The Geochemistry of Some Manganese Nodules and Associated Pelagic Deposits

Home , Birnessite, Hausmannite, Jacobsite, Psilomelane

THE GEOCHEMISTRY OF SOME MANGANESE NODULES AND ASSOCIATED PELAGIC DEPOSITS.

David Spencer Cronan

A thesis submitted for the degree of Doctor of Philosophy in the University of London

Department of Geology, Imperial College of Science and Technology. March, 1967. (±)

ABSTRACT

Manganese nodules and their associated pelagic sediments from diverse localities in the Pacific and Indian.Oceans have been analysed for Mn, Fe, Ni, Co, Cu, Pb, Ba, Mo, V, Cr, Ti, P, H2O and CaCO3. The mineralogy, petrography, internal structures, and sub- surface distribution of the nodules have also been investigated.

Nodules are as abundant in the upper two metres of the sediment, excluding the surface layer, as at the surface. Evidence suggests that some nodules may form in-situ within the sediment.

Optical and electron microprobe techniques have been used to examine the petrography, internal composition and structure of the nodules. Replacement of the cores and post-depositional segregation of elements within the crusts is indicated.

The principal minerals in the nodules are todorokite and birnessite. Variations in their abundance in nodules from different areas and depths have been found. The causes of these variations are discussed.

Element abundances and associations in nodules and sediments have been derived using an I.B.M. 7090/1401 computer. Element variations with depth have been found in the nodules., Compositional variations within single nodules, between nodules from the same site and at different depths in single sediment cores, and between nodules from closely related sites,have been investigated.

Regional variations in the composition of nodules are similar in both the Pacific and Indian Oceans. They differ from the variations found in the sediments. The former depend mainly on (a) the availability of continental, extrusive volcanic or exhalative volcanic sources of elements and (b) the environment of deposition largely governed by depth. Similarities are observed between regional and local variations in nodule composition and it is considered that similar factors affect each. ACKNOWLEDGEMENTS

The work presented in this thesis was carried out during the period October 1964 to February 1967 at the Applied Geochemistry Research Group of Imperial College. The project was suggested by Professor J.S. Webb and was under the supervision of Dr. J.S. Tooms.

Most of the material used in this study was supplied by the Scripps Institution of Oceanography, University of California. I am particularly grateful to Professor H.W. Menard and Mr. W. Riedel for their great assistance, advice and encouragement throughout this project. I am also grateful to Professor Carl Hubbs for allowing me to participate in S.I.O. cruise MV-65-1 in the East Pacific and for provid- ing ship time for the collection of nodules from the Mexican continental borderland. Thanks are also due to Miss.P. Helms and Mr. T. Walsh for practical assistance in sampling se-I- iment cores.

I also wish to acknowledge with gratitude the practical assistance and advice given to me by the following:- Dr. J.D.H. Wiseman, British Museum, Natural History, who also provided some nodules from the Challenger collections.

Dr.J. Cann, British Museum, Natural History.apd recently of the department of Mineralogy and Petrology, Cambridge, who, in addition, supplied the nodules from area 4c of the Carlsberg Ridge collected by R.R.S. Discovery. (iv)

Dr. A.S. Laughton, National Institute of Oceanography, Surrey, who was principal scientist on cruise 11 of R.R.S. Discovery in the North Atlantic Ocean and who also provided data on area 4c.

Dr.J. Mero, Ocean Resources Inc. La Jolla, California.

Dr. P.L. Bezrukov, Institute of Oceanography, Moscow, who presented several nodules collected by R.V. Vityaz in the Indian Ocean.

Dr. D.F. Hewett, U.S.G.S., Menlo Park, California, for a sample of well crystalline todorokite.

Dr. S. Landergren, Marine Laboratory, University of Miami, for a red clay standard.

Sincere thanks are also due to many members of Imperial College for advice and assistance including:- Dr.I.Nichol, Mrs.A.Cole and Mr.R.Berlin, Mr. R. Stanton, Dr. E. Newman, Mrs. A. Hardwick, Mr. C. Dixon, Mr. S. Haggerty.

Particular thanks are given to Mr. Ray Curtds and Mrs.S. Bird for their painstaking assistance in the X-Ray Diffractometry and to Mr.T.Kelly for conducting the electron microprobe analyses. (v)

Mr.J.Gee and Miss M.Doe assisted in reproducing diagrams.

Miss J. Somers typed the manuscript.

The work was supportedbYaN.E.R.C. research student- ship for which I am most grateful. (vi)

CONTENTS Page ABSTRACT (i) ACKNOWLEDGEMENTS (iii) CONTENTS (vi) LIST OF PLATES (xiii) LIST OF FIGURES (xv) LIST OF TABLES (xix) INTRODUCTION

PART ONE 5

Chapter 1 SURFACE AND SUB-SURFACE CONCENTRATION

AND DISTRIBUTION OF MANGANESE NODULES 6 Introduction 6 Surface distribution and concentration 7 Sub-surface concentration and distribut- icn. 10 Discussion 15 Chapter 2 DESCRIPTION, PETROGRAPHY AND

STRUCTURE OF NODULES 19 Description 19 (i)Size 20 (ii)Shape 20 (iii)Internal Form 21 (iv)Cores 22 Petrography and Structure 23 (i)Petrography and structure of nodule cores. 24 (ii)Petrography and structure of nodule crusts 31 Discussion 42 (vii) Page Chapter 3 ELECTRON MICROPROBE ANALYSIS OF MANGANESE NODULES 46

Analytical methods 46 (i)Sample Preparation 47 (ii)Instrumental Methods 47 Results 49 (i)Sample 5133.7 50 (ii)Sample 5179.1 54 (111) Sample 2P50 58 (iv) Other Samples 61 Discussion 68

Chapter 4 THE MINERALOGY OF MANGANESE NODULES 75 Part 1 THE MANGANESE MINERALS Introduction and Previous work 75 Methods 80 (i)X-Ray Diffraction 80 (ii)Heating Experiments 81

Results 81

(i)Mineral Identification 81

(ii)Heating Experiments 82

(iii)Mineralogical variations 89

Discussion 92

Part 2 OTHER MINERALS 94 Introduction 94 Detrital Feldspar Analysis 95 Results and Discussion. 97 (viii) Page

PART. TWO

Section 5.1 INTRODUCTION 100 Section 5.2 DATA PROCESSING 101 Section 5.3 ELEMENT ABUNDANCES 103

(i) Element dispersion patterns 103 a)Manganese nodules 103 b)Pelagic sediments 106 c)Conclusions 108 (ii) Abundances in Manganese Nodules108 (iii) Abundances in Pelagic Sedimentslll (iv) Enrichment Factors 116 Section 5.4 ELEMENT ASSOCIATIONS 120

(i)The relationship between 120 nodule composition and mineralogy. (ii)The relationship between 121 nodule composition and depth. (iii)Inter-element associations. 124 a) Variation diagrams 129 b) Correlation Coefficients 138 i)Manganese nodules 138 ii)Pelagic sediments 141 c) Factor Analysis 144 i)Manganese nodules 145 ii)Pelagic sediments 149 d) Conclusions. 153

(ix) Page

Section 5.5 DISCUSSION OF ELEM.= ASSOCIATIONS AND ABUNDANCES 155

(i)Manganese and Iron 155 (ii)Nickel and Copper 156 (iii)Cobalt and Lead 157 (iv)Vanadium, Chromium and 160 Titanium. (v)Molybdenum and Barium 162 (vi)Summary and conclusions 164

Section 5.6 COMPOSITIONAL VARIATIONS WITHIN SINGLE NODULES :166

(i)Nodule 5133.1 167 (ii)Nodule 5138.17 167 (iii)Conclusions. 173

Section 5.7 COMPOSITIONAL VARIATIONS BETWEEN NODULES FROM THE SAME SITE 175 (i)Morphologically similar 175 nodules (ii)Morphologically dissimilar 177 nodules (iii)Discussion 179 (x) Page

Section 5.8 COMPOSITIONAL VARIATIONS BETWEEN NODULES AT DIFFER- ENT DEPTHS IN SINGLE SEDIMENT CORES 180

Section 5.9 COMPOSITIONAL. VARIATIONS BETWEEN NODULES FROM ADJACENT SITES 183

Section 5.10 INTER-OCEAN VARIATIONS IN THE COMPOSITION OF NODULES AND SEDIMENTS 187

Section 5.11 REGIONAL GEOCHEMISTRY 192 a) COMPOSITIONAL VARIATIONS 193 WITHIN THE PACIFIC OCEANS (1) Topography of the Pacific Basin 193

(ii)Manganese nodules 195

(iii)Sediments 209

b) COMPOSITIONAL VARIATIONS WITHIN THE INDIAN OCEAN 214 (i)Topography of the Indian Ocean Basin. 214 (ii)Manganese Nodules 216 (iii)Sediments 228

c) SUMMARY OF REGIONAL GEO- CHEMISTRY AND COMPARISON WITH PREVIOUS WORK. 229

(xi) Page

Section 5.12 DISCUSSION OF REGIONAL GEOCHEMISTRY 235

(i)Regional variations in the Composition of Sediments 24.0 (ii)Regional variations in the composition of manganese nodules 244 a)Manganese 245 b) Iron 248 c)The Minor Elements 250 Section 5.13 MANGANESE NODULES FROM THE CARLSBERG RIDGE 255

(i)Description of the samples and sample sites 255

(ii)Results 263

(iii)Discussion 264 a) Variations between sites 264 b) Variations within one site 268 Section 5.14 NOTE ON SOME pH AND Eh DETERMINATIONS ON ATLANTIC SEDIMENT CORES 271

(i)Introduction 271 (ii)Methods 271 (iii)Core Description and results 273 (iv)Discussion 276 (xii) Page

DISCUSSION 279

APPENDIX 1

ANALYTICAL TECHNIQUES 293

(i)Sample Preparation 294 (ii)Instrumental Methods 295 a)Optical Spectrography 295 b) X-Ray Fluorescence 300 Spectrography (iii) Wet Analytical Methods 302

a)Colorimetric Analysis 302

b) Titrimetric Analysis 303 (iv) Discussion 303

APPENDIX 2

ANALYTICAL RESULTS 308 (xiii) Page

LIST OF PLATES

Plate 1 Illustrating internal macro-and micro structures in manganese nodules. 27 Plate 2 Thin sections of parts of the core of nodule 5138.24 and the crust of nodule 5136.1. 30 Plate 3 Photomicrographs of segregations in nodule 5133.7. 34 Plate 4 Photomicrograph5 of sections of manganese nodules. 36 Plate 5 Photomicrographs of parts of the crusts of manganese nodules. 38 Plate 6 Photomicrographsof the internal structures of the segregations in the crusts of manganese nodules. 40 Plate 7 Electron beam-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of manganese nodule 5133.7 x 250. 52 Plate 8 Electron beam-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of nodule 5179.1. x 250. 57 Plate 9 Electron beam-scanning photographs of back-scattered electrons and selected K radiations from a section

of nodule 2P50. x 250. 60 Plate 10 Electron beam-scanning photographs of back-scattered electrons and characteristic K radiations from sections of nodules 5133.1 and 5179.1. x 250. 63 (xiv) Page

Plate 11 Electron beep-scanning photographs of back-scattered electrons and characteristic K radiations from a section of nodule 5133.1. x250 65 Plate 12 Electron beam-scanning photographs of back-scattered electrons and characteristic K radiations from a section of nodule 5179.1. x 1000. 67 Plate 13 Underwater photographs of manganese nodules at station 5132 on the Carlsberg Ridge. 260 Plate 14 Underwater photographs of manganese coated submarine volcanics at station 5137 on the Carlsberg Ridge. 262 (xv) Page

LIST OF FIGURES

Figure 1.1 Map showing sample sites in the. Pacific Ocean. 1.2 Map showing sample sites in the Indian Ocean. 9 1.3 Histograms showing the distribution of nodules in gravity cores. 14 1.4 Histograms showing the distribution of nodules in piston cores. 14 4.1 D.T.A. curve of a Loch Fyne nodule. 86 4.2 Variation diagrams showing the effect of heat on the 7.1 and 9,7A X-ray 87 peaks in manganese nodules. 4.3 Diffractometer trace illustrating the effect of heat on the powder pattern of nodule Mag Bay A.35. 88 4.4 Diagram of an envelope surrounding_ reported values of A219- (131 and 131) using Cu K 0( radiation, for the plagioclase series. 96 (from Peterson and Goldberg 1962) 4.5 Map showing the geographic distribution of feldspar:,lites in the South Pacific Ocean. 96 (from Peterson and Goldberg 1962) 5.1 Histograms showing the distribution of elements in manganese nodules. 105 5.2 Histograms showing the distribution of elements in pelagic sediments. 107 (Figs, 5.3 to 5.14 apply to nodules only). 5.3 Variation diagram of Ni with depth. 125 (xvi) Page

5.4 Variation diagram of Cu with depth. 126 5.5 Variation diagram of Co with depth. 127 5.6 Variation diagram of Pb with depth. 128 5.7 Variation diagram of Ni with Mn. 130 5.8 Variation diagram of Cu with Mn. 131 5.9 Variation diagram of Mo with Mn. 132 5.10 Variation diagram of Mn with Fe. 133 5.11 Variation diagram of Ti with Fe. 134 5.12 Variation diagram of L.O.I. with Fe. 135 5.13 Variation diagram of V with Fe. 136 5.14 Variation diagram of Co with Fe. 137 5.15 Plot of variation of selected elements across nodule 5133.1. 169 5.16 Diagram illustrating the variation in element content from the core to the surface of nodule 5138.17. 172 5.17 Diagram illustrating the variation in element content between nodules from site 5138. 176 5.18 Diagram showing a comparison of the composition of the small, with the large, nodules, from station 5133. 178 5.19 Diagram showing a comparison of the composition of the small nodules from station 5133 with those from station 5136. 184 5.20 Map showing the topography of the

Pacific Basin, 194

(xvii) Page

5.21 Map showing the regional variation in the Mn content of Pacific nodules. 196 5.22 Map showing the regional variation in the Fe content of Pacific nodules. 197 5.23 Map showing the regional variation in the Ni content of Pacific nodules. 199 5.24 Map showing the regional variation in the Cu content of Pacific nodules. 200 5.25 Map showing the regional variation in the Co content of Pacific nodules. 202 5.26 Map showing the regional variation in the Pb content of Pacific nodules. 203 5.27 Map showing the regional variation in the Mo content of Pacific nodules. 205 5.28 Map showing the regional variation in the V content of Pacific nodules. 206 5.29 Map showing the regional variation in the Ti content of Pacific nodules. 207 5.30 Map showing the regional variation in the Ba content of Pacific nodules. 208 5.31 Map showing the regional variation in the Mn content of Pacific sediments. 210 5.32 Map showing the regional variation in the Fe content of Pacific sediments. 211 5.33 Map showing the topography of the Indian Ocean Basin. 215 5.34 Map showing the regional variation in the Mn content of Indian Ocean nodules. 217 5.35 Map showing the regional variation in the Fe content of Indian Ocean nodules. 218 5.36 Map showing the regional variation in the Ni content of Indian Ocean nodules. 219 (xviii) Page

5.37 Map showing the regional variation in the Cu content of Indian Ocean nodules. 220 5.38 Map showing the regional variation in the Co content of Indian Ocean nodules. 222 5.39 Map showing the regional variation in the Pb content of Indian Ocean nodules. 223 5.40 Map showing the regional variation in the Ti content of Indian Ocean nodules. 224 5.41 Map showing the regional variation in the V content of Indian Ocean nodules. 225 5.42 Map showing the regional variation in the MO content of Indian Ocean nodules. 226 5.43 Map showing the regional variation in the Ba content of Indian Ocean nodules. 227 5.44 Map showing nodule composition zones within the Pacific Ocean. 231 5.45 Map showing the bathymetry of area 4c on the Carlsberg Ridge. 256 (from Laughton 1967). 5.46 Sketch of bathymetry at station 5133 on the Carlsberg Ridge. 258 5.47 Sketch of bathymetry at stations 5136 and 5138 on the Carlsberg Ridge. 258 5.48 Map showing the location of the North Atlantic sediment cores on which pH and Eh determinations were conducted. 272 (xix) Page

LIST OF TABLES

Table 1.1 Length3of gravity and piston cores and numbers of nodules collected. 11 1.2 Comparison of numbers of nodules at surface and at depth. 12 3.1 Analysis of nodule 5133. 54 4.1 Powder Patterns of manganous manganite and 6' Mn02. 76 4.2 Comparison of the power patterns of the principal phases suggested as being present in manganese nodules. 78 4.3 Powder patterns of selected manganese nodules. 83 4.4 Effect of heat on the X-ray powder peaks of nodule MV-65-1-3S. 90 4.5 Composition of plagioclases in pelagic sediments in terms of the separation of the 131 and 131 X-ray peaks. 97 4.6 Composition of plagioclases in the acid insoluble residue of some nodules. 98 5.1 Skew of elements in manganese nodules, pelagic clays and pelagic carbonates using arithmetic and log data. 104 5.2 Element abundances in 139 nodules from the Pacific and Indian Oceans. 109 5.3 Comparison of average compositions of manganese nodules. 110 5.4 Element abundances in 188 pelagic sediments from the Pacific and Indian Oceans. 112

(xx) Page

Table

5.5 Element abundances in 33 surface pelagic clays. 5.6 Element abundances in 31 surface pelagic carbonates. 5.7 Comparison of average compositions of pelagic sediments. 5.8 Average composition of sediments adjacent, and not adjacent, to a nodule. 115 5.9 Enrichment of elements in manganese nodules over their concentrations in other rock units. 117 5.10 Average composition of nodules rich in todorokite and birnessite. 121 5.11 Relationship between the average composition of surface nodules and their depth of deposition. 122 5.12a Values of the correlation coefficient for elements in nodules and depth. 123 5.12b Correlation matrices for elements in manganese nodules. 140 5.13 Correlation matrices for elements in pelagic clays. 142 5.14 Correlation matrices for elements in pelagic carbonates. 143 5.15 Rotated factor matrix for elements in manganese nodules. (Arithmetic Data). 147 5.16 Rotated factor matrix for elements in manganese nodules. (Log Data). 148 5.17 Rotated factor matrix for elements in pelagic clays (Arithmetic Data). 150 (xxi) Page

Table 5.18 Rotated factor matrix for elements in pelagic clays.(Log Data). 151 5.19 Rotated factor matrix for elements in pelagic carbonates.(log Data). 152 5.20 Variation in composition across nodule 5133.1. 168 5.21a Variation in composition across nodule 5138.17. 170 5.21b Variations in composition across nodule 5138.17. 171 5.22 Analyses of two manganese crusts from the North Atlantic Ocean. 185 5.23 Abundances of elements in manganese nodules from (a) the Pacific Ocean, and (b) the Indian Ocean. 188 5.24 Average compositiornof pelagic sediments from the Pacific and Indian Oceans. 190 5.25 Average compositions of clay sediments from different regions within the Pacific and Indian Oceans. 213 5.26 Average compositionsof manganese nodules from different regions within the Pacific and Indian Oceans. 233 5.27 Location of sample sites and sizes of nodules collected in area 4c. 257 (xxii) Page

APPENDIX

A 1 Analysis of hacksaw blade 295

A.2 Precision of spectrographic analyses 298 A 3 Comparison of present analyses of nodules with those of Willis and Ahrens(1962). 299 A 4 Comparison of colorimetric and spect- trographic determinations of Ni and Cu 299 A 5 Comparison of iron and manganese determinations by X.R.F. titrimetric and

colorimetric techniques. 302 1

INTRODUCTION

Manganese nodules have been the subject of considerable interest since they were first collected during the Challenger Expedition (1873-76), Murray and Renard (1891). They have been found in all the major oceans and consist essentially of oxides of manganese and iron usually surrounding.a core of either terrigenous, volcanic or organic material.

For many years after their discovery they were the subject of only occasional investigation. However, with the development of efficient depth sounding, coring and, dredging devices, during and after the Second World War, many new samples were obtained. Much of this work was undertaken by the Scripps Institution of Oceanography during numerous cruises in the Pacific Ocean, and the writer is indebted to this institution for supplying the bulk of the samples studied during the course of the present work. ,

With the greater abundance of samples available for research, investigations of nodules by many authors have appeared. 2

Most of these have been of a fundamental nature but recently the possible economic potential of these bodies has prompted investigations by a number of commercial organisations.

The basic physical and chemical characteristics of manganese nodules were established by Murray and Renard (1891) and have suffered little revision since. These authors found them to be abundant in the pelagic areas of the oceans, mainly in areas of red clay accumulation. They were found to be strongly enriched in many minor elements as well as in iron and manganese; large variations in the content of all these elements between different stations being recorded. Much of the subsequent work has concentrated on the relationship between the, major and minor elements in nodules with, in addition, mineralogical investigations by authors such as Buser and Grutter (1956) and Manheim (1965).

Within the last decade it has been recognised that the elements in manganese nodules vary on a regional scale within the Pacific Ocean, Inter--ocean .variations in their composition have also been observed. Mero (1965) has shown that within the Pacific Ocean regions exist that contain nodules hig'G in Mn, Fe, iii and Co respectively. There have, however, been few atemots to relate these variations to specific processes, this largely being the result of an absence of the relevant data.

Much of the speculation concerning manganese nodules has centred on their origin. This is really two problems; 3 their mode of formation and the sources of the elements they contain. The nodules are formed by precipitation of elements from solution, most likely in a colloidal form,(Goldberg 1954). The sources of these elements, have, however, been the subject of much controversy. Most workers have attempted to account.for their supply in terms of either submarine vulcanism, as suggested by Murray in Murray and Renard (1891), or in terms of their derivation from the continents as suggested by Renard in the same work. There are persuasive argu,..entn to support both suggestions. Recently, some workers, including Skornyakova, Andrushnhonk and Fomina (1962) and Arrhenius et al (1964) have accepted that both sources are possible, but much controversy still exists.

Many excellent reviews on the previous wort done on manganese nodules.are available. These include, Murray and Renard (1891), Pettersion(1945), Goldberg (1954), Goldberg and Arrhenius (1958), Goldberg (1961),Arrhenius (1963), Menard (1964), Mero (1965) and Chester (1965); the reader is referred to these for background information. It is not proposed to discuss previous work in detail at this stage as it.will be presented at relevant points throughout the text.

In,any consideration of the geochemistry of manganese nodules, factors other than their geochemistry have to be taken into account. Important points are their distribution both laterally and vertically within the sediment, their petrography, structure and mineralogy. In addition, it is fruitful to attempt to relate their geochemistry to the nature of the environment in which they form. 4

Many features of their environment of,deposition are imperfectly known the present time, particularly the nature of the sea water at the different sites at which they occur, However, some features are better understood or can be inferred from features that are known. Of importance in this context are the depths at which the nodules are found, the nature of their enclosing sediment, their closeness to potential sources of elements and the configuration of the areas in which they occur. In this work the geochemistry of nodules is considered in terms of these and other factors.

The first part of this thesis includes some topics of a non-geochemical nature but which are of importance in interpreting the geochemistry of nodules. The points covered include ther distribution.petrography, structure, mineralogy and internal compositional variations. Part Two includes the geochemistry of both nodules and that of their surrounding sediments, This geochemical study has been divided into firstly, a general geochemical study of both nodules and sediments using a statistical approach to the interpretation of the data, secondly, the regional geochemistry of Pacific and Indian Ocean nodules and sediments, the latter entirely uninvestigated in the pas',;, and thirdly, local variations in the composition of nodules, Throughout, emphasis has been placed on the geochemistry of nodules in terms of their environment of formation, 5

PART ONE CHAPTER 1.

SURFACE AND SUB-SURFACE CONCENTRATION AND DISTRIBUTION OF MANGANESE NODULES

INTRODUCTION The distribution of manganese nodules at the sediment surface has been investigated by a number of workers; these including Menard and Shipek (1958), Zenkevitch and Skornyakov (1961), Menard (1964) and Mero (1965), Much of the available information has been obtained by underwater photography, but "grab" sampling devices have been used by Zenkevitch and Skornyakova (1961), In addition, Mero (1965) has used the frequency of occurrence of nodules in gravity cores as a measure of their abundance at the sediment surfacer,

Information on the surface concentrations of manganese nodules is most abundant from the Pacific Ocean where, according to Mero (1965), no extensive area other than continental shelves and oceanic trenches are free of them, 7

However, according to Bonatti and Nayudu (1965), within the Pacific the distribution of manganese nodules is by no means even. Some areas have an extensive. covering while adjacent areas are almost free of them.

The distribution and concentration of nodules in the Indian Ocean is less perfectly known, This is largely due to inadequate investigation of this ocean compared with the Pacific. However, recent work during several Scripps Institution of Oceanography cruises and aboard the Russian research vessel Vityaz (Bezrukov 1962,1963) indicates that large areas of the southern Indian Ocean have surface concentrations of nodules similar to those found in the Pacific. In addition, Laughton (1967) found large local variations in the concentration of nodules in certain parts of the Carlsberg Ridge.

The majority of nodules examined in this work were obtained using coring devices and are accompanied by their surrounding sediment. Gravity, piston and free fall corers were lised. The remainder were collected by dredge and are unaccompanied by their surrounding sediment.

SURFACE DISTRIBUTION AND CONCENTRATION The surface distribution of the nodules studied is presented in Figs. 1,1 and 1.2, The majority of the samples are from the Central and South Pacific with, in addition, a limited number of samples from the Indian Ocean. FIG 1.1 Mn Nodule Sample Sites in

The Pacific Ocean

MP26 a3 4MP2511

xP169g

xT27a 411343a g xPlaeg 156: (Plilg x 2P 5 2-- x "1725pg xl.H89pg '20c 2 7p xPiotg PI51 g xPlIpg )(Play PI 39g P137g LH 90 pg x P105g

xP108pg$p xA100g x P79p

x1.113pglip

xAII6pg

xh128g

FIG 1.2 Mn Nodule Sample Sites in

Thee Indian Ocean

XBM906 Di5106 1-Di 5123 10. X i 5133/36/38

2tDi 175/79 XD2 XD127d

XW5270 „L D75d 45s D54g '11111111 Deed:

XD lop XV520 2 D66 • XD113d XV5200 444 xD130g

off li**2( As;414‘.0 XD 32. XV51/1,1) 1- 0

Examination of Fig. 1.1 shows that the nodule sample density is not constant over the whole of the Central and South Pacific. Nodules appear to be more abundant in some areas than they are in others. This is, no doubt, largely a reflection of variations in the amount of sampling in these areas. To overcome this problem the number of surface nodules in cores has-been compared with the total number of cores collected. This serves as a general guide to the concentrations of nodules in particular areas. In certain areas such as the West Central Pacific and the southern portion of the East Pacific Rise (Menard, Goldberg and Hawkes, 1964) a higher proportion of the cores contained nodules than in other areas. Thus in these areas the surface concentration of nodules is higher than elsewhere. Insufficient samples are available from the Indian Ocean fora rimilar exercise to be undertaker there.

SUB-SURFACE CONCENTRATIONS AND DISTRIBUTION Various workers, including Menard and Shipek (1958), Skornyakova (1960), Menard (1964), Mero (1965) and Bender et al (1966), have reported the presence of buried manganese nodules in pelagic sediments. However, until recently, insufficient. data have been available to comment on their distribution. During the course of the present work data on the distribution of nodules in one hundred and thirteen sediment.cores from the Pacific Ocean have been accumulated (table 1.1), These cores, consisting of eighty-four gravity cores and twenty-nine piston cores, all contained nodules at one or more horizons, 11

Type of No.of No.of Av-Core Min.core Max. No. of Core Cores Cores length length core Nodules stopped exc.col. exc.col. length at surf- 3 3 a b ace. cm cm cm surface depth

Gravity 84 14 105 10 181 75 35 Piston 29 2 496 98 994 16 29

Total: 113 16 213 10 994 91 64

Table 1.1: Length of Gravity and Piston Cores and number of nodules collected.

In both types of core a relatively large number of nodules were found within the sediment as well as at the surface. A.higher proportion of nodules in piston cores were buried, than in gravity cores, this most probably being a reflection of the greater powers of penetration of piston coring devices. Several of the cores -ontained nodules at more than one horizon, although in the majority only one nodule was present. The maximum number of nodules found in a single core was five, including one at the surface,.but this core was collected near a fault scarp where, according to Heath and Moore(Scripps Institution of Oceanography, personal communication 1965) slumping of the sediment may have occurr071. That the total number of nodules found at depth was not greater is considered to be at least partly due to a number of the cores being stopped by a surface or near surface nodule. 12

The concentration ::'atio of buried to surface nodules per unit length of core has been derived from a study of cores penetrating to specific depths. This ratio has been calculated for piston and gravity cores separately, (table 1.2).

Depth No.of No.of Nodules No.of Nodules Col.4/ cm Cores on surface below surface Col.3. (a ) Gravity Cores 0-50 61 52 15 0.29 0-100 41 35 19 05 (b)Piston Cores 0-100 26 13 5 0.38 0-200 26 13 12 0.92 0-300 22 10 19 1.90 0-400 20 9 18 2.00

Table 1.2: Comparison of numbers of nodules at surface and at depth.

From table 1.2 it is evident that nodules in the upper two to three metres of the sediment are approximately equal in number to those at the surface. This is in agreement with the work of previous authors. Menard (1964) found in gravity cores from the Pacific, that the concentration of nodules in the first metre of sediment is approximately half that found at the surface. In addition, Bender et al (1966) found the ratio of nodules at the surface to those in the first metre of forty-eight gravity cores to be 1.7, slightly lower than Menard's figure. 13

The surface to depth ratio found in the upper metre of gravity cores in this work is 1.8. Thus it can be seen that a large measure of agreement exists between the ratio of surface to buried nodules in the upper metre of pelagic sediments.

It is of interest to note that, based on the model of manganese nodule formation presented by Bender et al (1966),namely the precipitation of manganese from sea water at the sediment surface, the predicted ratio of nodules at the surface to those in the first metre of sediment is 7, The fact that three independent determinations show excellent agreement for a ratio considerably removed from that predicted would perhaps indicate that this model is in error and there is a source of manganese additional to that postulated by these authors.

The distribution of nodules within the cores examined is presented in Figs. 1,3 and 1.4 as a ratio of the number of nodules collected from a given depth range, to the number of cores that penetrated to that depth. It is assumed that the corers were vertical on entry and remained so. No nodules were encountered in the piston cores below 486 cm. even though over a third of those examined were greater than this in length. However, nodules have been,found at depths greater than those reported in this work, one core collected in the Scotia Sea containing nodules down to a depth of about ten metres, (H.LMenard; Scripps, Institution of Oceanography, personal communication, 1966).

0-8

0-7 •

s 0.6 - le

du ou 0.5

O f no o o 0-4

No. 0.3 ■

0.2 r

0.1 r 61 8 8 8 8

S 0 150 Depth. cm Fig. 1.3 Illustrating distribution of nodules in gravity cores. (The numbers at the foot of each column refer to the actual number of nodules found in each depth interval. The first column marked DS" refers to surface nodules only.)

s le O 0.4 du o 3 f n 0.3 O o

No 0.2 -

0.1

14 3 3 4 3 7 3 3 1 1 1 S 0 500 Depth cm Fig. 1.4 Illustrating distribution of nodules in piston cores. (The numbers at the foot of each column refer to the actual number of nodules found in each depth interval. The first column marked "SD refers to surface nodules only.) 15

It can be seen from Figs. 1.3 and 1.4 that the distribution of nodules with depth is, in general, fairly regular. The high concentration of nodules in the 200 to 250 cm. interval in Fig. 1,4 is largely contained in the core collected where slumping may have occurrc' The dotted line in Fig. 1.4 indicates the concentration in this depth range if these nodules are excluded.

DISCUSSION The absence of nodules in any of the piston cores below 486 cm is problematic. It may be the result of an absence of nodules below this depth at the sites from which these cores were obtained. Alternatively, it could result from incomplete penetration of the corers, it being known that sediment is sometimes sucked into the lower portion of the core barrel as it is withdrawn from the sediment. In this context the observation of disturbance at the base of a proportion of the piston cores is significant. Such disturbance is most easily recognised in sediment with a definite layering or mottling and in homo- genous sediment it is not possible to readily establish the exact extent of the phenomenon.

The fairly even distribution of buried nodules, includ- in- their preferential concentration at the sediment surface, poses a number of problems when the cause of this distribution is considered, A number of theories have been proposed to account for their preferential surface concentration, and in certain cases these help to explain the observed depth distribution also. 16

Mero(1965) has suggested that the activity of burrowing organisms in reworking the sediment could be . a mechanism maintaining nodules at the surface. However, this is likely to be a fairly random procedure and would probably not affect the larger nodules.

Bonatti and Nayudu (1965) and subsequently Lynn and Bonatti (196:) have suggested that the upward migration of reduced manganese is an important factor in enriching the surface sediment in nodules. This process is undoubtedly operative in areas where reducing conditions are encountered at shallow depths within the sediment. However, all the cores examined in the present study appeared to be well oxidised throughout their lengths, In addition, there is no evidence of corrosion of the buried nodules nor did their concentration decrease with depth as would be expected if this mechanism were operative.

Bender et al (1966) have suggested that nodules grow at the surface until they reach a certain critical size, on the attainment of which they are then buried, This mechanism would account for the high surface concentration of nodules, and,perhaps also their even distribution at depth. However, the factors that influence the critical size of a nodule are largely unclear, Certainly, in vie— of the differing sizes of nodules found in some cores, they must be rather variable,

A further alternative explanation of the observed depth distribution of nodules could be that they form in situ within the sediment. 17

The manganese and other elements for this process could possibly be supplied by the alteration of buried submarine volcanics (Murray. and Renard 1891, Petterssonl945, Bonatti and Nayudu 1965), or by leaching from the sediment on alteration, this itself in,volcanic areas being largely composed of volcanic detritus, (Murray and Renard 1891, Peterson and Goldberg 1962, Griffin and Goldberg 1963). In this context it is perhaps significant that more of the buried nodules were found.in the volcanic areas of the Central and South Pacific, than in areas closer to the continents.

Removal of manganese from submarine volcanics necessitates its solution and oxidation, Manganese is largely present in the divalent state in primary minerals and on weathering will be oxidised to the quadrivalent state; Goldberg and Arrhenius (1958) suggested that this oxidation approximates to the reaction:- Mn+++ 202 = Mn02 H2O

According to Garrels (1960) the formation of Mn4+ occurs at an eH of about t5 volts at pH 8. That these conditions are satisfied on the sea floor is evinced by the abundant quadrivalent manganese found in pelagic sediments (see also section 5.14). Petrographic evidence to suggest that manganese is liberated on the alteration of submarine volcanics is presented in the next chapter.

If nodules do form within the sediment, their preferential enrichment at the sediment surface could partially result from sediment erosion. 18

Some supporting evidence for this suggestion is provided by the observation of current scour marks in bottom photographs of areas where nodules are abundant (Mero 1965). In addition, Skornyakova (1960) has commented on the marked association of nodules with abyssal hills, generally considered to be areas of more active erosion than the surrounding troughs or abyssal plains.

It is concluded that there is some evidence to suggest that nodules could form within the sediment and be subsequently exposed at the surface by erosion. This hypothesis is not presented as an alternative to the established hypothesis that nodules form at the sediment surface, but as an addition to it. 19

CHAPTER 2.

DESCRIPTION,PETROGRAPHY AND STRUCTURE OF NODULES

The nodules examined during the course of the present work show most of the features described by Murray and Renard (1891). The present samples were taken from a wide variety of localities and environments, con- sequently they tend to show a wide range of physical characteristics.

DESCRIPTION The nodules consist of a moderately soft brown- black earthy friable material which is easily crushed with moderate pressure or cut with a hacksaw. The actual hardness varies considerably, some being soft enough to be broken down with the fingers while others are somewhat harder and do not fracture unless struck by a hammer. This latter variety commonly takes a good polish on cut surfaces thus displaying the internal structures to good advantage. 20

The soft and friable nodules are the most porous. On immersing,these in water considerable volumes of air are given off, but when the more massive varieties are immers- ed.little air is released.

The external surfaces of the nodules vary somewhat in texture. Some are quite smooth and hard while others dis- play various forms of surface ornamentation. Small tubercles are quite common. On some samples these are quite hard and resist mild abrasion while on others they can be removed by rubbing with the finger. Some of the nodules have a curious mammillated,surface somewhat reminiscent of kidney hematite. When struck, these nodules fracture along the boundaries of the kidneys,

(i)Size The overall size of the nodules varies greatly. The smallest are less than 0.5 cm. in diameter while the largest are 10 cm. to 15 cm. in diameter. Much larger bodies have however been reported (Goldberg and Arrhenius 1958). Manganese coatings on volcanic rocks were also examined; these vary from a few millimetres to several c:'- ntimetres in thickness. No overall size can be given to these bodies as they are obviously fragments of larger masses that have been broken off during collection by the dredge; they were usually collected from seamounts.

(ii)Shape The shapes of the nodules vary from spherical through oval and finally tabulate forms with, in addition, numerous other irregular shapes that defy simple description, 21

Generally, when several nodules from a single site were examined, they were found to be similar in shape, but variable in size. However, at two dredge sites in the Indian Ocean two size populations of nodules occur (section 5.7 and 5.13). Some of the nodules consist of aggregates of smaller nodules which have fused together on growth. This structure is best observed in cross section where the individual smaller nodules often show the development of concentric banding.

(iii) Internal Form The concentric banding which is often regarded as typical of manganese nodules is developed with varying degrees of perfection in the samples examined. In the more massive samples numerous fine bands of an alternate metallic and earthy appearance were observed. In others the banding is much coarser, only a few individual layers being present. These layers are usually a dull earthy brown colour alternating with others of lighter hue, either light brown, grey, yellow or dull red. The lighter bands contain greater amounts of silicate material than do the darker ones, Sometimes the material of these lighter bands is indistinguishable from the surrounding sediment, while in other cases it closely resembles the core material.

In a number of the samples concentric banding is absent, These usually consist of dull earthy material and are softer and more friable than the banded forms. In addition, they are usually porous, often appearing vesicular, and are of irregular shapes. 22

In both the banded and unbanded forms there is generally a lightening of colour as the core is approached, caused by increasing amounts of silicate materials. Sometimes the boundary between the core and the outer crust is very diffuse while in other cases it is sharply defined thus facilitating easy removal of the core.

(iv) Cores The cores of the nodules examined show a great deal of variation, both in size and composition. Most cores examined consist of volcanic material in various stages of alteration; pieces of palagonite, sideromelane, pumice and clay were commonly found.

The most common core material is a white to buff clay like substance which usually contains partially altered feldspars, pyroxenes and olivines with, in addition, glass shards and pieces of palagonite. Some nodules have cores of organic matter such as fish teeth and bones. However, the volcanic cores are Quantitatively the most important.

One nodule examined showed a variety of features of interest. The core consisted of a piece of sideromelane surrounded by a thin discontinuous layer of reddish brown palagonite. This graded outwards into a whitish clay which contained segregations of manganese-iron oxides. The proportion of clay decreased as the outer layers were approached, these outer layers consisting of relatively massive banded layers of manganese-iron oxides. This nodule is important because it shows the progressive alteration of the original basaltic material and its partial replacement by manganese-iron oxides. It is rare that this sequence is seen in its entirety, but is part- , ially developed in many of the nodules examined. 23

Usually, alteration of the core material has progressed to completion and little of the original material remains.

Not all the clay cores are of volcanic origin; some consist of balls of clay indistinguishable from that com- prising the surrounding sediment. In such cases no difficulty was found in removing these cores, there usually being a sharp boundary between these and the manganese crusts. In addition, not all the volcanic material in the nodules is present in the cores. Scattered throughout the manganese phases pieces of clay and fragments of plagioclase are commonly found and one sample contained a partially altered fragment of basalt.

Some nodules have no core. Usually, when this occurs there is a slight increase in the amount of silicate material towards the centre of the nodule. In other cases there is a hole where the core should have been. The former can be explained by replacement of the core by manganese-iron oxides, while in the case of the latter the core has obviously been dissolved away after the deposition of the surrounding phases.

PETROGRAPHY AND STRUCTURE Manganese nodules from Discovery stations 5133,5136,5138, and 5179 on the Carlsberg Ridge in the North-West Indian Ocean have been examined petrographically. In addition, samples from other sites have been examined in order to establish the general applicability of the conclusions drawn from the Indian Ocean material. 24

The samples examined were chosen on the basis of the wide variety of physical characteristics they exhibit. Nodules from station 5133 are massive in appearance, contain small manganese impregnated cores and show well developed concentric banding (plate ic). Those from station 5138 contain large cores of altered volcanic material and relatively thin crusts of manganese-iron oxides (plate la). The cores of these nodules are very porous and a gradational relationship between these and the outer crusts is observed. From station 5136 massive man, anee-iron encrustatiors on altered Iroicanics were examined, and from station 5179 a piece of crust of vesicular appearance.

Petrographic investigations have been conducted using both transmitted and reflected light. The former facilitated study of the silicate phases while the latter was more applicable to the opaque minerals.

(i) Petrography and Structure of the Nodule Cores The petrography of the cores of the nodules from the North-West Indian Ocean is rather complex owing to the very fine grain size of much of the material. The main constituent of the cores of the nodules from station 5138 is a whitish to buff coloured clay, X-ray analysis of which indicated the presence.of montmorillonite (J.Cann, British Museum, Natural History, personal communication 1967). Other fine grained materials present include green chlorite and microcrystalline zeolites. These latter are often concentrated into spherulitic aggregates of fibro- radiate form, the individual fibres showing parallel extinction. 25

They also occur as cavity fillings. Coarser grained materials include plagioclase showing polysynthetic twinning.

Scattered throughout the cores of these nodules are angular fragments of palagonite (hydrated volcanic glass) (plate 2a). Palagonite is common in the cores of nodules from station 5138 and in certain nodules from other localities it constitutes the whole core. In addition, small pockets of microcrystalline calcite occur interspersed with the clays and chloritic matter.

In one of the nodules from station 5138, a fragment of partially altered basalt surrounded by manganese-iron oxides was found well away from the core (plate 2b). This fragment contains plagioclase laths of andesine composition, pyroxenes and some hornblende. The alteration that it had undergone(evinced by the sodic nature of the plagioclase and the development of hornblende) is similar to that found by Matthews et al (1965) in basalts from an adjacent area believed to have been subjected to low grade hydrothermal metamorphism. In a number of nodules from the same station fairly large crystals of labradorite are scattered throughout the manganese-iron phases, again away from the cores.

Interspersed with the silicate core materials in the nodules from station 5138 are numerous small segregations of manganese-iron oxides. In addition, fibrous dendrites of manganese oxides occur. The segregations sometimes appear to be concentrated into vesicle like forms with a dark outer rim, a lighter inner rim and a centre filled with clay like material (plate lb). 26

PLATE 1 A B C D

a) Cross section of a nodule from station 5138 showing a gradational relationship between the volcanic core and the manganese crust. Size 5cm. x 7cm..

b) Photomicrograph of part of the core of nodule 5138.34, ;'):125. Note the vesicle like structures.

c)Cross section of nodule 5133.7 showing well developed concentric banding. Diameter 5.5cm.

d)Photomicrograph of part of the core of nodule 5138038, x 125.

Some segregations are just minute specks while others are well rounded and show internal banding (plate id). These segregations occur even in the innermost areas of the cores but increase in size and frequency towards the outer areas.

The overall appearance of the cores of the nodules from station 5138 is that of a palagonite tuff breccia. Palagonite tuffs l'ave been commonly reported as being associated with vulcanism and according to Nayudu (1961+) often comprise the cores of manganese nodules. Palagonite is generally considered to result from the hydration of basaltic glass. The angular nature of the palagonite fragments in the samples from station 5138 probably results from the brecciation of the original hot submarine lava in contact with sea water.

The zeolites and chlorite commonly observed in the present samples are probably the result of alteration of the palagonite, Nayudu (1964) has reported these minerals as alteration products of palagonites from both submarine and terrestrial localities, and Peacock (1926) has found them to be alteration products of palagonite in Iceland.

The presence of calcium carbonate in the majority of the samples examined is of interest. Calcium carbonate is also considered to be an alteration product of palagonite; Nayudu (1964) suggested that it is one of the last minerals formed. It is likely therefore that much of the carbonate in the present samples results from alteration. However, the principle sediment in the area where these samples were found was a calcareous ooze. 29

PLATE 2 A B

a) Thin section of part of the core and crust of nodule 5138.24. Note the angular fragments of palagonite in the lower half of the photograph x 7,5.

b) Thin section of part of encrustation 5136.1 enclosing a fragment of partially altered basalt. x 6.5

Therefore, it is possible, in view of the fragmented and porous nature of the cores of the nodules from station 5138, that some of this sediment has been incorporated into the deposit.

Examination of the cores of nodules from the other stationsin the North-West Indian Ocean reveals features similar to those already described. The cores of nodules from station 5136 contain clays and other volcanic alteration products with fragments of palagonite. The cores of nodules from station 5133 are smaller than those from station 5138 and consist of a white clay like material,in which Cann reports the presence of phillipsite (J.Cann, British Museum, Natural History, personal communication 1967). As in thA case of the nodules from station 5138 there is a gradational relationship between these cores and their surrounding crusts° However, in the nodules from station 5133 the impregnation of the cores is more advanced.

(ii) Petrography and Structure of the Nodule Crusts. Examination of the crusts of nodules from,the Carlsberg Ridge, using a reflecting microscope, reveals the presence of two principal materials. These are firstly, a hard, moderately reflecting, weakly anisotropic mineral, and secondly, a softer, isotropic phase which shows weak internal reflections.

The spatial relationships between these two phases are more or less the same in all the nodules examined. The former occurs as microscopic segregations enclosed in the latter (plates 3a, 4 and 5). 32

Electron microprobe analysis (Chapter 3) revealed that the segregations consist principally of manganese- iron oxides while the interstitial matrix material is almost free of manganese but rich in iron. This observation is supported by the examination of nodule sections etched with hydroxylamine hydrochloride. This reduces manganese oxides-but leaves iron oxides unaffected (Arrhenius 1963). In plate 3b an example is shown where the segregations have been reduced by the hydroxlamine hydrochloride attach.

In a further attempt to determine the compositional relationships between the segregations and the interstitial material nodule sections were etched with cold concentrated HC1 after the manner of Murray and Renard (1891). This dissolves both manganese and iron oxides but leaves the silicates largely unattacked. After etching, the sections were examined under the microscope. The manganese-iron oxide segregations were dark and had been strongly attacked while parts of the interstitial areas remained largely unaltered. Inserting the analyser, these showed strong internal reflections resulting in their appearing bright yellow to reddish brown in colour. Successive etchings failed to attack these phases although the segregations became further corroded. It was therefore concluded that they were silicates; they appear to be identical with the material found in the nodule cores.

Thus the combined evidence of electron microprobe examination, etching with,hydroxylamine hydrochloride and with concentrated HC1,demonstrated that the segregations consist of manganese-iron oxides and thr interstitial materials consist of iron oxides with some silicates. 33

PLATE 3 A B

a)Photomicrograph of radially elongated segregations in nodule 5133.7, x140.

b) Photomicrograph of segregations in nodule 5133.7 that have been etched with hydroxylamine hydrochloride. The dark area is the part etched.x 100.

PLATE 4 A B C D

a)Photomicrograph of part of the crust of nodule 5138.38. x 125.

b)Photomicrograph of part of the crust of nodule 5133.7, x 125.

c)Photomicrograph of part of the crust of nodule 5138.24, x 125.

d)Photomicrograph of part of encrustation 5136.1, x 125.

PLATE 5 A B C D

a) Photomicrograph of part of a concentric ring near the surface of nodule 5133.5, x 125.

b) Photomicrograph of part of the crust of nodule 5138.5, x 125.

c) Photomicrograph of internal banding within.segregations in encrustation 51791, x 125.

d) Photomicrograph of part of the crust of nodule 5138.5, x 125.

PLATE 6 A B C D

a) Phdxmirograph of internal banding within large segregations in encrustation 5179.1, x 125.

b) Photomicrograph of internal banding within a large segregation in encrustation 5136.11, x 125.

c) Photomicrograph of internal banding within clustered segregations in encrustation 5179.1, x 125.

d) Photomicrograph of internal banding within a segregation in encrustation 5136.11, x125.

The actual forms of the segregations in relation to their matrix caabe correlated with the amounts of the materials available. In nodules with a high content of , manganese relative to iron, as in those from station 5133, the segregations are large and form the centres of linked polygons of iron and silicate phases (plates 3a and 4b). In other,cases, when the proportion of manganese to iron is lower, as in nodules from station 5138 (section 5.9), the segregations are more isolated and the proportion of the matrix materials increased (plates 4a,4c, 5b and 5d).

Often the segregations are elongated in the radial plane of the nodule (i,e. their long axes point towards the nodule surface). However, this only occurs when the proportion of segregations relative to the matrix is large. When the interstitial areas are larger the segregations are usually more rounded.

The elongation of the segregations in the radial plane of the nodules could result from their mutual interference during growth, so that they continued to grow radially when their development,laterally had been checked by adjacent forms. By contrast, the more rounded nature of some of the other segregations could result from their growth in a medium offering little resistance.

Within any one nodule there is much leses variation in the form of the segregations than between different nodules. However, some variation both in the form and the size of the segregations within the crusts of individual nodules occurs. . • In most of the sections examined they are better developed in the interior of the nodule crust than at its surface, However, when there is a gradational relationship between the core and crust of the nodule, as in the case of those from station 5138, they become more isolated as the core is approached. It was sometimes observed that in the outermost layer of the nodule they become irregular in form and occasionally are absent altogether. When this occurs a continuous crenulated layer of manganese-iron oxides forms the outer rim of the nodule. The crenulations could : represent the development of embryo segregations.

The internal,structures of the segregations can be seen in plates 6a, 6b, 6c and 6d. Within these segregations concentric banding is developed. Examination of these bands under the high power of the microscope, after etching with HC1, reveals the presence of an occasional band of very finely divided silicate material interspersed with the manganese-iron oxides. The pattern of the banding in the elongated segregations is initially circular, but becomes more elongate as their outer margins are approached. Change in the growth direction of the segregations as a result of mutual interference is the most likely explanation of this observation.

DISCUSSION Certain features emerge from the above observations , that are common to most of the nodules examined. Firstly, there is usually a gradational relationship between the cores and crusts of these bodies, Only in a few cases was a clear line of demarcation between the core and the crust observed. Secondly, the manganese and the iron oxides are largely, segregated from each other in the crusts of the nodules, but are segregated together from the detrital phases in their cores.

The gradational relationship between the cores and crusts of the nodules could be largely the result of percolation of manganese and iron bearing solutions into the porous core materials. However, the presence of relict. plagioclase crystals in the manganese crusts, well away from the cores, suggests that in addition to being impregnated by manganese and iron the cores have been replaced by them also. Plagioclases are amongst the last minerals in submarine basalts to undergo dissolution (Peterson and Goldberg 1962), and therefore the more soluble primary materials with which they were associated must have been completely weathered away.

The segregations of iron and manganese within the core materials may also partly result from the diffusion of solutions bearing iron and manganese into the porous cores. However, this is unlikely to be the only mechanism. It is to be expected that iron and manganese will be liberated from the volcanic core materials on alteration. Bonatti and Joensuu (1966) have reported that altered lava fragments on the sea floor contain less manganese and other ferrides than the,original basalt from which they were derived. Further, Nayudu (1964) and Bonatti and Nayudu (1965) have reported segregations of manganese-iron oxides in palagonites from both submarine and terrestrial localities and considered them to result from the leaching and segregation of these elements within the palagonite during processes of palagonitisati,in. 44

Finally, Murray and Renard (1891) have recorded is interesting to observe that they (palagonitised basaltic glasses) are very rarely found without a more or less thick coating of manganese, while lapilli of , feldspathic basalt, of REitic or hornblendic andesite, or fragments of ancient rocks likes gneiss and granites, are often found in the same deposits without any, or but a very slight, coating of manganese."

Thus there is a body of opinion that believes that manganese and iron can be leached and reprecipitated during processes of alteration of volcanic glass. This mechanism would partly account for the segregations in the cores of the present nodules. The presence of the segregation even in the centres of these cores and the observation that they are mutually unconnected, at least in the radial plane of the sections, suggests that this mechanism is probably operative. If this is so the varying forms of the segregations could represent different stages of this leaching and reprecipitation process. In particular, the vesicle-like forms, various- ly rimmed with manganese-iron oxides could result from the diffusion of these elements during alteration processes, and are possibly segregations in an early state of growth. The dendritic forms probably also result from leaching and reprecipitation.

These observations are important and must be considered in any attempt to understand the origin of nodules. The removal of iron and manganese from the palagonite could partly account for the supply of these elements to the growing nodule crusts. 4.5

Bonatti and Nayudu (1965) considered the derivation of elements from submarine volcanics to be an important process in the formation of manganese nodules. This and other hypotheses will be discussed in a subsequent section.

The origin of the segregation structures in the crusts of the nodules could perhaps be,related to the origin of those in the cores. However, assuming an original body of identical size to the present nodule, an additional source of manganese and iron from outside is required to account for the volume relationships between the manganese-iron oxides and the other phases. If the original volcanic fragment was larger than the present nodule, the total amount of iron and manganese in the nodule could possibly be accounted for, but it would then be difficult to explain the close packed nature of the segregations. Possibly sources of elements from both within and outside the parent volcanic body are important. The origin of these structures will be further discussed after the presentation of relevant electron microprobe data. 46

CHAPTER 3.

ELECTRON MICROPROBE ANALYSIS OF MANGANESE NODULES Electron microprobe techniques have been used in the examination of selected manganese nodules in order to investigate firstly, inter-element relationships and secondly, the compositional relationships between the manganese segregations and the iron rich matrix in which they are enclosed.

Th9 samples chosen for analysis were selected firstly, on the basis of their variable compositions and secondly,on the basis of their development of segregation structures. All but one of the samples were taken from the North-West Indian Ocean, these being the samples upon which most of the petrographic work had been done.

ANALYTICAL METHODS The analyses were conducted on polished sections of manganese nodules previously examined by optical techniques. The sections were 3.5 x 3.0 x 0.5 cm. in size and were mounted in Ceemar. 47

(i)Sample Preparation In the earlier stages of this work the samples were coated with aluminium under vacuum prior to insert- ion into the path of the electron beam. However, owing to a change in the procedure in the electron microprobe laboratory during the course of this work, the later samples were coated with carbon.

(ii)Instrumental Methods After coating, the samples were placed in the electron probe and the instrument was evacuated overnight. Owing to the high porosity of the majority of the samples this often took longer than twelve hours to accomplish, sometimes taking as long as thirty-six hours.

The principles of electron microprobe analysis are briefly as follows. A finely focused electron beam is made to impinge on a microscopic area of a polished section of a mineral. This results in the production of a continuous spectrum containing X- radiation characteristic of the elements present in the specimen. The characteristic wavelength for any element is selected by means of a spectrometer and a pulse height analyser. In this manner the element can be identified and the intensity of its characteristic radiation is a measure of its concentration. In addition, electrons are backscattered from the specimen surface to various extents due to topography and the atomic numbers of the elements present. These electrons are detected by means of a scintillation counter and are used to build up a picture of the sample surface. 48

The apparatus used was a Cambridge Instruments Microscan Mark 1. The operating conditions were 25 kV and from 50 to 100 millimicroamps, depending on the effect the beam had on the sample surface. The back scattered electron and X-ray distribution patterns were produced on an oscilloscope screen which was photo- graphed with Polaroid land film type 47. The detection limits of most elements varied between 100 and 1000 ppm.; exposure times ranged from less than a minute to about 20 minutes.

A number of techniques were used to investigate the samples. These were as follows:- a) Wavelength Scanning The curved crystal semi-focussing spectrometer was set to scan over selected wavelength ranges in order to determine which elements were present in measurable quantities. Unfortunately, owing to the absence of a gas flow proportional counter during the course of this work,elements of low atomic number such as Na, Mg, Al and Si could not be determined.

b) Line Scanning The electron beam was set to traverse short distances, over the specimen surface, about 0.5inn., the variation in the concentration of selected elements being presented as a graph on the oscilloscope. This technique enabled variations in the concentration of selected elements to be monitored before a photograph was taken. 49

c)Electron Beam Scanning The electron beam was scanned over square areas of the sample surface. The intensity of the distribution of the characteristic X-radiation of selected elements, and the back scattered electron image, were recorded on the oscilloscope. This showed the two dimensional distribution of selected elements in the area being studied, the results being recorded photographically.

d)Point Analysis In one sample two areas were quantitatively analysed for all the elements detectable. This was conducted by counting for fixed times the intensities of the characteristic X-radiation of the elements found, and comparing with standards of known composition. Matrix absorbtion correct- ions were applied after Kelly (1966).

RESULTS The results of this investigation are presented in the form of photographs showing the distribution and intensity of the secondary X-radiation of the elements studied (plates to 12). In these photographs the distribution of the white dots shows the distribution of the element being studied and their intensity is a measure of its concentration. This does not yield a quantitative analysis but is useful in examining both inter-element relationships and two dimensional element distribution patterns. 50

(i) Sample 5133.7 A tangential section of this sample was selected for analysis as it showed the development of roughly circular segregation structures. These segregations were elongated in radial section and therefore the present section is cutting at right angles to their presumed direction of growth.

Nodule 5133.7 was moderately high in Mn and Ni and low in Fe and Co. It showed well developed con- contric banding and was hard and.compact, The distribution of the elements Mn, Ni, Co, Cu,Ti and Ca were investigated, while Ba and Pb were sought but not found (plate 7).

Considering firstly the major elements, it is apparent from plate 7 that manganese is clearly concentrated in the segregations while it is almost absent from the interstitial material. By contrast, iron has a more even. distribution being present in the interstitial material and in the segregations. Calcium follows manganese, being mainly present in the segregations but its distribution is more irregular than that of manganese. Calcium was the last element determined in this sample and part of its irregular distribution could result from cracking of the sample surface caused by dehydration under the electron beam.

Of the minor elements, nickel and copper are concentrated in the segregations with manganese, the former more so than the latter. 51

PLATE 7 Electron beam-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of manganese nodule 5133.7 x 250.

'. • 15..44 .4j1 • 44- •* JO, 11( t tAttl;;;N,

pr it% 4444.... gar • 4•• • 1?*

BSE Mn Fe

, ,.:1- -, ...... --..., ,t.. e•iiii • . ci. , ALF41; 4,16. •A P' , 4, 0 ..- illt i ir

•` .5* 4 4:4 14111, • 055. >5 • +4 •••• •.,.. •N • - ' ( Ili/ ovi " 9 9.. • r ' 41 •• •• • -"v. , ... , • 140 jr 5 • I p i •••!' . ....0 !IA/ . . 4, 4.x'N'apj)

4,*•* ., .4 b. ,,,‘) • .i?...lo A d • •.. 4- , , 5404.• 9 ••••

rd 'tf.:si r. 4 :c__. .,,,• ..; • ; .4 V •. A ' ...„.14!%,‘ 1. 1 4: s'4 4 ‘ 4 5.n dia‘ t5... 4. • A .14%: 'iir:,44.0-,•'''' '''.4'0 11 • ,...0. i . . ... 4 • ...., 4 ' • r,4., ...4;6,- ik.r,• • vor duo ,10 4 , . .` A ,,• 4 • 19 I ""i-ic•,r,k1A-4- '• pie ..'si . A • la " "t *. 1 C \:: I 2wk ri vWsr."1.1`';ti., --)tcd.:01 . A: A. A L ... 4 . -P• .1 .... t %. C C o N

4 . , A . ..Pe o- k 51 Nlit 'i t 1 il , Ar . t -I tOC 1.1; '''' ' . • ."5 0 1 0* " .. .t1/4 — ' . • 11 144-Itr t- . ' :74 V:.• I .1§4, - P '' , • : : • t1. 1t 4 AN' vt. C 1 ‘At • ,i 974 A i S.• 11"; : .1 A . -, 4 , - t.• ..t., -0?- '.. . .8 X4,14 I e ), • .•4 • • - ge 41,.. 1 ' i 4.0- • 01 A" • • • ...I lb.- le 41' IV * • . • , • . • 115, *, 1/4. 4 t aVlijit

Ca T 53

However, they are still present in the interstitial material in proportionally greater concentrations than manganese. By contrast, cobalt and titanium have a fairly even distribution showing little preferential enrichment in either the segregations or the interstitial material.

Within the segregations themselves element variations also occur. The peripheral areas of the segregat. . ions are depleted in manganese relative to their centres. By contrast, nickel and copper are sordewhat, enriched in the peripheral areas of the segregations relative to their concentrations immediately inside the periphery. However, secondary maxima in the content of these two elements occur at the centres of the segregations.

Analysis of two areas, one within the central segregation and the other in the interstitial material, gave the results presented in table 3.1. It can be seen from these results that all elements are more enriched,in the segregation than in the interstitial material, but that in neither case does the total give 100 percent. This,is largely the result of elements such as Si, Na, Al, Mg and K not being determined, but this is unlikely to be the only cause. The low total for the interstitial area compared with that for the segregation is probably the result of the enrichment of water in the iron phases (Arrhenius 1963) and also the presence of detrital materials not detectable owing to the elements of which they consist being of low atomic number. 54

Correlation analysis (section 5.4) indicates that water follows iron in manganese nodules. Further, the loss on ignition of this nodule was between 25 and 30 percent by weight. In view of the total of elements in the segregation most of this must be present in the interstitial material. In addition, in this sample the volume of the segregations is greater than that of the interstitial areas (plate 3a). Thus in order for there to be a 25 percent loss on ignition the water content of the interstitial material must be high.

Segregation Interstitial Material Mn02 32.61 0.83 Fe203 53.40 27.92 TiO2 0.91 0.26 Co0 0.53 0.04 Ni0 0.44 0.04 CuO 0.15 0.03 Ca0 3.30 3.14

Total: 91.34 32.26

Table 3.1: Analysis of nodule 5133.7 (in weight percent).

(ii) Sample 5179.1 A radial section of this nodule showing the development of circular segregations was chosen for investigation. 55

This nodule was higher in cobalt,and lower in copper and nickel than the previous one, and consisted of porous material of vesicular appearance. The elements Mn Fe, Ni Co Ti Zn, Ca and K were determined while Cu, Pb, Ba, Mo and V were sought but not detected (plate 8).

As in the previous sample the clear concentration , of manganese into the segregations is observed. However, in this sample iron is enriched in the interstitial material. Both calcium and potassium follow the manganese and are enriched in the segregations. The lack of resolution of potassium results from the very high iron background under the potassium peak. The potassium K o& first order and the iron K p second order peaks are very close together and it was not possible to resolve them separately with the equipment used,

Of the minor elements, nickel and cobalt are - concentrated within the segregations but are present in relatively higher proportions than manganese in the interstitial areas:. Titanium is partially concentrated in the segregations but is also abundant in the interstitial material. Zinc has a peculiar distribution. It is present in the interstitial areas but does not appear to associate with any other elements Its irregular distribution and localised high concentration suggests the formation of separate zinc, or zinc-iron minerals. The actual zinc content of this nodule determined by X.R.F, was 600 ppm. 56

PLATE S Electron beam-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of manganese nodule 5l79.1 x 250, a) 0 C LL N

; sf. '*, • k4.11 a • 16' 4%1' frS

C `e,• 'w • z s • " 1.4 " . • • "t •

z 58

Within the segregations there is not the clear further segregation of elements found in the previous sample. However, manganese is slightly enriched in the centres of the segregations relative to its concentration in the peripheral areas whilst nickel, and to a greater extent cobalt, are rather depleted. Iron is also rather lower in the centres of the segregations than in their peripheral areas and in the interstitial material. Titanium appears to be concentrated slightly in the peripheral areas of the segregations relative to its concentration in their centres. In addition, there is one small area containing a very high titanium content. This could be a discrete titanium mineral, Arrhenius (1963) having reported the presence of rutile and anatase in manganese nodules.

(iii) Sample 2P50 This nodule from the South Pacific Ocean, a radial section of which was examined, shows the development of segregation structures. It is higher in cobalt than in nickel and copper. As in the other samples manganese is concentrated into the segregations, these being separated by narrow iron rich interstitial areas (plate 9).

The copper, cobalt, and nickel distributions are not so variable in this sample as in the previous two. Nickel is largely present in the segregations but is also found in the interstitial material. Cobalt also tends to be abundant in the segregations but not to the same extent as nickel. Copper has a rather irregular distribution? 59

PLATE 9 Electron b?am-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of manganese nodule 2P50, :( 250, 1 r-- . - • *- T 1 y. 4' • . . . ,

7 U

r z

rts 61

Within the segregations further compositional variations occur. In the top left hand segregation a circular enrichment of manganese is associated with a decrease in the iron content. The distribution of the minor elements is rather irregular, largely owing to the dehydration and cracking of the sample surface under the electron beam. This was prevalent to a greater or lesser extent in all the samples examined but was particularly so in this one as, owing to a series of mechanical failures, the sample was in the instrument for about a week. In order to demonstrate, the effect of the electron beam on the sample surface, the back scattered electron pictures taken at the beginning and end of.the analysis are presented for comparison (plate 9).

(iv) Other Samples The remainder of the samples examined showed features similar to those discussed. The antipathetic relationship between iron and manganese is seen in samples 5133.1 and 5179.1 (plate 10). Com- positional variations within the segregations can be seen in plates 11 and 12. In one segregation manganese is enriched in the centre while iron is more abundant in the peripheral area (plate 12). Nickel tends to follow,manganese in the centre of the segregation while cobalt, more abundant in the segregation than in the interstitial area, has a higher concentration around the periphery. Calcium follows manganese in the centre of the segregation. 62

PLATE 10 Electron beam-scanning photographs of back-scattered electrons and characteristic K radiations from sections of nodules 5133.1 and 5179.1. x 250.

. I .

• - • 1 N • r. ••••• .4- a• • $ • •

IS" 4,14;•C • ••• . . IP IL A . • , • . 01' • ,404 • • • A. . • • • 4 VA 6.4. •

• 7° le • i4g• • I d • 4 • • 4s, • • •

Mn Mn

..; _4•_ . • • -,„

wilitif ,. -

F e F e

B.S. E . B. S. E . PLATE 11 Electron beam-scanning photographs of back-scattered electrons and characteristic K radiations in a section of manganese nodule 5133.1. x 250. B.S. E.

Mn Ni

F e 66

PLATE 12 Electron beam-scanning photographs of back-scattered electrons and selected characteristic K radiations from a section of manganese nodule 5179.1. x 1000. 0 U

w tr) tll co z LL 68

A clear relationship between manganese and nickel is shown in sample 5133.1 (plate 11). Here two large radially elongated segregations are seen, with a narrow interstitial area between them. Good internal banding, slightly elongated in the radial plane of the nodule, is observed within the segregations. In one of these bands manganese and nickel are enriched while iron is depleted.

(v) Summary a)Mn, Ca, K, Ni, and Cu tend to be associated together and are enriched in the segregations. b) Co is also concentrated in the segregations but to a lesser extent and tends to follow Fe slightly in its distribution within the segregations. c)Ti has a fairly even distribution but tends to associate more with Fe than with Mn. d)Of the elements studied, Fe is present largely alone in the interstitial areas except for water, but is present in the segregations also. e)The irregular distribution of Zn suggests the formation of separate Zn minerals.

DISCUSSION The data presented are of significance in terms of inter-element relationships in manganese nodules, and in terms of the origin of the segregation structures.

(i) Inter-element associations Previous electron microprobe analysis of manganese nodules has indicated that certain inter-element associations exist. 69

Burns and Fuerstenau (1966) in the only published electron probe study on manganese nodules to date, suggested that the elements Co, Ti and Ca followed Fe,and Ni, CulZn and Mg followed Mn. The data presented in this work partially substantiate these conclusions but significant differences are observed.

The association of Ni and Cu with Mn observed by Burns and Fuerstenau (1966) has been found in the present samples. These elements all concentrate in the segregations relative to their concentrations in the interstitial areas. Generally, they tend to follow manganese in their distribution within the segregations, but occasionally the reverse is found and they segregate from manganese as in sample 5133.7 (plate 7).

The association of Ca with Fe, and Zn with Mn, noted by Burns and Fuerstenau (1966) has not been observed.. Calcium in the present samples follows manganese into, and within, the segregations. In this respect it is similar to potassium, a behaviour which would be expected in view of the presence of both elements as constituents of todorokite (Straczek et al 1960) and calcium of birnessite (Jones and Milne 1956), both important manganese minerals in manganese nodules (Chapter 4).

Cobalt has a variable distribution in the nodules examined. It does follow Fe as suggested by Burns and Fuerstenau (1966) but is also concentrated in the manganese segregations. 7.0

Possibly it varies independently of both elements (section 5.5). Titanium has a rather even distribution throughout the samples examined, apart from the formation of possible Ti minerals, but tends to follow Fe more than Mn,

From these observations and those of Burns and Fuerstenau (1966) it is apparent that inter-element associations within individual nodules are rather variable. Most of the minor elements tend to be more enriched,in the segregations than in the interstitial material, but once inside the segregations they can vary independently of each other. A good example of this is found in the relationship of Cu and Ni to Mn. These elements are enriched in the segregations over their concentrations in the interstitial materials. Usually they. vary together within the segregations also. How- ever, it is evident from sample 5133.7 (plate 7) that these elements can also vary independently of each other within the segregations.

The variable relationships of certain elements in nodules could be related to variations in the chemical micro-environment .:ithin the nodules, and the enrichment of certain elements into rims within and around the segregations possibly indicates the operation of diffusion processes. In any event the factors determining the distribution of elements within the nodules are likely to be related to the origin of the segregation structures themselves, 71

(ii) The origin of the segregation structures in the crusts of the nodules Any explanation of the origin of the manganese- iron oxide segregations surrounded by the iron and silica rich matrix, will have to account for a number of observations. These are as follows:- a) The regular forms of the segregations within any one nodule. b) The absence of segregations in the outermost layer of some nodules., c)The widening of the interstitial areas as the cores of the nodules are approached in nodules showing a gradational relationship between the cores and crusts. d) The internal growth structures of the segregations and their elongation in the radial plane of some nodules. e) The concentration of most of the minor elements into the segregations and the variable behaviour of these elements within the segregations.

There are a number of possible explanations of the origin of the segregation structures. They could represent previously formed micronodules that have aggregated together. Alternatively, they could represent the segregation of iron and manganese either at the nodule surface on deposition, or after deposition during early diagenesis. 72

The aggregation of previously formed micronodules is not considered a likely explanation. It does not account for most of the observations listed. In particular it is at variance with the elongation of the segregations and their absence in the outer layers of some nodules.

This leaves the other possibility that the segregations form either on, or after, the deposition of the iron and manganese phases. Both processes could be operative. If the segregations form by the separation of iron from manganese at the nodule surface, the crenulated outer layer observed in some nodules could represent the growth of embryo segregations. However, the increasing perfection in form of the segregations towards the inner layers of the crusts suggests that they form mainly after the deposition of the iron and manganese phases, probably while these are still in a gel state.

Goldberg (1954) has suggested that the iron and manganese phases in nodules are precipitated in a colloidal form. This would accord with the general lack of crystallinity of the iron phases in the nodules examined and also with their colloform appearance. How- ever, it is commonly observed that the manganese phases of the nodules are crystalline (Chapter 4). The post- depositional ageing and crystallisation of these manganese phases could provide a mechanism for the formation of the segregations by th. diffusion of Ii2-Ingan,33 associated elements towards the centres of crystallisation. 73

The circular banded central areas of the segregations could represent segregations of iron and manganese oxides formed by leaching and reprecipitation of these elements within the original volcanic core materials (Chapter 2). That these latter were more extensive than now is evinced by the nodule crusts containing relict primary minerals and quantities of finely divided silicate material. However, an additional source of manganese and iron from outside the nodule is required to explain the volume relations between the segregations and the remaining silicate material. This additional supply will enlarge any pre-existing segregations or in their absence form new ones. By this enlargement the elongation of the segregations in the radial plane of the nodules can be explained. This feature could not result unless a supply of elements from outside the original volcanic core materials was available.

That diffusion of elements through the saturated gel materials occurs is evinced by the minor element variations within the segregations. ?That causes this diffusion is not clear but it could possibly result from the migration of elements towards centres of precipitation. Crystallisation of gel materials would be expected to be accompanied by a loss of water. In this context the observation of circular shrinkage cracks in some sections is significant.

It is concluded that the segregations of manganese iron oxides in both the cores and the crusts of nodules are probably related. 774-

Those in the cores are considered to result largely from the migration and segregation of manganese and iron within the volcanic materials. This could partially explain the presence of the segregations in the crusts also, replacement evidence suggesting that the volcanic materials were more extensive than they now appear. However, a supply of iron and manganese from outside the nodule is required to explain the volume relationship between the segregations and the interstitial areas. This probably precipitates as a gel which on ageing crystallises and enlarges any pre- existing segregations and forms new ones also. In this manner the observed growth structures of the segregations can be explained. 75

CHAPTER 4.

THE MINERALOGY OF MANGANESE NODULES

THE MANGANESE MINERALS

Introduction and Previous Work The mineralogy of approximately sixty nodules has been investigated using X-ray diffraction techniques.

The mineralogy of manganese nodules has been the subject of some controversy ever since mineral identifi- cations were first made on these bodies by Buser and Grutter (1956). In a series of papers (Buser and Grutter 1956, Grutter and Buser 1957, Buser 1959) these authors suggested that three principal manganese phases were present. The X-ray powder patterns of two of these minerals were identical with those of the synthetic 7 A manganous manganite and Mn02 of Buser et al (1954) and were called the 7 A manganite and Mn02 respectively. The third phase having a basal spacing of 9.7A was thought to obe a modification of the 7A manganite and was termed 10A manganite, 76

These authors suggested that there was a structural relationship between these minerals and that their degree of oxidation and disorder increased from the o 10A manganite through 7A manganite to Mh02°

Recent work on the synthetic manganese dioxides by Bricker (1965) has shown that the 7A manganous manganite and Mn02 of Buser et al (1954) are compositionally and mineralogically identical to each other. He considered that the differences between the powder patterns of these two forms (table 4.1) is a result of their differing particle sizes, it having been shown by Buser and Graf (1955) and McMurdie and Golovato (1948) that the particle size of S Mn020is an order of magnitude smaller than that of the 7 A manganous manganite As a result of this Bricker (1965) has suggested rejecting the name manganous manganite and calling both these phases 6 MnO2.

Accordingly, only two principal minerals are known to occur in the nodules; Buser and Grutter's 10A manganite and their 8 Mh02.

Manganous Manganite 8 Mn02 0 dA I dA 1 7.2 S 3,63 M 2.43 S 2043 S 1,42 S 1.42 S

Table 4.1: Powder Patterns of Manganous Manganite and Mh02 (Buser et al 1954) 77

Independent of the work outlined above, other investigators have examined the mineralogy of manganese nodules. Straczek et al (1960) have reported the. presence of todorokite (Na, Ca, K, mn2+) (mn4+, mn2+,mg) 6012 3H20 (Yoshimura 1934.) in a manganese nodule from the Pacific Ocean. G.W. Moore (U.S.G.S. Menlo Park, California, personal communication 1966) has also found this mineral in nodules from the Pacific, According to Levinson (1962) birnessite (Na 0.7 Ca0.3) Mn7 014 2.8 H2O (Jones and Milne 1956) has been found to be a constituent of manganese nodules from the Pacific and Atlantic Oceans. Manheim (1965) has detected the presence of both todorokite and birnessite in nodules from various localities. In addition, this latter author has also found psilomelane and a form of ramsdellite in manganese nodules and suggests that as yet undescribed manganese minerals may be present in these bodies.

Comparison of the principal powder lines of the various phases suggested as being present in manganese nodules reveals considerable similarities (table 4.2). This is easily explained in the case of birnessite and 8 Mn02 for Jones and Milne (1956) have shown that birnessite is a naturally occurring form of synthetic S' Mn02. The similarity between the powder patterns of todorokite and 10A manganite suggests that these also are mineralogically identical. Certainly, it appears that the phase termed 10A manganite by Buser and Grutter (1956) has been called todorokite by subsequent workers. In view of its historical precedence this latter name is preferred and with the name birnessite will be used in this work to describe the two principal minerals found in manganese nodules. 78

Todorokite 10A Birnessite 7A 6 mno2 Manganite. Manganite 0 0 0 0 0 dA I di, I dA I dA. I dA I 9.56-9.65 10 9.7 5.98-7.20 1.5 7.27 s 7.2 4.76-4.81 8 4.8 4.42-4.45 1 3.60 w 3,63 m 3.19-3.20 3 3.25 2.45-2.46 2.5 2.46 2.44 m 2.43 s 2.43 2.39-2.40 4.5 2.33-2.36 1.5 2.36 2.21-2.23 3 2.13-2.16 1 2.18 1.42-1.43 3 1.42 1.412 m 1.42 s 1.41 1.38-1.40 1.5

Table 4.2: Comparison of principal powder lines of phases suggested as being present in manganese nodules. 1)Todorokite: Data from Straczek et al (1960), Frondel et al (1960) and Levinson (1960). 0 2)10A Manganite: Data from Buser and Grutter 1956. 3)Birnessite: Data from Jones and Milne (1956). 0 4)7A Manganite: Data from Buser et al (1954).

5) jMnO2: Data from Buser and Grutter (1956). 79

Buser and Grutter (1956) suggested that the differencQ3between X-ray powder patterns of minerals in manganese nodules is a result of their differing degrees of disorder related to their varying degrees of oxidation. However, the work of Bricker (1965) shows that oxidation differences do not cause the differences between the X-ray powder patterns of two of these phases, these probably being related to particle size differences alone. However, the possibility still exists that while variation in the powder patt9rn E of Mn02 is not the result of oxidation differences, the difference between todorokite and birnessite could be. Bricker has reported synthetic preparations of birnessite haying O:Mn ratios ranging from 1.74 to 1.99. However, the 0:Mn ratios of naturally occurring samples of todorokite analysed to date vary from 1,79 to 1.87 (data recalculated from Frondel et al 1960, Straczek et al 1960). Thus it is possible that oxidation differences occur between todorokite and birnessite in the natural environment. Much more data is required before this possibility can be confirmed.

The structures of the minerals in nodules have not been determined directly. However, from the postulated structure of 6' Mn02 (Buser et al 1954), Buser and Grutter (1956) suggested they have a double layer form, the so called 10A manganite having two Mn2+ layers 0 between layers of Mn4+, while the so called 7A manganite has only one such layer. S Mn02was believed to consist of randomly orientated double sheets a few atomic layers thick. 80

Whether these structures are present in todorokite and birnessite can only be determined from structural studies on these phases. However, certain similarities between their powder patterns and the observation of the writer (page89 ) that todorokite appears to give way to birnessite on heating suggests that there could . be a structural relationship between these two minerals.

Methods (i) X-ray Diffraction X-ray powder analysis of the present samples was conducted using a Phillip's diffractometer. The operating conditions were 40 kV and 20 mA using CU, K cc radiation, Ni filter. The scan speed was 2° per minute with a time constant of one second. The receiving slit was 0.1 mm. wide and the divergent and scatter slits were varied according to the angles scanned. Pulse height discrimination was used to reduce fluorescent background.

Analysis of the acid insoluble residue of some of the nodules was conducted as above with the exception that the scan speed was i° per minute with a time constant of four seconds°

As an addition to the diffractometer analysis selected samples were analysed using a Guinier quad- ruple focusing camera with unfiltered Fe K c;)C radiation 81

(ii) Heating Experiments In order to investigate the effect of heat on manganese nodules of varying chemical and mineralogical composition, several samples were heated by stages up to 650°C and subjected to X-ray powder analysis after each stage. The temperatures to which, the ampler were,heated were; 37°, 50°, 68°, 89°, 98°, 119°, 139°, 165°, 191°, 430° and 650°Q, respectively. This procedure was carried out in air, initially in an oven but at higher temperatures in a furnace. No attempt was made to control variables other than the temperature.

Results (i) Mineral identification On the basis of their X-ray powder patterns the present samples can be divided into four groups. 0 a)Those showing the 9.7A peak of todorokite, (ten samples). 0 b)Those showing the 2.44 A band of the two line form of birnessite,(seventeen samples). 0 c)Those showing the 7.1A peak of the four line form of birnessite, (one sample). 0 d)Those showing both 9.7A and 7.1A peaks,(three samples),

Subsidiary peaks of todorokite and birnessitg were also observed. The remainder of the samples, twenty-seven in all, showed no distinct peaks and were.regarded as being either non/or poorly crystalline. 82

The powder patterns of some well crystalline samples of these minerals are presented in table 4.3. In addition,the patterns of todorokite and birnessite taken from the literature, and that of a sample of todorokite from Charco Redondo, Cuba, are presented for comparison.

In an attempt to confirm the X-ray identification of todorokite, one sample thought to contain this mineral (Loch Fyne, table 4.3) was subjected to D.T.A. up to 1000°C. An endothermic peak was observed at 625°C and another at 980°C (Fig.4.l). This is in agreement with the D.T.A. pattern of todorokite reported by Frondel et al (1960).

In a further attempt to confirm the identification of todorokite and birnessite, samples thought to contain these minerals were heated to 120°C and 625°C respectively. The 7.11 peak of birnessite collapsed at 120°C while at 625°C hausmannite developed at the expense of todorokite. This is in agreement with the reported behaviour of todorokite and birnessite (Jones and Milne 1956, Frondel et al 1960).

On treatment with hydroxylamine hydrochloride all the peaks assigned to todorokite and birnessite disappear- ed. This is in agreement with the behaviour of these peaks as reported by Buser and Grutter (1956).

(ii) Heating Experiments The results of these experiments are shown in Figs.4.2 and 4.3. In Fig. 4.2 the peak heights of todorokite and birnessite have been plotted against rising temperature; the broken lines represent birnessite and the solid lines todorokite.

