Ferromanganese oxide deposits from the Central Pacific Ocean, II. Nodules and associated sediments

Gmchimica 8 -on

c( Cosmochimica Aclo Vol. 49, PP. 43745 Pns Ltd. 1985. FVinted in U.S.A.

I

00167037/85~3.00

+ .I0

Ferromanganese oxide deposits from the Central Pacific Ocean, II. Nodules and associated sediments ANDREW C. APLIN’ and DAVID S. CRONAN AppliedGeochemistry Research Group, Department of Geology, Imperial College, London, SW7 2BP, UK. (Received December 23, 1983; accepted in revised form October 30, 1984) Abstract-Bulk chemical, mineralogical and selective leach analyses have been made on a suite of abyssal ferromanganese nodules and associated sediments from the SW. equatorial Pacific Gcean. Compositional relations between nodules, sediment oxyhydroxides and nearby ferromanganeae encrustations are drawn assuming that the crusts represent purely hydrogenetic ferromanganese material. Crusts, N&-rich nodules and sediment oxyhydroxides are compositionally similar and distinct from diagenetic todorokitebearing nodules. Compared to Fe-Mn crusts, sediment oxyhydroxides are however slightly enriched, relative to Mn and Ni, in Fe, Cu, Zn, Ti and Al, and depleted in Co and Pb, reflecting pmccmea of nonhydrogenous element supply and diagenesis. 6MnQ nodules exhibit compositions intermediate between Fe-Mn crusts and sediment oxyhydroxides and thus are considered to accrete oxides from both the water column and associated sediments. Deep wean vertical element fluxes associated with large organic aggregates, biogenic calcite, silica and soft parts have been calculated for the study area. Fluxes associated with organic aggregates are one to three orders of magnitude greater than those associated with the other phases considered, are in good agreement with element accumulation rates in sediments, and are up to four orders of magnitude greater than element accumulation rates in nodules. Metal release from labile biogenic material in surface sediments can qualitatively explain the differences between the composition of Fe-Mn crusts and sediment oxyhydroxides. Tcdorokite-rich diagenetic nodules are confined to an eastwards widening equatorial wedge. It is proposed that todorokite precipitates directly from interstitial waters. Since the transition metal chemistry of interstitial waters is controlled dominantly by reactions involving the breakdown of organic carbon, the supply and degradation rate of organic material is a critical factor in the formation of diagenetic nodules. The wide ranp of (trace metal/Mn) ratios observed in marine todorokite nflects a balance between the release of trace metals from labile biogenic phases and the reductive nmobilisation of Mn oxide, both of which are related to the breakdown of organic carbon.

INTRODUCTION IT IS GENERALLYconsidered that the composition of marine Fe-Mn nodules reflects the relative importance of two basic modes of accretion: firstly, hydrogenetic accretion directly from the water column results in an intimate, approximately 1:l mixture of aMnO and amorphous Fe oxyhydroxides; secondly, diagenetic accretion, controlled by a variety of oxic and sub-oxic early diagenetic reactions in associated sediments, results in the precipitation of Mn-Cu-Ni-Znrich todorokite (SAAB, 1972; CALVERT and PRICE, 1977; USUI, 1979; HALBACHet al., 198 I). In principle, similar processes can potentially control the composition of micronodules and finegrained oxyhydroxides dii in sediments. However, no clearcut relations have been observed between the compositions of nodules and sediment oxyhydroxides, suggesting a partial decoupling of the sediment-nodule system (CALVERT and PRICE, 1977; MARCHIG and GUNDLACH, 1979; PIPER et al.. 1979; LYLE, 1981). A precise estimate of the influence of diagenesis on the compositions of nodules and sediment oxyhydroxides can only be made if the composition of

’ Presentaddrem Ccntre de Reeherches Petrographiques et Geechimiques, B.P.20, 54501 Vandoeuvre-les-Nancy, France.

the pure hydrogenetic end member is known. For the Central Pacific, this is 8iven by the composition of Fe-Mn encrustations accreting on hard substrates in the Line Islands Archipelago (this paper’s companion). Compositional di!Terences between the crusts, nodules and associated sediment oxyhydroxides must therefore represent non-hydrogenous pmcesses of metal supply, and sediment diagenesis. In the Pacific, nodules with an important diagenetic component occur in regions of relatively high surface water productivity, strongly implying that biogenic material plays an important role in their formation (PRICE and CALVERT,1970, GREENSLATPef al., 1973; PIPER and WILLIAMSON, 1977; EXON, 1983). We have calculated deep ocean fluxes of metals associated with labile biogenic phases, coupling these data with the hydrogenetic crust data to assess the role of biogenic material in those early diagenetic reactions which may atfect nodule and sediment oxyhydroxide chemistry.

MATERIALS AND MEI’HODS Seventy-two surface sediments and 61 nodules were ob tained during CcoplsoPAC cruises in 1980. and from the core collect&s at the University of Hawaii, Scripps Institution of Oceanography and Lament Doherty Geolo8ieal Observatory. Both nodules and sediments to@er examined from 36 sites.

437

were

4 C. Aplin and D. S. C‘ronan

43x

Table 1. Average bulk chanical composition and selected oxide and element ratios of sediment fran the S.W. eo=turial Pacific

:203 Tia 3 Mid co o_l Ni

TdtCk3u

Penrhyn

NEP

mwr

qc

11.5c2.5) 8.4f2.4)

li.Li(l.til 8.9c2.4)

l.O(O.7)

lO.9(1.?) 8.2c2.5)

6.lcr.o) 22.6(5.0)

16.6 7.7

1.4(0.5)

2.OCO.6) 19?(48) 446(115) 338(102)

434(187)

1070(260)

210

70(17)

4&25)

176(56)

4toc50)

0.77(0.13) 0.16(0.44) 0.014(O.Wt)

0.73CO.17) 0.20(0.07) 0.014(0.~3)

3.7 1.2 ---

0.96(0.37! 93f34) 281(139)

Pb In

143(31?

;&$2’3

;-;;&‘;;,

Co/H, 2 3

0:014(0:002)

167177)

-_

34

165

0.46 G.033 0.026

FdCific PfSbgiC Clay (FpC, Bischoff et al. 1979) end Metalliferws sediments from the &~er hain (Heath and Dymond, 1977 1. Gxides in u&&t % bulk sediment, elements in ppII CC&Co3free basis). FiguRZS in parentheses are one standard deviation.

Prior to chemical analysis, sediment samples were examined in smear slides. Bulk chemical analyses of air-dried nodules and sediments were made by atomic absorption spectrophotometry for Mn, Fe, Cu, Ni, Co, Pb. Zn, Ca, Al and Ti (Appendii A, B; Tables 1,4). Accuracies, determined by comparison with international nodule standards, were better than 10% for all ekments except AI (15%), whilst precisions were generally better than 5%. Zn contamination from core barrels was suspected in some samples, and these results were not used. Sediments and selected nodules were leached by mixed hyd~xylamine hyd~hlo~~-~c acid using a slightly modified version of the CHESTER-HUGHES ( 1957) technique. This leach removes Mn oxides and noncrystalline Fe oxides, CaCQ and adsorbed ions, and may partially attack Fe-rich smectite (HEA+FIand DYMOND, 1977).Sampies were shaken with the magent for 5 minutes and left to stand for 20 hours before filtering and analysis of the leachate (Appendix C; Tabks 2, 3). The precision of the analyses was generally better than 10%. As a further check, analyses of selected 1-h residues were made, the sum of residue plus lea&ate being in agreement with the bulk composition, within the limits of precision. Seketed sediments were additionally leached at a ratio of I:5 by weight with a 0.2 M mixture of ammonium oxaiate and oxalic acid, buffered to pH 3 (SCHWERTMANN, 1964). This is considered to remove Mn oxides and amorphous Fe oxides but does not attack crystalline Fe oxides or Fe-rich smectite (LANDA and GAST, 1973: HEATH and DYMOND, 1977). Samples were shaken for 60 seconds and left to stand in the dark for 2 hours. Following filtration, 2 cm3 of 30% hydrogen peroxide were added to the leachate to oxidise the oxalic acid and the solution evaporated to approximately 5 cm’. The solution was made up to 25 cm’ with i M HCI and analysed by AAS (Table 3). Data presented by BREWARD and PEACHEY (I 984) suggests that the presence of oxalate in the solution matrix introduces less than 5% error in the determination of each element at our levels of analyte. Levels of precision were better than 5% for most elements, but only 30% for Zn and 50% for Pb (analyte near detection limit). Nodule mineralogy was determined by X-ray diffraction by subjecting finely ground noduk powders to Feti radiation during I”28 mitt-’ runs between 5 and 90”28. Clay mineral abundances in the less than 2 pm fraction were made f&owing the method of BI~CAYE f 1965). RESULTS Sedimentary environment The study area consists of four deep basins (North-

east Pacific (NEP), Penrhyn, Samoa, Tokelau) sepa-

rated by upstanding tectonic units (Manihiki Plateau, Line, Tuamotu, Tokelau, Society and Cook Islands Archipelagos, Fig. I). Most of the basinal areas are below the CCD (4900 m. BERGER et al., 1976). Biogenic silica occurs equatorwards of 10°S, but sediments rarely comprise more than 20% biogenic silica. The abundance of volcanic gIass in the sediments generaily increases westwards and is an important sediment builder in local&d areas (Fig. 2). Since most volcanic rocks in the area are Ti-rich (JACKSON et al., 1976; NATLAND, 19801, the abundances of Ti and volcanic glass in sediment are closely related. Fe-rich smectite is the most abundant clay mineral in the region, accounting for 50-10090 of the t2 pm sediment fraction (APLIN, 1983). In the marine environment, authigenic smectite is considered to form either through the low temperature alteration of basalt or through reactions between Fe oxyhydroxides and biogenic opal (see CC&E and SHAW, 1983,for a review). in the S.W. Pacific, smectite appears to form via both processes (APLIN. 1983). Sedimentary Geochemistry

Results of chemical analyses of bulk sediments and selective leach data are given in Tables l-3 and Appendices B and C. Sediments are enriched in Mn, Fe and trace metals compared to average Pacific pelagic clay, but are strongly Mn-Fe oxide depleted compared to Bauer Basin sediments which are con-

.2MKLn

15 l.lO(O.35) 0.6&O.%) o.owo.CC5> O.o2wJ.co?f 0.016(0.oOe) 0.019(0.005) 0.013(0.003)0.011(0.003) 0.006f0.001)O.Co3(O.M)08) O.~(O.O~~)

C.%(o,43) O.YJ(O.26)

0.34tO.281 0.34(0.20)

t.tefo.Yt)

1.15(0*3>

0.02l(O.m5) 0.011(0.001) O.~(O.~~

0.24(0.16)

0.009(0.056) 0.026(0.008) O.a%~O.Olf)

-0.03,

-0.03

439

Pacific Fe-Mn oxide deposits. II Table

3.

ksults

Of selective leaches

<-w->

<-%->

th ksloniun

1-2B Kl-4T Kl-4B Kl-51 Kl-56 Kl-68 cl-15 KK72-32 z:p

o~te-al~lic 0 63 il

ml-32 P-3 x leached (nan) 8.d.

Fe

Al

'II

CU

Pb

NiCa

0.58 0.66 0.61 1.23 1.50 0.54

acld leach 1.23 0 @J 1.45 0:5a 1.42 0.60 1.29 0.93 1.13 0.62 0.92 0.84 1.44 0.68 1.24 0.41 2.33 1.39 0.87 0.39

:*:i 0:22 0.15 0.14 0.10 0.10 0.06 0.17

136 68 127 63 119 68 134 65 90 @a 138 % 1% 226 32u 374 445 135 5ca 58

fx 1:52

1.09 1.54

0.37 0.55

L;; 0~10

142 234

9;

22 5

11 "

Zn

0

39

:‘I

; 10

37

41

5

i

‘59 199 60 280 154 107 301 Ml

1;;

! iii

0 02 5 284 10 57

q

iEn.1 mxyl.mim ahadhydrmblorideac+tic a2 15 a acid 2 leach m Tdzuaed.15 4 2 4 Haan x 1emhed 21 2 ti ,h,,,sed.~: 6 3 3

40 16 52 12

50 18 74 17

71 15 74 18

67 22 66 22

50 13 40 14

the HSFs generally ,exhibit higher Al/Mn, Al/Fe, Cu/ Mn and ZnfMn ratios, lower Co/Mn and Pb/Mn ratios and similar Mn/Fe and Ni/Mn ratios (Fig. 8). Important regional variations are observed in the composition of the HSF. Tokelau Basin sediments exhibit lower (Mn/Fe)H and higher (Al/M& and (Al/Fe)H ratios than either the Line Island crusts or the Penrhyn sediments (Fig. 4). Fen is unrelated to Mnn in the Tokelau sediments (TM,+ = 0.04) but shows a stronger correlation in the Penrhyn sediments (rMn_rc= 0.48). Since strong correlations would result from a model of sediment formation in which a constant supply of Ll-type authigenic oxides is superimposed upon a variable supply of detrital minerals, the weak covariance between Mn and Fe suggests that Mn:Fe fractionation has occurred within the sediment HSF, especially in Tokelau sediment. In

sidered to contain an important hydrothermal MnFe component derived from the East Pacific Rise (HEATH and DYMOND, 1977). The sediments plot close to basaltic material on BOSTROM’S(1973) Fe/ Ti versus Al/Al+Fe+Mn diagram (Fig. 3). We interpret these results as indicating that there is no discemable input of hydrothermally derived metals to the study area, but that the sediments contain a relatively important authigenic oxide component resulting from extremely low rates of sedimentation of detrital material (KRISHNASWAMI, 1976). Oxyhydroxides are most enriched in Penrhyn Basin and NEP Basin sediments where the occurrence of high abundances of phosphatic fish debris (S-89 of sediment) suggests particularly low sedimentation rates (BISCHOFFet al., 1979). Although a variable proportion of each sediment is leachable by hydroxylamine hydrochloride-acetic acid (leachable fraction of each element is denoted by subscript H, e.g. Mnn). the data indicate that most Mn, Co, Ni and Pb is contained within the hydroxylamine soluble fraction (HSF), that most Fe. Al and Ti is non-leachable and that approximately half the Cu and Zn is leachable. Calculation of element ratios shows that compared to the Line Island crusts-which are considered to represent oxides accumulating directly from the water columnTable

4.

Average canpasitlon and of Line Islands

N.E. Ihciflc Basin N. Rnrhyn Basin s. hnrhyn Basin ltkelau zzz kTr N.E. Pacific2

Pb and ZJI in ;rnta rata

frao fhan

23.0 21.0 17.4 18.4 17.5 17.3 24.6 16.8 23.5 19.5

ppm, other

clasby et al. Piper et al.

Nodule geochemistry

The average composition of bMnO&h nodules and todorokite-rich nodules (defined here as those

of nodules according to cIwst.¶ fran below 2km.

