C.886

GEOLOGICAL SURVEY CIRCULAR 886

Analysis of the World 

Distribution of Metal-Rich 

Subsea Manganese Nodules
Analysis of the World 

Distribution of Metal-Rich 

Subsea Manganese Nodules

By V. E. McKelvey, Nancy A. Wright, and Roger W. Bowen

GEOLOGICAL SURVEY CIRCULAR 886

1963
United States Department of the Interior

JAMES G. WATT, Secretary

Geological Survey

Dallas L Peck, Director

Library of Congress Cataloging in Publication Data

McKelvey, V. E. (Vincent Ellis), 1916-

Analysis of the world distribution of metal-rich subsea manganese nodules.

(Geological Survey circular ; 886)

Bibliography: p. 53

Supt. of Docs, no.: 119.4/2:886

1. Manganese nodules. I. Wright, Nancy A. II. Bowen, Roger W. III. Title. IV. Series.

QE75.C5 no. 886 557.3 s[553.4'629] 82-600335

[QE390.2.M35]

Free on application to Distribution Branch, Text Products Section, 

U. S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Abstract _____________________________________________ 1

Introduction ___________________________________________ 1

World average metal content of manganese nodules ______________________ 1

Average metal content of nodules in each of the oceans _____________________ 4

World average metal content of nodules in latitudinal zones __________________ 6

Relation of metal content of nodules to water depth _______________________ 7

Relation of nodule concentration to water depth ________________________ 20

Metal-rich types of manganese nodules _____________________________ 21

Targets for exploration _____________________________________ 32

Other elements in manganese nodules ______________________________ 33

Genetic implications of variations in composition of manganese nodules ___________ 41

Relation of metal content to mineralogy ___________________________ 43

Relation to water depth ____________________________________ 45

Effects of direct precipitation from seawater in comparison with diagenetic precipitation _ 46

Relation to regional variations in sediment type, biologic productivity, and physiography _ 48

Summary _____________________________________________ 51

References cited _________________________________________ 53

ILLUSTRATIONS

FIGURE 1. Map showing manganese nodule stations in the Scripps Institution of Oceanography's Sediment Data

Bank as of March 1980 _________________________________________ 3 

2-13. Diagrams showing relations between:

2. Manganese^content in manganese nodules and their latitudes at stations in the Scripps Institution of Oceanography's Sediment Data Bank ___________________ _ _ 10

3. Combined nickel and copper content in manganese nodules and their latitudes at stations in the

Scripps Institution of Oceanography's Sediment Data Bank _________________ 11

4. Depth and combined nickel and copper content in manganese nodules at stations in the Scripps

Institution of Oceanography's Sediment Data Bank _________________ 12

5. Depth and cobalt content in manganese nodules in the Scripps Institution of Oceanography's

Sediment Data Bank ______________________________________ 13

6. Depth and combined nickel and copper in Pacific Ocean manganese nodules at 1,770 stations in

the Scripps Institution of Oceanography's Sediment Data Bank ______ ___ 14

7. Depth and combined nickel and copper content in Atlantic Ocean manganese nodules at 296

stations in the Scripps Institution of Oceanography's Sediment Data Bank ______ _ 15

8. Depth and combined nickel and copper content in Indian Ocean manganese nodules at 300

stations in the Scripps Institution of Oceanography's Sediment Data Bank _____ _ 17

9. Depth and cobalt content in Pacific Ocean manganese nodules at 1,710 stations in the Scripps

Institution of Oceanography's Sediment Data Bank ________________ _ 18

10. Depth and cobalt content in Atlantic Ocean manganese nodules at 285 stations in the Scripps

Institution of Oceanography's Sediment Data Bank ______v_____ _ 19

11. Depth and cobalt content in Indian Ocean manganese nodules at 289 stations in the Scripps

Institution of Oceanography's Sediment Data Bank _________________ 20

12. Depth and manganese content in manganese nodules at stations in the Scripps Institution

of Oceanography's Sediment Data Bank ___________________________ 21

13. Depth and concentration of manganese nodules at stations in the Scripps Institution of Oceanography's Sediment Data Bank ___________________________ _ _ 22

in
Page

14-18. Maps showing distribution of manganese nodules containing:

14. 1.8 percent combined nickel and copper or more _ _ 27

15. 1.0 or more and less than 1.8 percent combined nickel and copper 28

16. 1.0 percent cobalt or more ______ ___ 29

17. 0.5 or more and less than 1.0 percent cobalt ______ _ 30

18. 35.0 percent manganese or more _______ _ 31 

19-21. Maps showing distribution of manganese nodules having high metallic contents in:

19. Pacific Ocean __________________________ 33

20. South Atlantic Ocean _____________ __ 35

21. Indian Ocean _____________ _ 37 

22-28. Maps showing target areas for exploration for manganese nodules rich in combined nickel and copper in:

22. Central northeastern Pacific Ocean __________ 40

23. Central north equatorial Pacific Ocean _ _ 41

24. Southeastern equatorial Pacific Ocean _________ 42

25. Central southeastern Pacific Ocean ______ 43

26. Central South Pacific Ocean _____________________________ 44

27. Central south equatorial Indian Ocean ___ 45

28. Southeastern Indian Ocean ______ _ 46 

29. Ternary plot of principal mineral phases of manganese nodules at 107 stations in the Scripps Institution of Oceanography's Sediment Data Bank for which analyses of all constituents shown have 

been made ________________ 47

TABLES

Page

TABLE 1. World metal contents, nodule concentrations, depths, and metal ratios of manganese nodules _____ 2

2. Comparison of the world average metal contents of manganese nodules listed in table 1 with the values

reported by Cronan (1980) __ ____________________________________ 4

3. Metal contents, concentrations, depths, and metal ratios of manganese nodules in the Pacific, Atlantic,

and Indian Oceans _____________________________________________ 5

4. Average metal contents of manganese nodules, by ocean ________________________ 6

5. Some metal ratios in manganese nodules in comparison with those in the Earth's crust and seawater _ 7 

6, 7. Metal contents, concentrations, depths, and metal ratios of manganese nodules, grouped by latitude, in:

6. Northern hemisphere _________________________________________ 8

7. Southern hemisphere _________________________________________ 9 

8. World average and maximum metal contents of manganese nodules, categorized by latitude _____ 10 

9-11. Average and maximum metal contents of manganese nodules, categorized by latitude in:

9. Pacific Ocean ___________________________________________ 13

10. Atlantic Ocean __________________________________________ 14

11. Indian Ocean ______________________________________________ 15

12. Metal contents, concentrations, depths, and metal ratios of manganese nodules in water depths of less

than 2,000 and more than 4,000 m _________________________________ 16

13. Metal contents of manganese nodules in water depths above and below 3,000 m _____________ 18 

14-16. Metal contents, concentrations, depths, and metal ratios of manganese nodules containing:

14. 1.0 percent combined nickel and copper or more __________________________ 23

15. 1.0 percent combined nickel and copper or more outside the Clarion-Clipperton zone _____ 24

16. More than 0.5 percent cobalt and more than 35 percent manganese _______________ 25 

17-20. Other elements in manganese nodules:

17. Of the world and of the Pacific, Atlantic, and Indian Oceans __________________ 34

18. Means of the world, grouped by latitude _____________________________ 36

19. Means in water depths above and below 3,000 m __________________________ 38

20. Grouped by combined nickel and copper, manganese, and cobalt contents ___________ 39 

21. World means and ocean maximums of several other elements in manganese nodules that have exceptionally high concentrations _____________________________________ 40

IV
Analysis of the World Distribution of Metal-Rich 

Subsea Manganese Nodules

By V. E. McKelvey,1 Nancy A. Wright,2 and Roger W. Bowen

ABSTRACT

Publicly available data on the composition of subsea manganese 

nodules extend previous reports of differences in average metal 

contents from ocean to ocean and of variations related to latitude 

and depth. Pacific Ocean nodules have the highest average 

manganese, nickel, and copper contents, and Atlantic Ocean 

nodules have the highest average iron content. The average 

manganese, nickel, and copper contents generally increase 

toward the equator in both hemispheres, and iron content 

generally decreases. The variation of metal content with water 

depth is not linear; instead, there appears to be a threshold depth 

of about 2,900 to 3,000 m, above which combined nickel and copper contents are generally less than 1 percent and below which 

cobalt content is generally less than about 0.6 percent.

The composition of the nodules varies widely, but three rarely 

overlapping types that are of possible economic interest can be 

recognized. (1) Nodules containing more than about 1 percent 

combined nickel and copper only exceptionally contain more than 

0.5 percent cobalt and 35 percent manganese. (2) Nodules containing more than 0.5 percent cobalt rarely contain more than 1 

percent combined nickel and copper and 35 percent manganese. 

(3) Nodules containing more than 35 percent manganese only exceptionally contain more than 0.5 percent cobalt, although they 

average nearly 1.1 percent combined nickel and copper. Current 

economic interest in nodule mining is focused on the ClarionClipperton zone in the northeastern equatorial Pacific Ocean, the 

largest known area in which nodules average 1.8 percent or more 

combined nickel and copper. Several other areas in which nodules 

are rich in these metals are found in the Pacific and Indian Oceans 

and may be viewed as targets for exploration.

Nearly 60 chemical elements have been found in manganese 

nodules, many in concentrations far exceeding their crustal abundances. The amounts in which many minor elements are present 

vary with the amounts of principal metals present, but the three 

metal types described above do not include the maximum 

reported values for several other elements, such as titanium (8.9 

percent), vanadium (0.5), zinc (9.0), and lead (0.75). It seems possible, therefore, that there may be other kinds of metal-rich types, 

some of which may have potential economic value.

JU.S. Geological Survey, retired.

Many of the variations in nodule composition are in large part 

a function of variations in mineral composition, to which many 

factors contribute. Some of the regional variations can be broadly related to oceanic circulation, basin morphology, and depth, 

but a better understanding of ocean processes and regional 

oceanography and geology is needed to explain all the variations 

observed in the composition of manganese nodules.

INTRODUCTION

Through the good offices of J. Z. Frazer, we have 

entered in the U.S. Geological Survey computer in 

Reston, Va., all data on subsea manganese nodules 

in the Scripps Institution of Oceanography's Sediment Data Bank, which includes all published and 

otherwise publicly available analyses of manganese 

nodules, reported on or converted to a water-free 

basis (for a description of the bank, see Frazer and 

Fisk (1980)), We are thus able to analyze variations 

in nodule composition related to geographic distribution, water depth, and other factors and to 

identify areas in which the metal content of 

available samples is high enough to justify further 

exploration for deposits that might someday be 

suitable for mining. The results reported here 

place principal emphasis on variations in manganese, iron, nickel, copper, and cobalt contents (collectively referred to as the "metal content").

WORLD AVERAGE METAL CONTENT OF 

MANGANESE NODULES

As of March 1980, the Scripps Sediment Data 

Bank contained chemical analyses of nodules from 

2,401 stations. The metal contents, concentrations, depths, and metal ratios from these stations 

are summarized in table 1. Because the stations are 

irregularly distributed (see fig. 1), even world 

averages must be regarded as only approximations. More than 400 stations are located in the
TABLE 1. - World metal contents (in percent), nodule concentrations (in kg/m2), depths (in m), and metal ratios o

[The Clarion-CKpperton zone is.taken to be the area defined by 7° to 15° N., 114° to 153° W. Metal ratios are based on ratios in samples for which both constituents have been de

Would be obtained from the means of individual constituents]

Mn _

Fe_ _ _

Ni_ _ _

Cu _________________ 

Ni+Cu __________________ 

Co _____________________

Concentration _______________ 

Depth _ _ _

Mn/Fe _______________ 

Ni/Mn _________________

Cu/Mn

Cu/Ni

(Ni+Cu)/Mn ____________ 

(Ni+Cu)/Fe __________ 

Co/Mn _ __ _

Co/Fe __________________ 

Co/(Ni+Cu) ___________ 

Depth versus Ni + Cu _________ 

Depth versus Co ____________

No. of 

stations

2,378 

2,374 

2,383 

2,368 

2,366 

2,284 

344 

2,277 

2,370 

2,367 

2,352 

2.366 

2,350 

2,346 

2,267 

2,263 

2,270 

2,242 

2,162

Mean

18.60 

12.47 

.66 

.45 

1.12 

.27 

10.89 

4,270 

2.26 

.036 

.026 

.695 

.062 

.149 

.017 

.025 

.500

All Stations

Range

0.04-50.3 

.30-50.0 

.01-1.95 

.01-1.90 

.02-3.44 

.01-2.23 

.12-70.8 

46 7,280

.002-100.0 

.001-1.00 

.000-6.00 

.031-16.0 

.002-6.43 

.001-7.60 

.000-.429 

.000-1.333 

.005-4.50

Stations outsid

Standard 

deviation

7.20 

5.69 

.44 

.40 

.81 

.19 

10.44 

1,240 

3.84 

.034 

.126 

.721 

.144 

.250 

.016 

.034 

.507

Correlation 

coefficient

-0.44 

.75 

.65 

.89 

.72 

-.68 

.16 

.30 

-.18 

.30 

-.35

No. of 

stations

1,979 

1,979 

1,977 

1,962 

1,960 

1,888 

291 

1,951 

1,976 

1,968 

1,953 

1,960 

1,951 

1,951 

1,878 

1,878 

1,874 

1,916 

1,845

Mean

17.4 

13.6 

.55 

.34 

.90 

.27 

11.5 

4,182 

1.81 

.033 

.024 

.67 

.056 

.097 

.018 

.021 

.520

0

.

.

.

.

.

.

.

0

.
80°N

180°W. 150°W. 120°W. 90°W. 60°W. 30°W. 30°E. 60°E. 90°E

oo

60°N.

40°N.

80°S.

FIGURE 1.-Manganese nodule stations in the Scripps Institution of Oceanography's Sediment Data Bank 
Clarion-Clipperton zone in the northeastern 

equatorial Pacific-an area of about 2.5 million 

square kilometers in which nodules average 25.43 

percent manganese, 6.66 iron, 1.27 nickel, 1.02 

copper, and 0.22 cobalt (McKelvey and others, 

1979). Hein (1977) reported almost identical 

averages for the several thousand samples collected from the Clarion-Clipperton zone by the 

Centre National pour ITSxplotation des Oceans - 

namely 25.56 percent manganese, 6.40 iron, 1.25 

nickel, 1.05 copper, and 0.24 cobalt. The disproportionate number of samples there biases the world 

averages. As the comparison in table 1 shows, exelusion of Clarion-Clipperton zone values from the 

world averages decreases somewhat the average 

nickel, copper, and manganese contents, increases 

iron content, and has no effect on cobalt content. 

The world averages estimated by Cronan (1980, 

slightly revised from 1976; 1977) are even lower in 

manganese, nickel, and copper and higher in iron 

and cobalt (table 2). Because more than 70 percent 

of the stations outside of the Clarion-Clipperton 

zone are in the Pacific and because the average 

manganese, nickel, and copper contents of Pacific 

nodules are higher than those of Atlantic and Indian nodules (table 3), the influence of Pacific 

samples on the world averages shown in table 1 is 

considerable. D. Z. Piper (personal commun., 1981) 

pointed out, however, that nodules are far more 

abundant in the Pacific Ocean than they are in the 

Atlantic and Indian Oceans and that the number of 

Atlantic stations in the Scripps Sediment Data 

Bank (about 300 in comparison with about 300 Indian stations and nearly 1,800 Pacific stations) 

may give the Atlantic undue weight in the world 

average.

AVERAGE METAL CONTENT OF NODULES 

IN EACH OF THE OCEANS

Mero (1962), Cronan and Tooms (1969), and 

Cronan (1977) called attention to the fact that the 

average manganese, nickel, and copper contents of 

Pacific nodules are higher than those of Atlantic 

and Indian nodules. These differences and others 

are shown in table 3. Even when the ClarionClipperton zone stations are eliminated, Pacific 

nodules contain 1.38 and 1.2 times as much 

manganese and 2.36 and 1.5 times as much combined nickel and copper as Atlantic and Indian 

nodules, respectively. As might be expected, these 

differences also show up in the maximum values; 

nodules from the Pacific Ocean contain as much as

TABLE 2.-Comparison of the uxrrld average metal content of 

manganese nodules listed in table 1 with the values reported by 

Cronan (1980)

[The Clarion-Clipperton zone is taken to be the area defined by 7° to 15° N., 114° to 

____________________153° W.]____________________

Table 1 values (in percent)

World

World excluding World values

Clarion-Clipperton reported by Cronan

zone (in percent)

Mn __

Fe _____

Ni

Cu

Ni+Cu

Co

_ 18.60

_ 12.47

.66

.45

1.12

.27

17.45

13.63

.55

.34

0.90

.27

16.174

15.608

.4888

.2561

.7449

.2987

50.3 percent manganese and 3.44 percent combined nickel and copper in comparison with maximums of 40.9 and 32.3 percent manganese and 2.3 

and 3.24 percent combined nickel and copper for 

the Atlantic and Indian Oceans, respectively. On 

the other hand, both the mean and the maximum 

iron contents are highest for Atlantic 

nodules-16.97 and 50.0 percent, respectively, in 

comparison with 14.23 and 39.63 for Indian 

nodules and 11.4 and 41.9 percent for Pacific 

nodules. Although the mean cobalt content is the 

same for nodules from the Pacific and the Atlantic, 

the maximum in Pacific nodules is 2.23 percent in 

comparison with 1.44 in Atlantic nodules and 0.94 

in Indian nodules. The mean cobalt content of 

Atlantic nodules is more than twice the mean copper content and is nearly as much as the mean 

nickel content.

