Isotopic geochemistry of the Sawayaerdun orogenic-type gold deposit, Tianshan, northwest China: Implications for ore genesis and mineral exploration
Isotopic geochemistry of the Sawayaerdun orogenic-type gold deposit, Tianshan, northwest China: Implications for ore genesis and mineral exploration
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DOI：
10.1016/j.chemgeo.2012.03.026
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发表时间：
2012-06
期刊：
影响因子：
3.9
通讯作者：
Huayong Chen;Yan‐jing Chen;M. Baker
中科院分区：
文献类型：
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作者：
Huayong Chen;Yan‐jing Chen;M. Baker
萨瓦亚尔敦金存款矿床是中国天山成矿带中最大的穆龙套型金存款矿床。萨瓦亚尔敦金矿化发生在与三个主要热液事件有关的石英脉中：早期，贫瘠的石英脉阶段，中期含黄铁矿的矿化石英脉和晚期碳酸盐（石英）脉。萨瓦亚尔敦金存款矿床石英和硫化物同位素组成虽有一定差异，但与其他造山型金矿床的同位素组成基本一致。早期石英中捕获的流体的δ 18 O范围为13.6‰至15.4‰，δD范围为−48‰至−75‰，δ 13 C范围为0.5‰至4.2‰，δ 30 Si范围为−0.2‰至0‰。相反，捕集在中期石英中的流体的同位素组成的δ 18 O值为6.7‰至14.7‰，δD值为−56‰至−110‰，δ 13 C值为0.4‰至10.1‰，δ 30 Si值为−0.3‰至0‰。成岩和热液黄铁矿具有相似的硫（-1.8 ‰至0.9‰）和铅同位素值，与寄主岩石成分有关。早期富18 O和13 C流体可能来自于沉积容矿岩在深部的变质脱碳酸作用，导致早期贫石英脉的沉淀。在中期阶段，区域压力和温度状况的降低可能导致外部流体进入成矿系统。这些与围岩同位素特征相似的、普遍富含34 S和放射成因Pb的外来流体与原始成矿流体混合，产生了广泛的金属沉淀。方解石脉捕获的晚期流体同位素组成与大气降水相似，表明萨瓦亚尔敦热液循环的停止发生在这个时候。稳定同位素和铅同位素所描述的成矿模式也与萨瓦亚尔敦的流体包裹体研究相一致。Sawayaerdun矿化的发展与流体混合密切相关，已确定的含矿带流体的同位素特征证明了这一点。萨瓦亚尔敦其他异常带的同位素组成与矿化带相似，表明进一步找矿的潜力很大。
The Sawayaerdun gold deposit is hosted by Carbonaceous metasediments and is considered to be the largest Muruntau-type gold deposit in the Chinese Tianshan metallogenic belt. Gold mineralization at Sawayaerdun occurs in quartz veins associated with three major hydrothermal events: an early, barren quartz vein stage, middle stage mineralized quartz veins with pyrite and late carbonate (-quartz) veins. The isotopic compositions of quartz and sulfides from the Sawayaerdun gold deposit show some variation but are generally comparable to those of other orogenic-type gold deposits. Fluids trapped in early-stage quartz have a δ18O range of 13.6‰ to 15.4‰, δD of −48‰ to −75‰, δ13C of 0.5‰ to 4.2‰ and δ30Si of −0.2‰ to 0‰. In contrast, isotopic compositions of fluids trapped in middle-stage quartz have δ18O values of 6.7‰ to 14.7‰, δD of −56‰ to −110‰, δ13C of 0.4‰ to 10.1‰ and δ30Si of −0.3‰ to 0‰. Diagenetic and hydrothermal pyrite have similar sulfur (−1.8‰ to 0.9‰) and Pb isotopic values that are associated with host rock compositions. The early-stage,18O and13C-rich fluids are probably derived from metamorphic decarbonation of the sedimentary host rock at depth, leading to the precipitation of early barren quartz veins. In the middle stage, a decrease in the regional pressure and temperature regime could have resulted in the incorporation of external fluids into the ore-forming system. These external fluids with isotopic signatures similar to that of the host rock and generally rich in34S and radiogenic Pb mixed with original ore-forming fluids to generate extensive metal precipitation. Late-stage fluids trapped by calcite veins show isotopic compositions similar to meteoric water, indicating the cessation of hydrothermal fluid circulation at Sawayaerdun occurred at this time. The metallogenetic model illustrated by stable and Pb isotopes is also consistent with fluid inclusion studies in Sawayaerdun. The development of mineralization at Sawayaerdun is strongly linked to fluid mixing, as witnessed by the isotopic signatures of fluids from identified ore-bearing zones. The isotopic compositions of other anomalous zones at Sawayaerdun are similar to those of the mineralized zones, suggesting a high potential for further exploration.