 9 9 = \ 0 ....., 0 Iil 1 -- / 3 '.. - - i 3. I 9/ \ ...... 01 = B B 0 0 / = 0 II 9 1 + 1 B 0 N I .....— ,o, .... • ■.— 9/ = ) 9 0 •... y 4d / .. 00 .. E£0 0 \ = 9 \ - y + I 0 . „,.-.,, \ / 9 - = 0 E£0 I % ‘ I £ 0 / - 0 9 ) . = 0 / \ ....% I .-.... 1 I 4p = '''.'" I / == \ El_ 1 $ / + — e i/ ‘....1 — 1 + I — . + = B -- — 0 t + / = I C + 0 = / = / 0 1 ++ I ----• 0 9 / .0- l+ = / ++ I a 0 e a / - / ®/ 1 E i + + I C 0 0 0 - /- B i ++ ... ---- I B B 0 00 = I / I 9 9 — 1 8 B I r++4.++++++4144.++++++++++++++++++4444.++++++++++++++++++++++++++++++++++4+++++++++++++++++++++++++++++++++++++++++++++++++++++++++T FIGURE 7.14 a • • • MINEX-WALES *PROJECT 94* - NORTH PEMBROKESHIRE FACTOR SCORES - FACT 3 )LOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS .+++++++++++++++++++f+++++-++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++ ++++++++++++ ++++++++++++++++++++++++1 C I I _ - z FACTOR LOADINGS T : ∎■...."t4 1 - - C ++ - + = t 0I : Ti 0.8 ... ••'• ".% ‘ ••• 1 = B ""-I E V 0.7 ; 0 \ ,...... "' 0 ■ B £ I ..- E .. 0 / ,...,B I .1 = £ 13 I E Ga 0.5 ' . 13 , + / '1/ C 1 I = i 01F3B... £ I E Co -0.4 • - It 0 ' 3/ % - = / .4...L - .:,-10 1 - I 4- \ - [ t® 0 0 k .6. I E I E GO 0 a \ / , • I -. ..- @ I - -I I. ) , , 1 RO® a — --- I E , , , B @ I E f B , 0 0 I C + , + , / + , 1 0 I E 13 B , El . • / t, 0 .1 r frtv--P-P - 0 13 00 r 1 E / .1 ' ) ,2 / e @ r 510 - ....., IEI [ • , .• - = ( 0 ...... -* • , 0 r I p 1 E ) 0 01 I E - + = t ,,, + \ 0 ‘E EE ON II •-• 1 0 ; I E = + - = , ..-. £ = ■ 0\ E .- - ..- -...... ,r (IIj El 0 ..• ■ t i ...... ••.. / / / I E = + + = % ®1 r..= = 3BB ••• -.. (0 0 0 0 ( 9 9 I 9r313 •...... _ ...... , I E 4- - = . 9 • + = N \ I E , + ++ E , • E. I3, 0 ..- -., \B I E , + + + - ■ = E. B • ..-... % --.. / \ `/0 \ I E • = E / 0 B) / --`• I E 3 = /II / B / / == I E 3 E ..:, = B = / 1 1® / B - I + - ... + / 0 0 1 =B I / E + + ''' I = I [ = = £ = B I [+++++++++++++++++++++++++;++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++44.4+4LT FIGURE 7.15 • MTNEX-WALES 4PROJFCT 94* - NORTH PEMBROKESHIRE FACTOR SCORES - FACT 4 )LOW-PASS FILTER USING EFFECTIVE RADIUS OF i CELLS [4.4-4.-11.4.-1-4-4.-1-4-4.4.4.4:}F 4-1-41111-4.—.11.4.41111-++++++++++++++++1 4 1•+++++++++++++++++++++++++++++++447-1-+ 1-4.11.4++++.411--..++++++++++++++++++++++++1 I I E FACTOR LOADINGS 1,-."'"'Inn = I : E .... erF4 A \ [ Sn 0.9 z£ /0 r tr \ B . I f3 0 --- '" / [ e \\ i £ I [ 5 0 /...e= f 0 ■ • I ...\ 8 0 13 / 213 1 000 Br3 C el C - .....0 U e%i' , I I 1 [ 0 II / + (-0 80 a ■LBB= -, , I E • B a % = + ...... 0 C --- ' E I h ------‘ E £ -.. 0. 1 + B - -.. --. 0 ' 0 ...... I [ == -- -- 099 ...... 0 ...N. .... I ■ ....., i on 1 1 E £ .{.; £ , ■ ...v .... N. I C - - 0,- B I - B N e 1 [ 8 B 3 t 7 .---. I C + - - 0 - E I . - - E 0....•)j, + £ FB 1 C B £ = B EE £ = £ BB ■ ..0 00 \= I 0 I ...... -'" ..- - I C I 0 Of. . P - E e - -N B E - - - - -.. = B\H e E -'e o k---' e a *"."*-.- -.., .... - 1 BB 8 -.. ...== re e 1 8 N 0 / 1 , I 316'•-•••••I ‘....- 1 / C 0 a 0 0 a 0 1= `a \ / .0-.0 I C e o a 0 j E. f.: = \ • +/e - .- .... , -I C 0 - 0 / £ 7 I 7 \\ El \ e = / a I / e...- I = v \ - • Ip • • I E . ■ \ = + ■e3 / • • I I • • > \ \ = . • • + , i C = + . . 0 1 - + £ t v . i r f = 4.1. 4 `./ • I C + 7 + e I r+++++++++++++++++++++++++-+++++++++++++ 4++++++++++++++++++++++++++++44444 4+44- 44 +4-44 44+4+ ++++++++++++-++++++++++++++4.+++++++++1 FIGURE 7.16 MINEX -WALES *PROJFCT 94* - NORTH PEMBROKESHIRE FACTOR SCORES - FACT 5 )L04I-P ASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS [++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++i E I I • ,...---s .• I C FACTOR LOADINGS ‘s ...,__.. i C • f A 0 I 00 B C Ba -0.8 BB £ t -"‘ HI E + . I C2Mo -0.7 I 0 B 0 - -,s -r I C ....\ , I C Ga -0.4 00 0 0 ..- + -V - I A 0 HA ' = li r= 1-= . ...I.+ •..... , I C Cu -0.4 / / I H t B 8 -13 - -.1-4, , I 1:.- . / [ ' V -0.3 A @ e-•-'ss B R £ / - = I C . 89 £ 0 + . I Fe -0.3 JP 7 s „.- ..- - . C 8 8 B / s__ BBE I _-... I C G I/ + + ■ e t- I [-N.6 = + N ..--4. t. / N. = . I -"=i 8 . + ...... , 1 i .0- N, . I C , 0 2 %. / 8 • I • r ...... / s_.../ B/ . I £ I - I ss = I e \ I [ .: e-----'1 / = / 8 1 / *N.N. 100 N I I..- -...... -. t C \ I ++ "I / z. £ E eel ' I .. pi t ... / "I I - _, [ . e 0 5 I =t.'" B 0 % 0 0 e..... / I C aw 1 , • I = = \ f - == I ,...- "i C \ £ i.E.) % 0 / . /1 ■ 0 I 4 11 F3E3 , I ‘, 0 / - . .. I + f. .7i% 9 I / I C - /Elf'r 1 el1 % 0 B , ... ✓-0, . L / ,/ ...., I /E i + "' . __ s s .., = I -), = I B 0 E , • • I I 71*-7-) I if'. , I I El 0 1 = / zi N 0/ + /..-.. - 0 -. / /4...... / 1 = \ I - I I el i B ■ -- ' / 1 \ v - • I I =1 a , 50 E 1 = . 1 v I \ e.....„ I , - ...‘ / \ % 8 I : 1 0 I , -- I I ♦ / R) \ 1 I ' B 11 ,..==s I ill, I 7 = 7 / / 1 , -• 1 1 I • • I =- . 1 I 3 ,. 1 I , >+ %.•.'" • I • • I 0 + + 1 T 4. ****** 4.++++++++..+++++++++++.++ 4-41-4-+++++4+++++++++++++++++++1-4-#4111- ++++++++++++4+++++++++++4-+++++++++++++++++++++++41-1 FIGURE 7.17 • • • • MINEX-WALES *PPO JECT 9+ - NORTH PEMBROKESHIRE FACTOR SCORES - FACT 6 )LOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS L ++++++++++4+++++++ +++4- J1-++ ++++++++++4+++++++++++++4+M+++,-+++++++.0-11-4.4.4.4.+4.4.4.4.4.4.4.4.4.4.4.4.4.4.4. 4.4.4-1.4.4.4-1.11.4.4.4.- +++4.4.4.++++++++++++++++++ 1 I . I I I I FACTOR LOADINGS T E ■ e • I 0 8 I E As 0.8 -- = 3B 0 RI E - I Pb 0.6 _ = E - .. o I I - $ $ t...... - • - N I E Cu 0.4 II3 - 9 B - 1 e ...N ..• .... ,.. 0 I I 1" ..• 00 1 0E8 £ = iBE --■ 8 1 I I • ..- / i 0 I £ / 0 / Et £ £BEc'- 1t e \'''' I • 4- .„„.....- I f = 1 0 ....■•-•"'-- B / - E 1 0 I I / a ig t B = I a I I -- B / I === 1 I = \ I I I B ( a o I " 1 0\ ""' - '''' N \. I I = / + ‘.... -- a 0 i % % 0 / _ 1 £ ‘.. 0 I L 7 + I E. N / ■ 0 1 • N. -.... -I I 9 I 0 0 / \.. I $ N 0 .0"/ = P I P3 =/4--7-7/ 1 I t1- i)0 / £ E. -- El I = 1 - + ..._..../ 2 f + = / / £ = B B I 1 0 - B 7 -- f = I 0 ,/ LE == £ f e ‘ I ....'N . ,,.: B I I • , • • + . % _ + • .•. L. •0 - E .. I, ... I I • y . y p \ N f f E Pt:10 . ; £ - I 0 1 = £ I I ...... 1 ■ z . ', / I y - % 0 1 eilo ...... 1 1 I I . $ B i ■+ _ .1 t" 0 - ...... - - / f 0 / ....• 1 t I I I - 0 + -- . 0 0 1 E = I I 1 B n /+ - - 1 1 BB i 0 0 13 1 1- +I I / 4 - t® 0 / = B IQ@ 1 I I E ■ -- - 0 /1 £ £ It@ I I I B ..... £ 3'1 0 0 I +,. -■ B E 0 / I 1 1 0 ‘ - = 1 8 t. , - 0 1 . 0E I / - % •..N f \.... .1 I E \ ,. \-.-- 4- I ''' I I - = B y + I 14-4-4-44-44-4-4-444-4444+++++4-+++++++++444- 4+444- 4+ 4-4+4-4-4-4- 4++++ 44-44-4-44-4-1-4-4-44+4-44-4-444-4-4-+ 4- 41-4-44-+++++4++++++++ T FIGURE 7.18 • HINEX -WALES *PROJECT 94* - NCRTH PEMBROKESHIRE FACTOR SCORES - FACT 7 SLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS +++++++++++++++++++++++++++++++++++++++++++++++ 4++ +++++++++++++++++++++++++4-4-++++++.1-+++ ++++4. 4-4+4+4+ 1-4-4+4+1-4-4+4+4+4-4+4+4+1-++1 I I I FACTOR LOADINGS . = + I Mn 0.8 7 7 - ' B B -I B , £ 9 I Fe 0.6 B + • , + 1 Co 0.6 -- + ...- ----.., , - + • I ..... r3= + = I 7 7 .0 , B . -+- Ni 0.3 .. • 4- / 0 N. B , B ++--s + I Cu 0.3 + / a 0 0 \ - , I / etc" -N g 0 I' • B = • £ I - 7, "' / eal , 0 1 / • - B B ..1 E1 0 1 I / I = B/ 0 ...... ■ •".... 1 0 1 I .t. / 1 i - 9 = 9 ■'- = I 1 % . £ ( g /+ £ 0 ‘..-_..% 0 £ I / ■,... - ., T 1 - E • 1£ I. ,- ..... ee g % .7 -- ,. ""• 13 ■ mi £I , I 1 N ... .—. \ 8 1 i 8 1 F3 9 = ( a ) £ - -. = + 7 f I : / ) 0 0A:) / 0 % BB . "... -.., - = BB •• 0, r39 = 9 I . / 0 o 0 0 I = I e ,...... - - ...... -.. £ 4. - e ..-1 \-0 cf. B I a == + 9 \ 0 • . . 0 0 0.. i / 1 t / + / 0 1 . , .' 1 e •■• I 7-: , .., 0..-.... 0 1 ■7 + / 1 \ \ I 0 I 1 \ I . NO I£ 1 a '.- 8 8 .., — — -." E / i ' \ : I @ A a e ...... 0". E BR • ....ft,. 1 0/ '\ 8 8 N. + I \ = B 9 1 00 i , . I / - I 1 e t £ ‘,_ _. / B 0 ‘., £F, I 9 -/ i --...„.. - .-, 0 0@ I / t1:1 I 1 ‘ - - p / 0 1 E / 0 • - 0 0 0 N 1 - - = • i• 0 20 N. •,.. . 1 0 - - B 0 I . • 7 e e I 4-4-4.4-44-4-+4 4-4-# +++.9-++++++4-+++++++++++ ++++++++4-1-+++++++++++++++++ f+4-4-4-4-4-+++++++++++++++++1 FIGURE 7.19 200. CHAPTER VIII INTERPRETATION OF GEOCHEMICAL ANOMALIES,ANGLESEY 8.1 INTRODUCTION This chapter presents the follow-up study of anomalous patterns revealed by the reconnaissance survey in northeast Anglesey. The stream-sediment data shows anomalous and marginally anomalous values of arsenic, copper, lead and zinc that probably reflect the presence of mineralization buried under glacial overburden that covers the area. A detailed study was made of the secondary dispersion of copper, lead and zinc in order to understand the mechanisms operating in soils derived from glacial till as an example for subsequent geochemical exploration in similar glaciated environments of Wales. An R-mode factor analysis of the stream-sediment data was performed, to determine the element associations and their spatial distribution on the island of Anglesey. Most of the factual information on the area has been taken from Greenly (1919); Roberts (1958); Manning (1959) and Wheatley (1971). 8.2 DESCRIPTION OF FIELD AREA 8.2.1 Location The area investigated is located in the County of Anglesey (Nat. Grid. ref. 2300-2500 and 3700-4000). The total surface covered is 600 sq. Kms., and it is centred around the Parys-Mona mineralization. The location of places mentioned in the text is shown in Fig. 8.1. • • + + + + + + + + + + + + -t- + + + Y. + + + + + + F + + f + + + + + + ANGLESEY Pre Cambrian Penmynydd De■onian I 1 Pleistocene Hornfels Carboniferous Gwna and Fydlyn i--- • -.Ii Detailed Followed—up Area l.—.—. —.. Intrusives Silurian Direction of Ice New Harbour Ordovician South Stack 1 0 1 2 miles Skerries Group Basic dykes ro=1...... K ms. 1 0 1 2 3 4 • Gneisses Fe kite after I.G.S. FIGURE 8.1 202. 8.2.2 Geology The geology of the area (Fig. 8.1) has been thoroughly described by a number of authors (Greenly, op.cit.; Bates, 1966; Wheatley, op.cit.). Except for a number of Tertiary basic dykes, the geological succession is dominated by Pre- Cambrian and Paleozoic rocks. The Pre-Cambrian system consists of the Mona Complex, which bounds the area to the north, the west and the south, forming three broad groups of highly folded and deformed rock-types (Gneisses, Bedded Series and Igneous intrusions). Lower Ordovician shales and mud- stones overlain by an igneous suite of felsitic rocks, rest with marked unconformity on the Mona Complex. Silurian shales (Llandovery) complete the succession of Lower Paleozoic rocks. The Devonian rocks (Old Red Sandstone) are predominantly red conglomerates and sandstones with thick beds of marls and cornstones. The succession of Carboniferous rocks is complete, but the greater part of it comprises the Limestone Series. Glacial and recent deposits are highly evident and are remains of the intensive glaciation during Pleistocene times. An ice-sheet of more than 300 mai% thick passed over Anglesey in a north-east to south-west direction, depositing in its advance and retreat, two distinct glacial deposits, known as the Upper and Lower boulder clays, separated by beds of sand and gravel. The Lower boulder clay is grey or bluish-grey highly calcareous in nature, and the Upper till is a reddish-brown boulder clay. Only the Upper boulder clay appears at the surface. The structure of the area is still not well understood but, it is a reflection of the Caledonian and Hercynian orogenies and has a general north-east to south-west trend. 203. 8.2.3 Mineralization Extensive mineralization exists at Parys Mountain, the zone being greater than 1500 Wm, in length and about 400 mtm„ in width, and with old mine workings extending to depths in excess of 300 mts. A smaller deposit occurs at Rhosmynach, 5 kms, north- east of the Parys-Mona mine. The mineralization at Parys Mountain has been described in detail by Manning (1959) and Wheatley (1971). Eight highly silicified and mineralized lodes occur at the contact of the Silurian shales and felsite. Disseminated pyrite, with veinlets of chalcopyrite, sphalerite and galena are found in the south (Bluestone-Mona mine); and siliceous lodes with disseminated pyrite and chalcopyrite in the north. The super- gene minerals are limonite, goethite, native copper, covellite, malachite, anglesite and minium. Quartz is the predominant gangue mineral, with minor chlorite and sericite occuring as products of wall-rock alteration in the argillaceous units. 