西昆仑甜水海黄羊沟闪长玢岩年代学、地球化学特征及构造背景

黄羊沟闪长玢岩岩体侵位于甜水海—喀喇昆仑地块上侏罗统红其拉甫组灰岩地层中，为了厘定其形成时代，揭示岩石成因以及构造背景，对黄羊沟闪长玢岩岩体进行了LA-ICP-MS锆石U-Pb年代学及全岩地球化学分析研究。岩石地球化学研究结果表明，该岩体锆石U-Pb年龄为(159.9±1.4) Ma，形成于碰撞后伸展环境，源区具幔源特征，有地壳物质同化混染参与，形成条件为低压、强氧化环境，经历中等分异作用。该岩体具低硅（w(SiO₂)=56.11%~57.36%）、高钙（w(CaO)=4.29%~6.59%）、富碱（w(Na₂O+K₂O)=6.00%~7.96%）特征，属准铝质（A/NCK=0.79~0.95）岩石，且富集大离子亲石元素K、Rb、Ba、Th、U及亏损高场强元素Nb、Ta、Zr、Hf等，具微弱Eu负异常，δEu均值为0.97。通过区域岩浆活动对比研究，认为黄羊沟岩体与班—怒缝合带革吉地区的帕阿岩体I型花岗岩体具有很强的亲缘性，且与班—怒缝合带内的岩浆岩时限一致，表明甜水海地体南部的黄羊沟闪长玢岩是班—怒缝合带以北区域中、新特提斯洋向南俯冲的岩浆作用响应。

Geochronology,Geochemistry and Tectonic Background of the Huangyanggou Diorite Porphyrite,Tianshuihai, West Kunlun

The Huangyanggou diorite porphyrite pluton intruded in the limestone of the Late Jurassic Hongqilafu Formation, which is located in Tianshuihai-Kalakunlun Terrane. In order to determine its formation age and reveal the petrogenesis and tectonic background, LA-ICP-MS zircon U-Pb geochronology and whole-rock geochemical analysis of Huangyanggou diorite porphyry were carried out.The zircon U-Pb age of the pluton is 159.9 Ma, which is formed in a post-collisional extensional environment. The magma source is characterized by mantle source, with the assimilation and mixing of crustal materials, which indicated the formation conditions were low pressure, strong oxidation environment and experienced intermediate differentiation. The pluton is characterized by low silicon (w(SiO₂)=56.11%-57.36%), high calcium (w(CaO)=4.29%-6.59%), and alkali-rich (w(Na₂O+K₂O)=6.00%-7.96%), and belongs to quasi-aluminous (A/NCK=0.79-0.95) rocks. It is also enriched in large ionic lithophile elements (K, Rb, Ba, Th, U) and depleted high field strength (Nb, Ta, Zr, Hf) elements, with a weak Eu negative anomaly (δEu mean 0.97). Through the comparative study of the regional magmatic activities, the Huangyanggou pluton has a strong affinity with the Pa’a I-type granite in the Geji area of the Bangonghu-Nujiang suture zone, and is consistent with the formation ages of the magmatic rocks exposed in this suture zone. It indicates that the Huangyanggou diorite porphyrite in the south of the Tianshuihai terrane is a magmatic response to the southward subduction of the Meso-Neo-Tethys Ocean in the northern Bangonghu-Nujiang suture zone.