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 TectonicBackground of the Huangyanggou Diorite Porphyrite,Tianshuihai, West Kunlun

The Huangyanggou diorite porphyrite pluton intruded inthe limestone of the Late Jurassic Hongqilafu Formation, which is located inTianshuihai-Kalakunlun Terrane. In order to determine its formation age andreveal the petrogenesis and tectonic background, LA-ICP-MS zircon U-Pbgeochronology and whole-rock geochemical analysis of Huangyanggou dioriteporphyry were carried out.The zircon U-Pb age of the pluton is 159.9 Ma, whichis formed in a post-collisional extensional environment. The magma source ischaracterized by mantle source, with the assimilation and mixing of crustalmaterials, which indicated the formation conditions were low pressure, strongoxidation environment and experienced intermediate differentiation. The plutonis 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 inlarge ionic lithophile elements (K, Rb, Ba, Th, U) and depleted high fieldstrength (Nb, Ta, Zr, Hf) elements, with a weak Eu negative anomaly (δEu mean 0.97). Through thecomparative study of the regional magmatic activities, the Huangyanggou plutonhas a strong affinity with the Pa’a I-type granite in the Geji area of theBangonghu-Nujiang suture zone, and is consistent with the formation ages of themagmatic rocks exposed in this suture zone. It indicates that the Huangyanggoudiorite porphyrite in the south of the Tianshuihai terrane is a magmaticresponse to the southward subduction of the Meso-Neo-Tethys Ocean in thenorthern Bangonghu-Nujiang suture zone.