8.2.4 Soils The soils of Anglesey were surveyed by Roberts (1958) and a simplified map of the area followed up with soil sampling is shown in Fig. 8.2. In general they occur on Pleistocene drift (Upper boulder clay) with their parent material derived from the Mona Complex and the Lower Paleozoic rocks. A larger portion of the area is covered by greyish-brown silty or clayish soils that show an imperfect drainage and are classed as Brown Earth with gleying (Sannan Series); smaller portions are covered by reddish- brown sandy loam soils classed as Brown Earth of low base status (Penrhyn Series). Both series become yellowish-brown, slightly stony, in the subsoil. • • • • ANGLESEY MAP OF SOILS SOIL SERIES GROUP t~·::·~·:::::·:~:le:::l•• ~.r.·:::. . CARON ] ORGA"'JICI' _ GESAIL 1GLEY ~ BRAINT ~ GAERWEN ~ TRISANT D ARVON BROWN EARTH ~ PENRHYN E3 SAN NAN 8±EB ROCK DOMINANT after Roberts. 1958 0 1 2 r , I miles 0 2 3 !-- I Kms. ------_. FIGURE 8.2 204. 8.3 GEOCHEMICAL DATA The geochemical data assessed here were: the multi-element stream-sediment analyses of the reconnaissance survey; and the results of soil, sediments and rock samples collected in the follow-up stage. The methods of sampling and chemical analyses are given in Chapter IV. All direct-reading results were confirmed by spectrographic analyses before detailed investigation in the field. 8.3.1 Reconnaissance Stream-sediment Results As described in Chapter V, the reconnaissance survey revealed an anomalous pattern of copper, lead and zinc, in the north-east of Anglesey. The results covering this anomaly have been replotted on maps of 2-1 miles to 1 inch, and are illustrated in Figs. 8.3 to 8.6. The distribution of the data of the four elements plotted, is illustrated in Fig. 8.7 and their background and threshold values are shown in Table 8.1. Table 8.1 Background and threshold values for arsenic, copper, lead and zinc in stream-sediments of Anglesey, based on log-transformed data. ARSENIC COPPER LEAD ZINC BACKGROUND 8 30 29 120 * 0.1 - 25 4 - 60 5-50 20 - 30 4. THRESHOLD 180 150 750 6‹ + 2s) 75 * geometric mean in ppm + range of values in ppm 3 74 .c, :5 • O 0 0 O o 0 o 0 0 0 o e 0 0 0 o 00 0 0 c.) 39 0 0 0 0 0 00 o® 0 0 0 O e 0 0 0 0 e 0 0 0 00 0 O 0 0 0 0 0 S 0 0 0 O 0 . 0 0 0 0 o O 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 3 (9 atv (9 (90 e 8 O 0 0 0 0 0 0 0 0 0 0000 0 0 0 00 0 0 0 0 0 0 0 00 0 0 0 00 0 0 0 00 0 . o 0 00 0 0 0 O 0 0 0 0 3 7 ANGLESEY METAL CONTENT OF —80MESH FRACTION • > 30 ID m O 15 — 30 ARSENIC O 8 — 15 IN STREAM — SEDIMENTS O 4 — 8 O <4 1 0 1 2 -4 miles Kms 1 0 1 2 3 4 FIGURE 8.3 2 '0 2 5 O 0 • 0 0* • a 0 0 00 co 0 * 0 0 0 0* 0 0 D 00 O 0 0 O 0 0 0 0 0 • 0 0 0 00 0 0 0 0 @@ o 0 0 O 0 0 0 ® O 0 0 00 0 0 0 00 0 0 0 o 0 o o o 000 00 0 0 O 0 00 0 0 0 O 0 o 0 0 0 O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ANGLESEY METAL CONTENT OF -80MESH FRACTION 410 >60 ppm O 30 - 60 COPPER IN STREAM - SEDIMENTS O 20 - 30 O 10 - 20 O < 10 1 0 1 2 6=necerraimermmod—.-- miles jr, s 1 0 1 2 3 4 FIGURE 8.4 0 0 • 0 @ @ 0 0 0 @ 0 0 0 ®O 00 © 0 ® 0 0 0 0 0 ® 0 00 @ @ 0 0 00 @ 0 @ 0 00 0 0 @o 0 0 0 0 0 0 @ 0 0 0 0 0 0 0 0 0 00 ~ 0 0 0 0 08 0 0 • I ~ ; . 0 , 0 0 0 0 ® 0 0 -G-0G·---0- . G 38 1 ! @O @ 0 l i 0 0 0 0 0 1 000 00 0 0 0 ® O® 0 0 0 0 0 o. ® 0 0 0 0 ® 0 0 0 0 0 • 0 0 0 0 0 0 0 0 0 0 @ 0 0 17 ANGLESEV METAL CONTENT OF -80MESH FRACTIOI-J © 300 ppm @ 100 -.300 LEAD IN 5TREAM - !>EDIMENTS 0 so - 100 ·0 30 - 50 0 30 0 1 2 h ..=-:=..:t.. .. :.¥"'""'...,....",.-'"==-~J rn iles Fo~--=r"' .. '"1--=~-==-l ~~nn 1 0 1 2 3 4 • ------~~~ FIGURE 8.5 3 2 4 0 25 O 0 • 0 . 0 0 i 0 0 • 0 0 0 0 0 0 0 ee e 0 0 39 0 0 0 0 0b 00 o 0 0 o . • 0 0 0 0 c i D O 0 0 00 0 o 0 0 0 0 0 e 0 0 o O 0 0 e - • o • O 0 o • o oo o 0 0 • o 0 0 0 0 0 0 0 38 0 00 • 00.--1 O 0 0 10 0 0 0 0 0 0 00 000 0 0 0 00 0 0 0 0 0 0 0 00 0 0 0 00 • 0 0 0 00 0 O o 00 0 o o O 0 0 0 0 0 ANGLESEY- METAL CONTENT OF -80MESH FRACTION a >300 ppm ZINC O 200 300 IN STREAM - SEDIMENTS O 100 20D O 50 100 1 0 1 2 o <50 miles Kms • 1 0 1 2 3 4 FIGURE 8.6 • • • • •_ • SIG•A mISTOGRAN OF cu VALUES /0 PCT ASO PPM 31111 NISTOLVAN or 266 554255 I? PC? 663 /Pm - . HISTOGRAM INTO %%%%% ARC LOCA/IT•mic• • NISTOGPAN INTERVALS An LOG/RITImIC • • • X • 1.21 X 0.4410•01 • 11.1170.02 • • 0.10 _ • • 6.11 1.5660.11 • 6.2310.12 • 0 • 0.61 • •2-_- • •• .2- •••• 6.05 6.7170•01 • O 0.292E072 • . _ • 1.1• •-•-• • - 1.71 0.1052•01 • 0.3530.02 • . • • • 2.54 9 1.16 0.1146,02 • 0.4640.02 • - XXX • 5.11 2." 0.1440•02 • 0.5656.02 • 611156I01 • 15.46 xxxxxx • •• _ .7 . • 06.65 0.1,20.12 • 0 0.7350.02 • xxxxxx 6X • 06.13 616106 113 1/..35 0.270i•12 • 0.9312•02 • xxxxxxxxxXxxx • 25.16 wxxxxx 777= - • I z. 0 3.2.••6•02 • 0.1170.67 • mrX • 5.11 xxxxxxx •=2:= - • 14.1, 0.7460.02 • 1..•.•03 • 106X • 6.16 xxxxx • 11.17 0 0.6436•02 • 0.1672.03 • XX • 3.1? XXXX X ::•••=.... •:-..••••_= 2-72. . 2:. • 1.03 0.5.46•02 • 0.2750.03 • . xXx • 5.16 0 _. 5.56 1.7110•31 • 0.2970.03 • _ • 2.56 xx - --_---27 - 4.52 0.1210•12 • 6.3150.03 • • -. -_____ . - - -5... • 1.16 X 1.25 • 6.0170•03 • x 0.4722.63 • x • 1.25 0.51 3.1400.03 • • 1.591E603 • • 1.25 0.61 0.1611013 • 0.7512103 • x • 3.6? ••• • •••••• • 2.5I • • • • • • . • 6 20 6.6 10 1.0 106 CO _ 60 101 •TPCENT • SIGMA •11520GR35 OF M,• 661615 It POT AID PPM 5/061 #2STOG1ANOF 15 ----VALUES1k PCT *NO Ppm . _ IIISTOGNAF INTERVALS 112 LOGRRIT1mIC HISTOGRAM INTERVALS ARC LOCARITtNIC -= -.7. • • • • • • • 2.56 • • .64 0.5311.11 • 0.1150•00 • • 0.01 XX . • 6,64 0.6670•01 • 0.129C•01 • X • 1.94 • 1.62 1.816(.71 • 0.1690•01 • • 1.46 0 _ 7% • • 0.11 0.1600•62 • 6.2220.01 • WX • 3.23 • 1. et 1.1260..12 • 0.211E•01 • Xx • 6.52 6.1526.72 • xxxxx • 10.72 0.3"0"" XXxXX • 2-- 0.1512•02 • • •••• = • 1.63 616•6616150 • 15.35 0 0.5010•01 • xxxXX_ -•••••-!...2.2 :12.-1 _27=-72 .71= • 1.33 0.2710•02 • 0.6561601 • xxxXXXXxXXX 0 • 21.29 X x = '7 • 4. 66 0.2641.62 • p.86:0.01 • xxx • 6.45 xx 71.- ;7= =1_ • 4.06 2.3010•02 • 0 • • 7.74 XX xx xxxxxxxx =.7.7- • :be A. ° 6.631.1•12 • "" 0.1460.02 • xxx • 3.16 XXxxXxXxxxxx - • 24.54 1.5760•02 • 6.1940.02 • • 1.56 0 xxx •••••• 77•-• :7 • 104 1.0121,12 • 0.2546.02 • 0 • 1.45 xxX •.• - 5.66 6..6232.02 • 0.7341.02 • xx • 3.6? ••• • 1.17 0.1662..12 • 0.4372.02 • xx 3.23 • . 0.17 1.122003 • 0.5740•02 • • 6.15 -7-7- ' 1.01 0.1501• 113 • 1.7571.72 • • xxx • 5.16 3.10 • • 20• 46 . 61 ?I 100 6 20 _ 60 _ _ 100 P1RCLYT PCRCEN? - • _ • Figure 8.7 Distribution of copper, lead, zinc and arsenic in -80 mesh fraction in stream sediments, log 10 transformed data. 205. An analysis of the spatial distribution of the four elements reveals that anomalous values occur over Pre-Cambrian and Lower Paleozoic rocks. The distribution of these values over Ordovician rocks shows a regular pattern in a north-east to south-west direction, with the Parys Mountain located at the northern limit. This anomaly could be interpreted as: (i) Reflecting a hydromorphic epigenetic dispersion from buried sulphide mineralization as the anomaly is apparently unrelated to known mineralization or contamination from the Parys-Mona mine; the drainage basin is well defined and the anomalous streams running to the west of Llanerchymedd, do not flow from the direction of the Parys Mountain. (ii) Related to a secondary clastic syngenetic dispersion from mineralized boulders transported by the ice sheet from the Parys Mountain. To establish the correct hypothesis, further stream-sediment and soil sampling was carried out. The results of this detailed survey are considered next. 8.3.2 Stream-sediment Results Anomalous streams were sampled to find cut-off values,this however, did not produce the results looked for. Reconnaissance sample sites were re-sampled and the outcome confirmed some anomalous values, but the majority of them were disproved. This difference was due to mislocation of sites in the original data, but this did not affect the overall pattern. 8.3.3 Soil Results Detailed investigation of the anomaly took the form of soil sampling and of an examination of available outcrop. Soil samples • were collected over the Llanerchymedd anomaly, along traverses 206. perpendicular to the ice movement, and from selected soil profiles. As far as possible, all soil samples were collected from the B horizon (30 ams. deep). The soil profiles were sampled to a depth of 1 mt. To outline the anomaly, copper, lead, zinc, arsenic and mercury were plotted in map-form. The contoured spatial • distribution of copper (Fig. 8.8) outlines three anomalies of which the larger, anomaly I, is a linear pattern elongated in a north- east to south-west direction showing mechanical dispersion of glacial drift. Anomaly II is displaced to the north-east of the anomalous streams, west of Llanerchymedd and it has an elongated shape in the same direction as anomaly I. Anomaly III, east of Llanerchymedd, has too few samples to produce a dispersion • pattern. Lead, zinc and arsenic produced a similar spatial distribution and mercury was slightly erratic without any positive trend. Background levels of copper in soils fall between 20 and 150 ppm, threshold values were calculated at 300 ppm, lead shows similar values, background values of zinc fall between 75 and 300 ppm with threshold values calculated at 500 ppm. 8.3.4 Lateral Distribution of Trace-elements in Soils A study of the mean values in each soil traverse (Table 8.2) shows that the nearer to the source of the anomaly (Parys Mountain), the higher the values in all the elements analysed including CXCu, with a regular decrease away from the source. Copper decreases from Traverse b-b' (over mineralization), by 15.3% to the nearest traverse (2 Kms.), and 81.4% to the furthermost (5 Kms.). Lead • • a • , --;...., 0 , r .., cv rn_:- . ANGLESEY - 0., --..?:;,s.3---,-- __I__ .- n //.. 0 . / ,'O -7. H eCs / 1 O, / ti I o ..:e.,' -Pt C:05,L---4:. 'IP ... COPPER /'/') , •''' al 51----I I ..„. CONTENT IN SUBSOIL / * ...0'....% I > 1000 ppm .% % 1% C) , • /. 0 Ao •/1/0 ® 300 - 1000 11 (-\ 0 0 O 150 - 300 0 11 / 1 /'-' / I • / / o 70 — 150 • I / rz, / f•t) _ ./. ...y., / / • 50 — 70 . ,-,/ , / r 0 < 50 •• 7--The' / ...... // •• ,,I ri , "X ...• OC soil profiles e a a soil traverse r4-> • 0 /_) glacial striae -mo o 0 / 1,.95 /•-•••0--- 0 0 0 O 0 0 of(S , C.) 0 0 0 ,, Llanerchy mecki 0 . (:) 1 0%0 II 0 1 Miles 1 1 2 3 K rns FIGURE 8.8 • • • • Table 8.2 Mean values (ppm) of metal content in soils along Traverses a-a'; b-b'; c-c'; d-d'; and Llanerchymedd anomaly. No. of Hg Cu Pb DI Sn CxCu samples (PPb) Traverse 300 170 290 11 100 18.0 a-al 7 Traverse 26 350 570 230 130 310 20.0 b-b' Traverse 32 70 80 210 140 c-c' 7 5.7 Traverse 36 65 64 160 5 160 3.9 d-d' Llanerchymedd 43 70 65 106 5 130 n.a. anomaly (11) n.a. : not 'analysed • • • • Table 8.3 Mean values (ppm) of metal content in soil profiles (sample sites A - B and H) over known mineralization. depth Description Cu Pb Zn CxCu Sn pH (cms) Dark reddish- brown with 15 500 1300 1000 30.0 15 5.1 rock chips, friable. # Dark reddish- 30 1300 850 1200 . 38.0 5 5.0 brown compact Light, yellowish- . 60 1200 1000 1000 38.0 5 5.0 brown, rock chips. ROCK 209. decreases in the range of zinc 18.1-51.5%, CXCu 10.0-95.0, tin 91.5-96.1% and mercury 67.7-48.8%. 