Fe

&I

addition, the strong covariance seen between Fen and sediment, but which is absent in Penrhyn sediment, strongly suggests that Al closely follows Fe during Mn:Fe fractionation processes (Fig. 5). The ammonium oxalate-oxalic acid (AOOA) leach removes an Fe-Al-Ti-Mn rich crypto-crystalhne phase additional to oxides leached by hydroxylamine hydrochloride-acetic acid (Table 3). The relative pro portion of each element varies but is typically Fe:Al: Ti:Mn = 1:1:0.5:0.3. HEATH and DYMOND (1977) found that hydroxylamine attacked Fe-rich smectite from Bauer Basin sediments, but that AOOA left the smectite intact. Since AOOA leached more Fe than hydroxylamine from the S.W. Pacific sediments, we conclude that an insignificant proportion of the Fe in the hydroxylamine soluble fraction is derived from smectite. A notable feature of the oxalate data is that oxalate-leachable Ti is strongly correlated with bulk sediment Ti, and thus with the abundance of volcanic glass in the sediment (Fig. 6). For this reason, we tentatively conclude that the Fe-rich oxalate-soluble, hydroxylamine-insoluble phase is a low temperature weathering product of volcanic glass. Al,, in Tokelau

10.4 10.3 14.0 15.2 17.6 19.6 8.1 17.3 6.9 17.6

elexnts (1981)

(1979)

location

and mineralogy,

Ca

Al

Ti

CU

Ni

Co

F'b

7n

M/Fe

1.7 1.7 1.8 1.8 1.9 -

2.7 3.2 2.7 2.4 2.2 -

0.47 0.77 1.02 1.27 1.53 -

0.25 0.21 0.36 0.32 0.36 0.23 0.16 0.32 0.x) 0.47

1080 1010

2.2 2.0

i% 950 -

E 620 -

1.: l:o 0.9

213 1121 2.8 0.49 1.56 1.20

0.90 0.80 0.46 0.48 0.33 0.23 1.08 0.34 0.94 0.36

460 460

1:9 1.6 2.6

0.69 0.69 0.26 0.37 0.23 0.17 1.14 0.22 0.76 0.17

8$

3.0

1010

I

in w&@t

%.

& 420 950

570

-

4 C Apiin and D. S. Cronan ----

NORTW-MST

17S”W

165”

170”

160”

1JS’

1SO’

145”

20’S 14O’W

FIG. 1. Map of study area, showing basin divisions and sample locations. Key: A = nodule and sediment, imperial College analysis; l = nodule, 1.C. analysis: * = sediment, K. anatysis; X = nodule,

Scripps Data Bank.

showing 9.8/1.4

A peak ratios greater than two) are

shown in Table 4. The average composition of nodules from specific basins reflects the relative importance of each mineral type and thus the influence of sedimentary d&genesis in the area. PRICE and CALVERT (1970) showed that the Mn/Fe ratio of nodules [(Mn/Fe),] is a useful index of diagenetic intluence. The distribution of (Mn/FeX, in the S.W. Pacific shows an equatorial wedge of high values (greater than 3) extending to 3% at 175”W and to 12’S at 145’W, expanding parallel to the productivity isolines in the region (KOBLENTZ-MISHKEefal., 1970) (Fig. 7). Todorokite bearing nodules are similarly confined to the equatorial wedge, although 6MnOz nodules are also common within it. To the south, 6Mn02 is the sole Mn oxide mineral and nodules exhibit compositions generally similar to the Line Islands crusts (APLINand CRONAN, 19851, though depleted in Mn and Co (Table 4). Inter-element relations for 6MnQ and todorokite nod&s are in agreement with previous findings (e.g. CALVERT and PRICE, 1977; HALBACH and OZKARA,

2od 176”W

166

156

146

I

FIG. 2. Map showing distribution of volcanic glass in surface sediment.

1979). Element associations in GMnOz nodules are generally similar to those observed in the Line Islands crusts (APLIN and CRONAN, 198% but with a few exceptions. First, Ti is associated with Fe in the nodules but shows no reiationship to either Mn or Fe in the crusts. Second, Zn is associated with Mn in the crusts but not in the nodules. Third, Cu is associated (weakly) with Mn in the nodules but not in the crusts in which it is associated more closely with Fe. These observations suggest that direct accretion of oxides from the water column is an oversimplistic mechanism for the formation of SMnO?rich nodules. CRUST-%&NODULE

RELATIONS

Although no clear pattern is observed for individual HSF-nodule pairs, general trends emerge if mean

FIG. 3. Fe/Ti ver.suFAI/(AI+Fe+Mn) (after BOSTROM, 1973)showing ~rn~tion~ r&&ens of sediment from the Penrhyn Basin (P) and the Tok&u Basin (T) to tcrriganous matter (TM), basaltic dab& (BM) and mctalliferoussediment from the East Pacific Rise (EPR).

Pacific Fe-Mn oxide

_-_ 17FW

160

165

$70

441

deposits. II

185

140-w

145

160

FIG. 4. Areal distribution of the Mn/Fe ratio in the hydroxylamine hydrochloride-acetic acid soluble fraction of S.W. equatorial Pacific surface sediment.

compositions are considered (Fig. 8). Broadly, our results concur with previous findings in that the crusts, HSF, and 8Mn02 nodules are compositionally similar but are distinct from diagenetic todorokitebearing nodules (CALVERT et al., 1978; PIPER et al., 1979; LYLE, 1981). It is particularly striking that the composition of HSFs of sediments associated with diagenetic nodules show little evidence themselves of significant diagenesis, suggesting that in the S.W. Pacific the supply of the metabolites which drive early diagenetic reactions is only sufficient to remobilise a small fraction of the metals supplied to the sediment-water interface (MARCHIG and GUNDLACH, 1982).

the general compositional similarity of HSFs and dMnOz nodules there are nevertheless differences which must reflect the related processes of element supply and diagenesis. We consider that CO best represents the input of hydrogenous oxides to the sediments, since it is removed from seawater pr~ominan~y by Mn oxides and is poorly diagenetWithin

crusts,

l.o-

ically mobile (KNAUER et al., 1982; APLIN and CRONAN, 1985; B~NATTIet al., 1971). By regarding Co as the hydrogenous oxide reference element we can identify those elements supplied predominantly in association with hydrogenous oxides and those which are also supplied in association with other phases. This analysis suggests the following results: Firstly, a non-hy~o~ supply of Mn is implied by (Co/M& ratios much lower than those in crusts. Since remobilisation from the suboxic zone is not an important source of Mn to oxic surface sediments (BENDER. 1971), and since remobilisation from organic-rich surface microlayers wouid decrease (Co/ Mn)H ratios, an addition of Co-poor Mn is the only way to explain our observations. Potential supptiers of Co-poor Mn are CaC03 and organic matter, which MARTIN

and KNAUER

1983) have identified

‘*O % Al

AI

1

.

lb)

(3

0.6.

(1982,

vertical carriers of Mn through the water column (see next section for further discussion). Secondly, lower (~/Mn~ ratios than observed in crusts likely result from the same process as described as important

l

/

l

I = 0.83

b/’

0.

.

0.6.

l

l

.

0.4.

.

.

.

,*-

l

'.p"=

Q1

r = 0.20

. 0.4,

l

.**

T-

.

0.2.

0

l

. .

96Fe 0.6

1.2

.. l

l

l

02

.

* .*

.

l

l

.

.

1.6

0’

If

,___:j. 0

. Fe

%

0.6

1.2

1.6

FIG. 5. Plot of Al versus Fe in the hydroxylamine hydrochloride-acetic acid soluble fraction of (a) Penrhyn Basin sediment and (b) Tokelau Basin sediment.

A. C. Apltn and D. S. Cronan

442

I-m

0.26

Tbx

0.20

.

. l

0.15

0.10

~

I

o.osJ

0.3

l

.

. .

l

. l

I

0.5

O.?

I

96%

1.1

0.9

FIG. 6. Plot of ammonium oxalate-oxalic acid leachable versus total sediment Ti(Ti,).

Ti(Ti,,)

for Co. Although the phases which remove Pb from the oceans are not precisely known, the extremely high crust/seawater partition coefficient for Pb (APLIN and CRONAN, 1985) suggests that scavenging by PeMn oxides is probably an important removal path of Pb in the ocean. Thirdly, a haimyrolytic supply of Fe, AI and Ti occurs in those sediments, mainly within the Tokelau Basin, rich in volcanic glass. This is supported by a) Tokelau (Mn/Fe)n ratios which are lower than those in crusts, b) the strong positive covariance between Fe,, and Al” in Tokelau sediment, c) particularly high (AWe), and ~Al/Mn~ ratios in Tokeiau sediment, and d) the results of the AOOA leach which indicate the occurrence of an easily leachable Fe-AlTi rich phase resulting from the low temperature alteration of volcanic glass. However, a non-hatmy-

2w6 176%

165

FIG. 7.

166

rolytic source of Al is also Implied by the occurrence of high (Al/Fe)u and (Al/Mn)~ ratios in volcanic glass deficient Penrhyn and NEP Basin sediment (Table 2). This supports the body of recent evidence supporting an active role for Al during early diagenesis and particularly MACKIN and ALLER’S(1984) observation that Al is strongly scavenged by Fe oxide in surface sediment. Fourthfy, the enrichment of Cu and Zn relative to Mn in the sediment HSF is indicative of non-hydrogenous supply. although specific enrichment processes are difficult to identify. Possibilities (which are not mutually independent) include a supply of organically associated Cu and Zn (BRULAND, 1980; KLINKHAMMERef al., 1982) a re-~uilibmtion of oxides to higher concentrations of Cu and Zn in pore waters according to the laws of surface chemistry (BALISTRIERI and MURRAY, 1983) and the formation of diagenetic Cu-Zn-rich micronodules (MARCHIG and GUNDLACH, 1979). Of these, we are least inclined to the third h~thesis, since in contrast to the sediment HSFs micronodules are typicatly enriched in Ni as well as Cu and Zn. Rather, the Ni data support the m-equilibration model, since pore water Ni in oxic sediments is little enriched over seawater, in contrast to Cu which is often highly enriched (KLINKHAMMER et al., 1982; SAWLAN and MURRAY, 1983). Mn/Fe, Cu/Mn and CofMn ratios in 6Mn02 nodules are intermediate between those of crusts and sediment HSFs, suggesting that the nodules represent a mixture of both sediment-derived and water-column derived oxides. This is further supported by the positive covariance between the Mn/Fe ratios in sediment HSFs and of directly associated &MnOr nodules (Fig. 9). Early diagenetic reactions therefore play a role in determining the composition of 8MnOz nodules, which cannot therefore be considered as purely hydrogenous deposits.

156

Area) distribution of Mn/Fe ratios for ferromanganese nodules.

443

PacificFe-Mn oxide deposits, II

0.002 I

0. C

”

D

C

T

I..

0.007

0.01 c H0 T

0.03

I

:I

o

iI

1

I”

1..

c

Ii

0

I..

I

o,oo

3

1

7

pb

F.

0.008.

I**sI’

0.004

I

0 :I

D-

I

c

CHOT

T

I D

I

..

L!! F.

0.04.

H

CHDT

0.08’

1

C

0.03

C”DT

1” I

0.04.

T

..

0.12.

0.04

D

0.00 1

I

“‘“I si

H

H

D

T

Co

F.

0.045

..

0.02

0.005i

C

I H

-* I

.. ’ D

7

FIG. 8. Means and standarddeviations of element ratios in the Line Islands crusts (C), the sediment acid-reducible fractions (H), dMnOl nodules (D) and todorokite nodules (T). A single asterisk indicates that the samples are derived from populations with a mean different to that of the cysts at the 95% confidence interval. Two asterisks mark the 99% confidence interval. ELEMENT FLUXES TO THE SEDIMENT-WATER INTERFACE

S.W. Pacific nodules with a diagenetic component are confined to an equatorial zone of non-calcareous sediments, a distribution consistent with that of similar

. . : . . lr/.

1.5

l

1.0

‘@

“t

tMn/Fd~ 0

I

0

I

0.S

1

I

1.0

I

I

nodules in other regions of the Pacific (Fig. 7, PIPER and WILLIAMSON,1977). Hypotheses erected to explain this distribution invariably invoke the influence of biogenic material, either supplying elements to the sediment-nodule system or driving diagenetic reactions (ARRHENIUS,1963; PRICE and CALVERT,1970; GREENSLATE et al., 1973; LYLE et al.. 1977). Here we attempt to assess the influence of four biogenic phases-siliceous and calcareous hard parts, organic soft parts and huge organically formed aggregateson processes of element supply and diagenesis by combining vertical mass tlux and compositional data to calculate element fluxes to the sediment-water interface. Vertical mass fluxes

l.s

FIG. 9. plot of Mn/Fe ratios in aMnO, nodules [(Mn/ Fe)J versus Mn/Fe ratios of hydroxyiamine hydrochlorideacetic acid soluble fractions of associated sediments [(Mn/ Fe)ti].

Although no direct flux determinations have been made in the S.W. Pacific, reasonable approximations can be achieved by extrapolating the data of HONJO et al. (1982a) for the North Central Pacific gyre and

444

,q i. Aplrn and Table 5. Fluxes of biogenic elements sediment water interface.

Crganicc Mininum t?aximlml

+gcm-2y-' opal Calcite 20 200

200 1000

tc thr~

Pggregates 300 1200

of COBLER and DYMOND (1980) for the equatorial East Pacific. HONJO et al.% ( 1982a) data for calcite, opal and organic C were used to give minimum subequatorial fluxes (Table 5). Maximum equatorial fluxes of each component were calculated in the following way: Organic C-from the surface water primary productivity data of KOBLENTZ-MISHKE et al. (1970) assuming that a constant proportion of productivity reaches the deep ocean (HONJO, 1978, 1980; COBLER and DYMOND. 1980: WAKEHAM ef al., 1980). CaCO,--sediment trap data indicate that the vertical flux of CaCOj is related to primary productivity and that in a given ocean regime the ratio of the net primary carbon fixation to the vertical flux of CaC03 is rather constant (DEUSER er al.. 198 1; HONJO, 1982). We can therefore write: equatorial CaCOl flux = sub-equatorial X

CaCOj flux

equatorial primary productivity sub-equatorial primary productivity

(CaCO 3 flux/Cfix.ed) equatorial ’ (CaCO 3 dChed) sub-equatorial where the last term corrects for the higher Caco 3 ,&&,, ratios observed in equatorial compared to sub-equatorial waters. The data required to solve the equation are taken from HONJO ef al. (1982a), KOBLENTZ-MISHKEL’Ial. ( 1970) DEUSERd al. ( 198 I) and COBLERand DYMOND ( 1980). Opal-we assume that the ratio of the vertical fluxes of calcite to opal equals three (COBLER and DYMOND, 1980).

Table

6. Metal contents of biogenic (calculated from Table 5)

phases

and

fluxes

I>. S. Cronan Aggregates-the vertical mass flux is known to be dominated by rare, rapidly-settling large particles. the majority of which are organically formed aggregates comprising a wide spectrum of biogenic and lithogenic particles (MCCAVE, 1975: HONJO. 1982: HONJO e[ al.. 1982a.b). To calculate the mass flux associated with aggregates. we calculated the total mass flux by assuming that the flux of biogenic matter (CaCO, + opal + organic C) comprises 90% of the total flux (HONJO el al.. 1982a; COBLERand DYMOND 1980). and then assumed that 75% of the total mass flux is associated with large (> 125 pm) aggregates (McCAV~, 1975). Metal contents c!f biogenic phases The metal contents of biogenic hard and soft parts are taken from MARTIN and KNAUER (1973), SCLATER ef al. ( 1976), LANDING and BRULAND (1980) and BOYLE (1981) (Table 6). We have used the Ni content of whole phytoplankton to estimate the Ni/ Si02 ratio, which may therefore be regarded as a maximum value. The chemical composition of aggregates is unknown and will be areally variable. We have used SPENCER et d’s (1978) analysis of a ‘green’ faecal pellet collected at 5367 m in the Sargasso Sea as our estimate, based on the assumption that both pellets and aggregates form by processes which are both essentially indiscriminate with respect to the particle types they remove from the water column. E(emenf fluxes Element fluxes and accumulation rates in S.W. Pacific sediment and nodules are given in Tables 68 (KRISHNASWAMI, 1976; LYLE, 1982). We recognise the limitations of the flux data but are given confidence in its use by the close similarity between the flux of aggregate-associated metals and the metal accumulation rates in sediments (Fig. 10). Cu is supplied in excess of its accumulation rate by a factor

to the sediment-hater

Metal

t+l Fe $5 2 Pb Al Ti

4x10_6 -6 8X10_,

0.8xlO_4

-6

,.',;;",-6 5,.::;;-5 2.2~14~ 4x10 ---& 6x10 ---& --___--

_-6.4~10;; 1x10

10-5-4

4.5x10-5 1*gx1o-6 t1.6~10_~ <2X1O_4 1.6x10_, 1.1x10 ' -----

bta sources :1. E!0y1e (1981) 2. Satin and Knauer (1973) 3. Martin and Knauer (1973) Landing and Bruland (1980)

2100 21600 50 20 20 15

0.6 0.1

0.53

0.03 0.9

0.15 0.: 0.3 ___30.1___

0.6 --

34 --20800 ,300

--__-

4. spencer et a1 5. &later et al 6. Fcwler (1977)

_--___

0.02

fluxes

(1978) (1976)

&m-2ky-1)

0.2 50

‘0.3

4:

6:;:

2 3 ---1

0.3 0:: a.065

21 <0.20 19

190 6 280 5

1

62::

___ ___ 0.3 13 ,g --_ 2

interface

20

---

---

---

390

2g5g

2%

'8';

790 24 1150 19

0.3 190 2503

40

9 0 0

'WO&

7. Data not available --8. ASSUDGS that the composition of faecal pellets and aggregates are identical.

7801 1100 10 40 0 0

445

Pacific Fe-Mn oxide deposits, II

AC->Fbx

/

FLU >A-

1/1-1-1 lcu

Ni .

co

11 1

10000

100 10 1000 ‘AGGREGATES’ FLUX (I&!cnr2 ky -‘)

FIG. 10.Comparison of element accumulation rates in SW. equatorial Pacificsediments (KRISHNASWAMI, 1976) with element fluxes associated with aggregates. It is assumed that aggregatesaccount for 75% of the

total vertical mass flux. of seven, in general agreement with pore water studies suggesting that 90% of the Cu supplied to sediments is recycled into the water column (KLINKHAMMER et al., 1982). Aggregate-associated metal fluxes are between one and three orders of magnitude greater than fluxes associated with calcite, opal or organic C and only aggregates can supply metals at a rate sufficient to account for the metal accumulation rates in sediments. The accumulation rates of metals in nodules are an order of magnitude less than those in sediments, such that the fluxes of calcite-opal-organic C-associated Fe, Cu, Ni, Pb, Zn and Ti are sufficient to account for their accumulation rates in nodules. Assuming that all the Al in the aggregates is contained within alumino-silicate phases, we calculated the composition of the aggregate-associated non-aluminosilicate phases (Table 6). The nature of these phases is unknown, but it is clear that they supply metals to the sediment-water interface in relative abundances significantly different to their abundances in hydrogenous oxides. The quality of

the data do not warrant a more quantitative appraisal of the possible effects of addition of biogenic phases to surface sediment, but a potentially important role is suggested for organic aggregates and, in the case of Al and Ti, for biogenic opal. Diagenetic nodules Calculation of metal fluxes to the sediment-water interface indicates that even in regions of low surface water biological productivity fluxes are sufficient to account for the metal accumulation rates in todorokite-rich diagenetic nodules. The confinement of diagenetic nodules to zones of relatively high biological productivity is not therefore a simple reflection of metal supply, but is related to the degree of metal remobilisation during sedimentary early diagenesis. in oxic sediments such as those studied here, two types of diagenetic reaction may be envisaged as playing a role in the formation of nodules. One releases biologically- and oxide-bound metals during the decomposition of organic material and the dissolution of biogenic hard parts (GREENSLATE et al.,

'lhblc7. Element accwdation rates in central Pacific sdiments and sub-swatorial nodules ELementacc*a_tjon Fec”B”“a,@Ni)

f-t7

790 wlolt sediment' sediment frll&iF &thigenfc 675 Nodule

;Bta fran Cahdatad

50 Krishneswsmi

rate

co

n

5360

25

13

a

430

1125

17

15

7

15

50

2

3

1

3

(1976)

from the equation of

memmtnu/clasqt m

FEE”

qrl Al-oormeted

aeamgatas Lyle

(1982)

‘mculnted

Fe 70

: 0.2 xc0

a ccumlJat.ion

inta mdules ) xcFtx

7:

136m

from Lyle (1982)

OJ

Ni

5020 31cNl 5070 19500

al

rate

n

Fbk

QO 1100

m3~ -

170

I 700

18ooo

400

0

446

i

t Aphn and D. S. Cronan

1973); a second involves the reaction between FeMn oxyhydroxides and biogenic opal to form Fe-rich smectite, fixing Fe and SiOz and releasing Mn and associated trace metals for subsequent incorporation into nodules (HEATH and DYMOND, 1977; LYLE ef al., 1977). The data presented here suggests that reactions involving the degradation of organic material are much more important than either those involving smectite formation or the dissolution of biogenic hard parts. With regard to smectite, if we assume that the hydroxylamine-soluble fraction of the sediments represents those oxides remaining after oxideopal interactions, then the maximum (Mn/Fe), ratio of I .7 in smectite-rich S.W. Pacific sediments indicates that smectite formation cannot sufficiently fractionate Mn from Fe to account for the Mn/Fe ratios in associated nodules. Furthermore, remobihsation of the sediment HSF cannot account for the (trace metal/Mn) ratios in diagenetic nodules. Our preferred model of diagenetic nodule formation involves

the direct

precipitation

of todorokite

from

pore waters. Recent work has shown that near surface pore water transition metal chemistry is closely related to the oxidation of organic carbon (FROELKH et al., 1979: KLINKHAMMER et al.. 1982; SAWLAN and MURRAY, !983). Pore water Ni/Mn and Cu/Mn ratios are highly variable and reflect a balance between the release of trace metals from biogenic phases and the reductive remobilisation of Mn oxide. In highly oxic surface sediments, pore water Cu/Mn and Ni/ Mn ratios are typically greater than unity, indicative of the retention of Mn in the solid phase. In contrast, hemipelagic sediments exhibit Cu/Mn and Ni/Mn ratios as low as 0.003 and 0.01 respectively, lower than those in the Line Islands crusts and indicative of extensive Mn remobilisation (KLJNKHAMMERef al., 1982: SAWLANand MURRAY, 1983). One may therefore envisage an entire spectrum of pore water (trace metal/Mn) ratios which can potentially yield a similar range of diagenetic precipitates. dMnO+ich nodules form where remobihsation is minimal and there is no capability for the formation of a diagenetic precipitate. Since divalent cations are essential to its structure (BURNSand BURNS. 1977), todorokite forms where the pore water concentrations of Cu2+. Ni’+. Zn2’ and Mn2’ reach a certain level in surface sediments. As the balance of diagenesis moves towards Mn remobihsation. Mn2+ replaces Cu”. Ni2+ and Zn’+ in the mineral structure, resulting in the highly Mn enriched. Cu-Ni-Zn poor nodules found in hemipelagic regions. Nodules with a major diagenetic component exhibit high accumulation rates of Cu, Ni, Zn and Mn. high Mn/Fe ratios and rapid growth rates, all of which are consistent with the model presented here (MOORE ef al., 198 1; LYLE. 198 I, 1982; REYSSet al.. 1982). Organic aggregates must play an important role in early diagenesis as they supply the majority of metals and organic carbon to the sediment-water interface. With respect to diagenetic nodule formation, the

supply rate of organic carbon is of major importance since it plays the critical role in metal remobilisation. In contrast, metal release from dissolving biogenic hard parts plays a secondary role in pore water metal chemistry. We may therefore reject hypotheses which relate diagenetic nodule formation to an enhanced metal supply from dissolving skeletal material below the lysocline (PAUTOT and MELGUEN. 1979). Although the model outlined above can explain a large proportion of observations concerning Mn nodules, precipitation from present day pore waters from red clays would nevertheless not yield a typical diagenetic todorokite (KLINKHAMMERet al.. 1982; SAWLANand MURRAY, 1983). Whilst rapid precipitation reactions may mask the true diagenetic mobility of Mn over short distances, the pore water data suggests either that reactions leading to todorokite formation are confined to an organic-rich surface sediment film (SOUTARd al., 1981) or that todorokite formation is episodic. The latter hypothesis is in agreement both with studies showing that the supply and degradation of organic material to sediments is highly variable (DEUSER er al.. 198 I; GARREL~ and PERRY, 1974), and with microscopic studies indicating that diagenetic and hydrogenous precipitates coexist in single nodules (HALBACHand OZKARA, 1979) CONCLUSIONS 1. In the S.W. Pacific, the composition of hydrogenetic Fe-Mn crusts, SMn02 nodules and sediment oxyhydroxides are broadly similar and distinct from todorokite-rich diagenetic nodules. 2. Differences between the composition of sediment oxyhydroxides and Fe-Mn crusts are related to process of non-hydrogenous element supply and diagenesis. The majority of metals are delivered to the sediment-water interface in association with large, organically-formed aggregates; reactions involving the addition of this material to the sediment oxyhydroxides can quantitatively account for sediment oxyhydroxide-crust compositional differences. 3. bMnO+ich nodules exhibit compositions intermediate between Fe-Mn crusts and sediment oxyhydroxides and accrete oxides from both the water column and associated sediments. 4. Todorokite-rich diagenetic nodules are confined to an eastwards-widening equatorial wedge, and todorokite is considered to precipitate directly from pore waters. The critical factor in the formation and chemistry of diagenetic nodules Seems to be the rates of supply and degradation of organic carbon. Temporal variations in surface water biological productivity will therefore affect the composition of abyssal

nodules. Acknowledgemenls-We

thank CCOP/SOPAC, the Scripps Institution of Oceanography and the Lamont-Doherty OK+ logical Observatory for supplying the samples used in this study and CCOP/SOPAC for providing A.C.A. with the

Pacific Fe-Mn oxide deposits, II opportunity to collect some at sea. Financial support was received from the NERC who also provided A.C.A. with a research studentship. Editorial handling: R. G. Bums

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E. R. and GAST R. G. (1979) Evaluation of crystailinity in hydrated ferric oxides. Clays and Clay Minerals

LANDA

21, 121-130.

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LYLE M., DYMONDJ. and HEATH G. R. (1977) Coppernickel-enriched fermmanganese nodules and associated crusts from the Bauer Basin, N.W. Nazca Plate. Earth Planet Sci. Lett. 35, 55-64.

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13.

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ot

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285-303.

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SCHWERTMANN I.J. (1964) Differenzierung der Eisenoxide des Bodens durch photochemische Extraction mit saurer Ammoniumoxalat-Losung. Zeitsch. Pflanzenemahr. Dung Bodenkunde 105, 194-202. SCLATERF. R.. BOYLEE. and EDMONDJ. W. (1976) On the marine geochemistry of nickel. Earth Plane; Sci. Lett. 31, 119-128. SOUTAR A., JOHNSON S., FISCHER K. and DYMOND J. (198 I) Sampling the sediment-water interface-evidence for an organic-rich surface layer. Eos 62, 905. SPENCERD. W., BREWER P. G.. FLEER A., HONJO S., KRISHNASWAMI S. and NOZAKIY. ( 1978) Chemical fluxes from a sediment trap experiment in the deep Sargasso Sea. J. Mar. Res. 36, 493-523. USUI A. (1979) Minerals, metal contents and mechanism of formation of manganese nodules from the Pacific Basin (GH76-I and GH77-I areas). In Marine Geology and Oceanography of the Pacific Manganese Nodule Province

(eds. J. L. BISCHOFFand D. Z. PIPER), pp. 651-679. Plenum. WAKEHAMS. G.. FARRINGTONJ. W.. GAGOSIANR. B., LEE C.. DEBAAR H.. NIAGRELLIG. E., TRIPP B. W., SMITH S. 0. and FREN N. M. (1980) Organic matter fluxes from sediment traps in the equatorial Atlantic Ocean. Nafure 286, 798-800.

Pacific Fe-Mn Appendix A. SamDle Cl-3M Cl-3F ClYF Cl-4L Cl-5 Cl-6A Cl-6B

Cl-at Cl-10 Cl-13 Cl-15 Cl-16 Q-1F c2-1L K2-1 STYX36S

Positions snd compositions of nodules. Depth

msition

(id

11d 21'

5580

10°;9' 155'21'

55:O 55;O 5390

11

800; 7'56'

157O22' 156'23' "

701; 6'11'

11

1?,';6' 157'21' 417' 160'57' 1, 0

AMPH 86C STYX64FF16 3'5;'

11

:I; Kl-F4 Kl-F6.S Kl-i%M Kl-F6L Kl-P8 Kl-RS Kl-9LA Kl-9LB Kl-FlO Kl-F13 Kl-F17 Kl-2 Kl-4 Kl-6 RCl3-45 RCl3-46%' RCl3-70 RC13-72 RC13-73 V18-283 V19-284 CAT&10 CAT&28

" I' 305;' 2028' 2'59' 2OOl'

156'03' 156'37' 158'39' 148'24' 144035' 149OU2' I’

I’

51;o 5390 5520 5650 5300 55Yo 5262 5027 5103 49;9 5065 4904 5065 5115 5283 5151 5210 ‘I

I’

II

II

11

15OO59' 151O57' 168'02' 169'30'

4750 4690 5460 4820

169'30 169'31' 169'29'

4820 5350 5310

11

2001' 4001' 5OOO'

55;o 5250

I’

155O47' I’

K3-1B K3-1 a-1 Top

449

oxide deposits,11

11

!1

11

54;o 5510 z 5480 5240 3940 zl?; 4980 4784 4936 4987 5288 547 1

t41

Fe

Ca

18.60 18.50 20.60 16.10 15.80 20.60 21.40 19.50 20.70 19.90 30.40 27.90

16.70 15.40 13.30 13.20 27.80 16.30 16.30 11.70 11.37 11.54 6.40 7.00 7.55 10.00 17.20

1.82 1.80 1.75 1.68 1.60 1.78 2.02 1.95 1.57 1.82 1.6 1.55 1.7 1.4 1.75 1.80 1.65 1.52 1.94 1.71 2.00 2.00 1.80 1.70 1.10 1.60 1.40 1.80 1.80 1.55 1.60 2.02 1.68 1.75 2.05 1.75 1.80 1.80 1.90 1.80 1.85 1.80 1.90 1.80

2.88 2.80 2.70 4.04 3.10 2.10 1.71 3.60 3.44 3.65 3.00 2.75 3.90 4.40 2.45 3.90 4.01 6.46 5.08 3.91 3.50 2.80 4.40 2.00 4.80 4.10 3.50 3.30 3.30 2.50 2.45 2.54 2.85 4.25 1.75 3.00 1.90 1.60 1.60 2.00 2.45 1.80 1.90 2.80

1.80 1.80 2.30 1.61 1.60 1.75 2.10 1.55 1.90 2.00 1.56

3.10 2.00 1.80 5.33 2.74 2.75 2.35 2.60 3.20 2.00 1.54

:E la:30 17.00 13.90 25.40 11.75 6.37 8.24 15.80 :I:; 20.10 19.70 13.90 21.00 9.44 11.87 lo.98 29.60 7.60 11.98 12.18 15.31 9.86 12.41 16.08 21.80 10.23 8.30 25.90 4.64 33.70 5.71 32.90 8.07 27.50 24.90 8.78 15.20 8.60 12.40 25.30 28.00 6.00 la.30 16.50 18.00 17.60 19.70 18.50 18.70 la.40 14.00 19.30 15.50 20.60 18.90 18.30 18.30 16.30 18.90 13.10 15.90 19.10 17.10 11.27 17.60 16.70 la.30 la.80 19.20 17.80 9.82 6.72 la.20 9.63 20.30 12.30 la.00 15.40 21.40 14.40 17.90 15.20 13.92 20.46 13.45 19.06