The metal ratios also differ considerably. Not 

only is the manganese-iron ratio much lower in 

Atlantic and Indian nodules, but the copper-nickel 

ratio in Atlantic nodules is also appreciably lower 

than the copper-nickel ratios in Pacific and Indian 

nodules. The moderate negative correlation between manganese and iron in Pacific nodules is 

much weaker in Indian Ocean samples and is nearly absent in Atlantic nodules. The strong positive 

correlation between nickel and copper and the negative correlation between combined nickel and copper and iron found in the Pacific nodules are 

weaker in Atlantic and Indian nodules.

For comparison, table 4 shows the ocean 

averages previously estimated by Mero (1962), 

Goldberg (1965), and Cronan (1980) along with 

those from table 3.

The average depth of the nodule stations is about 

the same in the Pacific and Indian but is nearly 700 

m shallower in the Atlantic. No data on concentration are available in the Atlantic; those in the In-
TABLE 3.-Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in the P

[The Clarion-Clipperton zone is taken to be the area defined by 7° to 15° N., 114° to 153° W. Metal ratios are based on ratios in samples for which both constituents have been d

would be obtained from the means of individual constituents]

All Pacific Ocean stations

Mn

Fe

Ni

Cu

Ni+Cu

Co

Concentration ____________ 

Depth

Mn/Fe ___ . ____________ 

Ni/Mn _

Cu/Mn _

Cu/Ni

(Ni+CuVMn

(Ni+Cu)/Fe

Co/Mn

Co/Fe

Co/(Ni+Cu) ___________ 

Depth versus Ni + Cu ________ 

Depth versus Co ___________

No. of 

stations

1,777 

1,772 

1,784 

1,771 

1,770 

1,710 

321 

1,677 

1,769 

1,771 

1,758 

1.770 

1,757 

1,752 

1,696 

1,691 

1,699 

1,650 

1,592

Mean

20.1 

11.4 

.76 

.54 

1.30 

.27 

10.89 

4,379 

2.64 

.04 

.03 

.71 

.07 

.18 

.02 

.03 

.38

Range

0.07-50.3 

.3-41.9 

.01-1.95 

.01-1.90 

.02-3.44 

.01-2.23 

.12-70.80 

46-7,280 

.01-100.0 

.001-.71 

.000-6.00 

.031-16.0 

.002-6.43 

.001-7.60

.000-.43 

.000-1.33 

.007-3.32

Standard 

deviation

6.9 

5.3 

.43 

.40 

.81 

.19 

10.22 

1,195 

4.31 

.027 

.144 

.648 

.157 

.278 

.015 

.038 

.460

Correlation 

coefficient

-0.45 

.71 

.62 

.88 

.69 

fiQ

.10 

.35 

-.24 

.28 

-.36

Pacific Ocean station

No. of 

stations

1,378 

1,377 

1,378 

1,365 

1,364 

1,314 

268 

1,351 

1,375 

1,372 

1,359 

1,364 

1,358 

1,357 

1,307 

1,306 

1,303 

1,324 

1,275

Mean

18.3 

12.77 

.63 

.41 

1.04 

.29 

11.61 

4,279 

2.10 

.03 

.03 

.68 

.06 

.12 

.02 

.02 

.46

TABLE 3. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in the Pacific, 

All Atlantic Ocean stations All In

Mn

Fe

Ni

Cu ______________ 

Ni+Cu

Concentration

Mn/Fe I

Ni/Mn

Cu/Mn _____________ 

Cu/Ni

(Ni+ Cu)/Mn ___________

(Ni+Cu)/Fe _____________ 

Co/Mn

Co/Fe

Co/(Ni+Cu) _

Depth versus Ni + Cu __________ 

Depth versus Co ____________

No. of 

stations

298

299

297

297 

296

285 

0

296 

298

296

296 

296

295 

296 

284

285

284

293

282

Mean

13.25

16.97

.32

.13 

.44

.27

3,614 

.95

.03

.02 

.56

.05 

.04 

.02

.02

.80

Range

0.04-40.9

1.54-50.0

.01-1.56

.01-.88 

.03-2.3

.01-1.44

232-7,180 

.002-13.38

.001-1.00

.001-1.00 

.05-6.00

.004-2.00 

.001-.54 

.001-.25

.001-.21

.041-4.50

Standard 

deviation

6.18

5.92

.23

.10 

.30

.20

1,513 

1.13

.07

.06 

.58

.13 

.05 

.02

.02

.66

Correlation 

coefficient

-0.03

.64

.29 

.64

.58 

-.38 

.53

.26

.05

.07 

-.38

No. of 

stations

303

303

302

300 

300

289 

23

304 

303

300

298 

300

298 

298 

287

287

287

299 

288

Mean

15.25

14.23

.43

.25 

69

.21 

10.82

4,304 

1.34

.03

.02 

.74

.04 

.07 

.02

.02

.50

0
TABLE 4. -Average metal contents of manganese nodules, by ocean

[The Clarion-Clipperton zone is taken to be the area defined by 7° to 15° N., 114° to 153° W.]

Pacific Ocean Atlantic Ocean Indian Ocean

Mn

Fe __ _ ___

Ni

Cu ________

Ni+Cu _____

Co _

All table

3 stations

20.1

11.4

.76

.54

1.30

.27

Table 3 stations

minus ClarionClipperton zone

18.84

12.77

.63

.41

1.04

.29

Mero

(1962)

24.2

14.0

.99

.53

1.52

.35

Goldberg

(1965)

19

14

.4

.5

.9

.3

Cronan

(1980)1

19.78

11.96

.634

.392

1.026

.335

Table 3

13.25

16.97

.32

.13

.44

.27

Mero

(1962)

16.3

17.5

.42

.20

.62

.31

Cronan

(1980)1

15.78

.78

.328

.116

.444

.318

Table 3

15.25

14.23

.43

.25

.69

.21

Cronan

(1980)1

15.10

14.74

.464

.116

.580

.325

1 Estimates made on the basis of detrital-free material.

dian Ocean are sparse but, for what they are 

worth, average about the same as those in the 

Pacific.

In the Earth's crust as a whole, in most of its 

common rocks, and in seawater, with few exceptions, Fe>Mn>Ni>Cu>Co (Lee and Yao, 1970; 

Goldberg and others, 1971). Except for means in 

Atlantic nodules, this relationship holds true also 

for means of nickel, copper, and cobalt shown in 

table 3; only in Atlantic nodules, however, is the 

mean iron content greater than the mean manganese content. As table 5 shows, the average ratios 

of nickel to cobalt and copper to cobalt in world and 

Pacific nodules outside the Clarion-Clipperton zone 

are somewhat similar to those in oceanic crust, 

although they do indicate a moderate impoverishment of cobalt relative to nickel and copper in the 

nodules. In seawater and Clarion-Clipperton zone 

nodules, the mean ratios of nickel to cobalt and 

copper to cobalt are much higher than those in the 

Earth's crust or its major subdivisions. The differences between the mean ratios of these metals 

in nodules and in average Earth's crust are minor, 

however, in comparison with the difference in the 

manganese-iron ratios. In the Earth's crust, iron is 

more than 40 times as abundant as manganese, 

and, even in seawater, it is 1.5 times higher. Iron is 

more abundant than manganese in some nodules 

also, but only in the Atlantic is the mean iron content of the nodules greater than the mean 

manganese content. In Clarion-Clipperton zone 

nodules, the average manganese content is more 

than four times the average iron content. In comparison with average contents in oceanic crust, 

world nodule means for nickel, copper, and cobalt 

are 47, 53, and 73 times greater, respectively, and 

the mean for manganese is 103 times greater, but 

that for iron is only 1.67 times larger. The difference between concentrations of iron and other 

metals in ocean crust and in Clarion-Clipperton

zone nodules is even greater. The average 

manganese, nickel, copper, and cobalt contents in 

Clarion-Clipperton zone nodules are 141, 91, 120, 

and 59 times greater, respectively, than their 

averages in oceanic crust, whereas the iron content is 0.89 times greater than its average in 

oceanic crust. The iron ratio would be even lower if 

it were based only on soluble iron, for, according to 

D. Z. Piper (personal commun., 1981), about 25 

percent of the total iron in metal-rich nodules is in 

insoluble silicates, most of which are very likely of 

extraneous origin. In marine manganese nodules, 

many metals are found in concentrations many 

times higher than their crustal abundances, but 

iron generally is not one of them; in fact, iron is 

less abundant in the nodules of greatest current 

economic interest than it is in oceanic crust.

WORLD AVERAGE METAL CONTENT OF 

NODULES IN LATITUDINAL ZONES

It has been known for some time that the subsea 

manganese nodules richest in nickel and copper 

are found in the equatorial regions of the Pacific 

Ocean (Mero, 1962; Horn and others, 1972, 1973; 

Arrhenius, 1975; Piper and Williamson, 1977; 

Skornyakova, 1979; Cronan, 1980; Heath, 1981; 

Exon, 1982), although J. Z. Frazer (written commun., 1980) pointed out that, whereas nodules 

greatly enriched in copper occur only near the 

equator, nodules high in nickel occur in many different regions. Hutchinson (1947) also reported a 

latitudinal zonation of the iron-manganese ratio in 

surficial sediments of the Atlantic, and Goldberg 

(1954) found a pronounced dependence of this ratio 

on latitude in pelagic sediments of the Pacific (see 

also Skornyakova, 1965; Greenslate, 1975; Piper 

and Williamson, 1977). Tables 6 and 7 show that 

the relation between latitude and the metal content of the nodules extends to higher latitudes as
TABLE 5. -Some metal ratios in manganese nodules in comparison with those in the Earth's crust and seawater

[Crustal values from Lee and Yao (1970). Seawater values from Goldberg and others (1971). Concentrations of manganese, nickel, and copper listed by these authors are much 

higher than more recent determinations by Bender and others (1977) and Bender and Gagner (1976), who are skeptical about the validity of higher values reported earlier, but 

these differences seem unlikely to affect sense of comparison of metal ratios shown here. Manganese nodule ratios based on ratios in samples for which both constituents have 

been determined. They differ, therefore, from metal ratios that would be obtained for means of individual constituents. The Clarion-Clipperton zone is taken to be the area 

defined by 7° to 15° N., 114° to 153° W.]

Manganese nodules

Mn/Fe

Ni/Co

Cu/Co _____

Earth

0.017

3.5

2.5

Crust

Oceanic

0.024 

3.2 

2.3

Continental

0.02 

3.4 

2.8

Seawater

0.66 

17.5 

7.5

World

2.26 

3.90 

2.82

World Pacific 

minus minus 

Clarion- Clarion- ClarionClipperton Clipperton All Clipperton 

zone zone Pacific zone Atlantic

1.81 

3.46 

2.39

4.52 

5.85 

4.81

2.64 

4.27 

3.19

2.10 

3.79 

2.69

0.95 

1.90 

.92

Indian

1.34 

3.67 

2.51

well. These data are summarized in table 8 for easy 

comparison. The average manganese, copper, and 

nickel contents generally increase toward the 

equator in both hemispheres, and iron decreases, 

although its high is in the 20° to 40° S. zone. 

Cobalt decreases slightly toward the equatorial 

region in the northern hemisphere but shows the 

opposite relation in the southern hemisphere. The 

increase toward the equator holds nearly as well 

for the maximum values of manganese, nickel, and 

copper. Curiously, however, the maximum values 

of iron and cobalt in both hemispheres are between 

latitudes 20° and 40°. Although the total metal 

content also increases toward the equatorial 

regions in both hemispheres, the difference is 

relatively small, except below latitude 60°, where 

the total of the five metals considered is only about 

25 percent, an indication that less than half of the 

nodules are composed of iron and manganese 

minerals.

The latitudinal relations for manganese and combined nickel and copper are also shown in figures 2 

and 3. These plots show well the increase in these 

metals toward the equator, but the graphs indicate 

that their contents decrease rather abruptly in the 

zone extending a few degrees north and south of 

the equator, as Piper and Williamson (1977) also 

showed. The graphs also show a rather curious 

decrease in manganese and combined nickel and 

copper between 20° and 30° S.

Although the average values for both nickel and 

copper generally increase toward the equatorial 

regions (the value for nickel between 40° and 60° 

S. is a slight departure from this trend), the 

copper-nickel ratios are not uniform (J. Z. Frazer, 

written commun., 1980). In the northern hemisphere, the copper-nickel ratio increases from an 

averge of 0.49 between 40° and 60° N. to 0.8 in the 

equatorial region. In the southern hemisphere, it is

more erratic; the high average of 0.80 is south of 

60° S. (where nickel and copper values are very 

low), and the low average of 0.59 is between 20° 

and 40° S. The latitudinal change in the percentages of nickel and copper contents is much greater 

than that for iron and manganese contents (Skornyakova, 1979).

The world averages are strongly influenced by 

the large number of Pacific stations, but somewhat 

similar latitudinal relationships prevail in each 

ocean (tables 9,10, and 11). Expectably, the trends 

for Pacific nodules are essentially the same as 

those for world averages. Although the data for 

some Atlantic latitudinal categories are too sparse 

to justify much confidence in the trends there, the 

general increase in manganese toward the equator 

is found in Atlantic nodules, although the highest 

value in the northern hemisphere is between 40° 

and 60° N. The highest means for nickel and copper are in the 20° to 40° range for both 

hemispheres in the Atlantic, and, although general 

equatorial increases are shown for these metals in 

the Pacific and Indian Oceans, slight secondary 

highs occur in the 40° to 60° range in both. The 

iron content of North Atlantic nodules decreases 

toward the equator but seems erratic in the South 

Atlantic. Although iron contents generally 

decrease toward the equator in the Pacific and Indian Oceans, the highest means are found in the 

20° to 40° range in both, and the highest value for 

the world (50 percent) is located in the 20° to 40° 

N. range in the Atlantic.

RELATION OF METAL CONTENT OF 

NODULES TO WATER DEPTH

Many previous investigators have reported a 

relation between nodule composition and water 

depth (Menard, 1964; Mero, 1965; Barnes, 1967;
00

TABLE 6.- Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in the no

[Metal ratios are based on ratios in samples for which both constituents have been determined. They differ, therefore, from metal ratios that would be obtained 

Between 40° and 60° N. Betwe

Mn

Fe __ _

Ni _ _ _

Cu _ _ _ _

Ni+Cu _ _ _

Co

Concentration _

Depth

Mn/Fe _ __

Ni/Mn

Cu/Mn ______________ 

Cu/Ni

(Ni+Cu)/Mn

(Ni+Cu)/Fe ______________ 

Co/Mn _ _

Co/Fe _

Co/(Ni + Cu) _ _

Depth versus Ni + Cu __________ 

Depth versus Co _

No. of 

stations

60

60

60

60

60

60

0

59

60

60

60 

60

60

60 

60

60

60

58 

58

Mean

15.67

15.46

.31

.14

.45

.32

3,395

1.20

.02

.01 

.49

.03

.04 

.02

.02

.94

Range

0.16-33.9

2.81-26.0

.01-.72

.01-.49

.02-1.21

.01-1.01

972-7,231

.02-4.35

.001-.071

.001-.062 

.050-4.00

.003-.125

.002-.144 

.001-.062

.001-.059

.123-3.071

Standard 

deviation

6.09

6.04

.17

.13

.28

.19

1,467

.81

.01

.01 

.56

.02

.03 

.01

.01

.71

Correlation 

coefficient

0.02

.53

.13 

.69

.39

-.46 

.49

.57

-.09

.33

.57

No. of 

stations

474

474

473

464

463

418

19

465

473

472

463 

463

462

462 

416

416

411

450 

405

Mean

18.1

13.64

.57

.32

.89

.28

5.43

3,753

2.06

.03

.02 

.59

.05

.09 

.02

.02

.56

0

.

.

.

.

.

.

.

.

TABLE 6. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in the no

Continued

Between 0° and <20° N.

Between 0° 

Clar

Mn

Fe __ __ _

Ni

Ni+Cu ___

P,n

Concentration

Depth _ _____

Mn/Fe

Ni/Mn _ __ _

Cu/Mn _

Cu/Ni

(Ni+Cu)/Mn _ _

Co/Mn __ _ _

Co/Fe __ _

Co/(Ni+Cu) .,__._.. _______

Depth versus Ni + Cu _________

Depth versus Co _____________

No. of 

stations

913 

907 

925 

924 

924 

905 

231 

827 

906 

913 

912 

924 

912 

906 

893 

887 

904 

825 

807

Mean

22.1 

9.2 

.93 

.73 

1.67 

.26 

9.7 

4,617 

3.36 

.04 

.04 

.80 

.08 

.27 

.01 

.03 

.26

Range

0.07-50.3 

.30-26.7 

.02-1.95 

.02-1.90 

.08-3.44 

.01-1.50 

.12-56.4 

46-7,180 

.024-100 

.002-.43

.001-6.00 

.04-16.00 

.01-6.43 

.007 7.60

.001-.43 

.001-1.33 

.014-2.82

Standard 

deviation

6.3 

4.5 

.42 

.42 

.82 

.16 

8.7 

1,054 

4.47 

.02 

.20 

.86 

.21 

.35 

.02 

.05 

.36

Correlation 

coefficient

-0.47 

.73 

.63 

.89 

.70 

-.74 

.07 

.38 

-.26 

.33 

-.40

No. of 

stations

514 

512 

519 

518 

518 

509 

178 

501 

512 

514 

513 

518 

513 

511 

504 

502 

508 

499 

490

Mean

20.41 

11.17 

.72 

.55 

1.27 

.28 

10.47 

4,501 

2.47 

.04 

.04 

.80 

.07 

.17 

.02 

.03 

.37

0
TABLE 7. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in the so

[Metal ratios are based on ratios in samples for which both constituents have been determined. They differ, therefore, from metal ratios that would be obtained 

Between 0° and <20° S.

Mn _ __ _ __ _ _

Fe __ __

Ni

Cu

Ni+Cu

Co

Concentration

Depth

Mn/Fe

Ni/Mn

CuflVfn .... ,. , .

