18. major element composition of leg 92 sediments1 ... · mitchell w. lyle, college of...

18. MAJOR ELEMENT COMPOSITION OF LEG 92 SEDIMENTS1

Mitchell W. Lyle, College of Oceanography, Oregon State University2

ABSTRACT

The major element composition of Leg 92 sediments reflects the input of hydrothermal precipitates from the EastPacific Rise and extinct Mendoza Rise plus minor amounts of terrigenous detritus. The basal sediments are a mixture ofhydrothermally precipitated ferromanganese oxyhydroxides and carbonates. In present and ancient sediments deposited200 km or more from the rise crest, however, the amount of hydrothermal precipitates in the sediments decreases mark-edly. The distal deposits of hydrothermal particulates are also richer in iron because of fractionation by sedimentationprocesses. Slowly accumulating aluminosilicate detritus becomes a more important fraction of the sediments far fromthe rise crest as a result of the decrease of hydrothermal sedimentation.

INTRODUCTION

One of the goals of the Leg 92 drilling was to studythe past and present geographic distribution of hydro-thermally derived sediments from the East Pacific Rise(EPR). The drilling transect was located at 19°S for avariety of reasons; among other things, the region is in aflow line from the fastest-spreading segment of the mid-ocean ridge system, and the region lies underneath a hy-drothermal plume emanating from the EPR (Lupton andCraig, 1981; Reid, 1982). The region lacks large inputsof organic matter to the sediments, and thus postdepo-sitional modification of the sediments during early dia-genesis is at a minimum. For example, Gieskes et al.(this volume) show evidence only for dissolution of cal-cite in the upper portions of Sites 597 and 598, and pos-sibly 599, and no evidence for formation of new diage-netic minerals. There is no evidence that redox processeshave ever modified the composition of the sediments sig-nificantly. The present-day distribution of nitrate andammonia in the pore waters at all the sites in the Leg 92transect (Gieskes et al., this volume) indicates that thetypical pE of the sediments is too oxic for even the re-duction and remobilization of manganese, the most re-dox-sensitive of the common transition metals. There isalso no evidence for any long-term changes in produc-tivity (e.g., changes in carbonate accumulation; Leinen,this volume) that could cause less oxic sedimentary re-dox conditions in the past.

The input of continental detritus is also very low.Sources for detrital material to this region are at least4000 km away (Dymond, 1981), and the data of Blooms-tine and Rea (this volume) indicate that the eolian detri-tal component has accumulated 1 to 2 orders of magni-tude more slowly than in similar regions in the NorthPacific. It is therefore an ideal place to study the com-position of precipitates from a hydrothermal plume andto determine whether the composition of the plume-de-

Leinen, M., Rea, D. K., et al., Init. Repts. DSDP, 92: Washington (U.S. Govt. Print-ing Office).

2 Address: College of Oceanography, Oregon State University, Corvallis, OR 97331.

rived material was different during hydrothermal activi-ty in the past.

This particular chapter is limited to an examinationof the composition of the plume-derived precipitates (aswell as other sediment components) and the deposition-al processes that could change the composition of theplume-derived material.

LOCATION AND SEDIMENTATION AT THEDRILL SITES

Figure 1 shows the locations of the three sites, 597,598, and 599, that were sampled for this study. Hole 597lies farthest west and was drilled into the oldest base-ment (28.6 Ma). The crust was actually formed at theextinct Mendoza Rise, but the rates of crustal formationare similar to those found today at the EPR. Hole 598 islocated on the EPR proper, on 16.0-Ma crust, and Hole599 is located on 7.8-Ma crust. There are 52.7 m of sedi-ment at Hole 597, 52.4 m at Hole 598, and 40.8 m atSite 599, as summarized in the sedimentation rate curvesfor the three sites (Fig. 2). In the basal section of eachhole, sedimentation rates range from 5 to 15 m/m.y.,but upcore the rates decrease to 0.5 m/m.y. or less. Thedecline in sedimentation rate is due primarily to the in-creasing depth of each site and the increased dissolutionof calcite (Rea and Leinen, this volume). The site surveyfor 597 and a limited survey for 598 show the area aroundeach site to have low relief and a uniform sediment cov-er. There is little likelihood that sediment redepositionhas occurred at either site. Site 599, on the other hand,is located in a small valley at the base of a slope; thepresence of turbidites indicates that some of the sectionis redeposited upslope sediment (see Site 599 chapter,this volume).

The sediments themselves are similar at all three sites.They are primarily mixtures of coccolith calcite, clay,and red brown to yellow brown semiopaque oxides (RSO).The RSO fraction is similar to that found during DSDPLeg 34 in the sediments of the Bauer Basin (Yeats, Hart,et al., 1976). The Leg 92 sediments contain no discern-ible opaline material in smear slides, and no siliceousmicro fossils could be sieved from core-catcher samples.

355

M. W. LYLE

15°N

15'

30°S

o

150° 135° 120 105° 75°W

Figure 1. Location of Sites 597, 598, and 599 with respect to the major features of the southeast Pa-cific Ocean. Inverted triangle denotes re-entry.

60 L

Figure 2. Sedimentation rate curves for Sites 597, 598, and 599 basedupon Knüttel (this volume) and Romine (this volume). All threesites have the fastest sedimentation rates ( 10 mm/1000 yr.) whennear the EPR crest; the sedimentation rates slow as the sites dropthrough the lysocline and calcite compensation depth.

Foraminifers are present but generally compose less than5% of the total sediment.

SAMPLING AND ANALYTICAL METHODS

I studied Hole 598 in the greatest detail because it had the mostcomplete, least complicated sedimentary record of the three sites. An

entire 9.5-m section was lost during the coring of Hole 597 because ofa core-catcher failure, so about 20% of the total sedimentary sectionwas missing at the time of sampling. Subsequent efforts have correlat-ed Holes 597 and 597A, so it will be possible to study this site in moredetail in the future. The sedimentary record of Hole 599 is compli-cated by the local redeposition of sediments from the surrounding ter-rain. Several turbidites were found during core description, and re-worked microfossils are abundant in a 25-m section of the core. In or-der to obtain a general record of the sedimentation at Holes 597 and599, I analyzed a small set of samples (taken at intervals of approxi-mately 1 m) from each of these holes. Hole 598, in contrast, was sam-pled at approximately 10-cm intervals for the entire length of the hole.

All sediment samples were freeze dried, ground in an agate mortarto disaggregate them, and pressed into pellets for X-ray fluorescenceanalysis. They were then analyzed on a Phillips PW1600 X-ray fluo-rescence spectrometer for Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Ba, S,and Cl. Machine drift and power fluctuations were corrected for byanalyzing a monitor standard (Canadian CCRMP standard syenite,SY-3) between each sample analysis. Raw counts were converted to ele-mental concentrations through the use of a fundamental parametersprogram and by further linear corrections derived from calibrationwith pressed pellets of over 100 N.B.S., U.S.G.S., Canadian, French,British, and South African standard geological materials, includingsets of N.B.S. standards mixed with reagent-grade CaCO3 to approxi-mate calcite-rich sediments. The sedimentary compositions were thencorrected for mass dilution by sea salt by assuming that all chlorine inthe samples was derived from sea salt and by normalizing composi-tions to a salt-free mass. Further corrections for sea-salt additions inNa, Mg, K, Ca, and S were made by assuming that salt contains thesame elemental ratios to chlorine as are found in average seawater andsubtracting the salt component of these elements from the uncorrectedconcentrations. Calcium carbonate was also estimated by using thenormative approach given in Dymond et al. (1976), which is basedupon Ca abundance. The compositional information is presented inTable 1.

I checked the precision of our analyses by analyzing an in-housesediment standard with each sample set. For 330 analyses bracketingthe time when the Leg 92 samples were run, the precision (lσ) was8.0% for Na, 3.1% for Mg, 3.6% for Al, 3.3% for Si, 3.5% for P,9.3% for Cl, 2.7% for K, 2.6% for Ca, 2.3% for Ti, 2.7% for Mn,2.3% for Fe, 2.7% for Ba, and 16.1% for S. I was also able to checkthe accuracy of our Al, Si, Ca, Mn, Fe, and Ba analyses for a high-carbonate, transition metal-rich matrix typical of EPR sediments bycomparing the results of analyzing 12 EPR sediments by our X-rayfluorescence (XRF) procedure with the results of Dymond's (1981) anal-ysis by atomic absorption (AA) spectrophotometry. There is no signif-

356

MAJOR ELEMENT COMPOSITION, LEG 92 SEDIMENTS

Table 1. Bulk elemental composition of Site 597, 598, and 599 sediments (wt.%).

Core-Section(level in cm)

Site 597

1-1, 131-1, 531-1, 1011-2, 131-2, 721-3, 131-3, 932-1, 232-1, 732-1, 1332-2, 732-2, 1332-3, 932-4, 1232-5, 732-6, 1432-7, 33-3, 33-3, 733-4, 1033-5, 933-6, 634-1, 834-2, 734-3, 634-4, 734-5, 934-6, 536-1, 836-2,736-3, 1026-4, 706-5, 676-5, 1296-6, 83

Site 598

1-1, 91-1, 191-1-1-1-1-

[-

, 29, 39,49, 59,69,79, 89,99, 109, 119

I, 1291, 139

-2, 91-2, 181-2, 301-2, 391-2, 491-2, 591-2, 691-2, 1021-2, 1091-2, 1191-2, 1291-2, 1391-2, 1491-3, 91-3, 191-3, 291-3, 39L-3, 491-3, 59L-3, 69-3,79

1-3, 891-3, 99

Sub-bottomdepth (m)

0.130.531.011.632.233.133.934.835.535.936.837.438.53

10.3311.3313.5313.6317.2317.9319.7321.1322.3324.6326.0327.4329.0330.7331.8343.8345.2347.0348.2049.6350.3051.33

0.090.190.290.390.490.590.690.790.890.991.091.191.291.391.591.681.801.891.992.092.192.532.592.692.792.892.993.093.193.293.393.493.593.693.793.890.99

Na

1.1371.8641.8960.1570.1300.1390.3570.1220.1620.1170.3010.1850.1840.1620.1010.0800.0390.1060.1210.1650.1320.0840.1440.1640.3250.2090.1890.1900.3141.3350.3621.1370.3610.4420.545

0.2430.1200.1120.2960.3300.3000.7390.5770.6960.2900.1850.1850.2490.1890.1420.0900.1300.1610.1420.2410.4270.6450.7380.3560.3300.1340.0810.026

-0.0020.1000.1120.2130.2250.1450.1420.1260.022

Mg

1.4421.8461.9820.7040.6190.6800.5930.6310.6420.4810.9100.5040.4980.4230.4430.3040.3070.3990.3710.3990.3420.4130.4200.4520.5130.5480.4770.5130.6700.8410.5290.8140.5910.8531.076

0.4440.5390.5640.7290.9170.8951.1061.0380.9110.8130.6820.6020.5330.3910.5160.4520.5340.5660.6010.8301.1921.2091.0571.0990.9270.5950.4470.3750.3710.4370.5180.7280.7110.7200.5780.4840.356

Al

4.0014.3173.3030.6140.4990.5410.4630.4810.4730.2880.6050.2430.2200.1720.2230.1740.1560.2350.1990.2110.1710.1770.1780.2120.2070.2430.1850.2270.3640.4050.5120.6280.3830.3500.685

0.3930.6430.6681.1151.4601.4622.1171.8091.5651.2530.9810.8250.6380.3930.6100.4830.6390.6550.7401.1231.7541.8741.8731.5161.1530.6760.4400.3180.2930.3500.4780.7860.7810.8050.5460.3960.248

Si

11.6713.059.461.731.421.561.421.401.430.931.950.910.830.670.820.610.560.800.730.760.630.710.750.890.881.010.820.94

.24

.39

.69,.02.28.16

2.23

1.161.851.933.144.094.135.764.954.253.432.722.31

.78

.16

.70

.37L.76.75.99

2.964.524.874.814.003.021.851.250.940.881.011.392.112.092.181.511.190.77

P

0.9321.2781.0790.1970.1200.1350.1250.1220.1270.0740.1740.0740.0680.0490.0540.0300.0250.0390.0350.0440.0300.0380.0410.0530.0560.0630.0580.0560.1240.1820.1180.1320.0920.1500.183

0.0810.1400.1460.2620.3500.3530.5080.4300.3670.3020.2400.2080.1480.0920.1610.1330.1750.1740.2120.3370.5420.5840.5520.5450.3900.2360.1530.1040.0990.1130.1480.2540.2500.2760.1770.1250.85

K

1.4111.5860.9860.1360.1210.1140.1040.1050.0950.0630.1140.0540.0480.0430.0530.0580.0610.0670.0640.0600.0550.0610.0600.0730.0630.0770.0630.0680.1110.0990.2130.2170.1410.0950.202

0.0820.1370.1570.2710.3450.3430.4750.3970.3390.2840.2270.1940.1510.1050.1530.1200.1620.1510.1710.2560.3840.4550.4210.3430.2570.1680.1190.0840.0790.0900.1150.1760.1720.1820.1240.0960.063

Ca

10.53.42.8

28.830.729.328.630.029.732.724.232.133.634.634.237.237.334.835.435.535.535.634.433.833.032.734.433.229.926.832.828.433.129.927.7

35.032.932.829.425.625.721.924.225.328.230.331.233.034.933.034.232.832.732.427.020.419.620.221.726.031.133.635.035.134.833.630.030.029.232.534.635.3

Ti

0.3400.2680.1900.0520.0470.0460.0460.0440.0470.0340.0500.0350.0310.0270.0310.0310.0280.0330.0330.0320.0330.0310.0300.0350.0380.0380.0310.0340.0550.0530.1140.1280.0800.0540.123

0.0560.0840.0870.1300.1580.1610.1970.1910.1650.1410.1150.0980.0710.0530.0740.0640.0780.0710.0830.1120.1530.1520.1380.1270.1000.0730.0520.0430.0420.0450.0540.0720.0700.0760.0560.0460.036

Mn

2.993.523.491.311.131.401.491.311.411.022.521.321.200.880.740.300.240.590.550.640.470.751.151.491.691.841.491.552.673.701.842.901.712.772.88

0.631.051.091.742.112.062.472.302.001.731.421.230.910.610.950.781.000.981.171.672.352.402.192.171.761.150.810.610.580.650.871.301.301.380.970.730.51

Fe

10.6114.4018.249.277.499.899.779.089.506.24

13.976.855.734.305.071.991.593.463.413.412.243.253.994.815.296.384.935.747.57

10.114.458.854.628.308.84

2.143.854.056.758.398.21

10.239.538.727.756.425.694.102.764.803.945.135.016.309.42

13.2214.3113.3613.3010.596.984.833.593.423.765.137.787.868.685.984.583.09

Ba

0.2150.1720.1770.0720.0740.0780.0820.0750.0790.0710.0850.0720.0780.0620.0650.0570.0550.0580.0570.0560.0510.0600.0650.0660.0640.0700.0690.0710.0640.0730.0590.0730.0580.0680.081

0.1290.1690.1740.2200.2540.2440.2910.2570.1900.1730.1590.1630.1500.1230.1250.1080.1030.0990.1080.1150.1350.1480.1460.1560.1390.1390.1310.1130.0990.1020.1140.1280.1320.1390.1310.1240.115

S

0.1210.1000.0900.0420.0380.0430.0300.0380.0390.0320.0490.0290.0340.0310.0330.0250.0220.0250.0190.0290.0240.0310.0310.0290.0330.0300.0290.0320.0370.0260.0360.0220.0280.0320.037

0.0740.0970.0970.1130.1410.1370.1360.1390.1010.1080.0920.0840.0420.0620.0760.0600.0650.0390.0750.0910.1180.1190.1120.1260.0600.0790.0640.0380.0380.0320.0430.0510.0480.0820.0440.0440.034

357

M. W. LYLE

Table 1 (continued).


Site 598 (Cont.)

1-3, 1091-3, 1191-3, 1291-3, 1391-4, 91-4, 191-4, 291-4, 391-4,491-4, 591-4, 691-4, 891-4,991-4, 1091-4, 1191-4, 1291-4, 1391-4, 1492-1, 72-1, 192-1, 392-1, 492-1, 692-1, 792-1, 892-1, 992-1, 1092-1, 1192-1, 1292-1, 1392-1, 1492-2,92-2, 192-2, 292-2, 392-2, 492-2, 592-2, 692-2, 792-2, 892-2, 992-2, 1092-2, 1192-2, 1292-2, 1392-3,92-3, 192-3, 292-3, 392-3, 492-3, 692-3, 792-3, 892-3, 992-3, 1092-3, 1192-3, 1292-3, 1392-3, 1492-4, 92-4, 192-4, 392-4, 392-4, 592-4, 692-4, 792-4, 892-4, 992-4, 1092-4, 1192-4, 1292-4, 1392-5,92-5, 192-5, 29

Sub-bottomdepth (m)

4.094.194.294.394.594.694.794.894.995.095.195.395.495.595.695.795.895.996.276.396.596.696.896.997.097.197.297.397.497.597.697.797.897.998.098.198.298.398.498.598.698.798.898.999.099.299.399.499.599.699.899.99

10.0910.1910.2910.3910.4910.5910.6910.7910.8910.9911.0911.2911.3911.4911.5911.6911.7911.8911.9912.0912.2912.3912.49

Na

0.0600.1060.1210.0090.2870.0180.0150.1480.3860.1620.0890.0000.1560.0120.0430.1480.0670.2130.141

-0.0230.1530.2370.1580.0240.0300.0610.110

-0.026-0.023-0.040

0.148-0.028

0.1090.2290.0180.1670.1520.1700.2420.1490.1810.2040.2860.1660.1660.1490.1910.1280.1270.1130.0670.1500.2580.1750.2000.2360.0560.2080.0920.2210.0930.1420.2130.2190.0650.2210.2160.0390.2350.2280.2200.2330.2220.0870.099

Mg

0.3570.4080.3640.3600.3280.4090.4630.6610.8720.6710.4420.3190.3480.3270.3510.4040.4370.4540.3270.3240.3580.3190.3260.3550.3410.3600.3450.3390.3400.3430.3570.3630.3590.3400.3730.3500.3650.3650.3920.3560.3600.3740.3830.3630.3690.3680.3740.3700.3830.3820.4300.4000.3630.3650.3850.3940.4200.4300.4530.4240.4940.4800.4010.3920.4860.4350.4610.4590.4800.4750.4470.5110.4940.4910.489

Al

0.2380.3090.2540.1980.1640.2610.3360.6040.8720.5680.2830.1630.1740.1570.1550.2440.3190.3490.1180.1120.1250.1200.1220.1300.1270.1260.1290.1200.1250.1220.1430.1490.1410.1530.1670.1490.1660.1660.1630.1550.1610.1620.1710.1660.1620.1600.1720.1580.1590.1670.2010.1780.1530.1610.1730.1900.1880.2050.2140.2080.2460.2280.1940.1960.2370.2110.2280.2260.2270.2250.2120.2570.2500.2380.247

Si

0.740.920.780.630.540.780.971.662.411.550.850.570.590.550.540.780.991.070.540.520.580.540.540.550.560.560.560.540.560.540.580.580.570.600.620.580.630.620.610.590.600.610.630.610.600.600.630.610.610.620.740.690.600.620.680.730.730.770.810.790.920.840.740.780.920.800.870.880.880.870.840.970.970.920.94

P

0.0850.1160.0950.0700.0600.0890.1210.2580.3470.2220.1020.0540.0550.0500.0490.0780.1040.1060.0340.0340.0360.0370.0350.0380.0370.0360.0360.0350.0350.0350.0440.0450.0440.0480.0520.0470.0540.0510.0500.0490.0500.0500.0540.0510.0500.0500.0530.0490.0490.0510.0630.0590.0490.0520.0570.0630.0620.0690.0730.0710.0830.0720.0670.0720.0830.0700.0770.0790.0760.0710.0710.0840.0830.0800.082