8.3.5 Vertical Distribution in Soils and Drift To understand the mechanisms of the vertical distribution of the ore-elements in the solum and drift, soil profiles were taken at selected sites, down to the surface of the ground moraine. Tables 8.3 to 8.6 summarize the results obtained in . the different horizons and at the top of the Upper boulder clay. In soil profiles taken over known mineralization (Table 8.3) • there is a constant high concentration of ore-elements, distributed evenly down the profile, with a slight increase of the metal- • content near bedrock. Soil profiles on the transported anomaly show an enrichment of ore-elements towards the topsoil, and a similar decrease in pH. This distribution is dependent on the soil formation and profile development; the profile nearest to known mineralization has the highest values. The high concentration of all the elements in the A horizon is due to specific metabolic processes of organic accumulation of trace-elements and to sorption. The soil profile taken over the Llanerchymedd anomaly (II) shows a similar distribution as the one over known mineralization but, with a much lower concentration value. Copper and CXCu are the elements displaying the best similarity. This anomaly could be a reflection of a hydromorphic dispersion from mineralized pyritic veinlets that the author has observed in the micaceous gneisses underlying the anomaly. • • • • Table 8.4 Mean values (ppm) of metal content in Soil Profiles (D and E) on transported anomaly, not related to known mineralization Depth Description Cu Pb Zn CXCu Su pH (cms) Reddish grey to dark reddish brown, porous, 15 350 75 400 8.0 5 5.1 friable Reddish brown with . light bands and 30 150 60 220 3.5 5 5.2 orange mottles Light reddish brown or greyish, compact, 60 85 60 350 1.5 2 5.2 orange mottled Yellowish grey, 8o 400 2.0 1 5.4 stony compact 70 75 Weathered 100 120 500 3.0 2 6.3 morraine 75 Unweathered 150 80 500 1.0 2 6.4 —N morraine o • s ♦ • Table 8.5 Mean values (ppm) of metal content in Soil Profiles (C) on transported anomaly, near known mineralization Depth Description Cu Pb Zn CXCu Sn pH (cms) Reddish brown, porous, shale 62o 500 600 18.0 13 5.0 fragments Reddish brown, red mottled, with 350 300 500 16.5 8 5.0 shale fragments Light grey, compact 190 180 400 6.5 6 5.1 orange mottled Yellowish-brown compact, shale 65 75 350 1.0 3 5.1 fragments, orange mottled Weathered morraine 300 300 500 7.0 5 6.3 • • • Table 8.6 Soil Profile (F) on Llanerchymedd Anomaly. Values in ppm. depth Description Cu, Pb Zn CxCu Sn pH (cms) Dark reddish brown, 15 160 100 300 3.5 5 4.5 porous, friable Dark brown with 30 150 60 200 1.0 5 4.8 shale fragments Reddish brown and yellowish bands, 60 60 40 150 1.0 <2 5.3 orange mottled Light yellowish, brown, porous, with 80 160 50 130 3.5 <2 5.6 shale fragments Weathered morraine 120 180 60 200 4.0 <2 6.2 213. 8.4 SUMMARY AND CONCLUSIONS OF THE GEOCHEMICAL DATA A summary compiled from the associations formed by the R-mode factor scores and their distribution show that the metal content in the stream sediments is a reflection of mineralization, lithology, and is possibly influenced by waterlogged soils. The association of Mn-Co-Ga-Ni-V-Ti (Factor 1 - Fig. 8.9) is sympathetic with Pre-Cambrian and Lower Paleozoic rocks outcropping in the east, with a large pattern spreading on a north-west to south-east direction, this pattern is influenced by the lithology and waterlogged soils of the area. The association is antipathetic with Carboniferous sediments. Copper/lead mineralization and the secondary dispersion caused by clastic movement of mineralized boulders from Parys Mountain, and post-glacial soil forming processes - is reflected by the Cu-Pb-Fe-Ga-Sn, negative signed association (Factor 2 - Fig. 8.10). The outstanding features of this association are: the length of the pattern, over 20 Kms.; and the association formed with tin and gallium. Tin has not been mentioned in any previous work from the area and could be directly related to the felsitic body, north of the mine, and to a possible occurrency of stanniferous minerals in the ore. Gallium in association with copper has been shown as a very strong factor in the copper mineralization of Zambia (Armour- Brown, 1971). The association of As-Zn-Cd (Factor 3 - Fig. 8.11) has a similar distribution as factor 2, and possibly refledts the sphalerite mineralization (bluestone) occurring at the Parys- 214. Mona mine. Analagous patterns are found over Pre-Cambrian and Ordovician sediments in the north-western boundary of the area and over Carboniferous sediments in the south-east. The single association of barium with negative sign, (Factor 4 - Fig. 8.12), is sympathetic with the Coedeana granite, and the hornfels that surround it. This association reflects the high content of potash feldspar in the granite. The negative association of Cr-Ti-V-Ni-Ga (Factor 5 - Fig. 8.13), overlaps geological boundaries but, it seems related to acid intrusions and to the Gwna and Fydly Group of the Bedded Series. There is also, some influence from Devonian sediments (Old Red Sandstone). Mo-Sn forming a negative association (Factor 6 - Fig.8.14) is limited to Pre-Cambrian and Ordovician rocks on the northern boundary. This association may be influenced by organic-rich metasediments and by a possible acid basement near to the surface. A similar but smaller pattern occurs over Gwna metasedi- ments extending over Carboniferous limestones, this pattern is difficult to explain and needs further investigation. The metal content in the soil traverses and profiles studied are related to secondary dispersion from mineralized zones and from the dispersion of boulders in the Upper boulder clay. The elements highly influenced by these effects are: Cu; Pb; Zn; Sn; As and Fe. Superimposed upon this distribution are the effects of post-glacial pedogenesis and to the adsorption of extractable ions on organic colloids in the topsoil. e 215. 8.5 ASSESSMENT OF THE MINERAL POTENTIAL OF THE AREA ON THE BASIS OF GEOCHEMICAL DATA The type of mineralization expected in the area of study would be similar to the stockwork of copper, lead and zinc mineralization found within Lower Paleozoic rocks at Parys Mountain, and to lead-zinc vein-type mineralization in the Carboniferous limestones. The significant geochemical values encountered in stream-sediments and soils are the effect of a hydromorphic secondary dispersion from known mineralized bodies (Parys Mountain), and from the mechanical dispersion at the time of the glaciation from drift formed by the Irish Sea ice when • it moved across Anglesey. Copper values combined with the Cu-Pb-Fe-Ga-Sn and As-Zn-Cd associations found in stream- sediments are a perfect example of these forms of dispersion. The high copper values combined with the high R-mode factor scores west of Llanerchymedd was confirmed as a hydromorphic secondary anomaly derived from quartz-veins with disseminated and streaky pyrite, although no chalcopyrite was visible. • The copper content in quartz samples was of 100 to 180 ppm. These values and the size of the anomaly, makes it of non- economic significance. The copper anomaly combined with high factor scores in the southwestern boundary of the area overlying Silurian rocks near Valley aerodrome, although interpreted as glacial dispersion needs further investigation. A detailed study is recommended with soil sampling on a square grid of 100 mts. centres, and with soil profiles down to the surface of the • 216. morraine. The results obtained should be assessed and compared with the results obtained in the profiles of this thesis, over known mineralization and from background zones. The association of As-Zn-Cd shows an interesting‘ pattern over Carboniferous limestones which is worth a detailed examination of the area in future exploration projects. The values of tin found over and around the Parys-Mona mine are a possible indication of stanniferous minerals in the ore-body and future chemical analysis should include this element, especially in core-samples already available. In summary, the area offers two localized zones with possible buried mineralization of copper-lead-zinc but, the • economic potential is limited and restricted to further development of the Parys-Mona area. • • MINER—WALES * PROJECT 910' ANGLESEY FACTO°, SCORES — FAC TOP, 1 OLOW —P ASS FILTER USING EFFECTIVE RADIUS OF 1. CELLS I -11- ++++++++++++++1-++++++++ +++4- ++ ++ ++++++ +4- ++ +++ +++ I I I I I I I I I I I I I I I I I I • CV 10 .10 10l2 4.1 1).1 : 1.2.11 TRee -0.50! 00,t / 1 I I = t F000 -.OTT TO -1.1,1 I I 1 I t "... ., E I I— .. — I + t•i;) = / ...." I 0110 .1.te! 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B 9 2 t felt:II/013 I ■•• .- .., T I 3 ..' - E ■I 0 i I I ,..--,... — B ..., I I ra) 0) I I — + I I — ,— --. I i I %.,....0 _ ) 1 I I 1 — I I+++++++++++++++++++++++++ ++++++++++++++++++++++++++I FACTOR LOADINGS FIGURE 8.9 Mn 0.8 co o:8 Ga 0.6 Ni 0.6 V o.6 Ti 0.3 a • MINX-WALES 4PROJ7CT 944 ANGL:SY FACTO SCORES - FACTC,Z, 2 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS 1+44-1-4-++++++++++++++++++++4 ++++++++++++++++++++++++++1 I I I I I I I I I I I I I I I I I 7 f 7 If P • I / I I /'-'` • I 1 211. .1.B! TO -1.451 1 I f: .. ' • moo V** 10 I \---0. 7 % • I • C) 7-- I 2.1. -0.611 TO f I . 1=."=. B 9 1 I • I • 1 B 3 91 _ 1 . ' I - ...... = ...... T i F•00 -I.0.2 IC -2.111 I /1 1, .I I- /0 9 ... , n 1 .: f 1 ...... %\ = , 60' I/ .1n- -0.121 TO 1.114 / 0 ." I 1 I 1 ( i e I 1 • a I I / I / , ! = 5- ■ % I 1 I 1 7 A I 0 0 2200 0.155 10 1.147 I f/++ ■. ..* 00 • I f ,e,..q,,„ 1 - 40 I..,,,,,,, Ic.003,1401 I/ 0 ■ / ...... • / I 1 ...... 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I I + 9 I I 3 I I 3 I I 13 13 9 I I = _ 0 1 I+++++++ ++++++++++++++++++++++++++++++++++++++++++++1 FACTOR LOADINGS FIGURE 8.10 Cu -0.8 Pb -0.7 Fe -0.6 Ga -0.4 Sn -0.4 • MINEX—WALES *PROJECT 94=`- ANGLESEY FACTOR SCORES — FACTOR OLOW—PASS FILTER USING EFFECTIVE RADIUS OF 1 CELL .S I++++++++++++++++++++++++++++++++++++++++++++++++++++I I I I I I I I I I. I I I I I I I I I ! 0T, TO FA. o+4000, .I2T1 I • I LIST IMAM .L.MW I I 1 -5.41$ TO -11 0.0 I I f 13 I ( 0 0 P I 7 0001 Ta I !••• I % + == I El • 1 — 0 I 7 1 - / Too, .00012 TO -1.211 I 6 I I I I "‘,..0 1 • I 0 i / » \ El I I N. 1... I 15 0 e' — + ' ii 0/:' I 1 ■ S.- I F.O. -1.211 IC .7.1?! I I ■ 0 / .0 - 1 I ...... I I + % ...... /. B + ,,, 0 „""*.".../ t@..., / I + — B ,e' I • ,R0. TO 1.100 I / B I B / 13 s I B e 1 B 3 e .i.: I ■ I r*O0 611,9 TO 1.7o0 I I 1.°"... / I t "0611,9 SO1 • 0 / OF 01,r,10.111 i ',pm/4943410 I % °I + I I ...... 00T,0111,101 ' 1^01,11,0111 a %.• .00 . .1_ nJ I 1 I i 1 MT 0.291 13 1...T.. / f al , ...... 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T : i / 3 It + I I t— 4, A + • I I++++++++++++++++++++++++++ ++++++++++++++++++++++++++1 FACTOR LOADINGS FIGURE 8.13 Cr —o.8 Ti —0.7 V —0.5 • MINEX -WALES *PROJECT 9i+ ANGLESEY FACT00, SCORES - FACTO? 6 OLOW-PASS FILTER USING EFFECTIVE RA)IUS OF i CELLS I+++++++++++++++++++++++++ ++++++++++++++++++++++++++1 I I I I I I I I I I I I I I I I I I = I tII4 1wRav r, 71C 0:4.. / ,4 0. .2.710 IC .1.111 C fft00 •1.1.0 11 •/.74I '''''''' 4.0.014,1 I 1 1 ...... J + ..i I I f404 .0.741 10 .1.171 . + — I + — \ -- 1 4 ) I 1 . = 1 i 1 \. + i _. 4. N ...... -...-.• .— r0 2 . 1 _ + / . 1 roo. .7.1.1 I n , \ I .1. %. I 6 F \ B t 1 0 SI .... • I 1 _ __ ------. ... I 1 1 6 -.. 1 9 • I = i .0. . : f4CP .0.1C7 70 1.074 1 %...... •.••••• ...... I 0 1— ...... 9 • %. + I 9 .%, I 1 ..._ / ;.., ...... I 9 9 . I I 9 9 9 I = "C. 0 170 YO 4.11T I i ,,,,,,,,,.„ :c,.....r7:73 I 0 .9 3:: = = .. ,...,..... nl.,s'• ',1,1 1 =: 1 ..,0. , ,4 TO . .4 .. I ,f 1f 7 I .14 f 4 . • I 0 = if , 1 I 1 I t + r d 0 B 1 1 .2.] 1 r3 1.S.: I 0 0 0 46 i: I : ,-.,- • m/.44C015.115... , I r I ' I eEo 66 6 B .... I :. 15S 5 1 . " 111.. .44■444 ICC4144.0:145 I 6o0 t ..... 8 ,," I = t•S.1 ..... ' ''''''' ''..ovitele, f - ..... — .. 66 7 a 1 1 .....$7441142RIIII„, 14347167 ...... 1 I ` 7 240212114, 1 I 1/4 I 1 : ... I .. 7 7 I • : .... — — ... •••• _ — — — I 1 B 0 / — B I 0 .....t i I --% B I I 4' f ... " I ' t 1 I 1...... 