Al

Ti 1.09 1.00 0.94 0.92 1.80 1.24 1.17 0.99 0.88 0.80 0.36 0.36 0.50 0.69 1.21 0.99 0.89 0.32 0.47 0.50 1.10 0.56 1.00 0.33 1.11 0.70 0.80 0.80 0.47 0.26 0.34 -

CLI 2360 2200 3400 1930 1200 2700 1780 2600 4530 3980 10700 8300 9300 4800 2600 1700 5890 2990 5100 5960 3560 7670 3280 11100 3540 4940 1280 6180 10100 12100 10900 7920

Ni 4100 3800 6100 4200 2000 4950 3400 5500 8000 6200 12100 10700 10900 9900 4100 3300 10100 3400 5600 7900 5960 9180 4510 10500 5460 6430 1450 10400 9900 11500 11000 10420

0.44 ::A 'Ez 0.77 6800 11000 0.52 12600 12200 1.16 3400 4900 1.20 2300 3000 1.17 2600 4400 1.59 2500 4000 2.00 1700 2600 1.77 1500 2400 1.70 1800 3300 1.53 2400 4400 1.13 6100 660 1.41 1900 2800 1.41 5190 6610 1.50 2100 4ooo 1.37 2100 3400 1.15 1400 3200 0.60 1040 1490 0.64 4610 7480 1.00 3600 6000 1.31 2000 4200 1.24 3600 6500 1.50 2000 4000 1.70 770 1050 1.36 1110 1270

tk, Fe, B, Al and Ti in weight percent. Cu, Ni, Co, Pb a~Id Zn in pp. Results expressed on an air dried basis.

Co

Pb

Zn

4040 990 430 3900 880 410 4200 810 530 3210 640 430 4200 1450 580 4780 1040 560 4990 990 430 3400 730 550 2810 610 670 3280 690 590 2000 350 1420 2200 300 1230 2200 490 1090 2000 560 710 4500 1080 500 3500 770 450 2840 760 750 1010 150 440 1810 380 660 2000 400 720 3330 830 640 1840 280 loo0 1630 390 550 1880 330 1650 1410 3~0 650 2010 410 590 1030 870 470 2470 470 a80 1770 300 1170 1300 140 1850 1500 200 1700 2280 340 1290 1720 390 1070 1300 260 710 2100 550 930 1500 200 1330 2900 780 550 3600 910 480 3600 a80 520 3600 910 500 2600 820 520 3300 980 510 4200 970 550 2600 790 510 1900 300 740 2900 870 490 2030 410 850 3500 780 1390 3700 940 490 3900 790 510 1820 370 250 2480 490 680 3300 610 590 4100 800 500 4ooo 770 590 3400 710 810 2530 900 580 3070 850 570

450

,? (‘ Aplln and D. S. Cronan Appendix B. Sample

bsitions PoSi

.tion

S Kl-2T Kl-2B Kl-4T Kl-4B Kl-5T Kl-5B Kl-6T Kl-6B s68-PC2 MO-32

MIo-33

MIO-34 z:-;z MI0138 KU2-34 CAT0 10 CAM 28 CAT0 32 SOlWl0-IA .WlWlO-2D WIWlO-3A SO'IWO-4B WlwlO-4c SOlWlO-5A STYX4-7 STYX4-10 STYX4-12 STY-X 43 RCl2-87 RC13-46 K2-1 K2-3 K2-10 K2-11 K2-13 K2-14 Cl-l Cl-3 Cl-4 Cl-7 Cl-9 Cl-10 Cl-13 Cl-15 Cl-16 $01Pl, AMPH 116 AMPH 117 AMPH 126 STYX 35 E 2: RC13-66 RC13-70 RC13-72 RC13-71 KK'72-32 KK72-33 Vl&267 V18-275 V18-276 VI a277 VI8-278 v18-279 v18-280 v18-281 ~18-283 V18-284 2::

K3-5

and compositions

lO59'

ow 168 08' 1,

6'00'

169'32' 1,

4oi5

17OO13' I'

40;5

170'58' 11

3'48' go121 6O16' 3O50' 0°35' 1°34' 2'18' 5O37' 7O31' 7'24' 7'12' 7'16' 7'12' 8'31' 8'17'

168Ol6'

168'43' 168'31'

7O29 ’ go37 ’

8'45' 7O41' 4O14' 2'18' 5OJ5' 18 16' 9 50' 11~38' 12'08' 13'08~ 13'38' 14O59' ll"21'

18O39' 8 07' 7'23' 7'18' 6'11' 7Z55'

y q;,

8

7 P' llO26' 12'24' llO59' 4'20' 3O54' 3O54' 4O49' 9O42' 11'56' 12'38'

144'22' 161oOO' 155O47' 155O47 152'38' 151'24' 150'56' 150'46'

161'35' 162'12' :2$:;' 161'03' 12'44' 160'56' 12'42' 160°49' 12'42' 160'45' 12'42' I 60’39 ’ 125142' 160:37' 12'27' 159"23' 12'26' 158'20' 12'51' 156'11' 14'05' 155'08' 6'58' 149O42' 5O47' 15OO13' 3O57' 15OO59' 2'28' 151O57' OOOO' 153O29'

7z39 ’

Depth (m) 4820

WI

of sediments. Fe

0.39 0.63 54;o 0.5i 0.65 55;'O cy4'

2.69 5.28 6.12 7.06 z.4";

521;O 0:44 0.58 5569 0.50 1.05 4457 5569 0.68 5027 0.13 0.40 :z:; 0.47 5496 ;.X& 5134 5288 0:63 5471 0.67 5182 0.54 5668 0.66 5507 0.76 5145 0.50 4751 0.24 4565 0.22 5619 0.54 4162 0.11 5021 0.47 5440 0.51 5451 y.;; 5243 1.32 5354 1.32 5510 1.51 5470 1.49 5170 1.49 4900 1.48 4750 1.47 4660 4750 0.96 1.81 5580 1.61 5560 5510 0.84 1.52 4970 1.28 5170 5390 1.03 1.09 5520 1.13 5650 1.56 5300 4721 1.68 5106 2.45 5151 2.06 4875 2.60 5262 0.87 5065 0.84 5187 0.73 1.47 E$ 1.79 4980 2.00 4784 2.04

4:oo 5.16 5.29 7.45 7.21 0.69 2.74 4.97 ;_;;

4569 4613 2760 3623 3587 3952 4738 4753 4989 5393 4936 4987 5230 5390 4750 4690 4760

cu 4200 7700 10800 11800 8500 9000

Ni

172 122 229 123 186 107 285 127 217 218 160 234 170 104 142 253 183 125 723 240 230 260 60 63 206 127 140 431 151 95 310 217 185 317 -i20 230 207 100 225 145 260 225 172 145 82 60 50 75 204 130 35 200 130 210 188 100 190 120 587 1050 325 546 408 275 458 375 448 425 372 390 381 370 329 390 291 240 464 380 410 395 360 250 533 455 475 551 500 315 420 295 396 250 389 325 68j 600 652 412 E; 644 543 285 225 285 220 274 235 677 400 427 ?70 450 340 478 370

2.45 2.25 1.98 2.10 8.70 2.00 1.95 3.95

5.90 6.40 5.70 6.35 5.10 5.60 S.50 6.55

i.;;

;.;3$

5.80 4.85 8.61 6.52 5.91 5.95 5.08 5.31 5.28 5.92 6.24 6.36 5.62 6.39 6.54 6.77 3.69 3.56 2.90 5.46 5.19 7.43 7.52

7:50 1.45 1.40 1.70 2.75 3.00 7.90 2.40 2.45 3.45 27.00 28.50 2.85 36.50 6.40 2.30 2.05 1.35 2.35 1.95 2.00 2.50 2.65 4.00 12.60 5.35 1.95 2.10 1.90 4.00 2.65 2.55 2.35 2.45 2.10 3.45 3.00 2.95 4.20 1.15 2.95 6.30 1.95 6.60 2.85 4.20