K

0.0580.0710.0600.0500.0370.0570.0700.1180.1460.1040.0640.0450.0440.0430.0460.0640.0810.0890.0400.0420.0430.0380.0400.0450.0430.0460.0420.0430.0430.0420.0390.0410.0420.0400.0410.0380.0390.0400.0370.0400.0380.0380.0390.0420.0380.0400.0400.0390.0400.0440.0460.0400.0370.0390.0370.0390.0430.0430.0440.0440.0470.0410.0410.0430.0480.0410.0440.0470.0420.0440.0460.0470.0490.0480.048

Ca

35.434.635.236.236.835.034.430.026.730.834.936.336.536.537.035.834.234.236.736.237.436.637.037.037.037.537.136.436.736.936.335.635.836.336.035.735.535.436.135.435.735.635.835.135.935.835.435.835.435.234.734.935.935.235.134.634.934.134.133.733.234.234.533.433.033.733.733.233.133.933.932.432.933.132.4

Ti

0.0350.0410.0350.0310.0280.0350.0400.0570.0680.0520.0350.0270.0270.0270.0270.0320.0350.0350.0240.0230.0240.0240.0240.0240.0240.0240.0240.0230.0230.0240.0250.0250.0250.0250.0270.0250.0260.0260.0260.0260.0250.0250.0260.0260.0260.0260.0260.0260.0250.0260.0290.0270.0240.0260.0270.0290.0280.0290.0300.0290.0310.0300.0290.0300.0320.0300.0310.0330.0310.0310.0310.0340.0330.0320.033

Mn

0.470.610.500.400.320.520.691.251.651.150.600.360.380.340.320.510.660.660.230.240.240.250.240.260.240.250.250.250.250.250.330.370.360.380.440.390.420.440.400.420.430.420.430.440.430.430.450.430.400.430.620.630.390.490.600.740.680.770.830.790.930.790.690.830.960.800.890.960.920.890.901.021.010.981.01

Fe

2.913.883.103.301.953.354.598.68

11.067.734.032.272.392.182.013.394.564.55

.68

.69

.74

.75

.74

.89

.79

.82

.84

.81

.83

.792.432.772.692.803.372.953.233.342.993.203.293.213.323.373.283.293.403.283.023.294.444.222.893.544.084.824.544.995.385.256.145.204.715.576.455.465.986.576.245.765.987.016.796.546.84

Ba

0.1060.1140.1110.1070.0920.1020.0990.1110.1290.1200.1130.1050.1050.1060.1010.1210.1220.1370.0970.0960.0980.0980.0970.0980.0970.0980.0980.0980.0970.1000.1010.0990.0980.0960.1010.0970.1000.0980.0990.0960.0980.0980.0980.0970.0980.0970.1020.0980.0990.1040.1010.1000.1000.0980.0990.1000.0980.1040.1030.1030.1060.1010.1020.0990.0970.0930.0990.0910.0930.0910.0890.0970.0970.0930.093

S

0.0300.0540.0300.0310.0140.0340.0370.0740.0600.0450.0330.0300.0230.0290.0280.0290.0360.0290.0170.0260.0260.0200.0160.0250.0250.0260.0210.0250.0240.0260.0160.0260.0240.0350.0230.0200.0200.0220.0170.0200.0220.0200.0160.0230.0190.0230.0230.0210.0220.0280.0280.0260.0150.0250.0190.0260.0300.0260.0350.0270.0310.0300.0250.0440.0340.0270.0270.0520.0220.0300.0310.0230.0340.0300.028

358




Site 598 (Cont.)

2-5, 392-5, 492-5, 592-5, 692-5, 892-5, 1092-5, 1302-5, 1392-5, 1492-6, 92-6, 192-6, 292-6, 392-6, 492-6, 592-6, 692-6, 792-6, 892-6,992-6, 1192-6, 1392-6, 1493-3-3-3-3-3-3-3-3-3-3-3-3-3-3-

, 9t, 19I, 29I, 391,49,59

1,691,79, 89, 99, 109, 119, 129, 139, 149

3-2,93-2, 193-2, 313-2, 393-2, 493-2, 593-2, 693-2, 793-2, 893-2, 993-2, 1093-2, 1193-2, 1293-3,93-3, 193-3, 293-3, 393-3, 493-3, 593-3, 693-3, 793-3, 893-3, 993-3, 1093-3, 1193-3, 1293-3, 1393-3, 1493-4,93-4, 193-4, 293-4, 393-4, 493-4, 593-4, 693-4, 793-4, 893-4, 99

Sub-bottomdepth (m)

12.5912.6912.7912.8913.0913.2913.5013.5913.6913.7913.8913.9914.0914.1914.2914.3914.4914.5914.6914.8915.0915.1915.8915.9916.0916.1916.2916.3916.4916.5916.6916.7916.8916.9917.0917.1917.2917.3917.4917.6117.6917.7917.8917.9918.0918.1918.2918.3918.4918.5918.8918.9919.0919.1919.2919.3919.4919.5919.6919.7919.8919.9920.0920.1920.2920.3920.4920.5920.6920.7920.8920.9921.0921.1921.29

Na

0.1260.1180.1030.1350.0530.2230.0830.2130.0750.1010.1080.0900.0990.1030.0390.2290.0720.0860.0430.2400.2430.2280.2320.2330.1850.2720.1530.1540.1530.0740.2550.0860.1790.1370.0980.2300.1410.0860.1200.2990.2710.0570.1480.1100.0620.0790.2210.2530.2200.2260.2680.1450.0240.0880.1520.1000.1880.1690.1590.2360.2590.0670.1740.0780.2680.0590.1890.0850.0860.1300.1610.1450.0450.1800.105

Mg

0.5780.5670.5920.4800.5270.5810.4970.5360.5570.5260.4840.5230.5030.5320.5150.5160.4930.5390.5170.5200.5320.5520.6920.5720.6930.6660.7020.7020.6770.5170.6880.5970.4750.5600.5560.5090.5270.4700.5090.5240.5500.4870.4890.5090.4830.4740.4470.4690.5100.4310.5050.4970.4840.4900.4980.5200.5210.5240.4550.4820.4660.5010.4890.4270.4500.4670.4750.4240.4910.4520.4850.4320.4330.4170.474

Al

0.3000.2930.3020.2510.2770.3130.2410.2500.2540.2440.2300.2400.2340.2400.2380.2480.2390.2980.2680.2560.2640.2630.3450.2860.3450.3370.3420.3440.3150.2140.3320.2920.1860.2430.1930.1880.1850.1700.1850.2010.2030.1710.1770.2050.1930.1960.1630.1820.1980.1480.1480.1460.1970.13301.360.1440.1250.1160.1120.1180.1220.1160.1080.0950.1120.0950.1100.0860.0950.0970.1080.0910.0990.1000.105

Si

1.131.111.130.981.071.150.940.960.970.940.910.930.910.930.920.960.931.111.010.980.990.991.411.241.411.421.411.411.320.971.391.240.871.020.890.860.870.810.840.890.910.820.820.870.850.860.780.820.880.720.760.740.880.720.670.780.710.660.640.650.670.690.650.570.620.600.650.540.590.590.670.570.610.630.62

P

0.1040.1010.1030.0910.0970.1020.0890.0860.0890.0840.0870.0850.0800.0820.0800.0850.0830.1020.0920.0880.0860.0870.1300.1170.1320.1340.1330.1310.1260.0930.1270.1190.0860.0950.0870.0820.0830.0800.0820.0830.0850.0810.0800.0820.0820.0820.0750.0780.0810.0700.0720.0710.0830.0750.0610.0770.0710.0670.0640.0640.0650.0740.0670.0570.0630.0640.0650.0540.0590.0580.0660.0580.0630.0620.071

K

0.0560.0540.0560.0530.0520.0550.0480.0450.0520.0470.0430.0470.0470.0460.0480.0460.0490.0580.0550.0500.0490.0500.0640.0590.0660.0650.0680.0660.0630.0480.0630.0600.0440.0510.0500.0440.0450.0430.0430.0420.0430.0430.0430.0440.0500.0460.0350.0420.0420.0370.0380.0380.0450.0390.0390.0440.0390.0360.0360.0340.0380.0360.0390.0350.0310.0390.0350.0330.0410.0350.0360.0350.0380.0360.038

Ca

31.231.631.931.931.231.432.332.433.132.432.232.832.032.833.132.832.631.332.032.332.632.828.928.528.327.628.628.429.531.828.929.632.331.932.732.933.033.033.132.832.933.233.133.432.932.732.333.231.933.833.132.532.433.334.332.433.133.433.233.633.233.034.034.234.034.133.134.134.634.533.434.533.833.434.1

Ti

0.0360.0360.0360.0330.0340.0350.0320.0320.0320.0310.0320.0310.0310.0310.0310.0320.0330.0370.0350.0330.0330.0330.0410.0390.0410.0430.0420.0420.0410.0350.0410.0390.0310.0340.0300.0300.0300.0300.0300.0300.0300.0300.0290.0310.0310.0300.0280.0300.0310.0280.0290.0280.0320.0270.0260.0270.0250.0260.0250.0260.0260.0260.0240.0230.0250.0240.0250.0230.0250.0250.0240.0240.0240.0250.026

Mn

1.181.181.191.201.151.211.021.041.071.031.041.021.011.021.021.041.041.281.161.081.081.071.741.711.771.821.791.781.721.291.651.571.271.281.251.171.221.151.151.171.211.171.151.121.121.111.161.111.161.151.451.321.231.421.211.631.441.421.261.321.451.521.561.321.311.411.461.251.321.261.391,421.401.391.42

Fe

8.228.098.157.757.868.037.067.027.076.796.876.816.766.756.746.776.697.987.466.996.876.72

10.4510.2410.6010.9810.7010.6310.157.61

10.299.587.177.706.876.426.676.276.316.336.386.306.256.356.466.506.276.126.255.905.695.856.835.864.956.535.855.505.354.875.156.015.714.634.524.844.944.444.614.495.714.464.935.114.68

Ba

0.1060.1030.0990.0890.0930.0960.0910.0880.0880.0860.0840.0840.0860.0860.0860.0880.0840.0890.0870.0850.0840.0850.1030.0970.1020.1010.1010.1040.1000.0910.1030.0970.0910.0920.0930.0930.0930.0920.0920.0950.0950.0950.0910.0930.0950.0950.0870.0920.0900.0800.0750.0740.0880.0770.0740.0750.0710.0640.0690.0680.0680.0720.0670.0690.0650.0670.0690.0620.0660.0690.0660.0670.0690.0630.068

S

0.0340.0320.0330.0510.0600.0360.0270.0240.0320.0270.0480.0280.0280.0270.0300.0300.0490.0570.0540.0360.0280.0310.0330.0520.0340.0350.0370.0330.0340.0550.0360.0610.0470.0280.0320.0320.0280.0470.0270.0310.0310.0540.0260.0250.0510.0480.0380.0290.0290.0410.0260.0240.0520.0480.0240.0500.0240.0230.0400.0250.0260.0490.0230.0230.0200.0480.0260.0400.0300.0220.0230.0210.0440.0260.025

359

M. W. LYLE



Site 598 (Cont.)

