BIOGENIC VS GEOCHEMICAL PRECIPITATION OF MINERALS IN THE SUBMARINE HYDROTHERMAL VENTS OF PUNTA MIT A, MEXICO

摘要

The submarine hydrothermal vents located in the vicinity of Punta Mita contain abundant deposition of calcite, pyrite. Also present are barite, carbonate hydroxyl-apatite, cinnabar and Tl-sulfide. Textures indicate direct deposition for calcite and pyrite; however, pyrite also replaces magnetite in the host rock. Thermal water was filtered and microscopic analysis of the particles from the filters shows that the shape of the crystals varies from euhedral crystals of pyrite to globular aggregates that may be interpreted as a mixture of chemical and biogenic precipitation. Isotopic signature of sulfur in pyrite and carbon in calcite indicates that biogenic deposition is an important phenomenon in this hydrothermal system.