Geochemistry of three cores from the East Pacific Rise

EARTH AND PLANETARY SCIENCE LETTERS 12 (1971) 425-433. NORTH-HOLLAND PUBLISHING COMPANY

GEOCHEMISTRY

OF THREE

CORES FROM THE EAST PACIFIC RISE*

Michael BENDER, Wallace BROECKER, Vivian G O R N I T Z * * , Ursula MIDDEL, Robert KAY, Shine-Soon SUN and Pierre BISCAYE Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964, USA Received 4 June 1971 Revised version received 30 August 1971

We have determined sedimentation rates of a core from the crest and two cores from the flank of the East Pacific Rise from the depth variations of their excess 23°Th content. We have also analyzed composite strip samples from these three cores for [Mn], [Fe], [Ni], SiO2], [A1203], [NaCI], and mineralogy, and determined the rare earth contents and isotopic composition of lead, strontium, and uranium in the crest core. The Mn accumulation rate of the crest core is 25 times higher than the world average, supporting the conclusion of Bostrom and Peterson [ 1] that at least some of the elements in these sediments derive from local volcanism. The relative concentrations of the rare earth elements and the isotopic composition of U and Sr in the crest core indicate that these elements derive from sea water. On the other hand, the isotopic composition of lead in the crest core indicates that the lead is mostly of local volcanic origin.

1. Introduction In a series of papers, Bostrom and Peterson and their coworkers have studied the chemistry and genesis of sediments from the East Pacific Rise. They have found that these sediments are enriched to a remarkable extent in iron, manganese, arsenic, boron [ 1 - 3 ] , mercury [4], uranium [5], and other elements. They noted that the East Pacific Rise is a center of sea floor spreading and high heat flow, and concluded that the unusual chemical composition of these sediments is due primarily to precipitation of insoluble metals " f r o m volcanic emanations that debouch on the crest of the rise". An alternative explanation for the genesis of these sediments is that iron, manganese and related elements are precipitated from sea water on the East Pacific Rise at the same rate as in other areas, but their concentration is higher on the rise because the authigenic precipitates are not diluted very much by either detritus or the skeletons o f microorganisms. If this is Lamont-Doherty Geological Observatory of Columbia University contribution no. 1584. ** Present address: Institute for Space Studies, 112 St. and Broadway, New York City. *

the case, then manganese must be accumulating in these sediments at a rate comparable to that in areas of normal pelagic sedimentation. On the other hand, if the manganese in these sediments is derived from submarine volcanism, then it must be accumulating unusually rapidly on the Rise. Bostrom [6] estimated accumulation rates of iron in sediments around the East Pacific Rise. He concluded that iron is being deposited more rapidly on the crest than in nearby areas. As a more definitive test, we have determined the rates at which manganese is accumulating in a core from the crest and two cores from the western flank of the East Pacific Rise at 17°S. The sedimentation rates of these cores were determined by measuring the exponential decrease in 23°Th. The content of CaCO3, Fe, Mn, Ni, U, Th, SiO2, and A120 3 were measured; the mineralogy was studied, and the isotopic composition of the U and Th were analyzed in these three cores. We have also studied the rare earth content, the strontium isotope composition, and the lead isotope composition in the ridge crest core in order to determine which of these elements derive directly from ridge volcanism and which are coprecipitated from sea water.

426

M. Bender et al., Geochemistry o f three Pacific cores

Table 1 Location and depth of the cores in this study. Core

Location

Depth (m)

VI9 54

17°02'S 1t3°54'W

2830

V19 61

16°5TS 116°18'W

3407

V19-64

16°56'S 121°12'W

3540

2. Core locations and geologic setting The three cores analyzed in this study (table 1) were raised on cruise 19 of the R/V VEMA during a traverse across the East Pacific Rise at 17°S. The Rise topography in this area is shown in fig. 1, along with the heat flow data and magnetic lineations. The sediment cover in this area is either thin or nonexistent and is always less than 100 m [7]. The sea floor spreading rate at 17°S is about 6 cm yr -1 [8].

