Abstract

Silicate, sulfide, and oxide assemblages indicate three stages of alteration and mineralization. During Stage 1, potassic alteration and zonal precipitation of sulfides occurred. Basic sills and dikes close to the ores underwent strong potassic alteration and slight sulfide mineralization, and were altered to skarn; metatuffites underwent potassic alteration and sulfide mineralization, and were altered to skarn; and dolomitic limestones underwent dedolomitization and sulfide mineralization and were altered to skarn. During Stage 2 the potassically altered tuffites were replaced by infiltrational-metasomatic amphibole skarns, which were subsequently replaced by pyroxene (-forsterite) skarns at temperatures of about 550 degrees C. The late Stage 2 pyroxene skarns are reaction skarns that are largely synkinematic with respect to boudinage of sulfide skarn layers and development of foliation in the marbles. Amphibole and pyroxene skarn relationships suggest a telescoping effect during the formation of the skarns. Silicate assemblages in metatuffites indicate metamorphic pressures of about 2.5 kb. During stage 3, retrogressive alterations, crystallization of pyrite, and remobilization of sulfides occurred largely syn- to postkinematically with respect to boudinage.--Modified journal abstract.

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