0 :' a 1 1.,L., - 1 ls' *, I 8 . p n I t I 9 r.., e = I I+++++++ +++++++++++++++++ ++++4+++++++++++++++++++++1 FACTOR LOADINGS FIGURE 8.11+ Mo —0.8 Sn —0.6 • 217. CHAPTER IX LEAD ANOMALIES IN CARMARTHENSHIRE 9.1 INTRODUCTION The crosscutting lead-zinc vein-type mineralization of the Southern Caledonides metallogenic district is apparently formed. by a metasomatic process, closely related to tectono- stratigraphic controls, with ore-deposition influenced by the coincidence of suitable structures (domes, anticlines and synclines) and pyritic shale horizons. Although the lithology and structure of the region between • Newcastle Emlyn in the west and the Ogofau gold mine in the east, is not well known in detail, the regional geological setting of the region formed by Ordovician and Silurian metasediments folded into anticlinal and synclinal structures, conforms with this genetic model. The coincidence of anomalous dispersion trains, shown by the stream sediment reconnaissance survey of Wales in areas super adjacent to the southern projections of the Central Wales syncline and of the Teifi and • Tywi anticlines, offer a good chance of exploration success. The present chapter deals with the geochemical data from the reconnaissance survey and from the detailed follow-up stage in the area designated as Newcastle Emlyn. • 218. 9.2 DESCRIPTION OF FIELD AREA 9.2.1 Location The area under study, is located at the boundary of the counties of Cardiganshire and Carmarthenshire (Nat. Grid. ref. 2300-2700 and 2300-2500), with a total surface area of • 800 sq. Kms. The locations of places mentioned in the text are shown in Fig. 9.1. 9.2.2 Geology and Mineralization As stated before there is a lack of detailed geological mapping in the region and the only reference of detailed work are the maps produced by Evans (1932), his sketch maps are available • at the National Museum of Wales and the map of Fig. 9.1 has been compiled by Harries (1971) and the author. Regionally the rocks exposed in the area are all of Lower Paleozoic age. Blue-black shales, mudstones, grits and coarse sandstones • interbedded with feldspathic ashes make up the Ordovician succession and these are mapped as the Upper Bala Series (Ashgill), following to the nomenclature used by Jones and Pugh • (1935). The Silurian rocks belong to the Llandovery Series (Graptolitic Facies). Basement beds, black shales and bands of sandstones with a basal conglomerate form the Lower Birkhill Group. Overlying this, as an unbroken succession, are the greenish mudstones and sandstones of the Middle Birkhill Group. The Upper Llandovery formed by the Upper Birkhill and Gala Groups, consists of a sequence of massive dark-blue shales and mudstones interbedded with bands of grits and sandstones of the same colour. • • • • • LE EMLYN CARD!GANSH!RE CAR~ARiHENSHIRENEWCAST GALA U LLANDOVERY -< lJ 91RKHlL 220. Much of the uplands and greater part of the lowland zones are covered by unconsolidated glacial drift, deposited by the local Welsh ice which accumulated on the summits of higher hill ranges during Pleistocene time. The uniformity of the rocks in the area makes it very difficult to trace the exact origin • of the drift deposits, but all are derived locally. The structure of the area is dominated by a series of minor folds making up three broad structures: the Teifi anti- cline in the north and the Tiwy anticline in the south with the Central Wales syncline between them. The regional structural trend is on a north-east to south-west direction, curving in the southern part to an east to west direction. The only important mineralized occurrence in the area 4 is the Ogofau gold mine (Roman Deep) located 71 miles southeast of Lampeter, and was a gold-pyrite-quartz occurrence worked until 1938 (Hall, 1971). In this year it yielded . 1000 ounces of gold during the month of October but a complete record of its total production is lacking as, the exact duration of operations is a matter of speculation. Galena-sphalerite vein occurrences are found 3 miles northwest of the Ogofau gold mine. The Llanfyrnach lead mining district is located only 2 miles west of the western boundary of the area, and the Lampeter-Pumpsaint mining districts are just outside the north-eastern boundary of the area. 9.2.3 Soils Soil surveying of the area is in the process of completion, and there is no official publication available. The zones followed-up with detailed soil sampling are formed mainly by: • • • • NEWCASTLE EMLYN z: GALA l.llANXVERY - g a FOLLOW-UP AREAS A "\ Soil Traverse \..A' FIGURE '9.2 222. Brown Earth (Rheidol soil Series); Brown Earth with gleying (Sannon soil Series); and Brown Earth derived from glacial drift (Denbigh soil Series). All these soils are brown- reddish to dark brown silt-loams, friable and with orange mottling. The high ground is covered by gley soils (Cegin soil Series) and peaty soils. A and C horizons are well developed and have an average thickness of 20 cms. The average pH is 5.0, classed as moderately acid. 9.3 GEOCHEMICAL DATA The geochemical data assessed in this Chapter are the multi-element results of the stream-sediment reconnaissance • survey and the results of detailed soil, sediment and rock sampling. The soil samples have been collected as soil traverses (Fig. 9.2) centred around anomalous stream-sediment values. Over a zone south of Drefach-Velindre samples were collected on a rectangular grid pattern. The analytical methods used and the sampling procedures employed have been previously described in Chapter IV. All direct reading analyses for Cu, Pb and Zn were confirmed by atomic absorption analyses. 9.4 RECONNAISSANCE STREAM-SEDIMENT RESULTS The reconnaissance data covering the area was replotted on maps of 21 miles to 1 inch in order to obtain the exact location of anomalous dispersion trains. The results of the re-analyses by atomic absorption are illustrated on a reduced format in Figs. 9.3 to 9.5. Similar results were obtained in computer plot-forms from the direct reading spectrometer results. • 223. Several areas could he outlined as anomalous dispersion patterns but, only those associated with favourable structures were followed-up, and are numbered from I to III on Fig. 9.2. These smaller areas are individually described in the following sections. 9.4.1 Anomalous Area I - DREFACH VELINDRE Streams draining Ordovician rocks to the south of Drefach- Velindre are anomalous in lead (100 to 650 ppm), zinc (200 to 600 ppm) and copper (100 to 350 ppm). The coincidence of lead and zinc with Ordovician shales and grits over the southern projection of the main axis of the Teifi anticline is particularly interesting, as all known lead/zinc mineralization within and near the area are enclosed in similar strata folded into anticlinal structures. A regional study of the mineralized fault system of Central and South Wales shows that most, if not all, are cross faults with their strike varying according to the direction of the main structures. In Central Wales this strike is generally N60° to 70°E and in South Wales this varies from N20°W to a NS direction. The anomaly shown by three sample sites draining the same stream form a dispersion train that might reflect the type of mineralization found in the Llanfyrnach mining district. 9.4.2 Anomalous Area II - CWRT-NEWYDD The Cwrt-Newydd area is located on a similar lithological and structural setting as Area I, in a zone of Ordovician rocks coinciding with the projection of the Teifi anticline. Streams draining the area are anomalous in lead (120 to 510 ppm), zinc s • • • • NEWCASTLE EMLYN CAr.~~A:;TH=~.S~:RE CA;:;OIGA~SHIR!o 2--1 G"'lA u LLA~:O\,'!oRY .< U !3P.' ~I'T _ ...... , ... iJ M BRKU"... L MLLA.~DDVERY ~ ::-=.-'.- ~ .: .. -~ l P·:RKH'll l. lLANDOw'ERY ~. ~ 9AlA g ~~ o ~~!tr)t cv",tf"'"',t 01 s!r~"n s.t"'di~~nt in - eo"'P.S~ fro~I'on COPPER 0 > 80 ppm 0 40- 80 @ 20- 40 0 10 - 20 0 < 10 FIGURE 9.3 • • • -O,~I //\): -(!Y -'j -. r. E :: N V I H n , I 51 'mJ:) t ~ '" >- c n: lie z \U 1" ~ C ~ Q 0 E :t-J (J () f 2: 7. § a. W ~2 a. r~1 j j u 0 ~ E u • • ·0 0 o 0 0 o -.: N 0 ~ I I 0 " 0 0· .... ~ ~ V ~ ® 0 0 • 227. (230 to 400 ppm) and copper up to 460 ppm compared with a back- ground of 20 to 30 ppm. The same criteria adopted in the selection of Area I applies to this area. 5.4.3 Anomalous Area III - MYNYDD LLANBYTHER Area III is located on Silurian metasediments coinciding with the southward projection of the Central Wales syncline, and has a similar geological setting as the Lampeter mining district, mile north of the northeastern boundary of the area. Streams draining to the Tywi river are enriched in lead (100 to 380 ppm), zinc (180 to 630 ppm) and copper (100 to 530 ppm). Lead and zinc could be attributed to a similar galena/sphalerite mineralization as mentioned above and copper values are particularly interesting as they might reflect a vein-type copper mineralization. 9.5 DETAILED FIELD INVESTIGATION OF THE ANOMALIES 9.5.1 Anomalous Area I - DREFACH VELINDRE Detailed investigation of the anomalous lead dispersion train in the Drefach-Velindre area, took the form of close sampling at intervals of 100 to 150 mts of the Esgair stream which carried the anomalous values, and of a parallel stream to the east, coupled with soil sampling along traverses encircling both streams, and of detailed examination of the quarries. The sediment sampling of the Esgair stream showed by coincidence, the cut-off values at the sample-sites of the reconnaissance survey (Fig. 9.3), values up-stream show only back- ground levels (Pb : 80 ppm) and down-stream values remained constantly high. A smaller stream draining to the Esgair stream from the east bank, also showed anomalous values of lead. The second stream sampled in detail carried only background values (Pb : 80 ppm, Zn : 70 ppm). 228. The results of the soil traverses were plotted on map-form and Fig. 9.6 illustrates the lead results obtained. The extreme northern samples on Traverses B-B' and D-D', just south of Drefach- Velindre, form a regular dispersion pattern and are located in the same zone as the anomalous sediment values. This smaller area was selected for a further detailed investigation, which formed the second stage of follow-up. This stage took the form of soil sampling on a rectangular-grid pattern of 50 x 100 mts., care was taken in sampling only the C horizon and the results obtained are illustrated by the lead values infig. 9.7. The lead linear anomaly found, follows the regional strike of the lead/zinc mineralization in South Wales, but has an unusual feature that zinc and mercury do not form a superadjacent anomaly, they form a dispersion halo away from the axis of the anomaly (Fig. 9.8). Other elements such as silver, copper and cadmium are not present in anomalous levels. An X-ray diffraction analysis failed to detect the mineral producing the lead anomaly, its detection limit was found to be 5000 ppm for galena. 9.5.2 Geochemical Interpretation of the Lead Anomaly by Identification of Trace-element Forms A geochemical investigation of the mineral forms in which lead occurs in the Drefach-Velindre linear anomaly was undertaken using the microwave-induced plasma emission system described by Meyer and Lan Shang Leen (1972). The -80 mesh fraction of the soil samples and synthetic and natural standards (PbS, PbSO4, Pb0 in rock base) were slowly heated, and a comparison of their thermal lead evolution profiles (Fig. 9.9) gave a close correlation between • A-.. 11 240 ; 1 DREFACH -VELINDRE 1 A. / l LEAD / \\ ...--- ) CONTENT IN SOILS 1 i DREFACH I .0„," VELINDRE;, >100 I I 6 ppm B ° ,.. ) I / , 0 80 - 100 -I i 1 0o - .:. ----, 0 40- 60 ( A I • 0 < 40 0 .....::::::::::::. . ) 00 00 1 0 d'; .. .:4:•:•::...... selected area ---...... -- / 1 n I / c W) / 0 t. 0 / 0 .; ( 0 0 1 2 0/ 0 4-,,/ y 0 . 111-111 7.11=117. 0 / L Kms 0 0 ...I N 1 „,...