1 2 3 . 4 Charco' Loch Chal. Chal. Redondo. Fyne 297 160 0 0 0 0 di, I dA I dA I dA I 9.60 100 9.66 100 9.56 100 9.80 100 7.10 55 4.78 60 4.81 75 4.81 45 4.81 75 4.43 5 4.48 5 4.45 50 3.40 10 3.34 5 3.20 5 3.19 40 3.11 10 3.11 10 2.46 25 2.45 15 2.44 40 2.45 55 2.39 50 2.40 20 2.39 30 2.40 50 2.35 40 2.35 10 2.35 20 2.36 30 2.22 10 2:23 20 2.23 40 2:13 15 2.13 25 1.97 10 1.97 25 1.97 10 1.97 25 1.916 5 1.916 5 1.91 10 1.77 10 1.77 15 1.67 5 1.67 20 1.53 10 1.53 5 1.53 15 1.53 35 1;49 5 1.42 20 1.41 25 1.42 40 1.42 35 1.39 10 1.40 25 1.40 30 1.40 10 Table 4.3: Powder Patterns of selected manganese nodules. 1)Todorokite from Charco Redondo, Cuba. 2)Samples 2, and 4 contain todorokite alone. 3)Samples 3, 5 and 6 contain todorokite and birnessite.

84 5 6 7 MV-65-1 Mag. Bay. MV-65-1 NP.25 38 A35 41 Fl

0 0 0 0 dA I .dA I dA I dA 9.81 45 9.70 100 7.24 100 7.20 80 7.18 100 4.84 25 4.80 50 4:45 15 4.45 20 3.61 35 3.57 20 3.57 30

2.45 25 2.44 30 2.44 20 2.43 b 2.42 25 2:39 25 2.35 15 2.217 15 2.25 20

1:73 10 1.67 5 1.53 5 1.42 25 1.42 30 1.41 15 1..41 b 1.39 10 1.39 10 Table 4.3(Cont'd) 4)Sample 7 contains the four line form of birnessite alone. 5) Samples 8 and 9 contain the two line form of birnessite identical to the S MnJ2 of Buser and Grutter (1956). 6) Column 10 contains the range of previously reported values for todorokite. Data from Straczek et al (1960), Frondel et al(1960)and Levinson (1960), 85

9 10 11 12 MP.43A Todorokite Four Line Two Line Birnessite Birnessite 0 o o dA I dA I dA I da 9.56-9.65 100 6.98-7.20 15 7427 s 4.76-4.81 80 4.42-4.45 10 3.60 w 3.40 5 3.19-3.20 30 3.10-3.11 10 2.43 b 2.45-2.46 25 2.44 m 2.43 2.39-2.40 45 2.33-2.36 15 2.21-2.23 30 2;13-2.16 10 1.98-2.00 10 1.92-1.93 10 1.83 5 1.78 10 1.73-1.75 10 1.68 5 1:53-1.56 10 1.49 30 1.41 b 1.419-1.43 30 1.412 m 1.41 1.38-1.40 15 1.33 5 Table 4.3(Cont'd) 7)Column 11 contains data on birnessite taken from Jones mad Milne (1956). 8)Column 12 contains data on the two line form of birnessite identical to the S Mn0 of Buser and Grutter (1956). 2 86

FIG 4.1 D.T.A. trace of Loch Fyne nodule

c-- tO I Z•Ir 01A I 11 01 6 9 L 9 9 tr £ Z 1 OE LE trZ lZ 91 91. Z1 6 9 E 111_111111 I I II I I I 1 III / / 9. / x O / e I0 —09 -09 / 0 0 0 x .00 —001 30 -001 0. *— •••••• ......

11-•••••.... •••••• •41. 1 ▪ " ...... ••••• *a . elm* •••• 0 ... .6 0 MOM ••••• ... • **. 00Z ."" - 0.... 00Z

a 3

I I 9L 99 PE Z 1 OE LZ VZ IZ 91 91 Z1 6 9 E I II II I 1 1 1 i 1 I III I 1 i 1 t

.0 .0 0 o0 .0 ) ( x .cx• -09 .0 -09 .0 0 .0 /0 a• Q a.' -001. Oa -001 De .1.. •••• 0 t#..• ...° ... •••• 0 ... — ..... Nab ... 0 .0 m. .. 0 Nem ••••• ••• ••• MM. .... •••• ••• .., MD 0 OE ••••• .a., ...... Oa .111•• 0 00Z 00Z

8 V Fig 4-3 Effect of heat on a nodule containing todorokite and birnessite

..a 34 G) .J::. "14 c-4 o

50 119 139 165 g9

From these experiments the following salient features were noted.% a)On heating,nodules containing todorokite and birnessite, the peak height of the former decreased while that of the latter increased, e.g. Mag.Bay.A 35, Fig. 4.2A and 4.3. b) In two out of three nodules containing todorokite alone, the 9.7A peak collapsed at a temperature below 450°C and a small birnessite,peak appeared (e.g. Chal. 160 and 2P52, Fig. 4.2, B and D). In the third sample it remained constant until the temperature was above 450o0, this sample being similar in behaviour to the todorokite from Charco Redondo. c)In nodules containing birnessite alone, the height o of the 7.1A peak increased up to a temperature of about 120°C after which it rapidly collapsed,e.g. MV-65-1-41, Fig. 4.20. d) After the disappearance of both the todorokite and birnessite peaks the 2.44A band sometimes increased in intensity, but usually just varied irregularly (table 4,4), e) Above 650°C variable proportions of the minerals hausmannite and jacobsite were found in all samples,

(iii) Mineralogical Variations The depth and regional distribution of the different minerals identified in the present samples have been examined. 90

Temp.Intensity Intensity intensity Adth 0 oC 9.7A 7.1A 2.44A 2.44A

15 6 13 5 6 37 4 15 5 5 50 0 24 5 5 68 2 24 5 5 89 0 24 5 4 98 0 26 7 5 119 0 28 5 6 139 0 20 5 8 165 0 11 6 9 191 0 4 5 11 430 0 0 5 15

o" o Table 4.4: Effect of heat on the 9.7A,7.1A and 2.44A peaks of sample MV-65-1-38. Explanation: The intensity of the peaks is measured in tenths of an inch above background. The o width of the base of.the 2.44A band is also meaetred in tenths of an inch.

This sample consists of a mixture of todorokite and birnessite. On heating, the todorokite peak decreases.in intensity whilst the birnessite peako increases. After collapse of both peaks the 2.44A band broadens consioderably. 91

The results are presented below.

a) Mineralogical variation with depth. Nodules containing todorokite as their principal mineral phase were found at greater average depths than those rich in birnessite, 4599m. and 3088m. respectively. Indeed, many of the birnessite rich nodules examined were collected on seamounts sometimes extending to within a few hundred metres of the sea, surface. However, one shallow water inshore nodule, that from Loch Fyne, taken in less than 100 fm. of water was found to contain well crystalline todorokite. According to Buchanan (reported in Murray and Renard 1891 p. 365) nodules from this site have a lower oxidation state than nodules found in oceanic areas.

b) Regional Mineralogical Variations. It is not possible to base an appraisal of the regional distribution of the minerals in manganese nodules,on the limited number of samples analysed. However, mineralogical differences between nodules from different locations have been observed.

On present evidence todorokite rich nodules have a limited geographical distribution. In the Pacific Ocean, they are confined to East of 130°W where they occur both in pelagic areas and off the continental margin. In the Indian Ocean one todorokite rich sample has been obtained from a locality on the Carlsberg Ridge while other samples have been obtained in the vicinity of Indonesia and South Australia. 92

Nodules containing birnessite are more widely distributed. However, the majority from the Pacific were collected West of 130°W particularly in the area of the Mid-Pacific Mountains and the island groups of the South Pacific. In addition, nodules from the West Indian Ocean, especially on the Carlsberg Ridge, commonly contained birnessite as their principle mineral phase.

The three samples containing todorokite and the four line form of birnessite are all from the East Pacific, two from the continental borderland and the third from near the Clipperton fracture zone. One sample containing the four line form of birnessite alone was also taken from the continental borderland.

Discussion The observation of regional variations in the mineralogy of manganese nodules poses the problem as to the cause of these variations. ,The average depth of nodules taken,from the East Pacific, a region of todorokite rich forms, is 3960 metres. By contrast, the average depth of those from the Mid-Pacific Mountains, an area of birnessite rich forms, is only 1747 metres. This suggests that apparent regional variations in the mineralogical compos-, ition of manganese nodules can, at least on a broad scale, in part be related to their differing depths of formation.

The variation in the mineralogy of manganese nodules with depth could result from a number of factors, possibly largely environmental. 93

However, the wide range of depths over which different mineral forms are encountered in oceanic nodules (3245- 5860m, for todorokite and 694-5582m. for birnessite) indicates that the factors causing these mineralogical variations are not variables, such as pressure, which vary regularly with depth, Rather, it suggests that they are factors which, while they show a general relationship to depth, probably vary under the influence of other environmental conditions also. Two such factors are the contents of dissolved carbonate and oxygen in sea water Carbonates playa minor part in the geochemistry of manganese nodules, but oxygen plays a more important role, In view of the possible oxidation differences between todorokite and birnessite the general decrease in the dissolved oxygen content of sea water with depth (Richards 1965)could be a factor in influencing the mineralogy of nodules, Decrease in the dissolved oxygen content of sea water in inshore areas relative to its concentration in the open ocean could also explain the low degree of oxidation, and thus perhaps the presence of todorokite in the nodules from Loch Fyne. However, little is known about the environmental conditions where nodules are forming and on present data it is not possible to draw any firm conclusions. 94

THE OTHER MINERALS

Introduction In addition to the principal mangantles?.phases discussed previously, othe/7 minerals have been reported in manganese nodules. Iron, Quantitatively the second most important element in these bodies is present mainly in the form of,goethite or amorphous Fe0OH (Arrhenius 1963). In addition, both detrital and authigenic minerals such as opal, rutile, anatase, phosphates, barytes celest- tobaryte zeolites, clay minerals, feldspars, quartz, pyroxenes, olivines and accessory minerals have been reported.

The minerals quartz, feldspar, pyroxene and olivine are quantitatively important in the detrital phases of many nodules, especially those from volcanic areas (Chapter 2). 95

Quartz is commonly found, but Rex and Goldberg (1958) consider a significant proportion of this mineral to be derived from the continents. Most of the detrital phases are present in a highly altered state and do not lend themselves well to microscopic examination. However, with the aid of X-ray diffraction techniques information of some of the less altered phases such as feldspars, can be obtained.

Detrital Feldspar Analysis Using the relationship between the 131 and 171 peaks of plagioclase feldspar, as applied to pelagic sediments by Peterson and Goldberg(1962), the compositionsof the plagioclases in.the cores of some manganese nodules have been determined. This method utilises the variation in the 'd' spacing of the 131 and 171 planes of the plagioclases as a function of their composition and thermal history (Fig.4.4). In determining plagioclase compositions by this method it has to be assumed that all the samples have undergone the same thermal history. This has been shown by Peterson and Goldberg (1962) to be largely the case for plagioclases in pelagic sediments, these authors considering them to fall in the volcanic group in Fig,4.4. The same factors that apply to plagioclases in sediments are considered to apply to those in nodules for it has been shown by a number of authors that these phases have a similar origin in both rock types (Murray and Renard 1891).

Using the value 2i9 171- 131 Cu K -40( radiation, Peterson and Goldberg (1962) have delimited the composition of plagioclases in pelagic sediments (table 4.5). 96

I— z I— cr I-- O

2.50= IX ANORTHITE - BYTOWNITE C.) 200 .04 09:70" LABRADORITE -ANDESINE SYN ANDESINE - OLIGOCLASE

IF) 1.50 OLIGOCLASE- ALBITE CD C\I CD

1.00 0 20 40 60 60 100 MOLE PERCENT ANORTHITE

Fig.4-4 An envelope surrounding the reported values of 020 (131 and 131), using CuKa radiation, for the plagioclase series. The boundaries within the diagram are based on reported occurrences of the feldspars. The diagram demonstrates the manner in which the plagioclase series has been divided into feldspar suites for the X-ray study of fine-grained oceanic sediments.

Sonidine-onorthoclose or Andesine - oligoclase r. 5555gt Lobradorite-andesine Bytownite - onorthite Fig.4•5:.A summary map showing the geographic distribution of the various feldspar suites in the area of the South Pacific thus far studied. The area between the dashed line and the stippling is °fin' of virtually no local volcanism. Big arrow points to Easter Island. from Peterson and Goldberg (1962).

Plagioclase

2.1 Bytownite-Anorthite 1.9-2.1 Andesine-Labradorite 1.6-1.9 Oligoclase-Andesine 1.1-1.6 Albite-Oligoclase

Table 4.5

It can be seen that the value of 131-131 does not give a unique composition for a particular plagioclase. Rather, it delimits general compositional fields. In addition, certain factors can alter the original composition of plagioclase. In particular, leaching by sea water can lead to the partial dissolution of the calcic component thus displacing the average composition of the assemblage as a whole towards the more sodic end of the series. Similarly, the use of hydrochloric acid to dissolve the non-detrital constituents of the nodules can selectively dissolve calcic plagioclases (Arrhenius 1963). Thus the original compositon of the plagioclase may have been more calcic than it appears at present, however, it is unlikely to have been more sodic.

Results and Discussion Plagioclase determinations on the cores of a number of nodules from widely separated localities are presented in table 4.6. The principal assemblage found was of labradorite- andesine composition with occasional oligcclase, andesine. This is in agreement with the work of Peterson and Goldberg (1962) for plagioclases from most of the South Pacific (Fig.4.5).

2 a

Sample 131-131. Plagioclases.

DWBG 59 1.9 Andesine-Labradorite

Proa.113P 1.9 TT ti Jyn.5.17G 1.9 91 Proa,162G 1.85 if TT MP,37C 2.0 VI TT 1.9 it IT Amp.86GV 1.85 41 IT Chal.297 1.9 IT 11 MP .26A3 1.85 It TT Jyn.2 9G 1,8 IT TT DWBD 1 2.0 IT IT S.0.B.20D 1.6 Oligoclase--Andesine Ris.14V 1,9 Andesine-Labradorite

Table 4.6: Composition of plagioclase3in the acid insoluble residue of some manganese nodules.

These data are possibly of significance in terms of the compositional variations between nodules from different localities (Mero 1965 and section 5.11). Bonatti and Nayudu (1965) have suggested that acidity variations between submarine volcanics from different areas could result in variations in the composition of the non-detrital fraction of the associated nodules. 99

They were of the opinion that the slightly acid vulcanism of the East Pacific Rise could be the cause of the higher than average manganese content of nodules found in that area. The nodules examined in this study are of widely varying compositions (Appendix 2) and yet on the basis of the plagioclase assemblages present, there is no evidence of significant variations in the acidity of their associated volcanics. Thus it would appear that factors other than acidity variations in submarine volcanics are the cause of compositional variations between nodules from different areas. Further evidence to support this conclusion will be presented in section 5.12. 100

SECTION 5.1

INTRODUCTION Approximately one hundred and fifty manganese nodules, mainly from sites from which a nodule has never previously been studied, have been analysed for a variety of elements, These are :- Mn, Fe, Ni, Co, Cu, Pb, Ba, Mo, V, Cr, and Ti. In addition, the water and volatile content of the nodules (loss on ignition at 850°C) and their detrital content (hydrochloric acid insoluble residue as weight percent) have been determined. The analyses are given in Appendix 2 and the analytical methods used are discussed in Appendix 1.

In addition to the nodule analyses, approximately two hundred sediment samples found associated with the nodules (i.e. were present in the same cores) have been analysed for Mn, Fe, Ni, Co, Cu, Pb, Mo, V, Cr, and Ti. Calcium carbonate and phosphorus determinations were also conducted on the sediments so that the element determinations could be recalculated to exclude these two components. In the case of phosphorus the values were so low that recalculation. was unnecessary. 101

SECTION 5.2

DATA PROCESSING

In view of the considerable amount of analytical, data obtained during the course of this investigation, it was decided to treat it in a statistical manner. This was accomplished using an I.B.M. 7090/1401 Computer of the Imperial College Computer Unit. The programme for the statistical treatment of chemical data was that in current use in the A.G.R.G. Imperial College, and was devised by Garret (Unpublished Ph.D. Thesis, University of London 1966).

The treatment of the data was as follows:- a)Histogram frequency distributions for elements in both nodules and sediments were computed using both log and arithmetic data. b)The arithmetic and log means,variance, standard deviation,skew and kurtosis of each element in the different groups of samples was computed. 102

c) A matrix of correlation coefficients for all elements in each group of samples has been calculated using both log and arithmetic data.

The analytical results obtained during the course of this investigation have been processed in a number of groups. These are:- i) All nodules ii) All sediments iii) All clays iv) All carbonates v) All surface clays vi) All surface carbonates vii) All buried sediments adjacent to a nodule viii) All buried sediments not adjacent to a nodule

In addition, the data have been subdivided into, smaller groups for reasons discussed later. Further, the data have been subdivided into regional groupings discussed in Section 5.11, and processed separately.

Factor analysis was also performed using the I.B.M. 7090/1401 Computer (see section 5.4).

Analytical results presented in this work are expressed on a weight percent air dried weight basis in the case of the nodules, and on a weight percent oven dried at 105°C weight basis in the case of the sediments, unless otherwise stated. 103

SECTION 5.3

ELEMENT ABUNDANCES i) ELEMENT DISPERSION PATTERNS The dispersion of elements in nodules and sediments has been investigated in order to establish the best way of expressing their mean concentrations in each deposit. The dispersion of each element, using. arithmetic and log data, has been plotted on histogram, the log histograms being illustrated in Figs.5.1. and 5.2.

a) Manganese Nodules Using arithmetic data, all elements determined in manganese nodules, excluding Mn and Fe, but including the detrital constituents and the loss on ignition (water and volatile content) are positively skewed at the 95 percent confidence level (table 5.1). Using log data Fe and Mn have small dispersions and are negatively skewed, Fe more so than Mn (Fig. 5.1).. These elements tend to approach a normal distribution. 104

Nodules Clays Carbonates Arith. L06. Arith. Tog. Arith. Log. Mn 0.314 -0.739** 1.560** -0.139 0.875** -0:199 Fe 0.181 -0.828** 1.351** -0.352 0.926** 0.113 Ni 1.359** 0.108 1.685** -0.39 1.381** -0.719** Co 3.047** -0.005 -0.390** -1.784** 0.445 -0.795** Cu 1.179** -0.519* 1.376** 0.339 1.539** -0.372 Pb 2.942** 0.049 2.613** -0.331 2.088** -0.003 Ba 3.313** -0.119 Me 0.868** -0.481** 3.758** -0.169 4.658** 3.077** V 0.803" -0.813** 0.602** -0.568* 3.194** 1.086** Cr 2.838** 0.372 2.049** -0.202 2.442** -0.014 Ti 1.076** -0.485* 1.815** -0.857** 1.120** -0.606** L.0.1.0.593** -0.352 Det. 1.183** -9.689** P 2.205** 0.103 2.998** 0.003

Table 5.1: Skew of elements in manganese nodules, pelagic clays and pelagic carbonates, using arithmetic and log data. Significant at .05 level. Significant at .01 level. Ni Cu Ti lim.M••••••1

50- 50 - 50- 5 0a.

MIN

1 3.2 7.1 14.7 321 707 1470 3210 7070 14700 32100 147 321 707 1470 3210 7070 14700 32100 147 321 707 1470 3210 7070 14700 32100 70.7 147 321 707 1470 707 1470 3210 7070 14700 32100

Co Pb Cr

50- 50 - 50- 50- 50- yo .11E=MMII=MEr 111.11M•11

1••••••=m,

3. 2 7.1 14.7 32.1 321 707 1470 3210 7070 14700 32100 32.1 70.7 147 321 707 1470 3210 7070 70 147 321 707 1470 1.5 3.2 7.1 14.7 321 70.7 147 Fig 5.1 Distribution of elements in manganese nodules (Mn & Fe in wt percent; remainder in ppm) 106

Of the minor elements,V was found to have the smallest dispersion, closely followed by,Flo,.each exhibiting a negative skew. The elements Ni, Co, Cu, Pb, Ti and Ba are morey,ddely dispersed and tend to a greater.or lesser extent to approach a log-normal distribution. Cr has a dispersion pattern different from that of the other elements being positively log skewed (Fig, 5.1).

These results agree quite closely with those of Willis and Ahrens (1962). However, these authors found Fe in their samples to be strongly negatively skewed on a log scale and suggested that it approximated to a normal distribution. The inclusion by these authors of two samples containing less than two percent Fe largely results in their dispersion for this element being more negatively log skewed than was found by the writer. Two groups of samples having Fe contents of approximately one percent were investigated during this work. Because of their anomalous composition relative to all the other nodules analysed, and because they were found in an environment different from that of all the other nodules, they have not been included in the general statistical treatment of the samples as a whole. However, had they been included, the dispersion of Fe would have agreed closely with that found by Willis and Ahrens.

b) Pelagic Sediments The dispersion of elements in pelagic sediments varies depending on whether clays or carbonates are investigated. Using arithmetic data all elements,with the exception of Co, are positively skewed in both deposits(table 5.1),

Ni V Ti "11•1••••••=01

50 -• 50— 50-• woommarl, 50- 50

1111IMMOMP

.1.1MOIO111

4M1 OM

IIMM•mmoiMMI

lam••••••=111 1.111111 4 3.2 7.1 14.7 32.1 707 1470 3210 7070 14700 32100 147 321 707 1470 3210 7070 14700 32100 147 321 707 1470 3210 7070 14700 32100 70.7 147 321 707 1470 707 1470 3210 7070 14700 32100

Fe Co Pb Cr

50- 50a 50-o 50- 50,

EM.MOlommoOr

". •MEMMF dm. OM

•IIMNOMMOMp F r-

3.2 7.1 14.7 32.1 321 707 1470 3210 7070 14700 32100 321 70.7 147 321 707 1470 3210 7070 20 147 321 707 1470 1.5 3.2 7.1 14.7 321 70.7 147

Fig 5•1 Distribution of elements in manganese nodules (Mn&Fe in wt percent; remainder in ppm) 108

Using log data most elements in both deposits are somewhat negatively skewed but tend to approach a log-normal distribution (Fig. 5.2; and table 5.1). In the clays Co and Ti are strongly negatively skewed, and Co and Ni in the carbonates. In the clays also,Cu is positively skewed and Mo and V in the carbonates. Combining the clay and carbonate data, all elements except Mo are negatively log skewed. This probably results from the dilution of the phases containing these elements by variable quantities of calcium carbonate. The apparent positive skew of Mo largely results from this element not being detected in quantities below 2 ppm. by the analytical method used, (Appendix 1). Values below 2 ppm. were plotted as 2 ppm. and therefore there is a considerable concentration of values in the first interval of the histogram for this element.

c) Conclusions From this data it is evident that most elements in both nodules and pelagic clays approach more closely to a log-normal than to a normal distribution. In view of this it was decided that the log means of the various elements were more meaningful in terms of their average abundances than their arithmetic means. Accordingly, unless otherwise stated, log means will be used in this work. ii) ABUNDANCES IN MANGANESE NODULES The concentrations of the elements determined in manganese nodules during the course of this work (table 5,2) show good agreement with those found by other authors. 109

Max Min Log Arithmetic Mean Mean

Mn 30.28 5.41 16.03 16.63 Fe 26.32 4.36 12.56 13.11 Ni 1.98 0.136 0.545 0.662 Co 2.57 0.045 0.311 0.421 Cu 1.64 0.028 0.293 0.436 Pb 0.514 0.0046 0.041 0.068 Ba 1.58 0.018 0.177 0.227 Mo 0.080 0.0087 0.032 0.035 V 0.093 0.010 0.043 0.045 C-- 0.012 0.00o2 0.0010 0.0016 Ti 2.65 0.123 0.687 0.797 L.0 1.44.00 13.06 25,76 26.20 et 49.70 0.27 11.94 16.37

Table 5.2: Element abundances in 139 nodules from the Pacific and Indian Ocean. (in weight percent). 110

1 2 3 4 5 6 7

Mn 16.03 19.07 17.03 19.18 24.20 18.97 22.06 Fe 12.56 13.98 12.17 12.16 14.00 11.68 14.58 Ni 0.545 0.460 0.280 0.470 0.990 0.580 0.570 Co 0.311 0.282 0.100 0.360 0.350 0.280 0.340 Cu 0.293 0.550 0.310 0.530 0.400 0.330 Pb 0.041 0.017 0.090 0.100 0.150 Ba 0.177 0.330 0.180 0.150 0.310 Mo 0.032 0.022 0.052 0.038 0.068 V 0.043 0.035 0.054 0.044 0.059 Cr 0.001 0.0005 0.001 0.001 0.001 Ti 0.687 0.850 0.431 0.600 0.670 0.563 0.610 L.O.I. 25.76 17.10 25.80 25.00

Table 5.3: Comparison of average compositions of manganese nodules. (in weight oercent).

1) Present work, average of 139 nodules. 2) Average composition of 11 Pacific nodules, Goldberg (1954). 3) Average composition of 3 Pacific nodules, Riley and Sinhaseni (1958), presented in Manheim (1965). 4) Average compOsition of 31 nodules, Skornyakova et al (1962). 5) Average composition of 54 nodules, Mero (1965). 6) Deep ocean average nodule composition, Manheim (1965) 7) Deep ocean average nodule composition, Chester (1965). 111

The concentration ranges of the elements Fe, Ni, Co, Cu, Pb, Ba, V,Cr and Ti and the L.O.I. are very similar to , those found by Mero (1965) in Pacific manganese nodules, while those of Mn and Mo are a little lower. The average composition of the nodules (table 5.3) is also similar to that found by other workers. Howev=er, certain differences are apparent. These can largely be accounted for by two factors. Firstly, differences between nodules from different parts of the oceans and secondly, differing methods of data presentation, Mero (1965) has shown that nodules vary in composition throughout the Pacific Ocean but that large areas contain nodules of a similar composition (see also section 5.11). Thus averages based on nodules taken from some of these areas and not from others will probably not be compositionally representative of nodules as a whole., Comparison of the present log means with arithmetic means computed by other authors will also show differences, How- ever, in general these differences are small. The arithmetic means of the °resent data are presented for comparison (table 5,2). iii) ABUNDANCES IN PELAGIC SEDIMENTS The large difference between the maximum and minimum, content of most elements in pelagic sediments (table 5.4), can largely be accounted for by the variable proportions of calcium carbonate found in these deposits (up to 95 percent by weight).^,lien calcium carbonate free sediments (clays) are considered alone, the lower limits of the concentration ranges of all the elements are considerably raised (table 5.5). This observation coupled with the low concentration of the elements studied in pelagic carbormtes 112

Max Min Av.

Mn 2.4 0.044 0.337 Fe 14.0 0.470 2.92 Ni 0.160 0.001 0.014 Co 0.020 0.001 0.008 Cu 0.100 0.002 0.018 Pb 0.013 0.0002 0.0018 Mo 0.016 0.0002 0.0006 V 0.030 0.002 0.007 Cr 0.016 0.0002 0.0024 Ti 1.000 0.005 0.154 P 1.200 0.016 0.107

Table 5.4: Element abundances in 187 sediments from the Pacific and Indian Oceans. (in weight percent). 113

Max Min Log. Av. Arith. Av.

Mn 1.76 0.056 0.434 0.536 Fe 14.0 1.05 4.07 4.69 Ni 0.160 0.005 0.022 0.028 Co 0.020 0.002 0.0095 0.011 Cu 0.085 0.010 0.021 0.023 Pb 0.013 0.001 0.003 0.003 Mo 0.005 0.0002 0.0008 0.0012 V 0.020 0.003 0.011 0.012 Cr 0.016 0.001 0.005 0.006 Ti 1.000 0.100 0.300 0.333 P 0.400 0.020 0.097 0.118

Table 5.5: Element abundances in 33 surface . pelagic clays. (in weight percent).

Max Min Log. Av. Arith. Av.

Mn 0.640 0.050 0.226 0.276 Fe 5.80 0.470 2.45 2.850 Ni 0.030 0.010 0.0098 0.012 Co 0.016 0.0016 0.0062 0.0075 Cu 0.050 0.003 0.013 0.015 Pb 0.0085 0.0004 0.0017 0.002 Mo 0.0005 0.0002 0.0002 0.0002 V 0.013 0.002 0.0053 0.006 Cr 0.013 0.0002 0.0021 0.003 Ti 0.400 0.005 0.122 0.170 P 0.300 0.0 ?.6 0.065 0.082

Table 5.6: Element abundances.in 31 surfade pelagic carbonates. (in weight percent). 1 2 3 4 5 6 7 8 9 10 11

Mn 0.337 0.434 0.226 1.29 0.67 0.562 1.25 0.45 0.59 0.148 Fe 2.92 4.07 2.45 5.1 6.5 4.56 6.5 4.42 5.45 1.60 Ni 0.014 0.022 0.0098 0.021 0.023 0.024 0.032 0.015 Co 0.008 0.0095 0.0062 0.015 0.0074 0.010 0.016 0.0055 Cu 0.018 0.021 0.013 0.035 0.074 0.027 Pb 0.0018 0.003 0.0017 0.011 0.015 0.0060 Mo 0.0006 0.0008 0.0002 0.0045 V 0.007 0.011 0.0053 0.011 0.012 0.019 0.023* Cr 0.0024 0.005 0.0021 0.0062 0.009 0.0069 0.0093 Ti 0.154 0.300 0.122 0.420 0.460 0.425 0.730 P 0.107 0.097 0.065 0.117

Table 5.7: Comparison of average compositions of pelagic sediments. (in weight percent) 1)Total sediments, this,work. 2)Surface pelagic clays, this work. 3)Surface pelggic carbor,lates, this work. 4)Deep-pea clay akierage, Landergren (1964). 5)Deep-sea clay average, Turekian and Wedephol (1961). 6)Deep-sea 9e-limenc average, Chester (1965). 7)Pelagic cli.y avt.:oage, Goldberg and Arrhenius (1958). 8)Pacific sediment average, Skornyakova (1966). 9)Pacific clay average Skornyakova (1966). 10)Pacific carbonat3 average,,Skornyakova (1966), 11)North Pacific clay average, Tatusumoco (1957),reported in Wedephol (1960). Modified according to Wedephol(Goldberg and Arrhenius 1958, P193). 115

1 2 3 4

Mn 0.593 0.485 0.208 0.232 Fe 4.14 4.39 1.58 1.69 Ni 0.025 0.022 0.0098 0.0093 Co 0.013 0.013 0.0077 0.0068 Cu 0.028 0.029 0.014 0.015 Pb 0.0033 0.0023 0.0013 0.0011 Mo 0.0014 0.0017 0.0002 0.0002 V 0.011 0.0080 0.0054 0.0052 Cr 0.0038 0.0034 0.0016 0.0015 Ti 0.287 0.250 0.082 0.086 P 0.153 0.177 0.098 0.091

Table 5.8: Average composition of sediments adjacent, and not adjacent, to nodules. (in weight percent). 1)Average of 7 clays immediately adjacent to nodules. 2)Average of 28 clays above and below nodules. 3)Average of 8 carbonates immediately adjacent to nodules. 4) Average of 33 carbonates above and below nodules. 116

(table 5.6) relative to their concentration in the clays, indicates that these elements are not appreciably concentrated in the carbonate phases of the sediments.

Comparison of the average compositions of the different sediment types with the averages obtained by previous workers (table 5.7) reveals considerable similarities. In a similar manner to the nodules, the differences that do occur can largely be accounted for by compositional differences between sediments from different areas, and differing methods of data presentation. The high average values of manganese recorded by Goldberg and Arrhenius (1958) and Landergren (1964) are probably the result of the recorded inclusion of micronodules in a proportion of the samples studied by these authors.

The general similarity between the average composition of the present samples and those of samples studied by previous workers is significant when it is remembered that the present samples were associated with manganese nodules. This observation coupled with the fact that sediments taken immediately adjacent to buried nodules showed no overall compositional differences from those taken above and below the nodules (table 5.8) indicates that the presence of nodules within the sediment has no overall effect on the sediment composition. and iv) ENRICHMENT FACTORS The degree of enrichment of the elements determined in manganese nodules over their concentrations in pelagic clays, near-shore clays (data of Wedephol 1960) and igneous rocks (data of Ahrens and Taylor 1961) are presented in table 5.9. 117

Deep Sea Near Shore Igneous Clays. Clays Rocks

Mn 34 188 160 Fe 3.1 2.6 2.5 Ni 22 99 155 Co 33 239 155 Cu 13 60 53 Pb 13 20 27 Mo 36 33 33 V 3.8 3.3 3.6 Cr 0.18 0.09 0.09 Ti 2.2 1.5 1,6

Table 5.9: Enrichment of elements in manganese nodules over their concentrations in other rock units. (Ratios calculated on weight percent dry weight basis).

The degree of enrichment of elements in nodules over their enrichment in the other rock types and the differences between their enrichment in these other rock types can be broadly divided into four categories. a)Elements that are enriched in both nodules and pelagic clays relative to their,concentrations in the other rock types e.g. Mrs, Ni, Co, Cu, and Pbe b) Elements that are enriched in nodules relative to their concentrations in the other rock types but which vary little between these different rock types e.g. Mo. 118

c)Elements that are only slightly enriched in nodules relative to their concentrations in the other rock types, and show little variation in their enrichment between these rock types e.g. Fe, Ti and V“ d) Elements that are depleted in nodules relative to their concentrations in the other rock types e.g. Cr.

These enrichment factors are similar to those calculated for manganese nodules by Willis and Ahrens (1962). These authors found the elements.Mn, Ni, Cu, Co and Mo to be strongly enriched, and Fe, Ti and V only slightly enriched, in nodules over their concentrations in igneous rocks. Further,the present observations on the enrichment of elements in pelagic clays over their concentrations in other rock types are similar to those of Wedephol (1960) and Goldberg and Arrhenius (1958). Wedephol (1960) found Mn,Ni,ivb,Pb, Co and Cu to be enriched in pelagic clays over their concentrations in near-shore clays, while he found the concentrations of V and Ti to be similar in both deposits. The enrichment of Mo noted by Wedephol has not been found in the present samples,

These results show that Mn, Ni, Cu, Co and Pb increP7._ in concentration from igneous rocks; through pelagic clays, to manganese nodules. The ratios of the concentrations of elements in manganese nodules over their concentrations in both near-shore clays and igneous rocks are rather similar suggesting that the processes bringing about the enrichment of elements in pelagic areas do not apply to near- shore areas. 119

Elements that are enriched in pelagic deposits relative to their concentrations in igneous rocks have almost certainly undergone secondary enrichment processes and thus have passed through solution at some stage in their history. Conversely, elements not enriched in these deposits could be, but are not necessarily, present in the form of primary phases, and thus have not necessarily passed through solution.during their transport to the marine environment. 120

SECTION 5.4

ELEMENT ASSOCIATIONS i) THE RELATIONSHIP BETWEEN NODULE COMPOSITION AND MINERALOGY Comparison of the average composition of ten todorokite rich nodules with the average composition of seventeen birnessite rich samples, reveals considerable differences (table 5.10). Both Ni and Cu are enriched in todorokite rich nodules while Co, Ti and Pb are concentrated in those rich in birnessite. Elements such as Mo, V, Ba and Cr are equally enriched in nodules of both types while Mn is slightly enriched in the former and Fe in the latter 121

Todorokite Birnessite

Mn 19.53 15.30 Fe 9.07 13.78 Ni 0.985 0.390 Co 0.172 0.790 Cu 0.562 0.107 Pb 0.033 0.115 Ba 0.193 0.221 Mo 0.046 0.038 V 0.042 0.055 Cr 0.0010 0.007 Ti 0.403 0.943 L.O.I. 26.08 29.22

Table 5.10: Average composition of nodules rich in todorokite and birnessite (in weight percent).

ii) THE RELATIONSHIP BETEEN NODULE COMPOSITION AND DEPTH

The average composition of manganese nodules, taken at thousand metre intervals, varies quite considerably with depth (table 5.11). 122

No. of Samples 3 10 7 8 51 39 Depth Interval 0-1000 1-2000 2-3000 3-4000 4-5000 5-6000

Mn 18.06 14.40 14,39 15.15 16.33 16.68 Fe 11.76 12.69 16.13 15.07 11.92 11.51 Ni 0.318 0.420 0.322 0.427 0.614 0.636 Co 1.823 0.736 0.653 0.255 0.223 0.262 Cu 0.096 0.056 0.048 0.213 0.339 0.477 Pb 0.382 0.101 0.099 0.026 0.036 0.031 Ba 0.733 0.329 0.237 0.140 0.177 0.145 Mo 0.056 0.039 0.040 0.023 0.030 0.037 V 0.067 0.057 0.064 0.039 0.040 0.040 Cr 0.0004 0.0021 0.0010 0.0006 0.0011 0.0009 Ti 1.078 0.610 0.917 0.567 0.693 0.638

Table 5.11: Relationship between surface nodule composition and depth. (Analyses in weight percent). It can be seen from table 5.11 that the abundance of certain elements in manganese nodules appears to be related to the depth of nodule formation. Co, Pb and Ba are concentrated in nodules from shallow depths while Ni and Cu are more abundant in nodules from deeper waters. However, these elements do not show a regular response to depth, there being an abrupt change in their concentrations at around 3000m.in most cases, 123

Calculation of the correlation coefficients of elements against depth also reveals that certain element concentrations are sensitive to depth. All elements except Mn, Fe, Ti, Mo and Cr show some response to depth (table 5.12)

Mn Fe Ni Co Cu Pb Ba 'r' 0.14 -0.16 0.26 -0.61 0.48 -0.57 -0.49

Mo V Cr Ti L.O.I. 'rt-0.08 -0.49 -0.21 =9.04 -0.04

Table 5.124: Values of the correlation coefficient 'r' for elements in nodules against depth (all values of 'r' greater than .254 or less than -.254 are significant at the 99 percent confidence level.

The response of the various elements to depth can be divided into three categories. These are:- a)Elements that show no significant correlation with depth, e.g. Mn, Fe, Mo, Ti, and Cr. b) Elements that are positively correlated with depth e.g. Ni and Cu. c)Elements that are negatively correlated with depth e.g. Co, Pb, V and Ba.

The relationship of all elements to depth has been plotted on variation diagrams. 124

This was accomplished onthQ I.B.M. 7090/1401 computer of the Imperial College Computer Unit using the BNDO2D correlation programme of the Health Sciences Department U.C.L.A. In the case,of all the elements that show a. relationship to depth, the scatter of points is large. Ni and Cu show a curved positive relationship to depth (Fig. 5.3 and 5.4), indicating that they do not vary constantly over all depth ranges (see also table 5.11). By contrast, Co and Pb show a smoother negative relationship to depth (Figs. 5.5 and 5.6). By transforming the element values to logs a more lintIr relationship with depth results. Apparently, their concentrations are either log proportional or log inversely proportional to depth.

These element variations with depth could result from a number of possible causes. One could be that they are enriched in one or other of the two principal manganese minerals in nodules, these themselves showing a relationship to depth (Chapter 4). Another could be that elements are precipitated under differing environmental conditions related to depth also. However, irrespective of the causes of these variations it does appear that depth can influence the concentrations of certain elements in manganese nodules. iii) INTER-ELEKENT ASSOCIATIONS In an attempt to determine the inter-element associations in manganese nodules and their associated pelagic sediments, various techniques have been used. These include plotting variation diagrams and perform- ing correlation and factor analysis.

