投稿时间：2021-08-13
修订日期：2021-12-16
网络发布日期：2022-03-17
中文摘要:阿斯哈金矿床是青海东昆仑造山带东段金矿床的典型代表。金矿体主要赋存于闪长岩和花岗闪长岩体的构造破碎带内,受NNE向和NNW向-NW向断裂构造控制。与金矿化密切相关的蚀变类型为黄铁矿化、硅化、绢云母化和黄铜矿化。矿石矿物主要为黄铁矿,其次是黄铜矿、方铅矿、毒砂、自然金和银金矿。据矿脉穿插关系、矿石矿物共生组合和结构构造特征,将成矿期划分为3个阶段:石英-黄铁矿-毒砂阶段(Ⅰ)、石英-多金属硫化物阶段(Ⅱ)、和石英-碳酸盐阶段(Ⅲ),其中Ⅱ阶段为主成矿阶段。前人研究表明黄铁矿的微量(含稀土)元素含量可以反映成矿流体与成矿物质来源的特征,本次采用电感耦合等离子质谱仪(ICP-MS)技术对阿斯哈金矿主成矿期的主要载金矿物黄铁矿进行研究。ICP-MS测试结果显示:黄铁矿相对富集少量高场强元素(如Y、U、Zr、Hf)外,其他元素均有不同程度的亏损,其Hf/Sm、Th/La和Nb/La比值(除个别样品外)普遍<1,表明矿床成矿流体可能是以富Cl的成矿热液为主。黄铁矿Co/Ni比值(1.39~6.61,平均为2.57)显示矿床为热液成因。黄铁矿Y/Ho比值(26.10~35.76,平均为30.57)与现代海水及海底热液明显不同,略较赋矿围岩闪长岩和花岗斑岩的Y/Ho比值(26.97~29.25,平均为28.12)范围宽,暗示除赋矿围岩外,可能还有其它源区。阿斯哈金矿床含金黄铁矿稀土元素总量较低(ΣREE=4.83×10-6~64.30×10-6,平均为19.60×10-6),LREE/HREE比值平均为6.62,(La/Yb)N值平均为8.11,为轻稀土元素富集型,其配分与赋矿围岩闪长岩和花岗斑岩相似,而与矿区地层金水口群变质岩不同,暗示该矿床成矿物质来自赋矿围岩。Eu负异常明显(δEu=0.49~0.92,平均为0.68),Ce异常不显著(δCe=0.73~1.00,平均为1.02),与赋矿围岩相似,进一步表明该矿床与中酸性围岩的内在成因关系。综合研究认为,阿斯哈金矿床属于与中酸性岩浆作用有关的浅成热液脉状型金矿床,并可能受到造山作用影响。
Abstract:The Asiha gold deposit is a typical representative of the gold deposit in the eastern section of the East Kunlun orogenic belt from Qinghai Province. The orebodies mainly occur in the structural fracture zone of diorite and granodiorite, and are controlled by NNE-trending and NNW-NW-trending fault structures. Alteration types closely related to gold mineralization includes pyritization, silicification, sericitization and chalcopyrite. The ore minerals are mainly pyrite, followed by chalcopyrite, galena, arsenopyrite, native gold and electrum. According to the interspersed relationship of ore veins, mineral association and structural characteristics, the mineralization stages are divided into the quartz-pyrite-arsenopyrite stage(Ⅰ), the quartz-polysulfide stage(Ⅱ) and the quartz-carbonate stage(Ⅲ). The stage Ⅱ is the main ore-forming stage. Previous studies had verified that characteristics of oreforming fluid can be reflected by trace elements(including REE) patterns contained in pyrite minerals. Trace element compositions of pyrites from the Asiha gold deposit was measured by ICP-MS in our study. ICP-MS test result shows that all elements in the pyrites have different extent depleted except the high field-strength element(HFSE) such as Y, U, Zr, Hf and its Hf/Sm, Th/La and Nb/La values of pyrite are all less than 1 except for individual samples, indicating the ore-forming fluid may be dominated by Cl-enriched. The Co/Ni ratios of pyrite(1.39~6.61, average 2.57) indicates that the deposit is hydrothermal origin. The Y/Ho ratios of pyrite(26.10~35.76, average 30.57) are significantly different from modern seawater and seafloor hydrothermal fluids. It is slightly wider than the Y/Ho ratios of host rock(26.97~29.25, average 28.12), suggesting that the ore-forming fluid might come from other source areas besides the host rocks. The total REE(ΣREE) of gold-bearing pyrite is relatively lower(ΣREE=4.83×10-6~64.30×10-6, average 19.60×10-6). The LREE/HREE ratio(6.62) and the(La/Yb)Nratio(8.11)indicate that the gold-bearing pyrite belongs to the LREE-rich type. REE characteristics are similar to those of host rocks(diorite and granitic-porphyry), suggesting that the ore-forming material of the deposit comes from the host rocks. Eu negative anomalies are obvious(δEu=0.49~0.92, average 0.68) but Ce anomalies are not significant(δCe=0.73~1.00, average 1.02). These characteristics are similar to host rocks, but differ from the metamorphic rocks of Jinshuikou Group in the mining area. It further indicates the inherent genetic relationship between the deposit and the intermediate-acid wall rocks. The Asiha gold deposit was epithermal gold deposit related to intermediate-acid magmatism, and might have affected by orogenic process.
keywords:geochemistry trace elements REE pyrite source of ore-forming material Asiha gold deposit East Kunlun of Qinghai Province
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基金项目:云南省地方本科高校基础研究联合专项资金项目(编号:202101BA070001-077); 云南省教育厅科学研究基金项目(编号:2021J0706); 昆明学院引进人才科研启动项目(编号:YJL2003)联合资助
引用文本：
岳维好,周家喜.2022.青海东昆仑阿斯哈金矿床含金黄铁矿微量元素地球化学特征及其地质意义[J].矿床地质,41(1):106~120YUE Wei-hao,ZHOU Jia-xi.2022.Trace element characteristics of gold-bearing pyrite from Asiha gold deposit in East Kunlun, Qinghai Province and their geological significance[J].Mineral Deposits41(1):106~120
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