-...... _ 06) / - \ ,.., ....., BI.® c.., • cl „.- 6 o i *--. 0 °0 0 00 0 0 \ 1070 0 ‘ 0 -- 1 o 0 0 0 %... 0 0 0 1-.' \ 0 Ci 1 0 ./.° '''.....--."'"g ..e". `'''' 0 \ 1 ...—....—..-•••/.. 0 0 (), 1 1 I / I , / .., ( v \ ip 8 DI N. / s. I 0*- ' \ k \ 1 1 i \ ) . • \ .S\ 0-• —1 1 • .. / '‘ I •••- 1 1 I g27 / ) f).— --. ,..) %.— -- "f i 240 230 N. I FIGURE 9.6 • LEAD CONTENT -80 MESH FRACTION soils stream sediment • >200 ppm 0 >200 ppm 9 120-200 0 .120 -200 80- 120 80- 20 40 - 80 0 < 20 <40 FIGURE 9.7 231. the soil and galena profiles, suggesting that the linear anomaly encountered was due to the persistance of PbS in soil derived from the weathering of an unexposed vein .of galena. 9.5.3 Anomalous Areas II and III The detailed investigation in these two areas was similar as the one performed in the Drefach-Velindre area, although stage two was not carried-out. Sediments were collected along anomalous streams coupled with soil sampling boundaring the reconnaissance anomalous values. The results obtained in both areas were not as encouraging as in the Drefach-Velindre area, and only Traverse H-H' in area II shows lead values up to 100 ppm, the rest of the traverses show background levels (Pb : 40 ppm and Zn 60 ppm) without any contrast. 9.6 SUMMARY AND CONCLUSIONS OF THE GEOCHEMICAL DATA As in previous chapters, a summary a conclusion is compiled from the element-association inherent in the stream-sediment data. These associations are formed by an R-mode factor analysis and are displayed in map-form by their R-scores. Eight associations are found but only those interesting from the mineral exploration point of view are discussed. Ga - Cd association (Factor 3 - Fig. 9.10), although elements being found frequently associated with zinc sulphide is an association reflecting the strong binding of both elements with clay minerals and are not related to mineralization. w •231(a) PPM 600 E mts 0 300 • Figure 9.8 Lead and zinc results in soils collected across axis of the linear anomaly PbO • PbS ITY S N TE IN 0 w 0 1000 T°C Figure 9.9 Thermal evolution profiles for lead from controlled heating of PbO, PbSO4 and PbS in rock base and soil • from linear anomaly. 232. Zn association (Factor 4 - Fig. 9.11), occurs mainly over Silurian rocks outcropping in the northeast of the area and over Ordovician rocks in the west. This single association is sympathetic to some R-score patterns of Factor 6 (Cu - Pb association), and may reflect zinc sulphides associated with lead mineralization. Arsenic association (Factor 5 - Fig. 9.12) has a sympathetic distribution with Factor 8 (Mn-Co-Fe-Ni association) and is an indication of co-precipitation with iron and not a reflection of possible mineralization. Cu - Pb association (Factor 6 - Fig. 9.13) is a good indicator of possible buried mineralization, it is distributed mainly over Ordovician rocks in the south-west of the area, making this zone of primary importance in future mineral exploration projects. Anomalously high concentrations occur locally in soils in the region of the drainage anomalies due to the probable presence of buried sulphide mineralization; amongst the elements affected are Pb, Zn, (Cu) and (Hg). 9.7 ASSESSMENT OF MINERAL POTENTIAL ON THE BASIS OF GEOCHEMICAL DATA The tentative identification of galena in the lead soil anomaly of Drefach-Velindre using microwave-plasma emission analysis has supported the presence of previously unknown lead mineral occurrences within the area. Although this area was the only one followed up in great detail, other drainage anomalies offer the same possibility of success. The Cu-Pb association as stated before is a reflection of secondary dispersion from basermetal mineralization and its distribution over a large zone in the southwestern boundary of the area is very significant and of possible economic interest. • 233. The large pattern of zinc (supported by the Zn R-score map) in the northeast may reflect a secondary dispersion of zinc mineralization, although care should be taken in interpreting future geochemical data from this zone, as Silurian rocks have a slightly higher zinc concentration compared with Ordovician rocks. Future exploration programmes in the area should consider the use of microwave-plasma emission as a diagnostic technique in determining mineral forms in the soil and as a quantitative method for Improving anomaly-background contrast. • ▪ • • • MPIE*X-WALES "PROJECT 91+4 R-FACTCR SCORES NEWCASTLE EMLYN # FACTOR 3 OLOW-PASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I+++++ +++++++++ ++ +4- ++ ++ ++ +++++++++++++++ ++++++++++ ++++++++++++++++++++++++ +++++++++++++ +++++++++ +++I I • 1 0 1 B = - 4. +4. :-.., I + + + I 97 = • FACTOR LOADINGS ■=, I 7 77 II 6 1 I 9 7 9 97 , I ) 4. Zn 0.8 ... 3 + B I 27 + - _ Cd 0.3 7 $ + • • B I I + t" I I -1- • • - + 1 t4 1 .0 .... I I + • E. + • 1 I. -= / I + • to 1 ++ + = 3 == e 01 .•,.. -.•„. „ .,••., I 2 • . I • 97 9 . -: i 0 I 1 PA ++ + , = 93= 9 :- . 1 t ... c I I -44 9 I f 3= - =BI " 0 I ..., ;-.: t ; = s I •••••• ,.••• T.) .1.•, I I i $ Be . I-% 43= + $ -- = F n i pi— •• = 1 1 .0. •i i = I IA! 1-:. F -Jra 1+ +1-+ 9 1 o's ..• -,.,,t 0 f$:..- • f I' teee i + = . + 0 1 ! == I , ••• .- ... I 13= I 1 o0 / 0.- - .. , _ - N 9 .0 t 1 00 I = I ei I', 1 a 0 0 0 % 9 ..0 ..•'" 1, .. 3 El I ••'. 2 / 1 ri / ...... 00 I B /8 .. 0 0 % I .: I / i I.. — --• 05 I :40 0 / % % I = 13 / e 0 00 ® ■ I El El 0 % I I 1 43 1 / = ‘ 1= I % 5 't N..,_... :. 0 = B A I IA e , /= I I 0 4' 0 n 0 e-' B I i „.• r. .- ?, ,..., ■ I ) l I 01. ...= 11-' * 4 fl %01; I • 4- i g ....._., an i 9 • 0 0 0 000 el El I i ... •-• • •z.4•4 .. I a • ,„, 1 z; I (1 1 00 I I ; • ,.• .0., •,, I / E • I I ;"• ...... 1 • 14I - 11 II I0 / • • • ' I i i El ‘.., ...... -/ 00 I ; . " - 14 El / 13 A . i I • 11 / • I9 1 0 • I a q 8 1 . 9 I BO 0 El =I 1 I 0 0 1 n 0 @ 0 0 A e 3 I ; •-• •.••••, ,.„, +++++++++++++++++++++++++ ++++++++++++ 4- 4- ++ ++++++ +++I =" "" >;;°::.':∎" """' ., FIGURE 9.10 MIN,-- X—WALES *DROJECT 94* R—FACTCR SCORES NEWCASTLE EMLYN * FACTOR 4 OLOW—PASS FILT:R USING EFF7CTIV: RA9IUS OF 1 CELLS 1+4-4- 4-++4-+++++++1“-+++4-++++4-4-+++4-++4-4-411-4-4++++4+-1-4++4-44-4-++++4-441-44-+44+4-11-+++++-+++4-44+4+4+4++4+4+4+44+4+I 7 = , = 01 7 - == - r 9 I ,. ... = 77 + + / B9 . 0 I 1,1 1 FACTOR LOADINGS I + B B P -- ... -.... . • == + 00 o N •... .• / I - A ... 9 B 9 8199 :: I o 1 =- _ , 1 @ I I = == BR,.. - + i @ i .4.■ ■ 0 ' @@ I As 0.9 - ' // e- '''' I + • 0 ) 13 0 I • fl ...... ■ ii• / •■ 70 .1..,,,, I + 9 il ,,,,, . , ) I 0 • ••• i-:f.,: ..; * :: ; ** -:::: ::: ,::: '' 'i I . ==P • 9 13 1 + = t 0 e , I 0 e f. B"...,e I :: 1 9,e t... # , .. , 91 - % _ e 1 ; i - = ; n • Si %• 1'0.. )13 ,...... "...... 4 + 1 = 1 0 000 0 9 N„f4 N C q -' 0 / B -°I 1 I i e O. 1.... ++, = = , 1 B I . -- .•,...” .t.rle I I =' - + .. -.. 00 I B Z' , I + . + = . . *".. 4. == ...- • B :: 9 ... I = ,- • e •-c‘e 1 . [ 1 -+ = 1 = ,„.. 1 , -,• 19 9 =-4. = ==- , . • I x • l '3 .... ; neil• _ _ ... . , , I rl •IMM• .,■• 4 . + %. • r9 _= I • ; , 1 : I • ..... 3 C 9 . , ...„ ++ == ,..„, I i, ••t• .e.tir r, .l.ilf i 4 I 1 t i •.. • , ,...... : I • i 0 N 1 + N ■ 1 9 I ; 2 = = 1 I : :.,• •:.,,,:. ,.,,1 I + 1 00 I 9 i B i 1 - 19.,,, f3 I 7., 11••■ 1 I g i 9 I 1 -. t 9 ••' ‘ '4 I 0 i 13 .. .,,.. dir , % I ri ) I 9 \''' 471 A . i; = T i 1 , ••" .."..*:...... i ■• e•. : 110...... ,1 1 I ;, ,;::! •-=,. ' I . -'.. ■ -;,' ••••• I N a / _ = 11-2, c I ' [ ‘ ... / r ••J• 110.1 70 1.•11 I I 1 :•:, . I 3 3 ; B: ,...% r•••• ..... la. a I II t Bi= I i .." :'..:1 %.0. 0 44. I r ••.- 0,... 7C 7..1r [ I 0.... /r [ I ....0 .0 3 4 t@ i , ON. ... I r r 1 ..= ...... = 1 . - 9 • 4 Il i r 0 % +I 14. I i "'' ..;:::;'',... ''" I I I r4 / - + = = I CI a 1 B = = I++++4•+++++++++++++++++,4•4- +++++++++4-++++4•+++++++++ + +++++++++++++++++ ++4. I.++ ++++++++++ +++++ +++++ +++++#4-1 , T...... •Ct .t1•I,o4 FIGURE 9.11 1 5 ors" ...... 11. el [I [I 111•117.1111311 Ir : 111.11 ..... M KI - MINEY-'DALES *0ROJECT 9t+ R-FACTOR SCORES NEWCASTLE EMLYN FACTOR 5 OLON-0 ASS FILTER USING EFFECTIVE RADIUS OF 1 CELLS I++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++I I 7,:. ) 10 + = , + ++ • E I i -. / 4 + = It • .1:i: / a / 4..., t /.,., i 1 FACTOR LOADINGS I '1:: 1 01 =3 -I. + - . ++ 133 B e .% A...... '-' / I F. 1001=r31:, = t 8 1 9= = •l'0.j., I Cu 0.7 + - + - BD I I-.. , -It-, `. :.- + ) + %s, 0 • .... •••■ I o "- -. '-'1 a `. = + ) + N a -= + % = = I ,Pb . , . O. , . 7. (4...., 10. I m EI i . B % I I r ,...... n 2.....: _.,....,: : I goP ..,/ B - B . I % + + , e - •••tt• •.) ..1.4.• I "*%‘ CI i • + -I 1 -•- . . I = N, • T • = ■•••••1 • El • - I • .: I...... ; I 7n 2 7 • 7 4. • =- • I I \ Sli .. ••• •• ..... 2 , '2■ ;3...... ‘ II • 9 I ; i in 7 •0° .0. r I R': I 0 01 ■ S ++ a p , 0 11% -. I I= B B1= el or?- I* \ .7...-: / • ''' I ; I 0 = = =A ...... -, + 9 , n- 33 -= ,.., '''' "•\ 3 ....• o I I 41 ." = ::: -- = 0, / r4 3 3 + I ro, • r. T. 1. t < I . F.3 I '3 / B El I I e.i N = -- / 0 / 0 B I 1 1 - 4- 7 + I (4 NI 0 = It = ne B ' .. T / / 1 •,• r.T•7 I, 2.22! 1 I % i - n 13 f4 , + ff) 9 S. I • i I / I. • % =. + ; 0 I...... •• ...... • I e .". 1 ...... :. .. . ,...... I• 1 0% - „.... -I 0 El /#. 13 7 0 ill 0t II •1•.. It WO = ritiele I ;.• ..... • ...... 0,01.. I 1 g *. ... + ( 0 I ri I '4, ... ,r-,,-., ...... 100* "" . '.1 •...„• ,,- WO. .... = • I .... .111 If /.•••11^, IN =1 B = 1...... % cr ice: i 0% ‘01'1 , I ; 1.•1•411,171 • 0, ii. = 3 1 : 13/4 --"' a I 3 = .... I I ••■P• la, It ...1:1 I ...10.• 116 1...... • Ie I P # '" • + ...... 0" • F. - I ...... 0.• 1 S. I I + - F - II - :5 ; In = + . 4. ei % .... + •I - 7 I a..,,N ; — + t0; i n e I 1 ,4 dr -r = I • I- .3 f '4.4- 4 4, + ++++ 4.4.+ 4•}4.4. 4.+++++++ +++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++ :: T...... I FIGURE 9.12 t ...... pro• .....(471 ...... •• at T lett ..... t•kt, ...... I T t 1.1,,P , • . •• I i I I .....t i,•til. i I T • I MINEX-WALLS "RO,F:CT 94* r-FACTCP, SCORES NEWCASTLE EMLYN * FACTOR 6 OLOM-DAIS FILTED USING EFFTrTIW: FODIUS OF 1 CELLS I++++++++++++++++++ ++t+ + + +++++++++ ++++++++++++++++4++++++++++++++++++++++++ ++++++++ ++ ++ ++++++++++ +++I I m 71 + e)g 1 I • t '::1 + = • . 1 .. I + ...' = 4 t q e l I I = = N...... = + 1 FACTOR LOADINGS I + = .Rn —.'/..1 [33 . B- = a- 1 .11% :.- 9 + I / + r. (i' elI • -- 1 ri I 111 „ N, + I • = Vi % ,...... % = ++ I Ga 0.8 I + == w ttP ri 7 i g , + ••••1 + N..14, I = + / B 4- 7/ 1 7 3 1..,.....00 4.+ I Cd 0.7 / 4' = N - n I n / / i 1 + • a Bn / - + I •••• ,-•• : 1 o 9 1 9 = I R / r -% , / „■.• '. 9 =I I , t 0 .--. 9 r ...• -1.•sr I + 1.0 /". == + B , I 0 at: 9 1 4 i • 7- , = 9 I I - = =3= = .._...1'.9 ...... I , •••■ = ' 1 == .. I II 7 .-, = % . I BR ••••••• ..., : = = I I le') I ”1" -1..•1 .....—‘ 1 . 1 I '''' *ft ‘..E1 j ...... O() 7 L • II 771:1 a "• 1 I 4,t: .sf:"..1- .... 0 B I I :'... r3 ...• 0 ... I .1 e .:..21/ •••., a , I® .... : = " +4. + I i .C.”.% I (1171:://0 70 ) ...... I I 10 no c.-, a zi .= = == + 1 1 e = + I 1 .!...... ".: 1 .r.) 0 / 3 / l I3 10 0 1 1 B .. ... t'.71 ., + •0 ■ 1 i I r t M I g 1 Qi4 0-...... , 0 1t g 9 3 - • I i • q.....1= •;;;`.;:. .. a I tyl, •./ 0 / 9 '- / %... N I •• .. I _ --. % %,...... / f 5 ‘ 0 ‘,..) BB / - I ;:•...... D %'- ...... B.1 ; - ••••■, ::::: 1 ■ i = 1 4 / - -= - I ,•9.• •.1(9 •C e". I- 1, \ I / ( g 0; r:113 t 0 I I ::::::: .. --- .... ! ::::: I / .. ".. :-: I • I 1 0 .0 , I ••••• (0....." _ I. 1 o 11 0 0 0 1 1 I 1 0 0 i = :. -.' --: - 1 i + + + + + + + + 4, + + + + + + + + ++ + I ;..:::: ::::: 9'494.919. . ::::: I++++ ++++++++++++++++++ ++ ++++++++++++++++++++++++++++++++++++ ++++++++++++++ + + + + I ift 9 FIGURE 9.13 ...... 