东昆仑哈日扎-那更康切尔银矿区花岗岩年代学、地球化学及岩石成因  

Geochronology,Geochemistry and Petrogenesis of the Harizha⁃Nagengkangqieer Granites in the East Kunlun Orogen

作　　者：马忠元 柴佳兴 张爱奎 燕正君 张金阳[2] Ma Zhongyuan;Chai Jiaxing;Zhang Aikui;Yan Zhengjun;Zhang Jinyang(The Third Geological Exploration Institute of Qinghai Province,Xining 810029,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]青海省第三地质勘查院,青海西宁810029 [2]中国地质大学资源学院,湖北武汉430074

出　　处：《地球科学》2024年第5期1778-1792,共15页Earth Science

基　　金：青海省第三地质勘查院自筹科研项目(No.SKYZC-2022-007);青海省“高端创新创业人才计划”项目《青藏高原北缘三叠纪斑岩铜多金属矿成矿作用研究》。

摘　　要：东昆仑东西部发育多处大型银矿床,但东昆仑古特提斯构造演化和银矿成矿构造背景争议很大,基于此,对东昆仑哈日扎-那更康切尔银矿区岩心样品花岗岩及花岗斑岩开展年代学与地球化学方面研究.LA-ICP-MS锆石U-Pb定年结果表明,哈日扎花岗岩年龄为255 Ma,哈日扎-那更康切尔花岗斑岩年龄在220 Ma到224 Ma.哈日扎晚二叠世花岗岩整体上体现高硅、富碱、贫钙及贫镁的特征,轻稀土元素富集,重稀土元素及Nb、Ta等高场强元素亏损,具有强烈的负Eu异常,Ga/Al比值和Zr+Nb+Ce+Y含量明显偏高,符合A型花岗岩的特点.由于岩石K_(2)O/Na_(2)O与FeO/MgO比值较高,可能来自地壳钙碱性I型花岗岩的部分熔融,形成于晚二叠世弧后伸展体制.晚三叠世花岗斑岩是银成矿期岩石,主量元素与晚二叠世花岗岩相似,体现钙碱性过铝质的特点,但稀土元素与微量元素含量远低于晚二叠世花岗岩.结合前人研究成果,晚三叠世花岗斑岩及成矿可能形成于后碰撞构造背景,花岗斑岩是岩浆强烈结晶分异的产物.Several large silver deposits occur in the East Kunlun Orogen but their tectonic setting and related Paleo-Tethyan evolution are highly debated.Geochronological and geochemical works on the granites and porphyritic granites in the Harizha-Nagengkangqieer silver deposits of the East Kunlun Orogen were made in this study.LA-ICP-MS zircon U-Pb dating shows that the Harizha granites were emplaced at 255 Ma and the porphyritic granites in both areas between 220 Ma and 224 Ma.Late Permian Harizha granites have high SiO2 and K_(2)O+Na_(2)O but low CaO and MgO contents with enriched light rare earth elements,depleted heavy rare earth elements and high field strength elements,negative Eu anomalies,high Ga/Al ratios and Zr+Nb+Ce+Y values,and thus are A-type.These rocks were generated by partial melting of crustal calc-alkaline I-type granitoids in a back-arc extensional setting because of their relatively high K_(2)O/Na_(2)O,Ga/Al,FeO/MgO ratios.The Late Triassic calc-alkaline,peraluminous porphyritic granites are related to silver mineralization with similar major elements but low contents of trace elements compared to the Late Permian granites,are thus the result of fractional crystallization in a post-collisional background according to this and numerous previous data.

关 键 词：东昆仑 哈日扎 那更康切尔 花岗岩 年代学 地球化学 

分 类 号：P581[天文地球—岩石学]