Hydrothermal processes at the Axi epithermal Au deposit, western Tianshan: Insights from geochemical effects of alteration, mineralization and trace elements in pyrite
Hydrothermal processes at the Axi epithermal Au deposit, western Tianshan: Insights from geochemical effects of alteration, mineralization and trace elements in pyrite
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西天山阿溪浅成热液金矿热液过程：黄铁矿蚀变、成矿和微量元素地球化学效应的见解
DOI：
10.1016/j.oregeorev.2018.09.009
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发表时间：
2018-11
影响因子：
3.3
通讯作者：
Qing-Hua Shang
中科院分区：
文献类型：
--
作者：
Zhan-Kun Liu;Xian-Cheng Mao;Hao Deng;Bin Li;Shu-Gen Zhang;Jian-Qing Lai;Richard C Bayless;Min Pan;Long-Jiao Li;Qing-Hua Shang
作为西天山图拉苏盆地最大的低硫化（LS）浅成热液矿床，阿西金矿床的地质历史知之甚少。目前尚不清楚热液矿化是在单一事件中还是在多个事件中发生的。本文的新资料包括整个岩石地球化学和热液蚀变的质量变化计算。对黄铁矿进行了LA-ICP-MS微量元素分析，建立了黄铁矿综合成矿模式。阿西矿床黄铁矿-绢云母-石英蚀变的特征是斜长石和基性斑晶被绢云母、石英、黄铁矿（py1）、蒙脱石和伊利石取代，表明成矿早期处于微酸性和还原性条件。中等半面体黄铁矿晶体（py1）具有多孔结构，通常位于富铁矿物（如角闪石）附近，具有Co-Ni- mn富集特征，Co/Ni和Cu/As的比值较高（平均比值为1.114）和0.655)，表明岩浆热液系统中存在优先硫化反应。硅化岩中石英 ± 方解石 ± 黄铁矿 ± 黄铁矿组合及轻稀土的强迁移性均反映了矿石后期形成的微酸性富氯化物溶液相。具有碎裂结构的粗自体黄铁矿（py2）和中自体黄铁矿（py3）具有混合热液成因，分别在金-黄铁矿-石英和金-多硫化物-石英阶段与石英沉积。Py2和py3的Cu/As比值（平均值分别为0.103和0.088）明显低于py1，表明成矿后期有大气流体输入。3代黄铁矿，尤其是py3，均具有显著的晶格束缚金含量（py1: 0.01 ~ 38.86 ppm，中值1.51 ppm; py2: 0.03 ~ 234.37 ppm，中值1.21 ppm; py3: 3.31 ~ 231.56 ppm，中值42.72 ppm）。金的沉淀与含金的氯（Au(Cl)2−）和二硫化物配合物（Au(HS)2−）的硫化和沸腾失稳有关。这些特征表明，阿西浅成热液矿床是两期成矿作用的结果。
As the largest low-sulfidation (LS) epithermal deposit in the Tulasu basin, western Tianshan, NW China, the Axi gold deposit has a poorly understood geologic history. It is not clear whether hydrothermal mineralization occurred during a single event or multiple events. In this paper, new data consist of whole rock geochemistry and mass-change calculations for hydrothermal alteration. LA-ICP-MS trace element analysis of pyrite was conducted in order to develop a comprehensive metallogenic model. The pyrite-sericite-quartz alteration at the Axi deposit is characterized by replacement of plagioclase and mafic phenocrysts by sericite, quartz, pyrite (py1), smectite, and illite, indicating slightly acidic and reducing conditions during the early ore stage. Medium subhedral pyrite crystals (py1) with porous texture are typically sited adjacent to iron-rich minerals (e.g., hornblende) and are characterized by Co-Ni-Mn enrichment with high ratios of Co/Ni (avg. 1.114) and Cu/As (avg. 0.655), implying preferential sulfidation reactions in magmatic hydrothermal systems. The quartz ± calcite ± pyrite ± adularia assemblages in silicified rocks and the strong mobility of LREE both reflect a slightly acidic chloride-rich solution phase during the later ore stage. Coarse anhedral pyrites with cataclastic texture (py2) and medium euhedral pyrites (py3) have a mixed hydrothermal origin and were deposited with quartz during Au-pyrite-quartz and Au-polysulfide-quartz stages, respectively. Py2 and py3 both have significantly lower Cu/As ratios (avg. 0.103 and avg. 0.088, respectively) than py1, indicating the input of meteoric fluid during the later ore stage. The three generations of pyrite, especially py3, have significant lattice-bound gold contents (py1: 0.01–38.86 ppm, median 1.51 ppm; py2: 0.03–234.37 ppm, median 1.21 ppm; py3: 3.31–231.56 ppm, median 42.72 ppm). Gold precipitation is associated with the destabilization of Au-bearing chlorine (Au(Cl)2−) and bisulfide complexes (Au(HS)2−) via sulfidation and fluid boiling. All of these characteristics indicate the Axi epithermal deposit is the result of two stages of mineralization.
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DOI：
--
发表时间：
1999
期刊：
Journal of Precious Metallic Geology
影响因子：
--
作者：
Wu Rui
通讯作者：
Wu Rui
DOI：
--
发表时间：
2002
期刊：
Geology and Prospecting
影响因子：
--
作者：
Zhang Gui-lin
通讯作者：
Zhang Gui-lin
影响因子：
5.8
作者：
D. Cooke;C. Deyell;P. Waters;Rene I. Gonzales;K. Zaw
通讯作者：
D. Cooke;C. Deyell;P. Waters;Rene I. Gonzales;K. Zaw
影响因子：
3
作者：
G. Tang;Qiang Wang;D. Wyman;M. Sun;Zhenhua Zhao;Zi-qi Jiang
通讯作者：
G. Tang;Qiang Wang;D. Wyman;M. Sun;Zhenhua Zhao;Zi-qi Jiang
影响因子：
5.8
作者：
E. Ronacher;J. Richards;M. Reed;C. J. Bray;E. Spooner;P. Adams
通讯作者：
E. Ronacher;J. Richards;M. Reed;C. J. Bray;E. Spooner;P. Adams