Composición geoquímica y mineralógica de los depósitos hidrotermales de la dorsal del pacifico mexicano (21°N) y la cuenca de Guaymas

Abstract

Geochemical and mineralogical compositions are discussed for 24 samples collected by the submersible AL VIN, from the 21 0N Mexican Pacific Rise and the Southern trough of Guaymas Basin, Gulf of California. The hydrothermal sulfidc type deposits at 21 0N are primarily Cu, Zn and Fe sulfides (sphalerite, pyrite, marcasite, cha\copyrite and wurtzite) with less amounts of Ca and Ba sulfates (anhydrite and barite) and other minor minerals. The metal composition of thc interior of active chimncys-walI is: Cu, 29.30/0; Zn, 0.7%; Fe, 22.5°10; and the exterior: Cu, 2.5%; Zn, 10.3%; and Fe, 12.7%. The inactivc chimncys showed the following levels Cu, 1.8%; Zn, 7.3%; Fe, 2.9%;Ca, 25.3%;Mg, 5.5%; while thc mounds, Cu, 0.4%; Zn, 6.0%; Fe, 33.5%. In contrast with 21 0N Rise, the hydrothermal deposits of the Guaymas Basin have different sulfide mineralogy, as reflected in the geochemical composition; thc pyrrhotitc was the most abundant sulfide with less Zn, Cu-Fe sulfides.