Analysis of stable sulfur isotopes and trace cobalt on sulfides from the TAG hydrothermal mound
Friedman, Carrie T.
MetadataShow full item record
Stable sulfur isotopes (δ34S) and trace Co are analyzed in sulfide and sulfate minerals from six sample types collected from the TAG active mound, 26°N Mid-Atlantic Ridge. δ34S values range from 2.7 to 2O.9%, with sulfate minerals isotopically indistinguishable from seawater (21%), and sulfide minerals reflecting input of 1/3 seawater and 2/3 basaltic sulfur (~0%). Co concentrations in pyrite analyzed by ion microprobe primarily reflect depositional temperatures. The δ34S and Co data are combined to provide information regarding the sources and temperatures of parent fluids, the genetic relationships among sample types, and the circulation of hydrothermal fluids and seawater in the mound. δ34S values and Co concentrations vary by sample type. Chalcopyrite from black smoker samples exhibits invariant δ34S values, indicating direct precipitation from black smoker fluids. Crust samples contain chalcopyrite with a mean δ34S indistinguishable from that of black smoker samples, and pyrite with some light δ34S and moderately high Co values, consistent with crust samples precipitating from cooled black smoker fluids. Massive anhydrite samples are a mixture of anhydrite with high δ34S, and pyrite with variable δ34S and Co values, indicative of deposition from disequilibrium mixing between black smoker fluids and seawater. White smoker samples contain chalcopyrite and sphalerite with high δ34S, and pyrite with low Co values, reflecting deposition from cooler fluids formed from mixtures of seawater and black smoker fluid, with some reduction of sulfate. Mound samples contain chalcopyrite with a mean δ34S indistinguishable from that of black smoker and crust samples, and pyrite with low Co values, suggesting deposition from a fluid isotopically similar to black smoker fluid at temperatures similar to those of white smoker fluid. Massive sulfide samples exhibit pyrite with high δ34S values and very high Co, indicating deposition from and recrystallization with very hot fluids contaminated with seawater-derived sulfate. The data demonstrate that direct precipitation from black smoker fluids, conductive cooling, disequilibrium mixing with entrained seawater, sulfate reduction, and recrystallization all contribute to the formation of the TAG mound deposit. The successful preliminary Co analyses demonstrate that ion microprobe analyses are a viable technique for measuring trace elements in sulfides.
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1998
Showing items related by title, author, creator and subject.
Reproductive traits of pioneer gastropod species colonizing deep-sea hydrothermal vents after an eruption Bayer, Skylar R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2011-06)The colonization dynamics and life histories of pioneer species are vital components in understanding the early succession of nascent hydrothermal vents. The reproductive ecology of pioneer species at deep-sea hydrothermal ...
McDermott, Jill M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-02)This thesis examines the controls on organic, inorganic, and volatile species distributions in hydrothermal fluids venting at Von Damm and Piccard, two vent fields at the ultraslow spreading Mid-Cayman Rise, Earth’s deepest ...
Humphris, Susan E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1976-10)Considerable geological and geophysical evidence now exists to support the hypothesis that seawater circulates through freshly intruded basalt at the mid-ocean ridges. As a consequence of this process, reactions between ...