Strontium, oxygen, and hydrogen isotope geochemistry of hydrothermally altered and weathered rocks in DSDP Hole 504B, Costa Rica Rift

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doi: 10.1016/0012-821X(87)90132-4
Author(s): Kawahata, Hodaka; Kusakabe, Minoru; Kikuchi, Yoshiko
Author Affiliation(s): Primary:
Geol. Surv. Jap., Ibaraki, Japan
Okayama Univ., Japan
Toyama Univ., Japan
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 85(4), p.343-355. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 53 refs.; illus. incl. 4 tables
Summary: DSDP Hole 504B was drilled into 6 m.y. crust, approx 200 km south of the Costa Rica Rift, Galapagos Spreading Centre, penetrating 1.35 km into a section that can be divided into four zones - Zone I: oxic submarine weathering; Zone II: anoxic alteration; Zones III and IV: hydrothermal alteration to greenschist facies. In zone III there is intense veining of pillow basalts. Zone IV consists of altered sheeted dykes. Isotopic geochemical signatures in relation to the alteration zones at various depths are given. Alteration T are as low as 10°C in Zones I and II based on oxygen isotope fractionation. Sr isotopic data indicate that a circulation of sea-water is much more restricted in Zone II than in Zone I. Fluid inclusion measurements of vein quartz indicate that the alteration T was mainly 300 + or - 20°C in Zones III and IV, which is consistent with secondary mineral assemblages. The Sr, O and H isotopic compositions of hydrothermal fluids which were responsible for the greenschist facies alteration in Zones II and IV are estimated to be 0.7037, 2per mille and 3per mille respectively. Sr and O isotope data indicate that completely altered portions of greenstones and vein minerals were in equilibrium with modified sea-water under low water/rock ratios (in weight) of approx 1.6. This value is close to that of the end-member hydrothermal fluids issuing at 21°N EPR.
Year of Publication: 1987
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Alkaline earth metals; Basalts; Costa Rica Rift; D/H; DSDP Site 504; Deep Sea Drilling Project; Deuterium; East Pacific; Galapagos Rift; Geochemistry; Hydrogen; Hydrothermal alteration; IPOD; Igneous rocks; Isotopes; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Metals; Metasomatism; Mineral assemblages; O-18/O-16; Ocean Drilling Program; Oxygen; Pacific Ocean; Sr-87/Sr-86; Stable isotopes; Strontium; Volcanic rocks
Coordinates: N011335 N011338 W0834348 W0834357
N011203 N011400 W0834000 W0834500
N011338 N011338 W0834349 W0834349
N011338 N011338 W0834349 W0834349
N011300 N011340 W0834320 W0834400
N011000 N020000 W0834000 W0835000
N003000 N014000 W0834000 W0863000
N011337 N011338 W0834348 W0834349
S192706 N011400 W0834349 W1294614
Record ID: 1988007327
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom