The geochemistry of sulfur in a 1.3 km section of hydrothermally altered oceanic crust, DSDP Hole 504B

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doi: 10.1016/0016-7037(89)90206-8
Author(s): Alt, Jeffrey C.; Anderson, Thomas F.; Bonnell, Linda
Author Affiliation(s): Primary:
Wash. Univ., Dep. Earth and Planet. Sci., St. Louis, MO, United States
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, 53(5), p.1011-1023. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. 68 refs.; illus. incl. 2 tables, sketch map
Summary: The lithostratigraphy, distribution of secondary minerals and petrology of pillow basalts and of hydrothermally altered transition zone and sheeted dykes cored in DSDP Hole 504B, located in 5.9 m.y. crust in the E Pacific, are summarized. Minerals were identified in >200 polished thin sections and analysed. Pyrite, sphalerite and anhydrite were separated from veins for S isotopic analysis. Monosulphide S, soluble sulphate and pyrite S were extracted from whole rock powders for S isotopes. Igneous sulphides include pyrrhotite, with pentlandite, chalcopyrite, cubanite; most are altered in the upper pillow basalts to Fe- oxyhydroxides. In the hydrothermally altered zone and dykes, chalcopyrite, pyrite are dominant sulphides, with bornite, sphalerite, millerite and galena. S isotope analyses show that the pillow lavas have lost S to sea-water. Hydrothermally altered rocks are enriched in S and 34S compared with the sheeted dykes, indicating the presence of predominantly basaltic S in hydrothermal fluids deep in the crust. The S and delta34S enrichments in the transition zone are due to sea-water sulphate reduction and sulphide deposition during subsurface mixing between upwelling hot hydrothermal fluids and sea-water. Basaltic S was lost to sea-water through alteration of the upper crust with minor sea-water S fixed in the crust, and magmatic S redistributed within the crust with increases in S content and delta34S in the upper 1.8 km of the oceanic crust.
Year of Publication: 1989
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; Anhydrite; Basalts; Crust; DSDP Site 504; Deep Sea Drilling Project; Dikes; Equatorial Pacific; Geochemistry; Hydrothermal alteration; Hydrothermal conditions; IPOD; Igneous rocks; Intrusions; Isotopes; Lava; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Metamorphic rocks; Metasomatic rocks; Metasomatism; Mineral assemblages; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Pillow lava; Reactions; Reduction; S-34/S-32; Sea water; Stable isotopes; Sulfates; Sulfides; Sulfur; Volcanic rocks
Coordinates: N011000 N011000 W0834500 W0834500
Record ID: 1989045961
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom