Silver in sulfide chimneys and mounds from 13°N and 21°N, East Pacific Rise

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Authors:Moss, R.; Scott, S. D.
Author Affiliations:Primary:
University of Toronto, Marine Geology Research Laboratory, Toronto, ON, Canada
Volume Title:Canadian Mineralogist
Source:The Canadian Mineralogist, Vol.34(Part 4), p.697-716. Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada. ISSN: 0008-4476
Publication Date:1996
Note:In English. 66 refs.; illus., incl. 6 tables, sketch map
Summary:The 349°C hydrothermal vent from the SW vent field (21°N) is enriched in Ag by ∼ three orders of magnitude compared to sea-water. This Ag is shown to be transported as the dichlorosilver(I) complex, and to be undersaturated with respect Ag2S. The absence of a separate Ag phase such as acanthite in these chimneys suggests that the Ag remains undersaturated with respect to Ag2S during cooling and mixing of the hydrothermal fluid with sea-water. However, Ag is present to a limited extent in sulphides throughout the paragenesis of chimney growth, and is therefore controlled by its distribution in precipitating sulphides. Bulk Ag content of subsamples from a black smoker is accounted for by the Ag in chalcopyrite, pyrite, marcasite and ZnS; galena has the highest Ag (up to 0.95 wt.%), but is only present in trace amounts. Bulk chemical analyses of 33 chimney samples gave Ag up to 206 ppm; the Ag content correlates with Pb, S, Sb, Cd, Mn and Au in chimneys from both areas, and is also positively correlated with the morphological maturity of the containing structures, being highest in basal mounds and lowest in immature anhydrite-rich chimneys. Silver is thus continuously enriched in seafloor deposits during the lifetime of the hydrothermal system. [R.A.H.]
Subjects:Anhydrite; Black smokers; Bornite; Chalcopyrite; Chimneys; Covellite; Deposition; Electron probe data; Galena; Goethite; Hydrothermal conditions; Hydrothermal vents; Marcasite; Marine environment; Marine geology; Metal ores; Mid-ocean ridges; Mounds; Neutron activation analysis data; Ocean floors; Oxides; Pyrite; Pyrrhotite; Sampling; Silver ores; Sphalerite; Sulfates; Sulfides; Transport; Vents; Wurtzite; East Pacific; East Pacific Rise; Pacific Ocean; Isocubanite
Coordinates:N205000 N205400 W1090100 W1090900
Abstract Numbers:97M/1688
Record ID:2000027828
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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