:- 13 VARIAHL:t. Deplatk1AU wt. 6975.:.:1" 2475.1,' 397,..J1 5475.00Z -525. 3725."r. 4125./i:'. • .4•41.4.11,14140,poodt."41 *.000 tt+Imool0. 4.....v. +•0410 Z6l-;.Z ;• + 2a.::..•1 1 ft▪ 19t3p4 1980' • 194:Z, OCV 194CZ.:C: . 1 1900.'LZ.• 1 1 186,'! : + • 1824.0]. 1620J.,:c..1 . 1781;J.CD..: 17800.:1 . . 17400•'0': 1717.,^,..nZ.,' -... • 16600.....L: + . 162 .G 162'' . • 15813,-3: . 1 . 1540).71 . 1 1 . , 1500.07 • 146..I0., 14602...0: • 1 • 14200..:J0:: . ▪ 13627.IZ.. il.301:.-:v. 1 1 • f 13400...C: . 1 1 11.0300,j.%: . 1 1 1240 C.)...... ; 4. 1 1 . 11022%.:,;* . 11131).u0. 1180J.:: :, • . emm 1140%;...:09 11 • 10(45.0-• 113nci.:1.: . 1 1 . Z1'...60.1 : + 1 . 913C7d.Z . 9800 ;-.• • 1 940,Z.Z Z., . 1 . 904/S.:O. • 1 1 1 . 8600.;;;),.: + 111 1 . 820.....00. . 1 1 1 1 1 1 . 7403.00-: 7430,...V... . . 74Co....:' 1 1 1 T0U.,104 . 1 1 , • 1 . (11,..::. 660:.t:.: 1 1 6200.C..>: . 1 1 54;....,:. 513J:.%. 7: . 1 1 3 1 111 . .. • 1 • 1 1 11 1 . 53.%.7.:: 5400.0 1 1 1 1 50!17.:3'• • 1 1 i ".•: 463C.Cie: * 1 . 1 1 2 424:. 1 • 38J4..:. 420Z. 1 1 34 Aol.cnv . 1 1 11 1 1 . 2 1 11 • 3400 10 1 1 1 1 ! 1 •♦ 26Z.....: 3,100.' ): . . 1 1 1 : 4. 1 1 2 1 • 22).,0. 24O:, 1 1 1 1 . 18:'...: • 220Z C:: . 1 . 14:.. . 180:.:e..7 • 1 1 1.;„,.. 140J.I1: . 6.:• I'd ., .11;,a., ; . _ + io. • Iesdre.*•••••••..4.••••+1.."4.0.••••••••••••+•••01.eoef4141141*.woo•40tost Coof.0.••••+1.....4.11,•••*".“4.4144.••••.0. 3975.10.; 541S.01 69fj. . -,25.,,,,'' Ii5.D.J0 -...—. 2475.0/1 4725.0N. . . 6225../J, 22i.'''.:: 17250,):. 3225.1J: Fig 5.3 Variation of Ni with depth

w4RIA6ir Depthy-I, m. 2475.W:7. 1,473.6.1% 172n. • 3225. 4725.0C

+...... +....+....+....4....+....+...... 4000 .+1, 0 1.04 0,6 40,04106.+4,00....00 4 .900, • ▪ . . .• 17 1 . 16c. +

•1420';.t.",.. 134•.,L1:. 26'- . 221:.*:' • •

c 1 Q. 911C.: • . • A. , . . :). azo::), • 1 + .111 %I . 1 1 1 74 7C..)0.uC.• . 1 1 7 1 1 021,...CC. • ▪ . 1 . 1 540 .Ci . 1 1 2 11 . 460L.: 1 1 1 1 461 42C...);'- • 1 III 1 I • 422.,..- . 1 1 2 1 1 1 1 1 1 111 1 1 1 1 1 II 1 22060.3,', + 1 1 1 • 121 2 1 . 1 1 11 1 • - 100G.)C▪ • . 1 1 1 1 1 1 2 1 12 , 1 11 1 2 . 2C....,LO. + • 1 1 1 1 . • —23:.C% . —1000.66- . . —14MGALu . . —1800.00., + .4 —16040▪ 06 ••••+••••••••••••••+•••••••••••••0.••••••••••••••+•••••••• +•••••••••••••••••4••••••••••••••••• —525. )0O 975.000 2475.000 3975'000 5475.001' 69750.0:.. 225.000 • 1725.000 3225.000 4725.000 6225.101. Fig 5.4 Variation of Cu with depth

• .AR1Ahit D epth ,,,,,,-- 2 • m.. ' 247:--1 3+/F,.%.1 5474.J:1 697',... -525. 2_. 175. 622i. ,.. 225..:••• 1725., 3225..,) 4725.)1 , ••••••••••••• ...... +....+....+....+...... • + 27922.r:4, 279:C.uC - •+ 27314..-. 2733u.:0, . 24720.O3U 2471:J. . 241i2...C. 2oln.s.. . 25500.20.: i5520.0.: • 1 1 , • 2495:.....) 249, C .C:. • 243C:..J0.: 2435:...C:. . 2.37:.4.2C- 2J 7.7,.c.:.C 2310 .000 23100.2G: . 221::.,: 2250 .7.:6 . , . + 219:1'..r, 2190 '...2•: • 213•:11.,:2. 2133.:.J2. . 20723.00i. 2C720..: . . 2.:17:: 2013.c.:' . . 195)2.,4 1 ,2SOC'.C2 . • le9..:1...,?: 1890!..u-, + 183::.10, 1133C."..• . • 177',..:-.. 1771,...5 ., . 1 . 1715').J2. 1"7130. . . . 14'1).J.::- , 16SW.C:, • + 1515909.^_C: 159C .5..-.1, • 1 • 153::.'" e 153r1.2.-...-- . • 1475. A, 1477,:•:1 ,. • ad614121.C. • . 135-.."...:V. el13500.Cil,. . + 12'12 J5 '''129(E..:,:, + 1 . 121.0j, 123n)...-2. . . 1172.-,.:.:. ffi ll70:.:. 1 . 11.: .. 2r.. W 111 ^- --. . . 1.5:/..-.". 9920.,0: LP10512.2 . 1 • 992.7' . ....:' + . 93:::...7- . 1 . 1372::.%., 1 1 1 1 1 e712...... 1 . d1 - J.:: . 1 . ra0.)..,(:•- 1112r...:.. 1 1 1 Th.22. ,. . 1 + tr.r.. .:., 69r:::... .f. . a 1 . 63CO.,2 4322..• • 1 • 57 —,J:. 570.:,‘!:- . 2 1 1 . 51.::02:: 1 1 . 45:2.C:: 51r,...:.:2"% . 1 2 212 11 1 450:-,:.:. i il 1 1 3922...t,:- 39C.J.L...' + 1 1 1 11 21 • . 332...: 1 . 2/5..01, 33132.:5; . 1 1 •• 1 511 12211 1 • 2706.2.2. . 23 3 1 1 :11 . 1 . 21:.2.1:::. 210:.•'' . 1 1 1121 1 1 1 . 1502.2:0 2 1 1 + 92..'.:: 152'.J. 2 . 1 12 4 1 3 r + 1 1 1 . 3.22..2.1 30900. 2 . : -32:.:.1 -31:- ...... -9GC..,- 21, -90.:.. ..:. • -21(7;..),:. -151 0...7. .. -211:.. :. .0.....•....4.....+...... +...... 4.....4...... +.... 6975.: 1.1 N) 2475.o0U 3975.400 51475.0C3 -.)21. ,,' 975.:ru 4725.cr* 6225.1 '0: • 'NO 225.. 0: 1725.20.1 3225.:2'' Fig 5.5 Variation of Co with depth

Depth m. VARIAFLF 6175..)-,.. n 397.'. ),, .047t.J).: 175.,. 24TS.3: 4125.0A1 1,225.')O- 172i.2U: ?725. t...... t...... 4 .25..01 ▪ +....t.w..t... OOOOO

,..>5: ,.. • . t.:).• .C)... cli...: 565'..•,11... t.,:::' 57:).C:iC t J5..•'.:,-!,.. o 54)./e0T.. 1. • 5.52y:S 44:,;13 J, 34 .....•,::- 7)2S .. S. . 1.95:!...,:.: n11,.% 1 • 48)4oV...., 4'11.• - • • 4155,.(...:.: 411n. 3 + 145(:;,... 4t,5 ". - 435C.:C.: k:..o u3'3:•• ., I 4'72 ...:'' 39;.C:: 4.:1S:. . + 3151,',.: ,5 .::.— 36:.'...'/.. -

1 • .3:1::.-.3 _)15:.:., 1 265::...":- 27..,:.:2'- , Ce.,3,. . + 2S',"..C:.: G .777 ...„` 1 1 k...... ,: ., ...., 5 .., 225D.'::,.: Li1.7,.,2 . • M!....-' i 1 • 10:J.7:,: . dft, 135:,.. • 1 1165.1•C-2,, ad , - a. I e 5 . .. ' • 1 135::, ..: c. 15::•:: • • 1 1 11 4. 1 : .::6 , ..:., 1 1 1.5,5L-L: 1 5.• 11 11 1 90C.':i0C., 1. S : . — • 1 2 ...1.:, 1 1 75:. 1 1 12 11 11 4Cc.C5; cfl7.:,. 1 1 1 75.,.. Ill 451....iliJ 1 2. 111 23 11 1 t,';',.... • S00.33.; 4';':o. 111 1 11 1 2 112 122 1 1 11 1 1 150.C7,5 1 1 1 1 3 2 217 1 11 ..: + 1 21 15.. 1 12 1 -15J.60::.' : . . -50U.C,C,:. -15 . + -453.:60 -W:u.00,:.1 • : -61:.:. .-90Q. :Aci -/-,'„ , .-105G.C6C:

+ o4o.oefoome....oefoolp.. ••••••••••••••••••04•41,eas+.000'.".11. -127,...k 0'.....+.....+4.....e41,;•.4."4+e" 5475.000 697S.0J* 2475.310 3975..W 6225.'70^ - ',.. _ 1r5.rw 3225.:100 4725.00C . .72,.'- • . 172i.C'r Fig 5.6 Variation of Pb with depth 129 a) Variation Diagrams The construction of variation diagrams is a useful preliminary step in attempting to correlate pairs of variables. Using the I.B.M. 7090/1401 computer with the BMDO2D correlation programme, all the elements in manganese nodules have been plotted against iron and manganese. For reasons.of space not all these diagrams can be included. However, some are of sufficient interest to warrant comment. i) Associations with manganese. The elements Ni, Cu and Mo show a good positive relationship to Mn, (Figs.5.7, 5.8 and 5.9). The scatter of points is wider in the Mn and Mo,and,Mn and Cu,diagrams than in that of Mn and Ni. In addition, in the Mn and Ni diagram there is a better linear relationship between the two variables than in either of the other two diagrams. Plotting Mn against Fe (Fig. 5.10) a negative relationship is seen. However the scatter of points is very wide. ii) Associations with iron Element associations with iron are less clear than those with manganese. There appears to be a positive relationship between Fe and both Ti and the loss on ignition (Figs.5.11 and 5.12). However, in both cases the scatter of points is very wide. A positive relationship between Fe and V is also possible (Fig. 5.13). Plotting Co against Fe no significant relationship is observed (Fig. 5.14). However, if the high values of Co are excluded a possible correlation exists between these elements.

VARIABLE 111/111 ,,,,,RIAhLt 1 p p 3 27;n)3.4 147001.3,.3 2T,7330.0)0 267'.0t.3:3 3aJ01.L..: if00..00,; 117001.000 1(7000.:)3 237100.00„) 297:0,%))1 +•.••+..••+....+....+••.•+••.•+.••.+••..+•.••+. •••••••••••••••••+•••.+••••+•• • •+•••• •....•„"+"..4. + 206)7.000 1 1 . 1980?. 5S,-, 1 1 190C.007 1 1 + 186%.(.0., 18203.,:i 17800.:30 17400.00:: 177/1.;.00.. + 1660 .0J . 162S0.00 •158 0.00„ 1 1 1 •15:;00.30 ♦ 1464.00:. . 142VC.00:, . 136:10.CC: 1 1340,5.00: 1 1 + 126.:,40,.., 1 1 11833.0;3 1 1 11010.00 1 1 + 1 . 10274.003 9400.00) . 943J.73:: 1 • 9C7:0.30. 860;.C,S + 1 1 + 8600.;,0:. 8212.. 1 1 11 ;2: 780c.z,o, . 1 1 1 7833.00:. . 1 11 1 11 1 . 66%.C,33 620.00. . 1 • 623.000 1 1 5800.0 541L.:".0C . 1 121 2 2 1 • 54.33.300 501.;..4" 1 11 1 11 1 1 . 510:.71c 4600.000 + 1 1 1 1 1 1 1 + 4e.'0.300 4200.00: . 1 11 1 1 . 4203.03.1 380G.CO, 11 1 . 380).:0;; 1 11111 1 1 1 1 . 3400..':01; 300C.1;0:. 1 1 1 11 . 3L0j.000 2600.007 + 1 1 1 + 2603.000 22U.CC,, . 1 1 2 1 1 1 • 22C0.30., 1800.0: . • 1800.030 1400.iJ0i . 1 1 . 140:).03L 1000.0O3 . 600.00,, + +ed."...... "+*.e..+.1,1.0+:0000+0000+0000+60010.11101110 , 4...... 4...... •..... 27000.006 87300.000 ' 147000.000 20000.0.70 26790C.000 327)00.01; ,7: 33: 117001.11O 177100.030 . 237000.00C 297300et00 Fig 5.7 Variation of Ni with Mn

VARlAtilt: Mn V1tillii'LL 1 WI) rin 267;.JC.,D 117)C;').1 ) 177:03.0') 23700.nd 297000.000 182:).7.JO'

1661: . .

15o,' 1 15trn... . . 15JOD.SJ. 14.3C".J0 . + • 142Ca.--, J,. . . 12600.-Z.: . 1220.).J1, + 1 . 1147: E 1 . 1 1 1..,2oJ.,c • + . 1' 1 94Csi.Z10,: . 1 1 Z6,.. 1 r (.)7t1JJ.ly + 11 1 1 71360.7)v 1 1 1 1 1 1 1 O6' + 1 1 ♦ 2:;J.E1 . 1 1 58"- 2 1 1 1 1 541,..CGL . 1 1 LOi . 1 1 1 40C).C7:. + 1 1 1 1 1 1 1 1 1 1 1 1 . 121 1 1 1 1 . 1 2 1 1 i 1 1 1 1 1 + 22U4..," 180:.C6 , . \L 1 1 1 1 12 1 1 14,';,-)..A% • 1 1 2 1 1 • 140Z.L1. • 1 2 1 1 2 1 2 11 3 1 + 121

+ 4...... +....+....+....+....+...... +. ..+....+....+....+...... +....+,....+....+....+....+ UT qfl..,.. 1147.))0,...... ; 2:7v)1. o., 267MC.00.:, 327)...... ''.',. 117,7T7.00,:, I77' 0.?..'.: 2S7:2,.,-,-_ 29V,0'..0: Fig 5.8 Variation of Cu with Mn •

• .. ,i' ppm

le,I' ;' I;, 7,-,. C.,':: 11,'·· .. 117 2:,,7 "),. . 2,Q7 ,.. -" ...... t ..... t~ .... ~ ...... ~ ... t ...... ~.# ...... ~ ••••• : ...... : .. + •••• t •••• \- •••• + ...... + ..... +

2/1",; , .,.- 2 ,~ 1 .; ,; ,:, ~ : ... tv:" ~'~ •• ~ j ). " 21'l:":'~.C'~ .,. "J ,,' : 2L.', +? (,~ 201 ~'):. '( .2,,7; , 2 v 1 _ .... ,' .,:J.,\'... ,.

2 u I) ~\-:", • ..-1.',. 2~~:",:~.·,~ t ~I~ Y ; .... _ 2jl~; • " .';'.".' .. :' 2.51 J::. ;;, .2; 1 " ns ~". ',- 2 t 1C'" ... -, - 210 : z" (', : : • , 2.1:: .'

1 :}>"; "~" : .. J 1 0')': _ • ~ 1 d':" ... ( :" ,: : 1 77 ;0". 1/1;' .. ~ lo~_~:.' 1 ~t;: J,:. _. bj;:',.: ' 1 ~ ,,:,'-: ~. l"" 141C • 1 j:)>,# .... , • ~" 1 ;. 'l ',~ ,.', " 12~~'~(,. _', 117 "',.,: 1 1 1 ~~" .'-', 1 j~:;' .' '

j,) ,~, ~1, ' t: 7 ... '.; ... ~ , ~.1 " •..\. c 1 ~ : .• ,I" 7, ,.,' IS .. " ~ • (I:L' •...... '1. 'JO' ' .. n~ .. " J. (j : ... : .... -' ~ ') 7 .', ,\. ') ?,~ .... J. ~ " ,1 ".:' :> L.; • ~: • of -) ...... ' ) ~ .-.9':' .... O' ,.1 ... _ .. _~",t3 . '. ~.

: r ~' " • rf.;" Z1/~;' .:." - 21." •• " j: 1 ) : ! '. _ • '~jjj • .:'~. " ,/'.".1 •.;~_ } ...,' ... , • + ...... t •••• + •••• + •••• ~ •••• + •••• t •••• t ...... + •••• + •••• + ••••••••• ~ •••• + ...... - I '.J 147·,)').)\)~· 2J1.1 ..'·j.jIJ) :!blvt.t.utJ'J j21,J,)J ... ~J ) { ~ .. ,-. 117,":"",)" 177'k ... )) 2,H:,):.r,r,,1 2·H~~,;."'1;, Fig S·lO Variation of Fe with Mn , . 4,4ARJAPti Fe VARIABLE 2 FII) M 11 3')Q.• .. 63-10.0,7. 123000.00 . 163001.600 44i/36.00e 333 2.1.:J1 ?..3.3. ...0.: 93001.060 153303.000 213000.000 273100.133 4-.4...... 4....4....+....+....+...... 4.....4.....+....+....+....4...."+....4,...•....4.....4 26633.30e 4- + 28600.003 2620'3.33: OPC) . 282:J.33: . 27430.300 . 27034.30. 1 . 24430.00,', 4. 4. 258333 252.): • . 25233..300 . 2.443.03,31 2433.▪33 . 24360.000 . 2340).L13 2260.7.0, + 22E403.033 22233.33: . 222:J.30, 218C.3.60,. . 21600.0% t 21.:..333 20400.600 + 1 4, 1960.;.603 9273.3J' . 19206.604 643 • . 1883' -. • 1,.. 18603.003 ik - 80C,0.▪3: • •18813.000 11 .• l . 182:)3.303 1 . 1580.:.COJ 1 ...... 15:,33 - 1 1 . 14403.004 1 11 + 13823.:QJ 1 1 1 1 . 1320,3.633 281Q.W 1 1 1 1 N.128.'3...D. I 1 1 12.330.30 200:.C3' ,• . 114.::.::4 1 1 ' 1 , . 1 111 1 1 , + lue3o.so..; C20,.:2 1 1 . 10203.00. 1 1 1 1 1 : 9403.00u 9010.33 1 1 1 I . . 1 1 1 . 8400.C33 843Q.Y, 7833.,21:: 1 1 1 72.003 1 1 1 1 2 1 1 1 1 • 457,.J.:.7 4,30Q.CC. I 11 11 • . 44;00,333 1 1 1 11 1 •5403.000 514%.c.-J• • 4830.063 44803.....); • 1 1 1 11 1 1 1 1 1 14202. 2c: 1 1 11 1 1 • 3602.22 1 1 1 1 1 1 . 3850.003 • 1 1 111 1 ir • 3Q30.333 2leC 3.22- 1 1 1 1 1 1 • litigU..!: 1 1 . 1200.063 1213..)3' . 660.306 . Q. . -400.33,1 , • • -1233.030 4-•••••••••••••••••••••••••••••••••"+••••4• •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 3. 43:01.3.V 123000.330 18300o.004 2430.n.000. - 303000.330 i'.:,.:, ..."r 93011.000 , 153)C0.001 213000.100 273103.010 Fig 5.11 Variation of Ti with Fe

ppm IL) NJ rs,wp..) N IN N A) A/ NJ A) Cod WU, W LA, 1.•1 U4 W U. W U• {Jo W FFFF cr.c.rv.r.c CC C. NW F CVA C• V CO 0) .0 C. NI NJ WF LT o. CD 0 0. -• UFF LP 0- V 0 ad C P ••• I, LA F 0- V 0 FN ClCO 0' F NC' CC 0. N) 0 CO P FNf CDPCNC C.P • cn cr CA CT. o—r r CL C.c a, a c.c,or CIC..c.C.OnC C. C.C.C/C.C•C•k.JC,C.l. rAt.c.••C,C.C.C.L- C.CA, C.C.r C I I C, 0 C)C., 0 0 0 0 0 0 0 0 e• 0 .3 CNC) C.) 0 0 CA 0 L.. c• cc L'• 0 C. 0 .1.• r-ccJcjc...c, NF C a.e: f.C:C•CDC C./..C.0c•r CA ••••••••••••••••••••••••••••••••••••••••••••••••••• 0 4'. C c • C• • C- 0 • Ca C r-

+ • • • • • • • • • • • • • • • • • • 4. • • • •• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • U. •- • c • • • C.

• • • • L, • 0 • • Al • LAC • 0 • 6, -• NJ • • • • %—• • C• • 1%) • .11.

.00 • 1. 6.• • C. • • 0 • NJ • r U ..I • C1 C2 -. NJ 1, ••• •• • 0 1•' • 0 111 •••• •••• 4 CO • 4.4 NI • ..i Irj • 0 : ...... • .0 • • ' I • • C. — a • • r 4 . • C2 2" 0 • • AI tr • U. • • L 0 • • 0 • • • 0 • • • • • 1 4, • • r• • Al • • .1 C • • {A • • IA 0 • • • • 1.".• • c• • + + • 0 • • Cc C • • c• • • • 0 A) • • CO vi • • ...•‘ • • LAI r• • • 0 0 • • 0 C. • • * ••• • • .) L) • • C. • Cc

L. • • U. C I • • I, • 166. • • / • • •—• • 1_1 • • • C • • • •.• NJ A) A.• NJ Ni N) NJ NJ NJ NJ Al V! CAC L•• L.• U. W(.. LA. IA U1 FFFi O IL) L.1 LP 0 V 0 CO .0 N.) V, 0 0 Cr .0 A 0 c..• r 0. 0. y r•1 Cr .r c, Cr C•• r C, CO r c cc 0, N Co C (_-• r V NJ 0 CC C• A/ 0 CC F Al 0 0. F NJ•• CC ..•.. _s C Cs 0 c r ces C, C CJ c C. C• r• • VU. • C c. C• C.. t.ick C. C• C, . r • C. 0 1•0,0,, •,•• in • C • L. C. • C. Cr' C-) C. C. 4. 0 C•'.11I C C. c 4._ 0 • "•• • • ‘, • • C.. L. C. r.• L. • • • • • • • • • • • • • • • • • • • • • • • • • • ..... • • • ..... • • • • • • • .....

.. el I 16, •61 1.• • - • C1.1 1C, 4 C.61 I • C, :I.. L. L. r.• •.1 1.3 I. .• c•I • • C. I • I • • • C C. • r.• l 1 C • • • • t .• •

S L- VARIABLE VARIAGV 2 ppm 9 Fe 63...),. .:1' 12.3.:21 183000.nC ' 24 .3C0C.300273000.noc332,1 ..'..!:C .- ....0: 93 C0.rJ07. IS3,00.J03 213000.000 .1-• L1,:,.CC._ + . + 99)..r. . 1,1).J.

. 95'.:6C3t: 930.CO, . : + • d9o..:1. . + 912....0, . 090.00o 850.%:2 . . 8S3.:.10 63:....- . 1 830.2,3, 81‘..6.-, • • d1...00,- 77.:.2C, p 1 . 7/0.000 75,..' .1 A. ., .•159.20., 732•0:,. • el 1 73C..C.O. + • ..117,1.7', 1 1 : f1v.2::. 69C.C3% . . . • i - .Z...• 1 1 . 694.:00 67:... . 1 1 1 1 673..2 65J.C.; . 1 1 1 654.,.: 1 • 3 . 1 + 21.:,:t 1 • 1 1 . 1 11 1 • 55C.COC, 1 1 71 1 1 1 : Zt:2i) 9/ 1 11 1 1 2 1 473.20C 450.'.:30 21 1 1 11 1 1 11 1 I 1 1 1 : ;;;.::: 123 1 1 1 1 2 1 1 .•39C.,i3i. 1 1 2 1 . 37:1,200 1 1 1 1 1 1 • 353.23 2 1 1 11 . 33C.013i. 1 1 1 1 1 1 + 1 .• 293.303. 1 1 1 1 . 1 1 • 2gij.) .tkt + ;12..,::: 190.103 1 - 170.00. 157.00C 1 + 1 • 90.000 • 73.00C

• 30.330

eo+dimeo+oeekt.044.0.84..0.•••••••••+seem+414meo+eeoe+e460."4.4.4. 63C133.000 123030.030 1830000310 243004:0000 3J34,43.JJJ 0:0C 03033000 1530000030 213000.000 27300000n ,Fig 5.13 Variation of V with Fe VARIA0L% Fe L ppm • 3 .... l, 63.: ... 123"%%0 1d3c,0i2 243:':C.C.:0 75'.7'... 1: 1'33. Y, '• 7,7.i 213)..7.).coc ...... 4...... • • . • • , 273b0::.G.:,c 3'?"':': 279313..)) + 2?3',:,,,:,.. . ' +4219C0600.: 267W.:',' . . 2675L.0:.70:0 2610Z.. . . 2551C.C:o". • 1 1 ;tr0'0".0'8Z 249:4.3 + + 24930.00. 2430.4...:.). . • 24300.000 237Cu...... Y . . 23700.00:. 23100.:0', . . 23100.000 2250C.::'.2 . 219^,1..UC • : ;1=:t)Oki 2131.:6;G.: . . 21300.00.: 2C730.,:40) . • 20700000 2014,,.. . 20100.00.: 1950:..1S . 6 19500000 769C:).:,:. + G 18300.00 . : 41:0:01 1770.3•00 . 1 . 1771.).:0. S: 1710C . • 17100.000 1650v.1: . . 16500.00„ 0.15903.4:: + 1 • 15900.000 . • 153C.:•.::' • . 153.).:.4:. IL 14700.', . . . 14700.33( ' 14100.::: . . 14100.00: 1.351C.:i..0:. • • 13500.00u o 1290....C7 + • 12910.0:'. 16,123^0..•n . . 12300.ox, 1170C.:::. 6 1 . 11700.0% 1110Z.LC. . • 0400000 1051C.:C,' . .I 990 503'.:03 00 f 99',:...:-.) I 1 9.30:41.::. . • 9300.005 87S,.00:' . 1 1 1 11 • 8700.000 V1::•..: 1 1 . 8to.D.01L 75'..L..:. . 2 • 75000000 690(:.::. + 1 + 690a.:!3t 61.,%...... • I - - 6300000 577.:..C. • 1 1 1 1 . 570.).30 510v..c*: . 1 1 1 .. - 5100.000 45CO.CC'. . 1 1 1 21 1 1 11 1 a 4500000 1903.40:' 3900.000 ' 3303.:0.: . 1 1 1 1 1 1 1 1 . 3300003 270.Z.:7, . 2 1 2 2 1 1 1 1 21 1 • 270000C 210;.3:-. • 1 11 12111 1 1 1 1 1 1 . 21006002 1513600..' • 1 1 13 11 11 12 . 100.000 91:..:C.: • 1 1 2 1211 1 1 1 1 • 100004 30:,..0: 1 • 1 1 1 . 303.000 310.C.,.: . . ••300.000 -900.G' • . . 9006001.. .-150.:.1:'::- . .21':'/...... + • : :2=00G +...... ,...... *.....+6.0...... +...... 0...... 661,...... +64.0.10..... !.'06000 630306000 123000.000. 183000.000 243000.000 - 303000.000 337OC.J00 93000000 ' 153000.000 213000.000 273000.000 ,Fig. 544 Variation of Co with Fe 138

iii) Minor element associations Variation diagrams have not been plotted for the minor elements against each other. However, their associations with each other can be seen from their associations with iron and manganese. In general minor elements correlated with either iron or manganese, are also correlated with each other.

b) Correlation coefficients The correlation coefficient 'r' measures the degree of correlation between any pair of variables assuming that these variables are distributed normally, or log- normally in the case of log data. It is evident from section 5.3 that most of the elements in both nodules and sediments are not normally distributed. In fact, the majority tend to approach a log-normal distribution, with some falling between normality and log-normality.

In spite of this difficulty correlation and factor analysis were attempted using both log and arithmetic data. The reason for analysing both sets of data was that most elements approach a normal distribution on . either a log or an arithmetic scale. In this manner reliance could be placed on correlations between variables of like distribution. It was also hoped that useful correlations between elements of unlike distribution could be obtained. i) Manganese nodules A number of workers have commented on the correlations between certain pairs of elements in manganese nodules. 139

Goldberg (1954) suggested from,analyses of 33 nodules, that Fe was correlated with Ti, Zr and Co, and Mn with Ni and Cu. Riley and Sinhaseni (1958) examined the data from which these conclusions were drawn and found that only.the correlations of Fe with Ti and Co were significant. Willis and Ahrens(1962) from their data and those of Mero (1960), concluded that there was a correlation between Ni and Cu and a weaker correlation between Fe and Co. A negative correlation between Fe and Mn was also observed.

The correlations obtained in this work are based on 139 nodule analyses. Correlation matrices using .both arithmetic and log data are presented in table 5.12.

From both correlation matrices certain features emerge. It appears that Ni,. Cu and Mo are strongly correlated with Mn. Further, Cr appears to be correlated with the detrital constituents of the nodules. Element correlations with Fe are less clear. Using both matrices correlations are found between Fe, V and Ti but not between Fe, Co and Pb.

Comparison of the arithmetic correlation matrix with the log matrix reveals few differences. Most elements are similarly correlated at the 99 percent confidence level on both. The principal differences occur in the case of the elements Co, Pb and Ba. Using arithmetic data there is no correlation of Co with Fe, while using log data a significant correlation between these two elements exists. In addition, the correlation between Co and Pb is stronger using arithmetic data than with log data, as is that between Co and Ba. *(6CT = 111 4 •uoTqp-eas aTqnTosuT pTo-e oyaoTgooapAH .-4aG - -41.10Ta @qq. 04 uTep OoT 'Teuo0-eTp atiq JO qjaT eqep oTqamtiqTav) 4 GaTnpou asaueOuem 11-T squamaTa JOJ saoTaqem uoTTeiaaaoo:qnic

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The reasons for these differences are not entirely clear but are undoubtedly in part related to the changing of the form of the distribution of these elements by transforming the data into logs.

The information presented above points to a tri parti.te division of the elements in manganese nodules. Iron, manganese and the detrital constituents probably represent the three principal phases in the nodules, and their correlation with the minor elements is probably reflecting the tendency of these minor elements to associate with one or other of these phases. However, it should be emphasised that the differences between the distributions of the major and minor elements leave these correlations open to some criticism. ii) Pelagic Sediments Previous work on inter-element correlations in pelagic sediments has been performed by Landergren (1964). This author has sl2own that a number of pairs of elements are correlated, and uses these correlations to deduce the sources of the elements concerned.

For the present purpose the sediment data has been divided into two parts, clays and carbonates. Correlat- ion matrices for both groups using log and arithmetic data are presented in tables5.13 and 5.14.

Examination of both correlation matrices for pelagic, clays reveals certain features in common. The elements V, Ti and Cr are strongly associated with each other, confirming the observations of Landergren(1964). Mn Fe Ni Co Cu Pb Mo V Cr Ti

Mn 1 0.425 0.550 0.330 0.125 0.354 0.530 -0.025 -0.359 -0.013 0.519 Fe 0.394 1 0.432 0.455 0.213 0.254 0.294 0.152 -0.118 0.282 0.393 Ni 0.568 0.277 1 0.510 0.659 0.405 0.601 0.382 0.106 0.361 0.435 Co 0.359 0.378 0.318 1 0.298 0.386 0.331 0.297 0.150 0.447 0.423 Cu 0.087 0.206 0.631 0.232 1 0.192 0.362 0.255 0.111 0.180 0.145 Pb 0.358 0.257 0.229 0.418 0.072 1 0.176 0.508 0.190 0.522 0.335 Mc 0.538 0.152 0.631 0.174 0.227 0.101 1 0.325 -0.117 0.104 0.500 V 0.105 0.155 0.340 0.309 0.126 0.402 0.490 1 0.600 0.671 0.048 Cr -0.155 -0.161 0.054 -0.093 -0.104 0.046 0.087 0.425 1 0.704 -0.438 Ti -0.029 0.174 0.157 0.288 0.019 0.373 0.083 0.555 0.670 1 -0.032 P 0.362 0.262 0.352 0.182 0.161 0.247 0.291 0.057 -0.386 -0.199 1

Table 5.13: Correlation matrices for elements in Pacific Pelagic clays. (arithmetic data, bottom left; log data, top right). = 90. Mn Fe Ni Co Cu Pb Mo V Cr Ti

Mn 1 0.549 0.695 0.720 0.540 0.613 0.488 0.303 0.213 0.409 0.611 Fe 0.617 1 0.619 0.560 0.614 0.738 0.392 0.558 0.748 0.875 0.273 Ni 0.587 0.494 1 0.825 0.799 0.670 0.402 0.414 0.446 0.645 0.663 Co 0.661 0.536 0.742 1 0.687 0.733 0.364 0.453 0.377 0.614 0.729 Cu 0.533 0.532 0.634 0.648 1 0.602 0.511 0.578 0.644 0.734 0.462 Pb 0.569 0.651 0.499 0.550 0.587 1 0.434 0.557 0.586 0.734 0.403 Mo 0.527 0.294 0.564 0.367 0.604 0.355 1 0.460 0.322 0.332 0.382 V 0.357 0.625 0.318 0.449 0.613 0.634 0.373 1 0.597 0.597 0.110 Cr 0.296 0.608 0.278 0.369 0.631 0.608 0.348 0.715 1 0.813 0.061 Ti 0.477 0.839 0.419 0.505 0.687 0.752 0.270 0.734 0.754 1 0.268 P 0.478 0.152 0.671 0.573 0.358 0.175 0.574 -u.002 -0.096 0.011 1

Table 5.14: Correlation matrices for elements in Pacific Pelagic carbonates. (Arithmetic data, bottom left; log data, top right). Tnt = 79. 144

The elements Fe, Ni, Mo and Co appear to be correlated with Mn but are not all correlated with each other. The associations within this latter group are not clear.

Both correlation matrices for elements in pelagic carbonates reveal that almost all element pairs are positively correlated. This is probably the effect of dilution of the phases containing these elements by variable amounts of calcium carbonate and reflects the previous observation (section 5.3) that the elements dealt with in this study are not significantly concentrated in the carbonate phases of the sediment,

c) Factor Analysis Owing to the difficulty in interpreting correlation matrices where a large number of variables are involved it was decided to attempt factor analysis of the analytical data obtained on both nodules and sediments. Factor analysis has become a generic term for a variety of procedures developed for the purpose of analysing inter- correlations within a set of variables (Cooley and Lohnes 1962), in this case the variables being the elements determined in nodules and sediments. Standard texts on the method include, Thurstone (1947), Carroll (1953), Kaiser (1958) and Harmon (1960).

Briefly, factor analysis seeks to explain the correlations among,a set of 'n' variables in terms of 'm' common factors, where 'm' is less than 'n'. This is accomplished by 'plotting' the variables in 'n' dimensional space and subjecting the resulting multivariate swarin to principal component analysis, 145

This involves placing an axis through the swarm along which the maximum amount of variance occurs. A second axis is constructed orthogonal to the first and so on, each axis accounting for successively smaller amounts of the total variance. In all, the swarm will be referred to 'n' axes (principal components) where 'n' is the original number of variables in the correlation matrix. However, at some point in the sequence of locating new axes in the swarm, an insignificant amount of variance is found in the remaining dimensions, thus reducing the total number of dimensions required to explain most of the variance.

A number of princip'al components are selected for rotation, the actual number chosen depending on the amount of correlation accounted for by successive princip.P.1 component axes. These are rotated, in the present case according to the Varimax rotation scheme of Kaiser (1958), so that some of the variables are maximised on one axis and minimised on the others. This is termed the best estimate of 'simple structure'. The end product of this operation is a series of factors upon which the variance of each of the original variables is loaded. Variables with high loadings on the same factor tend to be associated, while the converse applies to variables loaded on different factors. The computer programme used to perform this task was COVAP ( Columbia Vector Analysis Programme) of Manson and Imbrie(1964). i) Manganese nodules The correlation matrices of both arithmetic and log manganese nodule analyses have been factor analysed. 146

Using arithmetic data it was found that 81.9 percent of the total variance of the elements determined could be explained in terms of five rotated factors(table 5.15).

The largest factor contained high loadings of the elements Mn, Ni, Cu and to a lesser extent Mo, further suggesting that these elements are associated in manganese nodules. Factor two is heavily loaded with Co and Pb and to a lesser extent with Ba. Other elements are either weakly or negatively loaded on this factor, iron included. This suggests a lack of association between Fe on the one hand and Co and Pb on the other. In view of the response of Co and Pb to depth this factor could be tentatively interpreted as a depth factor. Factor three has high loadings of Cr and the detrital constituents of the.nodules, confirming the observations made frcm the correlation matrices. Factor one also contains a proportion of the detrital constituents but the loading is rather weak. Factor five has a high loading for Ti and a weaker loading for Fe. All the other elements have either very weak or negative loadings on this factor.

Using log data and rotating five factors the results are very unclear (table 5.16). Again Mn,Ni and Cu,and to a much,lesser extent NO,are loaded on the same factor. However, here the similarity with the arithmetic data factor matrix largely ends. Factor two is also loaded with manganese, this time associated with Mo and Ba. Cr and,the detrital constituents are loaded on different factors, three and four respectively, these factors containing weak or negative loadings of all the other elements. Rotated Factor Matrix Factor Number 1 2 3 4 5 Sums of squares down columns 1.529 2.417 2.133 3.479 1.096

Variable Communality Name 5 Factors

Mn 0.792 -0.159 -0.015 -0.338 0.796 -0.137 Fe 0.836 -0.275 -0.175 -0.314 -0.704 0.368 Ni 0.863 -0.003 -0.106 -0.016 0.904 -0.186 Co 0.839 -0.190 0.823 -0.230 -0191 0.189 Cu 0.828 0.186 -0.184 0.047 0,870 0.006 Pb 0.827 -0.016 0.876 -0.190 -0.131 0,074 Ba 0.699 -0.369 0.698 0.037 0.273 -0.004 Mo 0.756 -0.581 0.266 -0.198 0.547 -0.100 V 0.858 -0.813 0.266 -0.046 -0.269 0.229 Cr 0.804 -0.206 -0,017 0.825 -0.270 -0.091 Ti 0.889 -0.145 0.240 -0.024 -0.337 0.835 L.O.I. 0.793 -0.179 0.377 -0.664 -0.300 -0.296 Bet. 0.869 0.357 -0.258 0.815 -0.005 -0.104

Table 5.15: Rotated factor matrix for elements in manganese nodules. (arithmetic data). 1 4E

Rotated Factor Matrix

Factor Number 1 2 3 4 5 Sums of Squares down column 2.202 2.377 1.566 1.188 2.698 Variable Communality Name 5 Factors Mn 0.768 0.180 0.555 -0.412 -0.032 0.500 Fe 0.755 -0.513 -0.260 -0.206 0.048 -0,616 Ni 0.870 0.370 0.367 -0.141 0.075 0.757 Co 0.759 -0.731 0.299 -0.132 -0.164 -0..302 Cu 0.831 0.191 -0.039 -0.077 0.210 0.862 Pb 0.485 -0.406 0.236 -0.116 -0.458 -0.201 ha 0.661 -0.046 0.809 -0.020 -0.055 -0.006 Mo 0.773 -0.054 0.814 -0.231 0.002 0.233 V 0.748 -0.442 0.562 0.158 -0.065 -0.456 Or 0.812 0.048 -0.054 0.871 0.115 -0.187 Ti 0.864 -0.908 -0.068 0.063 -0.070 -0.159 L.O.I. 0.820 -0.055 0.280 -0.663 -0.069 -0.542 Det. 0.885 0.063 0.027 0.089 0.931 0.075

Table 5.16: Rotated factor matrix for elements in manganese nodules. (Log Data). 149

There are no heavy loadings of Fe, Co and Pb on any of the factors, Co and Pb having weak loadings on factor two and all three elements with Ti having variable negative loadings onfactor one.

ii) Pelagic Sediments As in the case of the nodules both arithmetic and log correlation matrices have been factor analysed. There is less difference between these two rotated fact- or matrices than there is in the case of the nodules.

Using arithmetic data for clays and rotating four factors, a number of features emerge, (table 5.17). The elements V, Cr and Ti are all heavily loaded on factor two, again pointing to the strong association between these elements in pelagic clays. Factor one is loaded with Mn, Mo, Ni and to a lesser extent P. Factor three is loaded with Fe, Co and Pb while factor four contains negative loadings of most elements.

Using log data (table 5.18) V, Cr and Ti are again all loaded on the same factor but this time with Pb. Factor one contains the major portion of Mn, Ni and Mo, but again with Pb included. Factors three and four contain weak or negative loadings of all elements.

