投稿时间：2021-02-25
修订日期：2021-08-20
网络发布日期：2021-10-22
中文摘要:特提斯喜马拉雅发育与造山带平行的片麻岩穹窿构造带，其与喜马拉雅金锑、铅锌多金属、锡钨铍多金属矿具有密切的时空关系。西藏扎西康铅锌多金属矿集区是喜马拉雅造山带最具特色的矿集区，集中产出20余处不同规模的金锑、铅锌、锡钨铍多金属矿床。矿集区内矿床围绕错那洞穹窿呈规律性分布，体现为从穹窿核部向外依次分布铍钨锡稀有金属矿→铅锌多金属矿→金锑矿。这些矿床分布特征与区域1：5万区域水系沉积物分析结果一致，从错那洞片麻岩穹窿核部-淡色花岗岩内部及其接触带到外围表现为W、Sn、Bi、Rb等高温元素→Pb、Zn、Ag、Sb等中温元素→Au、Sb、Ag、Hg、As等中低温元素异常组合。错那洞穹窿形成于中新世，该时期伴有大量的淡色花岗岩（23~14 Ma）侵位，此时也迎来了扎西康矿集区"成矿大爆发"（21~12 Ma）。矿集区内典型矿床的H-O同位素组成表明，各矿床均显示有岩浆热液不同程度的贡献。矿石矿物的Pb同位素特征表明，锡钨铍来自于淡色花岗岩，铅锌具有多源性，既可以来自于淡色花岗岩，亦可以来自于古老基底物质，而金锑主要来自于与幔源作用有关的基性岩及玄武岩。结合矿集区内矿床的时空分布特征、流体及物质来源特点，文章认为扎西康矿集区内多金属矿床形成是喜马拉雅带成穹作用引发的构造-岩浆-成矿事件，构成了受穹窿控制的金锑-铅锌-锡钨铍稀有多金属成矿系统。自中新世以来，喜马拉雅造山带处于伸展活动时期，发育多期次的淡色花岗岩深熔作用，并在错那洞侵位形成片麻岩穹窿。深熔淡色花岗岩具有较高的演化程度，演化后期出溶富集Be-W-Sn-Rb的岩浆流体。在岩浆侵位过程引发的高异常地热梯度作用下，岩浆流体向外扩散，在岩浆顶部形成伟晶岩型铍铷稀有金属矿，在岩体边部与大理岩交代形成矽卡岩型铍稀有多金属矿，在错那洞穹窿拆离断裂及近南北向张性断裂中形成锡石-硫化物脉型锡多金属矿。岩浆流体在向外渗流过程中，萃取各类地质体中的成矿元素，并与大气降水、地热循环水不同程度的混合，在外围的张扭性断裂中形成铅锌，在温度更低的压扭性断裂中形成金（锑）矿。
中文关键词:地质学 穹窿成矿作用 扎西康矿集区 构造-岩浆-热液成矿系统 喜马拉造山带
Abstract:The Tethys Himalaya Gneiss Dome (THGD) is parallel to the orogenic belt, which is closely related to the gold, antimony, lead-zinc and tin-tungsten-beryllium polymetallic deposits in the Himalaya orogenic belt. The Zhaxikang lead-zinc polymetallic Ore concentration Area (ZOA) in southern Tibet is the most famous ore-concentrating area in the Himalayan orogenic belt, more than dozens of gold-anitimony, lead-zinc and beryllium-tungsten-tin deposits with different tonnages were formed within it. The ore deposits in the ZOA are concentrated around the Cuonadong gneiss dome in the central part of this area, and occurred in the sequence of berylliumtungsten-tin rare metal ores → lead-zinc polymetallic ores → gold and/or antimony ores from the core of the dome to the rim, which are consistent with the 1:50 000 scale regional stream sediment geochemical anomaly represented by a zonation of high temperature elements (W, Sn, Bi, Rb) in the core of the dome→ medium temperature elements (Pb, Zn, Ag, Sb) in the outer contact zone of granite → medium and low temperature elements (Au, Sb, Ag, Hg, As) in the peripheral country rocks. The Cuonadong Dome was mainly formed in Miocene, during which a number of leucogranites (23~14 Ma) were emplaced, and the "metallogenic explosion" (21~12 Ma) of ZOA took place during this time. The H-O isotopes indicate that the ore-forming fluids within ZOA have contribution of magmatic hydrothermal fluid in different degrees. The Pb isotopes indicate that Be-W-Sn is derived from leucogranite, and Pb-Zn has multi-sources, which could come from leucogranite and ancient metamorphic basement rocks, while the Au(Sb) is mainly derived from mafic dikes and basalts related to the mantle or lower crust. Based on analysis on the spatial and temporal distribution, fluid and material source of typical deposits, it is considered that the formation of polymetallic deposits in ZOA is a tectonic-magmatic-metallogenic event triggered by the doming in the Himalayan belt, which constitutes an doming controlled Au-Sb-Pb-Zn-W-Be polymetallic metallogenic system. The Himalayan orogenic belt has been in an extensional period since the Miocene, and multiple periods of leucogranites anatexis have been developed in this area that formed gneisses dome centered at Cuonadong. The anatexis intrusions are highly evolved leucogranites, with exsolution of Be-W-Sn-Rb bearing magmatic fluid in late magmatic evolution. With the high geothermal gradient caused by the magma emplacement, the magmatic fluid diffused outward, forming pegmatite-type Be-Rb rare-metal deposits at the top of the magma, and forming skarn-type Be rare metal deposits when metasomated with marble in the contact zone of the granite, and also forming cassiterite-sulfide vein type tin polymetallic ores in the Cuonadong detachment faults and the near north-south striking extensional fault systems. In the process of flowing outward, the ore-forming elements in various geological bodies are extracted, and mixed with varying degrees of meteoric water and geothermal water, forming Pb-Zn deposits in the peripheral extensional fractures, and Au-Sb ores at a lower temperature.
keywords:geology metallogenesis in dome Zhaxikang ore-concentration area tectonic-magmatic-hydrothermal system Himalaya orogenic belt
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基金项目:本文得到国家自然科学基金（编号：91955208）、科技部国家重点研发计划（编号：2019YFC0605201、2018YFC0604103）和西藏山南地区铍锡多金属矿调查评价项目（编号：DD20190147）共同资助
引用文本：
梁维,李光明,巴桑元旦,张林奎,付建刚,黄勇,张志,王艺云,曹华文.2021.喜马拉雅带片麻岩穹窿成矿作用——以扎西康矿集区错那洞穹窿为例[J].矿床地质,40(5):932~948LIANG Wei,LI GuangMing,BASANG Yuandan,ZHANG LinKui,FU JianGang,HUANG Yong,ZHANG Zhi,WANG YiYun,CAO HuaWen.2021.Metallogenesis of Himalaya gneiss dome: An example from Cuonadong gneiss dome in Zhaxikang ore concentration area[J].Mineral Deposits40(5):932~948
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