Massive sulfide deposits at 21°N, East Pacific Rise: Chemical composition, stable isotopes, and phase equilibria

Abstract

Research Article| August 01, 1984 Massive sulfide deposits at 21°N, East Pacific Rise: Chemical composition, stable isotopes, and phase equilibria ROBERT A. ZIERENBERG; ROBERT A. ZIERENBERG 1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706 Search for other works by this author on: GSW Google Scholar WAYNE C. SHANKS, III; WAYNE C. SHANKS, III 1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706 Search for other works by this author on: GSW Google Scholar JAMES L. BISCHOFF JAMES L. BISCHOFF 2U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information ROBERT A. ZIERENBERG 1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706 WAYNE C. SHANKS, III 1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706 JAMES L. BISCHOFF 2U.S. Geological Survey, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1984) 95 (8): 922–929. https://doi.org/10.1130/0016-7606(1984)95<922:MSDANE>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ROBERT A. ZIERENBERG, WAYNE C. SHANKS, JAMES L. BISCHOFF; Massive sulfide deposits at 21°N, East Pacific Rise: Chemical composition, stable isotopes, and phase equilibria. GSA Bulletin 1984;; 95 (8): 922–929. doi: https://doi.org/10.1130/0016-7606(1984)95<922:MSDANE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Study of massive sulfide deposits at 21°N, East Pacific Rise (EPR) indicates that coexisting sulfide minerals are not in isotopic equilibrium. Sulfur isotope values of sulfide mineral separates range from 1.5 to 4.5 per mil and indicate isotopic disequilibrium. Isotopic fractionation between coexisting minerals is small (<0.5). Larger differences between samples can be attributed to temporal variations in the isotopic values of H2S in the venting fluids. Sulfur isotope values of anhydrite and barite indicate disequilibrium with coexisting sulfides and show that ambient sea-water sulfate, not the hydrothermal fluid, is the sulfur source for anhydrite and barite. Oxygen isotope geothermometry applied to anhydrite sulfate provides temperatures of 194 and 222 °C. Detailed petrographic study of mineral paragenesis shows that the initial hydrothermal precipitates form from a fluid with Fo2-Fs2 values that are below the pyrite-pyrrhotite boundary. High-iron wurtzite may initially precipitate within the pyrrhotite stability field, but most wurtzite co-precipitates with pyrite as the fluid evolves into the pyrite stability field by mixing with cold oxygenated sea water. Precious-metal values, with the exception of silver, are uniformly low, especially for the platinoid metals. Silver content ranges to 240 ppm. Silver is predominantly associated with zinc-sulfide phases and does not occur in significant amounts as a discrete silver-bearing mineral. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.