3-4, 1093-4, 1193-4, 1293-4, 1393-5, 13-5, 193-5, 293-5, 393-5, 493-5, 593-5, 693-5, 793-5, 893-5, 993-5, 1093-5, 1193-5, 1293-5, 1393-5, 1493-6,93-6, 193-6, 393-6, 493-6, 593-6, 693-6, 893-6, 993-6, 1093-6, 1194-1,94-1, 494-1, 594-1, 694-1, 894-1, 994-1, 1104-1, 1194-1, 1394-1, 1494-2,94-2, 194-2, 294-2, 394-2, 494-2, 594-2, 694-2, 994-2, 1094-2, 1194-2, 1294-2, 1394-3,94-3, 304-3, 394-3, 494-3,694-3, 894-3,994-3, 1094-3, 1194-3, 1294-3, 1394-3, 1494-4,94-4, 304-4, 394-4,494-4, 594-4, 694-4,794-4, 894-4, 1194-4, 1304-4, 1394-5,9

Sub-bottomdepth (m)

21.3921.4921.5921.6921.8121.9922.0922.1922.2922.3922.4922.5922.6922.7922.8922.9923.0923.1923.2923.3923.4923.6923.7923.8923.9924.1924.2924.3924.4925.5925.8925.9926.0926.2926.3926.5026.5926.7926.8926.9927.0927.1927.2927.3927.4927.5927.8927.9928.0928.1928.2928.4928.7028.7928.8929.0929.2929.3929.4929.5929.6929.7929.8929.9930.2030.2930.3930.4930.5930.6930.7931.0931.2031.2931.49

Na

0.0710.0650.0350.2350.1430.0650.0890.2440.2460.2090.1650.1260.1210.2400.1100.2150.1780.1590.2940.0770.1760.2140.1830.1250.2180.1490.2090.0960.1650.1910.1080.1560.1960.3370.3020.1290.2250.2600.2690.0930.1570.1710.1720.1320.1390.1360.1380.1570.1130.2290.2050.1310.0660.1150.0420.1730.0840.1040.1630.1700.2680.1200.0520.1770.0490.4180.2040.0890.1700.1560.1530.1440.0720.1470.074

Mg

0.4090.4400.4040.3810.4220.4160.4610.4880.5360.5390.5930.5100.5700.5170.5390.5590.5720.5050.4430.4840.4820.5320.4830.4770.5820.5520.5960.5620.6240.5570.5720.6380.7490.8550.7460.5930.6180.7540.7470.5260.5510.5490.5640.5550.5230.4250.4990.5510.5280.5650.6010.5190.5060.5200.5320.5460.5630.6310.5100.6470.5770.4710.5260.4930.4940.4540.4590.4890.5260.5300.4640.5610.5230.4630.439

Al

0.0920.0930.0890.0920.0930.0860.0930.1040.1240.1130.1170.1200.1360.1330.1330.1300.1190.1080.0960.0980.1020.1070.0990.1040.1220.1320.1580.1320.1330.1310.1320.1610.2060.2300.1760.1400.1410.1680.1820.1160.1290.1300.1360.1330.1400.1080.1160.1110.1190.1280.1380.1250.1270.1220.1210.1190.1420.1680.1120.1750.1640.1350.1460.1250.1330.1230.1170.1110.1070.1060.1010.1400.1140.0880.077

Si

0.580.580.550.550.570.560.650.690.760.770.750.780.860.770.820.800.770.690.630.670.670.690.630.680.790.830.950.900.920.900.921.061.341.381.130.920.911.101.110.720.800.800.850.800.810.640.740.700.760.790.890.850.820.840.830.820.901.030.681.020.930.770.840.770.730.730.710.690.690.690.640.790.730.580.53

P

0.0650.0590.0550.0580.0780.0580.0650.0740.0850.0890.0840.0890.0970.0950.1020.1040.0880.0800.0710.0730.0750.0770.0720.0740.0810.0880.1110.1100.1030.1000.1050.1240.1510.1760.1440.1200.1140.1160.1050.0870.1040.0940.1140.1090.0930.0990.1340.1260.0890.0870.0890.0790.0840.0880.0990.1530.1170.1160.0770.1010.0960.0850.0920.0780.0810.0970.0970.0910.0680.0670.0850.0790.0820.0680.062

K

0.0340.0380.0360.0300.0350.0340.0380.0400.0410.0410.0450.0440.0460.0420.0470.0460.0450.0420.0360.0370.0390.0390.0380.0400.0460.0530.0490.0540.0520.0540.0560.0580.0740.0790.0660.0520.0530.0650.0610.0500.0500.0510.0530.0520.0480.0400.0440.0410.0500.0460.0520.0530.0510.0490.0500.0460.0580.0630.0420.0650.0540.0480.0500.0450.0430.0390.0390.0430.0420.0420.0390.0430.0430.0400.032

Ca

33.934.333.534.234.435.233.232.732.531.533.031.931.232.331.732.032.332.933.132.932.933.133.833.031.931.430.930.530.129.729.828.726.126.128.230.030.528.329.132.631.731.931.632.431.733.032.733.732.632.230.830.230.930.931.031.230.829.133.330.731.732.531.631.732.133.132.532.533.433.432.732.532.633.334.8

Ti

0.0240.0240.0230.0240.0240.0240.0230.0240.0270.026 :0.0250.026 :0.028 ;0.0280.030 :0.028 :0.025 :0.0250.0240.0240.0240.0230.0240.0250.025 ;0.027 ;0.029 ;

Mn

1.341.38.24.24.39.32

1.62.78.85

2.07.82

'.04>.32.90

>.23J.141.01.98.77.86.87.83.78.92

>.2O'.44>.50

0.027 2.710.026 2.570.026 2.880.027 2.950.030 :0.032 i

.34U 2

0.036 4.300.030 3.610.029 :0.029 :0.029 :0.031 2

.01'.98.58.18

0.026 2.200.027 2.490.028 2.430.027 :..570.026 2.260.029 2.480.027 .870.027 2.080.025 1 .690.028 2.230.027 :..190.027 2.640.027 : .740.027 2.490.028 2.860.027 2.670.026 2.630.029 2.770.031 3.270.026 1 .870.031 2.910.030 2.480.028 2.050.029 2.250.027 2.240.030 2.010.028 1 .950.027 2.030.027 10.025 10.026 10.026 10.029 10.026 10.023 10.023 1

.94

.87

.87

.87

.98

.97

.79

.39

Fe

4.724.604.344.324.574.475.635.886.187.066.006.777.636.136.986.776.675.755.305.835.915.615.215.576.657.197.308.078.378.077.869.03

11.3310.909.387.857.589.319.015.796.406.336.776.166.545.006.065.206.126.197.437.507.157.627.507.307.338.515.317.936.815.996.846.396.125.835.885.665.575.575.205.926.234.924.28

Ba

0.0710.0650.0640.0640.0670.0660.0660.0680.0750.0740.0700.0720.0760.0730.0740.0740.0690.0690.0650.0670.0660.0660.0670.0680.0690.0730.0740.0760.0720.0740.0740.0790.0860.0900.0800.0790.0770.0790.0750.0680.0710.0710.0740.0710.0730.0670.0700.0650.0700.0740.0750.0780.0730.0770.0740.0710.0760.0780.0660.0750.0770.0710.0710.0710.0690.0680.0680.0660.0650.0650.0610.0650.0670.0610.061

S

0.0460.0460.0440.0210.0220.0220.0460.0280.0290.0490.0290.0490.0510.0290.0540.0280.0280.0260.0230.0510.0230.0250.0210.0470.0290.0310.0340.0570.0300.0490.0610.0650.0740.0390.0340.0620.0300.0630.0340.0320.0300.0290.0560.0320.0280.0260.0280.0370.0550.0510.0550.0490.0560.0510.0570.0510.0630.0650.0280.0360.0260.0520.0550.0470.0530.0450.0440.0500.0260.0260.0460.0440.0510.0430.044

360




Site 598 (Cont.)

