Hydrothermal Mineralization in the Guaymas Basin, Gulf of California
Jan M. Peter, Steven D. Scott, 1991. "Hydrothermal Mineralization in the Guaymas Basin, Gulf of California", The Gulf and Peninsular Province of the Californias, J. Paul Dauphin, Bernd R. T. Simoneit
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Hydrothermal precipitates occur in both the northern and southern troughs of the Guaymas Basin in the Gulf of California. A talc-pyrrhotite deposit in the northern trough is interpreted to have formed at temperatures around 280°C. Numerous hydrothermal spires and mounds composed of carbonates, sulfates, silicates, metal (Fe, Zn, Cu-Fe, Pb) sulfides, and iron oxides are found at a water depth of 2000 m in the southern trough. Some structures are actively venting hydrothermal fluid at temperatures of more than 300°C. Predominant minerals include calcite, barite, amorphous silica, stevensite, pyrrhotite, and marcasite. Mineral assemblages present and the compositions of the individual minerals can best be explained by the mixing of end-member hydrothermal fluid with ambient seawater. Most minerals are precipitated at the vent site largely in response to decreasing temperature induced by mixing.