Cu/Ni

(Ni+Cu)/Mn__ __ _ _

(Ni+Cu)/Fe _

Co/Mn _

Co/Fe

Co/(Ni + Cu)

Depth versus Ni + Cu

Depth versus Co

No. of 

stations

322 

324 

322 

319 

319 

312 

55 

319 

322 

320 

317 

319 

317 

319 

310 

312 

309 

312 

306

Mean

18.2 

13.8 

.55 

.37 

.91 

.29 

13.3 

4,543 

1.88 

.03 

.02 

.68 

.05 

.10 

.02 

.02 

.55

Range

0.21-42.3 

.83-34.0 

.01-1.8 

.01-1.66 

.02-3.24 

.01-1.88 

.18-62.0 

119-7,280 

.01-50.96 

.003-.10 

.000-.19 

.03-3.33 

.006-.286 

.001-.62 

.000-.09 

.000-.14 

.015-3.00

TABLE 7. -Metal contents (in percent), concentrations (in kg/m2), depthi

Mn

Fe

Ni

Cu

Ni + Cu __________ 

Co_ _ _

Concentration _ _______

Depth

Mn/Fe

Ni/Mn

Cu/Mn

Cu/Ni

(Ni+Cu)/Mn

(Ni+Cu)/Fe _

Co/Mn _____ ______

Co/Fe __ _ __

Co/(Ni+Cu) __ __ _

Depth versus Ni + Cu __________ 

Depth versus Co _ _ _

No. of 

stations

212 

212 

210 

207 

207 

203 

1 

211 

212 

210 

207 

207 

207 

207 

203 

203 

200 

206 

202

Mean

13.4 

14.6 

.45 

.20 

.65 

.19 

8.4 

3,907 

1.16 

.038 

.021 

.684 

.059 

.066 

.018 

.013 

.442

Between 40° and

Range

0.20-36.0 

1.1-30.6 

.01-1.65 

.01-.89 

.03-2.49 

.01-1.06

369-6,117 

.013-15.73 

.003-.52 

.002-.35 

.096-7.00 

.011-.87 

.003-1.32 

.001-.23 

.001-.07 

.014-2.27

Standard 

deviation

6.9 

5.3 

.38 

.34 

.69 

.22 

12.3 

1,100 

3.25 

.02 

.02 

.37 

.03 

.12 

.01 

.02 

.53

Correlation 

coefficient

-0.39 

.68 

.58 

.84 

.66 

-.59 

.01 

.38 

-.31 

.21 

-.44

No. of 

stations

361 

361 

358 

359 

358 

352 

38 

360 

361 

357 

358 

358 

357 

357 

351 

351 

352 

356 

350

Betw

Mean

15.2 

15.9 

.42 

.20 

.61 

.29 

17.3 

4,266 

1.08 

.03 

.01 

.59 

.04 

.05 

.02 

.02 

.61

s (in m), and metal ratios of manganese nodules in the so

Continued

<60° S.

Standard 

deviation

6.8 

5.6 

.35 

.16 

.49 

.14

1,024 

1.36 

.05 

.03 

.84 

.08 

.11 

.02 

.01 

.43

Correlation 

coefficient

-0.12 

.75 

.53 

.78 

.72 

-.47 

.36 

.29 

.10 

.25 

-.30

No. of 

stations

35 

35 

34 

34 

34 

33 

0 

35 

35 

34 

34 

34 

34 

34 

33 

33 

33 

34 

33

Mean

9.4 

14.9 

.31 

.19 

.49 

.19

4,183 

.67 

.04 

.03 

.80 

.07 

.04 

.03 

.01 

.54
£

£ J23-£$b£

CO h-' I »

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*». O> O <£> O «>

N> O» <J CO CO © © 

/P/Co"Hi'K» /N>'ox

CO

CO

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l_» 00 l-» l-» CO *>.

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bo J-» b> to *>. b> *> 

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8

MANGANESE CONTENT, IN PE

cn

N) 

O

N)

cn

CO

o

CO

cn

O 

m

o 

N>o

- . ;.-i-:: r-^ ^r^'rT^' 

>: ;;.->v>f.v^% '- / -. . ". ^ « :vUi**n«v. >*V*i>?K * " '* " . * > ** :^.,-^::-^:--;- -. .. . '.'!,.:..-;' "" ' *
coo

COMBINED NICKEL AND COPPER CONT

-» ISJ 

ISJ 

O

C£

 . ***?;"£., .,-. _

H

D 

m

Ni

s

§o

00

o

* '' '
KZ 

LLJ 

U 

QC 

LU

ULJ

Z

o

U

QC 

ULJ 

Ou

U 

Q

<

_l 

LU

y

z

o

i '

m

O 

u

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 4. - Relation between depth and combined nickel and copper content in manganese nodules at stations in the Scripps Institution of Oceanography's Sediment Data Bank.

17.10 percent, combined nickel and copper decreases to 0.99 percent, iron increases to 13.01 percent, and cobalt content remains unchanged.

Given the rather marked differences in the metal 

contents of these groups, one might expect the correlations of nickel, copper, and cobalt with depth to 

be stronger than tables 1, 3, 6, and 7 indicate. The 

explanation is found in figures 4 and 5, which show 

that the depth relation is not linear; rather, there is 

a threshold depth of about 2,900 to 3,000 m, above 

which combined nickel and copper contents 

greater than 1 percent are rare and below which

nodules containing cobalt in amounts greater than 

about 0.6 percent are rare. As figures 6 through 11 

show, below the threshold depth for combined 

nickel and copper and above it for cobalt, the maximum metal contents rise to an optimum depth 

range and then decline. Nodules containing more 

than 3.0 percent combined nickel and copper, for 

example, are found only in a depth range of about 

4,450 to 5,450 m in the Pacific, and nearly all of 

them are in a range of 4,800 to 5,200 m. No such 

values are found in the Atlantic, but the few 

samples containing more than 1.5 percent com12
ill 2

(J

DC

HI

Q_

z 111

z 

o 

u

GO 

O 1

u

. f .

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 5. - Relation between depth and cobalt content in manganese nodules in the Scripps Institution of Oceanography's Sediment

Data Bank.

TABLE 9. -Average and maximum (in parentheses) metal contents (in percent) of manganese nodules in the Pacific Ocean,

categorized by latitude

Mn _

Fe _

Ni

Cu

Ni+Cu

Co

Total

40°-<60° 

N. 

(30 stations)

15.71 (33.9)

11.33 (26.0)

.35 (.72)

.19 (.49)

.54 (1.21)

.24 (.86)

27.82

20°-<40° 

N. 

(355 stations)

19.72 (39.56)

12.28 (41.90)

.66 (1.69)

.38 (1.10)

1.04 (2.46)

.28 (1.64)

33.32

0°-<20° 

N. 

(885 stations)

22.39 (50.30)

8.90 (26.7)

.96 (1.95)

.76 (1.90)

1.72 (3.44)

.26 (1.50)

33.27

0°-<20° 

S. 

(244 stations)

18.30 (42.3)

14.17(34.0)

.54 (1.80)

.34 (1.54)

.89 (3.11)

.31 (1.88)

33.66

20°-<40° 

S. 

(146 stations)

16.46 (38.02)

16.93(32.20)

.47(1.73)

.22 (.65)

.69 (2.17)

.35 (2.23)

34.43

40°-60° 

S. 

(98 stations)

14.89 (36.0)

14.13 (28.20)

.54 (1.65)

24 ( 84)

.79 (2.49)

.22 (1.06)

30.02

>60°S. 

(32 stations)

10.11 (22.40)

15.57 (25.64)

.32 (1.00)

.20 (.58)

.52 (1.58)

.19 (.57)

26.39

13
H 

Z 

uu 

CJ

cc. 

uu

Q.

UU

z 

o

CJ

Q_

CL 2

O 

U

U

2 1

Z 

00

O

CJ

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 6.-Relation between depth and combined nickel and copper content in Pacific Ocean manganese nodules at 1,770 stations

in the Scripps Institution of Oceanography's Sediment Data Bank.

TABLE 10. -Average and maximum (in parentheses) metal contents (in percent) of manganese nodules in the Atlantic Ocean,

categorized by latitude

(

Mn

Fe

Ni ______ 

Cu

Ni+Cu ______ 

Co

Total

>60°N. 

1 station)

10.36

22.83 

.01 

.03

.04 

.18

33.41

40°-<60° N. 

(30 stations)

15.03 (27.39)

19.58 (24.28) 

.27 (.68) 

.08 (.34)

.35 (1.02) 

.39 (1.01)

35.35

20°-<40° N. 

(120 stations)

13.25 (40.90)

17.62 (50.00) 

.30(1.56) 

.13 (.62)

.44 (1.97) 

.29 (1.04)

31.59

0°-<20° N. 

(12 stations)

14.06 (34.80)

15.84 (23.70) 

.24 (.73) 

.11 (.48)

.35 (1.21) 

.25 (0.51)

30.50

0°-<20° S. 

(7 stations)

15.13 (24.00)

19.54 (22.4) 

.25 (.43) 

.09 (.15)

.34 (.51) 

.49 (1.44)

35.50

20°-<40° S. 

(56 stations)

14.51 (26.78)

14.67 (26.40) 

.42 (1.42) 

.15 (.88)

.57(2.30) 

.30(1.01)

30.05

40°-<60° S. 

(72 stations)

11.16(26.64)

16.56(34.55) 

.30 (.99) 

.13 (.41)

.43 (1.40) 

.16 (.76)

28.31

>60°S. 

(1 station)

1.00

7.10 

.14 

.10

.24 

.10

8.44

14
LU 

O 

DC 

LU 

Q_

I

O 

O

cc

LU 

Q_ 

Q_ 

O 

O

LU

Q

LU

Z 

CD 

2 

O 

O

'.». 

 !_

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 7.-Relation between depth and combined nickel and copper content in Atlantic Ocean manganese nodules at 296 stations

in the Scripps Institution of Oceanography's Sediment Data Bank.

TABLE 11. -Average and maximum (in parentheses) metal contents (in percent) of ma',

categorized by latitude

[-, no data]

Mn ............

Fe

Ni

Cu

Ni+Cu

Co

Total

0°-20° N. 

(28 stations)

16.52 (32.30)

16.64 (22.80)

.38 (.81)

.10 (.30)

.48 (1.08)

.29 (.93)

33.93

0°-<20° S. 

(73 stations)

18.05 (32.25) 

11.92 (19.70) 

.58 (1.58) 

.47 (1.66) 

1.06 (3.24) 

.20 (.94) 

31.22

20°-<40° S. 

(159 stations)

14.36 (26.50) 

15.47 (39.63) 

.37 (1.19) 

.18 (.84) 

.55 (1.95) 

.22 (.62) 

30.6

40°-<60° S. 

(42 stations)

13.53 (24.57) 

12.25 (21.60) 

.48 (1.43) 

.25 (.89) 

.72 (2.13) 

.13 (.37) 

26.64

>60° S. 

(2 stations)

3.07 (3.93) 

8.94 (12.22) 

.04 

.02 

.06

12.07

15
TABLE 12. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules in water depth

[The Ciarion-Clipperton zone is taken to be the area defined by 7° to 15° N., 114° to 153° W. Metal ratios are based on ratios in samples for which both constituents have been de

would be obtained from the means of individual constituents]

<2,000m

No. of 

stations

Mn _______

Fe

Ni

Cu _________

Ni+Cu _____ 

Co ________ 

Concentration _

Depth ________

Mn/Fe _ _ _

Ni/Mn _______

Cu/Mn _____

Cu/Ni _____

(Ni + Cu)/Mn ___

(Ni + CuVFe ___

Co/Mn

Co/Fe _____

Co/(Ni+Cu) ___

Depth versus

Ni+Cu ___

Depth versus Co

186 

186

185

174 

174 

170 

0

188

186

185

174

174

174

174

170

170

164

174

170

Mean

18.00 

14.81

.41

.08 

.50 

.53

1,266

2.17

.026

.007

.303

.033

.042

.030

.038

1.154

Standard 

Range deviation

0.16-50.30 

.42-41.9

.01.1.16

.01-0.73 

.02-1.78 

.01-2.23

46-2,000

.02-60.45

.001-.14

.000-.10

.04-7.00

.002-.24

.002- .20

.000-.10

.001-.17

.07-3.29

8.30 

6.14

.22

.08 

.26 

.37

449

6.62

.02

.01

.64

.03

.03

.02

.03

.74

Correlation 

coefficient

-0.003

.52

.05

.38

.46

-.10

.54

.16

.33

.16

.14

> 4,000 m

No. of 

stations

1,561 

1,557

1,565

1,565 

1,563 

1,530 

332

1,576

1,554

1,552

1,552

1,563

1,550

1,546

1,517

1,513

1,527

1,563

Mean

18.6 

11.7

.71

.52 

1.24 

.24 

11.1

4,946

2.32

.04

.03

.76

.07

.17

.01

.02

.33

Range

0.04-42.3 

.3-50.0

.01-.189

.01-1.90 

.02-3.44 

.01-1.04 

.12-70.8

4,000-7,280

.002-100.0

.001-1.00

.001-1.00

.05-16.00

.003-2.00

.001-7.60

.000-.25

.000-1.33

.005-2.80

Standard 

deviation

6.9 

5.3

.44

.41 

.83 

.12 

10.5

507

3.70

.04

.03

.72

.07

.29

.01

.04

.34

Stations outside Ciario

Correlation 

coefficient

-0.51

.82

.77

.91

.81

-.72

.10

.32

-.11

-.02

.04

No. of 

stations

1,249 

1,249

1,247

1,247 

1,245 

1,221 

279

1,258

1,246

1,240

1,240

1,245

1,238

1,238

1,214

1,214

1,218

1,245

1,221

M

4
Ill 

o

DC 

LLJ 

Q_

I

o 

o

DC 

LLJ 

Q_ 

Q.

O 

O

LLJ 

^

o

Q 

LLJ 1

m

O 

o

1000 2000 3000 4000

DEPTH, IN METERS

5000 6000 7000

FIGURE 8. - Relation between depth and combined nickel and copper content in Indian Ocean manganese nodules at 300 stations in

the Scripps Institution of Oceanography's Sediment Data Bank.

bined nickel and copper occur in a depth range of 

about 4,850 to 5,200 m. In the Pacific, the optimum 

depth range for nodules containing more than 1 

percent cobalt is about 800 to 1,850 m; in the 

Atlantic, it is about 1,000 to 1,650 m. No such high 

values have been found in Indian nodules, but one 

of the two highest reported is from a depth of 

about 1,350 m. The rather substantial differences 

in the mean values of nickel, copper, iron, and 

cobalt above and below the 3000-m depth are 

shown in table 13.

Cronan and Tooms (1969, p. 340) also noted the 

enrichment of nickel and copper in the deeper 

water nodules and observed "that 3000-4000 m is a 

critical depth for many of the elements. In the case 

of Co, Cu, Pb, Ba, and V, in particular, there is a 

sharp difference between the concentrations above 

and below 3000 m. Those elements which are in 

higher concentrations in the shallower waters tend 

to increase gradually in concentration from 3000 m 

to the surface. A similar distribution is observed in 

the case of Cu although the highest average con17
B 2 

cc

UJ

a.

LU

Z

o 

o

00 

o 

o

"' V ' ; * .'"' ' . i'\~*

.» . ..;. . -..'^.r £& - - ' 5-3r 

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 9.-Relation between depth and cobalt content in Pacific Ocean manganese nodules at 1,710 stations in the Scripps

Institution of Oceanography's Sediment Data Bank.

TABLE IB.-Metal contents of manganese nodules in water deptiis above and below 3,000 m

< 3,000 m > 3,000 m

Mn

Fe

Cu

Ni+Cu

Co

No. of stations

324

324

323

309

309

307

Mean (percent)

17.16

15.63

.39

.10

.50

.46

No. of stations

1,931

1,926

1,936

1,935

1,933

1,855

Mean (percent)

18.60

12.17

.69

.49

1.18

.23

18
Iz

LU

O 

DC 

LU 

0.

5 1 

o

O

CD 

O 

O

\.

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 10. -Relation between depth and cobalt content in Atlantic Ocean manganese nodules at 285 stations in the Scripps Institution of Oceanography's Sediment Data Bank.

centrations are recorded at the maximum depths." 

(As indicated above, the increase "to the surface" 

does not hold for cobalt). Rper (1974) reported 

that the rare-earth composition of nodules also 

changes at the 3,000-m depth, and Piper and 

Williamson (1977) showed that the high values of 

the manganese-iron ratio as well as those of nickel 

and copper are below this depth.

As figure 12 shows, manganese shows little correlation with depth, although the data suggest a 

decrease in the maximum values and possibly an 

increase in the minimum with increasing depth. No

nodule analysis shows more than 32 percent 

manganese below depths of 5,300 m, and only one 

reports less than about 13 percent below 6,000 m. 

The increase in the copper-nickel ratio with increasing depth reported by S. A. Mooreby (unpublished thesis, 1978, discussed by Cronan (1980)) for 

Indian Ocean nodules is seen also by comparing the 

mean copper-nickel ratio with mean depths in the 

various populations analyzed in the tables here. 

Thus, at the mean depth of 1,266 m for samples 

from depths of less than 2,000 m, the copper-nickel 

ratio is 0.196; at a mean depth of 3,395 m for

19
z

LLJ 

CJ

a:

UJ

o_

z

UJ

O 

O

CD

O 

O

1000 2000 3000 4000

DEPTH, IN METERS

5000 6000 7000

FIGURE 11.-Relation between depth and cobalt content in Indian Ocean manganese nodules at 289 stations in the Scripps Institution of Oceanography's Sediment Data Bank.

samples between 40° and 60° N., the ratio is 0.49; 

at a mean depth of 4,379 m for all Pacific stations, 

it is 0.71.