238. CHAPTER X SUMMARY, CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK ' • 10.1 SUMMARY AND CONCLUSIONS 10.1.1 Regional Geochemical Reconnaissance Survey The aim of the interpretation of the geochemical reconnaissance data from Wales was to determine the geochemical variations related to the mineral potential of Wales, with a view to delineating areas for detailed investigation. (i) Samgling and analytical techniques • The geochemical reconnaissance survey of Wales was based on stream-sediment sampling at a spatial average density of one per square mile. The -80mesh fraction of the sediment was analysed for a total of twenty elements by a low-precision direct reading spectrometer (Quentometer). Arsenic, cadmium, molybdenum and zinc were analysed by atomic absorption and colorimetric techniques. Accuracy and precision have to some extent been • sacrificed in favour of increased analytical productivity (see Sec. 4.3). (ii) Data handling (a) The use of magnetic tapes was found to be a useful method of data handling, but the use of computer cards greatly simplified the sorting and re-arrangement of samples into different categories and stratigraphical units (see Sec. 4.5.1). * 239. (b) The calculation of basic statistical parameters and analytical control was greatly facilitated by the use of computerised techniques (see Sec. 4..5.2). (c) Map plotting using the grey-scale computer program proved very efficient and practical. (d) The use of percentile maps using decile class limits as a means of grouping large volumes of data without a prior knowledge of their distribution has proved very useful. (e) Moving average smoothing was found satisfactory, reducing analytical noise and sampling errors with an enhancement of the spatial geochemical variations. (iii) Regional geochemical variation • (a) Investigation of the frequency distribution of the sixteen elements used in the description and interpretation of the reconnaissance data, showed that the majority of the elements tend to a log 10-normal distribution, with gallium and vanadium tending towards a normal-Gaussian distribution. Arsenic, cadmium, molybdenum and tin did not show a definite distribution. Analysis of the break of slope in the distribution as a means of r differentiating multiple populations, although successful with small numbers of samples, was less successful with the large number of samples treated (see Sec. 5.2). (b) The interpretation of the single element geochemical maps showed that variations related to geology, mineralization, secondary environment, and pollution, had been delineated by the reconnaissance survey. An integrated summary of the regional w 240. variation (see Sec. 5.3) of the sixteen elements analysed revealed that: 1. There is a decrease in the trace element content in stream sediments from the Upper Paleozoic compared with those of the Lower Paleozoic.' 2. Within Upper Paleozoic sediments there is a sharp increase in trace element content in the Carboniferous compared with the Devonian (Old Red Sandstone). 3. Cu, Pb, Zn and Ba display high concentrations over known mining districts. 4. As, Cd, Fe, Mn, Ni, (Zn), and (Co) display high concentration patterns over mountain areas and dissected plateaux underlain by Lower Paleozoic rocks. (iv) Relationship between geochemical patterns and geology Comparison of mean values showed a marked enrichment of trace elements in the drainage sediments from Pre-Cambrian, Lower Paleozoic and Carboniferous rocks, with the highest mean content in Cambrian sediments and the lowest in Devonian sediments, the exception being chromium. The metal distribution reflects ■ to some extent sedimentation facies with an increased abundance of metals from sandstone to argillites (see Sec. 5.5.2). (v) Correlation with predominant type of rocks A comparison between available rock geochemical data and the stream-sediment content showed that (a) Ba, Cr, Cu, Ga, Pb, Mo, Ni and V show a similar abundance in both sets of data. 241. (b) Co, Fe, Mn, Sn, Ti and Zn are slightly enhanced in the stream sediments compared with the mean values from rock data. Secondary environmental features as adsorption, and scavenging of trace elements by precipitation of manganese- iron oxides, and sedimentation and/or sorting of heavy minerals in stream beds are the probable cause of these enhancements (see Sec. 5.5.3). (vi) Relation of pochemical variation to mineralization The patterns of the data from the reconnaissance geochemical survey outlined the metallogenic districts of Wales as areas of high background. Base-metal anomalies are related to past mining and smelting activities, however, marginal and possibly anomalous patterns of copper, lead, zinc, molybdenum and tin were assessed using a filtering technique (see Sec. 5.6.1). (a) Thirteen anomalous copper regions were outlined and only three of them could be related to possible unknown buried mineralization, the remainder of the anomalies overly known mining districts or reflect high lithological background (see Sec. 5.6.2). (b) The lead anomalies showed a similar distribution to those of copper, with eighteen anomalous regions and only three of them reflecting possible unknown buried lead mineralization (see Sec. 5.6.3). (c) Zinc anomalies tend to coincide with copper and lead, with dispersed larger anomalies over known lead/zinc mineralization. Anomalies of zinc shown by the filtering technique tended to discriminate against areas influenced by secondary • 242. environmental effects. Thirteen anomalous regions were outlined and only one is on an area with a favourable geological setting and without a nearby source of contamination (see Sec. 5.6.4). (d) Although molybdenum mineralization is not recorded in Wales, this element was considered due to its association with disseminated copper mineralization and black (organic) shales and mudstones, favourable lithology of ore- deposition in the Southern Caledonides metallogenic district. The plotted map reflects this latter association (see Sec. 5.3.11 and 5.6.6). (e) Mineralization of tin has never been found in Wales and the review of tin anomalies was made as these outlined acid intrusive and extrusive rocks. Five tin anomalies overlying Carboniferous rocks in South Wales are related to airborne contamination from smelter fumes (see Sec. 5.6.7). (vii) Aeplication of the reconnaissance survey of Wales It is concluded from the current study that the multi-element geochemical reconnaissance survey of Wales has immediate application in detecting: (a) Regions of increased metal abundance associated with mineralization; (b) Geochemical facies variations within the geological sequence; 243. (c) Partially 'false' anomalies and spurious distribution patterns related to regional variations in metal abundance, but related to an enrichment of Co, Ni, As, and Zn with Mn and Fe as a result of secondary environmental factors, and enhancement of Sn, Ti and Cr due to heavy mineral sorting. 10.1.2 R-mode factor analysis As concluded in the previous section, the geochemical variations in background levels of the trace element abundance of stream sediments, can be related to three main factors, mining and mineralization, geology and secondary environment. it is essential to determine the element association characteristic of the data from these features, prior to suggesting that regions of high element background delineate possibly anomalous areas of mineral exploration interest. (i) R-mode factor analysis of the regional reconnaissance data R-mode factor analysis was used as a means of indicating the overall element affinities and the results obtained indicate the three characteristic associations. Three R-mode factor associations could be related to geology-lithology, two associations were related to mineralization and one association was related to secondary environmental features. 1. Ga-Ni-V7Co-Fe association was related to argillaceous rocks. 2. Cr-Ti association was related to detrital sediments and basic intrusive and extrusive rocks. 3. Mo-Co association was related to argillaceous rocks rich in organic matter. 244. 4. Ba-Fe-Zn association was related to mining and possible lead/zinc mineralization in the Southern Caledonides metallogenic district. 5. Cu-Pb-Zn-Ba association was related to possible mineralization and contamination from past mining activities. 6. Mn-Fe-Zn-Co association was related to secondary environ- mental features. 7. The seventh factor association is a single-element association of Sn and its distribution is similar to the one shown by the tin geochemical map, this association was related to acid igneous rocks and airbone pollution from tin smelting works. (ii) R-mode factor analysis of the regional stratigraphical units R-mode factor analysis was applied to data sets sorted into the regional geological stratigraphic units. Data sets of fourteen and sixteen elements were considered and the association obtained were broadly similar to the regional analysis, but slightly different in detail. The use of sixteen elements compared with the results of the fourteen elements, did not greatly change the element associations as the elements added, Cd and As, formed single element associations or formed part of a predicted association. An analysis of the factors formed by Cu-Pb-Zn-Cd-As-Fe and Ba are related basically to high background concentration of trace elements in the different stratigraphical units studied. Associations resembling the mineral assemblage of sulphide ores were also formed (see Sec. 6.5). 245. (iii) The use of R-mode factor analysis in follow-ue areas R-mode factor analysis was also applied to the reconnaissance stream-sediment data covering the follow-up areas of North Pembrokeshire, Anglesey and Newcastle Emlyn, and their factor scores plotted on map-form revealed the following relations: I. The geochemical variations of the North Pembrokeshire stream- sediment data was interpreted on the basis of the association derived from a factor analysis and the spatial distribution of their R-scores. Four associations were related to lithology, two to mineralization and one to secondary environmental features. (a) Cr-Ni-Cu-V association and Ti-V-Ga-(neg. Co) association was related to the dolerite-diorite intrusions. (b) Sn association was related to acid intrusions. 4 (c) Ba-Mo-Ga-Cu-V-Fe association was related to metasediments. (d) Zn-Cd-Fe was related to possible Pb/Cu and Pb/Zn/Ag mineralization. (e) As-Pb-Cu association was related to possible copper mineralization. (f) Mn-Fe-Co-Ni-Cu association was related to secondary environment (see Sec. 7.7). e 2. The factor associations formed from the metal content in the stream-sediments of Anglesey reflected similar relations. Four associations were related to lithology and pOssible enhancement through secondary co-precipitation and two associations to effects of mineralization. (a) Mn-Co-Ga-Ni-V-Ti association was related to Pre-Cambrian and Lower Paleosoic sediments. It 246. (b) Cr-Ti-V-Ni-Ga association was related to metasediments of the Bedded Series (Pre-Cambrian). (c) Ba as a single element association was related to acid intrusions (Coedana granite and its metamorphic aureole). (d) Mo-Sn association was related to Pre-Cambrian and Ordovician metasediments outcropping in the north of the island. (e) Cu-Pb-Fe-Ga-Sn association was related to copper/lead mineralization and to secondary dispersion caused by clastic glacial movement. (9) As-Zn-Cd association was related to zinc mineralization (Blue-stone - Parys Mona mine), (see Sec. 8.4). 3. The stream sediment reconnaissance data of Newcastle Emlyn revealed with the factor analysis applied to it, eight factor associations, of which only those reflecting mineralization were interpreted, although the rest of the associations could be related to the two features mentioned before. (a) Cu-Pb association was related to copper/lead mineralization. (b) Zn as a single association together with Ga-Cd association was related to possible zinc mineralization. (c) Arsenic association, although formerly considered to be related to secondary dispersion of sulphide mineralization, was related in this area to secondary environmental features (see Sec. 9.6). 