3. Chemical methods and results

HEAT

FLOW +

+ +

o

+

T~ 6i

+ + +

?E to

4

+.++ +~1

++

o ::k

+ ¢?+

%+* +

+ -t-

+ L

+++;+*%,

+'+

,+

i

V19 -64

2,000 mr'-

I

,

V I 9 v19 -6t -54

t

,ooo L ,' MAGNE TICS

IIIII i T i l l | 5

0

BASEMENT 150°W

125 °

IIIHIIII

I ~ I I ' Jl,ilil,llH

120 °

115 °

5 AGE

(m. yr)

liO °

I05 °

LONGITUDE

Fig. 1. Heat flow, topography and magnetics across the East Pacific Rise at 17°S. Circles are heat flow data for the V19 traverse; pulses are data from nearby cruises. Magnetic data are from Herron [71.

238U, 234U, 232Th, and 23°Th contents of samples from cores V 1 9 - 5 4 , 61, and 64 (table 2) were obtained using standard radiochemical procedures [9, 10]. The unsupported 230Th was calculated by subtracting the 234U activity from the 230Th activity. Since in core V 1 9 - 5 4 , 234U/238U is > 1.00 this procedure is not precisely correct, but introduces a negligible error into the calculated sedimentation rates. In cores V 1 9 - 6 1 and V 1 9 - 6 4 the [U] was too low to permit accurate measurement of the 234U/238U; we assumed that in these cores the 234U/238U is 1.00. The logarithm of the unsupported 23°Th content is plotted versus depth for samples from each of the three cores in fig. 2. The sedimentation rate is given by the core length over which the unsupported 230Th decreases by one half, divided by the 23°Th half life (75 200 yr). Mn, Fe, and Ni were determined in composite strip samples (continuous wedges) from V 1 9 - 5 4 , 61, and 64 by atomic absorption [ 11 ]. CaCO 3 in these cores was analyzed gasometrically. Chloride was determined by Mohr titration. Mn, Fe, Ni, CaO, A1203 and SiO 2 were measured in the strip samples from cores V 1 9 - 5 4 , 61, and 64 by X-ray fluorescence, using an adaptation of the fusion-heavy absorber method of Rose et al. [ 12]. The fusion mixture consists of 50 mg of sample, 100 mg Li2CO 3, 100 mg La203, and 900 mg Li2B407 Since the samples contained large amounts of CO 2 and H20 , they were ignited prior to fusion in graphite crucibles at 1100°C, and the weight loss was recorded. The resulting beads were then crushed and pressed into pellets. Standards were prepared in the same

427

M. Bender et al., Geochemistry o f three Pacific cores

Table 2 Uranium and thorium isotope concentrations. Depth in core (cm)

[CaCO3] (%)

[U] (ppm)

234U 23SU

V19-54

18 48 86 114 150 200 305 400

59 67 61 64 60 60 60 58

4.76 4.96 4.93 4.30 5.25 6.90 5.60 4.55

1.13 1.15 1.09 1.13 1.12 1.11 1.07 1.03

V19-61

15 53 93 128 160 208 260

v19-64

11 35 6o 85 157 218 265

Core

23OTh (dpm gm-1 )

Unsupported 23OTh (dpm gm-I )

0.2 0.2 0.2 0.3 0.2 0.l 0.1 0.8

17.5 14.0 11.2 10.8 11.1 10.1 6.68 3.79

13.6 9.8 7.3 7.2 6.8 4.5 2.3 0.35

0.37 0.71 0.47 0.45 0.41 0.56 0.77

0.3 0.3 0.2 0.1 0.1 0.1 0.1

17.5 12.1 5.35 3.23 2.05 1.04 0.64

17.2 11.6 5.0 2.9 1.8 0.63 0.08

0.20 0.27 0.35 0.32 0.52 0.34 0.36

0.05 0.1 0.1 0.2 0.6 o.3 0.4

15.4 14.3 11.4 5.35 1.53 O.35 0.36

15.2 14.1 11.1 5.1 1.15 0.10 0.10

manner from artificial mixtures of spec pure oxides. Because of its low concentration, nickel was measured directly in the unignited powder. The concentrations of 10 rare earth elements and Ba were analyzed in V 1 9 - 5 4 by stable isotope dilution mass spectrometry. The spike solutions are those used by Gast et al. [13], who also described the analytical method. The isotopic composition of strontium in the carbonate free phase of the V 1 9 - 5 4 strip sample was obtained by totally dissolving the carbonate in pH 5 buffer (NaAc+HAc) and determining the 87Sr/86Sr ratio of the remaining water-cleaned oxides mass spectrometrically. The 87Sr/86Sr ratio is 0.708 -+ 0.001. Lead isotopic measurements were done on the carbonate-free phase of a sample from the trigger weight core raised at station V 1 9 - 5 4 ( 2 3 - 2 6 cm). The sample was similarly treated using a buffer solution with pH = 5 to dissolve carbonates. Remaining

232Th (ppm)

solids were cleaned by ultrasonic treatment in triple distilled water, and then dried at 100°C. A 0.2262 gram sample was weighed and dissolved in 50 ml triple distilled HNO 3. Using Ba(NO3) 2 coprecipitation, the Pb silica gel method (Tatsumoto, personal communication, 1970) and the double spike method [14] we carried out two sample- and three sample-plus-double-spike mass spectrometry runs. The blank for each run is about 0.04%. The concentration of lead in the carbonate free phase is 370 ppm. The lead isotopic composition is as follows (absolute ratios): 2°6pb/2°4pb = 18.140 -+ 0.1% 2°8pb/2°4pb = 37.862 + 0.15% 2°6pb/2°7pb = 1.1671 + 0.1% 2°Tpb/2°4pb = 15.543 -+ 0.1% 2°8pb/2°6pb = 2.0872 + 0.05% The mineralogy of the core samples was examined by X-ray diffraction, using a Siemens diffractometer. The samples were X-rayed untreated, after leaching

M. Bender et al., Geochemistry o f three Pacific cores

428

Table 3 Bulk chemical composition of cores from the East Pacific Rise. Core

Mn (%)

Fe (%)

Ni (ppm)

CaCO 3 (%)

SiO2 (%)

AI20 3 (%)

NaC1 (%)

V19 54

3.8* 3.3**

10.4" 10.5"*

204* 198"*

65

5.1"

~< 0.3*

3.6

VI9 61

0.41" 0.38**

2.13" 1.93"*

55* 50**

90

2.6*

0.6*

V19-64

0.21" 0.17**

1.26"

55*

90

2.0*

< 0.3*

1.06"*

47**

3.5

* X-ray fluorescence. ** Atomic absorption.

Table 4 Rare earths in V19--54. La 19.1 ppm Ce 5.47 Nd 15.2 Sm 3.25 Eu 0.99 Gd 3.90

Dy 4.73ppm Er 3.63 Yb 3.73 Lu 0.57 Ba 970

Table 5 Accumulation rates of different phases in EPR sediments.

Core

Sed. Rate (cm/10 3 yr)

CaCO3 Sed. Rate (cm/10 3 yr)

Detritus Sed. Rate (cm/10 3 yr)

Mn Acc. Rate (mg/cm 2 10 3 yr)

V19-54 V19-61 V19 64

1.50 0.70 0.45

0.97 0.63 0.41

~< 0.04 ~< 0.01 ~< 0.01

35 1.7 0.54

with s o d i u m acetate-acetic acid b u f f e r solution (pH 5)

4. Discussion of the results

to isolate iron oxide(s) and silicates, and after leaching with h o t 2N HC1 to isolate silicates. Results for all e l e m e n t a l analyses f r o m the strip samples from the three V I9 cores are given in tables 3 and 4. S e d i m e n t a t i o n rate and a c c u m u l a t i o n rate data are given in table 5. All a c c u m u l a t i o n rates are caiculated assuming that the density o f these cores is 0.7 g cm -3.

4.1. M i n e r a l o g y All three u n t r e a t e d samples c o n t a i n e d calcite as the d o m i n a n t phase, but V 1 9 - 6 1 and V 1 9 - - 6 4 also s h o w e d trace a m o u n t s o f quartz. No crystalline iron or m a n g a n e s e mineral was d e t e c t e d , a l t h o u g h friable l u m p s o f r e d d i s h - b r o w n material were observed u n d e r the binocular m i c r o s c o p e . The calcite can be attri-

429

M. Bender et al., Geochemistry o f three Pacific cores

buted to the presence of coccoliths and foraminifera. The acetic-acid leached samples were heated for 2 hr each at 500°C, 650°C, and 900°C. All three samples remained amorphous up to 900°C, at which temperature hematite plus a few lines of an unidentified phase (possibly jacobsite, MnFe204, or a Mn oxide) appeared. The hydrochloric acid-insoluble residue in all three cases consisted of a mixture of quartz and calcic plagioclase (labradorite). 4.2. S e d i m e n t a t i o n rates The logarithmic decrease in unsupported 230Th with depth is shown in fig. 2. The straight lines through the points are drawn giving little consideration to those points with low absolute values of excess 230Th, because there is a high uncertainty in these numbers. The consistency of the results for these three cores compares favorably with published results (for a general review of excess 230Th dating of sediments see Ku et al. [15] ) and must give close approximations to the true sedimentation rates. The excess 230Th content of the 400 cm sample of core V 1 9 - 5 4 falls far below the value expected from the higher samples. The 234U/238U ratio of this sample (1.03) is below the expected value of about 1.07. These results suggest that this sample may be considerably older than the overlying sediments due to a hiatus in deposition.

i

"e~®

°"o

'

s e d i m e n t a t i o n rates

The extremely low 232Th and A1203 concentrations in these cores indicate that their content and sedimentation rate of detritus is very low. Assuming that the 232Th content of continental detritus in deep sea sediments is 10 ppm [16], the detritus content of the three cores in this study can be calculated. The detritus sedimentation rates for the cores (in cm/

,60

VI9-54

'

260

'

36o

'

4oo

i VI9-61

o

(.9

s

=0 . 7 0

cm

Q. a

o

N o

(f) (D bJ 0 X Ld

OI I00

4.3. CaCO 3 s e d i m e n t a t i o n rates Sedimentation rates of CaCO 3 in units of cm/103 yr, are calculated by multiplying the bulk sedimentation rate by the percentage carbonate content. The carbonate sedimentation rates are 0.63 and 0.41 cm/ 103 yr for V19-61 and V 1 9 - 6 4 , respectively; 0.28 and 0.42 cm/103 yr for two other southeast Pacific cores [15], RC8-93 and V 2 1 - 4 8 , respectively; and 0.93 cm/103 yr for V 1 9 - 5 4 .

4.4. D e t r i t u s

i

®

200

300

400

V 19-64

O

0

3

I00

=

200

m i-

Y F'

300

400

DEPTH IN C O R E ( C M ) Fig. 2. Excess 2 3 ° T h vs. d e p t h i n the cores.