4:40 5.55 3.00 5.70 6.40 7.15 5.25 6.40 5.95 6.15 2.35 2.10 6.35 0.84 6.20 5.85 5.35 7.20 6.80 5.80 6.05 5.70 5.40 6.00 4.40 6.35 5.95 5.85 6.80 5.90 5.75 5.95 6.10 6.25 6.05 5.70 5.55 6.00 5.33 4.35 4.35 3.85 6.20 6.20 6.10 6.50

1100 12300 8800 6600 5200 6800 4500 4500 3800 2200 4000 3200 18000 6200 5000 6200 3600 2500 2500 4000 3600 6800 3000 2200 4400 590 3600 3200 2800 4200 5400 7700 7400

1.65 5.56 0.43 1.64 0.04 5.00 1.65 6.47 1.58 7.30 1.73 4.30 4.15 10.50 0.66 2.83 1.84 7.79 1.84 7.90 1.84 7.33 1.75 9.22 1.70 5.32 1.55 5.20 0.12 0.60 0.08 0.39 0.10 0.51

9.40 30.20 5.00 11.45 2.10 18.60 9.40 25.50 2.20 2.00 2.65 2.75 2.15 2.15 34.70 34.30 31.40

5.15 1.90 7.95 6.00 6.70 4.25 4.40 2.75 6.65 6.25 6.25 6.50 5.30 5.15 0.82 0.73 0.90

3600 513 453 1700 155 100 4500 115 1100 5:: 650 6000 694 850 1400 346 550 1800 1027 1300 4200 174 115 430 270 9100 447 245 7900 6100 399 335 13300 414 295 440 4600 529 355 3300 449 55 45 500 50 35 87 45

* = below detection limit. t+, Fe, @ and Al in weight percent.

6:65 7.04 4.76 6.48 6.69 6.62 2.29 1.85 6.26 1.04 6.33 5.95 ;.z$

.

5.74 5.98 5.82 5.67

4.97

‘II, c‘u,

7900

4300 11300 600 2500 6200 1800 5200 10300 13000 5100 9100 8500 10000 3100 1000

5900

Ni, Co, Pb and 7~ in ppm.

co

Pb

Zn

51 80

17 35 42 39 49 42 35 45 50 49 74 21 30 59 17 53 69 40 30 34 62 39 12 27 36 19 33 33 39 18 44 70 58 43 52 52 35 24 65 84 56 76 80 60 63 49 98 84 38 68 60 50 63 77 53 55 78 78

75 119 123 139 124 137 136 247 368 493 259 172 101 211 82 136 446 416 335 205 282 183 76 59 273 49 234 230 474 235 160 121 140 130 118 125 116 174 143 132 122 135 132 138 140 149 155 245 196 177 178 443 104 95 179 128 160 166

;1 74 90 :: 70 137 110 2: 80 55 123 100 105 :; 125 70 ;z 80 14 ;: 80 137 172 185 205 210 205 205 215 140 265 225 135 220 185 160 165 165 215 255 255 255 293 120 120 115 199 218 247 261 237 68

52 176 11 50 __

;: 241 251 226 77 229 265 233 211 213 192 27

25

-

;I:

I

83 81 78 70 52 45

163 158 271 49 26 26

l

14

l

17

l

451

Pacific Fe-Mn oxide deposits. 11 AppendixC. Caaposition of the hydmxylaminehydrochloride soluble fraction of S.W. Pacific sediwnts, expressed as pm of the W sediment. t&

Fe

IL

Ni

CoPbznAl

Kl 28 2T Kl

5270 3102

3572 9809

108 112

92 62

55 35

22 34

2;

;g

;;

Kl 4T Kl 4B

3i300 9956

106 116

42 62

51 ?a

29 33

50 98

6517 4176

35 32

Kl 5T

5219

5696

Kl 5B Kl 6~ Kl 6~ .%a 2 Ml0 32 MI0 33 MO 34 MI0 35 MI0 36 n70 38 KK72 34 CAT0 10 CAT0 2e CATS j2 .%YMO 1A SO'IWlO 2D .WIWO 3A .WlUlO &B .solw10 4c Sol%'10 5A sm4 7 xYx410 sTrx412 STYX 43 1x13 46 K21

YE.;

5491 4600 7029 5746 1141 3616 3924 2414 6552

9240 128 83 102 129 110 121

6;; 4896 7974 2652 7128

;79 1;; 136 73 104 49 79 70 121 142

K3 K3 2 K3 3

16330 15230 14450 1060

K3 5 4

1008 730

1180 930

Cl 3 Cl 4 Cl 1

Cl

9

Cl Cl Cl Cl

10 13 15 16

ZO'Pl? AWHl16 AWHl17 AMPH126 m

35

SEi 2: KK72 32 !s:: ;; RCl3 70 RCl3 72 RC13 73 VI0 267 Vla 275 Vl8 276 Vl8 277 via 280 Vl8 281 vla 283 wa 284

1

19390 18350 869 16040 14310 17600 17240 15810 16740

2;

a702 6138 7582 9860 7281

7750 109OO 13800 10290 2815 1228 10940 2455 8060 '1190 10320 4602 12750 12440 12920 12120 15850 11660 14350 19420 15740 9180 11375 0988 7463 10520 11320 18430 10350 9900 19490 17940 10550 a118 6216 10330 2780 7125 15690 19850 17360 1540 4444 5655 6675 19560 19760 17140 20520 10950 7980 1423

K23 K2 10 K.2 11 K2 13 K2 14 Cl 1

3505 5950 7686 4573 1523 593 4125 --1185 3458 4270 3680 13000 13240 14400 14840 14780 13600 14650 7824 19530 18020 1424 16130 14030 11420 11760 10860 16800 17140 22880 20470 22110 6426 a808 7616 14580 1695 13740 16860

10690

57 113 165 93 ji 15 117 31 97 117 loa 123 164 205 263 la4 210 183 145 286 224 145 254 207 146 161 162 243 386 431 259 381 207 187 171 277 41 210 240 248 260

57 92 52 143

;;

$i

44 63 53 90 a0 :;

27 26 24 39

42 lo9 380

9; 41 106

23

b6

32

95

47 58 114 41 1;

46 57

24 26

95

;;

51

50

:'9

::

;@ 5 3 24 5 2?

44 58 268 208 284 293 275 247 254 122 267 274 152 344 3110 223 195 la7 258 568 799 350 471 165 210

193 392 19

;i2 317 234

80 31 18 37 123

i88 145 154 178 157 165 166 153 99 218

173 137 lil 118 97 211 193 227 240

‘2 112 11 158 18 129 109 235 231 ;:

237 227 37 58 34

23 18

1:

4294 3379 6494 6120 1791 1072 864 3424 5130 4318 4680 4147 3564 365e 4978 6944 5270 -873 340 6696 680 4oo4 6048 6024 1989 2346 2664 2440 2140 2725 1320 2904

48

193 102

183 220 178 224 200 178 200 170 15

207 225

53 6749

56 53 94

6;: 757 592 232 220 276 234 384 321 23

3:: 228 195 228 224

3; 16 32

n

39 21 50 23 411 24 30 32 22 28 36 5

;:E :59 3360 60 41 E 44 3026 3200 50 :z 113 101 :;

;: 61 33

z:: 3151 1958 2592 2310 8874 6534 4228 2044 1023 3135 3131

;: 101 48 11 22 15

:z 1364 1606 1965 2525 3380 3325 3534

21

55 181

3

31

i%;: 4557 495

:

14 11

480 413

j0

32 69 63 53 25 40 41 45 54 43 24 64 51 101 47 72 68 314 280 64 232 93

25 5; 22 74 g 40 26 26 29 14 15 20

2

122

2: ;i 2:

101 213 2:: 101 108 125 42 90 118

::