4-5, 194-5, 294-5, 394-5, 494-5, 594-5, 694-5, 814-5, 894-5, 994-5, 1104-5, 1184-6, 94-6, 204-6, 305-5-5-5-5-5-5-5-5-5-5-5-5-5-

, 9I, 19, 29,39, 49, 59,69,80, 89

1,99, 109, 119, 129, 142

5-2,95-2, 195-2, 315-2, 395-2, 495-2, 595-2, 715-2, 795-2, 895-2,995-2, 1095-2, 1195-2, 1295-2, 1395-3,95-3, 195-3, 295-3, 395-3, 495-3, 595-3, 795-3,995-3, 1095-3, 1195-3, 1295-3, 1395-3, 1495-4,95-4, 195-4, 295-4, 395-4, 495-4, 595-4, 695-4, 795-4, 895-4, 995-4, 1395-5, 95-5, 295-5, 395-5, 495-5, 595-5, 695-5, 895-5, 995-5, 109

Sub-bottomdepth (m)

31.5931.6931.7931.8931.9932.0932.2032.2932.3932.4932.5832.9933.1033.2035.0935.1935.2935.3935.4935.5935.6935.8035.8935.9936.0936.1936.3036.4236.5936.6936.8136.8936.9937.0937.2137.2937.3937.4937.5937.6937.7937.8938.0938.1938.2938.3938.4938.5938.7938.9939.0939.1939.2939.3939.4939.5939.6939.7939.8939.9940.0940.1940.2940.3940.4940.8941.0941.2941.3941.4941.5941.6941.8941.9942.09

Na

0.1420.1480.1770.1540.2380.2030.2690.1800.1160.2200.1670.2340.2720.2860.2560.1930.2110.1810.1900.2430.2160.2310.2530.2250.2330.2620.1320.1860.2930.3470.2240.2490.4460.2230.4140.2720.3310.3200.2750.3140.2890.3170.2450.2960.2720.1970.3730.2700.2660.2780.3980.2400.3000.2090.4220.1960.2980.3200.3190.3680.3060.2390.2390.1750.3660.3320.2880.3480.3380.4720.3560.4370.3800.3080.286

Mg

0.4860.5460.5100.6400.6890.6240.7700.6220.5440.5850.5860.7900.8170.8340.6340.5670.5880.7120.7520.6740.6750.7030.8340.6790.6590.7860.6620.6400.6930.8220.6960.6600.8050.4370.9230.7760.7750.7870.7130.8270.8410.7100.6820.6640.6020.6130.6680.5820.7150.8080.7970.6220.7030.7110.8100.8460.8000.8300.7600.8040.7590.7230.6700.6470.8580.7640.6990.8190.8020.7650.8070.8910.9120.8710.740

Al Si

0.087 0.570.092 0.620.087 0.600.119 0.860.139 0.900.149 0.900.249 .220.165 0.890.120 0.710.127 0.770.123 0.770.2090.1570.159

.26

.20

.210.111 0.890.098 0.750.105 0.810.1220.1270.127 (0.1500.1540.168

.01

.07).96.05.07.26

0.136 0.990.144 0.980.145 .130.137 0.930.131 0.880.123 0.920.1620.1510.127 (0.148

.24

.05).87.14

0.090 0.610.1590.1530.1460.1610.1510.1720.2010.1620.140

.34

.12

.14

.17

.03

.29

.34

.06

.000.129 0.970.122 0.810.134 (0.159

).89.04

0.123 0.840.2050.2080.1820.1510.1520.1410.1650.2240.2080.1880.1480.1590.1420.149

.25

.37

.30

.03

.08

.05

.24

.50

.31

.29

.10

.19

.16

.040.124 0.940.1450.1760.1550.132 (0.1350.1670.1500.1690.2110.1910.1800.166

.03

.43

.15).97.16.27.18.26.49.46.31.15

P

0.0680.0750.0760.0860.0990.0860.1220.1040.0910.0840.0920.1290.1320.1430.1020.1160.0940.1530.1180.1990.1710.1520.1280.1530.1520.1350.1140.1030.1120.1180.1360.0990.1710.3140.1210.1260.1270.1200.1250.1260.1260.1260.1170.1000.1010.0840.090.950.130.060.030.960.110.210.440.620.500.450.360.700.710.250.470.260.330.730.420.870.500.120.260.740.370.550.77

K

0.0360.0350.0380.0540.0550.0560.0640.0470.0420.0460.0480.0680.0610.0670.0530.0460.0490.0530.0540.0550.0540.0620.0700.0550.0550.0630.0570.0560.0540.0680.0590.0500.0620.0370.0690.0580.0630.0650.0600.0660.0700.0600.0560.0540.0490.0540.0580.0490.0680.0760.0750.0590.0570.0600.0710.0830.0730.0710.0620.0630.0580.0540.0540.0600.0730.0660.0570.0670.0630.0620.0760.0850.0800.0650.065

Ca

34.733.733.830.930.631.629.632.033.232.632.427.427.526.830.031.531.128.928.429.729.229.026.229.129.927.730.031.330.426.229.331.227.533.824.128.427.126.629.126.125.428.429.430.131.530.728.831.928.026.025.629.628.729.526.124.827.726.128.627.227.530.330.129.523.727.930.027.526.927.627.323.924.127.228.6

Ti

0.0230.0230.0230.0240.0250.0260.0360.0290.0250.0260.0250.0320.0270.0260.0230.0230.0230.0260.0230.0260.0260.0270.0260.0260.0260.0240.0250.0250.0240.0250.0270.0250.0240.0240.0250.0260.0250.0270.0270.0250.0280.0270.0250.0240.0250.0260.0270.0240.0310.0290.0280.0270.0270.0270.0270.0310.0310.0300.0250.0270.0250.0290.0250.0260.0270.0280.0260.0300.0280.0270.0280.0300.0280.0280.028

Mn

1.421.771.592.442.732.613.062.291.902.092.073.263.463.662.802.292.463.182.833.053.093.293.763.303.183.522.862.512.853.893.332.713.311.364.383.503.793.813.153.983.953.293.083.162.652.863.132.393.453.904.032.923.132.973.924.483.533.733.053.663.382.742.712.864.303.483.003.754.043.734.024.754.223.473.15

Fe

4.365.124.887.947.886.958.026.355.596.036.16

10.5710.7911.008.196.767.249.44

10.328.519.009.09

11.568.528.16

10.388.137.268.00

11.308.807.06

10.014.96

12.689.59

10.0610.578.77

11.4811.799.058.918.556.707.328.946.819.60

11.0311.238.689.328.99

10.8212.1710.1211.549.65

10.3810.768.278.239.15

12.859.768.22

10.2110.749.95

10.2612.0812.7011.229.28

Ba

0.0600.0630.0630.0700.0740.0750.0820.0760.0690.0700.0670.0870.0840.0830.0710.0670.0700.0740.0740.0760.0800.0890.0850.0810.0800.0850.0800.0790.0790.0880.0870.0740.0770.0660.0850.0820.0830.0840.0860.0860.0880.0820.0770.0800.0730.0810.0820.0780.1050.1010.0960.0910.0840.0880.0970.1060.1010.0840.0790.0800.0780.0770.0810.0850.0970.0850.0820.0850.0960.0850.0930.1010.0890.0860.081

S

0.0230.0230.0250.0340.0350.0300.0350.0300.0270.0290.0310.0380.0320.0380.0320.0320.0300.0320.0330.0420.0400.0390.0400.0400.0440.0390.0340.0330.0350.0390.0370.0330.0350.0430.0360.0340.0360.0320.0370.0380.0410.0380.0360.0370.0320.0320.0320.0320.0400.0440.0470.0360.0480.0410.0510.0560.0440.0450.0390.0380.0400.0380.0380.0390.0480.0610.0380.0410.0350.0450.0460.0440.0450.0420.042

361

M. W. LYLE



Site 598 (Cont.)

5-5, 1195-5, 1295-5, 1395-5, 1495-6, 195-6, 295-6, 415-6, 495-6, 595-6, 69

Site 599

1-1, 1291-2, 291-2, 1291-3, 691-3, 891-3, 1291-4,91-4, 291-4, 391-4, 691-4, 791-4, 891-5, 391-5, 1271-6,92-1, 592-1, 892-2, 492-2, 1292-3, 392-3, 1292-4, 392-4, 1392-5, 792-6, 792-6, 1493-3-3-3-3-3-3-3-3-3-

, 9, 19,29, 39,49, 59, 89,99, 109, 130

3-2, 193-2, 293-2, 493-2, 593-2, 873-2, 1003-2, 1293-2, 1393-3, 93-3, 393-3, 1093-3, 1193-3, 1393-3, 1493-4, 193-4, 893-4, 1293-5, 493-6, 693-6, 1494-1, 794-2, 694-3, 194-3, 494-4, 804-4, 1194-6, 49

Sub-bottomdepth (m)

42.1942.2942.3942.4942.6942.7942.9142.9943.0943.19

1.291.792.793.693.894.294.594.794.895.195.295.396.397.277.598.498.799.89

10.6911.2912.2912.7913.7914.6916.1916.8916.9917.0917.1917.2917.3918.0918.3918.4918.5918.8019.2919.3919.5919.6919.9720.1020.3920.4920.5920.8921.6921.7921.9922.0922.2922.8923.1924.0025.6926.4927.8929.2930.2930.5932.4034.2935.09

Na

0.4780.4360.2250.2510.2920.2770.2510.2220.2590.210

0.2620.1940.0930.105

-0.0150.0010.2910.040

-0.008-0.002

0.1160.0050.1170.1810.0010.122

-0.0120.3680.2440.3780.2140.1000.1290.1490.2330.3690.0690.0580.0850.1740.3430.1410.1810.1750.2080.2570.1860.2580.3110.1610.2130.2400.2850.2230.3690.0740.1520.1290.1590.1830.0380.1760.0800.3570.5610.2010.3620.3900.0090.2520.3590.4360.667

Mg

0.6711.0390.6710.6010.7790.7460.7320.6120.7940.635

0.3450.5150.3570.2820.2570.2820.3640.2990.3290.3180.3680.3540.3480.3520.3200.4660.2980.6510.6790.5790.4510.4240.4330.4810.5500.7220.4890.3980.4160.5850.6850.4510.5710.5330.6680.6830.5360.6310.6560.5330.7470.6360.7140.6240.6400.3770.4600.4520.5160.4990.3040.4980.4750.7000.7330.5780.7040.7900.4010.6330.7290.8030.827

Al

0.1490.1870.1330.1380.1870.1800.1690.1450.2200.154

0.3230.6180.2140.0930.0750.0730.1480.1010.1100.1000.1420.1190.0880.0850.0590.1070.0600.1160.1240.1050.0890.0910.0940.0980.1060.1110.0700.0580.0620.0860.0990.0860.0840.0700.0800.1020.0700.0840.1170.0740.0880.0910.0930.0790.1170.0930.0920.0850.0990.0850.0590.0890.0660.1080.1130.0670.1300.1290.0620.1320.1130.1400.166

