Gold mineralization of the Huangjindong gold deposit in the Jiangnan Orogen, South China: Constraints from fluid inclusions and LA-ICP-MS analysis of pyrite and arsenopyrite
Hangfei Ge , Yi Liang , Guogang Wang , Chunbo Zhou , Qiuming Pei , Xingyu Jiao , Haonan Huang
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引用次数: 0
Abstract
The Huangjindong gold deposit (∼80 t Au @ 5 g/t) is located in the middle segment of the Jiangnan Orogenic Belt, South China. Mineralization of the deposit is mainly controlled by the NE-trending faults and a series of EW-NWW-trending inverted folds, which are dominated by auriferous quartz veins, altered slates and breccias. As the gold-bearing minerals, pyrite and arsenopyrite are both classified into two generations (Py1, Py2, Apy-a and Apy-b). The mineralization comprises three stages, Py1 + quartz + sericite (stage I), Py2 + arsenopyrite + gold + galena + sphalerite + chalcopyrite + tetrahedrite + quartz (stage II), and quartz + chlorite + calcite (stage III). To understand the characteristics of gold mineralization and the ore-forming conditions, we conducted comprehensive studies of the fluid inclusions, EPMA, LA-ICP-MS and thermodynamic analyses. The microthermometric results reveal that the ore-forming fluids may have two temperature peaks at ∼180 °C and ∼280 °C. The EPMA results show that the fineness of the native gold ranges from 978 to 1000 (mean 995.9). The LA-ICP-MS analyses of fluid inclusions, pyrite and arsenopyrite formed at different stages reveal the distinct distributions of trace elements. Since the processed data from the LA-ICP-MS mapping analyses reveals that the Au/Ag values of Py2 (10–1000) and arsenopyrite (10–10,000) are higher than that of Py1 (0.1–100), we conducted thermodynamic calculations and plotted the 3D isopleth models for the gold solubility and the Au/Ag ratio. The results of this study suggest that gold mineralization mainly occurs in stage II with higher Au/Ag ratios and higher temperatures, and the decreased sulfur concentration might have caused large-scale gold precipitation.
期刊介绍:
Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.