Using log data alone on the carbonates and rotating two factors (table 5.19), 74 percent of the variance of the correlation matrix is accounted for. There are moderate to heavy loadings of all elements on fact- or one an: n,2.g-.',tiv,J lo-,dings of all elements 'on factor two. Ibis is eisily explained in terms of a carbonate and a non-carbonate factor. 150

Rotated Factor Matrix

Factor Numbers 1 2 3 4 Sums of Squares down columns 2.235 2.326 2.089 1.451 Variable Cumunality Name 4 Factors. Mn 0.725 0,746 -0.122 0.391 0.024 Fe 0.520 0.133 -0.089 0.679 -0.184 Ni 0.874 0.647 0.143 0.182 -0.633 Co 0.635 0,091 0.105 0,758 -0.204 Cu 0.928 0,078 -0.033 0.128 -0.951 Pb 0.646 0.183 0.251 0.727 0.147 Mo 0.858 0.875 0.229 -0.055 -0.195 V 0.700 0.351 0.715 0.244 -0.076 Cr 0.819 -0.060 0.879 -0.200 0.045 Ti 0.840 -1.103 0.845 -0.339 -0.029 P 0.556 0.540 -0.396 0.327 -0.027

Table 5.17: Rotated factor matrix for elements in Pacific pelagic clays. (Arithmetic Data). 151

Rotated Factor Matrix

Factor Numbers 1 2 3 Sums of Squares down columns 2.462 2.712 1.781 1.606 Variable Communality Name 4 Factors Mn 0.715 0.791 -0.057 -0.135 -0.261 Fe 0,765 0.252 0.025 -0.124 -0.828 Ni 0.851 0.422 44276 -0.705 -0.314 Co 0.678 0.231 0.312 -0.217 -0.693 Cu 0.833 -0.004 0.081 -0.895 -0.160 Pb 0.717 0.472 0.673 0.076 -0.189 Mo 0.738 0.644 0.123 -0.555 0.027 V 0.808 0.082 0.861 -0.243 0.032 Cr 0.868 -0.509 0.769 -0.132 0.022 Ti 0.867 -0.118 0.850 -0.082 -0.35'. P 0.721 0.790 -0.063 -0.078 -0.294

Table 5.18: Rotated factor matrix for elements in Pacific pelagic clays. (Log Data). 152

Rotated Factor Matrix

Factor Number _L 2 Sums of sauares down columns 4.257 3.893 Variable Communality Name 2 Factors Mn 0.739 0.222 -0.830 Fe 0.795 0:823 -0.344 Ni 0.823 0.441 -0.793 Co C..841 0.380 -0.835 Cu 0.740 0.653 -0.560 Pb 0.728 0.663 -0.537 Mo 0.347 0.354 -0.471 V 0.602 0.758 -0.163 Cr 0.848 0.920 -0.040 Ti 0.868 0.881 -0.304 P 0.818 -0.050 -0.903

Table 5.19 Rotated factor matrix for elements in Pacific pelagic carbonates.(Log Data). 153

d) Conclusions The interpretation of correlation and factor analysis of manganese nodule and pelagic sediment data presents a number of problems. It would appear that data of this nature do not readily lend themselves to this type of analysis. Two possible reasons for this are firstly, the differing distribution of the major and the minor elements and their deviation from normality or log-normality mentioned previously, and secondly, the wide differences between the means of the variables. Possibly the arithmetic data correlation and factor matrices give a better pl ';ure of the relationships between the various elements than do the log data matrices. By transforming the data to logs and thereby changing their distribution some element associations may be obscured.

In spite of these difficulties certain features of interest emerge from the data. In the nodules there is good evidence to suggest Ni,Mo and Cu are associated with manganese. There is also a.possible association between Fe, Ti, Co and Pb. However, it appears more likely that Co and Pb are associated more strongly with each other than with either of the other two. Further, the evidence suggests that Cr is associated with the detrital phases of the nodules. Certainly, as the percentage of detrital constituents increases so does the Cr content (see also sections 5.5 and 5,10). Why this relationship is not shown on the log factor matrix is not clear but could be related to the very large skew shown by the log detrital value (table 5.1), 154

In the clays there is good evidence to suggest that Cr, V and Ti are associated with each other. Further, Ni and Mo appear to associate with Mn. The relationships between the other elements are not very clear. 155

SECTION 5.5

DISCUSSION OF ELEMENT ASSOCIATIONS AND ABUNDANCES

In this section certain features concerning the geochemistry of the elements determined in this work will be discussed in the light of the data presented in the foregoing section. For more general coverage of the marine geochemistry of these elements the reader is referred to the following articles:- Chester(1965), Arrhenius (1963), Goldberg and Arrhenius (1958), El Wakeel and Riley (1961). i) Manganese and Iron These elements show a fundamentally dissimilar behaviour in both nodules and sediments. In nodules they form separate mineral phases, although it appears that, some iron can enter the manganese minerals (Chapter 4), and exhibit a strong negative correlation. Both have a strong negative skew on a log scale and are narrowly dispersed. 156

Neither exhibit a normal distribution but iron tends to approach this more than manganese. The greater enrichment of Mn than of Fe in both nodules and sediments over their concentrations in igneous rocks is probably a reflection of its greater mobility in the secondary environment. Goldberg and Arrhenius (1958) have shown that while manganese is present largely in authigenic phases on the sea floor, iron is present to a larger extent in partially weathered detrital minerals derived from the continents. This observation applies more to sediments, where, according to Chester and Hughes (1966) more than 90 percent of the iron present occurs in clays and other non-authigenic phases, than to the nodules where the bulk of the iron is present in hydrated authigenic minerals. ii) Nickel and Copper Both these elements exhibit a similar behaviour in manganese nodules, but do so to a much lesser extent in pelagic sediments. In the nodules each is strongly correlated with the other, and both are strongly correlated with manganese. Further, both are heavily loaded on the manganese factor in both factor matrices. These observations confirm the suggestion of Arrhenius (1963) that both Ni and Cu are largely constituents of the manganese phases in nodules.

Both elements are similarly enriched in todorokite rich nodules over their concentrations in birnessite rich forms, and are positively correlated with depth. 157

Their association with todorokite probably results from the replacement of divalent manganese (ionic radius 0.80) by divalent Ni and Cu (ionic radii 0.69 and 0.72 respectively). This association with todorokite could partially be the cause of their relationship to depth, the abundance of todorokite itself being depth dependent (Chapter 4).

The association between these elements is not as close in the sediments as in the nodules. While Ni is strongly correlated with Mn and groups with manganese in the fact- or analysis, the association between Mn and Cu using both techniques is weaker. Goldberg and Arrhenius (1958) have shown that a high proportion of Ni in pelagic. sediments is present in the form of micronodules. Further,Chester and Hughes(1966) have found that Ni is partitioned between the micronodule and clay fraction of the sediment in roughly equal proportions. By contrast, Goldberg and Arrhenius (1958) have found only a small proportion of the Cu in the sediment to be present in the micronodules, much of this element being present in organic phases and basaltic pyroclasts. In the context of this latter observation it is significant that on factor one of the arithmetic factor matrix for.nodules,Cu and the detrital constituents are associated. iii) Cobalt and Lead Cobalt and lead are strongly associated in manganese nodules, and are negatively correlated with Ni, Cu and Mn. They are positively correlated with each other and are loaded on the same factor in the factor analysis. 158

According to Arrhenius(1963) both elements are largely present in the iron phases of the nodules. This association does not appear. to be strongly developed on the basis of the present data, nor are they strongly enriched in the iron phases of the nodules examined by electron microprobe techniaues (Chapter 3). There is evidence for a weak association of these elements with iron, both from their correlation coefficients with Fe and from the electron microprobe investigation (Chapter 3). However, their enrichment in nodules cannot be related to an enrichment of iron in these nodules,the maximum concentrations of these elements occurring in different samples (section 5.10).

Both elements are enriched in nodules containing birnessite,relative to their concentrations in the todorokite rich forms. However, as they are not associated with manganese this association is probably fortuitous. It could result from their relationship to depth, both elements and birnessite, being enriched in shallow water oceanic nodules relative to their concentrations in deeper areas.

The abundance of Co in nodules from shallow depths, especially those on basaltic seamounts, could perhaps result from its possible variable oxidation state in sea water. According to Garrels (1960) and others, under moderately oxidising conditions Co2+ is the stable form of this element in sea water. However, Burns (1965) has shown from thermodynamic calculations that where the Co content of sea water exceeds 1.3 x 10-8M, under highly oxidising conditions Co2+ can be oxidised to Co3+ and will possibly form insoluble CoOOH. 159

Thus the relationship of Co to depth can probably be explained by the gent increase in the degree of oxygen- ation of sea water(and possibly of the sediment also, section 5.14) as the sea,surface is approached, (Richards 1965). However,this is unlikely to be the only factor for according to Burns (1965) the average Co content of sea water is less than 1.3 x 10 8M and therefore the transformation of Co2+ to Co3+ would be unlikely to occur. In this context the association of Co rich nodules with basaltic seamounts is significant (section 5.10). According to Carr and Turekian (1961),submarine basalts contain on average between 30 and 80 ppm. Co. By contrast, the Co content of average igneous rocks is only 20 ppm. (Ahrens and Taylor 1961). Thus in areas where submarine basalts are undergoing weathering a supply of Co, to sea wr-ter is available. According to Burns (1965),this local supply of cobalt to sea water coupled with the oxidising conditions associated with the tops of seamounts, could result in the formation and precipitation of trivalent cobalt. In this manner both the associations between Co and depth, and the enrichment of Co in nodules found on seamounts, could be explained.

A similar explanation possibly also applies to the associations between lead in nodules and depth. Goldberg (1965) has suggested that Pb2+ could be oxidised to Pb4+ and precipitated under highly oxidising conditions. ,according to Garrels (1960),under laboratory conditions at 1 atmosphere and 25°C, with both dissolved carbonate and sulphur species in the system, this transformation takes place at an Eh of about.7•volts. 160

Possibly conditions sufficiently oxidising to form trivalent cobalt also form quadrivalent lead, thus causing the enrichment of both elements in the same nodules. The strong association between these elements in nodules would suggest that similar factors are influencing the concentration of each.

Cobalt and lead in sediments exhibit features similar to their behaviour in the nodules. According to Goldberg and Arrhenius (1958) and El Wakeel and Riley (1961),a significant proportion of each is located in the micronodules, the remainder being largely present in the clay fraction of the sediment. The loading of a portion of both elements with manganese in both factor matrices would tend to agree with these suggestions, so also would the correlation between Mn and Co in the correlation matrices. iv) Vanadium, Chromium and Titanium The associations between the different, members of this triad are stronger in pelagic sediments than in manganese nodules. In the sediments both correlation and factor matrices attest to this association. None of these elements are significantly enriched in pelagic clays over their concentraions in igneous rocks (table 5.9) nor according to Goldberg and Arrhenius (1958) are they concentrated in the authigenic phases of the sediment. On the basis of these observations and the similarity between this association and that found between these elements in igneous rocks, Landergren (1964) has suggested they are primarily present in the detrital phases of the sediments. 161

By this it is suggested that they enter the basin either in unweathered terrigenous material or in the products of submarine vulcanism.

Consideration of the oxidation behaviour of Cr and V in.the marine environment would support these suggestions. According to Landergren (1964), on weathering, both elements would pass into solution as soluble complex anions, chromates and vanadates respectively. Thus it is to be expected that on the breakdown of primary phases these elements would be lost from the deposit. That Ti does not behave in this manner is evinced by its slight enrichment in pelagic clays over its concentration in near—shore clays and igneous rocks. Possibly Ti is,in part,associating with Fe in these deposits.

In manganese nodules greater differences between the behaviour of these elements are observed. Both V and Ti are slightly enriched in nodules over their concentrations in igneous rocks, while Cr is actually depleted in these bodies. This depletion of Cr in manganese nodules is in accordance with its expected oxidation behaviour in the marine environment. Further, the strong association between Cr and the detrital constituents of the nodules (if the log data factor matrix is ignored) attests to the presence of this element in the detrital phases of these bodies. This is in contradiction to the suggestion of Arrhenius (1963) that Cr is present in the Fe phases of manganese nodules. No association between Cr and Fe has been found in this work. 162

On the basis of th,,, factor and correlation matrices, there is evidence to suggest that V and Ti are associated with Fe in nodules. This is in accord with the observation of Arrhenius (1963) that Ti is present in the iron phases of these bodies, V not being determined by this author. The slight enrichment of V in nodules over its concentration in igneous rocks is perhaps somewhat surprising in view of its suggested oxidation behaviour in the marine environment (Landergren 1964). Obviously this element does not entirely remain in solution, some being removed, possibly by adsorption onto colloidal ferric hydroxide (Krauskopf 1956), into the iron phases of manganese nodules. v) Molybdenum and Barium From section 5.4 there is good evidence to suggest that Mo is strongly associated with =In in both nodules and sediments. For the sediments this is in agreement with the work of Goldberg and Arrhtaius (1958), these authors reporting the presence of significant concentrations of. Mo in micronodules. However, in the case of the nodules,Arrhenius (1963) has suggested that Mo is present in the iron phases.

Quite how Mo could be present in micronodules in significant concentrations and yet enter the iron phases of macronodules is not clear. It cannot be associating to any significant extent with Fe in the former, for Chester and Hughes (1966) have shown that little iron is present in these bodies. Further, in the sediments investigated in this work, the correlation between Mn and Mo is much stronger than that between Fe and Mo. 163

In view of the lack of an association between Fe and Mo in the nodules investigated in this work, and the presence of a strong association between Mn and Mo (see also section 5.10),it is concluded that Mo is present in the manganese and not the iron phases of nodules. whether it is present in the lattices of these minerals or adsorbed onto their surfaces is not known.

According to Wedephol (1960) Mo is enriched in reIagic clays, especially those :'rom the Pacific Ocean, relative to its concentration in near-shore clays and igneous rocks. Inspection of table 5.9 reveals that this enrichment does not appear to occur in the present samples. However, this observation is based on the log mean of Mo in clays. The arithemetic mean is 20 ppm., falling between the 3 ppm. of Kuroda and Sandell (1954) and the 27 and 45 ppm. of 'edephol (1960) and Goldberg and Arrhenius (1958) respectively. In view of the wide differences between these averages little can be said at the present time concerning the enrichment behaviour of Mo in pelagic sediments.

According to Arrhenius (1963) Ba in nodules can be present in the manganese phases and also in the form of barytes. and celestobaryte. From the data presented in section 5.4 there is some. evidence for an association between Mn and Ba. However, the relationship of Ba to depth cannot result from its association with Mn, the concentration of this latter element not being depth dependent. It could possibly be related to a volcanic source of Ba in the vicinity of volcanic seamounts (see also section 5.10). 164 vi) Summary and Conclusions 1) The dispersion of elements in nodules and sediments is variable and their distribution approaches log-normality in the case of the minor elements and normality in the case of the majors. 2) The abundances of elements in nodules and sediments examined in this work are similar in most cases to those examined by previous workers. Sediments found adjacent to nodules show no general compositional differences from those not associated with nodules. 3) The elements Mn, Ni, Co, Cu and Pb are enriched in both nodules and pelagic clays over their concentrations in near-shore clays and igneous rocks. Cr is depleted in nodules while the concentrations of Fe, Ti and V are higher in nodules but much the same in the other three rock types. 4) Nodules containing todorokite are compositionally different from those rich in birnessite. Ni and Cu are enriched in the former and Co, Pb and Ti in the latter. This could result from compositional differences between these minerals or from other factors such as depth. 5) Compositional variations in manganese nodules are related to depth. Co and Pb are abundant in shallow water oceanic forms and Ni and Cu in those from deeper areas. This could, in the case of Co and Pb, be the result of oxidation of these elements to insoluble forms under the oxidising conditions found near the top of seamounts and other shallow water oceanic areas. 165

6) Correlation and Factor Analysis reveal that in nodules, Ni, Mo and Cu associate with Mn, Ti with Fe, Co with Pb,and Cr with the detrital constituents. In pelagic clays,elements in the triad V-Cr-Ti are associated with each other, Ni and Mb follow Mn, while the associations of the other elements are indistinct. These associations can be explained by the variable partition of elements between the different phases of nodules and sediments. 166

SECTION 5.6

COMPOSITIONAL VARIATIONS 71ITHIN SINGLE NODULES

Compositional variations within single nodules have been investigated by comparing analyses in two nodules of sections taken at varying distances from the cores. Both these specimens were large nodules taken from stations 5133 and 5138 on the Carlsberg Ridge (Chapter 2 and section 5.13).

The sample from station 5138 was approximately 10cm. in diameter one half of this being occupied by a manganese impregnated volcanic core. By contrast, the sample from station 5133 was about 7 cm. in diameter and contained three small discrete cores each surrounded by concentric- ally banded layers of manganese iron oxides. This latter sample is probably a composite of three smaller nodules that,have coalesced. The analyses are presented in tables 5.20, and 5.21. 167 i) Nodule 5133.1 In this nodule two series of samples were taken from two of the three cores present to the surface (Fig.5.15 and table 5.20). Except in the case of Ni and Ba in the first series and Mo in the second, there is little change in the composition of this nodule from its centre to the surface. In view of the presence of three small nodules within this composite body, comparison of sections taken at the same distance from separate cores are probably of little significance in terms of compositional variations within a single nodule. However, the outer layers of the three inner nodules are common, and with some exceptions are fairly similar in composition at the two places sampled. ii) Nodule 5138.17 Three sets of samples were examined in this nodule. One sample was taken from the outer 2 mm., four samples from 2 to 6 mm. from the surface and four samples from adjacent to the core.

Comparison of the composition of samples within each individual set revealed, with few exceptions, few significant variations (Fig. 5.16). In the 2 to 6 mm. section only Pb and Si vary markedly, the sample containing the greatest Si content being that with the lowest Fe and Mn contents. In the four samples from adjacent to the core twoltfourfold variations in the Ni and Ba contents occur While the Si content remains fairly constant. First Series Second Series a b c a b c d Adjacent 5 mm.out Outer 3 mm. Core 5mm. out 5 to 10mm. 10 to 15 to from from core from core mm.from Core previous core core section nn 15.49 16.74 16.67 14.46 15.52 15.09 15.12 Fe 17.50 15.77 15.76 13.87 15.89 18.09 15,76 Si 9.8 6.3 7.7 14.5 11.4 10.1 10.3 mi. 0.186 0.500 0.633 0.363 0.268 0.268 0.444 Co 0.161 0.209 0.218 0.163 0.163 0.228 0.186 Cu 0.111 0.118 0.154 0.148 0.132 0.133 0.136 b 0.033 0.022 0.030 0.015 0.017 0.016 0.015 Ba C.077 0.115 0.147 0.207 0.195 0.146 0.139 Lb (.030 0.043 0.045 0.020 0.018 0.039 0.064 Cr (.000? 0.0005 0.0007 0.0014 0.0012 0.0011 0.0009 Ti 0.896 0.495 0.633 0.707 0.682 0.844 0.716 L.O.D. 16.31 17.28 23.58 12.87 14.55 14.13 14.45 1.:0.1. 14.28 15.64 23.61 14.86 15.08 16.69 16.21 Table 5.20: Compositional variations within nodule 5133.1 (in weight percent). 169

2nd Series 1st Series

Fe Fe .•11, ,Mo .110••• mom ma • m. ea. ow • Mn Mn • Si 10 Si

Mo x 100 5 x100 Mo t) cen r e

(p Manganese Pb x 100 tion impregnated /, cores tra Ba x 10 en nc

Co Ba x 10

0.5 Ni

4 ,-- -* C9.-----. . Co • .Cu • 0.1 15 10 5 0 0 5 10 Cm from core

Fig. 5.15 Plot of variation of selected elements across nodule 5133.1. 170

Outer 2 to 6 mm. from the surface 2 mm. a b c d Mn 16.64 12.52 14.52 15.20 15.31 Fe 17.60 14.35 17.90 18.23 18.21 Si 6.7 12.4 7.2 5.5 7.3 Ni 0.392 9.330 0.380 0.394 0.368 Co 0.322 0.267 0.282 0.271 0.241 Cu 0.133 0.182 0.133 0.153 0.138 Pb 0.056 0.025 0.024 0.064 0.085 Ba 9.171 0.211 0.165 0.198 0.200 Mo 0.036 0.030 0.035 0.037 0.031 Cr 0.0004 0.0013 0.0011 0.0014 0.0010 Ti 0.736 0.759 0.7'9 0,894 0.659 L.O.D. 18.29 17.34 16.53 17.41 17.05 L.O.I. 15.82 14.86 15.52 14.75 14.53 Adjacent to the core. a b c d Mn 9.87 11.64 11.19 11.69 Fe 13.58 13.28 15.91 16.60 Si 20.1 18.4 16.1 20.5 Ni 0.169 0.114 0.335 0.126 Co 0.189 0.160 0.176 0.132 Cu 0.144 0.177 0.160 0.186 Pb 0.028 0.034 0.043 0.036 Ba 0.105 0.145 0.068 0.182 Mo 0.034 0.036 0.052 0.031 Cr 0.0020 0.0020 0.0024 0.0017 Ti . 0.564 0.570 0.599 0.685 L.O.D. 14.61 14.01 10.89 13.94 L.O.I. 13.07 13.72 10.27 13.45 Table 5.21(a): Compositional variations within nodule 5138.17.(in weight percent). 171

1 2 3 Mn 11.09 14.38 16.64 Fe 14.84 17.17 17.60 Si 18.7 8.1 6.7 Ni 0.186 0.368 0.392 Co 0.164 0.265 0.322 Cu 0.166 0.151 0.133 Pb 0.035 0.049 0.056 Ba 0.125 0.193 0.171 Mc 0.038 0.033 0.036 Cr 0.002 0.0012 0.0004 Ti 0.600 0.757 0.736 *L.O.D. 13.36 17.08 18.29 L.O.I. 12.62 14.91 15.82

Table 5.21b:Comparison of samples at different distances from the core of the nodule 5138.17 ( in weight percent). 1) Average of 4 samples adjacent to the core 2)Average of 4 samples 2 to 6 mm. in from the surface. 3)One sample from the outer 2 mm. L.O.D. = loss on drying at 100°C for 2 hours. Fig. 5.16 Illustrating the variation in element content of the manganese crust from the surface (a) and adjacent to the core (b) of nodule 5138.1?. 173

Between the three sets of samples much more general compositional differences occur than within a single set (table 5.21 a and b). At the 95 percent confidence level (Student's t test), Ni, Ba, Mn and Co are all significantly higher in the 2 to 6 mm. set than in samples from adjacent to the core, while Si and Cr are lower.

In the single sample from the surface of this nodule the Ni, Mn and Co contents appear to be somewhat greater, and the Si and Cr contents less, than their mean concentrations in the samples at 2 toCuth.from the surface. However, only in the case of Co and Cr are these differences statistically significant. Thus within this nodule there is an increase in Si and Cr and a decrease in Mn, Ni, Co and Ba as the core is approached. iii) Conclusions The differences betwoHlthe compositional variations found within these two nodules can largely be related to the greater amount of detrital materials in the latter ; than in the former (Chapter 2). Elements that are concentrated in the detrital phases of the nodules from station 5138 increase in concentration as the percentage of detrital phases increases, while the reverse is found for elements not concentrated in the detrital phases.

These compositional variations are different from those found during the electron microprobe study (Chapter 3). In the latter, very local compositional variations were being investigated. 174

It would appear that while compositional variations on a microscopic scale occur in nodules, there can also be a change in the bulk composition of the nodule from its core to the surface. 175

SECTION 5.7

COMPOSITIONAL VARIATIONS BET. TEEN NODULES FROM THE SAME SITE i) Morphologically similar nodules Comparison of analyses of five nodules from a single site (station 5138 Carlsberg Ridge) revealed differences of up to threefold in certain element concentrations (Fig. 5.17). However, these variations are only slightly greater than those observed in the eight samples from the single. nodule from this same site (table 5.21 and Fig.5.16). Indeed, except in the case of Cu and Mo, the spread of results is greater within the single nodule. Analyses of morphologically similar nodules from Challenger station 297 and from station Proa. 113 (Appendix 2) also reveal few compositional variations within each site.

These results suggest that morphologically similar nodules from a single site are of similar composition. This is in agreement with the work of Lorber (1966) who has shown that at two dredge sites within the Pacific Ocean most nodules at each site are of similar composition.

176

Mean Range I

6 ;•?- 0-5

0.1

0.05

Mn Fe Si Ni Cu Mo Co Cr x100 Ti Bo Pb 0.01

Fig. 5.17 Illustrating the variation in element content between nodules from site 5138. 177

In addition, Skornyakova et al (1962) have found at a number of sites in the Pacific that compositional differences between nodules from within each site are small. ii) Morphologically dissimilar nodules :here there are different sizes of nodules at a single site, greater compositional differences are observed. For example, at station 5133 on the Carlsberg Ridge, two size populations of nodules were found. One population consists of large nodules about 7 cm. in diameter, while the other population consists of small nodules, about 0.5 cm. in diameter.

These two populations are.distinct populations compositionally (Fig. 5.18). In particular,Ni, Mn and g*, CLA are present in significantly higher concentrations and Fe and Ti in significantly lower concentrations in the small nodules, than in the crust of the one large nodule examined from this site (Fig. 5.15).

At another site on the Carlsberg Ridge, station 5136, a population of manganese crusts and a population of small 0.5 cm. diameter nodules occur. Comparison of the composition of a sample of crust with that of the small nodules reveals less marked differences than were found at station 5133. The Ni content of the small nodules is higher and the Si and Fe contents lower than that of the crust. How- ever, in the few samples studied these differences are not statistically significant and it cannot be stated with confidence that the two sets of samples are different compositional populations (Appendix 2). 178

50-

140 .1(0

T 10- 1

01;

T 0-05 -

[ Mn Fe Si Nu Cu Mo Co Cr i100 Ti PI 0 01

Fig. 5.16 Comparison of composition of small (a) and large (b) nodules from station 5133. 179 iii)Discussion These observations are of considerable importance in the context of the regional geochemistry to be discussed subsequently. For regional variations in nodule composition to be.based on the analysis of a single nodule from each site, each nodule must be compositionally representative of the bulk of the nodules at the site where it occurs.

',here all nodules from a single site belong to the same morphological population, there is good evidence to, suggest that this condition is fulfilled. This, however, does not necessarily apply when morphologically dissimilar populations occur at the same site.

In general, occurrences of the latter are rare. To quote Murray and Renard (1891) " As a rule the nodules at any station have a family resemblance and differ in size, form and internal structure, from those at another station." No distinct separate populations of nodules at a single site were recorded by these authors although they investigated over three hundred dredge stations. The possible causes of the anomalous nature of the Carlsberg Ridge nodules will be dicussed in section 5.12. 180

SECTION 5.8

COMPOSITIONAL 0 VARIATIONS BETWEEN NODULES AT DIFFERENT DEPTHS IN SINGLE SEDIMENT CORES A number of the cores examined in this study contained nodules at several horizons (Chapter 1). In some cases these nodules approached closely to the same composition, i.e, the concentrations of most of the elements fell within twice the standard deviation from their means. For example, in nodules from cores Amp. 80G, Proa 108P, and Wah. 24.FF No. 8, only Pb, Ba and Cr in the first of these, Cr in the second and Co, Mo and Ti in the third, fell outside the ninety-five percent confidence limits.. Greater compositional differences were observed between nodules from cores TVa.h.2P and Proa 105G. In the former only Cu, Mo and Cr, and in the latter Co, Ba, Ti and V, fell within the ninety-five percent confidence limits (Appendix 2).

TJThile compositional variations between nodules in some cores are greater than can be accounted for by analytical error, inspection of Appendix 2 shows that rarely 181 are these variations greater than three-fold, and are often less than two-fold. Thus the variation is commonly little greater than that observed between surface nodules from a single site and is never so large that the composition of buried nodules becomes atypical of nodules as a whole from the region in which they are found.

An explanation of the compositional similarity between surface and buried nodules at the same site, poses some problems. If the nodules were formed at the sediment surface and subsequently btried, it is to be presumed that they are of the same age, or older, than their surrounding sediment. In this case the age difference between some buried nodules and their surface counterparts extends over a time interval at least equivalent to the Quater- nary period.

In view of the probable changes in oceanic circulation and bottom environmental conditions during the recent ice ages (Hurley et al 1963) it is difficult to accept that nodules forming at the sediment surface would have remained of similar composition throughout this period. Thus alternative explanations to account for the compositional similarities between buried and surface nodules must be considered.

If, as has been suggested in Chapter 1, some of the buried nodules form within the sediment, the compositional similarities between buried nodules and their surface counterparts could possibly be accounted for. 182

They could all be forming at, or about, the same time from sources of elements within or beneath the sediment. It is possibly significant in this context that most of the buried nodules examined in this work were found in areas far from land and thus where local volcanic sources of elements are possibly more important than continental sources (section 5.11). 183

SECTION 5.9

COMPOSITIONAL VARIATIONS BETWEEN NODULES FROM_ ADJACENT SITES

In a number of areas nodules were collected from closely related sites. These include the OarlsbeigRidge, the Kingt Trough area in the North Atlantic Ocean, and the continental borderland off Baja California.

In the case of the Carlsberg Ridge samples, considerable compositional and mineralogical variations were found between nodules only a few miles apart (see section 5.13). Only minor differences were observed between the two sets of large nodules from stations5133 and 5138 (Fig. 5.15 and 5.17). By contrast, significant differences occur between the two sets of small nodules from stations 5133 and 5136. The Ni and Cu contents of those from station 5133 are considerably higher than those from station 5136 (approximate ratios 5:1 and 7:1 respectively). The Fe, Ti and Co contents of the 5133 nodules are, however, markedly lower (approximate ratios 4:7, 1:5 and 2:9 respectively). In addition, the Mn and Si contents are also significantly higher in the 5133 nodules (Fig. 5.19). 184

Moe i Reis

I a

0'I

0-05 I

Mn Fe Si Ni Cu Mo Co Cr 100 Ti B. Pb 0-01

Fig. 5.19 Comparison of composition of small nodules from station 5133 (a) and station 5136 (b). 185

Examination of the mineralogical composition of these nodules also revealed interesting differences. All samples, with one exception, consisted of birnessite (Svin02 of Buser and Grutter 1956) or were too poorly crystalline for their mineralogy to be determined. The exception was the group of small n8dulesoat station 5133. These had Id, spacings of 9.7A, 4.8A, 2.44a and o• 1.42A,confirming the presence of todorokite.

Encrustations from two stations in the Kings Trough area in the North Atlantic also show considerable compositional differences. These samples were taken on the slopes of Palmer's Ridge in an area of rugged topography. The two sites were Discovery stations 5975, lat. 42°54.2'N, long. 20°12.8'W, depth 1752 to 1743 fathoms and 5978, lat. 42°54.6'N, long.20°11.2'W, depth 2103 to 1694 fathoms. Analyses ofasample from each site are presented in table 5.22. Mn Fe Ni Co Cu Ba St.5975 23.1 8.2 0.77 0.21 0.41 0.24 St.5978 16.7 18.0 0.36 0.89 0.12 0.12 Mo V Cr Ti St.5975 0.036 .0.01 0.03 0.45 St.5978 0.058 '..006 0.03 0.15

Table 5.22: Analyses of two manganese crusts from the North Atlantic Ocean (weight percent dry weight). Analyses by courtesy of N.D. Birrell, Newport News Ship- building,and Drydock Co., Newport News, Virginia, U.S.A. 186

Inspection of table 5.22 reveals that the enrichment behaviour of the elements in these samples is showing features found in nodules in general (section 5.5). Mn, Ni and Cu are enriched in the first sample relative to the second while the converse applies to Fe, Co and V.

The variation in the concentration of certain elements, particularly Ni, Co and Cu, between nodules within these two,topographically rugged areas, is of sufficient magnitude, if typical of other areas of similar size, to negate many of the conclusions drawn in the past concerning,the regional geochemistry of manganese nodules. However, analyses of nodules from a number of closely related sites, where there is not a rugged topography, show considerable similarities.

Nodules from a deep basin off Magdalena Bay, Baja California, all approximate closely to the same composition (Appendix 2). In addition, Mero (1965) has shown that along a 320 km. traverse in the East Pacific, nodules from ten dredge sites are closely related in composition. The only significant variations he found were a two-fold decrease in the Fe content and a slight increase in the Mn content as the American continent was approached.

It appears, from this limited data, that nodules from areas of rugged topography can show strong compositional variations over short distances, while these have not to date been found between nodules taken in areas of less rugged relief. Discussion of the possible causes of these differences will be postponed until after presentation of the regional geochemistry. 187

SECTION 5.10

INTER-OCEAN VARIATIONS IN THE COMPOSITION OF NODULES AND SEDIMENTS

Inter-ocean variations in the composition of both nodules and sediments have been investigated by a number of workers. In the case of manganese nodules, Willis and Ahrens (1962) have shown that compositional differences occur between.samples from the Pacific and Atlantic Oceans. These workers, analysing both their own data and those of Mero (1960), found that Mn, Co and Cu are lower in nodules from the Atlantic than in those from the Pacific, while Fe is higher. Mo and Ti were also found to be lower in Atlantic nodules than in those from the Pacific.

In the past, lack of data on the composition of Indian Ocean nodules has prevented their comparison with samples from other oceans. Comparison of the average composition of Pacific nodules with the average composition of Indian Ocean nodules, determined during the course of this work, reveals considerable similarities (table 5.23). 160

Max. Min. Av. Mn 30.28 5.4 16.53 Fe 26.32 4.36 11.96 Ni 1.98 0.184 0.605 Co 2.57 0.048 0.319 Cu 1.64 0.028 0.307 Pb 0.514 0.005 0.041 Ba 1.58 0.018 0.191 Mo 0.077 0.0087 0.035 V 0.093 0.010 0.042 Cr 0.012 0.0002 0.001 Ti 2.65 0.123 0.685 a) Pacific Ocean 91 samples.

Max. Min. Av. Mn 20.19 9.4 14.77 Fe 22.48 4.5, 13.31 Ni 1.35 0.136 0.418 Co 0.822 0.045 0.229 Cu 1.055 0.028 0.183 Pb 0.255 0.0046 0.046 Ba 0.399 0.060 0.154 Mo 0.056 0.012 0.030 V 0.084 0.017 0.046 Cr 0,011 0,0003 0,0012 Ti 1.404 0.232 0.651 b) Indian Ocean 27 samples. Table 5.23: Abundances of elements in surface manganese nodules from the Pacific and Indian Oceans. (in weight percent). 189

The elements Mn, Ni, Co and Cu are slightly more abundant in Pacific than in Indian Ocean nodules, while in the case of the other elements determined no significant differences occur.

Comparison of the compositional range of Pacific nodules with that of those from the Indian Ocean, reveals greater differences (table 5.23). Most elements show greater variation in their concentration in Pacific, than in Indian Ocean nodules. This is probably largely the result of more samples being collected from the former ocean than from the latter.

Inter-ocean variationsin the composition of pelagic sediments have been investigated by Wedephol (1960). This author reports that Mn, Ni, Cu, Pb, Co and Mo are enriched in Pacific pelagic clays relative to their concentrations , in those from the Atlantic. As in the case of the nodules, insufficient data has been available in the past on the composition of Indian Ocean sediments for them to be compared with those from other oceans.

Comparison of the average composition of Indian Ocean sediments examined in this study with that of samples from the Pacific reveals, as in the case of the nodules, considerable similarities (table 5.24). Again,the differences that do occur can largely be related to the greater numbers of samples taken in the Pacific Ocean. The greatest difference, that between the Ni averages, largely results from one sample of anomalously high Ni content being included in ' the Indian Ocean average. 190

.1 .2 3 4 5 6 Mn 0.345 0.282 0.436 0.428 0.234 0.202 Fe 2.90 3.17 3.97 4.41 2.36 2.78 Ni 0.014 0.015 0.018 0.040 0.010 0.0086 Co 0.0083 0.0061 0.010 0.0075 0.0065 0.0054 Cu 0.019 0.015 0.021 0.023 0,013 0.013 Pb 0.0018 0.0023 0.0031 0.0031 0.0017 0.0017 No 0.0006 0.0005 0.0007 0.0014 0.0002 0.0002 V 0.0069 0.007 0.011 0.0096 0.0054 0.005 Cr 0.0023 0.0033 0.005 0.004 0.0018 0.0034 Ti 0.148 0.235 0.303 0.288 0.101 0.233 P 0.115 0.058 0.100 0.084 0.071 0.047

Table 5.24: Average compositions of pelagic sediments from the Pacific and Indian Oceans. 1) Pacific Ocean sediments (169 samples) 2) Indian Ocean sediments (19 samples) 3) Pacific Ocean,surface clays (26 samples) 4) Indian Ocean, surface clays (7 samples) 5) Pacific Ocean, surface carbonates (24 samples) 6) Indian Ocean, surface carbonates (7 samples) 191

''Iedephol (1960) has suggested that the high concentration of certain elements in Pacific sediments compared with their concentration in those from the Atlantic, results from detrital sedimentation rates being higher in the latter Thus the compositional similarities between Pacific and Indian Ocean sediments could imply that the overall sedimentation rates in these oceans are similar. At least, it suggests that the rate of sedimentation in the Indian Ocean is more similar to that found in the Pacific than in the Atlantic Ocean. The less enclosed nature of the Pacific and Indian Oceans, compared with the Atlantic would accord with this suggestion. The similarity between the composition of the nodules from both oceans also suggests that they might.be forming under similar conditions (see also section 5.12), 192

SECTION 5.11

REGIONAL GEOCHEMISTRY

The regional geochemistry of both nodules and sediments from the Pacific and Indian Oceans has been investigated. The results are expressed in the form of diagrams and tables.

In view of the low concentration of most elements in nodules in the detrital phases of these deposits, all element values, excluding Cr, have been recalculated on a detrital free basis. This has been accomplished by sub- tracting the weight percentage of the hydrochloric acid insoluble fraction from the total nodule, and recalculat- ing the analyses accordingly.

Sediment values are discuised on a recalculated carbonate free basis. 193

COMPOSITIONAL VARIATIONS WITHIN THE PACIFIC OCEAN i) Topography of the Pacific Basin The main topographic features of the Pacific Ocean are shown in Fig. 5,20. The ocean can roughly be divided into an eastern portion of relatively low relief and a westeril portion of sharp topographic contrasts.

The North-East Pacific is dominated by a large deep basin extending as far west as the Hawaiian Islands. West of this area the topography becomes more rugged being dominated by east-west ranges of submarine mountains associated with the Marcus-Necker Rise.

The South-East Pacific is dominated by the East Pacific Rise which reaches its maximum elevation at long. 110°W. West of this, in the northern portion of the South Pacific,is the Tuamotu Archipelago separating the East Pacific Rise from the Central South Pacific Basin, This basin extends as far south as the Pacific-Antarctic Ridge. West of the central basin are ridges and troughs of a volcanic nature similar to those found in the North- -gest Pacific, However, unlike these, they are orientated in a north-south direction.

In conjunction with the following descriptions the reader is referred to the map "Bathymetry of the Pacific Basin" prepared by the North American Aviation Company, and Menard (1964)n 1 195

ii) Manganese Nodules Most of the elements in Pacific manganese nodules show some variation in their abundance throughout the basin. Manganese is highest in nodules from adjacent to the American continent, about 35 percent, and falls off sharply at first, and then gradually, towards the central areas of the basin (Fig. 5.21). In general, the average manganese content of nodules from the East Pacific is higher than is found in those from the south and west. In these latter areas,low manganese values are recorded in nodules and encrustations from areas of submarine volcanic mountains. The lowest manganese content recorded, about 10 percent, occurs in nodules from the South-West Pacific (Fig. 5.21).

The regional variation in the iron content of Pacific nodules is the reverse of that found for manganese. The highest iron values, around 15 to 20 percent occur in nodules from the South-West Pacific and in the volcanic mountain areas of the western and southern Pacific, (Fig. 5.22). By contrast, lower iron values occur in the eastern Pacific, these usually ranging from 10-15 percent. The lowest values of all, less than 2 percent, occur in nodules from the continental borderland area.

Consideration of the Mn/Fe ratio in Pacific nodules illustrates the antipathetic relationship between these two elements. This ratio decreases from a value of about 15 in the continental borderland to 0.5 in the South-est Pacific.

0 FIG 5.22 0 Fe in Pacific Nodules -• It ., • > 25 p•reent • • '1 ® Z0 - ZS II eN A 0 0 1S - 20 II Il l o 1 0 - 1 3 III II o 3 - 1 0 3 0 < 5

i 0 0 & C o o 0

‘,\ 0 1 •• 0 —a --.4. s CEO c 0 • 0 % •

Alli se

Illis

0® \1111, 0 3 Ili . 0 0 .• • 8 111 Ir ,- 198

Samples from volcanic mountain areas tend to have a ratio slightly in excess of 1, irrespective of their position relative to the margin of the basin.

The regional distribution of nickel and copper in Pacific manganese nodules is, in general, similar to that of manganese (Figs. 5.23 and 5.24). High values, generally in excess of 1.5 percent Ni and 1.0 percent Cu, prevail over the East Pacific pelagic area but very low values are encountered in nodules from the continental borderland. Thus, although there is a general similarity between the regional distribution of Nit Cu and Mn the maxima of Ni and Cu are displaced towards the pelagic areas of the ocean relative to that of Mn.

In the Central, South and 'est Pacific the nickel and copper contents of the nodules are generally lower than in the East Pacific. The lowest concentrations of both elements are found in nodules and encrustations from volcanic areas, especially in samples taken from seamounts, while higher values are recorded in the intervening basins.

The regional variation in the cobalt and lead contents of Pacific nodules is somewhat similar to that of iron (Figs. 5.25 and 5.26). However, it can be seen from comparison of Figs. 5.25 and 5.26 with Fig. 5.22 that the maxima of these elements are displaced towards the volcanic areas of high relief relative to that of iron. The highest values of each occur in nodules and encrustations from the Mid-Pacific Mountains and the Tuamotu Archipelago.

- - - 201

Areas of low relief between the elevated areas in the western and southern Pacific contain nodules with lower concentrations of both elements.

