Significance of native arsenic in the Baogutu gold deposit, western Junggar, Xinjiang, NW China

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2009,（10）
• 页码范围: 1744-1749
• 页数: 6页
• 语种: 英文
• DOI: 10.1007/s11434-009-0086-6

摘要

Native arsenic together with comb quartz and stibnite is found in the Baogutu gold deposit, western Junggar (Xinjiang), NW China. It is anhedral with various grain size (<0.001 to 2 mm), and contains 98 wt% to 98.7 wt% As. Micro-granular electrum, the main auriferous mineral in the Baogutu gold deposit,is commonly enclosed in or closely accompanied by native arsenic. Three ore-forming paragenetic stages could be identified. Native arsenic mainly formed at stage ⅠⅡ which is also the major stage for gold deposition. Mineral assemblage formed at this stage is native arsenic-stibnite-electrum-arseno-pyrite-miargyrite-freibergite-pyrrhotite-pyrite. Based on native arsenic and its coexisting minerals, the temperature (230 to 170℃), oxygen fugacity (Iog fO2 = -42--56.5) and sulfur fugacity (Iog/S2 = -13.3--16.6) of stage Ⅱ are estimated. From stage Ⅰ to stage ⅠⅡ, the temperature, sulfur fugacity and S<'2-> con-centration of hydrothermal fluid decrease obviously, whereas the As concentration increases. Coexis-tence with native arsenic of electrum and its contents of 0.5 wt%-1.3 wt% As suggest that As is im-portant to transport Au when S<'2-> concentration decrease in hydrothermal fluid. Crystallization of native arsenic induced the deposition of electrum and consequently the formation of the Baogutu gold deposit.