RELATION OF NODULE CONCENTRATION 

TO WATER DEPTH

The publicly available data on concentration of 

manganese nodules are insufficient, especially outside of the Pacific, to support any firm conclusions, 

but, in tiie population shown in figure 13, all but

one of the stations having more than about 13 kg of 

nodules per square meter occur at depths greater 

than about 3,700 m. Analysis of hundreds of freefall grab samples collected by the Centre National 

pour ITExploitation des Oceans-SoeietS Le Nickel 

and the Association Francaise pour ITStude et la 

Recherche des Nodules Polymetalliques led Pautot 

and Melguen (1979) to conclude that the greatest 

concentrations of nodules are restricted to an interval of 300 to 400 m, the lower limit of which 

varies from basin to basin but falls within the 

range of 4,350 to 5,200 m-close to the carbonate

20
55

50

45

\- 40

01

o

DC

a! 35

Iz

LU hLU 

(/) 

LU

30

8 25

20

15

10

' *.* V

 '*.'*'* -; '* %*.s' "*,'*'* » »

: '' ' ; */.<* /' " ' /. ' "

' '. '"*.* .'.** * *

1000 2000 3000 4000 5000

DEPTH, IN METERS

6000 7000 8000

FIGURE 12.-Relation between depth and manganese content in manganese nodules at stations in the Scripps Institution of

Oceanography's Sediment Data Bank.

compensation depth in each basin. Skornyakova 

(1979) also reported that the highest concentrations are confined to depths below the carbonate 

concentration depth.

Although available evidence thus indicates that 

the greatest concentrations of nodules occur at 

abyssal depths, the encrustations, which average 2 

cm in thickness over large areas, reported by 

Manheim and others (1982) on mid-Pacific seamounts at depths between 2,500 and 1,200 m 

represent a far greater concentration of 

metalliferous oxides per unit area than the nodules

do, except in their rarest concentrations; in fact, 

the average concentration of manganese oxide 

crust of 33 kg/m2 implied by Manheim and Halbach 

is four times the average of 8.33 kg/m2 dry weight 

in nodules of the Clarion-Clipperton zone.

METAL-RICH TYPES OF MANGANESE 

NODULES

Examination of metal-rich manganese nodules 

led us to conclude that three distinct, only rarely 

overlapping compositional types of possible

21
DC 80 

LU

LU

DC 

<

o

70

DC 

LU°- 60

DC 

CD 

O

LU

O 

O

Z

LU 

(/> 

LU

Z

50

40

O

20

10

DC

LU 

O

2 i

O 2500 3000 3500 4000 4500 5000

DEPTH, IN METERS

5500 6000 6500

FIGURE 13.-Relation between depth and concentration of manganese nodules at stations in the Scripps Institution of

Oceanography's Sediment Data Bank.

economic interest could be recognized: (1) nodules 

containing more than 1 percent combined nickel 

and copper, (2) nodules containing more than 0.5 

percent cobalt, and (3) nodules containing more 

than 35 percent manganese (although nodules in 

this group contain more than 0.5 percent cobalt only exceptionally, they do average nearly 1.1 percent combined nickel and copper). The metal contents of these types are summarized in tables 14, 

15, and 16; the groups having high combined nickel 

and copper contents and high cobalt contents have 

been broken into two parts. These groups are

similar to ones defined for the composition of 

Pacific nodules by Howarth and others (1977) by 

means of a nonlinear mapping technique. Their 

group 2, for example, averages 0.60 percent 

cobalt, 0.56 percent combined nickel and copper, 

and 15.58 percent manganese. Their groups 3, 4, 

and 5 average 0.3, 0.27, and 0.17 percent cobalt, 

1.15, 1.97, and 2.74 percent combined nickel and 

copper, and 17.67, 22.07, and 26.99 percent 

manganese, respectively. Their group 6 averages 

0.06 percent copper, 1.05 combined nickel and copper, and 34.29 percent manganese.

22
to

CO

TABLE l^.-Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules containing 

more

[Metal ratios are based on ratios in samples for which both constituents have been determined. They differ, therefore, from metal ratios that would be obtained 

> 1 .8 percent Ni + Cu

Fe ~~ ~ ~ ~~

Ni _ _

Cu

Ni+Cu_ _ _ _

Co

Concentration _______________ 

Depth

Mn/Fe _________________ 

Ni/Mn ____________________ 

Cu/Mn ________________ 

(Ni+Cu)/Mn ______________ 

(Ni-i-Cu)/Fe _ _

Co/Mn

Cu/Ni _ _ _

Co/(Ni+Cu) _____________ 

Co/Fe _______________ 

Depth versus Ni + Cu _________ 

Depth versus Co _ ____________

No. of 

stations

557 

554 

561 

561 

561 

527 

141 

506 

553 

557 

557 

557 

554 

523 

561 

527 

520 

506 

473

Mean

26.17 

6.89 

1.29 

1.05 

2.34 

.21 

5.9 

4,720 

4.43 

.05 

.04 

.09 

.40 

.01 

.82 

.09 

.04

Range

14.02-45.6 

.3-16.92 

.56-1.95 

.33-1.90 

1.81-3.44 

.01-.63 

.12-27.25 

2,660-6,401 

1.14-100 

.02-.09 

.01-.08 

.05-.15 

.12-7.6 

.000-.03 

.20-2.68 

.005-.26 

.001-1.33

Standard 

deviation

3.48 

2.08 

.18 

.24 

.35 

.08 

5.8 

585 

4.91 

.01 

.01 

.01 

.40 

.004 

.20 

.04 

.06

Correlation 

coefficient

-0.33 

.44 

.38 

.49 

-.54 

.17

.34 

-.05 

.08 

.35 

.10

No. of 

stations

459 

457 

465 

465 

465 

444 

76 

423 

456 

459 

459 

459 

457 

438 

465 

444 

436 

423 

403

a 1.0

Mean

20.4 

10.2 

.85 

.54 

1.39 

.23 

9.3 

4,668 

2.36 

.04 

.03 

.07 

.16 

.01 

.67 

.17 

.02

1
TABLE 15. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodules containing 1

more outside the Clarion-Clipperton zone

[The Clarion-Clipperton zone is taken to be the area defined by 7° to 15° N., 114° to 153° W. Metal ratios are based on ratios in samples for which both constituents have been de

would be obtained from the means of individual constituents]

> 1.8 percent Ni+Cu

Mn

Fe

Ni _

Cu

Ni+Cu _ _ _

Co

Concentration

Depth

Mn/Fe _ __

Ni/Mn_

Cu/Mn _

Cu/Ni __ _

(Ni+ Cu)/Mn ___________ 

(Ni+CuVFe ______________ 

Co/Mn

Co/Fe _ _

Co/(Ni+Cu) _____

Depth versus Ni + Cu _

Depth versus Co _ _ _

No. of 

stations

263 

263 

264 

264 

264 

238 

90 

259 

263 

263 

263 

264 

263 

263 

237 

237 

238 

259 

233

Mean

26.10 

7.72 

1.24 

.98 

2.23 

.19 

5.08 

4,652 

3.70 

.05 

.04 

.80 

.09 

.32 

.007 

.03 

.08

Range

14.02-45.60 

3.23-16.92 

.56-1.80 

.33-1.90 

1.81-3.44 

.01-.49

.20-20.0 

3,160-6,401 

1.14-14.12 

.02-.09 

.01-.07 

.20-2.68 

.052-. 15 

.14-.74 

.000-.02

.001-.08 

.005-.23

Standard 

deviation

3.40 

2.09 

.17 

.27 

.34 

.08 

5.36 

741 

1.44 

.01 

.01 

.24 

.01 

.13 

.004 

.01 

.04

Correlation 

coefficient

-0.33 

.29 

.33 

.14 

.41 

-.58 

-.24 

.15 

-.03 

.44 

.12

No. of 

stations

367 

365 

370 

370 

370 

350 

74 

356 

364 

367 

367 

370 

367 

365 

347 

345 

350 

356 

337

> 1.0- 

Mean

20.61 

10.78 

.84 

.52 

1.36 

.22 

9.44 

4,640 

2.17 

.04 

.03 

.66 

.07 

.14 

.01 

.02 

.17

7

1

1

1,

.0

.0

.0

.0
cn

TABLE 16. -Metal contents (in percent), concentrations (in kg/m2), depths (in m), and metal ratios of manganese nodldes containing m

85 percent manganese

[Metal ratios are based on ratios in samples for which both constituents have been determined. They differ, therefore, from metal ratios that would be obtained 

a 1.0 percent Co

No. of 

stations

Mn _______ 

Fe _______ 

Ni

Cu

Ni+Cu ______

Co _____

Concentration _

Depth _____ 

Depth/(Ni+Cu) _ 

Depth/Co ____

Co/Fe _____

Mn/Fe _____

Ni/Mn _____

Cu/Mn _____

(Ni+Cu)/Mn __ 

(Ni+Cu)/Fe __ 

Co/Mn _____

Co/Ni _____

Co/(Ni+Cu) __

27 

27 

27 

27 

27 

27

0

23 

23 

23 

27

27

27

27

27 

27 

27

27

27

Mean

26.02 

15.6 

.55 

.094 

.64 

1.25

1,764 

.083

1.74

.021

.004

.025 

.045 

.049

.175

2.15

Range

18.83-50.3 

9.5-20.3 

.3-1.25 

.03-.36 

.33-1.5 

1.0-2.23

795-5,192 

.05-. 17

1.10-3.18

.01-.05

.001-.02

.01-.06 

.02-.16 

.03-.07

.05-.84

.67-3.32

Standard 

deviation

5.98 

2.75 

.21 

.08 

.25 

.30

1,027 

.03

.57

.007

.004

.009 

.03 

.01

.15

.70

Correlation 

coefficient

0.31 

-.33 

-.21

-.16

.50

-.14

.37 

-.72 

.38

.38

.15

a 0.5-1.0 percent Co

No. of 

stations

155 

154 

155 

150 

150 

155

4

152 

147 

152 

154

154

155

150

150 

149 

155

150

150

Mean

20.0 

16.54 

.44 

.16 

.60 

.64

17.2

2,791 

.04

1.35

.02

.01

.03 

.05 

.03

.34

1.33

Range

6.3-45.5 

4.2-26.0 

.011-1.47 

.02-1.50 

.19-2.8 

.05-0.97

1.8-30

64-5,775 

.02-.13

.044-7.5

.007-.11

.001-.08

.01-.14 

.01-.58 

.02-.09

.04-1.50

.2-3.43

Standard 

deviation

5.29 

3.92 

.21 

.22 

.39 

.13

13.3

1,474 

.02

.89

.01

.01

.02 

.07 

.01

.26

.61

Correlation 

coefficient

0.26 

-.40 

-.03

-.28

.54

.15

.38 

-.58 

.31

.63

.06

No. of 

stations

27 

27 

27 

27 

27 

24

1

27 

27 

24 

24

27

27

27

27 

27 

24

27

24

>35 

M

3,4
Tables 14 and 15 show nodules high in combined 

nickel and copper worldwide and outside the 

Clarion-Clipperton zone. Average combined nickel 

and copper contents of nodules within the ClarionClipperton zone seem to be slightly richer than 

those of nodules outside, but nodules rich in combined nickel and copper have essentially the same 

chemical compositions wherever they are found. 

Given the depth and latitude relations already 

discussed, one would expect nodules rich in nickel 

and copper to occur at abyssal depths in low 

latitudes; tables 14 and 15 and figures 14 and 15 

confirm this expectation. Figures 14 and 15, 

however, show that nodules rich in nickel and copper also occur at higher latitudes. In both the 

Pacific and the Indian Oceans, nodules richest in 

nickel and copper are found mainly in the eastern 

parts (Cronan and Tooms, 1969; Tooms and others, 

1969; Cronan, 1980). Nodules containing 1.8 percent combined nickel and copper or more are 

essentially absent from the Pacific west of 180° 

W., even at low latitudes, and none have been 

reported west of 75° E. in the Indian Ocean (fig.

14). Only a few samples containing 1.8 percent 

combined nickel and copper or more have been 

reported from the Atlantic, but the largest concentrations of samples containing > 1.0 to < 1.8 percent also lie on the eastern side of the basin (fig.

15).

Nodules containing >1.0 to <1.8 percent combined nickel and copper are generally distinct from 

those in the cobalt- and manganese-rich groups. In 

comparison with those containing 1.8 percent combined nickel and copper or more, they are lower in 

manganese and higher in iron, and their coppernickel ratio is appreciably lower.

Tables 14 and 15 indicate that the concentration 

of nodules on the sea floor is inversely related to 

combined nickel and copper content, both in the 

lower average concentration found in the ^ 1.8- 

percent nodules in comparison with those in the 

> 1.0- to < 1.8-percent range and in the maximum 

nodule concentration in each group. This relation 

was previously reported by Menard and Frazer 

(1978) for the entire Pacific but was found to be 

weak in the Clarion-Clipperton zone (McKelvey 

and others, 1979).

The manganese content of nodules high in cobalt 

(table 16) is similar to that of nodules high in combined nickel and copper, but the iron content is 

much higher. They are low in combined nickel and 

copper, and the copper-nickel ratio is also low. 

Comparison of the sO.5- to < 1.0-percent group

shows that manganese is appreciably higher in the 

> 1.0-percent group, iron is slightly lower, the 

copper-nickel ratio is lower, and the average depth 

is about 1,000 m less. Figures 16 and 17 suggest, 

along with previous observations (for example, 

Mero, 1962; Menard, 1964; Cronan and Tooms, 

1969; Piper and Williamson, 1977; Calvert, 1978), 

that, although cobalt-rich nodules occur over a 

wide range of latitudes and longitudes, those containing more than 1 percent and even more than 

0.5 percent cobalt are relatively more populous in 

the central and western Pacific. The ^1.0 percent 

cobalt group is essentially of the same composition 

as the encrustations recently reported on midPacific seamounts by Manheim and others 

(1982)-1.0, 0.5, 25.0, and <0.1 percent cobalt, 

nickel, manganese, and copper, respectively, in the 

crusts, according to Manheim and others, in comparison with 1.25, 0.55, 26.02, and 0.094 percent 

averages for the same metals in the ^1.0 percent 

cobalt nodules shown in table 16. It may be that 

some of the samples reported as nodules in the 

Scripps Data Bank are in fact encrustations.

Nodules containing more than 1.0 percent cobalt 

have not been reported in the Indian Ocean, but 

those containing 0.5 percent cobalt or more are 

confined to the western side of that basin. The 

number of samples in the > 1.0-percent cobalt 

group is only 27, perhaps not enough to justify 

much confidence in the observations made about 

them here.

Nodules high in manganese (table 16) also have 

been found at only 27 stations, again too few to 

support much generalization about them. The data, 

however, indicate that they are relatively low in 

iron (some are very low); the mean manganese-iron 

ratio is 16.12, in comparison with 4.43 for nodules 

of the 1.8-percent or more combined nickel and 

copper type. The average combined nickel and copper content, 1.08 percent, falls in the lower range 

of the ^1.0- to < 1.8-percent combined nickel and 

copper group. Halbach and Fellerer (1980) found, 

for nodules from the southeastern Pacific, that 

combined nickel and copper increases as the 

manganese-iron ratio increases up to about 5 and 

decreases as the ratio increases further.

Although the number of samples shown in figure 

18 is small, all but two of them occur in the eastern 

and north equatorial Pacific (see also Mero, 1962; 

Cronan and Tooms, 1969; Skornyakova, 1979; 

Cronan, 1980; Heath, 1981). Only one sample is in 

the Atlantic, and none have been found in the Indian Ocean. Whereas the nodules especially rich in

26
180°W. 150°W. 

80°N.

120°W. 90°W. 60°W. 30°W. 0° 30°E. 60°E. 90°E. 

to

60°N.

80°S.

FIGURE 14.-Distribution of manganese nodules containing 1.8 percent combined nickel and coppe
80°N

180°W. 150°W. 120°W. 90°W. 60°W. 30°W. 30°E. 60°E. 90°E. 

to

00

60°N.

80°S.

FIGURE 15.-Distribution of manganese nodules containing 1.0 percent or more and less than 1.8 percent comb
180°W. 150°W. 120°W. 90°W. 60°W. 30°W. 0° 30°E. 60°E. 90°E. 

80°N

to

60°N.

40°N.

20°N.

20°S.

40°S.

60°S.

80°S.

FIGURE 16.-Distribution of manganese nodules containing 1.0 percent cobalt or more.
80°N

180°W. 150°W. 120°W. 90°W. 60°W. 30°W. 0° 30°E. 60°E. 90°E. 

60°N.

60°S.

80°S.

FIGURE 17.-Distribution of manganese nodules containing 0.5 percent or more and less than 1.0 per
80°N

180°W. 150°W. 120°W. 90"W. 60°W. 30°W. 0° 30°E. 60°E. 90°E. 

CO

60°N.

40°N.

20°N.

20°S.

40°S.

60°S.

80°S.

FIGURE 18.-Distribution of manganese nodules containing 35.0 percent manganese or mo
manganese are found along the eastern margin of 

the Pacific basin, Skornyakova (1979) reported 

that those rich in iron are from its western margin, 

where they have concentrations as high as 70 percent Fe203 and manganese-iron ratios of less than 

1 (see also Price and Calvert, 1970).

TARGETS FOR EXPLORATION

The Clarion-Clipperton zone of the northwestern 

equatorial Pacific is the largest and most promising area known to have nodules rich in nickel and 

copper; in fact, at this stage, it seems likely that no 

other area of comparable size containing nodules of 

comparable quality and concentration will be 

found. Nevertheless, analysis of the data on the 

2,401 stations in the Scripps Sediment Data Bank 

shows that there are several other areas that appear to contain metal-rich nodules, including some 

that might be high enough in combined nickel and 

copper (that is, 1.8 percent or more) to justify exploration for sites suitable for first-generation 

mining.

