Abstract

Ag mineralization occurs as vein fillings and disseminations confined to areas of high fracture density and brecciation in the hanging wall of the Amethyst fault and vein. Paragenesis is divided into two main stages: 1 is a sulfide-poor assemblage characterized by rhodochrosite, quartz, barite, and an absence of silver; 2 represents a complex event made up of three substages. Disseminated mineralization in the study area appears to be related to stage 2. Analysis of fluid inclusions in stage 2 vein quartz showed that average homogenization temperatures and salinities decrease in a regular manner from lower to upper levels of the mine. Inclusions in stage 2 quartz from the lower mine levels had an average T h = 238 degrees C and an average salinity of 9.8 equivalent weight percent NaCl. Those in the uppermost level had an average T h = 170 degrees C and an average salinity of 6.5 equivalent weight percent NaCl. The rapid drop in temperature and dilution of hydrothermal solutions which was a result of mixing with near-surface waters caused the deposition of the high-grade Ag ores in the southern Amethyst vein system.--Modified journal abstract.

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