4. As a conclusion, the multi-variate treatment of the reconnaissance data by factor analysis has revealed the strong influence of three primary and secondary features affecting the element association in the sediments: geology (lithology), mining and mineralization and secondary environmental features, 247. (iv) Potential usage of factor analysis in mineral exploration eroiects The use of R-mode factor analysis with the multi-element stream-sediment data of Wales (9910 samples), has been successful not only in reducing by half the number of maps to be interpreted, but revealing the host of genetic factors that form part of the overall geochemical variations. Its potential in mineral exploration programmes is hown by the factor associations formed of elements related to mineralization. A combined interpretation of the spatial distribution of their factor scores and of single element maps could be the most suitable and efficient procedure in delineating follow-up target areas. • 10.1.3 Detailed Follow-Up of Some Anomalous Areas Relative exploration success was obtained in the detailed investigation of some regional geochemical variations. The procedure of selecting areas which conformed to the ore genetic model for Wales and which showed coincident regional geochemical variations marginally higher than the background level of the surrounding area, proved to be efficient and focussed attention • away from contaminated areas. (i) North Pembrokeshire The field investigation of six smaller areas showing marginal anomalies of copper, lead, zinc and tin in North Pembrokeshire showed the feasibility of finding disseminated copper mineralization and the possibility of relating lead/zinc anomalies to probable lead/zinc vein-type deposits. The significant values of tin is • 248. streams draining acid igneous suites, may have no economic significance but, are of academic interest (see Chap. VIII). (ii) Ansle2ey Anomalous copper, lead, zinc and arsenic patterns encountered in Anglesey are the effect of hydromorphic secondary dispersion from known mineralized bodies (Parys-Mona mine) and from the mechanical dispersion due to past glacial movement. The out- standing feature of the latter anomaly is, its length of over 20 Kms. (see Sec. 8.3). Investigation of the lateral and vertical dispersion of ore- elements showed that soil traverses near to mineralization have higher metal values with a decrease of around 80% of the metal level in the furthest traverse (5 Kms). Ore-element content is high and evenly distributed in soil profiles over known mineral- ization; soil profiles along the transported anomaly showed an enrichment of ore-elements towards the topsoils (see Sec. 8.3.3). (iii) Newcastle Emlyn (Carmarthenshire) Anomalous dispersion trains of copper, lead and zinc over- lying favourable regional tectono-stratigraphic ore-depositional controls were selected for field investigation. Three smaller areas covered by Lower Paleozoic rocks were followed-up in detail with the successful detection of a linear lead anomaly in the area sourth of Drefach-Velindre (see Sec. 9.5). Investigation of this linear anomaly with the use of a microwave-induced plasma emission apparatus, showed a close correlation of the lead thermal 249. profiles of soil with galena indicating that the anomaly was probably due to PbS in soil derived from an unexposed vein of galena. (iv) Other areas investigated Field work was carried out in three other areas, North of Dolgellau, west of Llanrwst Vale and around Moel-Ddu and Moelwyn Mawr (Caernarvonshire). (a) Mechanical and hydromorphic dispersion of copper, lead and zinc was investigated along the Afon Wen (4 miles north of Dolgellau). Investigation of different size fractions of stream- sediments coupled with analysis of different size fraction of -• separated heavy and light minerals and ground water analysis, showed that the anomalous metal abundance of copper (up to 4000 ppm), in the drainage system was greatly influenced by mechanical dispersion of chalcopyrite. Copper content in spring and seepage waters indicated that substantial quantities of this metal were dispersed in solution. No definite conclusion was obtained and further research into this interesting problem is recommended. (b) Lead dispersion was investigated in streams draining the Llanrwst mining district and an anomalously high lead content (>1%), in sediments was directly related to mechanical dispersion of galena. Soil sampling along anomalously high lead values west of the district gave high secondary dispersion patterns over the Upper tuff beds (Crafnant Volcanic Series), demonstrating clearly the stratigraphic controls for ore-deposition in the area, 250. (c) Preliminary investigations were made of copper, lead, zinc and tin anomalies in sediments of streams draining to the Afon Glaslyn. Copper was related to contamination from known mineralization, although soil sampling north-east of Beddgelert showed high metal values probably related to vein extensions. The finding of a small grain of cassiterite in the heavy fraction of the sediments from Hafod-Gwyfil is encouraging for a further investigation of acid igneous suites of Snowdonia as possible sources of stanniferous minerals. (v) Potential of follow-up areas The mineral potential of the follow-up areas has been clearly outlined by the detailed investigations in each area. Anomalous and marginally anomalous metal values in stream sediments and soils are potential indicators of possible buried mineralization- and exploration programmes along zones outlined in this research project could be carried out successfully and at a low-cost. Mineral exploitation will always be restricted by world market prices and local environmental impositions. National Parks and private ownership of mineral rights are a severe restriction to economically viable projects. 10.2 RECOMMENDATIONS FOR FUTURE WORK Several high patterns were observed during the interpretation of the geochemical reconnaissance data from Wales, but only a few of these have been followed-up. Field investigation of the remaining areas is recommended applying similar procedures of interpretation and of field work as those followed in this research. - 251. Interpretation of regional stream sediment data over a region the size of Wales, with the poor precision inherent in the spectrographic analysis, can only, be made on smoothed results. Individual high values should be considered with caution, as they could arise from local contamination, sampling or analytical errors. Much time could be wasted in fruitless investigation of these sample sites. The use of computer processing and R-mode factor analysis is recommended when dealing with large numbers of samples and other multi-variate techniques such as discriminant and cluster analysis should also be considered. Detailed investigation should be made on the secondary dispersion of tin from the acid igneous rocks of North Wales, with particular regard to the sampling problems arising from the distribution of discrete grains of cassiterite in the stream- sediments. Detailed field work with close interval stream sediment sampling and with soil sampling along road traverses with sites at intervals of 200 to 300 mts. are efficient and could be carried at a low cost. Soil sampling on a rectangular or square grid pattern is recommended for second stage follow-up work. Improvement in the precision of the analytical method used with future reconnaissance surveys would help in the interpretation of data and in the use of statistical techniques. REFERENCES Archer, A.A. (1959) The distribution of non-ferrous ores in the Lower Paleozoic rocks of North Wales, in the future of non- ferrous mining in G. Britain and Ireland, Inst. Min. & Metall., London, 259-276. Ahrens, L.H. and Taylor, S.R. (1962) Spectrochemical analysis Pergamon Press, London, 454 p. Armour-Brown, A. and Nichol I. (1970) Regional geochemical reconnaissance and the location of metallogenic provinces. Econ. Geol. 65 No. 3. Bassett, D.A. (1961) Bibliography and index of geology and allied sciences for Wales and the Welsh Borders 1857-1958, Nat. Museum Wales, Cardiff, 376 p. Bates, D.E.B. (1966) The geology of Parys Mountain. Welsh Geol. Q., 2, No. 1, p. 27-29. Boyle, R.S. (1967) Geochemical prospecting. Retrospect and Prospect. Geol. Surv. Canada, Paper 66-54, p.30-43. Brundin, N. (1937) Method of locating metals and minerals in the ground. U.S. Patent 2158980 (summarized by Hawkes and Webb, 1962). Brode, W.R. (1962) Chemical Spectroscopy, New York. Cameron, E.M. and Morton, R.E. (1967) Analysis of rocks using a multi-channel emission spectrometer, Chem. Geol., v.2 p.135-142. Canney, F.C. (1966) Hydrous manganese-iron oxides scavenging: its effect on stream sediment surveys. Proc. geochem. Prospecting,, Ottawa. Celenk, 0. (1972) Applications of computer-orientated statistical and mathematical techniques to the interpretation of geochemical prospecting data, with particular reference to the Pirejman area, S.E. Turkey, Unpub. Pb.D Thesis, Univ. of Leicester. Child, D. (1970) The essentials of factor analysis. Holt, Rinehart and Winston, London, 107 p. Cox, A.H.; Green, J.F.N.; Jones, 0.T. and Pringle, J. (1930) The geology of the St. David's District, Pembrokeshire. Proc. Geol. Ass., Lond., 41, p.241-273. Cruft, E.F. and Giles, D.L. (1967) Direct reading emission spectrometry as a geochemical tool, Econ. Geol., v.62, p. 406-411. Cummins, W.A. (1969) Patterns of sedimentation in the Silurian rocks of Wales : in Symp. of the Pre-Cambrian and Lower Paleoz. rocks of Wales. Univ. of Wales Press, p. 219-238. Davenport, T.G. (1970) Geochemical studies of the bauxite deposits of the McKenzie region, Gwyanon. Unpub. Ph.D Thesis, Univ. of Leicester. Davis, T.C. (1973) Statistical and data analysis in Geology. John Wiley & Sons, Inc., 550 p. Davis, W.C. (1971) Regional geochemistry of stream sediments derived from an area underlain bythe English Permo-Triassic Unpub. Thesis, Univ. of London. Dewey, H. and Eastwood, T. (1925) Special reports on the mineral resources of G. Britain., vol.XXX, Copper ores, 87 p. Dunham, K.C. (1934) Genesis of the north Pennine ore deposits. Quart. J. geol. Soc., Lond., vol.90, p.689. Dunham, K.C. (1948) Geology of the Northern Pennine orefield. Vol. 1, Type to Stainmore Mem. Geol. Survey, U.K. Dunham, K.C. (1959) Syngenetic and diagenetic mineralization in Yorkshire. Proc. Yorks. geol.'Soc., 32, p.229-284. El Shazly, E.M.; Webb, J.S. and Williams, D. (1958) Trace elements in sphalerite, galena and associated minerals from the British Isles. Inst. Min. Metall. Trans., v.66, p.241-271. Evans, D.C. (1932) Unpublished geological maps. St. Clears. Evans, D.S. (1971) Secondary dispersion of mercury and associated elements at Keel, Eire. Unpub. Ph.D Thesis, Univ. of London. Evans, W.D. (1945) The geology of the Prescelly Hills, North Pembrokeshire. Quart. J. geol. Soc., Lond., no. 401-402, 101, p.89-110. Fairbain, H.W. (1971) Radiometric age of mid-Paleozoic intrusives in the Appalachian-Caledonides mobile belt. Am. J. Sci., 2/2, 203-17. Flanagan, F.J. (1969) U.S. Geological Survey Standards - II. First compilation of data for the new USGS rocks. Geoch. and Cosmochim. Acta., v.33 p.81-120. Fleischer, M. and Stevens, R.E. (1962) Summary of new data on rock samples, G-1 and W-1, Geochem. Cosmochim. Acta, v.26, p.525-543. Garret, R.G. and Nichol, I. (1967) Regional geochemical reconnaissance in Eastern Sierra Leone. Trans. Inst. Min. Metall., 16, B97-B112. Garret, R.G. (1967) A program for the rapid screening of multi- variate data from the earth sciences and remote sensing. Report No.11, Dept. of Geol., Northwestern Univ., Illinois,USA • Garret, R.G. (1967) Two