关键词: 水银洞金矿, 环带黄铁矿, 元素Mapping, 原位硫同位素, 岩浆活动

Abstract: The Shuiyindong gold deposit is a typical large Carlintype gold deposit. It is located in the “Golden Triangle” area crossing Yunnan, Guizhou and Guangxi provinces where arsenian pyrite and arsenopyrite are the significant Aucarrying minerals with invisible gold. In this study, Back Scattered Electron (BSE) imaging and highresolution MultiElement Mapping by NanoSIMS show that the pyrites usually have the zonal texture containing lower Au, As in the core and higher Au, As and Cu in the overgrowth rim. The trace element pattern implies that the ore fluid is Au, As, Curich during the pyrite overgrowth stage. In addition, highresolution NanoSIMS mapping reveals that the Aurich rim is composed of several unevenly distributed fine subzones, marked by the banded pattern of Au, As and Cu due to episodic hydrothermal fluid variation. Meanwhile, in situ sulfur isotopic analysis of pyrite shows that the δ34S values of cores and rims range from 1.3‰ to 6.5‰ and -3.5‰ to 7.4‰, respectively, focusing generally around 0‰. This result, combined with similar gold deposits around the world, indicates that sulfur is likely originated from the deep magmatic source contaminated by sedimentary sulfur. Finally, a magmatichydrothermal model is proposed for the Shuiyindong gold deposit. It suggests that the As and Aubearing acid magmatic fluid upwelled along the deep fault to fill or react with Ferich wall rocks, which led to the deposition of gold; in addition, the meteoric water might have been involved in the ore formation.

Key words: Shuiyindong gold deposit, zonal pyrites, Element Mapping, sulfur isotope, magmatic activities