青海祁漫塔格虎头崖多金属矿区花岗斑岩地球化学、年代学特征及其地质意义

青海祁漫塔格地区侵入岩分布广泛，主要沿区域主构造线北西西向展布。虎头崖多金属矿区内的花岗斑岩产于东西向与北西西向构造结合部位，呈岩枝状产出。斑晶的主要成分为石英、斜长石、钾长石、黑云母及普通角闪石。对该花岗斑岩进行了全岩主量、微量、稀土元素分析和LA-ICP-MS锆石U-Pb定年研究，同时对虎头崖矿区内的典型花岗岩进行了详细的岩石地球化学特征及岩相学研究。花岗斑岩的里特曼指数δ为1.56~2.16，具有高硅、高钾、低铝的特征，属高钾钙碱性系列，准铝质-弱过铝质花岗岩。微量元素具有富集大离子亲石元素，相对亏损高场强元素，Ba、Sr、Nb负异常特征。稀土元素配分曲线为略右倾的海鸥型，Eu负异常特征明显，具有A₂亚型花岗岩的特征。花岗岩与花岗斑岩具有一致的地球化学特征、成因类型、岩浆源区、形成环境。因此，该花岗斑岩与花岗岩构成的酸性侵入体为同一岩浆源区，形成于东昆仑造山带后碰撞伸展环境中的花岗质杂岩体。LA-ICP-MS锆石U-Pb定年获得（232.7±1.8）Ma（MSWD=1.3，n=22）的岩体侵位年龄，表明东昆仑在印支期进入陆内造山末期，大规模的岩浆事件引起祁漫塔格地区印支期成矿作用。

Geochronology,Geochemistry and Geological Significance of Granite Porphyry in Hutouya Polymetallic Deposit,Qimantage Area,Qinghai Province

Magmatic intrusions widely distributed in Qimantage area of Qinghai Province, are mostly located around NW-extending regional structure. The granite porphyry in Hutouya polymetallic deposit occurred in the joint position of the E-W extending and northwest-extending structures. Phenocrysts mainly include quartz, plagioclase, K-feldspar, biotite and amphibole.This paper reported major, trace, rare earth elements composition and LA-ICP-MS zircon U-Pb dating result about the granite porphyry. Simultaneously, geochemistry and petrography of the ore-hosting rock in the Hutouya polymetallic deposit are studied. The granite porphyry is characterized by high silicon, high potassium and low aluminum, and belongs to the high-K calc-alkaline series metaluminous-peraluminous granite. Trace elements are enriched in LILEs, depleted in HFSEs, and with Ba, Sr, Nb negative anomaly characteristics. In the REE partition diagram, the porphyry is in seagull form, having Eu negative anomaly character. The granite porphyry can be classified into the A₂-subtype granite. The granite in the Hutouya ore district has the common geochemical charactersistics, genetic type, magma source and forming environment with the granite porphyry, which indicates that they formed the granitic complex. The complex was originated from the common magma source and emplaced in the extensional environment occurring after the post-collision transitional period from compression to extension of East Kunlun orogenic belt. LA-ICP-MS Zircon U-Pb dating of the granite yielded (232.7±1.8) Ma(MSWD=1.3, n=22), representing the fact that the East Kunlun was in the end stage of the intracontinental orogeny during Indosinian. Large-scale magmatism led to the Indosinian mineralization in the Qimantage area.