In the East Pacific both the cobalt and the lead content of the nodules is lower than in the west and south. In this area averages of around 0.2 percent Co and 0.03 percent Pb occur. The lowest values of all , were found in nodules from the continental borderland, less than 0.1 percent Co and 0.01 percent Pb. Samples from the Southern Borderland Seamount Province tend to have concentrations of these elements more similar to those found in the volcanic areas of the western and southern Pacific than to those from the rest of the East Pacific.

The regional variations in the content of the remaining.minor elements in nodules tend to reflect, more or less, the regional variations of either iron or manganese (Figs. 5.27, 5.28, 5.29. and 5.30). However, in many cases these regional variations are small. Molybdenum is highest in the nodules from the continental borderland and tends to be generally higher in the East Pacific than in the south and west (Fig. 5.27). It appears to follow manganese rather closely. By contrast, vanadium is slightly enriched in nodules from the West and South Pacific relative to its concentration in those from the east, but attains high concentrations,between 0.06 and 0.10 percent, in the encrustations from the Southern Batz:rland Seamount. Province (Fig. 5.2$).

204

The regional variation in the titanium content of Pacific nodules is very similar to that of iron (Fig.5.29). This would be expected in view of the close association between these two elements (section 5.5). High values are found in the South and West Pacific, especially in volcanic mountain areas. By contrast, lower values are found in the East Pacific, averaging 0.2 to' 1.0 percent, but increasing slightly in the Southern Borderland Seamount Province.

Regional variation in the barium content of the Pacific nodules is neither large, nor regular. It appears not to associate strongly with either iron or manganese (Fig.5.30). There does appear to be a slight barium enrichment in manganese rich nodules from the North-East Tropical Pacific. However, it also attains high concentrations locally in nodules from seamounts and exhibits a moderately high average concentration in nodules from the volcanic areas of the Mid-Pacific Mountains and the Southern Borderland Seamount Province.

Chromium in manganese nodules is largely present in the detrital phases and therefore its distribution throughout the Pacific cannot be considered on a detrital free basis, In general, encrustations rich in silicate material, such as those from the Southern Borderland Seamount Province, are rich in chromium also. In addition, it is sometimes enriched in nodules enclosed in chromium rich sediment. These observations would accord with its suggested detrital origin.

1110 0 F IG 5.28 V in Pacific Nodules ....,

• • 070 - • 147 percent ® • 032 - • 070 ,, eaN

s .014 - • 032 ,, % IP 0 •007 - • 0 1 4 s ,

O O 0 @0 @ 'no # o r j 1 • # ®

0 0 • ®

11111k:d\ .0 ...N ® Ail 1 ap+' OOF -. .. , ao ® •

ill 1 Act

)11

tAgtil11 la

41 111N01h4 0 CC) 0 .

209 iii) Sediments There is less variation in the composition of Pacific pelagic sediments than is found in the case of the nodules. Apart from local high concentrations in the continental borderland, about 1.5 to 2.0 percent, manganese is highest in sediments from the South Pacific basin, far removed from land. Its concentration in these sediments is around 1.0 percent but often exceeds this value in the dark chocolate clays rich in micronodules, typical of this area (Fig. 5.31).

By contrast,, sediments from the marginal areas of the Pacific Basin, and from much of the North Tropical Pacific, are lower in manganese. In this latter area manganese values range from 0.3 to 0.6 percent (Fig. 5.31).

In contrast. to its behaviour in the nodules, iron in the sediments, with a few exceptions, tends to show a similar regional distribution to manganese (Fig. 5.32). Low concentrations occur in sediments from the continental borderland area in which manganese is enriched. The, highest concentrations occur in the South Pacific basin, also an area of high manganese content. In this latter area iron values between 5 and 10 percent occur but often increase to above 10 percent in the dark chocolate clays. By contrast, sediments from the marginal areas of the basin and from the North Tropical Pacific contain lower iron concentrations. Values range between 3 and 6 percent over most of this latter area (Fig. 5.32). FIG 5.31 Mn in Pacific S•d im•nts

• 1.47 - 3.21 psrc•nt • • 707 - 1.47 0 •321 - • 707 O •147 - •321 O •070 - •147

212

Most of the minor elements investigated vary little throughout the Pacific basin. Their average concentrations in clay sediments from different areas are summarised in table 5.25.

High concentrations of Ni were found in the two samples from the continental borderland, 850 ppm. and 400 ppm. respectively. By contrast,the Cu content of these samples is fairly low. Over most of the pelagic areas of.the Pacific both Ni and Cu average about 200 ppm., Cu, for the most part, being slightly in excess of Ni. Samples from the South-East Pacific contain slightly higher concentrations of both elements than do those from the central South Pacific Basin.

The cobalt and lead contents of sediments from the North Tropical Pacific vary between $0 and 160 ppm., and l5and 40 ppm. respectively. Lower values of both elements occur in sediments from the continental borderland. In the South Pacific, concentrations of 120 to 200 ppm. Co and 30 to 80 ppm. Pb occur in the south-east of the basin, while values of 80 to 160 ppm. Co and 20 to 50 ppm. Pb were found in the central area.

Titanium varies between 2 and 5 thousand ppm. in the North Tropical Pacific, including the continental borderland. In the South-East Pacific, values are a little lower but increase in a westerly direction. 213

1 2 3 4 5 6 Mn 0.43 0.53 0.97 0.30 0.38 1.8 Fe 4.41 4.37 9.47 3.06 3.88 3.5 Ni 0.040 0.030 0.017 0.020 0.020 0.062 Co 0.0075 0.015 0.016 0.0095 0.012 0.005 Cu 0.023 0.031 0.016 0.020 0.024 0.013 Pb 0.0031 0.0031 0.0051 0.0032 0.0027 0.0020 Mo 0.0014 0.0016 0.0009 0.0006 0.0005 0.014 V 0.0096 0.013 0.010 0.011 0.011 0.018 Cr 0.0040 0.0055 0.0034 0.0065 0.0052 0.011 Ti 0.289 0.267 0.355 0.346 0.308 0.350 P 0.084 0.072 0.218 0.154 0.112 0.085

Table 5.25: Element abundances in surface pelagic clays from different areas (in weight percent). 1) East Indian Ocean (7 samples) 2) East Pacific Rise (8 samples) 3) Central South Pacific (3 samples) 4) West Central Pacific (6 samples) 5) Central Pacific (8 samples) 6) Continental borderland(2 samples) 214

The molybdenum and vanadium contents of sediments from,the North Tropical Pacific range between 2and 30 ppm., and 50and 200 ppm. respectively. However, local high concentrations of molybdenum, 130 ppm. and 160 ppm. respectively, occur in the two samples taken from the continental borderland. These high molybdenum values probably result from an abundance of micronodules in the sediments from this area, molybdenum probably following manganese in these bodies (section 5.5). In the South Pacific, values of aolybdenum between 5 and 20 ppm. and vanadium between 40 and 160 ppm. were found.

COMPOSITIONAL VARIATIONS WITHIN THE INDIAN OCEAN

i) Topography of the Indian Ocean Basin A simplified topographic map of the Indian Ocean basin is presented in Fig. 5.33. Further, in conjunction with the following descriptions the reader is referred to the bathymetric chart of the Indian Ocean presented in the Times Atlas (1959).

The Indian Ocean can be divided into an eastern and a western basin separated by the Mid-Indian Rise. The western basin occupies one third of the ocean and has very irregular relief, being separated into a series of basins by rise areas. From north to south the main topographic features are; the Arabian Basin, The Carlsberg Ridge, the Somali Basin, the Mascarene Ridge, the. Mascarene Basin, the Mauritius Basin, the South-West Indian Ridge and the Kerguelen Basin.

!,'SG 5-33 Topography of the Indian Ocean Basin

4000 m . Arabian C.--te"`"? Basin

Somali Basin o r

a ,/

a Indian West Basin Australian a Bas i n

m 0 u ``, oc,

3‘7 Kergue len .7) Amsterdam a: Basin St. Paul

Plateau

ut 216

By contrast, the eastern basin, occupying two thirds of the ocean, is of more simple relief. It is divided into two by the Ceylon Rise, the Mid-Indian Basin being to the west and the West Australian Basin to the east. ii) Manganese Nodules The regional variation in the composition of Indian Ocean manganese nodules is similar to that found in the Pacific Ocean. Manganese is highest in nodules from the eastern basin where it ranges from 17 to 29 percent(Fig. 5.34). By contrast, in the western basin it i$ lower ranging between 12 and 22 percent. In general,the highest values are found close to the continental areas in the east and low values on the elevated areas in the west.

In contrast to manganese, iron is highest in the western basin, especially. in samples from the volcanic Carlsberg Ridge. However, in the areas of lower relief, in the west, such as the Mascarene and Kerguelen Basins, lower iron values occur. The total range of iron values encountered in nodules from the western basin was from 12 to 26 percent. Nodules from the eastern basin are lower in iron, ranging from 7 to 20 percent and there is little systematic variation within this area ((Fig.5.35).

As in the'case of Pacific nodules, nickel and copper tend to follow manganese. ,The highest values of each occur in the eastern basin, Ni ranging from 0.3 to 2.0 percent and Cu from 0.1 to 1.3 percent (Figs. 5.36 and 5.37). In general, samples low in nickel are also low in copper. FIG5.34 Mn in Indian Ocean Nodules O 25 - 30 0 20 - 25 % 0 15 - 20 %

O 10 - 15 % •

1.3 -4 FIG 5.35 Fe in Indian Ocean Nodules • > 23 ® 20 25 0 15 20 % 0 10 15 % O 5 10 %

30.

03 FIG 5.36 Ni in Indian Ocean Nodules • 1.47 - 3.20 % * •70 - 1.47 % 0 •32 - • 70 7. 0 •1 4 - •32 %

3 0' FIG 5.37 Cu in Indian Ocean Nodules ® • 70 - 1.47 % 0 •32 - •70 %

0 •14 •32 %

0 •07 •14 % o <•07 221

Copper tends to decrease slightly in content away from the eastern margin of the ocean but there is little systematic variation in the nickel content of nodules throughout the eastern basin.

In the western basin both nickel and copper are lower than in the east. Values of Ni range from 0.2 to 1.0 percent and those of Cu from 0.03 to 0.4 percent. Tidthin this area high Ni values were recorded in samples from the Arabian and Kerguelen basins, 0.8 and 1.0 percent respectively, and in one sample from the Carlsberg Ridge (section 5.13) while lower values occur in nodules from the elevated volcanic areas. Similar features were observed in the case of copper, high values occurring in nodules from the basin areas and very low values, generally less than 0.1 percent, in samples from the elevated volcanic areas. In this respect nodules from the western basin are similar to those found in volcanic areas in the Pacific.

The distribution of cobalt and lead in Indian Ocean nodules is in contrast to that of nickel and copper (Figs. 5.38 and 5.39). High values of each occur in the western basin, Co varying.from 0.07 to 1.0 percent and Pb from 0.01 to 0.25 percent. Within this area the highest values of each element occur in samples from the elevated areas, especially the Carlsberg Ridge and the Mascarene Rise, and lower values occur in samples from the basin areas. Nodules from the eastern basin are lower in both elements, Co ranging from 0.08 to 0.4 percent and Pb from 0.007 to 0.12 percent. FIG5.38 Co in Indian Ocean Nodules ® • 707 - 1.47 %

0 •341 - • 707 %

O -147 - •341

0 • 070 - • 147

N ts) N FIG 5.39 Pb in Indian Ocean Nodules O . 147. - •321 % •070 •147 % •032 - •070 :% O -014 , • *012

;007 •

FIG 5.40 Ti in Indian Ocean Nodules • 1-47 - 3.21 ® •707 - 1.47 (;) •321 - •707 •147 - •321

10%... •070 - •147 % •032 - •070 %

•014 - •032 % FIG 5.42 Mo in Indian Ocean Nodules 4

OO •032 - .070 •014 - •032 %

10 O

20*

30* • FIG 5.43 Bain Indian Ocean Nodules

0 •341 - •707 % •147 - •341 %

0 .070 - •147 228

Titanium tends to follow iron in its general distribution in Indian Ocean nodules. Values greater than 1.0 percent often occur in the western basin. In the eastern basin lower values were found, these varying between 0.3 and 1.2 percent (Fig. 5.40).

The elements molybdenum, vandaium and barium show little regional variation within Indian Ocean nodules (Figs. 5.41, 5.42 and 5.43). Vanadium is highest in the elevated areas of the western basin where it varies between 0.03 and 0.10 percent but decreases little towards the eastern basin where values between 0.04 and 0.09 percent occur (Fig. 5.41). In contrast to the behaviour of vanadium, molybdenum is slightly higher in nodules from the eastern basin, than in those from the west (Fig.5.42). The V/Mo ratio is greater than 1 in most samples but drops below this value in a few samples from the eastern basin. Compared with its variatiom'in the Pacific Ocean, the,variation of barium in Indian Ocean nodules is very small, (Fig. 5.43). iii) Sediments So few surface sediment samples were taken in the Indian Ocean (twelve in all ) that a regional appraisal of their compositional variations is not possible. The samples that were obtained came from the eastern basin and the southern portion of the western basin. No samples were obtained from the elevated areas in the west.

The manganese content of the Indian Ocean sediments varies from 0.05 percent close to the continental margin 229 of West Australia, to 1.3 percent in the centre of the eastern basin. In general, higher values occur in the dark red clays than in those of lighter colour. There are no significant compositional differences between samples from the two basins.

The iron content of the samples ranges from 2.2 to 12.0 percent, the highest values being found in sediments containing highest manganese. As in the case of manganese there are no significant compositional differences between the eastern and western basins.

Nickel and copper are higher in sediments from the eastern basin than those from the west. Values range from 85 to 1800 ppm. Ni (this latter value being highly anomalous) and 100 lc 500 ppm. Cu in the former, and from 60 to 130 ppm. Ni and 120 to 16Cppm.Cu in the lattc,r,

All other minor elements show little variation throughout the Indian Ocean. The average minor element composition of East Indian Ocean clay sediments is presented in table 5.25. No clay sediments were taken from the West Indian Ocean.

SUMMARY OF REGIONAL GEOCHEMISTRY AND COMPARISON WITH PREVIOUS WORK

Considerable similarities are observed between the regional geochemistry of manganese nodules from both the Pacific and Indian Oceans. The elements Mn, Ni and Cu are usually more enriched in nodules from the east of these 230 basins, than in those from the west. However, some high values of these elements are found in the west also. Manganese attains its highest concentration in nodules from the Mexican continental borderland, while Ni and Cu attain their maxima in nodules from the pelagic areas of the East Pacific.

By contrast, the elements Fe, Ti, Co and Pb are more enriched in nodules from the west of the Pacific and Indian Oceans than they are in samples from the east. Again, however, this does not hold true for all samples. In nodules from both oceans Mo tends to follow Mn and V follows.Fe, while the distribution of barium is rather irregular.

In nodules from both oceans, Ni, Cu, Co and Pb show a response to depth. Nickel and copper tend to be enriched in nodules from deep water areas while cobalt and lead are enriched in those from shallower areas. This can be seen in both the West Pacific and the West Indian Oceans where nodules from basin areas tend to have higher Ni and Cu contents than do those from adjacent shallow areas.

These results have permitted the Pacific Ocean to be divided roughly into a series of regions containing nodules of similar composition (Fig. 5.44). The average abundances of elements in the nodules from these regions (not calculated on a detrital free basis) are presented in table 5.26. This serves as a useful guide to the overall regional variation in the composition of manganese nodules. Fig 5.44 1 60 ° W S .0. B. Smt. Prov. Nodule composition North Pacific C. B. zones within the

Pacific Ocean

.1a.?oc. tAtS•

West Pacific

South

Pacific South-East

Pacific

I to %.%) 232

Comparison of these results with those of previous workers reveals considerable similarities. Both Skornyakova et al (1962.) and Mero (1965) have presented regional compositional patterns for Pacific nodules very similar to those found in this work. However, aertain differences are apparent. For example, an area of nodules rich in iron in the North-East Tropical Pacific outlined by Mero (1965) and which he labels AD1, does not appear to be reflected in the few samples from that area examined by the writer. However,Mero's observation that two high cobalt regions, one in the vicinity of the Tuamotu Archipelago and the other in the region of the , Mid-Pacific Mountains, has been substantiated; but at the present time there is little evidence to suggest that these two regions, are joined, although it is possible that sampling in the elevated area of the Line Islands would pmduce nodules high in cobalt.

Mero's high nickel and copper region in the South- rest Pacific does, on present evidence, contain some samples high in Ni and Cu. However, many samples from this area contain only moderate quantities of these elements (thble 5.26) and the overall Ni and Cu contents of these nodules are rather less than those found in the high Cu and Ni regions in the East Pacific. Finally, present evidence suggests that Mero's high Co region in the area of the Mid-Pacific Mountains is a little smaller than he suggests. Many samples from the region around 10°N, 170°W examined by the writer, contained only moderate amounts of this element. 233

1 2 3 4 5 6 Mn 34.00 14.93 22.41 18.40 15.91 16.40 Fe 1.62 12.72 8.94 10.86 9.63 14.08 Ni 0.096 0.370 1.126 0.923 0.857 0.414 Co 0.0074 0.478 0.191 0.157 0.245 0.591 Cu 0.065 0.071 0.710 0.313 0.602 0.185 Pb 0.006 0.067 0.024 0.031 0.049 0.068 Ba 0.171 0:351 0.374 0.128 0.171 0.226 Mo 0.072 0.038 0.046 0.034 0.038 0.033 V 0.031 0;062 0.040 0.033 0.036 0.048 Cr 0.0019 0.0057 0.0007 0.0006 0.0010 0.0007 Ti 0,060 0.506 0.389 0.488 0.641 1.007 LOI 21.96 25.65 24.20 27.52 21.90 28.66 FLwiDthW 3535 1131 4553 4141 5025 3551

7 8 9 10 11 12 16.07 13.97 13.72 15.83 15.12 12.59 Fe 13.53 13.11 15.86 11.32 17.71 12.10 Ni 0,529 0,393 0.335 0.512 0.270 0.463 Co 0356 1.127 0.353 0.153 0.490 0.160 Cu 0.385 0.061 0.097 0.330 0.052 0.280 Pb 0.034 0.174 0.062 0.034 0.070 0.018 Ba 0.143 0.274 0.153 0.155 0.171 0.198 Mo 0.033 0.042 0.029 0.031 0.035 0.021 V 0.043 0.054 0.053 0.040 0.071 0.040 Cr 0.0008 0.0011 0.0016 0.0009 0.0012 0.0024 Ti 0.854 0.773 0.817 0.528 0.980 0.708 LOI 25.06 30.87 26.95 27.18 28.53 28.81 Depth 5024 1756 3722 5046 3240 5142

Table 5.26: Average abundances of elements in surface nodules from different regions within the Pacific and Indian Oceans. 1) Continental borderland (3 samples). 2) Southern Borderland Seamount Province (6 samples). 3) North-East Pacific (10 samples). 4) South-East Pacific (11 samples). 5) Central Pacific (12 samples). 6) Central South Pacific (12 samples). 7) West Pacific (30 samples). 8) Mid-Pacific Mountains (5 samples). 9) West Indian Ocean (13 samples). 10)East Indian Ocean (14 samples). 11)Carlsberg Ridge excluding station 5133(10 samples). 12)North Pacific (5 samples). 234

In general, there is less overall variation in the composition of pelagic sediments from the Pacific and Indian Oceans than is found in the case of the nodules. Iron and manganese tend to be enriched in sediments from the central areas of the ocean basins relative to their concentrations in those from the ocean margins. However, local high manganese contents occur in sediments from the continental borderland. Most of the minor elements appear to exhibit little overall regional variation in their content in sediments from either ocean.

Compared with the nodules, relatively little work has been done in the past on the regional geochemistry of pelagic sediments. Goldberg and Arrhenius (1958) have found sediments from the South Pacific to be enriched in manganese relative to those from other areas. Skornyakova (1964) has prepared maps showing the regional distribution of Fe and Mn in Pacific sediments and the results of the present, investigation agree closely with her conclusions. However, as she examined many more samples than did the writer, her regional patterns are more detailed than those presented in this work. Further, because of this detailed sampling some discrepancies between her work and that of the writer exist. In particular, she finds different average values to those presented in this work for iron and manganese in the South-East Pacific. All the samples from this area examined by the writer were taken from the margins of the basin and thus are possibly not compositionally representative of the basin as a whole. A summary of the average composition of clay sediments from different areas is presented in table 5.25. 235

SECTION 5.12

DISCUSSION OF REGIONAL GEOCHEMISTRY

Discussion of the data presented in the foregoing section concerns the chemical relationship between the nodules and their associated sediments, and the causes of the compositional variations in each.

It can be seen from a comparison of the distribution of elements in nodules with their distribution in sediments that few similarities exist. Apparently, iron is the only element that has a similar regional distribution in both deposits. In the sediments, most of the other elements either show little regional variation or vary in an opposite manner to their behaviour in the nodules.

Calculation of the correlation coefficient of the content of each element in the nodules with its content in the associated sediment confirms these conclusions. Only in the case of iron was a significant correlation observed. These observations suggest that the factors determining the regional compositional variations in the nodules are largely 236 different from those diermining the regional compositional variations in the sediments.

Before attempting to explain these regional variations it is useful to discuss the possible sources of elements in the marine environment. Various authors have suggested different sources for elements in both nodules and sediments. Renard in Murray and Renard (1891), and Goldberg and Arrhenius (1958) believed that the bulk of the elements in manganese nodules could be accounted for by the precipitation of dissolved species derived from the continents. By contrast, Murray in Murray and Renard (1891) considered them to be derived from submarine volcanics. This view was shared by Pdtersson (1945) and Bonatti and Nayudu.(1965). In addition, Gumbel (1878), Skornyakova (1964) and Bostrum and Peterson (1966) have suggested a hydrothermal source for at least some of the elements found in pelagic deposits.

In view of these conflicting opinions it is useful to examine the various sources suggested in more detail. Of use in this context is a knowledge of the amount of manganese lost annually, in solution in rivers, from the continents. The relevant data are firstly, the average manganese content of the world's rivers and secondly, the rate of discharge of river water into the oceans. The. former has been conservatively estimated at 11.9 ppb. by Livingstone (1963) based on the. manganese content of Russian rivers (Konovalov 1959), while the same author calculated the latter to be equal to 36,247 thousand cubic feet per second, 237

Converting cubic feet to cubic centimetres, 10,269 x 8 10 cc. of river water enter the oceans each second. As each cc. contains 0.0000119 milligrammes of dissolved manganese the annual amount of manganese lost from the continents is:-

10,269x108x0.0000119x602x24x365x10-9 385,434 metric tons.

This value seems small when compared with Mero's (1965) estimate of 1,656 billion metric tons of nodules in the Pacific basin alone, particularly so in view of the fact that firstly, the Pacific Ocean receives a smaller share of continental run-off, relative to its size, than the other major oceans, and secondly, sub- surface nodules have not been taken into account in Mero's estimate.

In addition, the manganese disseminated throughout pelagic sediments has to be taken into account. Using 13 Goldberg and Arrhenius' (1958) estimate of 2.8 x 10 gm. of pelagic clay deposited annually and assuming a manganese content of 0.434 percent, 90 percent of which, according to Chester and Hughes (1966) is in the form of secondary oxides, some 900, 000 metric tons of manganese are precipitated from solution in the worlds oceans annually. Even allowing that some of this manganese may have entered the oceans in particulate matter and has been liberated subsequently (page 246), there does seem to be a discrepancy between the amount of manganese lost from the continents in solution and the amount present in the ocean basins. 238

These figures indicate that while a proportion of the manganese in nodules can be accounted for by its derivation from the continents, other sources must be available. In this context, it is significant that Mackenzie and Garrels (1965) and Arrhenius et al (1964) have presented evidence to show that silicate materials undergo dissolution on the sea floor.

In addition, Bonatti and Joensuu (1966) have reported that the alteration products of submarine basalts are impoverished in manganese and other ferrides relative to their content in the original unaltered basalt. Further evidence of a volcanic source of elements on the sea floor is presented by Bonatti and Nayudu (1965) and in Chapter 2 of this work.

It would appear therefore that both continental and volcanic sources of elements in nodules and sediments are possible. This conclusion has been reached also by Skornyakova et al (1962) and Arrhenius et al (1964).

More difficult to evaluate on a regional scale is the importance of hydrothermal solutions as a source of elements in nodules. Niino (1959) has found manganese deposits associated with submarine hydrothermal manganese rich springs off the coast of Japan. Hewett (1966) has suggested that certain terrestrial manganese deposits result from hydrothermal activity. In view of the association between hydrothermal activity and vulcanism on land, it is perhaps reasonable to extend this relationship to the deep-sea floor also. However, in this connection it should be emphasised that hydrothermal waters are generally 239

considered to be dominantly or entirely of meteoric origin; the dissolved matter being derived from the rocks through which,the waters pass (Ellis and Mahon 1964). Accordingly, the elements introduced into the sea by hydrothermal springs are most probably not derived from primary magmatic sources but from the rocks of the ocean floor.

That hydrothermal activity can be of importance on a local scale in injecting iron and manganese into sea water has been shown by Zelenov (1964). This author has found active fumaroles associated with the submarine Banu 'Nuhu volcano, Indonesia, through which hot jets of iron and manganese rich solutions are debouching onto the sea floor. The iron and manganese in these jets has been observed to be separating out as a hydroxide suspension only one metre above the vents and the surrounding rocks are heavily coated with layers of precipitated hydroxides. These deposits were reported to contain all the minor elements found in deep sea manganese nodules, but in different proportions.

Another possible supply of elements to the sea floor, that of extra terrestrial materials, has been suggested by PeWersson (1959). While these, usually in the form of cosmic spherules, have been found in pelagic deposits (Murray and Renard 1891, Carstang and Frederickson 1958, Brunn et al 1955) it has been shown by Wiseman (1964) and Chester and Hughes (1966), that they are quantitatively unimportant. Therefore, they need not be considered further as an important supply of elements to pelagic deposits, 240

Summarising previous work, it appears that both the continents and submarine volcanic rocks are potential sources of the elements in nodules and sediments. It is not possible to make a quantitative estimate of the relative importance of these sources at this time. However, it is possible to explain some of the regional compositional variations found in pelagic deposits in terms of one, or other, or both sources.

REGIONAL VARIATIONS IN THE COMPOSITION OF SEDIMENTS

Only the elements iron and manganese have been found to vary to any significant degree,in the pelagic sediments examined. In general these are enriched in sediments from the centres of the oceans and depleted in those from the marginal areas.

Consideration of the phases in which these elements occur in pelagic sediments is useful in attempting to explain their regional compositional variations. Accord- ing to Goldberg and Arrhenius (1958) and Chester and Hughes (1966) most of the manganese present is in the form of micronodules. By contrast, only a small proportion of the iron occurs in this form, the remainder being present in the detrital clay and colloidal fraction of the sediment (see section 5.5)

The abundance of manganese in the authigenic phases of the sediment, quantitatively important in areas of low detrital sedimentation rates, explains its high concentration in the Central South Pacific. 241

According to Goldberg and Koide (1962) the rate of sedimentation in this area, about 0.5 mm. per thousand years, is amongst the lowest found in the oceans. Owing to this low sedimentation rate,authigenic manganese bearing phases are able to accumulate without suffering dilution and thus the total manganese content of the sediment is high. By contrast, in the marginal areas of the oceans, receiving a much larger contribution of detritus derived from the continents, the authigenic manganese bearing phases are diluted and thus the total manganese content of the sediment is lower.

An exception to this generalisation is found in the sediments from the continental borderland. In this area the manganese content of both the sediments and the nodules is higher than average. This is consistent with the upward migration of divalent manganese from reducing sediments at depth (Lynn and Bonatti 1965). On burial,Mn4+ is re- 2+ duced to Mn and passes into solution. The reduced manganese migrates upwards until it reaches oxidising conditions again when it is re-oxidised to Mn. This leads to a net upward migration of manganese in the sediment causing its enrichment in the surface layers. This process is only likely to be operative in areas of high sedimentation rates where reducing agents in the sediment are in- sufficiently oxidised before burial. In the pelagic areas of the oceans where sediments are oxidised down to considerable depths,upward migration of manganese is unlikely to occur.

The enrichment of iron in sediments from the Central South Pacific cannot, as in the case of manganese, be 242 explained by its presence in micronodules, Chester and Hughes (1966)having found that these bodies contain a low proportion of the total iron in the sediment, about 1.5 percent. These authors consider much of the iron in pelagic sediments to be present in the clay and colloidal fractions.

Skornyakova (194) has suggested, in view of the in- cidence of vulcanism in the area, a hydrothermal source for much of the iron in South Pacific sediments. At the present time there is little direct evidence to support this hypothesis. Indeed, the iron content of the basic volcanic rocks, the weathering products of which the sediment is predominantly composed (Murray and Renard 1891, Peterson and Goldberg 1962, Griffin and Goldberg 1963) would have been about the same as the iron content of the present day sediments (table 5.25), the average iron content of basalts being, according to Rankama and Sahama (1960) 8.71 percent. Alteration and weathering of these original volcanics will have resulted in a redistribution of the iron and its abundance in the sediments can largely be accounted for by this mechanism. Thus no extensive hydrothermal source of this element is needed.

A possible subsidiary source of iron in the South Pacific, but which will be of greater importance in the marginal areas of the basin, is the sedimentation of finely divided particulate matter derived from the continents. According to Goldberg and Arrhenius (1958) iron prevails in solid phases during the major part of its residence in the oceans. 243

The minor elements in pelagic sediments exhibit few significant regional variations. As in the case of the major elements their partition between the various phases of the sediment, and. the relative abundance of these phases one to another, will probably be important factors in determining their concentration in the sediment as a whole.

Elements concentrated in the authigenic phases of the sediment would be expected to be abundant in areas of low detrital sedimentation rates, as found in the case of manganese. However, with the exception of Ni and Mo in sediments from the continental borderland, there is no significant enrichment of the minor elements in sediments rich in manganese. This suggests that the other minor elements are less concentrated in the authigenic manganese phases of the sediment than are Ni and Mo. Chester and Hughes (1966) have shown that Ni is partitioned in roughly equal proportions between the clay and micronodule fractions of the sediment. Thus the above information, coupled with the weak association between most of the minor elements, excluding Ni and Mo, and manganese (section 5.4), indicates that the bulk of the minor elements are concentrated in phases of the sediment other than the micronodules.

In view of the presence of V, Cr and Ti in the detrital phases in the sediment (section 5.5), it follows that their abundance in the sediment as a whole will depend on the nature and quantity of these detrital phases. In particular, their concentration in the source rock from which the sediment was derived will be an important factor, 244

The higher concentration of V and Cr in sediments from the continental borderland area than in those frorg other areas (table 525) is an example of how the detrital constituents can affect the bulk composition of the sediment as a whole. Part of this high concentration Probably results from the high rate of detrital sedimentation to be expected in areas near the continental margins. However, more important is the nature of the detrital -phases themselves. Bonatti and Arrhenius (1966) have shown that much of the sediment in the continental borderland area is composed of eolian weathered, wind- blown, material from the deserts of the South-''Aiest United States, and northern Mexico. This material having been subjected to mechanical rather than chemical weathering will be poorly leached of elements such as V and Cr which are prone to enter solution in an aqueous oxidising environment (section 5.5).

Thus the high V and Cr content of the continental borderland sediments is considered to result firstly, from their being the products of eolian erosion processes, and secondly, from their probable shorter residence on the sea floor than the more degraded (at least as far as V and Cr are concerned) detrital materials found in the pelagic areas of the oceans.

REGIONAL VARIATIONS IN THE COMPOSITION OF MANGANESE NODULES It has been shown that the regional geochemistry of manganese nodules from the Pacific Ocean is very similar to that found in the Indian Ocean. 245

In general,nodules are rich in Mn, Ni and Cu in the east of each of these basins and rich in Fe, Ti, Co and Pb in the west. Further, compositional similarities are observed between nodules from volcanic areas in both oceans. This overall similarity strongly suggests that the same factors are influencing the composition of nodules in both oceans. In order to understand these factors it is useful to consider regional compositional variations in nodules in terms of the possible sources of the elements they contain, and their environment of deposition.

a) Manganese Previous explanations of the regional geochemistry of manganese in nodules include bacterial action and regional variations in the composition of submarine volcanics.

Mero (1965),noting the observation of Ljunggren (1953) that bacteria precipitate iron and manganese from sea water,has suggested that the high manganese content of nodules near the continental borderland could be a result of this. However, he also suggested that differ- ential precipitation of iron and manganese leached from volcanic rocks, or derived from the continents, could be important.

Both Graham (1959) and Ehrlich (1963) have suggested that bacterial precipitation of manganese may be important in the growth of nodules. Further, Wangersky and Gordon (1965) thought that sedimentation of divalent 246 manganese in particulate matter, followed by bacterial breakdown of the organic material and release of the Mn2+, might account for the supply of manganese necessary for the formation of manganese nodules. However, these authors note that no regional variations in the quantity of particulate manganese have been found. Bacterial action in removing elements from sea water can be regarded as a possible mode of precipitation of the elements in nodules. However, there is no evidence that it is likely to account for their observed regional compositional variations.

An alternative suggestion by Bonatti and Nayudu (1965) is that the supposedly high manganese content of volcanics in the region of the East Pacific Rise could account for the high manganese content of nodules found in that area. This suggestion is based on the possible greater acidity of the East Pacific Rise volcanics, compared with those from other areas.

Examination of the limited data on the composition of submarine basalts from the Pacific (Engel and Engel 1965, and Poldervaart and Green 1965) reveals no significant increase in the manganese content of basalts from the East Pacific Rise, relative to its content in those from other areas. Indeed, one sample of basalt from the Henderson seamount (25°33.5'N 119°33.3'14) containing 0.14 percent Mn0 was coated with acrust containing 22 percent Mn (Goldberg 1954). By contrast, a basalt sample from the Mid-Pacific Mountains (station MP25, 19°07'N, 169°44'W) containing 0.20 percent Mn0 was coated with a manganese crust containing 13 percent Mn (Appendix 2), (Basalt analyses from Poldervaart and Green 1965). 247

Thus in these samples there is an inverse relationship between the manganese content of the basalt and that of the surrounding crust. In addition, examination of the plagioclases in the cores of nodules of widely varying compositions (Chapter 4, section 2), revealed no significant acidity variations.

It would appear therefore that regional variations in the composition of manganese nodules are not the result of regional variations in the composition of their associated volcanics.

It is the writer's opinion that the regional variation in the manganese content of nodules can be explained in terms of a continental source for much of this element in the marginal areas of the oceans,and a probable volcanic source in the volcanically active central areas. Divalent manganese, entering the oceans from streams and rivers, is unstable under moderately oxidising conditions. and thus would be expected to precipitate in near-shore areas. This appears to be the case, for according to Manheim (1965) and references therein, there is a higher concentration of manganese in coastal waters than in the open ocean. This would account for the high manganese content of nodules adjacent to the continents, and its decreasing concentration towards the open ocean. However, the high manganese content of nodules from the continental borderland cannot be entirely related to the preceipitation of manganese derived from the continents, Lynn and Bonatti (1965) having shown ti-at the upward migration of manganese from buried reducing sediments is an important contributary source. 248

In addition to manganese derived from the continents other sources of this element are probably important in areas far from land. Bonatti and Nayudu (1965) have suggested that much of the manganese in nodules from volcanic areas is derived from the volcanics themselves. It is difficult to evaluate this hypothesis on a regional scale for, excluding the East Pacific Rise, no increase in the manganese content of nodules occurs towards volcanic areas. However,there is abundant evidence that elements are supplied to the ocean floor by submarine volcanic activity and manganese derived from volcanic sources could be disseminated throughout the sediment in the form of micronodules and perhaps contribute to the formation of buried macronodules, both more abundant in the volcanic areas than in the non-volcanic areas of the Pacific (see section 5.8).

It is concluded that the regional geochemistry of manganese in nodules is largely related to its source. It is higher in areas close to a continental source than in areas far removed from the continents. In these latter areas volcanic sources probably become important.

b) Iron The regional variation in the iron content of nodules cannot be explained by assuming a significant continental source for this element. Krauskopf (1957) has shown that with increasing Eh iron is precipitated from solution before manganese. Thus Mero (1965) has suggested that iron rich nodules should be found closer to the continents than those rich in manganese, and reports the presence of one such area off the Pacific coast of Central America. 249

Manheim (1965) has found that nodules from inshore areas tend to be richer in iron than in manganese, and reviews evidence that the iron content of coastal waters is greater than that of the open ocean. It would appear, therefore, that the bulk of the iron weathered from the continents in solution is either precipitated in inshore areas or on land. This would indicate a local source for the iron enriched in nodules from the central areas of the oceans.

The association of iron rich nodules with the volcanic areas of the Mid-Pacific Mountains, the Central-South and South-West Pacific and the ''!est Indian Ocean suggests, as possibly in. the case of the sediments from at least some of these areas, that much of the iron is derived from volcanic sources.

:The observation of Murray and Renard (1891) and others, that,in the volcanic areas of the South Pacific,the weathering of submarine volcanics is active, as it will be in other volcanic areas also, indicates that iron will be released and be available for incorporation into the forming nodules and sediments. That the regional geochemistry of iron is similar in both nodules and sediments suggests that the same factors are affecting its concentration in each.

A possible objection to deriving the iron in both nodules and their associated sediments from the weathering of submarine basalts is that their combined iron content, per unit volume of sediment, is probably in excess of the iron content of the same volume of original basalt. How- ever, if the bulk of the sediment is formed from the 250 weathering of submarine volcanics and taking into account a) that a proportion of the basalt will be removed in solution on weathering, and b) the relative lack of mobility of iron under oxidising conditions, it would be expected that iron would be concentrated in the residual sediment relative to its concentration in the original basalt. In this manner the enrichment of iron in both nodules and sediments from volcanic areas could be accounted for.

In addition to the slow weathering of submarine volcanics as a source of iron, hydrothermal activity is possibly of importance locally. Bonatti and Joensuu (1966) have proposed a hydrothermal origin for some iron rich deposits from the crest of the East Pacific Rise. Further, Bostrom and Peterson (1966) suggested that the enrichment of iron in sediments, also from the crest of the East Pacific Rise, is the result of hydrothermal activity.

It is concluded that the regional geochemistry of iron in nodules, like that of manganese, is primarily dependent on its source. Continental sources of iron are less important than local sources within the oceans. Of these local sources the alteration and breakdown of submarine volcanics is considered to be of regional importance with hydrothermal activity possibly important locally. c) The Minor Elements One of the major factors affecting the geochemistry of the minor elements in nodules is their depth of formation. 251

The relationship between the concentration of Ni, Cu, Co and Pb in nodules and their depth of deposition has been discussed in section 5.5. Areas in which nodules are rich in Ni and Cu include the East Pacific, the East Indian Ocean and to a lesser extent the :west Central Pacific. The nodules from all these areas have an average depth of deposition of greater than 4000 m. By contrast, the nodules in which Co and Pb are enriched, those from the Mid-Pacific mountains and to a lesser extent the Central-South Pacific and the Carlsberg Ridge, were collected at depths averaging less than 4000 m.

Thus the regional variation in the content of Ni, Cu, Co and Pb in nodules appears to be largely a function of regional variation in depth.

The regional distribution of Co and Pb in nodules is more irregular than that of Ni and Cu. This largely results from the irregular distribution of shallow water areas in the Pacific and Indian Oceans. For example, the highest values of Co and Pb are found in nodules from seamounts, obviously of limited areal extent, while nodules from deeper areas in the same general region tend to have lower concentrations of both elements.

The manner in which depth could possibly affect the concentrations of Ni, Cu, Co and Pb in nodules has, been discussed in section 5.5 and will not be considered here. However, depth alone is unlikely to be the only factor causing variations in the concentrations of these elements. In the case of Co, both Nero (1965) and Burns (1965) stress the importance of local volcanic sources. 252

In addition, the high concentration of Ni and Cu in nodules from the East Pacific cannot entirely be the result of depth,for nodules taken from similar average depths in the West Central Pacific and in the North Pacific contain smaller ouantities of both elements. The reasons for this are not clear but it is of significance that todorokite was commonly encountered in the East Pacific but not in the west, and nodules containing this mineral have been found to be enriched in Ni and Cu (section 5.4).

Regional variations in the content of the other minor elements in nodules are not as large as in the case of Ni, Cu,Co and Pb. Molybdenum and vanadium show little overall variation throughout the Pacific and Indian Oceans. Possibly much of the variation they do show results from variations in the major element content of the nodules, Mo following Mn rather closely, and V following Fe (sections 5.4 and 5.5). In a similar manner the close association between Ti and Fe suggests that similar factors are affecting their distribution.

The causes of the variation in the barium content of Pacific nodules are not clear. The high barium content of some nodules associated with seamounts could suggest a volcanic source for at least some of this element. In this context it is perhaps significant that Arrhenius and Bonatti (1965) have shown that Ba is enriched in sediments in the vicinity of the East Pacific Rise and have suggested a hydrothermal source for much of this element. 253

In conclusion, the regional geochemistry of manganese nodules appears to be related to a number of factors. These include their closeness to continental or volcanic sources of elements, possible hydrothermal activity, and the environment of deposition largely influenc- ed by depth. Other factors such as the upward migration of reduced manganese from buried sediments become important locally.

These tentative conclusions leave much unexplained. For example, problems are posed by the low minor element content of the nodules from the continental borderland and the anomalous compositions of nodules from the South- ern Borderland Seamount Province compared with those from the East Pacific as a whole.

In order to explain the low minor element content of the continental borderland nodules, Arrhenius et al (1964) have suggested the slow precipitation of manganese from sea water leading to its separation from other ionic species. However, the instability of divalent manganese under oxidising conditions would tend to suggest that the bulk of this element is precipitated soon after entering the oceans. Manheim (1965) believed this to be the case and has suggested a rapid growth rate for nodules close to the continents. If this latter suggestion is true the low content of trace metals could be due to the manganese oxides remaining for only short periods in contact with sea water thus reducing their effectiveness as scavengers of minor elements. 254

The large compositional differences between encrustations from the Southern Borderland Seamount Province and nodules from the rest of the North-East Pacific raises considerable problems also. Possibly,contributions of elemente_fhm the submarine volcanics around which the manganese crusts are forming are leading to a 'dilution' of manganese derived from the continents and from possible local sources. In general, it would be expected that there would be less separation between elements derived from a local source than if they had passed a considerable period of their history in solution in sea water. The crusts from this area tend to show compositional similarities to those from volcanic areas in the centres of the ocean basins and thus similar factors could be influencing their composition in both areas. 255

SECTION 5.13

MANGANESE NODULES FROM THE CARLSBERG RIDGE

Information concerning the manganese nodules collected from the Carlsberg Ridge by R.R.S. Discovery has been presented to illustrate various points throughout this thesis. Their petrography and overall form have been described in Chapter 2, internal compositional variations in Chapter 3, and various aspects concerning their geochemistry in sections 5.6, 5.7 and 5.9. It is proposed in this section to briefly recapitulate some of these features and discuss the geochemistry of the nodules from the area as a whole. i) DESCRIPTION OF THE SAMPLES AND SAMPLE SITES The area from which these samples were obtained is on the southern flanks of the Carlsberg Ridge. It contains rugged volcanic topography and has been described with the aid of underwater photographs by Laughton (1967)who has termed it area 4c (Fig. 5.45). 59°501 60°001E 60°20' 3°OO' N

2°40'

0 10 20 nautical miles FIG 5.45 Bathymetry of area 4C

from Laughton 1967

257

Nodules were obtained at three sites within this area, Discovery stations 5133, 5136 and 5138. Station 5133 was taken part way down the south facing slope of a seamount about sixteen miles to the east of the other two stations (Fig. 5.46). At this station two populations of nodules were collected, a population of large nodules similar to those seen in plate 13, and a population of small nodules also (table 5.27).

Stations 5138 and 5136 were taken, respectively, on the top and on the south-east spur of the same seamount (Fig. 5.47). From station 5138 one population of large elipsoidal nodules containing large cores of altered palagonite tuff were obtained (plate 1). At station 5136 two populations were found, a population of manganese crusts similar to those coating bedrock shown in plate 14 and a population of small nodules also. sample Depth of Size of site Location water(fms) nodules(cm) Core 15133 02°45.4'N-60002.8'E 2110-2170 0.5-1 Absent 5.0-7 Present

:5136 02°46.6'N-59°52.8'E 1845-1940 0.5-1 Absent Encrust- ation Present :5138 02°47.9'N-59°52.1'E 1775-1840 10.0-15 Large Nuclei Present

Table 5.27: Location of sample sites and sizes of nodules. 0 6 0° 0 0' E 0 6 0° 05'E N 258

z in st 5133 0

Fig 5.46 Bathymetry of station 5133 in fathoms

0ix, 590 5 E 59° 55'E

190

z 0 0 Fiy5.47 Bathymetry of stations 5136& 5138 in fathoms Data from A. S. Laughton N. 1. 0. 259

PLATE 13 Underwater photographs of manganese nodules at station 5132 on the Carlsberg Ridge. Reproduced by permission of A.S. Laughton. ei- AL C' 1 Q *Pe rs•• r •

1&A (

• I • o vi

4. 11., , e

-0 ^ 46 I. 0 * • ''' .' 4 46 wr d Or t • er • • tioSba" ti %%AM 261

PLATE 14 Underwater photographs of manganese coated submarine volcanic rocks at station 5137 on the Carlsberg Ridge. Reproduced by permission of A.S. Laughton.

263

ii) RESULTS On.briefly recapitulating the geochemistry of these nodules, two features of particular interest emerge. First- ly, at station 5133 two chemical populations occur (section 5.7). In the small nodules, Ni, Mn and Cu are present in significantly higher concentrations, and Fe and Ti in lower concentrations than in the crust of the one large nodule from this site analysed. Bezrukov (Institute of Ocean- ography, U.S.S.R., personal communication 1966) has kindly analysed one of the other large nodules from this site and finds concentrations of all elements within, or very close tci the range of composition found in the nodule analysed by the writer.

Secondly, large compositional variations occur between the sets of small nodules at stations 5133 and 5136. The nodules at station 5133 contain significantly higher concentrations of Ni, Cu and Mn,and lower concentrations of Fe, Co and Ti,than those from station 5136, (section 5.9). Mineralogical differences between these nodules also occur.

These two features are almost unique to this area. At none of the other stations investigated were two chemical populations of nodules found. In addition, in only one other area, that of King's Trough in the North Atlantic, also an area of strong topographic contrasts, were found large variations between the composition of nodules from adjacent sites. Accordingly, the discussion of the geochemistry of the nodules from area 4c will be centred on these features. 264 iii) DISCUSSION Variations between Sites The compositional variations between nodules from the different sites in this area need to be considered in the light of the general geochemistry of nodules from the Carlsberg Ridge as a whole. It has been shown in Section 5.11 that, in keeping with nodules from other areas of rugged volcanic topography, nodules from the Carlsberg Ridge are higher than average in Fe, Ti, Co and Pb and lower in Ni and Cu.

Thus the nodules from stations 5138 and 5136 are similar in composition to the bulk of the nodules from the Ridge as a whole. Only the small nodules from station 5133 differ significantly from this pattern, both compositionally and mineralogically.

Attempting to explain the differences between the nodules from station 5133 and those from the other stations, presents considerable difficulties. However, there is one important point that has to be taken into consideration. This is the mineralogical difference between the nodules from station 5133 and those from the other stations in this area.

The small nodules from station 5133 contain todorokite as their principal mineral phase, while nodules from other sites contain either birnessite (Elfin° 2 of Buser and Grutter 1c)56) or were too poorly crystalline for their mineralogy to be determined. 265

It has been shown that both Ni and Cu are preferent- ially enriched in todorokite rich nodules (section 5.4) . Thus the factors bringing about the enrichment of these elements in this mineral could be the cause of their enrichment in the small nodules from station 5133.

The factors affecting the formation of todorokite are very unclear. It is generally more prevalent in the deeper areas of the oceans than at shallower depths (chapter 4). However, large depth variations cannot be an explanation of its presence in this area. Although station 5133 was taken in deeper water than the other stations, the difference only amounts to about two hundred fathoms. Thus some other mechanism must be invoked to explain the presence of todorokite at station 5133.

It has been suggested in Chapter 4 that the variation in the mineralogy of manganese nodules with depth could be the result of variations in the degree of oxygen- ation of sea water. If this is the case, the formation of todorokite at station 5133 could result from redox differences between the environment of deposition at this site and at the others. There are at least two factors which could possibly cause redox variations within this area. Firstly, submarine vulcanism and secondly, local variations in the environment of deposition.

Considering submarine vulcanism, Bonatti and Nayudu (1965) have stated that considerable variations in the redox conditions of the bottom waters are likely to occur during a submarine volcanic eruption. 266

This is considered to result from the interaction of acid gases and reduced phases in the volcanics, with alkaline, oxygenated sea water. They believed that unstable redox conditions could lead to the fractionation of elements introduced from volcanic sources leading to the formation of deposits of widely varying chemical com-. position,.but all derived from the same source. This mechanism, if operative, could account for any redox differences between the nodules at station 5133 and those from the other stations. Selective precipitation of elements from a single hydrothermal source, or contributions of elements from different but related hydrothermal • sources could also contribute to the chemical differences found in this area. That iron and manganese can be supplied to the sea floor by local volcanic exhalations is shown by the observation of Zelenov (1964) on the submarine volcano, Banu Wuhu, Indonesia (section 5.12).

Some evidence for hydrothermal activity in this area is provided by the presence of the altered basalt fragment in the crust of one of the nodules from station 5138 (chapter 2). This basalt is similar to basalts from an adjacent area which have been subjected to hydrothermal metamorphism (Matthews, Vine and Cann 1965).

If alternatively, the differences between the nodules from station 5133 and those from the other stations are a a result of local environmental factors and not submarine vulcanism, the nature of the environmental differences has to be explained. Consideration cf the bottom topography at the different stations is useful in this context. 267

Both stations 5136 and 5138 were located at or near the top of a seamount, while station 5133 was located some 300 fathoms from the top of a seamount.

According to Nero (1965)and others, bottom water conditions are highly oxidising on the tops of seamounts where current action is often strong. Indeed, Laughton (1967) reports that in this area nodules are abundant on the tops of seamounts and suggests that current winnowing has possibly occurred. Current action leading to well oxygenated sea water would explain the enrichment of cobalt in the samples from station 5136, this element being concentrated in nodules forming under oxidising conditions at the tops of seamounts (section 5.5).

By contrast, the position of station 5133 further down the slope of a seamount could imply that conditions were less oxidising here than at the other stations. If this is the case, and the differences between the nodules in this area are the result of variable redox conditions, the anomalous composition and mineralogy of the nodules from station 5133 could perhaps be accounted for.

The two alternative suggestions therefore to explain the compositional variations in this area are either that they result from the action of submarine vulcanism, or from local variations in the redox conditions under the influence of bottom topography. It is not possible at this stage to reach a firm conclusion. However, it is perhaps significant in terms of the latter that similar variations in the composition pf nodules have been found in an 268 area of strong topographic contrasts in the North Atlantic (section 5.9). Further work to be done in area 4c on R.R.S. Discovery in 1967 should help to resolve this problem.

b) Variations within one site The presence of two chemical populations of nodules at station 5133 is, if anything, more difficult to explain than the chemical differences between the sites in this area. If the nodules were all forming at the same time it would be expected that they would be similar in nature. Thus it is possible that the two populations were formed at different times and under different conditions. Alter- natively, they could have formed at the same time but in different micro-environments. In either case their present concentration at the same site must result from factors operating after their deposition.

The simplest explanation of this observation is that the nodules are in fact separated in space and not present at the same site together. If this is the case they could have been sampled at different points in the dredge traverse. The dredge is not usually on the sea floor for the whole of a traverse, and even if it were, two populations of nodules forming in different micro-environments could have been sampled. In this context it is perhaps significant that Laughton (1967) has found variations in the form of manganese nodules along underwater camera traverses in this area. These, however, were longer than the dredge traverse at station 5133. 269

An alternative explanation is that both populations are not exposed at the surface. Examination of bottom photographs of station 5132, upslope of station 5133, reveals the presence of nodules similar to the large nodules from station 5133, but not the presence of the small nodules. Further, Laughton (1967) reports that in some photographs nodules appear to be partially buried. It is possible therefore that one population has been formed and buried, and another population formed at the surface, but by the dredge cutting into the sediment both populations have been sampled.

A second alternative explanation is that the nodules were formed at different times and buried or even formed d_thin the sediment, and have been exposed at the present day surface by winnowing of their surrounding sediments. However, station 5133 was not near the top of a seamount where Laughton (1967) believes current winnowing to be most active.

A third alternative explanation could be that the two populations were separated in space but since their formation have become mixed. The nodules at station 5132 could possibly have moved clown the slope to become mixed with the population of small nodules forming at station 5133. If this has occurred it is to be expected that the sediment would have moved down the slope also and if this is the case one might expect all the nodules at station 5133 to be buried. Accordingly, this is not considered to be a likely mechanism. 270

At the -)resent time it is not possible to say which, if any, of these mechanisms are resulting in the two populations of nodules at station 5133. As in the case of the compositional differences between the sites in this area further research aboard R.R.S. Discovery should help to resolve this problem.

From the practical viewpoint the data. obtained in this area are of considerable significance, irrespective of the genesis of the manganese accumulations. It is apparent that at least in this area, and in the Kings Trough area, considerable variation in the composition of nodules can occur over short distances. It would be desirable therefore in any assessment of the economic potential of manganese nodules to take into account the possibility that local large variations in the concentrations of ore elements may occur within a larger area of relatively little variation. The factors determining such local variations can only be determined by much more detailed sampling in critical areas, 271

SECTION 5.14

NOTE ON SOME pH AND Eh DETERMINATIONS IN ATLANTIC SEDIEENT CORES. i) Introduction As a preliminary to an investigation of the state and distribution,of manganese in sediments from different environments, the writer conducted pH and Eh measurements on sediment cores during his participiation in the scientific investigations conducted aboard R.R.S.Discovery in the North Atlantic in 1966. Measurements were made on cores taken from the foot of the continental slope, frog seamounts, a deep and a ridge. The location of these cores is shown in Fig. 5.4g. ii) Methods The cores examined, seven in all,,were obtained using gravity coring devices. Initially,a wide plastic core barrel was used but this proved to be unsuccessful in anything but the softest sediment and later cores were collected using a stainless steel barrel. 0

20 15 10 5

O N

FIG 5.48 Sample distribution inthe N.Atlantic 273

In order to conduct pH and Eh measurements, holes were drilled through the plastic core barrels through which the electrodes were inserted. Cores collected using the steel barrel were extruded on deck and taken to a constant temperature laboratory uhere they were examined immediately. Care was taken to minimise oxidation of the cores before the pH and Eh measurements were made.

The measurements were made using specially. shaped electrodes, supplied by Analytical Measurements Ltd., in conjunction with a battery operated meter. A needle shaped glass electrode was used for pH measurements and a similar shaped platinum electrode for Eh measurements. A saturated calomel electrode was used in each case as a reference. Standards for pH measurements included buffers at a pH of 4.01 and 9.15, While for the Eh measurements a mixed solution of M/300 potassium ferricyanide and M/300 potassium ferrocyanide was used. This latter developed an Eh of 183 millivolts against the saturated calomel electrode. All Eh values were corrected with respect to the standard hydrogen electrode. Reproducibility-was within about 10 percent and meter drift ceased after about ten minutes.

iii) Core descriptions and results a) Station 5937, 46°13'N,05°43'W, 4658 m. P.V.C. core barrel, 10 ft. long. Penetration complete but only 90 cm. of core retained. This consisted of grey- green clay. Taken near the foot of the continental slope in the Bay of Biscay. 274

Depth(cm) *S.W. top 14 24 35 48 61 pH 8.0 7.8 7.4 7.2 7.2 7.1 7.0 Eh 375 135 195 75 -45 -185 30

S. W. = sea water collected from the slurry at the top of the core. N.B. Eh in millivolts. b) Station 5942, 45°20.5'N, 05°21'W, 4031m. P.V.C. core barrel 10ft. long. 169cm. of greenish grey clay obtained, the top four inches of which consisted of brown mud. Taken on Gascony Seamount.

Depth(cm) 11 34 55 76 99 125 149 166 pH 7.4 7.2 7.2 7.2 7.3 7.2 7.0 7.0 Eh 515 55 15 -15 20 5 0 5

c) Station 5947, 45°04'N, 8°00.3'W, 4389 m. Stainless steel barrel 5 ft. 10', long. 171cm. of greenish buff ooze obtained. Taken on Cantabria Seamount.

Depth(cm) top -17 32 47 69 89 130 155 170 pH 7.2 7.0 7.4 6.9 7.0 7.0 7.0 6.8 7.0 Eh 525 510 455 450 425 445 420 375 465 275 d) Station 5970, 43°04.8'N, 19°49.0W, 5952m. Steel core barrel, 12 ft. long. 210 cm. of brownish clay obtained. This contained a sand layer at 69cra. Taken in Peake Deep.

Depth(cm)2 24 46 69 72 115 139 161 184 207 pH 7.0 7.2 7.1 7.3 7.1 6.8 6.8 7.0 7.1 7.2 Eh 110 70 0 0 -30 -30 -40 -45 -30 220 e) Station 5971, 43°01.4'N, 20°07.0'W, 5300m. Steel core barrel 12ft.long. Core length 180cm. Lower portion (below 70cm) solid. Upper portion, pale grey-green clay. Taken on the lower slopes of Palmerb Ridge.

Depth(cm) 5 13 49 69 pH 7.2 7.6 6.9 7.0 Eh 530 470 390 390 f) Station 5972, 42°57.8,N, 20°07.3'W, 4507m. Steel core barrel, 12ft. long. Core length 214cm. Soft brown ooze. Taken on middle slopes of Palmerb Ridge. 276

Depth(cm) top 31 52 83 113 144 175 210 pH 7.8 7.2 7.2 7.1 7.2 7.0 7.4 7.2 Eh 540 470 470 440 430 470 460 470 g) Station 5984, 43°06.2/N, 20°09.5'WJ, 5944 m. Steel core barrel, 12 ft. long. Core length 370cm. Upper portion brown clay. Below 69 cm. grey-green clay. Taken in Peake Deep.

De-oth(cm) 2 27 49 69 107 149 176 229 304 357 pH 7.6 7.2 7.0 7.0 7.0 7.0 7.4 6.8 6.6 6.6 Eh 430 430 410 460 150 50 40 30 25 80

iv) Discussion These preliminary data are of interest in terms of the degree of oxidation of marine sediments. In general, both pH and Eh decrease with depth in the sediment. However, local reversals are found in some cores. These could result from local conditions prevailing at different horizons and frorg variations in sediment type. Features such as these may become apparent when the cores are subjected to sedimentological analysis. The high Eh at the base of some cores could result from sea water entering the base of the corer as it is pulled up from the bottom. 277

Considerable Eh variations are found both within single cores and between cores from different locations. The Eh is highest in cores from elevated areas and lower in those taken at greater deaths. In cores from both environments, Eh decreases with increasing depth in the sediment, but tends to fall off more sharply in the cores collected from the deepshaninthose from the elevated areas.

The fairly high overall Eh of the cores from the elevated areas, and the lack of a marked decrease in its value with depth, is probably a result of their being exposed to greater current action and circulation of sea water than are those from deeper areas. In addition, the overall rate of sedimentation is likely to be lower in these areas than elsewhere as they will receive the bulk of their detritus from either in-situ weathering of submarine crustal rocks or from the settling of particulate matter from sea water. They are unlikely to be subject to turbidity current action. This slow rate of deposition will enable organic matter to be oxidised before burial.

The lower Eh of the sediments from the deeper areas is probably also a function of environment. Its sharp decrease in core 5937 can probably be related to a high rate of sediment deposition and the inadequate oxidation of organic material, this core being collected near the foot of the continental slope.where sedimentation, and especially turbidity current deposition, is likely to be high. In a similar manner the low Eh of the sediments from Peake Deep and its rapid fail-off with increasing depth in the sediment, may result from a slightly restrict- ed circulation in this area relative to that in the more 278 elevated areas; and from rapid sedimentation, the deep receiving turbidites from the adjacent' Palmer's Ridge.

The significance of these findings in terms of the marine geochemistry of manganese and -manganese nodule formation will not become apparent until manganese determinations on the cores have been conducted. How- ever, two points are worth mentioning at this stage. Firstly, the Eh in some of the cores is lower than that at which quadrivalent manganese is stable. This may mean that any quadrivalent manganese present in these sediments in the past has been mobilised and has migrated upwards in a similar manner to that found in the Mexican continental borderland by Lynn and Bonatti(1965). The change in colour of some cores from brown to grey-green with increasing depth is significant in this context.

Secondly, the generally higher Eh of sediments from the seamounts and ridges than of those from the abyssal plains and deeps would accord with the suggested precipitation of trivalent cobalt under oxidising conditions in nodules on seamounts.

Future geochemical and sedimentological analysis of these cores will enable any variations in their nature, and particually in their content of ferrides, to be examined in the light of the pH and Eh variations found. 279

DISCUSSION

From the information presented in this work it is apparent that the factors affecting the composition of manganese nodules are largely different from those affecting the composition of their associated sediments. These latter are considered to be largely related to the nature of the phases of which the sediment is composed.

Sediments, consisting of phases from different sources and of differing compositions will be compositionally dependent on the relative proportions of these phases in the deposit as a whole. In particular, factors such as their provenance and the organic productivity in the overlying sea water will significantly affect their composition. By contrast, the nodules, consisting of hydrogenous , phases precipitated from solution, will not be so compositionally dependent on factors such as these, but will depend more, for example, on the chemistry of the sea water from which they are precipitated.

Factors affecting the composition of manganese nodules are numerous. Important considerations are the nature of 280

of the source of the elements they contain and the chemical behaviour of these elements in the marine environment.

The sources of elements in manganese nodules have been discussed in section 5.11 and it was concluded that both continental and local volcanic sources are important. Indeed, the observations of Goldberg and Arrhenius (1958) and Chester and Hughes(1966) that the bulk of the manganese on the sea floor is present in the form of secondary phases indicates that manganese from any source is a.potential constituent of manganese nodules. There- fore, the problem is not to establish a single source for the elements in nodules but to differentiate between nodules containing elements from different sources.

It is not easy to decide which of the possible sources is most important in any particular area. In general, it would be expected that continental sources are of greatest importance near the continents and volcanic sources in the vicinity of volcanic areas. In this context the observation that buried nodules are quantitatively more abundant in the volcanically active central oceanicareas than in areas close to land, is of significance. If, as it has been• suggested, some of these nodules faum within the sediment, the source of the elements they contain prob.-ply lies within the sediment also. Certainly, it is unlikely that elements in solution in the overlying sea water would be precipitated several metres below the sediment surface. more likely source is the sediment itself. This, in volcanic areas, consists largely of partially weathered volcanic materials, which on further breakdown could supply 281 the elements required for nodule formation. If this is the case, an abundance of buried nodules in volcanic areas could be taken as an indication of a volcanic source for the elements they contain.

One way of distinguishing between nodules formed by precipitation of elements derived from the continents and those formed by precipitation of elements from local volcanic sources, has been discussed by Arrhenius et al (1964). These authors used the abundance of Co in nodules as an indication of their ultimate origin. They considered that a high content of Co in nodules was a result of their rapid precipitation from volcanic solutions under low redox conditions. By contrast, a low content of Co in nodules was considered to result from the slow precipitation, under more oxidising conditions, of elements derived in solution from the continents. As supporting evidence for this hypothesis they noted that nodules from volcanic areas in the Central Pacific are higher in Co than those found close to the continents.

The validity of this hypothesis depends on the oxid7 ation behaviour of Co in the marine environnent. Indeed, the question as to whether Co does become enriched in nodules under low redox conditions is of prime importance.

It has been shown in section 5.4 that Co is more enriched in nodules containing birnessite than in those rich in todorokite and there is some evidence tc suggest that birnessite is more highly oxidised than todorokite. 282

Further, based on the thermodynamic calculations of Burns (1965) concerning the oxidation of Co in sea water, it was concluded that Co is enriched in nodules only under the highly oxidising conditions required to oxidise it to the trivalent state (section 5.5).

These observations suggest that an abundance of Co in nodules cannot be taken as an indication of exhalative vulcanism and attendant low redox conditions. However, they do not imply that Co could not be derived from the weathering of submarine lavas. The observation of Burns (1965)that an additional supply of Co is required to supplement its content in sea water before oxidation of Co2+ to Co3+ will proceed, suggests that where Co is strongly enriched in nodules a local source of this element is available. If this is so it is to be expected that other elements in the nodules will have also originated from this same source.

Thus, in general, the enrichment of Co in nodules from volcanic areas suggests submarine vulcanism has played a part in the formation of these nodules.

There are certain similarities between regional variations in the composition of manganese nodules and those found locally in areas such as the King's Trough in the North Atlantic and the Carlsberg Ridge in the Indian Ocean. In both cases the elements Ni, Cu and Co vary considerably.

The regional variation in the content of these elements can be related to regional variations in the depth 283 and the bottom topography of the oceans. Likewise, the local variations in the North Atlantic and on the Carlsberg Ridge could result from variations in topography also, although in the latter, local volcanic sources of elements are possibly of importance. Thus it is possible that both local and regional compositional variations in nodules are the result of the same factors.

If this is the case,it is to be expected that where local topographic variations occur within areas containing nodules of similar composition, local variations in the composition of the nodules will occur. This proves to be the case in certain areas.

Nodules taken from less than average depths in basin areas sometimes contain concentrations of Ni, Cu and Co approaching those found, in areas of elevated volcanic topography. For example, sample Proa 161 from the West Central Pacific was taken in 2708 metres of water. The average depth of nodules taken from the West Central Pacific is 5024 metres. Sample Proa 161 contains more Co and less Ni and Cu than the average for the area and approaches in composition the Co rich nodules found in the Mid- Pacific Mountains to the north. Indeed, it can be regarded as being transitional in composition between the `':Test Central Pacific nodules and those from the lad-Pacific Mountains.

In a similar manner nodules taken from basin areas within a region of generally elevated topography are often similar in composition to those found in the deeper regions of the oceans. 284

For example, nodules from the West Indian Ocean, predominantly an area of elevated topography, have an average depth of deposition of 3722m. and contain Co in excess of Ni and Cu. However, sample BM96626F collected in a basin in the northern part of the area in 4793 metres of watery contains high Ni, low Co,and approaches in composition the average for nodules taken from areas of greater average depth. Similar examples are seen in the Central South Pacific. This is an area of variable topography containing numerous seamounts and volcanic mountain areas but with intervening deep basins.. The nodules from the seamounts are rich in Co and Pb while those from the basins are poorer in their elements but richer in Ni and Cu.

It is apparent from this information that within regions containing nodules of an overall similar composition, compositional variations with depth occur on a local scale, just as they. do on a regional scale. It is to be expected, therefore, that with closer sampling in areas of variable bottom topography, many more local variations in the composition of manganese nodules will be found. 285

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APPENDIX 1

ANALYTICAL TECHNIQUES 294

INTRODUCTION The analytical techniques used in this work include both instrumental and wet chemical methods. In the case of the manganese nodules, manganese and iron have been determined by titrimetic,colorimetric and X-ray fluoresence spectrographic methods. The elements, nickel, copper, cobalt, lead,molybdenum, vanadium, chromium, barium, titanium and in a limited number of samples, silicon, have been determined by emission spectrography, and in the case of nickel and copper by colorimetric methods also. In the sediments all constituents have been determined spectrographically except the carbonate content and phosphorus which have been determined titrimetrically and colon. imetrically respectively.

SAMPLE PREPARATION The preparation of the samples for analysis varied dependent upon their nature. Most nodules were obtained from sediment cores and had to be thoroughly washed to remove adhering clay particles. This was accomplished with deionised water, after which they were left to dry overnight. They were then crushed to sand size using a porcelain pestle and mortar and ground by hand to pass an 80 mesh sieve using an agate pestle and mortar. To minimise salting between samples both pestles and mortars were thoroughly washed with concentrated HC1, deionised water and acetone between each operation. At all stages of the procedure care was taken to minimise loss of the finest fraction of the samples as dust to the atmosphere. 295

The larger samples obtained from dredge hauls required little treatment prior to crushing. They were sectioned with a hacksaw blade, analysis of which showed that contamination would result in a dilution of all elements except iron and chromiumt (table 1). Mn 0.4 Pb 0.0005 Ni 0.06 Mo 0.004 V 0.001 Cu 0.06 Co 0.04 Cr 0.015

Table 1: Analysis of hacksaw blade (in weight percent).

After sectioning, the portions of nodules were treated in the same way as above. The final powders were stored in glass bottles.

Sediment samples taken from cores were dried overnight in a drying oven at 110°C after which they were hand grotnd to pass an 80 mesh sieve in the same manner as the nodules; they were also stored in glass bottles.

INSTRUMENTAL METHODS Optical Spectrography i) Nodules The spectrographic methoohthat have been used in this work are a modification of those in current use in the 296

A.G.R.G. for soil and sediment analysis, (Nichol and Henderson-Hamilton 1965).

Prior to analysis the samples were placed in a furnace at 850°C for ten minutes, the loss on ignition being recorded. The removal of volatiles from the samples prevented spitting into the arc during analysis thus giving a smoother burn than that for the unignited samples.

One hundred milligrammes of the ignited sample were mixed with an equal weight of buffer containing 50 percent NaC1 and 50 percent carbon with 800 ppm. Pd added as an internal standard. This mixture was shaken in a Wig- L-Bug for sixty seconds. Approximately forty milligrammes of the mix were then placed in a carbon electrode of outer diameter 4.6 mm., innner diameter 2.95 mm., and depth 5.6 mm., which served as the anode; a pointed carbon electrode served as the cathode. The samples were arced for twenty seconcbat seven amps. and the spectra recorded on Ilford No.30 plates.

In order to arrive at this method various experiments were conducted with differing operating conditions, the variables including the length of the burn, the arc current and the composition of the buffer. Arcing the samples at seven amps. for twenty seconds was found to give the required sensitivity for all the lines used and gave a good line to background ratio. The. choice of the buffer was based on the reduction of possible matrix effects caused by variations in the Fe/Mn ratio of the samples. To this end, equal weights of iron and manganese were added to different portions of the same sample and the intensities. 297 of the minor element lines recorded using various buffers. It was found that the buffer described above gave the close- st agreement between the intensities in the two samples, reducing any matrix effect to within the precision limits of replicate analyses of a single sample.

The operating conditions of the Hilger and Watts large quartz spectrograph were as follows:- Slit .015 mm. Electrode Gap • 3mm. Wavelength Range 2800-4900A

In order to produce a line blackening curve,a three step sector with a cut down of 1:4 was used. The lines were read on all three steps where possible using a Hilger and Watts L90 densitometer. The line intensities read as percent transmission were transformed to a relative intensity level by means of a linear density transforrp scale incorporated into a calculating board developed by Kerbyson (1962). The line intensities were corrected for background and were read against working curves prepared frem spec-pure materials. The following element lines were found to be satisfactory:-

0 Element Line A Pb 2873.3 Cu 2961.1 3273.9 Si 2987.6 Co 2989.5 3453.5 Ba 3071.6 298

0 Element Line A Ni 3099.1 Mo 3170.3 V 3185.4 Ti 3377.6 Cr 4254.3

Pd 3242.7 served as the internal standard line.

A.standard mix was prepared containing Pb, Ni, Cu, Co, Mo, V, Cr, Ti, and Ba. This was diluted by steps with a base containing 53 percent Mh02, 37 percent Fe203 and 10 percent Si02 (Willis and Ahrens 1962). The final range of standards varied from two percent to 1 ppm. In addition, separate standards were prepared for Ni, Co, Cu and Ti, containing 0.66, 1.33 and 1.99 percent of all four elements and 2.66 percent of Ni, Co and Cu mixed in the above base. Thus it was possible to construct good working curves over the ranges of concentration of all these elements in manganese nodules.

Replicate determinations on a number of samples over a period of one year gave a precision range for most elements of approximately 10-15 percent at one standard deviation. The actual precision value for each element is recorded in table 2.

Ti Cu Co Ni Pb V -Ba _ Mo 13.5 15.4 14.7 14.6 15.0 13.1 17.9 11.8 Table 2: Precision of spectrographic analyses (in percent at one standard deviation). 299

Comparison of analyses of samples previously analysed by Willis and Ahrens (1962) with present analyses of the same samples gave reasonable agreement in most cases (table 3.). No. Co Ni Cu Ti Mo V Present author W19 .33 .29 .16 .43 .068 .08 Willis and Ahrens .21 .23 .12 .36 .048 .058 resent author W20 .21 .86 .31 .33 .073 .083 Willis and Ahrens .16 .73 .27 .36 .059 .060 resent author W21 .20 .97 .37 .37 .060 .077 qillis and Ahrens .17 .81 .38 .41 .057 .06 Present author W22 .15 1.10 .39 .34 .061 .087 Willis and Ahrens .15 .95 .40 .36 .054 .06

Table 3: Comparison of present analyses of nodules with those of Willis and Ahrens (1962), (in weight percent).

In addition, colorimetric determinations of Cu.and Ni on samples also analysed spectrographically gave, in most cases, agreement to within the combined precision limits of the methods used, (table 4).

Sample Ni Cu Color. Spec. Color. Spec. 1 1.050 0.750 0.223 0.182 2 0.330 0.369 0.092 0.090 3 1.460 1.370 0.397 0.345 4 0.598 0.555 0.393 0.433 5 0.534 0.475 0.149 0.076 Table 4: Comparison of colorimetric and spectrographic determinations of Ni and Cu(in weight percent). 300 ii) Sediments Sediment analyses for all elements except iron and manganese were conducted using the rapid quantitative method of Nichol and Henderson--Hamilton (1965) in current use in the A.G.R.G. Iron and manganese were determined quantitatively on the same plates using the spectral lines Mn 2933 and Fe 2843.9 with Ge as an internal standard for iron. The international rock standard W.I and a standard red clay supplied by S. Landergren (University of Miami) gave values falling on, or very close to,the working curves prepared from spec-pure materials in an intermediate rock base. The precision of the Fe and Mn determinations was I 10 percent at one standard deviation. Replicate rapid quantitative determinations of the minor elements in the red clay gave values close to the values supplied by Landergren.

X-ray fluorescence spectrography X-ray fluorescence spectrography was used for the determination of iron and manganese in all the samples from area. 4c in the N.W. Indian Ocean. In addition, Rb, Sr, Y, Nb, Zr and Zn were determined on selected samples from this area. Iron and manganese were determined by a quantitative method using Cr as an internal standard.

To 200 milligrammes of sample, about 10 percent by weight of Cr203, weighed accurately, was added, and the mixture thoroughly shaken for twenty minutes in an Agate and General Stonecutters micro-ball mill. The final powder was compressed as an inset on a cellulose disc in which state it was ready for analysis. 301

Manganese was determined by counting for fifty seconds the Mn K oC 1,2 peak at 2.102/105 A, and chromium for one hundred and twenty seconds on the Cr K p 1,3 peak at 2.085 A. The Mn/Cr ratios obtained were compared with the Mn/Cr ratios of synthetic standards plotted on a working curve and thus the manganese content determined. Iron was determined using manganese as a variable internal standard, iron being counted for fifty seconds on the Fe K cbC 1,2 peak at 1.936/40 A and manganese for the same period on the Mn Kflpeak at 1.910 A. Iron values were obtained in a similar manner to the manganese values. The operating conditions of,the equipment, an A.R.L. Production X-ray Quantometer, were 40 kV, 30 mA with a tungsten target; counting was accomplished with an argon filled gas proportional counter. Replicate determinations on one sample gave a precision of ± 3.4 percent for manganese and - 3.5 percent for iron at one standard deviation.

The elements Rb, Sr, Nb, Zr and Y were determined by the method of Butler and Smith (1962) and zinc by a similar method.

The accuracy of the X.R.F. method can be gauged from a comparison of results obtained on samples analysed both titrimetrically and colorimetrically (table 5.) 302

Sample Mn Fe No. X.R.F. Col. Titri. X.R.F. Col. Titri 1 16.3 16.0 15.8 14.0 14.6 16.4 2 12.9 13.5 11.1 17.6 15.5 16.4 3 25.5 25.4 24.5 7.8 7.2 8.7 4 23.0 22.2 22.3 11.5 8.9 10.8 5 18.5 17.8 15.6 16.4 15.1 19.7

Table 5: Comparison of iron and manganese determinations by X.R.F., volumetric and colorimetric methods (in weight percent). WET ANALYTICAL METHODS

Colorimetric Analysis- The elements Mn, Fe, Cu and Ni were determined by a visual colorimetric procedure (Stanton 1966) on five nodule samples, in an attempt to check the accuracy of the analyses clone by optical spectrography.

The samples were attacked with HC1 in the manner of Riley and Sinhaseni (1958) and the insoluble residue treated in the manner of Stanton et al (1962). The two solutions were combined and made up to constant volume.

Nickel and copper were determined on an aliqwtof this solution after dithizone extraction of the heavy metals, Stanton et al (1962). Manganese and iron were determined in total solution by the permanganate and thioglycollic acid methods respectively (A.G.R.G. Tech.Comm. 36 and 40). Comparison of the colorimetric analyses with those by other methods are given in tables 4 and 5. 303

Phosphorus was determined in the sediments by the vanadate- molybdate method in current use at the A.G.R.G., (A.G.R.G. Tech. Comm. No. 52).

Titrimetic Analysis Manganese and iron were determined titrimetrically in the bulk of the samples. Initially, the sample was digested in hot concentrated HC1 the residue being filter- ed, dried and weighed. The methods used were those of Scott and Furman (1955) pages 567-568 and 473-474.

The calcium carbonate content of the sediment samples was determined by a titrimetric method,(A.G.R.G. Tech.Comm.53). The CO radical was detelwined by treatment 3 with dilute HC1; back titrating the excess with standard sodium hydroxide. Other carbonates present would be attacked by this method but these are believed to be quantitatively unimportant compared with calcium carbonate.

DISCUSSION Of the various techniques available for the analysis of manganese nodules those used in this work were chosen firstly, on the basis of accuracy and precision and secondly, on the time they required to conduct. It is possible in the case of all the elements sought to use very precise analytical methods but where large numbers of samples are involved this obviously becomes impracticable. Alternat- ively, all samples could be analysed by rapid semi- quantitative techniques with, however, a concomitant reduction in precision. In the case of the spectrographic work a position between these two extremes has been taken; 304 a little precision has been sacrificed for the sake of rapidity but not sufficient to affect the interpret- ations drawn from the data.

The precision values recorded in table 2 are average values determined from several samples, individual values varying somewhat dependent on the element concentrations involved. For most elements the precision over the whole concentration range encountered falls close to the average value. This was not the case with cobalt, nickel and copper. These elements have a wide dispersion in manganese nodules and the 'recision varies as the concentration levels change. At values of these elements over 0.2 percent the precision is better than that recorded in table 2 while at lower concentrations it falls below this value. This worsening of precision with decreasing concentration is a direct response to the decreasing line to background ratio as the detection limits of the lines used are approached. More sensitive lines could not be used for these elements with the equipment available as the concentration levels were too high or the lines suffered from iron or manganese interference. From the interpretive point of view this worsening of precision with low concentrations of Ni, Cu and Co is not considered important as variations at low concentrations are not considered significant unless gross (see element distribution maps in. Part 2 of this work). When, as occasionally happen- ed, the concentration of these elements fell to a few hundred ppm., the most sensitive lines could be used and a good precision was obtained. 305

The different methods used for the determination of iron and manganese gave closely similar results. The colorimetric procedure is liable to larger errors than the other two for any error in the visual colour matching is greatly exagerated by the large dilutionsthat are required in order to bring the concentrations down to levels where the colours can be matched. The X.R.F. method is both rapid and precise but could suffer from matrix effects, although the presence of an internal standard would largely compensate for these. The volumetric method although being rather time consuming has much to recommend it in terms of accuracy and precision. In addition, the HC1 insoluble residue can be used as a measure of the detrital content of the nodules thus, for comparative purposes, enabling all the analyses to be recalculated on a detrital free basis. Accordingly, this was the method used for the bulk of the samples.

