Carbonate veins trace seawater circulation during exhumation and uplift of mantle rock : results from ODP Leg 209
Robinson, Laura F.
MetadataShow full item record
KeywordHydrothermal processes; Seawater circulation; Carbonate veining; Ocean-crust exchange; Li isotopes; Age dating
Carbonate veins hosted in ultramafic basement drilled at two sites in the Mid Atlantic Ridge 15°N area record two different stages of fluid-basement interaction. A first generation of carbonate veins consists of calcite and dolomite that formed syn- to postkinematically in tremolite–chlorite schists and serpentine schists that represent gently dipping large-offset faults. These veins formed at temperatures between 90 and 170 °C (oxygen isotope thermometry) and from fluids that show intense exchange of Sr and Li with the basement (87Sr/86Sr = 0.70387 to 0.70641, δ7LiL-SVEC = + 3.3 to + 8.6‰). Carbon isotopic compositions range to high δ13CPDB values (+ 8.7‰), indicating that methanogenesis took place at depth. The Sr–Li–C isotopic composition suggests temperatures of fluid-rock interaction that are much higher (T > 350–400 °C) than the temperatures of vein mineral precipitation inferred from oxygen isotopes. A possible explanation for this discrepancy is that fluids cooled conductively during upflow within the presumed detachment fault. Aragonite veins were formed during the last 130 kyrs at low-temperatures within the uplifted serpentinized peridotites. Chemical and isotopic data suggest that the aragonites precipitated from cold seawater, which underwent overall little exchange with the basement. Oxygen isotope compositions indicate an increase in formation temperature of the veins by 8–12 °C within the uppermost ~ 80 m of the subseafloor. This increase corresponds to a high regional geothermal gradient of 100–150 °C/km, characteristic of young lithosphere undergoing rapid uplift.
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 311 (2011): 242–252, doi:10.1016/j.epsl.2011.09.021.
Showing items related by title, author, creator and subject.
Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the seawater–brine interface Shah, Sunita R.; Joye, Samantha B.; Brandes, Jay A.; McNichol, Ann P. (Copernicus Publications on behalf of the European Geosciences Union, 2013-05-13)Orca Basin, an intraslope basin on the Texas-Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200 m in which limited microbial activity has been reported. This brine contains a large reservoir ...
Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean Cooper, Lee W.; Benner, Ronald; McClelland, James W.; Peterson, Bruce J.; Holmes, Robert M.; Raymond, Peter A.; Hansell, Dennis A.; Grebmeier, Jacqueline M.; Codispoti, Louis A. (American Geophysical Union, 2005-12-07)Concentrations of dissolved organic carbon (DOC) and δ18O values have been determined following sampling of runoff from a number of major arctic rivers, including the Ob, Yenisey, Lena, Kolyma, Mackenzie and Yukon in ...
B content and Si/C ratios from cultured diatoms (Thalassiosira pseudonana and Thalassiosira weissflogii) : relationship to seawater pH and diatom carbon acquisition Mejia, Luz Maria; Isensee, Kirsten; Mendez-Vicente, Ana; Pisonero, Jorge; Shimizu, Nobumichi; Gonzalez, Cristina; Monteleone, Brian D.; Stoll, Heather M. (Elsevier, 2013-06-18)Despite the importance of diatoms in regulating climate and the existence of large opal-containing sediments in key air-ocean exchange areas, most geochemical proxy records are based on carbonates. Among them, Boron (B) ...