430

M. Bender et al., Geochemistry of three Pacific cores

103 yr) is calculated by multiplying the detritus content (in %) by the sedimentation rate. Because of the low 232Th content of these cores, the uncertainty in its measurement is large, and upper limits only are given. The calculated values (table 5) of a few tenths of millimeters per thousand years are extremely low. 4.5. Manganese accumulation rates Bender et al. [17] have determined the manganese accumulation rates in 38 pelagic sediment cores, Rates ranged from 0.2 to 3.2 mg Mn cm -2 10-3 yr -1. The average value was 1.3 mg cm -2 10-3 yr -1. The manganese accumulation rate of V 1 9 - 5 4 is 35 mg cm -2 10-3 yr -1, or an order of magnitude higher than the previously observed maximum. We interpret the manganese accumulation rate of this core as support of Bostrom and Peterson's [1] conclusion that the high content of manganese (and other transition metals) in East Pacific Rise sediments is directly or indirectly due to ridge volcanism. The manganese accumulation rate falls off rapidly on the western flank of the Rise. The manganese accumulation rate of V 1 9 - 6 1 (1.7 mg cm -2 10-3 yr -1) is comparable to the average manganese accumulation rate of normal pelagic sediments. The manganese accumulation rate of V19 64 is 0.54 mg cm -2 10- 3 yr -1, or a factor of two less than the average manganese accumulation rate in normal sediments. 4.6. Uranium contents and 2 3 4 U/2 38 U ratios Fisher and Bostrom [5] reported that sediments on the East Pacific Rise have unusually high uranium contents. Our results are in agreement with this conclusion. V 1 9 - 5 4 has a uranium content of about 15 ppm on a carbonate-free basis - about a factor of six above the concentration in normal pelagic sediments [16]. All of the 234U/238Uratios listed for V 1 9 - 5 4 are well above 1.00. The 234U/238Uratio in a sample from the top of the core was determined to an especially high accuracy; it was 1.16 +- 0.01. These ratios indicate that the uranium in these cores comes from sea water, and is probably adsorbed by or coprecipitated with the iron and manganese hydroxides. Similar results and conclusions have been reported by Veeh and Bostrom [5] for East Pacific Rise sediments and by Ku [10] for sediments from the Red Sea hot brines. 4.7. Rare earth contents o f V19 54 The rare earths in V 1 9 - 5 4 (table 4) occur in the

2000

1000

D ~

Mn nodule average Phosphorite Sediment average

o

V19-54

m

/~ / \ /

~

ater

500

I-

no

I00

~"

50

I0

LO Ce

Fig. 3. Chondrite normalized rare earth distribution in the strip sample from V19-54 compared with the distribution in sediments and in sea water. Data for sea water (shaded area) are from Goldberg et al. [18] and Hogdahl et al. [19]. Data for sediments and nodules are from Haskin et al. [20] and Ehrlich [21], respectively. Absolute concentrations in sea water are about six orders of magnitude less than in V19-54.

same proportions as in sea water. Fig. 3 shows the close similarity of V 1 9 - 5 4 and the mean chondrite normalized patterns of North Atlantic deep water and East Pacific surface water [18, 19]. A diagnostic feature in the rare earth distribution is the twofold depletion of Ce relative to La and Nd, the neighboring rare earths. This depletion is not found in igneous rocks or sediments [20]. For comparison, an average sediment pattern is plotted on fig. 3. Goldberg et al. have noted that the Ce enrichment of Mn nodules complements the depletion in sea water. Thus, rare earths in Mn-Fe-rich sediment and nodules are clearly different. Tile detrital material in V 1 9 - 5 4 is nil, and X-ray determinations of Y (similar to heavy rare earths) show that most of the rare earths are in the noncarbonate fraction. We propose that most of the rare earths in this core have been removed without fractionation from sea water by adsorption or on coprecipitation with the Mn-Fe fraction of the sediment.

431

M. Bender et al., Geochemistry o f three Pacific cores I

]

t

I

I

sedimentsP°cisegments/ fic Atlonfic

1

1

V19- 54,1~

,.oI

/ StHeleno

elupe

//;__

1540~p~B.6

I

~-'~arld, ge samples

5.501 l 17.50

n 18.00

;8.50

19.00

I 1950

I 20.0("