For the purpose of this analysis, the locations of 

stations falling into the metal types described in 

the preceding section were plotted on a world map 

(parts of which are reproduced in this report) as a 

basis for selecting areas in which nodules might 

contain 1 percent combined nickel and copper or 

more and that therefore seemed to deserve further 

study. The results, shown on the following pages, 

give some indication of areas that would seem 

favorable for further exploration. Because data on 

concentrations outside of the Clarion-Clipperton 

zone are few, no attempt has been made to 

estimate tonnage in other areas. Estimates of 

average grade and of size are given for several 

areas, but, because the data are sparse, these 

estimates must be taken as only a rough indication 

of what may be present in areas that, at this stage, 

are merely targets for exploration. Nor should it be 

concluded that the areas identified as warranting 

further study are the only ones that deserve further exploration. As the maps show, many other 

areas contain high-quality nodules, and further 

sampling might show some of these areas to be of 

minable size.

No consideration has been given here to further 

identifying exploration areas for nodules rich in 

cobalt or manganese. The data shown in figures 

16,17, and 18 do suggest, however, that there may 

be large areas in which such nodules might be

found. One of the striking results of this analysis as 

well as of others is that there appears to be considerable continuity in the combined nickel and 

copper content of manganese nodules over large 

areas, and this continuity may hold also for nodules 

rich in cobalt and in manganese. The data suggest, 

for example, that one or more such areas in which 

nodules contain more than 1 percent cobalt may be 

found in the north-central Pacific between 158° 

and 180° W. This region is the one within which 

Manheim and others reported cobalt-rich 

manganese oxide encrustations to "cover nearly 

the entire exposed surface of the seamounts 

studied" between depths of 2,500 and 1,200 m. 

Samples containing more than 35 percent 

manganese that have been reported along the 

eastern side of the Pacific basin (fig. 18) may be indicative of large areas of manganese-rich nodules.

Several areas in which nodules have high combined nickel and copper contents have been 

selected for further analysis; these areas are 

shown in figures 19, 20, and 21, along with the 

average combined nickel and copper contents for 

all stations within each area. These averages range 

from 0.72 percent combined nickel and copper in 

the South Atlantic to 1.56 percent in the central 

south equatorial Indian Ocean. Figures 22 through 

28 are enlarged maps of the same areas within 

which we have tried to delineate smaller areas of 

nodules containing more than 1.0 percent and 

more than 1.8 percent combined nickel and copper. 

Nodules containing lesser amounts have been included in these smaller areas where the average of 

that station and the ones adjacent to it is above the 

cutoff. It must be emphasized that areas thus delineated are significant only as targets for further exploration.

As figures 23, 24, and 27 show, fairly large 

target areas for nodules containing more than 1.8 

percent combined nickel and copper can be identified in the central north equatorial Pacific Ocean, 

the southeastern equatorial Pacific Ocean, and the 

central-south equatorial Indian Ocean. If nodule 

mining becomes possible, the rich resources of the 

Clarion-Clipperton zone will probably be large 

enough to support production for several decades. 

Some time in the distant future, however, it may 

be feasible to mine lower grade nodules; looking to 

that possibility, one can identify even larger areas 

in which the nodules contain >1.0 to <1.8 combined nickel and copper.

32
160°W. 140°W. 120°W. 100°W. 80°W. 60°W.

15

30°S.

45°S.

EXPLANATION

i0.861 Area selected for further study. + 5*1.8 percent NI + Cu 

Number is average NI + Cu ,«,-«% KI- , /- 

percentage at stations within study x 1 -°- 1 '79 percent Nl + Cu 

area n ^ 1.0 percent Co

A 5=35.0 percent Mn

FIGURE 19.-Distribution in the Pacific Ocean of manganese nodules having high metal contents.

As already mentioned, those target areas identified on the maps should not be thought the only 

ones worth considering. Others can be picked out 

from figures 14, 18, and 19. For example, a fairsized target for nodules containing more than 1.8 

percent combined nickel and copper appears to lie 

at 154° to 160° W., 1° to 3° S. in the South Pacific 

(McKelvey and Wright, 1980); on the basis of recent sampling, Exon (1982) identified this area and 

others in the central South Pacific between 

latitudes of 1° and 7° S. as having nodules of 

potential economic significance). The large area at 

124° to 160° W., 0° to 18° S. would be a target for

nodules containing more than 1.0 percent combined nickel and copper. Of course, further sampling may disclose other promising areas now 

unknown.

OTHER ELEMENTS IN MANGANESE 

NODULES

Some 51 other elements are present in the 

analysis of subsea manganese nodules entered in 

the Scripps Sediment Data Bank in addition to 

manganese, iron, nickel, copper, and cobalt. Data 

on these elements, summarized in tables 17

33
TABLE 17. - Other elements in manganese nodules of the world and of the Pacific, Atlantic, and Indian Oceans

[-, no data]

World

Li

Be

B

c

F

Na

Mg

Al _ 

Si

P

S

Cl

K

Ca

Sc

Ti

V _ 

Cr

Zn

Ga

Ge

As

Rb

Sr

Y

Zr

Nb

Mo

Ag

Cd

Sn

Sb

Te

I

Ba ___ _____ 

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

Hf

Ta

W

Hg

Tl

Pb

Bi

Th

No. of 

stations

19 

40 

86 

75 

2 

410 

531 

592 

509 

321 

106 

13 

490 

1,083 

76 

900 

437 

274 

1,363 

57 

4 

63 

32 

369 

134 

289 

68 

836 

7 

129 

141 

10 

17 

1 

463 

75 

72 

37 

38 

38 

36 

101 

32 

8 

9 

22 

1 

130 

1,246 

41 

121

Mean 

(percent)

0.010 

.001 

.029 

.327 

3.00 

1.97 

1.57 

2.70 

7.69 

.37 

.51 

.83 

.73 

2.23 

.005 

.69 

.052 

.007 

.12 

.001 

.004 

.014 

.002 

.085 

.015 

.057 

.007 

.038 

.001 

.001 

.008 

.005 

.022 

.250 

.23 

.021 

.072 

.026 

.004 

.001 

.001 

.003 

.000 

.001 

.002 

.010 

.000 

.016 

.093 

.002 

.003

Range 

(percent)

0.00-0.060 

.00-.010 

.002-.090 

.033-1.50 

3.00-3.00 

.30-6.55 

.02 5.39

11-8.00 

.24 28.80

.02-6.03 

.05-3.50 

.28-1.01 

.11-3.70 

.02-28.73 

.00-0.269 

.01-8.90 

.001-.500 

.000-.231 

.01-9.00 

.000-.007 

.000-.009 

.002-.048 

.000-.006 

.001-.285 

.002-.095 

.002-.360 

.001-.030 

.002-.220 

.000-.002 

.000-.003 

.000-.040 

.004-.005 

.017-.027

.000-2.14 

.009 .070

.009-.300 

.007-.070 

.002-.011 

.000-.002 

.000-.002 

.001-.010 

.000-.001 

.000-.001 

.000-.002 

.003-.060

.000-.061 

.01-.75 

.000 .009

.000-.013

Standard 

deviation

0.014 

.002 

.018 

.315 

0 

.82 

.63 

1.30 

4.12 

.77 

.71 

.17 

.45 

2.54 

.031 

.47 

.033 

.024 

.41 

.001 

.004 

.009 

.001 

.042 

.013 

.038 

.005 

.022 

.001 

.001 

.008 

.000 

.003

.21 

.012 

.059 

.014 

.002 

.000 

.000 

.001 

.000 

.000 

.001 

.011

.010 

.067 

.002 

.002

Pacific 

mean 

(percent)

0.02 

.001 

.030 

.342 

3.0 

2.05 

1.50 

2.75 

7.62 

.28 

.32 

.83 

.82 

1.96 

.005 

.73 

.051 

.009 

.116 

.001 

.004 

.011 

.002 

.084 

.015 

.061 

.007 

.041 

.001 

.001 

.010 

.005 

.022 

.25 

.235 

.022 

.069 

.027 

.004 

.001 

.001 

.003 

.000 

.001 

.002 

.008 

.000 

.017 

.083 

.003 

.003

Atlantic 

mean 

(percent)

0.025

.77

1.86 

1.75 

2.37 

6.34 

.91 

1.34

.57 

3.72 

.002 

.42 

.06 

.006 

.123 

.001

.02

.094 

.024 

.056 

.004 

.031

.001 

.007 

.004

.228 

.023

.003

.018 

.14 

.001

Indian 

mean 

(percent)

0.001 

.001 

.007 

.212 

3.0 

1.70 

1.43 

2.67 

9.39 

.37 

.83

.48 

1.97 

.001 

.62 

.054 

.002 

.149 

.001

.018

.079 

.011 

.034 

.007 

.029

.001 

.001

.21 

.018 

.125 

.011 

.004 

.001 

.001 

.001 

.000

.012

.008 

.101 

.001 

.003

through 20, follow the general structure adopted in 

the presentation of data on principal metals.

The world mean contents (table 17) of sodium 

(1.97 percent), magnesium (1.57), aluminum (2.70), 

silicon (7.69), and calcium (2.23) exceed 1.5 percent 

in the nodules; the sum of the oxides of these 

elements at their mean values is about 30 percent.

In the ^0.1- to < 1.5-percent range are the means 

of carbon (0.327 percent), phosphorus (0.37), sulfur 

(0.51), chlorine (0.83), potassium (0.73), titanium 

(0.69), zinc (0.12), and barium (0.23). The means of 

12 other elements (lithium, vanadium, strontium, 

yttrium, zirconium, molybdenum, tellurium, lanthanum, cerium, neodymium, and lead) are in the

34
20°E. 40°E.

20°S.

40°S.

60°S.

EXPLANATION

Area selected for further study. 

Number is average Ni + Cu 

percentage at stations within study 

area

+ ^*\& percent Ni + Cu 

X 1.0-1.79 percent Ni + Cu 

a SM.O percent Co

FIGURE 20.-Distribution in the South Atlantic Ocean of manganese nodules having high metal contents.

range of <0.01 to <0.1 percent. Although the 

mean concentrations of these elements in nodules 

are all much lower than those in the deposits from 

which they are mined on land, many represent 

substantial geochemical concentrations. For example, in comparison with the averages estimated by 

Lee and Yao (1970) for oceanic crust, the mean for 

zinc in nodules is 10 times greater, that for lead is 

93 times greater, and that for molybdenum is 253 

times greater. Even though their amounts are 

relatively small, some of these minor metals for 

which the price is relatively high conceivably might 

be recovered as byproducts in the extraction of 

nickel and copper.

Analyses available for other elements are fewer 

than those available for the metals previously

discussed. Given this limitation, it nevertheless appears that regional variations similar to those 

observed for the principal metals occur in the contents of some other elements. If only elements for 

which the station population in each ocean is 10 or 

more are considered, the means for phosphorus, 

calcium, and yttrium in Atlantic nodules are more 

than 20 percent higher than the world mean, and 

those for potassium and titanium are more than 20 

percent lower (table 17). The means for silica, 

arsenic, and cerium are more than 20 percent 

higher than the world mean in the Indian Ocean, 

and those for lithium, carbon, zirconium, potassium, molybdenum, and tin are more than 20 percent lower. Because stations in the Pacific are 

much more numerous than those in other oceans,

35
TABLE IS.-Means of other elements (in percent) in manganese nodules of ike world, grouped by latitude

[-, no data. Values set in italics are based on 10 stations or more]

Element

Li .

Be

B

C _

F _

Na

Me

Al

Si

P

S

Cl

K

Ca

Sc

Ti

V

Cr ____________ 

Zn

Ga __________ 

Ge

As ___________ 

Rb

 Sr

Y

Zr

Nb

Mo

Ag

Cd

Sn

Sb

Te

I

Ba _______ _ 

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

Hf

Ta

W

Hg 

Tl

Pb

Ri

Th

60°-40° N.

0.000

.028

.26

1.64

1.72

2.81

12.15

.26

.73

.57

2.19

.001

.53

.042

.004 

.06

.002

.01 

.003

.084

.028

.040

.005

.038

.000

.000

.291 

.018

.053

.018

.004

.001

.001

.002

.000

.010

.120

.001

.008

40°-20° N.

0.02

.000

.026

.29

1.87

1.61

2.61

7.04

.50

.51

.86

.71

3.30

.002

.66

.055

.012 

.12

.001 

.004

.019 

.003

.097

.016

.062

.009

.040

.001

.001

.005

.005

.022

.37 

.02

.10

ftay

.004

.001

.001

.003

.000

.001

.003

.018

.103

.003

.002

20° N.-0°

0.001

.000

.02

.22

3.0

1.84

1.57

2.58

742

.28

.26

.74

1.87

.023

.64

.046

.011 

.11

.001

.009 

nfti

.082

.015

.042

.004

.046

.001

.001

.25

.267 

.027

.058

.034

.006

.001

.001

.005

.000

.016

.067

.004

.002

0°-20° S.

0.001

.001

.029

.30

2.30

1.40

2.56

7.58

.18

.64

.83

2.07

.001

.76

.056

.001 

.13

.001 

.000

.016 

.001

.071

.015

.057

.010

.031

.001

.001

.004

.020

.173 

.020

.065

.020

.003

.001

.001

.003

.000

.002

.011

.000

.016

.09

.002

.003

20°-40° S.

0.001

.022

412

3.00

1.96

1.42

3.28

8.07

.47

.82

.90

.64

2 12

.003

.880

.049

.002 

.17

.002 

.009

.01*

.087

.013

.036

.004

.031

.002

.001

.010

.234 

.020

.126

.020

.004

.001

.001

.003

.000

.009

.014

.12

.002

.005

40°-60° S.

0.002

.043

.682

2.37

1.58

2.46

8.68

.86

.51

.28

.86

1.82

.002

.623

.059

.004 

.10

.001

.015

.082

.013

.072

.005

.037

.002

.009

.136 

.017

.045

.030

.004

.001

.002

.003

.000

.012

.14

.003

.004

60°-80° S.

_

_

1.96

2.64

3.18

13.83

.964

2.25

.639

.041

.06

-

.084

.073

.031

.008

.109

_

_

_

.16

they strongly influence the world mean for most 

elements, and significant departures from the 

world mean are not to be expected in Pacific 

nodules. Even so, the mean for chromium in 

Pacific nodules is 28 percent higher than the world 

mean (and 4.5 times higher than that in Indian 

Ocean nodules), and sulfur is 38 percent lower.

As for latitudinal variations (table 18), the means 

for magnesium and lead decrease toward the

equatorial region. Overall, but departing from the 

trend in one or more intermediate zones, so do the 

means for boron, carbon, aluminum, silicon, and 

calcium; the means for phosphorus, sulfur, 

chromium, and yttrium also decrease toward the 

equator in one hemisphere or the other. On the 

other hand, the means for potassium, titanium, 

vanadium, zinc, and molybdenum generally increase toward the equator, although there are

36
20°N40°E. 60°E. 80°E. 100°E. 120°E. 140°E.

20°S.

40°S.

60°S.

+ 

X

EXPLANATION

Area selected for further study. 

Number is average Ni + Cu 

percentage at stations within study 

area

3=1.8 percent Ni + Cu 

1.0-1.79 percent Ni + Cu

FIGURE 21.-Distribution in the Indian Ocean of manganese nodules having high metal contents.

some departures from the trend in intermediate 

latitudinal zones.

Again, if we compare only those elements that 

have been analyzed at 10 stations or more in 

populations above and below the 3,000-m depth 

(table 19), aluminum, silicon, potassium, scandium, 

and samarium are enriched in nodules below that

depth, and boron, phosphorus, sulfur, calcium, 

vanadium, chromium, arsenic, strontium, yttrium, 

tin, barium, cerium, and lead are enriched in 

nodules above it. Means for several other elements-for example, sodium, magnesium, zinc, zirconium, molybdenum, and lanthanum-are about 

the same in both groups.

37
TABLE 19. -Means of other elements in manganese nodules in 

water depths above and below 3,000 m

[ , no data]

< 3,000 m

No. of 

Elements stations

Li _ _

Be _____ 

B _ _

c

F

Na

Mg ____

Al 

Si

P

s

Cl ______ 

K

Ca

Sc __ _ 

Ti

V

Cr ______ 

Zn _ _ 

Ga _

Ge _ _

As

Rb

Sr _ _

Y _

Zr

Nb ______ 

Mo

Ag 

Cd

Sn ______ 

Sb _____ 

Te ______ 

I _ _

Ba

La

Ce _____ 

Nd

Sm

Eu _ _

Tb __ _ 

Yb

Lu

Hf

Ta ______ 

W _ _

Hg 

Tl _ _

Pb

Bi _ _

Th ______

5 

10 

33 

2 

1 

98 

125 

103 

94 

51 

12 

0 

119 

188 

21 

136 

68 

52 

188 

15 

0 

14 

0 

77 

36 

46 

15 

118 

0 

23 

19 

1 

0 

0 

63 

33 

15 

13 

13 

13 

11 

36 

13 

0 

0 

0 

0 

24 

197 

9 

13

Mean 

(percent)

0.001 

.001 

.040 

.91 

3.00 

1.83 

1.61 

1.72 

5.07 

1.148 

.85

.47 

4.65 

.001 

.76 

.071 

.015 

.11 

.001

.020

.122 

.024 

.057 

.005 

.045

.001 

.004 

.004

.34 

.022 

.087 

.021 

.003 

.001 

.001 

.004 

.000

.018 

.14 

.002 

.002

> 3,000 m

No. of 

stations

14 

30 

52 

68 

1 

310 

403 

478 

399 

265 

92 

13 

368 

883 

54 

748 

367 

221 

1,118 

41 

4 

47 

32 

290 

96 

239 

52 

710 

7 

102 

122 

8 

17 

1 

398 

42 

57 

24 

25 

25 

25 

64 

19 

8 

9 

22 

1 

101 

1,029 

31 

105

Mean 

(percent)

0.013 

.001 

.022 

.311 

3.00 

2.02 

1.553 

2.95 

8.29 

.22 

.43 

.83 

.81 

1.72 

.007 

.68 

.049 

.006 

.12 

.001 

.004 

.012 

.002 

.075 

.012 

.057 

.008 

.037 

.001 

.001 

.009 

.005 

.022 

.25 

.22 

.021 

.068 

.028 

.005 

.001 

.001 

.002 

.000 

.001 

.002 

.010 

.000 

.016 

.08 

.003 

.003

Examination of the distribution of other 

elements in nodules typed by their high contents of 

combined nickel and copper, manganese, and 

cobalt (table 20) indicates that several other 

elements follow these metals in their variations. 

