Ag-Au-Te and pyrophyllite-dumortierite in alteration systems, southernmost korea

摘要

Cretaceous volcanic rocks at the far southern end of the Korean Peninsula contain numerous areas of acid sulfate alteration. They are also intruded by granodiorite stocks. Pyrophyllite, quarried here for centuries, is accompanied by varying amounts of dumortierite, diaspore, alunite, dickite, sericite, pyrite, and anomalous traces of base and precious metals. Nearby, little-altered andesite and argillaceous sandstone host jasperiodal quartz veins containing telluride-rich precious and base metal sulfide ores accompanied by clay and carbonate alteration. Manifestations of hot spring discharge are lacking throughout the area. The two mineral assemblages, characterized as high and low sulfidation, appear unrelated. New age dates suggest volcanism, intrusion, and phyllic alteration were nearly contemporaneous. A shallow hydrothermal system, perhaps during pluton emplacement, caused th widespread local acid sulfate alteration zones. Supersaturation of silica probably led to the generation of pyrophyllite by low temperature, low potassium solutions.