t 20.50

21.00

p b 206 / p b 204

Fig. 4. Comparison of the 2°Tpb/2°4pb and 2°6pb/2°4pb of the carbonate-free fraction of V19-54 (plus inside box) with Pacific pelagic sediments, manganese nodules, oceanic volcanic rocks and dredge samples. 4.8. Isotopic composition o f the lead in V 1 9 - 5 4 In fig. 4 the 207pb/204pb and 2°6pb/2°4pb from V 1 9 - 5 4 is compared with ratios in pelagic sediments (from Chow and Patterson [22]), manganese nodules (from Reynolds and Dasch [23]), oceanic volcanic rocks (data from fig. 6 of Oversby and Gast [24]) and dredge samples [25]. Chow and Patterson's data are corrected to absolute ratios with their CIT standard measurements by comparison with the ratios of Catanzaro [26]. Since the isotopic composition of lead in Pacific deep water has not been measured, we have no simple test for the origin of the lead in the oxide phase of V19-54. However, the fact that the lead isotope composition of this sample is clearly different from that of all other analyzed sediments (including Mn nodules), taken together with its similarity to lead in some oceanic volcanic rocks, suggests to us that the lead derives at least partly from local volcanism.

5. Summary and discussion The unusually high manganese accumulation rate of V 1 9 - 5 4 adds further evidence to the prevalent belief that the exotic composition of sediments near the crest of the East Pacific Rise is associated with ridge volcanism. To understand the genesis of these sediments, it is essential to elucidate the sources of the constituent elements. Our data strongly suggest that the U, Sr, and REE are derived from sea water. The isotopic composition of lead indicates that that element is derived from ridge volcanism. Evidence from other work suggests that iron is derived from volcanism. First, Spencer et al. [27] have found a mid-depth maximum for iron in the Eastern Pacific similar to that found by Clarke et al. [28] for 3He. Second, Corliss [29] has shown that the iron content of basalts is reduced by reaction with sea

432

M. Bender et al., Geochemistry o f three Pacific cores

w a t e r d u r i n g cooling, a n d h e h a s suggested t h a t this is the source o f iron in the East Pacific Rise a n d similar s e d i m e n t s . T h e origin o f t h e m a n g a n e s e in these s e d i m e n t s is p r o b l e m a t i c . T h e h i g h m a n g a n e s e a c c u m u l a t i o n rate at first suggests a volcanic origin. H o w e v e r , Corliss f o u n d o n l y a very small decrease in the m a n g a n e s e c o n t e n t o f h o l o c r y s t a l l i n e basalts t h a t h a d c o o l e d in the p r e s e n c e o f sea w a t e r a b o u t 0 . 0 1 % o f the t o t a l weight o f the rock, c o m p a r e d w i t h a b o u t 1.5% for iron. This suggests t h a t the m a n g a n e s e m a y in fact be r e m o v e d f r o m sea w a t e r b y c o p r e c i p i t a t i o n . This conclusion is surprising a n d c o n t r a r y to t h a t o f earlier workers. H o w e v e r , the h y p o t h e s i s o f a volcanic origin for m a n g a n e s e c a n n o t be a c c e p t e d unless t h e r e q u i r e d v o l u m e s o f m a n g a n e s e - p o o r altered basalt are f o u n d . ( G r e e n s t o n e s a n d spillites f o r m e d b y m e t a m o r p h i s m o f basalts near the m i d - o c e a n ridges m a y r e p r e s e n t such M n - p o o r residues.)

Acknowledgments This research was s u p p o r t e d b y A t o m i c E n e r g y C o m m i s s i o n C o n t r a c t A T ( 3 0 - 1 ) 3 1 3 9 . T h e cores were raised b y t h e L a m o n t - D o h e r t y ships R / V V E M A a n d R / V C O N R A D o n cruises s u p p o r t e d b y c o n t r a c t s O N R N 0 0 0 1 4 - 6 7 - A - 0 1 0 8 - 0 0 0 4 a n d N a t i o n a l Science F o u n d a t i o n G r a n t G A - 1 0 6 3 5 . T h e h e a t flow data in fig. 1 are f r o m a s u m m a r y m a d e available to us b y David Epp. We are g r a t e f u l t o Ellen H e r r o n for perm i t t i n g us to i n c l u d e u n p u b l i s h e d m a g n e t i c d a t a in fig. 1. We also wish t o t h a n k M a r y l o u Zickl for t y p i n g the m a n u s c r i p t a n d T h o m a s Z i m m e r m a n for d r a f t i n g the figures.

References { 1] K. Bostrom and M.N.A. Peterson, Precipitates from hydrothermal exhalations on the East Pacific Rise, Econ. Geol. 61 (1966) 1258. [2] K. Bostrom and M.N.A. Peterson, The origin of aluminium-poor ferro-manganese sediments in areas of high heat flow on the East Pacific Rise, Marine Geol. 7 (1969) 427. [3] K. Bostrom, M.N.A. Peterson, O. Joensuu and D.E. Fisher, Aluminum-poor ferromanganoan sediments on active oceanic ridges, J. Geophys. Res. 74 (1969) 3261.

[4] K. Bostrom and D.E. Fisher, Distribution of mercury in East Pacific Rise sediments, Geochim. Cosmochim. Acta 33 (1969) 743. [5] D.E. Fisher and K. Bostrom, Uranium rich sediments on the East Pacific Rise, Nature 224 (1969) 64. H.H. Veeh and K. Bostrom, Anomalous 234U/238U on the East Pacific Rise, Earth Planet. Sci. Letters 10 (1971) 372. [6] K. Bostrom, Submarine volcanism as a source for iron, Earth Planet. Sci. Letters 9 (1970) 348. [7] E. Herron, Sea floor spreading and the Cenozoic history of the east central Pacific, (in preparation). [81 L.H. Burckle, J. Ewing, T. Saito and R. Leyden, Tertiary sediment from the East Pacific Rise, Science 157 (1967) 537. M. Ewing, R. Houtz and J. Ewing, South Pacific sediment distribution, J. Geophys. Res. 74 (1969) 2477. [9] T.-L. Ku, An evaluation of the U234/U238 method as a tool for dating pelagic sediments, J. Geophys. Res. 70 (1965) 3457. T.-L. Ku, Uranium series disequilibrium in deep sea sediments, Ph.D. thesis (1966) Columbia University. [10l T.-L. Ku, Uranium series isotopes in sediments from the Red Sea hot-brine area, in: Hot Brines and Recent tteavy Metal Deposits in the Red Sea, E.T. Degens and D.A. Rose, eds. (Springer Verlag, New York, 1969). [11] M.L. Bender and C. Shultz, The distribution of trace metals in cores from a traverse across the Indian Ocean, Geochim. Cosmochim. Acta 33 (1969) 292. [121 H.J. Rose, I. Adler and F.J. Flanigan, X-ray fluorescence analysis of the light elements in rocks and minerals, Applied Spectroscopy 17 (1963) 81. [13] P.W. Gast, N.J. Hubbard and H. Wiesmann, Chemical composition and petrogenesis of basalts from Tranquillity Base, Proc. Apollo 11 Lunar Sci. Conf. 2 (1970) 1143. [ 14] W. Compston and V.M. Oversby, Lead isotopic analysis using a double spike, J. Geophys. Res. 74 (1969) 4338. [15] T.-L. Ku, W.S. Broecker and N. Opdyke, Comparison of sedimentation rates measured by paleomagnetic and the ionium methods of age determination, Earth Planet. Sci. Letters 4 (1968) 1. 116] D. lteye, Uranium, thorium, and radium in ocean water and deep sea sediments, Earth Planet. Sci. Letters 6 (1969) 112. [17] M.L. Bender, T.-L. Ku and W.S. Broecker, Accumulation rates of manganese in pelagic sediments and nodules, Earth Planet. Sci. Letters 8 (1970) 143. [18] E.D. Goldberg, M. Koide, R.A. Schmitt and R.tt. Smith, Rare earth distributions in the marine environment, J. Geophys. Res. 68 (1963) 4209. [19] O.T. ttogdahl, S. Melsom and V.T. Bowen, Neutron activation analysis of lanthanide elements in sea water, Advances in Chemistry Series No. 73 (1968) 308. [201 L.A. Haskin, F.A. Frey, R.A. Schmitt and R.H. Smith, Meteoritic, solar, and terrestrial rare earth distributions,

M. Bender e t aL, Geochemistry o f three Pacific cores

[21]

[22]

[23]

[24]

[25]

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