The mean values of magnesium, aluminum, silicon, 

potassium, scandium, chromium, and zinc in the

> 1.8-percent combined nickel and copper groups 

are appreciably higher than those in the 

> 0.5-percent cobalt groups. The highest means for 

magnesium (1.87 percent), scandium (0.018), and 

chromium (0.013) are in the ^ 1.8-percent combined nickel and copper group, which also has the 

lowest mean values for sulfur (0.22 percent), 

calcium (1.59), titanium (0.47), strontium (0.06), 

yttrium (0.011), zirconium (0.049), lanthanum 

(0.013), cerium (0.035), and lead (0.048); the mean 

for vanadium (0.043) in this group is also appreciably lower than that in the ^ 0.5-percent 

cobalt group but is about the same as that in the 

>35.0-percent manganese group. The 

^ 0.5-percent cobalt groups have the highest 

means for phosphorus (0.531 percent), calcium 

(2.83), titanium (1.07), vanadium (0.069), strontium 

(0.14), yttrium (0.031), zirconium (0.072), lanthanum (0.027), cerium (0.133), and lead (0.26) and 

the lowest means for magnesium (1.337 percent), 

aluminum (0.71), silicon (2.00, at six stations only, 

however), potassium (0.32), and zinc (0.07). The 

> 35.0-percent manganese group has the highest 

means for sodium (2.77 percent, at 9 stations only), 

and barium (0.423) and the lowest means for phosphorus (0.120 percent, at 7 stations only), titanium 

(0.253), and vanadium (0.041, at 8 stations only); 

the mean for silicon (4.68 percent) in this group is 

appreciably lower than that in the high combined 

nickel and copper groups, and it is lower also than 

the silicon mean (5.18 percent) in the >0.5- to 

< 1.0-percent cobalt group.

Average contents of the other elements in 

Clarion-Clipperton zone nodules are essentially the 

same as those in ^ 1.8-percent combined nickel 

and copper group nodules-expectably so, because 

Clarion-Clipperton zone stations are the largest 

population within that group and strongly influence its mean values. The means for calcium 

(1.56 percent), vanadium (0.03), and zirconium 

(0.036) in Clarion-Clipperton zone nodules, 

however, are appreciably lower than those in the 

> 1.8-percent combined nickel and copper group; 

the mean for chromium (0.02) is appreciably 

higher.

Although the covariance of other elements with 

the principal metals in manganese nodules supports the idea that the metal groups described are 

geochemically distinct, the metal groups do not include the maximum values for several other elements-namely, titanium (8.9 percent), phosphorus (6.03), sulfur (3.50), potassium (3.70),

38
TABLE 20. - Other elements in manganese nodules grouped by combined nickel and copper, manganese, and cobalt contents

[-, no data]

> 1 .8 percent Ni + Cu 

No. of Mean 

stations (percent)

Li

Be

B

C

F

Na

Mg

Al

Si

P

S

Cl

K

Ca

Sc

Ti

V

Cr

Zn

Ga

Ge

As

Rb

Sr

Y

Zr

Nb

Mo

Ag

Cd

Sn

Sb

Te

I

Ba

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

Hf

Ta

W

Hg ______

Tl

Pb

Bi

Th

4

6

15

15

0

46

78

120

111

61

27

4

73

279

16

169

69

62

371

10

0

19

18

55

33

43

7

186

0

29

6

4

5

1

78

11

22

4

5

5

5

17

2

4

0

1

0

25

301

1

39

0.018 

.0002 

.02 

.23

2.02 

1.87 

2.65 

6.98 

.21 

.22 

.86 

.79 

1.59 

.018 

.47 

.043 

.013 

.14 

.002

.008 

.002 

.06 

.011 

.049 

.007 

.05

.002 

.010 

.004 

.024 

.25 

.288 

.013 

.035 

.021 

.003 

.001 

.001 

.002 

.000 

.001

.003

.02 

.048 

.001 

.002

>1.0-<1.8 percent

Ni+Cu

No. of 

stations

5 

12 

20 

22 

1 

67 

91 

111 

111 

70 

32 

5 

80 

191 

19 

169 

95 

55 

267 

16 

1 

14 

8 

80 

32 

55 

17 

175 

3 

28 

26 

4 

9 

0 

101 

15 

15 

7 

10 

10 

10 

22 

7 

4 

0 

2 

0 

24 

229 

9 

24

Mean 

(percent)

0.020 

.000 

.027 

.321 

3.00 

1.97 

1.57 

2.96 

8.26 

.288 

.319 

.860 

.86 

1.73 

.001 

.58 

.05 

.001 

.14 

.001 

.000 

.012 

.001 

.077 

.012 

.050 

.007 

.039 

.001 

.001 

.009 

.005 

.021

.224 

.019 

.066 

.023 

.004 

.001 

.001 

.002 

.000 

.001

.004

.013 

.071 

.002 

.003

^ 35.0 percent 

Mn

No. of 

stations

0 

0 

6 

1 

0 

9 

9 

11 

11 

7 

3 

0 

10 

14 

3 

16 

8 

5 

11 

4 

0 

1 

0 

8 

5 

6 

1 

13 

0 

0 

1 

0 

0 

0 

10 

1 

0 

0 

0 

0 

0 

5 

0 

0 

0 

0 

0 

1 

19 

0 

1

Mean 

(percent)

0.016 

.93

2.77 

1.67 

2.09 

4.68 

.120 

.547

.72 

1.64 

.001 

.253 

.041 

.001 

.08 

.001

.002

.070 

.007 

.033 

.001 

.056

.009

.423 

.018

.002

.000 

.09

.005

> 1.0 percent 

Co

No of 

stations

0 

0 

5 

0 

0 

7 

8 

12 

6 

4 

1 

0 

8 

11 

4 

16 

9 

3 

12 

1 

0 

1 

0 

7 

5 

6 

1 

11 

0 

1 

2 

0 

0 

0 

8 

6 

2 

2 

2 

2 

1 

6 

2 

0 

0 

0 

0 

2 

12 

2 

1

Mean 

(percent)

0.041

1.99 

1.47 

.71 

2.00 

.32 

1.2

.32 

2.72 

.001 

1.07 

.069 

.002 

.07 

.002

.027

.14 

.031 

.072 

.007 

.060

.000 

.022

.333 

.024 

.133 

.032 

.005 

.001 

.000 

.005 

.001

-

.037 

.26 

.003 

.001

s0.5-<1.0 

percent Co

No. of 

stations

2 

6 

9 

2 

1 

37 

47 

46 

39 

23 

3 

0 

43 

81 

8 

80 

34 

28 

85 

4 

0 

7 

3 

27 

14 

18 

7 

63 

0 

15 

5 

0 

1 

0 

39 

13 

10 

5 

4 

4 

4 

12 

4 

0 

0 

0 

0 

15 

95 

4 

10

Mean 

(percent)

0.000 

.001 

.032 

.080 

3.0 

1.80 

1.337 

1.81 

5.18 

.531 

1.199

.49 

2.83 

.001 

1.01 

.064 

.001 

.14 

.001

.016 

.001 

.119 

.021 

.061 

.006 

.048

.001 

.004

.021

.286 

.027 

.098 

.034 

.006 

.001 

.001 

.004 

.000

.020 

.17 

.003 

.003

calcium (28.73), scandium (0.269), vanadium (0.5), 

zinc (9.00), molybdenum (0.220), barium (2.14), lanthanum (0.07), cerium (0.30), yttrium (0.095), 

neodymium (0.07), and lead (0.75). Because many 

of these maximums are an order of magnitude or 

more larger than the means, one might suspect

that they are simply erroneous. That this explanation may not be valid, however, is suggested by the 

fact that their maximums in each ocean are also 

much higher than the world mean (table 21). For 

example, the world maximum for titanium comes 

from the Pacific, but the highest values in the

39
40°N180°W. 170°W. 160°W. 150°W. 140°W. 130°W. 120°W.

-TVEXPLANATION

-j- 2* 1.8 percent Ni + Cu

X 1.0-1.79 percent Ni + Cu 

D 2*1.0 percent Co 

0.5-0.99 percent Co

<1.0 percent Ni + Cu,<0.5percent Co

Area within which Ni + Cu2*1.0 

percent (4,900,000 km2 ; 50 stations; 

average 1.25 percent Ni+Cu)

FIGURE 22.-Target areas for exploration for manganese nodules rich in combined nickel and copper in the central northeastern

Pacific Ocean.

TABLE 21.- World means and ocean maximums (in percent) of 

several other elements in manganese nodules that have exceptionally high concentrations

[-, no data. Values in italics are based on fewer than 10 samples]

World Maximum

p

s

K

Ca

Ti

Sc

V

Cr

Zn

Y

Mo

Ba

La

Ce

Nd

Pb

mean

0.37

.51

.73

2.23

.69

.005

.052

.007

.12

.015

.038

.23

.021

.072

. _ .026

.093

Pacific

5.12 

1.90 

3.70 

24.0 

8.90 

.269 

.500 

.231 

7.00 

.095 

.220 

1.65 

.070 

.300 

.070 

.46

Atlantic

6.03 

2.50 

2.71 

28.73 

2.03 

.004 

.15 

.017 

8.00 

.071 

.177 

.800 

.033

.40

Indian

4.42 

3.50 

.65 

14.93 

1.76 

.001 

.102 

.013 

9.00 

.038 

.066 

2.14 

.029 

.300 

.015 

.75

Atlantic and Indian Oceans are 2.03 and 1.76 percent, respectively. The maximum for zinc is from 

the Indian Ocean, but the high values in the Atlantic and Pacific Oceans are 8.0 and 7.0 percent, 

respectively. It seems possible, then, that types of

metal-rich nodule groups other than those discussed here may exist and that some of them may 

have potential economic value.

The Scripps Sediment Data Bank had no 

analyses for platinum metals and gold in manganese nodules as of March 1980. In 1932, V. M. 

Goldschmidt and C. Peters (see Goldschmidt, 

1954), however, reported 0.5, 0.2 and 0.2 ppm 

platinum, palladium, and rhodium, respectively, in 

a nodule from Challenger Station No. 286 in the 

southeastern Pacific (133°22' W., 33°29' S.) Harriss and others (1968) determined palladium, irridium, and gold values in several nodules and 

found ranges of 0.24 to 9.25, 0.90 to 23.1, and 0.21 

to 8.28 ppb, respectively. Although individual 

analyses thus vary considerably, the average for 

each metal is similar for both Atlantic and Pacific 

nodules, and no correlation with any other major 

and trace metals was found.

Recently, P. J. Aruscavage (see Flanagan and 

Gottfried, 1980) determined platinum, palladium, 

and ruthenium values for the two nodule samples 

used by the U.S. Geological Survey as standard 

samples. The one from the Clarion-Clipperton zone 

(at 124°28'W., 14°50'N.) contains 123,5.6, and 4.7 

ppb of platinum, palladium, and ruthenium, respec40
180°W. 

20°N.

170°W. 160"W.

10°N.

EXPLANATION 

~\~ 3*1.8 percent Ni + Cu 

X 1.0-1.79 percent Ni + Cu 

D 3*1,0 percent Co 

^ 0.5-0.99 percent Co 

o <1.0 percent Ni + Cu, <0.5 percent Co

-""^ Area within which Ni + Cu3*1.8 percent 

'--" (240,000 km2 ; 27 stations; average 2.0 

percent Ni + Cu)

Area within which Ni + Cu3*1.0 percent

FIGURE 23. -Target areas for exploration for manganese nodules rich in combined nickel and copper in the central north equatorial

Pacific Ocean.

tively, and the one from the Blake Plateau (at 

78°22' W., 31°02' N.) contains 453,2.5, and 18 ppb, 

respectively. Analyses of 12 other nodules from the 

western Atlantic (Manheim and others, 1980) show 

that iron-enriched nodules from seamounts have 

the lowest platinum values, the maximum being 

120 ppb. Elements best correlated with platinum in 

these samples are nickel and cadmium. The 

rhodium control of these samples ranges from 2 to 

30 ppb.

Because so few samples have been analyzed for 

precious metals, nothing can be said about their 

geographic or geochemical distribution. If the few 

data available are reliable, they do suggest that the 

concentrations of silver in the nodules and of the 

metals that are commonly associated with gold in 

its ores (antimony, tellurium, and bismuth) are 

geochemically remarkable, even though the actual 

amounts are small. The world means for silver, antimony, tellurium, and bismuth in the nodules 

(table 17) are 0.001, 0.005, 0.022, and 0.002 percent, respectively, and represent concentration 

factors above the averages in oceanic crust (according to Lee and Yao, 1970) of 110, 55, 250,000, 

and 200, respectively.

Interest in recovering metals from subsea manganese nodules has thus far focused on nickel, copper, cobalt, and (on the part of a few companies) 

manganese. In seems possible, however, that some 

other elements-molybdenum and vanadium, for 

example-may also prove to be recoverable as 

coproducts, particularly if hydrometallurgical 

processes are used to concentrate the metals.

GENETIC IMPLICATIONS OF VARIATIONS IN 

COMPOSITION OF MANGANESE NODULES

The observations made in this analysis must be 

explainable under any comprehensive theory of the 

origin of subsea manganese nodules. Before we 

review existing theories, it would be useful to summarize salient features that require explanation:

1. The differences in the metal contents of nodules 

in the different ocean basins, the high concentration of nodules rich in combined nickel and 

copper on the eastern sides of the ocean 

basins and of those rich in cobalt on the 

western sides of the Pacific and Indian

41
100°W. 90°W. 80°W.

10°S

20°S

EXPLANATION

-|- ^1.8 percent Ni + Cu

X 1.0-1.79 percent Ni + Cu

A 3=35.0 percent Mn

<0> 0.5-0.99 percent Co

<1.0 percent Ni + Cu, 

<35.0 percent Mn, 

<0.5 percent Co

Area within which Ni + Cus=1.8 percent 

(815,000 km2 ;12 stations; average 2.11 

percent Ni + Cu)

Area within which Ni + Cus*1.0 percent

FIGURE 24. -Target areas for exploration for manganese nodules rich in combined nickel and copper in the southeastern equatorial

Pacific Ocean.

Oceans, and the occurrences of nodules containing more than 35 percent manganese 

mainly on the eastern side of the Pacific basin 

and those high in iron on the western side.

2. The relation between metal content and latitude, including the concentration of nodules 

high in cobalt and iron between 20° and 40° 

latitude in both hemispheres.

3. The relation of nickel, copper, cobalt, and iron 

to water depth.

4. The relation of nodule abundance to depth.

5. The great complexity in the chemical composition of the nodules, which contain nearly 60 

elements, many of which are present in concentrations many times larger than their 

averages in oceanic crust and several of which 

are present in local concentrations many 

times larger than their world means.

Although iron is one of the major constituents 

of the nodules, it is less abundant in those 

nodules richest in other metals, such as the 

nodules in the Clarion-Clipperton zone, than 

it is in average oceanic crust.

6. The existence of essentially nonoverlapping 

nodule types defined by their high contents of 

combined nickel and copper, cobalt, and manganese but also showing consistent differences in their contents of many other 

elements.

7. The high positive correlations of cobalt with 

iron, nickel with copper, and combined nickel 

and copper with manganese and with the 

manganese-iron ratio and the negative correlation of cobalt with nickel, copper, and 

manganese, except where the cobalt contents 

are in the highest range.

42
100°W. 90°W. 80°W. 70°W.

31°S.

Area within which Ni + Cu^LO percent 

(490,000km2 ; 5 stations; average 1.76 

percent Ni + Cu)

41 °S.

EXPLANATION 

-f" 3=1-8 percent Ni + Cu 

X 1.0-1.79 percent Ni + Cu 

A 5=35.0 percent Mn

o <1.0 percent Ni + Cu,<35.0 percent Mn, 

<0.5 percent Co

FIGURE 25.-Target area for exploration for manganese nodules rich in combined nickel and copper in the central southeastern

Pacific Ocean.

8. The strong inverse relation between concentration and combined nickel and copper content 

in nodules containing > 1.0 percent combined 

nickel and copper and the weak relation between concentration and grade in the ClarionClipperton zone.

RELATION OF METAL CONTENT TO 

MINERALOGY

Many of the variations in the chemical compositions of nodules are reflected in their mineralogies. 

Study of these mineralogies is difficult because 

most component particles are submicroscopic, but 

much progress has been made, beginning with the 

pioneering X-ray diffraction studies of Buser and 

Grutter (1956). They described three manganese 

oxide minerals in the nodules by identifying their 

X-ray patterns as those of synthetic analogues and 

named them 10-A manganite, 7-A manganite, and 

6Mn02. They also identified the ferric oxyhydroxide mineral goethite as a component of the nodules. 

Subsequent workers (for example, Straczek and 

others, 1960; Hewett and others, 1963; Manheim, 

1965; Cronan and Tooms, 1969) correlated the

10-A manganite with todorokite and the 7-A 

manganite with birnessite. Controversey has 

developed over the terminology used to describe 

the manganese minerals and indeed over the question of whether they are valid minerals (see Burns 

and Burns (1977) for a review), but there seems to 

be no disageement over the existence of the three 

phases. Most authors, following the recommendations of Burns and Burns (1977), have referred to 

them as todorokite, birnessite, and 6Mn02. 

Chukhrov and others (1979), however, recently 

proposed that the 6Mn02 phase be called vernadite. 