Si

1.001.610.930.971.261.201.120.931.270.92

0.901.590.660.390.390.410.600.530.570.550.620.650.490.500.510.800.611.261.471.180.860.830.891.051.301.841.270.930.991.591.881.021.681.371.841.871.241.731.821.462.081.681.861.561.590.991.321.251.431.280.791.201.271.962.031.581.892.170.991.611.821.931.93

P

0.600.590.850.650.890.360.030.320.150.28

0.0810.1790.0890.0350.0340.0380.0610.0520.0590.0520.0530.0620.0440.0470.0480.0680.0470.2540.2950.1870.0800.0620.0590.1360.2170.2290.1740.0940.0890.1910.2690.0720.3370.3000.2730.3030.3690.4280.3210.2960.2230.4680.2840.2850.3320.0400.0730.0670.0780.0700.0390.1080.1880.4010.3440.2730.3490.1580.0650.2260.2870.4420.318

K

0.0530.0720.0540.0560.0700.0720.0640.0570.0630.054

0.0790.1500.0450.0290.0210.0200.0300.0210.0260.0250.0380.0290.0320.0220.0210.0470.0240.0610.0710.0560.0430.0410.0430.0550.0630.0820.0470.0350.0360.0550.0600.0470.0670.0570.0660.0740.0470.0680.0800.0590.0750.0630.0680.0590.0730.0470.0470.0450.0490.0450.0300.0560.0510.0830.0840.0600.0810.0910.0380.0720.0810.0850.085

Ca

29.722.530.829.928.128.529.431.229.132.5

35.732.234.936.037.036.634.835.835.535.434.835.036.036.135.834.335.028.426.629.733.033.333.431.629.025.029.432.832.627.124.632.427.229.125.325.029.726.527.028.623.326.524.627.227.333.630.931.430.331.434.731.029.624.924.427.424.922.931.627.524.822.923.0

Ti

0.0270.0260.0280.0270.0300.0300.0290.0270.0340.029

0.0370.0560.0280.0210.0220.0230.0250.0240.0250.0250.0250.0250.0210.0220.0220.0230.0210.0240.0250.0220.0210.0210.0210.0220.0240.0240.0220.0210.0210.0240.0260.0210.0260.0250.0240.0250.0240.0250.0250.0240.0240.0250.0260.0250.0270.0210.0230.0220.0220.0210.0210.0210.0210.0220.0230.0210.0250.0240.0210.0260.0240.0260.030

Mn

2.754.552.662.753.203.483.082.452.802.17

0.430.790.470.200.210.310.520.470.520.540.610.740.560.570.651.280.902.943.572.531.551.331.422.012.774.232.671.761.733.394.161.633.573.103.754.042.923.613.643.184.523.724.193.573.370.971.951.822.242.010.912.052.603.844.003.503.904.431.773.083.924.424.37

Fe

8.1714.657.648.259.809.189.057.269.196.45

2.575.663.561.411.542.153.663.243.643.483.634.612.943.093.465.523.998.99

10.6211.445.585.285.666.818.52

11.728.555.856.28

10.2612.316.079.868.23

11.5211.197.72

10.579.938.73

13.0110.1411.899.799.254.807.687.028.307.233.966.967.96

11.4411.8210.5511.4613.106.87

10.2011.6712.6912.78

Ba

0.0730.0900.0790.0800.0850.0910.0770.0750.0790.074

0.1110.1330.0980.0950.0940.0920.0960.1060.0990.0980.1010.1040.0840.0870.0850.0950.0840.0910.1040.1000.0920.0910.0910.0890.0920.0990.0940.0850.0850.1020.0970.0860.1030.0960.1030.1020.0870.0980.1010.0960.1060.0970.1000.0940.0910.0900.1060.0990.1110.0970.0910.0880.0970.1000.0960.0950.0950.1000.0920.0960.0970.1040.098

S

0.0260.0480.0400.0420.0420.0490.0420.0370.0400.038

0.0260.0420.0260.0210.0260.0290.0180.0270.0300.0300.0230.0340.0230.0210.0290.0290.0270.0350.0440.0450.0270.0260.0270.0300.0350.0370.0410.0340.0360.0420.0320.0260.0520.0460.0490.0510.0440.0540.0440.0470.0480.0500.0470.0430.0350.0250.0350.0350.0350.0340.0300.0270.0400.0450.0400.0420.0350.0310.0350.0380.0390.0470.040

362


icant difference in composition for Ca and Al between AA and XRFanalysis. When analyzed by XRF, Si, Mn, and Fe were consistentlyhigher, averaging 9.2%, 13.1%, and 8.4% higher, respectively, thanDymond's AA analyses. Barium by XRF averaged 6.5% lower than byAA. By comparing our results with other N.B.S. standard carbonatemixtures run separately from our calibration, we estimate that phos-phorus may be 7.5% higher by our XRF analysis. I do not have reli-able carbonate-rich standards at the proper elemental concentrationsfor Na, Mg, K, Ti, and S, but I assume that the accuracy of these ele-mental analyses is similar to that of the elements checked.

SEDIMENT COMPOSITION

CaCO3

The major trends in CaCO3 content of Leg 92 sedi-ments (Fig. 3) are due to two major effects—dilution byhydrothermal sediments near the rise crest and dissolu-tion of CaCO3 as the Pacific Plate descends below thelysocline.

Carbonate contents are between 60 and 70% in thebasal 20 m of each hole but rise to 90% higher in thesection. The increase in carbonate above the basal sec-tion cannot be due to postdepositional dissolution, sincethere is little evidence for diagenesis except in the mostbasal 1 to 2 m of sediment. Dissolution due to lysoclineeffects does not explain why, in three different time peri-ods (27 to 18 Ma or 51.3 to 20.9 m depth in Hole 597;15.9 to 7 Ma or 43.2 to 7.0 m depth in Hole 598; and8.1 Ma to the present or 35.1 to 0 m depth in Hole 599),carbonate contents increase as the water depth of each

site increases. The best explanation for the common car-bonate trend is dilution by significant quantities of hy-drothermal sediments while the site is at the EPR crest;the dilution of carbonate decreases upcore as each sitemoves away from the ridge.

Holes 598 and 597, being on older, deeper oceaniccrust, have penetrated the lysocline. In Hole 598 thiszone is marked by highly variable but decreasing car-bonate contents in the upper 6 m of the core, whereas inHole 597 it is marked by a 2-m-thick sediment layer withlow carbonate contents. The carbonate profiles of theLeg 92 sediments are discussed in more detail by Leinen(this volume).

Fe/AlPrevious work by Boström and Peterson (1969), Dy-

mond et al. (1973), and others has shown that the basalmetalliferous (hydrothermal) sediments at the EPR arehighly enriched in Fe. This is true of the Leg 92 sedi-ments as well. Figure 4 is a plot of the Fe/Al ratio (toeliminate dilution effects by CaCO3) versus depth at thethree holes. The figure shows that Sites 598 and 599 haveFe/Al values that decrease from very high (60 to 100) inthe basal sediments to values between 3 and 10 at thepresent sediment surface. At Hole 597, however, Fe/Alchanges cyclically from 9 to 30 over the depth range from4 m to the basement (17 Ma to 28.3 Ma). From 4 m tothe surface (17 Ma to the present), Fe/Al decreases mono-

CaCO CaCOa

20 40 60 80 100

5 -

1 0 -

1 5 -

— 2 0 -E

=5 25 HΦ

CO

O

Φ 3 0 -

£

S »-

4 0 -

4 5 -

5 0 -

5 5 -

Site 597

CaCO3

20 40 60 80 100

Site 598 Site 599

Figure 3. CaCO3 (wt.%) versus depth below seafloor at Sites 597, 598, and 599. CaCO3 content is controlledby dilution with hydrothermal precipitates in the basal sediments and by dissolution before burial in thecore tops after each core passes through the lysocline.

363

M. W. LYLE

Fe/AI

12 18 24 30Fe/AI

20 40 60 80 100

Fe/AI

22 44 66 88 110

5-

10-

1 5 -

I20"8U 25

30-

40-

45-

50-

55 -

Site 597 Site 598 Site 599

Figure 4. Fe/AI versus depth below seafloor at Sites 597, 598, and 599. Site 597 is marked by the lowest Fe/AIratio and highest Al content.

tonically to a ratio near 3. The difference in average Fe/Al between the three sites is almost entirely due to high-er Al contents at Holes 597 and 598. At all three sites,the average iron concentration for the basal 10 m of sed-iment is between 8 and 10%. The average aluminum con-tent for the basal 10 m of Hole 597, however, is 0.47%,as compared with 0.15% at Hole 598 and 0.13% at Hole599. The data suggest that Hole 597 had an additionalsource of aluminum as compared with the other two sites(perhaps some type of aluminosilicate detritus). The gen-eral decrease in Fe/AI upcore, as each site travels awayfrom the source of hydrothermal sediments at the risecrest, is consistent with a general decrease of hydrother-mal influence away from the ridge and an increase rela-tive abundance of low-Fe/Al aluminosilicate debris.

Si/AlSi/Al ratio at Sites 597, 598, and 599, like Fe/AI ra-

tio, is high while the sites are at the rise crest and de-creases as the sites move away (Fig. 5). Again, the majordifferences between the sites are due primarily to the av-erage aluminum content of the sediments. The Si/Al ra-tios in the basal sediments of Holes 598 and 599 are sim-ilar to the hydrothermal Si/Al ratio of 11 found by Dy-mond (1981), and the Si/Al ratio of 3 at the top of allthree cores is similar to the value estimated by Dymondfor both authigenic and detrital end members. The Si/Al trends fit with mixing between hydrothermal precipi-

tates and either authigenic material precipitating fromseawater or aluminosilicate detritus.

