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Barrett, T J; Friedrichsen, Hans (1982): 87Sr/86Sr ratios, Sr and Rb concentrations and stable oxygen isotope values for some basalts from ODP Hole 504B (Table 1). PANGAEA,, Supplement to: Barrett, TJ; Friedrichsen, H (1982): Strontium and oxygen isotopic composition of some basalts from Hole 504B, Costa Rica Rift, DSDP Legs 69 and 70. Earth and Planetary Science Letters, 60(1), 27-38,

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Seventeen whole-rock samples, generally taken at 25-50 m intervals from 5 to 560 m sub-basement in Hole 504B, drilled in 6.2 m.y. old crust, were analysed for 87Sr/86Sr ratios, Sr and Rb concentrations, and 18O/16O ratios. Sr isotope ratios for 8 samples from the upper 260 m of the hole range from 0.70287 to 0.70377, with a mean of 0.70320. In the 330-560 m interval, 5 samples have a restricted range of 0.70255-0.70279, with a mean of 0.70266, the average value for fresh mid-ocean ridge basalts (MORB). In the 260-330 m interval, approximately intermediate Sr isotopic ratios are found.
Delta18O values (‰) range from 6.4 to 7.8 in the upper 260 m, 6.2-6.4 in the 270-320 m interval, and 5.8-6.2 in the 320-560 m interval. The values in the upper 260 m are typical for basalts which have undergone low-temperature seawater alteration, whereas the values for the 320-560 m interval correspond to MORB which have experienced essentially no oxygen isotopic alteration.
The higher 87Sr/86Sr and 18O/16O ratios in the upper part of the hole can be interpreted as the result of a greater overall water/rock ratio in the upper part of the Hole 504B crust than in the lower part. Interaction of basalt with seawater (87Sr/86Sr = 0.7091) increased basalt 87Sr/86Sr ratios and produced smectitic alteration products which raised whole-rock delta18O values. Seawater circulation in the lower basalts may have been partly restricted by the greater number of relatively impermeable massive lava flows below about 230 m sub-basement. These flows may have helped to seal off lower basalts from through-flowing seawater.
Median Latitude: 1.227100 * Median Longitude: -83.730100 * South-bound Latitude: 1.227000 * West-bound Longitude: -83.730200 * North-bound Latitude: 1.227200 * East-bound Longitude: -83.730000
Date/Time Start: 1979-10-07T00:00:00 * Date/Time End: 1979-12-04T00:00:00
69-504B * Latitude: 1.227200 * Longitude: -83.730200 * Date/Time: 1979-10-07T00:00:00 * Elevation: -3460.0 m * Penetration: 489 m * Recovery: 262 m * Campaign: Leg69 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL)
70-504B * Latitude: 1.227000 * Longitude: -83.730000 * Date/Time: 1979-12-04T00:00:00 * Elevation: -3460.0 m * Penetration: 836.1 m * Recovery: 91.6 m * Campaign: Leg70 * Basis: Glomar Challenger * Device: Drilling/drill rig (DRILL) * Comment: 40 cores; 328.6 m cored; 18.5 m drilled; 27.9 % recovery
#NameShort NameUnitPrincipal InvestigatorMethodComment
1Event labelEvent
3Sample code/labelSample labelBarrett, T JODP sample designation
4Sample code/label 2Sample label 2Barrett, T J
5Lithology/composition/faciesLithologyBarrett, T J
6AlterationAlterationBarrett, T JG = colourless to green smectites occurring as alteration products of olivine and glass, and as vesicle fillings. R = reddish-brown alteration minerals indicative of relatively oxidizing conditions (hematite, Fe hydroxide, iddingsite), occurring as alteration products of olivine and glass, and as vesicle fillings. P = pyrite, indicative of relatively reducing conditions. Where pyrite is indicated, it is not present in the actual sample, but in veins within 30 cm above or below it
7RubidiumRbmg/kgBarrett, T JX-ray fluorescence (XRF)
8StrontiumSrmg/kgBarrett, T JX-ray fluorescence (XRF)
9Strontium 87/Strontium 86 ratio87Sr/86SrBarrett, T JIsotope ratio mass spectrometry
10Strontium 87/Strontium 86, error87Sr/86Sr e±Barrett, T JIsotope ratio mass spectrometry
11delta 18Od18Oper milBarrett, T JIsotope ratio mass spectrometry
12Water in rockH2O%Barrett, T J
153 data points

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