Burns and Burns (1979) accepted that proposal, 

and that usage is adopted here. Although goethite 

has been reported by some other investigators, the 

iron phase is generally believed to be amorphous 

hydrated ferric oxide (Burns and Burns, 1977; 

Bischoff and others, 1981).

All three of the manganese minerals may be 

present in individual nodules, but it appears that 

vernadite is present in most of them. Birnessite is 

less common and generally occurs only where the 

other two are present (Barnes, 1967; Piper and 

others, 1979; Bischoff and others, 1981). The vernadite phase is extremely fine grained, and, when

43
150°W 

36°S.

140°W. 130°W.

46°S.

120°W.

+

X

D

EXPLANATION 

3*1.8 percent Ni + Cu 

1.0-1.79 percent Ni + Cu 

3*1.0 percent Co

<1.0 percent Ni + Cu, <0.5 percent Co, 

<35.0 percent Mn

Area within which Ni + Cus*1.0 percent 

(1,300,000 km 2 ; 21 stations; average 

1.4 percent Ni + Cu)

FIGURE 26.-Target area for exploration for manganese nodules rich in combined nickel and copper in the central South Pacific

Ocean.

it occurs in nodules, it contains admixed amorphous iron hydroxide and extremely fine grained 

silicate minerals (Usui, 1979; Halbach and Ozkara, 

1979), including some of extraneous origin. 

Recently, Bischoff and others (1981) have shown 

that the mineral phillipsite-(K, Na, Ca^-a (Si, 

Al)8Oi6 'H20, according to Fleishcher (1980)-is 

also ubiquitous in the nodules, forming in place on 

the growing nodules, as the manganese minerals 

and amorphous iron hydroxide do. They suggested, 

in fact, coupled and mutually catalytic reactions in 

which the alteration of phillipsite from volcanic 

glass locally raises the pH and stimulates the oxidation of Mn*2, which, in turn, releases the 

hydrogen required in the formation of phillipsite. 

Abundant evidence has accumulated to show 

that variations in the contents of these minerals 

are reflected in variations in bulk nodule chemical composition. Todorokite-(Mn*2 , Ca, 

Mg)Mn*4 07 *H2 0), according to Fleischer 

(1980)-has a structure that includes sites in which 

small divalent cations, such as nickel, copper, 

magnesium, and zinc, can replace Mn*2 and other 

sites that will accommodate large cations such as 

potassium. Birnessite-Na4Mn14027*H20, according to Fleischer (1980)-apparently has somewhat 

similar properties (Burns and Burns, 1977). It is 

the nodules rich in todorokite and birnessite that 

are rich in nickel and copper and the other minor 

metals previously described as most abundant in 

the 5: 1-percent combined nickel and copper type 

(Burns and Fuerstenau, 1966; Barnes, 1967; 

Cronan and Tooms, 1969; Tooms and others, 1969; 

Margolis and Burns, 1976; Piper and Williamson, 

1977; Calvert and Price, 1977; Halbach and 

Ozkara, 1979; Usui, 1979; Piper and others, 1979; 

Cronan, 1980; Bischoff and others, 1981). It is also 

the todorokite-rich nodules that have a manganeseiron ratio of >1.5 (Margolis and Burns, 1976;

Piper and Williamson, 1977; Calvert and Price, 

1977; Halbach and Ozkara, 1979). On the basis of 

microprobe analyses of individual layers of 

todorokite and the 6Mn02 phase (including the 

amorphous iron) in nodules from the north-central 

Pacific, Usui (1979) found several of the elements 

that he examined partitioned between the two 

phases by grade such that concentrations of 

manganese greater than 30 percent, of both copper 

and nickel greater than 0.8 percent, of magnesium 

greater than 0.8 percent, of potassium greater 

than 0.6 percent, and of sodium greater than 0.5 

percent are in the todorokite phase, and concentrations below those values are mostly, if not entirely, 

found in the vernadite phase. Amounts of iron 

greater than 4 percent and of silica greater than 

1.2 percent are restricted to the 6Mn02 (vernadite) 

phase. Cobalt has about the same range in both 

phases, but most of the concentrations greater 

than 0.3 percent are in the 6Mn02 phase, and most 

below that value are in todorokite. Although a 

number of authors have reported a positive correlation between cobalt and iron, Usui found a 

positive correlation of cobalt with manganese and 

concluded that'trivalent cobalt is substituting for 

manganese in the vernadite phase and that some 

divalent cobalt may substitute for manganese in 

the todorokite phase (10-A manganite in his terminology). Burns (1976) made a similar proposal 

and suggested that the formula for 6Mn02 (vernadite) should be (Mn, Co*3)Mn6Ol3 -*H20. Halbach 

and Ozkara (1979) reported similar findings in 

studies of nodules from an area within the ClarionClipperton zone. Nodules consisting mainly of 

todorokite contain 23 to 32 percent manganese, 2 

to 3.2 percent combined nickel and copper, 0.1 to 

0.2 percent cobalt, and less than 7 percent iron; 

those consisting mainly of vernadite contain 16 to 

24 percent manganese, 1.0 to 1.6 percent combined

44
70°E. 80°E.

10°S.

20°S.

X

X

EXPLANATION 

5=1.8 percent Ni + Cu 

1.0-1.79 percent Ni + Cu

<1.0 percent Ni + Cu, <0.5 percent Co, 

<35.0 percent Mn

Area within which Ni + Cu^1.8 percent 

(270,000 km2 ; 12 stations; average 2.3 

percent Ni + Cu)

Area within which Ni + Cus= 1.0 percent

FIGURE 27. -Target areas for exploration for manganese nodules rich in combined nickel and copper in the central south equatorial

Indian Ocean.

nickel and copper, 0.25 to 0.40 percent cobalt, 

more than 1 percent titanium dioxide, and more 

than 9 percent iron and have a manganese-iron 

ratio of 2.5 or less.

Bischoff and others (1981) believed that 

titanium, phosphorus, and some silica are 

associated with the amorphous iron phase, and 

Calvert and Price (1977) showed a similar correlation of arsenic, yttrium, lead, strontium, and cobalt 

with iron. Even though the amorphous iron 

hydroxide is physically a part of the vernadite 

phase in the nodules, its content varies independent of the vernadite content. Variations in the 

chemistries of the nodules are thus best 

understood as variations in their contents of 

authigenic todorokite-birnessite, vernadite, amorphous iron hydroxide, and phillipsite, along with 

clay and other siliceous minerals of extraneous 

origin. To illustrate compositional variations in the 

authigenic components of nodules, Bischoff and 

others (1981) used a ternary diagram in which all of 

the manganese phases are lumped together and 

plotted against the phillipsite and amorphous iron 

phases. Figure 29 follows this design and shows an 

almost complete gradation of mineral composition 

within the ranges of about 4 to 55 percent 

manganese oxide phases, 7 to 37 percent amorphous iron phase, and 7 to 60 percent phillipsite 

phase.

Given the mineralogy of the nodules, it is easy to 

understand the concentration of so many of the 

chemical elements. Not only does the structure of 

todorokite favor the incorporation of many 

elements, but also both iron and manganese oxides 

are well known for their abilities to scavenge other 

metals from seawater by physical adsorption 

(Goldberg, 1954). It is also easy to understand 

variation in metal content as a function of 

mineralogy, at least in large part. But to what factors do variations in the proportion of mineral 

phases relate?

RELATION TO WATER DEPTH

Barnes (1967), Cronan (1967), Cronan and 

Tooms (1969), and Piper (1972) found that the relation between metal content and depth is also a 

function of the mineralogy of the nodules, 

todorokite being more abundant in deeper water 

nodules and vernadite being dominant in nodules 

from shallower depths. The three manganese oxide 

phases represent different degrees of oxidation of 

manganese, and Cronan and Tooms (1969) concluded that variations in the mineralogy of nodules

45
95°E. 

31°S.

105°E.

41 °S.

EXPLANATION 

X 1.0-1.79 percent Ni + Cu

° <1.0 percent Ni-i-Cu, <0.5 percent Co, 

<35 percent Mn

Area within which Ni + Cus* 1.0 percent 

(300,000 km2 ; 15 stations; average 

1.35 percent Ni + Cu)

FIGURE 28. -Target area for exploration for manganese nodules 

rich in combined nickel and copper in the southeastern Indian 

Ocean.

with depth may reflect variations in the degree of 

oxidation of the environment of deposition. Piper 

and Williamson (1977) found support for this 

theory in the fact that the few nodules containing 

more than 0.5 percent cobalt that occur in water 

depths greater than 3,000 m are from the area immediately to the west of the Line Island Ridge, 

where there is a major intrusion of highly oxidizing 

Antarctic bottom water.

Cronan (1980) related the increase in the combined nickel and copper content of nodules that 

takes place at a depth of about 3,000 m to the 

lysocline-the depth at which calcium carbonate in 

organic remains begins to dissolve and to liberate 

metals, particularly copper, concentrated by 

organisms. Because copper is more concentrated 

in the skeletons of many organisms than nickel is 

(Halbach and others, 1979), this process would also

explain the fact that copper-nickel ratios in shallow-water nodules are lower than those in deepwater nodules. (See Heath (1981) for a review of 

the importance of surface plankton in the concentration of metals.)

EFFECTS OF DIRECT PRECIPITATION FROM SEAWATER 

IN COMPARISON WITH DIAGENETIC PRECIPITATION

Another factor that may explain differences in 

nodule mineralogy involves the source and manner 

of deposition of their components. Rabb (1972) 

found that many nodules have a smooth upper surface and a gritty, lumpy bottom. Separate analyses 

of tops and bottoms showed that the tops are high 

in iron, cobalt, and lead and low in copper, nickel, 

molybdenum, zinc, and manganese and that the 

reverse is true for the bottoms. Calvert and Price 

(1977), Halbach and Fellerer (1980), Piper and 

others (1979), and Usui (1979) have suggested that 

the upper surfaces of such nodules (shown to be 

composed of vernadite) represent precipitate 

derived directly from seawater and that the bottoms (todorokite) represent a diagenetic 

precipitate by leaching of the underlying sediment. 

Concentrations of manganese, copper, nickel, 

cobalt, and zinc in the interstitial water of deep-sea 

sediments have been found to be higher than those 

in deep seawater, and Lynn and Bonatti (1965) and 

others (Bender, 1971; Renard and others, 1976) 

proposed that Mn*4 in the sediments is reduced to 

Mn*2 under low Eh conditions (perhaps created in 

part by the oxidation of buried organic matter, as 

Price and Calvert (1970) suggested), dissolved, carried upward, and precipitated under the oxidizing 

conditions prevailing at or near the surface. Nickel 

and copper also go into solution in this process 

(Piper and others, 1979). In the redox potential 

range in the sediment, the solubility of iron oxide is 

not affected, and it remains in the sediment (Borchert, 1970, referred to by Halbach and Ozkara, 

1979; Cheney and Vredenburgh, 1968, referred to 

by Usui, 1979). The sediment thus represents the 

residue resulting from diagenesis (Piper and 

others, 1979).

Some nodules (Halbach and Ozkara's (1979) type 

A and Usui's (1979) type B) contain little or no vernadite and are explained as having formed within 

the sediment just beneath the surface. Halbach and 

Ozkara also found nodules (iheir type B) composed 

entirely of vernadite on the flanks of a seamount 

within the area that they studied. They found that, 

in contrast to the todorokite nodules, in which the

46
MnO + MgO + NiO + CuO AI203 + K2O + Na2O + SiO2

FIGURE 29. -Ternary plot of the principal mineral phases (normalized to total 100 percent) of manganese nodules at the 107 stations 

in the Scripps Institution of Oceanography's Sediment Data Bank for which analyses of all the constituents shown have been 

made. Compositions shown for the metal types are based on means.

nucleus is generally a fragment of a preexisting 

nodule, the vernadite nodules generally have a 

rock nucleus. They translate the findings of Heye 

and Marchig (1977)-that nodule growth rate increases with increasing manganese, nickel, and 

copper contents-to conclude that the growth 

rates of todorokite nodules and layers are 10 to 15 

times greater those of vernadite (see also Piper 

and Williamson, 1977), which they and Usui believed is deposited from a colloidal form in nearbottom seawater rather than from an ionic solution 

of Mn+2 , as todorokite is.

M. Lyle (unpublished 1978 thesis, referred to by 

Heath, 1981), confirming Heye and Marchig's 

(1977) finding, observed an inverse ratio between 

nodule growth and iron content and suggested 

that, in areas of very low productivity, growth is 

slow and is controlled by precipitation from

seawater. In areas of oxic diagenesis, the rate of 

growth increases with increasing biologic productivity in surface water. "As the rate of input of 

organic debris increases to the level at which anoxic diagenesis begins... the mobilization of Mn 

under anoxic conditions results in rapid nodule 

growth that virtually swamps the input of other 

metals, leading to lower Cu and Ni contents" 

(Heath, 1981, p. 757). This process, Heath believed, 

explains the high manganese content of the 

nodules in the hemipelagic sediment along the 

eastern margin of the Pacific.

The three types of nodules described by Halbach 

and Ozkara are all from within a relatively small 

area in which the water depths range from 4,600 m 

at the summit of a seamount to 5,200 m on the surrounding ocean floor. The presence of both 

todorokite and vernadite in the same nodules in47
dicates that both minerals may form in the same 

macroenvironment. Halbach and Ozkara believed 

that the type formed is governed by topography, 

the availablity of rock fragments to serve as nuclei, 

local sedimentation rate, and bottom-current activity; vernadite forms as nodules or as crusts on 

rock surfaces where no sediment has accumulated 

or on the tops of nodules exposed to seawater, and 

todorokite forms at or near the surface of the sediment, which is largely radiolarian ooze in the 

southern part of the Clarion-Clipperton zone and 

red clay in the northernmost part. Nodules containing adjacent laminae of both minerals (the A 

type of Usui and the AB type of Halbach and 

Ozkara) reflect merely a change in the nodule's exposure to seawater-for example, burial by sediment to deposit todorokite on top of vernadite or a 

winnowing away of enough sediments to uncover a 

nodule forming near the bottom surface. Local 

variations in nodule content within the ClarionClipperton zone-in which the todorokitevernadite nodules are most common (Halbach and 

Ozkara, 1969)-may thus reflect differences in the 

todorkite contents of the nodules as a result of 

local variations in their exposure to seawater. 

Cronan (1977), however, pointed out that, although 

the presence of todorokite is a probable prerequisite for the enrichment of nickel and copper in 

the nodules, it is not the only factor, for some 

todorokite-rich nodules outside the North Pacific 

have lower contents of these metals.

The great concentration of manganese with 

respect to iron in Clarion-Clipperton zone nodules 

is thus explained as a diagenetic mobilization of 

manganese in sediments in which the iron, 

although it is several to many times more abundant 

than manganese, remains fixed. More puzzling is 

the fact that, in the vernadite-amorphous iron 

phase apparently formed by colloidal precipitation 

from seawater, the manganese-iron ratio, although 

averaging only about 1.5 according to Usui's 

analyses, is the reverse of what it is*in seawater. 

For whatever reason, proportionately more iron 

than manganese leaves seawater in some other 

way.

This fact leads to other interesting questions: 

why do the iron and manganese phases occur 

together, and why do they commonly occur as 

nodules? As Halbach and Ozkara (1979) and others 

indicated, they occur as encrustations on bedrock 

where nucleating grains are absent. The tendency 

for extremely fine grained particles to form aggregates is common in many other kinds of 

materials; Ramberg (1952) attributed this tendency to differences in surface energy that lead to a 

lower free energy in clusters rather than in 

disseminated form. The scarcity of ironmanganese minerals indicates that iron and 

manganese have little chemical affinity, but Burns 

and Burns (1977, p. 246) pointed out that, 

"although Mn02 and Fe OOH x H20 consist of 

very small disordered crystallites, both phases contain cations in octahedral sites of hexagonally 

close-packed oxygen layers. Therefore, these two 

phases in manganese nodules are highly susceptible to epitaxial intergrowth [that is, oriented intergrowth of one phase on the other where lattice 

parameters or interplanar spacings are similar] 

which probably initiates nucleation and leads to the 

intimate association of manganese and iron oxide 

phases." As mentioned earlier, Bischoff and others 

(1981) thought that the other main constituent of 

manganese nodules, phillipsite, may form as a 

coupled reaction with the manganese oxides. It 

thus appears that there are good reasons for these 

chemically distinct phases to occur together in the 

nodules.

Because both todorokite and vernadite phases 

may form in the same macroenvironment, it would 

seem that, of the factors previously proposed as affecting the composition of the nodules, hydrostatic 

pressure (Barnes, 1967), dissolved oxygen (Cronan 

and Tooms, 1969), and pH-Eh conditions within 

the abyssal aqueous environments (Crerar and 

Barnes, 1974) do not control the deposition of 

todorokite versus vernadite or the ratio between 

the two. Such physicochemical factors, however, 

may influence their contents of minor elements. 

The enrichment in the cobalt contents of nodules 

from shallow depths, for example, has been ascribed to oxidation from Co*2 to Co*3 under the 

highly oxidizing conditions prevailing on seamounts and similar features (Goldberg, 1961; 

Burns, 1965; Cronan and Tooms, 1969; Piper and 

Williamson, 1977), and Goldberg (1965) suggested 

a similar effect with respect to lead. The wide 

variations in the nickel and copper contents of 

todorokite (Usui, 1979) may be due in part to variations in physicochemical factors.