Errors in the analyses could accrue from a number of sources. However, these have been limited as far as possible. Matrix effects in the spectrographic analyses have been suppressed to within the precision limits of replicate determinations on single samples by use of the buffer mix. Likewise, matrix effects on sediments caused by increasing carbonate or silica content in globigerina and radiolarian oozes have been largely suppressed by the buffer (Nichol and Henderson-Hamilton 1965). useoftheLiC03 The volumetric determinations suffer from little error, their precision being in the order of one to two percent. 306

REFERENCES

A.G.R.G. Technical communication No.36 (1965) Determin- ation of manganese in soil and sediment samples. A.G.R.G. Technical communication No.40 (1965) Determin- ation of iron in soil and sediment samples. A.G.R.G. Technical communication No.52 (1966) Determin- ation of phosphorus in soil, sediment and rock samples. A.G.R.G. Technical communication No.53 (1966) Determin- ation of carbonate in soil samples. Butler J.R. and Smith A.Z.(1962) Zirconium,niobium and certain other trace elements in some alkali igneous rocks. Geochim. et Cosmochim. Acta 26, 945-953. Kerbyson J.D. (1963) A calculating board incorporating a linear density transform. Spectrochim.hcta 19, 1335-1341. Nichol I. and Henderson-Hamilton J.C. (1964) A rapid quantitative spectrographic method for the analysis of rocks, soils and stream sediments. Trans. Inst. Min. Met. 74, Part 15 955-961. Riley J.P. and S&nhaseni P. (1958) Chemical composition of three manganese nodules from the Pacific Ocean. J.Mar.Res. 17, 466-482. Scott W.W and Furman N.H. (1955) Standard Methods in Chemical Analysis 1 (5th Ed). D. Van Nostrand, New Jersey. Stanton R.E. (1966) Rapid Methods of Trace Analysis 96pp. Edward Arnold, London. 307

Stanton R.E., McDonald Alison J. and Carmichael I. (1962). The determination of some trace elements in silicate rocks. Analyst, Lond. 87, No. 1031 134-139. Willis J.P. and Ahrens L.H. (1962) Solve investigations on the composition of manganese nodules, with particular reference to certain trace elements.. Geochim. et Cosmochim. Acta 26, 751-764. 308

APPENDIX 2

ANALYTICAL RESULTS 309

Explanation of abbreviations used in Appendix 2 and in Figs.l.l and 1.2

1) The samples are designated by an expedition name and station number: thus Chal. 160, for example, indicates that the sample was collected at station 160 of the Challenger Expedition. In addition, letters are placed after the station number in some cases to indicate the nature of the sampling equipment. These are as follows:- G = Gravity core • Piston core PG = Gravity core attached to a piston core. • Camera station V = Heat flow core • Dredge Where no letter follows the station number the nature of the sampling device is given below,

2) The abbreviations of the expedition names are as follows: 310

Appendix Figs. 1.1 Full Name and 1.2

Amp. A S.I.O.Exped.Amphitrite B.M. B.M. British Museum Collections. Cap. C S.I.O. Exped.Cqpricorn. Chal. Ch. Challenger Expedition. DWBG DWBG S.I.O. Exped.Downwind,Ship the Baird, Gravity core. DWBD DWBD As DWBG but collected by dredge. DWHG DWHG As DWBG but aboard R.V. Horizon. DWHD DWHD As DWHG but collected by dredge. Dis. Di Discovery Expeditions. Dodo D S.I.O. Exped.Dodo. Hilo H S.I.O. Exped.Hilo. Fan. F S.I.O. Exped.Fanfare. Jyn. J S.I.O. Exped.Japanyon. LSDA LA ) S.I.O. Exped.Lusiad. LSDH LH ) A. Argo., H. Horizon. Mag.Bay. MB S.I.O. Exped.Magdelena Bay. MV-65-1 MV S.I.O. Exped.MV-65-1. Mid Pac MP S.I.O. Exped.Mid Pac. 311

Appendix Figs.1.1 and Full Name 2 1.2

Msn. M S.I.O. Exped.ivlonsoon. Proa P S.I.O. Exped.Proa. Ris. R S.I.O. Exped. Rispac. S.O.B. S S.I.O. Exped. Southern Borderland. Tet. T S.I.O. Exped. Tethys. Vit.. V R.V. Vityaz. Wah. W S.I.O. Exped.Waheni. 312

Expd. Amp Amp Amp Amp Amp No.. 3P 9D 8oG 8oG 8oG Pos. top Dredge tDp 87-89 91-94 Lat. 15°041N 22°35tS 11°511S 11°511S 11°5115 Hoag. 125°05!W 150°55'W 160°51'W 160°51'W 160°511W Depth(m) 4500 807 3803 3803 3803 Asc. Brawn Corals Calc Cale Calc Sed. Clay Ooze Ooze Ooze Size (cm) 5x3x3 2x2x2 1x1x1 2x2x1 2x2x1 1 1 Section 3 2 12 1

Mn 23.19 16.07 16.90 15.72 16.57 Fe 5.95 11.80 18-00 18.12 17.79 Ni 1.911 0.011 0.302 0.242 0.226 Co 0.232 2.570 0.512 0.655 0.590 Cu 1.236 0.046 0.172 0.162 0.217 Pb 0.030 0.514 0.029 0.034 0.049 Ba 0.397 0.590 0.111 0.044 0.132 Mo 0.046 0.040 0.027 0.024 0.021 V 0.046 0.069 0.042 0.038 0.042 Cr 0.0013 <0.0002 0.0005 0.0004 0.0007 Ti 0.359 1.286 0.793 0.812 0.960 L.O.I. 25.31 37.22 29.80 28.77 28.84 313

mod. Amp Amp Amp Amp Amp No. 84G 85P 86GV 100G 116PG Pos. top 190-195 top 37-41 Cat Lat. 11°40'S 11°351S 11°25'S 3°40tS 11°26tS Long. 159016171 15e31111 157°371w 156°37'W 149°17114 Depth(m) 5146 5338 5302 5115 5106 Asc. Zeolitic Choc Choc Caic Choc Sed. Clay Clay Clay Ooze Clay Size(cm) 1x1x1 3x2x2 2x2x1 2x2x1 2x2x2 1 1 1 Section 1 2 2 7, 1

Mn 15.39 14.81 17.34 14.02 18.07 Fe 15.40 14.45 12.14 8°74 15.50 Ni 0.977 0.263 0.685 1.003 0.795 Co 0.544 0.730 0.301 0.178 0.650 Cu 0.432 0.182 0.392 1.053 0.318 Pb 0.0050 0.027 0.069 0.057 0.036 Ba 0.124 0.226 0.084 0.112 0.289 Iio 0.040 0.038 0.030 0.027 0.058 V n.d 0.061 0.032 0.034 0.054 Cr 0.0015 0.0008 0.0012 0.0032 0.0008 Ti 1.120 1.240 0.698 0.554 1.336 L.O.I. 19.94 27.04 24.69 17.35 27.76 314

Expd. Amp Amp B.M Cap Chat No. 124C 125PG 96626(20) 24HG 160 Pos. 14-18 top dredge top dredge Tot. 11°5915 11°591S 6°55'N 16° 44'S 42°42'S Long. 144°221W 144°221W 67°11 1E 161°221W 134°101 E Depth(m) 4970 4972 4793 4685 4760 Asc. Red Choc n.d Choc Red Sed. Clay Clay Clay Clay Size(cm) 22.5x1 2x2x1 2x2x2 1x1x-,3; 2x2x2

1 71 1_ 1. 1 Section. 2 2 2 2

iIn 15.33 19.89 17.25 16.27 20.19 Fe 12•86 9.76 13.27 26.32 8.84 Ni 0.440 0.835 0.814 0.220 1.318 Co 0.2:i8 0.118 0.064 0.432 0.199 Cu 0.417 0.771 0,264 0.178 0.750 Pb 0.028 0.014 0.052 0.056 0.025 Ba 0.155 0.165 0.111 0.126 0.356 No 0.036 0.038 0.035 0.015 0.056 V 0.041 0.040 0.051 0.068 0.050 Cr 0.0012 0.0019 0.0015 0.0057 0.0016 Ti 0.835 0.480 0.0232 2.651 0.478 L.O.I. 24.07 21.24 27.63 24.23 25.74 315

&pd. Chal. Chal, Chal. Mal. Dis. No. 289 297 297 297 , 5133.11 Pos. Dredge Dredge Dredge Dredge Dredge 39o41is Lat. 37°29'S 37°29'S 37°291S 2°45.4'N ° Long. 131°2344. 83°7'W 83°7'W 83 7'W 60°02.81S Depth(m) 4665 3245 3245 3245 3858 Asc. Red Glob Glob Glob Cale Sed. Clay Ooze Ooze Ooze Ooze Size (cm) 2x2x1 2x2x1 2x2x1 2x2x1 .5x.5x.5 Section 1z 1z 1z 1z 1

Yin 16.6a 18.51 15.36 16.27 19.95 Fe 10.36 12.34 13'44 15.02 9.55 Ni 0.820 0.686 0.800 0.582 1.119 Co 0.177 0.080 0.156 0.159 0.177 Cu 0.296 0.335 6.226 0.193 0.178 Pb 0.146 0.019 0.014 0.015 0.037 Ba 0.191 0'175 0.086 0.162 0.284 Mo 0.042 0.024 0.023 0.026 0.047 V 0.010 0.028 0.034 0.044 0.050 Cr 0.0002 0.00/0 0.0006 0.0005 0.0005 Ti 0.730 0.234 0.350 0.447 0.335 L.O.I. 30043 27.02 29.16 32.30 28.72 316

Expd. Dis Dis Dis Dis Dis No. 5133.11 5133.11 5133.7 5136.11 5136.11 Pos. Dredge Dredge Dredge Dredge Dredge Lat. 2°45.4'N 2°45-41 N 2°45.4'N 2°46.61 N 2°46.6'N Long. 60°02.81E 60002.81E 6b°02ALE 59°52.8TE 59°52.8TE Depth(c) 3858 3858 3858 3374 3374 Asc. Cale Cale Cale Cale Cale Sed. Ooze Ooze- Ooze Ooze Ooze • Size(cm) s5x•5x.5 •5x•5x•5 6x6x6 •5x•5x•5 Section 1 1 x Sect. 1 1

Nn 19.99 25.80 16.45 14.36 15.36 Fe 8.25 7.79 13.95 14.36 13.03 Ni 1.270 1.420 0.833 0.251 0.194 Co 0.150 0.086 0.186 0.487 0.531 Cu 0.149 0.276 0.131 0.028 0.031 Pb 0.022 0.027 0.021 0.021 0.074 Ba 0.100 0.087 0.381 0.070 0.155 ho 0.029 0.050 0.046 0.035 0.057 V 0.038 0.049 0.0083 0..047 0.067 Cr 0.0005 0.0006 0.0005 <0•0005 <0.0005 Ti 0.187 0.179 0.210 0.755 0.940 L.O.I. 30.59 30.99 30.58 37.55 35.17

Zn 0.105 0.049 Sr 0.044 0.080 Zr 0.067 0.029 Y 0.0072 0.013 317

Expd. Dis Dis Dis • Dis Dis No. 5136.11 5136.7 5138.304 5138.30 5138.4 Pos. Dredge Dredge Dredge Dredge Dredge Lat. 2°46.61 N 2°46.61 N 2°47.91 N 2°47.91 N 2°47.91 N Long. 59°52•g'E 59°52.8'E 59°52.1TE 59°52.1TE 59°52.1TE Depth(m) 3374 3374 3246 3246 3246 Asc. Cale Calc Cale Calc Cale Sed. Ooze Ooze Ooze Ooze Ooze Size(cm) .5x•5x•5 Crust 10x6x6 9x7x6 10x7x7 Section. 1 Frag. x Sect. 1 1

Mn 13082 15.50 12.83 14'45 13.33 Fe 14.21 20.63 17.54 19.51 18.02 Ni 0.268 o.075 0.238 0.227 0.293 co 0.655 0.448 0.240 0.249 0.278 Cu 0.020 0.036 0.073 0.134 0.161 Pb 0.029 0.103 0.023 0'041 0.024 Ba 0.122 0.177 0.16o o.199 0.216 Rio o.o57 0.035 0.032 0'021 0.024 V 0.069 0.075 0'099 0.092 0.091 Cr 4( -'0.0005 0.0009 0.0022 0'0013 0'0023 Ti _ 1.110 1.170 0.790 0•$24 0.805 L.O.I. 34'5 26.54 27.50 27.71 26.74

Zn o;o6o Sr 0.081 Zr 0.057 0'012 318

Expd. Dis Dis Dis Dis Dis No. 5138.8 5138.7 5179.1 5106.12 5123.3 Pos. Dredge Dredge Dredge Dredge Dredge 5034.01N Lat.. 2°47.91 N 2°47.91 N 2°07.91,1. 5°36.31 N Long. 59°52t1 1 E 59°52.1 1E 57°24•51 E 61053'4'E 61°51.51 E Depth(m) 3246 3246 4133 2176 2331 Asc. Calc Calc Calc n.d n.d Sod. Ooze Ooze Ooze Size(cm) 12x5x6 7x7x6 Crust Crust Crust Section. 1 1 Frag. Frag. Frag.

En 12.90 12.51 18.41 13.82 16.59 Fe 17.39 16.91 16.35 19.78 22.48 Ni 0.327 0.376 0.471 0.282 0.250 Co 0,338 0,326 0.810 0.414 0.260 Cu 0'060 0.132 0'053 0.029 0.048 Pb 0.018 0.020 0.081 0.061 0.019 Ba 0.285 0.231 0.139 0.175 0.165 Mo 01053 0.027 0.028 0.042 0.043 V 0'115 0.111 0.086 0.069 0.067 Cr 0.0016 0.0019 0.0014 0.0018 0.0016 Ti 0.670 0.966 1.760 0.687 0.500 L.O.I. 27.81 28.92 26.34 25.32 22.99

Zn 0.047 Os081 Zr 0.052 0.014 319

Expd. Dis. Dis. DWBD DVJBD DWHD No. 5175.1 5175.2 1 4 15 Pos. Dredge Dredge Dredge Dredge Dredge Lat. 2°06.3'S 2°06.3'S 21°2 IN Tuamotu 15°23'S Long. 57°22.9fE 57°22.9'E 126°43vg a5carplent 136°1871W Depth(m) 4041 4041 4300 694 4480 Asc. nd nd nd Calc Frag nd Sed. Size(cm) Crust Crust 3x3x3 Crust Crust 1 1 Section Frag Frag 2 Frag

Mn 15.41 14.53 16.92 21.24 21.49 Fe 17.89 19.10 12.91 10.80 8.14 Ni 0.341 0.317 0.350 0.350 1.288 Co 0.591 0.350 0.342 2.527 0.070 Cu 0.078 0.055 0.203 0.065 0.744 Pb 0.036 0.137 0.143 0.394 0.016 Ba 0.144 0.177 0.556 1.580 0.132 Mo 0.035 0.029 0.057 0.058 0.040 V 0.059 0.084 0.048 0.065 0.027 Cr 0.0020 0.0021 0.0005 < 0.0002 0.0005 Ti 0.908 1.292 0.963 1.160 0.207 L.O.I. 24.28 26.15 28.63 35.19 44.00 320

xpd. DWHD D!HD DWBG DWBG DWBG No.. 16 47 7 18 46 Pos. Dredge Dredge top top top Lat. 16°29'S 42591S 8°48IN 13°37'S 36°23'S Long. 145°33111 102°01'W 130°48vg 135°31'W 137°15fW Depth(m) 1270 4200 4917 4337 4680 Asc. Corals nd Brown Choc Red Sed. Clay Clay- Clay Size(cm) 3x3x3 2x2x2 lxlx2 lx1x45 3x1.5x1 1 1 1 1 Section 2 2 iln 16.90 15.25 24.56 23.82 16.81 Fe 11.27 13.50 4.36 11.65 13.13 Ni 0.620 0.580 1.515 1.798 0.966 Co 1.800 0.106 0.120 0.124 0.430 Cu 0.086 0.212 1.227 0.906 0.347 Pb 0.465 n.d. 0.0097 0.027 0.026 Ba 0.579 0.205 0.536 0.337 0.194 mo 0.059 0.030 0.036 0.049 0.051 V 0.065 0.042 0.043 0.045 0.058 Cr < 0.0002 0.0010 0.0009 0.0009 0.0022 Ti 1.140 0'517 0'179 0'509 1'470 L.0.I. 36.66 29.21 22.28 25.07 24.53

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Expd Dodo Dodo Dodo Dodo Dodo No. 27P 60P 62D 66D 75D Pos . Cat top Dredge Dredge Dredge Lat. 9°40'N 16°17/S 16°18 IS 19°5615 13°1515 Long. 169°00"1 10e30/E 104°161 E 100°00!E 93°121 E Depth(t) 5170 5918 5660 5860 5325 Asc ; n.d Clay Clay Clay n.d Sed. Size ( cm) 3x2x1 2x1x1 9x9x7 3x3x2 Crust

Section. 1 2 x Sect. Frag,

Nn 16-51 14.55 18.46 16.51 15 ..39 Fe 16-.73 13-.06 10.93 9-•11 10-.49 Ni 0.335 0.469 0.380 0.755 06 571 Co 0..274 0.153 0.325 0.196 0.123 Cu 0.498 1.055 0.241 0.531 0.829 Pb 0.045 0.031 0.032 0.070 0.053 Ba 0.314 0.160 0.227 0.136 0.173 Mo 0.037 0.025 0.042 0.052 0.02$ V 0.061 0.031 0.072 0'036 0.043 Cr 0.0008 0.0012 0.0015 0.0009 0.0012 Ti 1.388 0.500 0.497 0.356 0.633 L.O.I. 19.35 21.78 26.87 30.12 22 '85 323

Expd. Dodo Dodo Dodo Dodo Dodo No. 840 110P 113D 125D 127D Pos. Cat top Dredge Dredge Dredge Lat.. 15051 15 21°31 1S 23°16IS 9°391S 6°401S Long. 85°18IE 78°01IE 7059t E 56°25IE 51°541 E Depth(m) 4750 4610 4520 2800 2900 Asc. n.d Clay n.d n.d n.d Sed. Size(m) Frag 2x2x2 Crust Crust Crust 1 1 Section 2 7 Frag Frag Frag

Nn 18-96 18..27 13.20 15.25 13.49 Fe 17.92 16.44 16.00 13.55 15.64 Ni 0.290 0•538 0.409 0.393 0.342 Co 0.224 0.209 0.207 0'998 0.882 Cu 0.108 0.176 0.190 0.073 0,047 Pb 0'105 0'083 0.025 0.255 0'253 Ba 0-163 0.142 0.194 0.399 0'221 Mo 6'023 o•033 0'022 0'047 0.047 V 0'045 0.036 0'039 0.074 0.065 Cr 0'0003 0.0010 0.0014 0'0005 0'0013 Ti 0!.733 0.560 0.568 ii-404 1•138 L.O.I. 36e20 25027 30'71 37•60 36•74 324

Expd. Dodo Dodo Dodo Dodo Fan No. 130G 132F 132P 232D BD20 Pos. top top 10-15 Dredge Dredge Lat.. 26°56'S 31°02'S 31°021S 5o2315 40°151 N Long. 61°491E 64°52tE 64°52TE 97°29'E 128°27111 Depth(m) 4700 405 405 3558 4500 Asc. Calc Clay Clay n.d n.d Sed. Ooze Size(cm) 2x2x2 2x2x1 3x2x1 Crust 7x4x1 1 1 1 1 Section. 2 2 2 Frag 2

Mn 9,48 13:27 12.36 14:20 11:76 Fe 18.30 16.07 15.97 15.76 10.12 Ni 0.136 0.485 0.219 0.545 0.1,111 Co 0.428 0.447 0.328 0.149 0.096 Cu 0.132 0.219 0.088 0.342 0.369 Pb 0.140 0.125 0.152 0.025 0.020 Ba 0.060 0.071 0.065 0.154 0.289 Mo 0.015 0.027 0.015 0.023 0.026 lir 0.047 0.041 0.048 0.053 0.039 C,r 0.0017 0.0014 0.0013 0.0007 0.0072 Ti 1.069 0.948 1.118 0,447 0.393 L.O.I. 26.27 24.18 21.81 30.14 19.78 325

Expd. Hilo Hilo Jyn II Jyn TIT Jyn IV No. 4G 5G 8G 11G 11G Pos . top top 62-65 top top Lat. 22°57 t N 22°571 N 40°21 t N 27°421 N 27°42 ! N Long. 143°58IW 143°5811"1 172°33tE 175°101E 175°10 i E Depth (n) 4750 4850 4250 5750 5750 Asc . Clay Clay Brown Red Red Sed . Mad - Clay • Clay Size (cm) 0.5x0.5c0.5 1x ..5x.5 1.5c1.5x1.5 Frag • 5x. 5x1 1 1 1 1 :L. Section. 2 2 2 2

-An 10.67 10.81 10.24 18066 20.20 Fe 8.19 9.31 11.27 12.88 13.87 Ni 0.835 0.867 0.301 0.900 0.805 Co 0.225 0.162 0.071 0.397 0.264 Cu 0.559 0.530 0.168 0.420 0.523 Pb 0.060 0.075 0.0073 0.046 0.023 Be. 0.061 0.398 0.158 0.255 0.211 Mb 0.035 0.022 0.0093 0.063 0.027 V 0.034 0.044 0.028 0.054 0.036 Cr 0.0020 0.0011 0.0025 0.0013 0.0005 Ti . 0.371 1.108 0.642 1.270 0.823 L.O.I. 38.05 19.69 20.78 25.07 28.41 326

Expd. Jyn V Jyn V Jyn V Jyn V Jyn V No. 15PG 17G 29G 31PG 48PG Pos. top 8-10 top top top Lat.. 8°021 N 6°05IN 13°32'N 11°55'N 15°541 N Long. 149°54111 148°52'11 146°02'W 144°541111 133°57111 Depth(m) 5073 5036 5285 5539 4606 Aso; Red Brown Braun Brown Calc Sed. Clay Clay - Clay Clay Cla • Size(cm) 2x2x.1 1x.5x.5 2x1x1 3x2x1 1x.5x.5 1 1 1 1 Section. 2 2 2 2

Mh 23.63 20.11 18.46 19.45 20.52 Fe 9.34 12.05 n.d 10661 13457 Ni 1.212 0.654 1.026 0.524 0.664 Co 0.257 06202 0.193 0.182 0.325 Cu 0'984 0.436 0,778 0.372 0.198 Pb 0.108 0.020 0.012 0.071 0.130 Ba 0.318 0.169 0.104 0.254 0.295 Mo 0.068 0.028 0.048 0.037 0.046 V 0.043 0.026 0.027 0.042 0.040 Cr 0.0003 0.0007 0.0025 0.0003 0.0005 Ti 0.780 0.566 0.341 0.972 1.260 L.O.I. 24.26 26.51 19.79 24.09 27.81 327

Expd. Jyn V Loch Loch LSDA LSDA No. 50PG Fyne 1 Fyne 2 122G 122G Pos. top Dredge Dredge top 107-108 Lat.. 18°161 N Loch Loch 29°54'S 29°54IS Long. 131°46114 Fyne Fyne 61°531E 61°53IE Depth(m) 5210 -4( 190 ( 190 4400 4400 Asc; Brown Clay Clay Brown Brown Sed.. Clay - Clay Clay Size(cm) 1x.•5x.5 lx1x1 1x1x1 3x2x1 1x1x1 1 1 Section. 1 1 3 1

Tom 24. 28.12 30.02 10.72 11-47 Fe 9°58 5.39 2.24 17-92 20.47 Ni 1.092...---..., 0.0050 0.0100 42 0.193 Co 6.219 0.014 0.026 0.330 Cu 0.745 0.0012 0.0022 0.183 Pb 0.094 < 0.0010 0.0044 0:6100. 11 0.100 Ba 0.175 0.278 n.d 0.151 0.100 Plb 0.052 0.011 0.019 0.019 0.014 V 0.031 0.035 0.057 0.052 0.042 Cr 0.0007 0.0026 0.0040 0.0069 0.0013 Ti . . 0.477 0.226 0.158 1.270 1.149 L.O.I. 23.11 20.64 18.66 25.3 25.83 328

bpd. LSDA LSDA LSDH LSDH LSDH No.. 126G 219D 45G 87P 89PG Pos. top Dredge top top top Lat.. 39°461S 6°03IN 14°07/S 11°301 N 8°08/N Long. 64°001E 32°22114 89°35TE 177°48/E 177°10rg Depth(m) 4980 3280 5255 5520 5435 Asc. Brown Basalt Brawn Brown Brown Sed. Clay Clay Clay- Clay- Size(cm) 2x1x1 Crust 2x1x1 lx1x.5 2x1x.5 i 1 i Section. 2 Frag 2 2 lin 12.51 9.01 11.96 17886 15.78 Fe 8.00 19870 9865 10.50 12881 Ni 0.494 0.139 0.325 1.41 0'545 Co 08113 0.425 0.045 0.388 0.212 Cu 0.239 0.090 0.242 0.888 0..329 Pb 0.006 0.016 0.081 080080 0.025 Ba 0.121 0.171 0.079 0.177 0.065 Mo 0.012 0.029 0.031 0.046 0.028 V 0.017 0.091 0.028 0.037 0.035 Cr 0.011 080027 080022 0.0016 0.0014 Ti 0'921 0.699 0'420 0.8/4)14 0'712 L.0.I. 16'22 30'31 20.75 19.24 24.26 329

Expd. LSDH LSDH LSDH LSDH LSDH No. 90PG 90P 90P 93PG 93PG Pos . top 297-299 343-344 top 57-60 9o49 I N. Lat.. 7019lN 7°19'N 7°19'N 9°49'N Long. 175°281W 175°281W 175°2811 170°59111 170°591W Depth (m) 5190 5190 5190 4875 4875 Asc, Brown Brown Brown Cale Calc Sed. Clay Clay Clay- Ooze Ooze Size(cm) 2x2x1 1x1Y1 1x1x.5 1x1x.5 2x2x1 1 1 1 1 1 Section. 2 2 3 2

1+'1n 17.80 18.95 17.98 20.94 18.16 Fe 14.78 12.86 17.08 13.03 13.33 Ni 0.694 0.825 0.712 0.668 0.860 Co 0.4% 0.558 0.689 0.293 0.496 Cu 0.346 0.802 0.794 0.433 0.693 Pb 0.122 0.013 0.074 0.049 0.056 Ba 0.117 0.195 0.060 0.187 0.160 Ho 0.038 0.032 0.028 0.033 0.039 V 0-049 0.046 0.037 0.036 0.039 Cr < 000002 0.0002 0.0002 0.0004 0.0006 Ti 0.982 0.787 0.530 0.992 0.685 L.O.I. 26.18 23.60 24.29 26.51 27.21 330

bpd. Nag Bay NV-65-1 PV-65-1 Mid Pac Mid Pac No. A35 38 41 25F1 26A3 Pos. Dredge Dredge Dredge Dredge Dredge Lat. 24°231 N 24°241 P? 24o34IN 19°051 N 19°001 N Long, 113°18114 113°16111 113°281W 169°45'W 171°0011q Depth(m) 3550 1950 3510 1777 1464 Asc. Red Red Red n.d n.d Sed. Clay Clay Clay Size(cm) 2x2x2 3x2x2 2x2x1 Crust 2x2x2 Section. 1 1 1 Frag 1

Nn 33.90 33.92 34.1 2 13.38 12.28 Fe 1.69 1.99 1.18 12.72 11.68 Ni 0.111 0.110 0.069 0.436 0.473 Co 0.010 0.0069 0.0055 1.283 1-172 Cu 0.057 0•C86 0.052 0.047 0.059 Pb 0.0057 0.0058 0.0062 0.257 0.073 Ba 0.172 0.188 0.153 0.334 0.229 Uo 0.068 0.078 0.071 0.056 0.048 V 0.030 0.031 0.029 0.057 0.071 Cr 0,0016 0.0023 0.0018 0.0006 0.0028 Ti 0.069 0.064 0.049 1.187 1.538 L.O.I. 23.56 23.05 19.28 35.82 26.72 331

Expd. Aid Pac Aid Pac lad Pac Msn Msn No. 33K 37C 43A 128G 128G Pos. Dredge Dredge Dredge top 13-16 Lat. 17°50!N 17°102 N 13°002 N 13°5325 13°5325 Long. 174°152W 177°10114 165°002E 150°351W 150°352W Depth(m) 1696 2016 1830 3623 3623 Aso; n.d n.d n.d Calc Caic Sed. Sand Sand Size(cm). Crust Crust Crust 2x2x1 3x3x3 1 Sectior . Frag Frag Frag 2

Nn 11.13 14'97 19.40 14'44 17-42 Fe 14'49 13.27 13.53 15.84 17'44 Ni 0.226 0.339 0.518 0'349 0.334 Co 0.885 0.884 1.597 0.504 0.506 Cu 0.075 0.092 0.044 0.223 0.302 Pb 0.191 0.177 0.248 0.029 0.021 Ba 0.150 0'262 0.511 0.108 0.078 rho 0.028 0.037 0.047 0.025 0.029 V 0.044 0.056 0.044 0.043 0.037 Cr 0.0011 0.0036 -4.(.. 0.0002 0.0007 0.0005 Ti 0.820 00871 1'348 0.677 0.457 L.o.i. 31.61 31.95 29.02 27.92 29.71 332

Expd. Proa Proa Proa Proa Proa No. 11PG 79P 101G 105G 105G Pos. top 26-30 top top top Lat.. 6°08?N 4°51 1S 6°02tN 0°15'N 0°15TN Long. 136°11'E 174°01tE 178°351W 179°43'14 179°43'W Depth(m) 4600 495 5097 5045 5045 Asc. Brown Red Zeolitic Calc Calc Sed. Clay Clay Clay. Ooze Ooze. Size(cm) 1x1x1 3x3x2 Frag. 3x3x3 1x1x.5 1-. 1 1 1 Section. 2 2 1 2 2

Drri 14.30 12.67 15.4 15.85 17.14 Fe 17.36 19.30 15.48 15.75 15.85 Ni 0.755 0.379 0.253 0.646 0.653 Co 0.393 0-447 0.381 0.175 0-148 Cu 0.408 0.253 0.178 0.552 0.536 Pb 0.0050 0.019 0.017 0.024 0.027 Ba 0'501 0.067 0.116 0.141 0.093 Ho 0.063 0.029 0.037 0.020 0.025 V 0.077 0.049 0.052 0.034 0.040 Cr 0.0009 0.0005 0.0003 0.0004 0.0006 Ti . . 0.847 o.930 0.536 0.453 0.602 L.O.I. 22.95 25.56 40.40 ',1.30 26.58 333

Expd. Proa Proa Proa Proa Proa No.. 108PG 108P 113PG 113PG 113PG Pos. top 396 Cat Cat Cat 9o314is Lat. 3°31 1S 3°31'S 9°341S 9°34'S Long. 178°2511 178°251W 176°13TW 176°131W 176°13;W Depth (m) 5582 5582 437 4837 4837 Asc. Brown Brown Brown Brown Brown Sed. Clay Clay Clay Clay Clay Size(cm) 2x2x2 3x3x2 2x2x1 1x2x2 1x1x1 1 Section. 2 1 1 1 1

Mn 12.39 16.95 9.56 7.20 11.26 Fe 14.69 14.74 16.55 15.64 17.15 Ni 0.495 0.518 0.237 0.184 0.249 Co 0.334 0.368 0.365 0.252 0.287 Cu 0.388 0.450 0.209 0.163 0.172 Pb 0.024 0.017 0.073 0.111 0.017 Ba 0.109 0.117 0.076 0.058 0.055 Mo 0.035 0.032 0.014 0.0087 0.012 V 0.036 0.057 0.047 0.047 0.042 Cr 0.0003 0.0009 0.0040 0.0065 0.0037 Ti 0.662 0.668 1-632 1.977 1.437 L.O.I. 23.90 2h.94 22.27 22.64 24,35 334

Expd. Proa Proa ProaProa Proa No. 113P 116P 137G 139G 147G Pos. Cat Cat Cat top top Lat. 9o34'5 8°49'3 7°041 N 8°06111 10°301 N Long. 176°1 311 1 68°33 ti,,,t 1 71 °42 '1,1 170°251w 1 65°33 IW Depth (n) 4837 50 5386 5444 Asc, Brown No Rad ffc Sed. Clay Core CoreOoze Ooze Size(cm) 2x2x1 2x2x1 Frag 2x2x1 1x1x1 1 1 Section. 1 1 1 2 2

Mh 11.90 14.78 18.62 20.71 14.18 Fe 16.81 11.14 16.67 8.96 16.38 Ni 0.223 0.539 0.467 1.070 0.662 Co 0.257 0.243 0.511 0.187 0.882 Cu 0.136 0.570 0.210 1.223 0.318 Pb 0.027 0.057 0.023 0.049 0.036 Ba 0.079 0.043 0.189 0.115 0.345 Mo 0.017 0.016 0.045 0.043 0.036 V 0.040 0.032 0.060 0.030 0.054 Cr 0.0006 0.0029 0.0004 0.0005 0.0004 Ti 1.620 1.064 0.931 0.397 1.380 L.O.I. 24.40 22.87 30.00 23.55 23.27 335

Expd. Proa Proa Proa Proa Proa No. 147G 148G 151G 156G 156G Pos. 145-47 top top top 87-89 Lat. 10°301 N 11°01 1 N 8°34'N 10°231 N 10°231 N Long. 165°33111 164°56'W 168°521W 170°57!W 170°571W Depth(m) 4347 4835 4397 4469 4469 Acs. Cale Zeolitic Calc Calc Cale Sed. Ooze Clay Ooze Ooze Ooze Size 2x1x1 1x1x1 1.5x1.5x1 2x2x1 3x2x2 1 1 1 1 Section. 2 1 2 2 3

Mn 14.84 19.23 18.38 17.01 19.18 Fe 14.18 17.08 12.04 14.54 11.98 Ni 0.540 0.603 0.552 0.770 0.620 Co 0.679 0.440 0.440 0.692 0.458 Cu 0.416 0.646 0.447 0.631 0.719 Pb 0.012 0.131 0.048 0.0055 0.092 Da 0.339 0.309 0.239 0.277 0.250 Mo 0.035 0.043 0.036 0.039 0.032 V 0.047 0.050 0.037 0.049 0.037 Cr 0.0003 0.0025 4:: 0.0002 < 0.0002 0.0005 Ti 1.120 1.526 0•686 1.110 0.698 L.O.I. 22.82 29.00 25.38 23.04 24.98 336

Expd. Proa Proa Proa Proa Proa No. 156G 157G 159G 160G 161G Pos. 102-104 top top 87-89 Cat Lat. 10°23'N 10°201 N 11°231 N 11°31 1 N 12°161N Long. 170°571 a 172°0611j 172°471W 172°4911W 172°48114 Depth(m) 4469 5106 5380 4837 2708 Asc. Calc Zeolitic Brom Brown No Sed. Ooze Clay Clay Clay Core Size 0.5x0.50.5 1x1x2 2x1x.5 2x2x2 Frag 1 1 1 1 Section. 2 2 2 2 1

hn 19.97 20.63 17.12 12.20 13.02 Fe 16.24 13.72 14.80 13.14 16.03 Ni 0.936 0.404 0.489 0.552 0.310 co 0.877 0.433 0.430 0.358 0.896 Cu 0.690 0.241 0.270 0.493 < 0.050 Pb 0.053 0.031 0.047 0.028 0.082 Ba 0.085 0.112 0.074 0.078 0.293 Mo 0.035 0.032 0.044 0.019 0.039 V 0.053 0.038 0.039 0.031 0.075 Cr 0.0002 < 0.0002 0.0008 0.0006 0.0004 Ti 0'994 0.944 0.598 0.672 11259: L.O.I. 41.52 29.02 27.07 25.31 32.63 337

Expd. Proa Proa Ris Ris Ris No. 162G 169G 5V 8V 14V Pos. top top Cat Cat Cat Lat. 12°31 1 N 15°361 N 20°191 N 14°261 N 5°201 N Long. 175°51 111 166°40111 117°29qj 117°12111 117°55114 Depth (m) 5464 5440 4010 4125 4330 Asc. Brown No Red Brown Brown Sed. Clay Core Clay Clay Clay Size 1x1x1 Frag 2x1x-5 1x1x1 2x1x1 1 1 1 Section. 1 1 2 2 2

Mn 15.85 16.70 24.13 26.84 30.28 Fe 12.88 16.95 10.46 10.30 7.15 Ni 0.532 0.340 1.258 1.890 1.485 Co 0.721 0.844 0.258 0.083 0.048 Cu 0.433 0.157 0.680 1.064 0.914 Pb 0.0053 0.072 0.019 0.036 0.0087 Ba 0.425 0.154 0.340 0.440 0.381 Mo 0.036 0.043 0.036 0.080 0.027 V 0.054 0.063 0.033 0.040 0.031 Cr 0.0004 0.0009 0.0005 0.0009 <0.0002 Ti 1.380 1.215 0.289 0.343 0.123 L.O.I. 24.06 28.49 32.00 22.83 23.81 338

Expd. Ris Ris Ris S.O.B. S.O.B, No. 45V IIIV IIIPG 10D 13D Pos. Cat Cat top Dredge Dredge Lat. 13°32'S 14°551 N 14°551 N 30°121 N 29°31 1 N Long. 89°051 g 133°29111 133-° '&--2 114 117°38111 117°17:W Depth(m) 4080 4770 4770 1300 540/820 Asc. Clay Red Red Sandstone Basalt Sed. Clay Clay Size 1x1x2 1x1x.5 1x1x.5 Crust Crust 1 1 Section 1 2 Frag Frag

, 23.55 22.97 21.17 14.23 17.25 Fe 10.83 7.11 10.64 15.15 12.77 Ni 1.834 1.266 1.006 0.204 0.221 Co 0.101 0.261 0.295 0.557 0.9-: Cu 0.455 0.775 0.681 0.028 0.029 Pb 0.070 0.020 0.023 0.106 0.311 Ba 0.256 0.372 0.250 0.388 0.423 E.° 0.073 0.044 0.037 0-029 0.075 V 0.047 0.036 0.032 0.054 0067 Cr 0.0003 0.0012 0.0011 0.0049 0.0015 Ti 0.330 0.506 0.515 0.585 0.840 L.O.I. 26.62 20.83 2/1.32 29.50 37.76 339

Expd. S.O.D. S.O.B. S.O.B. Vit Vit No. 20D 25D 27D 5193 5200 Pos. Dredge Dredge Dredge Dredge Dredge 31o231N Lat. 31°05,N 30°181 N 32°481S 23°5215 Long. 118°03t4VI 118°37111q 117°4011d 103°52'E 91°39'E Depth(m) 1040 1650 1060 5300 4560 Asc. n.d Basalt Sandstone n.d n.d Sed. Size Crust Crust Crust 2x2x1 3x3x3 Section. Frag Frag Frag Outer Crust 14 ism 19.40 14.59 14.40 14.51 13.71 Fe 12.92 9e0.2 11.85 12.92 11.39 Ni 0.447 0.481 0.588 0.488 0,329 Co 0.581 0.202 0.567 0.244 0,187 Cu 0.062 0.130 0.039 0.301 0.121 Ph 0.116 0.037 0.031 0.016 0.006 Ba 0.640 0.574 0.442 0.069 0.164. Mo 0.042 0.032 0.034 0.038 0.029 V 0.093 0.052 0.067 0.047 0.039 Cr 0.0046 0.012 0.0086 0.0006 0.0006 Ti 0.529 0.236 0.457 0.488 1 ,000 L.O.I. 25.52 15.53 21.16 28.26 35.50 340

Fxpd. Vit Vit lilah Wah Wah No. 5202 5270 2PG 2P 2P Pos. Dredge Dredge Top Top 255-2% Lat. 20°521S 11°591S 11°51 1 N 11°51 1 N 11°51TN Long. 91°291E 79°051 E 152°56ra 152°56111 152°56111 Depth(m) 4565 5445 5221 5221 5221 Asc, n.d n.d Clay Clay Clay Sed. Size 2x2x2 Small 2x1'xt 2x22 2)C;-'). 1 1 Section. 2 1 2 1 1

Tin 14.53 19.56 15.44 10.96 16.51 Fe 9.80 4.5 11.98 6.92 11e05 Ni 0.530 1.35 0.724 0.539 0.612 Co 0.202 0.058 0.261 0.800 0.461 Cu 0.297 0.772 0.463 0.574 0.461 Pb 0.095 0.0046 0.037 0.038 0.029 Da 0.134 0.212 0.030 0.247 0,1.- Ko 0.026 0.033 0.050 0.020 0.05 V 0.039 0.037 0.040 0.041 0'047 Cr 0.0007 0.0009 0.0010 0•0006 0.0005 Ti 0.742. 0.471 0.687 1.22 0,636 L.O.I. 29.09 22.72 25.29 13.06 2048 341

Expd. IJah Wah Wah Wan Wa.h No. 2P 4PG 4P 24FF-8 24FF-8 Pos, 288-294 top 395 top 16-18 Lat.. 11°51 113 8°571 N 8°571 N 8°201 N 8°20IN Long. 152°56'W 152°52t14 152°52'W 153°00tW 153°00IW Depth(m) 5221 439 4839 5143 5143 ksc. Clay Clay Clay Clay Clay Sed. Size 2x2x3 2x2x2 1x1x.5 2x2x2 Jc3x2 1 1 1 1 1 Section. -,-; 2 2 2 2

1:in. 16.81 22.61 13.04 24.89 25.63 Fe 13.18 10.94 12.67 7.31 6.20 Ni 0.360 1.330 0.525 1.855 1.530 Co 0.438 0.409 0.191 0.253 0.138 Cu 0.356 0.780 0.690 1.646 1.500 Pb 0.130 0.082 0.037 0.042 0.032 Ba 0.519 0.334 0.405 0.317 0.280 No 0.049 0.065 0.020 0.057 0'028 V 0.076 0.056 0.026 0.041 0.023 Cr 0'0007 0.0034 0.0009 0.0017 0.0019 Ti 2.150 1.077 0.367 0.533 0.363 L.O.I. 25.76 25.70 25.00 22.68 21.08 342

Ex-pd. Wah Tet No. 2.4FF-8 27A Pos. 59-60 top Lat. 8°20 tN 13°05 tN Long. 153°0014J 163°10IW Depth (m) 5143 5413 Asc. Clay Rad Sed. Ooze Size 2x1x1 Small

Section. 2

Lin 26.73 17.94 Fe 6.57 8.85 Ni 1.646 0.480 Co 0.173 0.268 Cu 1.204 0.645 Pb 0.034 0.029 Ba 0.221 0.248 Mo 0.030 0.040 V 0.031 0.042 Cr 0.0012 0.0032 Ti . 0.309 0.677 L.0 .I . 19.68 21 •28