Strontium and oxygen isotopic composition of some basalts from Hole 504B, Costa Rica Rift, DSDP legs 69 and 70

Online Access: Get full text
doi: 10.1016/0012-821X(82)90017-6
Author(s): Barrett, T. J.; Friedrichsen, H.
Author Affiliation(s): Primary:
Oxford Univ., Dep. Geol. and Mineral., Oxford, United Kingdom
Univ. Tueb., Federal Republic of Germany
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 60(1), p.27-38. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 44 refs.; illus. incl. 17 anal., 1 table, sketch map
Summary: Whole-rock samples (17) 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 ratios for eight samples from the upper 260 m range 0.70287-0.70377, with a mean of 0.70320. In the 330-560 m intervals, five samples range 0.70255-0.70279, with a mean of 0.70266, which is the average value for fresh MORB. Intermediate Sr ratios were found in the 260-330 m interval. delta 18O values in the upper 260 m are typical of basalts which have undergone low-T sea-water alteration, whereas the values for the 320-560 m interval correspond with MORB which have experienced no O-isotopic alteration. The higher 87Sr/86Sr and 18O/16O ratios in the upper part of the whole can be interpreted as a result of a greater overall water/rock ratio than in the lower part. Interaction of basalt with sea-water increased Sr ratios and produced smectite alteration products which raised whole-rock delta 18O values. Sea-water circulation in the lower basalts may have been restricted by impermeable massive lava flows below approx 230 m sub-basement.
Year of Publication: 1982
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; Alkaline earth metals; Basalts; Costa Rica Rift; Crust; DSDP Site 504; Deep Sea Drilling Project; East Pacific; Galapagos Rift; Geochemistry; Halmyrolysis; IPOD; Igneous rocks; Isotopes; Lava; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Metals; O-18/O-16; Ocean Drilling Program; Oceanic crust; Oxygen; Pacific Ocean; Rift zones; South American Pacific; South Pacific; Southeast Pacific; Sr-87/Sr-86; Stable isotopes; Strontium; Volcanic rocks; Whole rock
Coordinates: N000000 N020000 W0830000 W0841500
Record ID: 1983002759
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom