| 柴北缘-东昆仑地区的造山型金矿床 |
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| 引用本文：.2001.Orogenic Gold IDeposits in the North Qaidam and East Kunlun Orogen, West China[J].Mineral Deposits,20(2):137~146 |
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| 基金项目:国土资源部“九五”资源与环境科技攻关项目（95-02-005）和地质大调查项目（K1-1-3-1） |
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| 中文摘要:柴达木-东昆仑是中国西部秦祁昆褶皱山系的一部分，它的显生宙造山经历了加里东和晚华力西-印支两个旋回，并以多岛洋／裂陷槽、软磁撞和多旋回造山为特点。该区已发现多个造山型金矿床，它们具有相似的地质-地球化学特征。有两组成矿年龄：一是晚加里东期（相当于加里东造山晚期）；二是晚华力西-印支期（处于该造出旋回晚期）。前期为发生于中地壳顶部-上地壳底部的金矿化，后期则是形成于较浅层次(1.2~5.7 km)的金矿体侵位。自区域北部向南部，矿床元素组合由Au-As向Au-Sb转化，金成矿年龄由老变新，成矿深度相应变浅。研究认为，与碰撞有关的热事件以及逐步升高的地热增温率，驱动被加热的建造水和大气降水流体沿磁碰撞带和大型剪切带长距离地迁移、活动，并淋取围岩的成矿元素，形成含金流体。在进入到矿床或矿体构造后，由于构造性质转换，物理化学条件亦随之改变，含金流体沉淀，形成金矿体。这些金矿床形成于造山晚期，是造山作用的产物，后者为前者提供了空间、热-动力条件。 |
| 中文关键词:造山带 金矿床 柴北缘-东昆仑 |
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| Orogenic Gold IDeposits in the North Qaidam and East Kunlun Orogen, West China |
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| Abstract:The North Qaidam and East Kunlun orogen (NKO), located in northwest Qinghai Province and the northeastern margin of Qinghai-Tibet plateau, is a part of the Qingling-Qilian-Kunlun orogens of West China. Being a multiple orogen, it underwent Caledonian accretionary orogeny and intetnsive overprinting orogeny from Late Variscan to Early Mesozcxc, eharactenzed by archipelagic ocean/aulacogen, soft collision ancimulticyclicity. Tens of orogenic gold deposits and mineral occurrences were discovered in the NKO, in which thirteen orogenic gold deposits are reviewed in this paper. Occurring near the deep faults and/or collisional belts, they are located at convergent plate margins in accretionary and/or collisiona-orogeny and controlled by three-order structural systems. Although the wallrocks of these orogenic gold deposits vary in age and petrology, all of them were deformed and metamorphosed into greenschist facies. Their alterations are planar and nonzonational, and exhibit strong silicifiction, pyritization and sericitization in or nesr the orebody. The form, occurrence and size of the ore body are controlled by structures. According to ore types, the orogenic deposits in the NKO can be grouped into two subtypes, namely altered rock type in the shattered zone and quartz vein type. As a result of deposition from low-salinity H2O-NaCl-CO2±CH4±N2 fluids, both of them are characterized by high Au/Ag ratios, low base-metal content and varied As and Sb content, varying from Au-As in the northern part of the NKO to Au-Sb in the southern part of the NKO. Field observation and Ar-Ar isotope dating show that gold mineralizations have two groups of ages, viz. late Caledonian (425~400 Ma) and late Variscan-Indosinian (296~200 Ma) . From north to south, the depths of these orogenic gold deposits changed from the top of the middle crust and the bottom of the upper crust (15.4~7.3 km) to the upper crust (5.7~1.2 km) . Subduction-related thermal events and episodically rising geothermal gradients within the hydrated accretionary sequences initiated and drove long-distance hydrothermal fluid migration. The gold of the orogenic deposits was initially concentrated in shear zones at the lower part of the upper crust during late Caledonian subductional orogeny by the heated CH4-CO2-NaCl~H2O fluids, whereas the gold ores were mainly emplaced at the depth of 5.7~1.2 km during the Late Variscan to Early Mesozoic orogeny through the heated CO2-NaCl-H2O fluid mainly by granitic magmatism An initial subeconomic gold mineralization related to Late Caledonian ductile deformation resulted in the concentration of ore-forming elements in the large-size shear zone, while the structural-hydrothermal-mineralization during the Late Variscan to Early Mesozoic orogeny formed the commercial gold ores. |
| keywords:orogenic belt, gold deposits, North Qaidam and East Kunlun Mountains |
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