RELATION TO REGIONAL VARIATIONS IN SEDIMENT 

TYPE, BIOLOGIC PRODUCTIVITY, AND

PHYSIOGRAPHY

Because of the importance of sediment 

diagenesis in the formation of todorokite, which

48
has a high manganese-iron ratio and generally high 

nickel and copper contents, regional variations in 

sediment character should be examined as a possible source of regional variations in nodule composition. Piper and Willilamson (1977) found that, in 

the Pacific, the relation between the manganeseiron ratio of nodules and latitude is almost the 

reverse of the relation between the manganeseiron ratio of sediments and latitude (sediment data 

from Skornyakova (1965)). In nodules, manganeseiron ratios are in the range of 6 to 9 near 10° N. 

and 10° S. and diminish to about 2 in the equatorial 

region and to less than 1 north and south of the 20° 

parallels. In sediments, the high manganese-iron 

ratio is about 0.7 in the equatorial region, and the 

lows of 0.01 to 0.03 are in the 10° N. and 10° S. 

regions. On the basis of a comparison with 

Lisitzin's (1972) map showing sedimentation rates 

for the Pacific, Piper and Williamson suggested 

that nodules having high manganese-iron ratios 

tend to occur in areas where sediment accumulation is slow.

Although Skornyakova (1979) found no correlation between the manganese, nickel, copper, and 

cobalt contents of nodules and associated sediment, she broadly related changes in nodule composition to sediment lithology. In the northern 

Pacific, for example, she observed that nodules 

having the highest average manganese, nickel, 

copper, and zinc concentrations are associated 

with the radiolarian ooze of the equatorial belt and 

decrease successively in the adjacent zones of the 

miopelagic clay, eupelagic clay, and calcareous 

ooze. She attributed the differences in the iron and 

manganese contents of nodules on the eastern and 

western sides of the Pacific to differences in 

primary manganese contents during sedimentation; sediments on the west are initially poor in 

manganese and those on the east are richer 

because of the presence of only a thin oxidized 

layer of sediment. She related the composition of 

nodules in the equatorial belt to the high organic 

productivity associated with the equatorial currents, which cause the diagenetic migration of the 

metals as buried organic matter oxidizes, and to 

slow deposition of sediment because of highvelocity bottom currents. Heath (1981) also related 

the metal content of the nodules to sediment type 

and, in turn, to biologic productivity in the overlying waters.

The zone of highest organic productivity in the 

equatorial region of the Pacific lies 50 to 100 km

south of, rather than above, the zones in which 

nodules are richest in nickel and copper. Exon 

(1981, p. 61) suggested that this zone is a result of 

northwestward movement of the Pacific plate in 

this region at a rate of about 100 km/m.y.: ''Assuming that the high productivity zone has not moved 

much (relative to the equator) in the past 10 million 

years, the time during which the nodules probably 

formed, they would have been beneath the high 

productivity zone for much of their growth."

Several other investigators (Arrhenius, 1963; 

Greenslate and others, 1973; Margolis and Burns, 

1976; Piper and Williamson, 1977; Cronan, 1977) 

also have suggested that organic productivity 

plays an important role in concentrating some of 

the nodule metals and transporting them to the 

bottom and, when such metals are buried by sediment, in creating the reducing environment that 

lead to their diagenetic mobilization and subsequent deposition at the surface. According to 

Glasby (1981, p. 4), "On a regional scale, the most 

important factor controlling the composition of 

South Pacific abyssal nodules is the biological productivity of the overlying surface sea water." 

Nodule abundance in that area, he reported, is inversely related to sedimentation rate-a factor 

that Piper and others (1982) considered to be of 

primary importance in the distribution of nodules 

over the Pacific basin as a whole (see also Menard, 

1976).

Greenslate (1975), Wendt (1974), and Margolis 

and Burns (1976) reported the widespread 

presence of sessile arenaceous foraminifera on the 

nodules. Margolis and Burns found that, whereas 

foraminifera are present on nodules from all 

latitudes, they are most abundant and most diverse 

on nodules from the Clarion-Clipperton zone. The 

iron, titanium, and cobalt contents of foraminiferal 

tubes are higher than those of the nodule surface 

on which they are growing, and the manganese, 

nickel, and copper contents are lower. Margolis 

and Burns did not believe that the foraminifera actually precipitate manganese, copper, and nickel, 

although they deposit iron oxide as a cementing 

agent, but they did "feel that the large number of 

these animals ... on the nodules from the coppernickel rich zones of the northeastern equatorial 

Pacific, are somehow linked to the unique chemical 

composition of nodules from this area" (Margolis 

and Burns, 1976, p. 259), perhaps as a part of the 

high biologic productivity of the area. They asked, 

however, why, if high productivity of the surface

49
layers of the ocean is the critical factor in tracemetal concentration in the manganese nodules, are 

nodules from other areas of oceanic upwelling and 

high productivity (the diatom ooze beneath the 

Antarctic convergence at about 55° S., for example), not also so enriched? As a possible reason, 

they suggested dilution by terrigenous sediment in 

those areas. Nodules from high southern latitudes 

differ from those in the equatorial region not only 

in their lower metal content but also in their low 

manganese-iron ratios. Cronan (1977, p. 37) suggested that high detrital sedimentation rates 

"could lead to low Mn/Fe ratios in view of the 

greater amounts of releasable Fe relative to Mn in 

the products of continental weathering," and he 

suggested that higher detrital sedimentation rates 

in the Atlantic compared to the Pacific may explain 

the differences in their manganese-iron ratios.

However, many of the stations outside the 

Clarion-Clipperton zone in the Pacific, where 

nodules are high in combined nickel and copper 

(figure 14), as well as many stations where the 

nodules contain 35 percent manganese or more 

(figure 18) do, in fact, lie seaward of areas of 

coastal upwelling along the eastern side of the 

Pacific basin, close enough, perhaps, to receive 

some of the organic debris generated by coastal 

upwelling. But such a relationship is not evident in 

the central South Pacific, where the nodules are 

also high in combined nickel and copper (figs. 14 

and 15).

Many of the regional variations in nodule metal 

content relate to the physiography of the ocean 

basins as it controls depth, organic productivity, 

and sediment type. Cronan's (1977) analysis of 

variations in nodule metal contents from different 

environments brings out, for example, the high 

cobalt content of nodules from seamounts and 

other submarine elevations, the high manganese 

content of nodules from continental borderlines, 

and the high combined nickel and copper contents 

of abyssal nodules.

In summary, many factors may play a part in the 

origin of subsea manganese nodules and the variations in their compositions: (1) the rate of deposition of sediment and its content of terrigenous and 

biogenous matter, (2) the redox potential of the environment and the extent to which diagenetic processes are locally operative, (3) the local availability 

of various metals, (4) the local availability of 

nucleating materials, (5) the bottom topography 

and water depth and the bottom-current activity

and character, and (6) the biologic productivity of 

surface waters, which is, in turn, related to oceanic 

circulation and its effects in locally bringing 

nutrient-rich waters into the photic zone.

Combinations of these factors seem to explain, at 

least partly, some of the features of nodule 

distribution and composition. For example, the 

high concentrations of cobalt in western Pacific 

nodules relate to the highly oxidizing, essentially 

nondepositional environment prevailing on the extensive seamounts and plateaus in that area. The 

asymmetrical concentrations of the principal 

metals in nodules on the eastern sides of the oceans 

versus those on the western sides and their 

latitudinal variations may be a function of slow 

sedimentation at abyssal depths and oceanic circulation. The main elements of oceanic circulation 

are (1) two large circulating gyrals, one in the northern hemisphere moving clockwise and one in the 

southern hemisphere moving counterclockwise, (2) 

an eastward-flowing equatorial countercurrent between them, and (3) areas of high organic productivity where cold, nutrient-rich waters upwell in 

coastal areas along the eastern sides of the basins 

in each hemisphere and along the equatorial 

countercurrent. These elements combine to create 

a widespread blanket of sediments on the abyssal 

floor; this blanket varies regionally in character, 

depending on whether biogenous, pelagic, or terrigenous sediments are dominant, and is generally 

below the lysocline where metals are liberated 

from organic matter and where diagenic processes 

are active in mobilizing and partitioning metals.

The differences in the average compositions of 

nodules from ocean to ocean may reflect the major 

differences in their geology and morphology. The 

Atlantic Ocean, for example, receives much more 

terrigenous matter per unit of area than the 

Pacific, its abyssal plains and areas covered by 

noncalcareous pelagic sediments are proportionally much smaller, and its mean depth is nearly 10 

percent less-all factors that would help to account 

for the lower average contents of manganese, 

nickel, and copper in Atlantic nodules.

But such broad controls are not much help in explaining many aspects of the regional trends-for 

example, the continuation of the poleward decrease in manganese, nickel, and copper contents 

of nodules to high latitudes, even in areas of high 

organic productivity; the area of the central South 

Pacific in which the content of these metals is high; 

the apparent localization of the manganese-rich (35

50
percent or more) nodules on the eastern side of the 

Pacific basin and the northeastern equatorial 

region east of the Clarion-Clipperton zone and 

their lower nickel and copper contents; the higher 

iron content of nodules on the western side of the 

Pacific; and the anomalously high local content of 

some normally minor metals such as tellurium, 

lead, and zinc. Given the large number of factors 

that may affect the composition of the nodules, it is 

not surprising that it is difficult to determine their 

interplay in accounting for specific variations. But, 

plainly, a greater understanding of ocean processes and regional oceanography is needed to explain all the variations observed in the compositions of subsea manganese nodules. If the reasons 

for these variations do come to be understood, they 

may facilitate, on one hand, prospecting for 

economically valuable deposits; on the other hand, 

the local composition of nodules may serve as an indicator of locally prevailing environmental conditions.

SUMMARY

Analysis of the publicly available data in the 

Scripps Sediment Data Bank supports and extends 

previous observations concerning the composition 

of subsea manganese nodules. Although all nodules 

contain amorphous iron oxide, one or more manganese minerals, and phillipsite-all of which form by 

accretion around a nucleus-and some admixed 

silicate grains from extraneous sources, regional 

variations in composition are pronounced. Nodules 

from the Pacific average 1.42 times as much manganese and 2.36 times as much combined nickel 

and copper as those from the Atlantic and 1.2 

times as much manganese and 1.5 times as much 

combined nickel and copper as those from the Indian Ocean. The mean iron content of Atlantic 

nodules is about 1.2 times that of Indian nodules 

and nearly 1.5 times that of Pacific nodules. Within 

each of the oceans, the composition shows both a 

circumferential and a latitudinal variation. 

Nodules richest in manganese, nickel, and copper 

are found mainly in the eastern parts, and those 

richest in iron and cobalt are found in the western 

parts. The average manganese, nickel, and copper 

contents of nodules within the 20° latitudinal zones 

generally increase toward the equator in both 

hemispheres, and iron generally decreases, 

although its high is in the 20° to 40° S. zone. 

Cobalt decreases slightly toward the equatorial

region in the northern hemisphere but shows the 

opposite relation in the southern hemisphere.

Nodule composition is also related to water 

depth. The relation is not linear but is more in the 

nature of a threshold depth of about 2,900 to 3,000 

m, above which combined nickel and copper contents greater than 1 percent are rare and below 

which nodules containing cobalt in amounts 

greater than about 0.6 percent are rare. Below the 

threshold depth for combined nickel and copper 

and above that for cobalt, the maximum metal contents increase to an optimum depth (in the Pacific, 

about 4,800 to 5,200 m for combined nickel and 

copper and 800 to 1,850 m for cobalt) and then 

decline. The manganese content shows little correlation with depth, although there does appear to 

be a decrease in the maximum and perhaps an increase in the minimum with increasing depth. 

Publicly available data on concentration are too 

sparse to support generalizations about its variations, but nearly all measurements showing 

nodules in concentrations of more than about 13 

kg/m2 are from depths of greater than about 3,700 

m. The greatest concentrations of metalliferous 

oxides, however, appear to be not in the nodules 

but in the widespread encrustations on the midPacific seamounts at depths of 1,200 to 2,500 m.

Although the composition of the nodules varies 

widely, three rarely overlapping, distinct compositional types that are of possible economic interest 

can be recognized. (1) Nodules containing more 

than about 1.0 percent combined nickel and copper 

only expectionally contain more than 0.5 percent 

cobalt and 35 percent manganese. (2) Nodules containing more than 0.5 percent cobalt rarely contain 

more than 1.0 percent combined nickel and copper. 

(3) Nodules containing more than 35 percent manganese only exceptionally contain more than 0.5 

percent cobalt, although they average nearly 1.1 

percent combined nickel and copper. Geographically, nodules in these compositional groups occur 

in the regions where they might be expected on the 

basis of the relationships previously mentioned. 

For example, areas in which nodules have high 

cobalt contents are found mainly at relatively 

shallow depths in the central Pacific. Nodules having high nickel and copper contents occur mainly 

at abyssal depths at low latitudes. The ClarionClipperton zone in the northeastern equatorial 

Pacific represents the largest accumulation yet 

known of nodules averaging 1.8 percent combined 

nickel and copper or more. Similar types also are

51
present in the southeastern equatorial Pacific and 

the equatorial part of the Indian Ocean, but 

nodules having high combined nickel and copper 

contents also occur at higher latitudes. Nearly all 

of the stations at which high manganese contents 

have been found are in the eastern and northern 

equatorial Pacific.

The data on high cobalt and high manganese 

types are not sufficient to justify an attempt to 

delineate the areas in which they are found as 

targets for exploration, although the data available 

would help in selecting regions where deposits of 

those types might be sought. Rough exploration 

targets for nodules having high combined nickel 

and copper contents have been delineated, however, and indicate several large areas where exploration might be justified later on.

Nearly 60 chemical elements have been found in 

subsea manganese nodules, many in concentrations far exceeding their average abundances in 

the Earth's crust. Variations in the concentrations 

of many of these elements with latitude, depth, and 

metal type follow the principal metals. For example, the highest means for magnesium, scandium, 

chromium, and zinc are found in nodules containing more than 1.8 percent combined nickel and 

copper; the highest means for phosphorus, 

titanium, vanadium, calcium, strontium, yttrium, 

zirconium, lanthanum, cerium, and lead are found 

in nodules containing more than 0.5 percent cobalt; 

the highest means for sodium and lead are found in 

nodules containing more than 35 percent manganese. However, the nodule groups having high 

combined nickel and copper, cobalt, and 

manganese contents do not include the maximum 

values for several other elements, such as titanium 

(8.9 percent), vanadium (0.5), zinc (9.0), and lead 

(0.75). Many of these maximums are higher than 

the means by an order of magnitude or more and 

may represent analytical errors. That this explanation may not hold, however, is suggested by the 

fact that the maximum for each ocean is also much 

higher than the world mean. The world maximum 

for zinc, for example, is from the Indian Ocean, but 

the high values in the Atlantic and Pacific Oceans 

are 8.0 and 7.0 percent, respectively. It seems 

possible, therefore, that types of metal-rich 

nodules other than those discussed here may exist 

and that some of them may be of potential 

economic value. Some minor metals in nodules rich 

in combined nickel and copper and in cobalt may 

also prove to be recoverable as coproducts.

Molybdenum and vanadium, for example, would 

seem to be candidates for recovery from nodules in 

the Clarion-Clipperton zone.

Not many samples have been analyzed for precious metals, but the few analyses available indicate that some are present in amounts much 

higher than their average abundances in the 

Earth's crust, although they are still too low to be 

of primary economic value. Platinum, for example, 

has been found in a sample from the ClarionClipperton zone and in one from the Blake Plateau 

in amounts of 123 and 453 ppb, respectively.

Many of the variations in the composition of 

manganese nodules are reflected in their mineralogy. It is now well established that the nodules 

are mixtures of three manganese mineral phases 

(vernadite, todorokite, and birnessite), an amorphous iron oxide phase, phillipsite, and admixed 

clay and other silicate minerals from extraneous 

sources. Fine-grained manganese and iron oxides 

have the capacity to attract and hold by physical 

adsorption a wide variety of metals; in addition, 

the crystal structures of todorokite and birnessite 

have sites in which small divalent cations such as 

nickel and copper can replace Mn+2 and other sites 

that will accommodate large cations such as 

potassium. It has also been established that 

todorokite forms on the parts of nodules that are 

buried in the uppermost layer of sediments as a 

result of diagenetic processes in which manganese 

(but not iron) is dissolved under the reducing conditions prevailing in the sediments (perhaps created 

by decaying organic matter), carried upward, and 

precipitated under the oxidizing conditions prevailing on the sea bottom. The amorphous iron-vernadite phases are direct precipitates from 

seawater and form on the tops of nodules exposed 

to seawater or as crusts on bedrock surfaces where 

there are no nucleating grains. Both groups of 

minerals form in the same macroenvironment of 

the deep ocean floor, and the mineral composition 

of a nodule thus depends on its exposure to 

seawater, as opposed to sediment in which 

diagenetic processes are operating. That fact alone 

does not explain the regional variations in nodule 

composition, however, for the nickel and copper 

contents of todorokite vary considerably.

Many factors may play a part in the origin and 

composition of the nodules, and combinations of 

these factors seem to explain at least partly some 

of their variations. For example, the high cobalt 

content of western Pacific nodules may be related

52
to the highly oxidizing, essentially nondepositional 

environment prevailing on the extensive seamounts and plateaus in that area. The circumferential and latitudinal variations may be related to 

oceanic circulation, which creates areas of high 

organic productivity along the eastern sides of the 

basins in each hemisphere and along the equatorial 

countercurrent and results in a slowly accumulating, widespread blanket of sediments on 

the abyssal floor. The regional variation in the 

character of this blanket depends on the 

dominance of biogenous, pelagic, or terrigenous 

sediments in which diagenetic processes are active 

in mobilizing and partitioning metals. The differences in the average compositions of the 

nodules from ocean to ocean may relate to major 

differences in their geology and morphology. The 

Atlantic, for example, receives much more terrigenous matter per unit of area than the Pacific, 

its abyssal plains are proportionately less extensive, and its mean depth is 10 percent less-all factors that would help account for its lower average 

manganese, nickel, and copper contents. But a better understanding of ocean processes and regional 

oceanography and geology is required to explain 

all the variations observed in the composition of 

subsea manganese nodules.

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