Fe/PBerner (1973) and Froelich et al. (1977) have suggest-

ed that iron oxyhydroxide precipitates, which are a largefraction of metalliferous sediments, can adsorb and re-move significant amounts of phosphorus from the worldocean. Froelich et al. (1977) have estimated that about15 to 40% of the total riverine flux of P is buried annu-ally as the result of scavenging onto hydrothermal pre-cipitates and their subsequent burial. Berner's (1973) studyindicates that the amount of phosphorus contained inmetalliferous sediments is primarily adsorbed and in equi-librium with dissolved phosphorus in seawater. If seawa-ter phosphorus concentrations have not changed, it isnot surprising that the basal sediments at all three siteshave a mean Fe/P ratio between 60 and 80 (Fig. 6). Thereis an unexpectedly high degree of variability about themean of this ratio, however, and an unexpected decreasein Fe/P occurs at the tops of Holes 597 and 598. A plotof phosphorus against iron (Fig. 7) suggests that thephosphorus contents of the sediments can be explainedby the mixing of three end members: calcite (0% P, 0%Fe); a low-P, high-Fe end member; and a high-P, high-Feend member. The low-P end member appears to be atypical hydrothermal precipitate. The high-P end mem-ber, because it is associated with the more slowly accu-

364


Si/Al

2 3Si/Al

4 6 8 10

5 "

1 0 -

15-

_ 2 0 -

2 5 -

3 0 -

3 5 -

4 0 -

4 5 "

5 0 -

55 J

Site 597 Site 598

Figure 5. Si/Al versus depth below seafloor at Sites 597, 598, and 599.

Fe/P

21 42 63 84 105

Fβ/P

20 40 60 80 100

5 -

10 -

1 5 -

2 0 -

2 5 -

30

3 5 -

4 0 -

4 5 -

50 -

55 -*

Site 598

Si/Al

8 12 16 20

Site 599

Fe/P

24 48 72 96 120

Site 599

Figure 6. Fe/P versus depth below seafloor at Sites 597, 598, and 599.

365

M. W. LYLE

P (wt.%)

Figure 7. Fe (wt.%) plotted against P (wt.%) at Site 598. The distribu-tion of data is consistent with mixing low Fe/P and high Fe/P endmembers with calcite.

mulating surface sediments, probably represents eitheradditional phosphorus scavenged by the precipitates orthe increase in the relative abundances of phosphatic fishdebris in the slowly accumulating surface sediments. Thevariability of Fe/P in the basal sediments may indicatethat hydrothermal activity is intermittent and separatedby more slowly accumulating sediments or that the phos-phorus content of Pacific Ocean waters has changed dras-tically on a relatively short time scale.

Fe/MnThe Fe/Mn distribution in Leg 92 sediments was un-

expected (Fig. 8). Dymond's (1981) study suggests thatthe basal sediments should have a "hydrothermal" ratioof about 3. Upcore, the Fe/Mn ratio should trend to-ward the authigenic end member ratio of 0.5, since thereare low amounts of detrital material in the samples. Thebasal samples in all three cores have ratios of 3 but in-crease rather than decrease upcore. Only within the up-permost 2 to 4 m in each core (the sediments depositedfarthest from the EPR) does the ratio of Fe to Mn beginto decrease. Even the surface sediments have Fe/Mn val-ues greater than 3, however.

To attempt to explain this unexpected trend I gener-ated four hypotheses:

1. Changes in the type of hydrothermal activity overtime may have resulted in times when iron-rich hydro-thermal precipitates were more common and the averageFe/Mn ratio of the sediments was higher.

2. The sediments more distal from the EPR may rep-resent a mixture of Fe-rich precipitates derived from anoff-ridge hydrothermal source and ridge-derived hydro-thermal precipitates.

3. The change in Fe/Mn may mark the removal ofmanganese-rich particles from the hydrothermal plume,

so that the deposits with high Fe/Mn ratios representtypical distal hydrothermal deposits (those far from theEPR).

4. Diagenesis may have reduced and remobilized man-ganese and left behind an iron-rich solid fraction.

Hypothesis 1 (that the hydrothermal effluent was rich-er in iron in the past) can be eliminated by comparingthe Fe/Mn ratios that existed at the three sites over com-parable periods of time. For example, between 5.4 and8.6 Ma, or between 11.9 and 40.8 m depth, Site 599 wasnear the EPR crest and collected sediments with Fe/Mnvalues of about 3. During the same time period (between4.7 and 10.9 m depth in Hole 598, and between 0.5 and1 m depth in Hole 597), however, the Site 598 sedimentshave Fe/Mn ratios between 6 and 8, and the Site 597sediments have ratios between 3.5 and 7. There is no pe-riod in time in which all three cores have Fe/Mn ratiosthat are consistently higher than in other time periods.

Data from surface sediments reported in Dymond(1981) and downcore data reported in this paper indi-cate a strong relationship between Fe/Mn and distancefrom the rise crest, not time. Figure 9 compares the Fe/Mn ratio to the distance from the rise crest at which thesediments were deposited for both sediments from thethree Leg 92 holes and for surface sediments from theEPR. In each hole, depth in the sediment has been con-verted to distance from the rise crest by assuming a con-stant spreading rate and using the age-depth scales inFigure 2. The assumption of a constant spreading ratemay introduce small errors, but they are not particularlyimportant for this comparison. Figure 9 shows that thetransition in Fe/Mn ratios in both modern and ancientsediments occurs on the ridge flanks, between 150 and300 km from the rise axis. The high-Fe/Mn zones clear-ly do not mark time horizons but instead define a pro-cess related to distance from the rise crest.

Diagenetic remobilization of manganese (hypothesis4) can be eliminated as a cause of high Fe/Mn ratio byboth surface-sediment and downcore information. If dia-genetic processes were removing manganese from the sed-iments, the surface sediments marked by high Fe/Mnmore than 250 km from the EPR must now be losing ex-tensive amounts of manganese to bottom waters. Thepore water information obtained from this and other legs(Gieskes et al., this volume, for example) shows that no-where in the area do sediments become sufficiently re-ducing for this to occur. In addition, the downcore Fe/Mn profiles require that times in the past were signifi-cantly more oxic to preserve the low Fe/Mn basal sed-iments. There is no evidence for a change in redox con-ditions here in the stable center of the South Pacific gyre.

The hydrothermal processes implicit in Hypothesis 2(the off-ridge hydrothermal source hypothesis) are un-likely to occur. If Hypothesis 2 is true, an off-ridge hy-drothermal system must be located at least 100 km fromthe crest of the EPR and must emit hydrothermal fluidsrich in iron.

Experimental studies have outlined the restricted con-ditions that can produce hydrothermal fluids high in iron(Bischoff and Dickson, 1975; Seyfried and Bischoff, 1977,1979; Mottl et al., 1979; Seyfried and Mottl, 1982). Ex-

366


Fe/Mn Fe/Mn

4 6 8 10

Fe/Mn

2 4 6 8 10

Site 598 Site 599

55 J

Figure 8. Fe/Mn profiles at Sites 597, 598, and 599. Low Fe/Mn ratio ( 3) in basal sediments is similar tothat observed by Dymond (1981). High Fe/Mn near the core tops is not predicted by Dymond's model,however.

8 -

7 -

6 -

5 "

4 -

3 -

1

-

1 |

Site598

V

1 1

Present(surface sediments) »

Å \Site ^ v597

I |

1 1

Site

j i

1

Risecrest

f ^ C

1

-

-

650 550 450

West

350 250

Distance to rise crest (km)

150 50 50

Figure 9. Comparison of Fe/Mn ratios in Leg 92 cores to Fe/Mn in modern sediments (open circles). The transition from low tohigh Fe/Mn occurs at approximately the same distance from the rise crest in ancient and modern sediments. The processthat causes the change is still active today.

367

M. W. LYLE

perimental fluids with Fe/Mn ratios greater than 5 havebeen produced only at temperatures greater than 400°Cat low water/rock ratios (Mottl et al., 1979). At highwater/rock ratios (>50; Seyfried and Mottl, 1982), thetemperature at which high solution Fe/Mn occurs is on-ly slightly lower (300°C).

Thus, if the high Fe/Mn ratio is due to additional hy-drothermal activity, an extensive off-ridge hydrothermalsource must exist at least 100 km from the spreading ax-is and must emit fluids as hot as the hottest hydrother-mal fluids found at the spreading axis (RISE ProjectGroup, 1980). Such high-temperature, off-ridge hydro-thermal systems have been neither observed nor predict-ed (Anderson and Hobart, 1976; Lister, 1977).

The third hypothesis (that the deposits with high Fe/Mn ratios represent distal hydrothermal material) con-flicts with speculations by Edmond et al. (1979) that hy-drothermal Fe/Mn ratios in ferromanganese oxyhydrox-ide precipitates result from the saturation of surfaces ofan initial Fe-rich oxyhydroxide precipitate with more slow-ly oxidizing manganese. By that model, the most distalhydrothermal deposits should either have a constant Fe/Mn ratio or be rich in manganese, because Mn is precip-itated more slowly than Fe.

The compositional data from Leg 92 show that themost distal deposits are the richest in iron, however, andpresent an apparent paradox: the sediments depositedfarthest from the EPR crest are most enriched in the ele-ment that should precipitate first from the hydrother-mal fluid. The paradox can be resolved if one realizesthat precipitation is not equivalent to sedimentation andburial. If a precipitate has a small enough particle size,it can drift for hundreds, perhaps thousands of kilome-ters before settling to the bottom.

The rapid mixing of hydrothermal fluids with normalseawater, as observed at 21 °N, results in a large size rangeof iron-rich oxyhydroxide particulates and more coarse-grained sulfides. Even though most of this material willsettle out rapidly, a small fraction of the precipitatingmaterial will be both colloidal in size and rich in iron.This was in fact first observed in the early studies ofEPR sediments (Boström and Peterson, 1966). This frac-tion can drift far from the rise crest. Manganese, on theother hand, even though it should remain dissolved inseawater longer than iron, is essentially an insoluble ele-ment in oxygenated seawater and is readily scavengedonto falling particles (Weiss, 1977; Martin and Knauer,1983). Dissolved manganese can therefore be strippedfrom the water column by falling particulates long be-fore colloidal iron-rich oxyhydroxide particles will havesettled to the bottom. Distal hydrothermal deposits morethan 200 km from the rise crest can therefore be rich iniron even though iron is more rapidly precipitated thanmanganese.

