On the formation of metal-rich deposits at ridge crests |
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| Authors: | JM Edmond C Measures B Mangum B Grant FR Sclater R Collier A Hudson LI Gordon JB Corliss |
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| Institution: | Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 U.S.A.;School of Oceanography, Oregon State University, Corvallis, OR 97331 U.S.A. |
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| Abstract: | Data from the hot springs at the Galapagos spreading center (T = 3–13°C) show depletions of the exiting waters in Cu, Ni, Cd, Se, Cr and U relative to ambient seawater. Manganese is strongly enriched. Iron shows highly variable behavior between vent fields but is in general low. The data confirm the occurrence of extensive subsurface mixing between the primary high-temperature, acid, reducing hydrothermal fluids and “groundwater”. The composition of the latter is indistinguishable from that of the free water column adjacent to the ridge axis. The final solutions are on the boundary between those forming MnO2 crusts and those producing iron-manganese rich sediments. The suite of metal rich deposits observed at ridge crests — Mn-O, Fe-Mn-O, Fe-S — can be explained as the manifestation of the degree of subsurface mixing, decreasing from 100 : <1 to <1 : 1 across the series (assuming an end-member temperature of 350°C). |
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