programs for the factor analysis of geologic and remote sensing data. Report No. 2, Dept. of Geol., Northwestern Univ., Illinois, USA. Gilbey, J.W. (1969) The mineralogy, paragenesis and structure of . the ores of the Dolgellau Gold Belt, Merionethshire and Associated wall rock alteration. Unpub. Ph.D thesis, Univ. of London. Govett, G.J.S. (1958) Geochemical prospecting studies in Northern Rhodesia. Unpub. Ph.D Thesis, Univ. of London. Greenly, E. (1919) The geology of Anglesey. Mem. Geol. Surv. Great Britain (IGS) 980 p. Hall, G.W. (1972) Metal mines of Southern Wales, private publication, 95 p. Harper, C.T. (1966) Potassium-Argon ages of slates from the Southern Caledonides of the British Isles. Nature, Lond., 212, p.1339-1341. Harden, G. (1962) Geochemical dispersion patterns and their relation to bedrock geology in the Nyawa area, Northern Rhodesia. Unpub. Ph.D Thesis, Univ. of London. Harries, W.J. (1971) Pers. Comma Harrison, MI.; Lord, R.C. and Loofbourow (1962) Practical spectroscopy, New York. Harman, H.H. (1967) Modern factor analysis. Univ. of Chicago Press. Hawkes, H.E. (1972) Bibliography exploration geochemistry. The Ass. of Exploration Geochemists, Spec. Vol. 1. Hawkes, H.E. and Webb, J.S. (1964) Geochemistry in mineral exploration. Harper and Row. 415 p. Hill, P.A. and Parker, A. (1970) Tin and zirconium in the sediments around the British Isles: A preliminary reconnaissance. Econ. Geol., Vol.65, No. 4, p.409-416. Howarth, R.J. (1971) Fortran-IV program for grey-level mapping of spatial data. Math. Geol., v.3, No.2, p.95-121. Howarth, R.J. and Lowenstein, P.L. (1971) Sampling variability Sr of stream sediments in broad-scale regional geochemical reconnaissance. Inst. Min. Metall., Lond., Vol. 80, Trans. Sec. B, B363-372. Howarth, R.J. and Nichol, I. (Pers. Comm.) AGRG, 1970. Horsnail, R.F. (1968) The significance of some regional geo- chemical patterns in North Wales and South West England. Unpub. Ph.D Thesis, Univ. of London. James, C.H and Webb, J.S. (1964) Sensitive mercury vapour meter for use in geochemical prospecting, Trans. Inst. Min. Metall., Lond., v.23, 633-641. James, L.D. '(1955) Llanrwst Mining District. Unpub. B.Sc. Thesis, Univ. of London (IC) Jenkins, D.A. (1964) Trace elements studies on some Snowdonia rocks, their minerals and related soils. Unpub. Ph.D Thesis, Univ. of Wales, Bangor. 'IL Jones, 0.T. (1952) Anniversary Address (the drainage system of Wales and the adjacent regions). Quant. J. geol. Soc. Lond. No. 426, 107, 201-225. Jones, 0.T. (1941) The ordovician rocks of the Builth district; a preliminary account. Geol. Mag. Lond., 21, 185-191. Jones, 0.T. (1940) Some Lower Paleozoic contacts in Pembrokeshire (Caerfai and Whitesand Bays) Geol. Mag., Lond., 21, p.405-409. Jones, 0.T. and Pugh, W.J. (1935) The geology of the districts around Machynlleth and Aberystwyth. Proc. Geol. Assoc., Lond., 46, p.247-300. Jones, 0.T. (1922) Lead and zinc, the mining districts of Cardiganshire and West Montgomeryshire. Spec. report Them., Mineral Resources of Great Britain (IGS) Vo].XX. Kakar, S.S. (1971) A study of the trace elements associated with the Pb-Zn ores of Wales, Unpub. Ph.D Thesis, Univ. of Wales, Aberystwyth. Khalerlee, J. (1969) The application of some data processing techniques to the interpretation of geochemical data. Unpub. Ph.D Thesis, Univ. of London. Lam Shang Leen, K.C.Y. (Pers. Comm.) AGRG - 1971. Lepeltier, C. (1969) A simplified statistical treatment of geochemical data by graphical representation. Econ. Geol., v.64, No.5, p.538-550. Lewis, W.J. (1967). Lead mining in Wales. Univ. of Wales Press, Cardiff. Manning, W. (1959) The Parys and Mona mines in Anglesey, in the future of non-ferrous mining in Great Britian and Ireland, Inst. Min. Metall., Lond. ti Meyer, W.T. and Lam Shang Leen, K.C.Y. (1973) Microwave induced argon plasma emission system for geochemical trace analysis, Proc. Fourth Int. Geochem. Explor. Symp. 1972. Inst. Min. Metall., Lond. Meyer, W.T. (1969) Uranium in lake water from the Kaipokoh Region, Labrador. Quat. of the Colorado School of Mines, v.64, No. I, P.377-394. 41. Miesch, A.T. (1967) Theory of error in geochemical data. Prof. Pap. US geol. Surv. 574-A, 17 P. Mitchel, R.A. (1968) A semiquantitative study of trace elements in pyrite by spark source mass spectroscopy. Nosk. Geol. Tidbskr., 48, p.65-80. Ministry of Agriculture, Fisheries and Food (1970) Modern ■■• farming and the soil, Agric. Adv. Council., London, 119 p. Mohr, P.A. (1955) A geochemical study of the Lower Cambrian manganese shale group sediments of the Harlech Dome. Unpub. Ph.D Thesis, Univ. of Manchester. Murchison, R.E. (1839) The Silurian System. John Murrary, London. Newman, E. and Foster, R. (1968) internal report on direct reading spectrograph, AGRG. Nichol, I.; Thornton, R.F.; Webb, J.S.; Fletcher, W.K.; Horsnail, R.F.; Khaleelee, J.; Taylor, D. (1970) Regional geochemistry of the Denbighshire area. Rep. Inst. Geol. Sci. 70/8. Nichol, I and Henderson-Hamilton, J.C. (1965) A rapid quantitative spectrographic method for the analysis of rocks, soils and stream sediments, Trans. Inst. Min. Metall., Lond. v.Z, p.955-961. Philips, W.J. (1970) The mechanical effect of hydrothermal solutions with reference to the mineralized normal faults and Breccia zones of Cardiganshire (unpublished) Pringle, J. and Neville-George, N.T. (1948) British regional geology, South Wales. Roberts, B. (1969) The Llwyd Mawr ignimbrite and its associated volcanic rocks in the Pre-Cambrian and Lower Paleozoic rocks of Wales. Univ. of Wales. Press, p.337-356. Roberts, E. (1958) The County of Anglesey, Soils and agriculture. Mem. Soil Survey of Great Britain. Rodgers, T.A. (1953) Geology of the Pb-Zn field of northwest Cardiganshire. Unpub. M.Sc. Thesis. Univ. of London (IC). Rowland, M.M. (1965) Geochemistry of some South Wales coals. Unpub. Ph.D. Thesis. Univ. Coll. of Wales, Swansea. Sawyer, R.A. (1963) Experimental Spectroscopy. Schellman, G.A. (1939) Applied geology at Haleyn district United Mines Ltd., Trans. Instn. Min. Metall., Lond., 48, 585-650. Shackleton, R.M. (1969) The Pre-Cambrian of North Wales in the Pre-Cambrian and Lower Paleozoic rocks of Wales. Univ. of Wales Press. p.1-22. Sherlock, R.L. (1947) The permo-Triassic Formations. Hutchinson, London, 367 p. Smith, B. (1922) Lead and zinc ores in the Carboniferous rocks of North Wales Resources Mem., Vol. XIX, Geol. Surv. of Great Britain (IGS): Smith, B. and Neville-George, N.T. (1961) British Regional Geology, North Wales. Geol. Surv. of Great Britain (IGS) Stanton, R.E. (1966) Rapid methods of trace element analysis for geochemical applications, Edward Arnold. Stevens, R.E. (1960) Second report on a cooperative investigation of the composition of two silicate rocks. U.S. Geol. Surv. Bull., 1113, 1-126 p. Taylor, D. (1968) The interpretation of lead and zinc stream sediment anomalies related to contamination and mineralization in the United Kingdom. Unpub. Ph.D Thesis, Univ. of London. Tennant, W.C. and Sewell, J.R. (1969) Direct reading spectro- chemical determination of trace elements in silicates in- corporating automatic background and matrix corrections, Chem. Geol., U.S. p.135-142. Tennant, C.B. and White, M.L. (1959) Study of the distribution of some geochemical data, Econ. Geol., v.54, p.1281-1290. Thomson, I. (1971) Regional geochemical studies of black shale facies in the particular references to trace element disorders in animals. Unpub. Ph.D Thesis, Univ. of London. Thomas, T.M. (1956) Mineral wealth of Wales and its exploitation, Oliver and Boyd, Edinburgh. Thomas, H.H. and Cox, A.H. (1924) The volcanic series of Trefgarn, Roch, and Ambleston (Pembroke) Quart. J. Geol. Soc. Lond. No. 320, 80, 520-548. Thompson, M. and Howarth, R.J. (1973) The rapid estimation of precision by duplicate determinations, The Analyst, Vol. 98, No. 1164, p.153-160. Thompson, M. (Pers. comm.), AGRG 1972 Thomspon, M. (Pers. comm), AJAX computer program, AGRG - 1972. Turekian, K.K. and Wedepohl, K.H. (1961) Distribution of the elements in some major units of the Earth's crusts. Bull. Geol. Soc. Am., v.72, p.175-192. Webb, J.S.; Nichol, I; Thornton, I. (1968) The broadening scope of regional geochemical reconnaissance. Internat. Geol. Congr., '23rd, Prague, v.6, p.131-147. Webb, J.S. (1959) Notes on geochemical prospecting for lead-zinc deposits in the British Isles. In the future of non-ferrous mining in Great Britain and Ireland: London, Inst. Min. Metall., Paper 19, p.419-436. Wells, A.K. (1925) The geology of the Rhobell Fawr Dist. (Merioneth). Quart. J. geol. Ass, Lond., No. 324, 81; p.463-538. Wheatley, C.J. (1971) Aspects of metallogenesis within the Southern Caledonides of Great Britain and Ireland, Trans. Inst. Min. Metall., 80, Sec. B, 211-223. Williams, A. (1969) Ordovician faunal provinces with reference to Brachiopod distribution : in the Pre-Cambrian and Lower Paleozoic rocks of Wales. Univ. of Wales Press, p.117-154. Williams, H. (1927) The geology of Snowdon (North Wales). Quart. J. Geol. Soc. Lond. No 331, 83, 346-431. Wood, A. (1969) Editor, Symposium on the Pre-Cambrian and Lower Paleozoic rocks of Wales. Univ. of Wales, Cardiff. Young, R.D. (1971) The interpretation of regional geochemical patterns in Northern Ireland. Unpub. Ph.D Thesis, Univ. of London. 9. GEOLOGICAL MAP OF WALES 1-2 9 JURASSIC TRIASSIC CARlIONIFP:ftOUS o c2 .•.• ~.. c 1 DEVONIAN 5 ~:::: ~ •. : ~.:: SILURIAN 4 ~b5 ~bl-3 ORDOVICIAN Co oj .1-3 CAMI'UAN X PRE-CAMBRIAN ~ Igneo\ll rocks T R EXTRUSIVE A ++++ ++ G-F INTRUSIVE iii D-H PROJECT '4 A.G.R.G. , 5 10 5 0 miles 10 20 .. .. 1 , , 6 , 10 5 0 Kms.10 20 30 4 FIGURE 2.2 16. GLACIAL FLOW IN WALES FLOW OF LOCAL ... WELSH ICE Jl'LOW OF IRISH ---- SEA ICE , -, EX TENSION ~EOF C~ IIUSH SEA § 1000 - 2000 ft. _ ABOVE 2000 fl. ""OJECT" A.G.R.G. 5 0 mi.'15 10, 20, _ _ 10~,-:i, =::::'=-~;'~~i-"::';'.-3~ 10, 5, 0' Kms. 16 20 FIGURE 2.3 18. PREDOMINANT TYPES of ROCK _AO BLACK SHALE S IIIIIIIIJ A 1 CLAYS A3 MUDSTONES t==-3 AND SHALES SLATES "ND BAS GREYWACKES FRIABLE OB2 SANDSTONES HARD B'2· BB3.... SANDSTONES [: : : ;] B4 QUARTZITES MASIVE m e4 LIMESTONES A1 1/'/20 GNEISS VOLCANIC ROCK G INTRUSIVES PROJECT " A. G.R. G. ~------~------~------~~~------~~------~~~~~~~~----~ 10 S o miles 10. 20 , , 10 5 o Kms.10 20 30 FIGURE 2.4 23. MAP WALES ANTICLINE SYNCLINE FAULT THRUST FA ULT 0. miles 10. 20 , , ,. 10 Kms.10 20 30 FIGURE 31. DRAINAGE MAP OF WALES ",-- MAIN WATER PARTINGS MAIN CATCHMENT AREAS 1 CONWAY 2 CLWYD 3 DEE 4 GLASLYN DWYRYD 5 MAWDDACH , DO'ln 7 SIYERN • ""liDO&. - YSTWYTH - AIRON , TEl'l 10 TYWI 11 WYE 12 LUGG - TEME 13 CL!DDAU 14 TAF 15 GW[NDRAETH l' LOUGHOR 17 TAWP: l' NUTH - AYAN . It TAFF - ELY - THAW 20 RHYMN[Y - EBBW 21 USK 22 OGMORE PROJECT '4 A.G.A.G 10 5 0 miles 10 20 k .. I I I , 'I , £ , , 1 5 o Kms. 10 2 30 20 FIGURE 2.8 I 33. SOIL MAP OF WALES KEY IN TABLE 2.4 0 o 0 0 o 0 0 0 o 0 Al ~ B2 0 B3 ~ 85 86 -E::l 87 C8 -~ C9 0 Cl0 ~ C11 PltOJ!CT S4 A.G.R.G. , 4 10 5 o, miles 10 20 k aI p" : 10 5 0 Kms.10 20 30 FIGURE 2.9 37. BASE - METAL MINING SITES • COPPE A MINES o LEAD- ZINC MINES (I) LEAD - ZINC - SILVER MINES • LEAD - ZINC - COPPE" MINE e GOLD - COPPER MINES MINING DISTRICS 0 00 PA!US-MONA • II .ETHESDA • 01'" III LLANRWST 00'0 IV LLANJrAIR-TALHAIRN- • • LLANSANNAN • v, VG.b.c HOLVWfLL- HALKYN- MINE!'" o. Vb i% VI SNOWDONIA- LLANLLHNI • VIn 0 Vc1' V II LUNENGAN •• VIII TRAWSFYNVDD- DEUDRAET • H U G.b HULECH DOME X LLANYNGON XI DINAS MAWDDY {X 0 XII EAST of CARDIGANSHIRE 0 0 X III WEST 01 MONTGOMERYSHI 0 0 00 X! • 0 XIV CWMYSTWVTH XV LLANDOVERY XVI LAMPETER 0 XYII PUMPSAINT XVIIJ LLANF YRNA CH XIX CARMARTHEH XX RISCA-LLANTRISANT- BRIDGE NT PROJECT" A.G.R.G. XIV o o o ~ o o 1:.> 0cJ' 00 • 0 (:J" XVI 0 (J) 0 0 0 o c9 0 0 ,o 080 e XYU o o XV ~ 0 8 XYIIJ o • o o o o Q:) 0 o o o o o o .10 5 0 miles 10 20 log , .. .. I I I 10 5 0 Kms.IO 20 30 20 FIGURE 3.1