FACTOR ANALYSIS OF LEG 92 SEDIMENTS

Factor analysis, as proposed by Miesch (1976) and byLeinen and Pisias (1984), provides a way to deduce thechemical composition of hypothetical end members inmixtures such as Leg 92 sediments and a way to see wheth-er the chemical composition of distal deposits at the EPR

are consistent with the hypothesis that an iron-rich frac-tion drifted from the rise crest. A factor analysis of thecombined data set from Sites 597, 598, and 599 showsthat three factors can explain 97% of the compositionalvariance in the data set (Table 2). The factors (end mem-bers) chosen by this more objective method reinforce theconclusions drawn in earlier sections.

Factor 1, which explains 43% of the total variance inthe data set, is typical of hydrothermal material. It isdominated by Mn, Fe, and P (possibly because of copre-cipitation with Fe, as suggested by Berner [1973]), and itdominates the sediment mixture at the base of each Leg92 site. Factor 2, which explains 36% of the data vari-ance, is dominated by Ca, K, and Ba and apparentlyrepresents biogenic calcite and barite. The Ba/S weightratio in the end member is 3.6, similar to a stoichiomet-ric barite (Ba/S = 4.3). The factors distribution is simi-lar to the calcite distribution in each core.

I call Factor 3, which explains 18% of the data vari-ance, the distal factor. The distribution downcore of Fac-tor 3 (Fig. 10) points out its distal association. It onlydominates the sediment assemblage at the top of eachcore and is relatively low in importance downcore, whereeach site was near the rise crest. The factor is dominatedby Al, Si, Ti, and P, all associated with slowly accumu-lating aluminosilicate debris or with apatitic fish debris.It is also marked by very high Fe contents. The Fe/Si ra-tio in the distal factor is 2.8, as compared with 1.2 in themost iron-rich hydrothermal clays (e.g., nontronite Nl;Corliss et al., 1978). Clearly, excess iron oxyhydroxidesare present in the factor. From these observations andfrom its dominance only in slowly accumulating sedi-ments, the distal factor is probably a mixture of alumi-nosilicates, slowly accumulating apatitic fish debris, andvery fine-grained iron-rich hydrothermal precipitates thathave drifted far from the rise crest. The presence of alu-minosilicates, shown by the high Al and Si loadings, prob-ably represents fine-grained eolian detritus. I interpretthe high P loading in this factor to be due to apatiticfish debris.

Table 2. Results of factor analysis of the combined Site 597, 598, and599 data.a

Element

NaMgAlSiPKCaTiMnFeBaSVariance0

Factor 1I(hydrothermal)

Composition(wt.%)

0.3280.84001.240.2180.971

21.60.0135.18

13.20.0550.045

43%

Factorscore'3

1.3700.975

-0.5840.5621.1170.4040.197

-0.1322.2151.3650.0900.519

Factor :I(biogenic)

Composition(wt.%)

00.2680.0780.28401.08

40.20.02201.590.0900.025

36%

Factorscore^

-0.3090.5820.2850.151

-0.5241.5942.1300.837

-0.5060.0951.5790.805

Factor 3(distal)

Composition(wt.%)

0.7791.743.398.450.9901.4900.2932.27

23.70.3000.199

18%

Factorscore'5

0.5050.0482.5771.0961.109

-0.350-0.682

1.302-0.448

0.0950.1050.408

a The data were weighted by normalization to equal means; resulting factors were rotated bythe VARIMAX algorithm and compositions determined by the QROTATE algorithm ofLeinen and Pisias (1984).Factor score is a measure of the importance of each element in determining the factor. Highfactor scores mark elements dominating the factor.

c Variance given is the percent of the total sums of squares in the data set explained by the fac-tor.

368


i.oi r

0.8

0.6

0.4

0.2

0.0

D Site 597

• Site 598

• Site 599

# \

• Q3 D

: • :

'.. , A A

y t

D

Λ

10 20 30

Depth below seafloor (m)

40 50

Figure 10. Depth distribution of the distal factor (see Table 2 and text) at Sites 597, 598, and 599. The distal fac-tor only dominates in the slowly accumulating sediments in the top of each core.

CONCLUSIONS

Leg 92 basal sediments contain hydrothermal precipi-tates similar to those described by Dymond (1981). Thereis no evidence for variations in basal sediment composi-tion due to changes in the composition of hydrothermalsource waters. Upcore there is strong evidence that pre-cipitates carried in the hydrothermal plume become frac-tionated due to size-settling effects. Because of precipi-tation kinetics, iron-rich oxyhydroxides are precipitatedfirst from the hydrothermal waters. Relatively coarse-grained material (probably > 10 to 20 µm) settles outnear the vents. It is eventually joined by the more slow-ly oxidizing hydrothermal manganese, which is strippedfrom the water column by both hydrothermal and bio-genic particulate debris. The very fine-grained iron-richparticles drift far from the hydrothermal vents, eventu-ally enriching distal deposits in Fe oxyhydroxides. Distaldeposits west of the EPR, because they accumulate be-low the lysocline and are isolated from sediment sourceterrains, are sediments typical of central gyre regions.They also collect eolian aluminosilicates and apatitic fishdebris, and they are unusual only in their high iron con-tents inherited from distant hydrothermal activity.

REFERENCES

Anderson, R. N., and Hobart, M. A., 1976. The relation betweenheat flow, sediment thickness, and age in the eastern Pacific. J.Geophys. Res., 81:2968-2989.

Berner, R. A., 1973. Phosphate removal from sea water by adsorptionon volcanogenic ferric oxides. Earth Planet. Sci. Lett., 18:77-86.

Bischoff, J. L., and Dickson, F. W., 1975. Seawater-basalt interactionat 200°C and 500 bars: implications for origin of sea-floor heavy-

metal deposits and regulation of seawater chemistry. Earth Planet.Sci. Lett., 25:385-397.

Boström, K., and Peterson, M. N. A., 1966. Precipitates from hy-drothermal exhalations on the East Pacific Rise. Econ. Geol., 61:1258-1265.

, 1969. The origin of aluminum-poor ferromanganoan sedi-ments in areas of high heat flow on the East Pacific Rise. Mar.Geol., 7:427-447.

Corliss, J. B., Lyle, M., Dymond, J., and Crane, C , 1978. The chem-istry of hydrothermal mounds near the Galapagos Rift. Earth Plan-et. Sci. Lett., 40:12-24.

Dymond, J., 1981. Geochemistry of Nazca Plate surface sediments:an evaluation of hydrothermal, biogenic, detrital, and hydroge-nous sources. In Kulm, L. D., Dymond, J., Dasch, E. J., Hus-song, D. M., and Roderick, R. (Eds.), Nazca Plate: Crustal For-mation and Andean Convergence. Geol. Soc. Am. Mem., 154:133-174.

Dymond, J., Corliss, J. B., Heath, G. R., Field, C. W., Dasch, E. J.,and Veeh, H. H., 1973. Origin of metalliferous sediments from thePacific Ocean. Geol. Soc. Am. Bull., 84:3355-3372.

Dymond, J., Corliss, J. B., and Stillinger, R., 1976. Chemical compo-sition and metal accumulation rates of metalliferous sediments fromSites 319, 320, and 321. In Yeats, R. S., Hart, S. R., et al., Init.Repts. DSDP, 34: Washington (U.S. Govt. Printing Office), 575-588.

Edmond, J. M., Measures, C , Mangum, B., Grant, B., Sclater, F. R.,Collier, R., Hudson, A., Gordon, L. I., and Corliss, J. B., 1979.On the formation of metal-rich deposits at ridge crests. Earth Plan-et. Sci. Lett., 46:19-30.

Froelich, P. N., Bender, M. L., and Heath, G. R., 1977. Phosphorusaccumulation rates in metalliferous sediments on the East PacificRise. Earth Planet. Sci. Lett., 34:351-359.

Leinen, M., and Pisias, N., 1984. An objective technique for deter-mining end-member compositions and for partitioning sedimentsaccording to their sources. Geochim. Cosmochim. Acta, 48:47-62.

Lister, C. R. B., 1977. Qualitative models of spreading-center process-es, including hydrothermal penetration. Tectonophysics, 37:203-218.

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Lupton, J. E., and Craig, H., 1981. A major helium-3 source at 15°Son the East Pacific Rise. Science, 214:13-18.

Martin, J. H., and Knauer, G. A., 1983. VERTEX: manganese trans-port with CaCO3. Deep-Sea Res., 30:411-425.

Miesch, A. T., 1976. Q-mode factor analysis of geochemical and pet-rologic data matrices with constant row-sums. Geol. Surv. Prof.Pap. U.S., 574-G.G1-G47.

Mottl, M. J., Holland, H. D., and Corr, R. E, 1979. Chemical ex-change during hydrothermal alteration of basalt by seawater—II.Experimental results for Fe, Mn, and sulfur species. Geochim. Cos-mochim. Ada, 43:869-884.

Reid, J. L., 1982. Evidence of an effect of heat flux from the East Pa-cific Rise upon the characteristics of the mid-depth waters. Geo-phys. Res. Lett., 9:381-384.

RISE Project Group, 1980. East Pacific Rise: hot springs and geo-physical experiments. Science, 207:1421-1433.

Seyfried, W., and Bischoff, J. L., 1977. Hydrothermal transport ofheavy metals by seawater: the role of seawater/basalt ratio. EarthPlanet. Sci. Lett., 34:71-77.

, 1979. Low temperature basalt alteration by seawater: an ex-perimental study at 70° C and 150°C. Geochim. Cosmochim. Ac-ta, 43:1937-1947.

Seyfried, W. E., Jr., and Mottl, M. J., 1982. Hydrothermal alterationof basalt by seawater under seawater-dominated conditions. Geo-chim. Cosmochim. Acta, 46:985-1002.

Weiss, R. E, 1977. Hydrothermal manganese in the deep sea: scaveng-ing residence time and Mn/3-He relationships. Earth Planet. Sci.Lett., 37:257-262.

Yeats, R. S., Hart, S. R., et al., 1976. Init. Repts. DSDP, 16: Wash-ington (U.S. Govt. Printing Office).

Date of Initial Receipt: 13 July 1984Date of Acceptance: 5 February 1985

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18. major element composition of leg 92 sediments1 ... · mitchell w. lyle, college of...

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