The Tiangongnile Cu-Au deposit located in the northern part of the Gangdise metallogenic belt is a skarn-type deposit closely related to granodiorite. Zircon ICP-MS U-Pb weighted average age of the granodiorite is 102.6±1.8 Ma, indicating that the deposit was formed during the Early Cretaceous period. Element geochemical data indicate that the diorite is characterized by high Al2O3, rich Na2O and low TiO2, thus belonging to metaluminous calc-alkaline series. Trace elements are characterized by enrichment of large ion lithophile elements(LILE) and depletion of high field strength elements (HFSE) and heavy rare earth elements, with Nb and Ta negative anomalies, suggesting that the diorite has geochemical features of island arc rock and its petrogenesis rnmay be related to magmatic activity induced by the subduction of Bangong Co-Nujiang River oceanic crust plates. In combination with regional tectonic evolution, it is held that the Tiangongnile Cu-Au deposit might have been formed in an island-arc environment before southward subduction and closure of Bangong Co-Nujiang River oceanic crust plates.%天富尼勒铜金矿床位于冈底斯成矿带北部,是与花岗闪长岩关系密切的矽卡岩型矿床.花岗闪长岩锆石ICP-MS U-Pb年龄加权平均值为102.6±1.8 Ma,指示该矿床形成于早白垩世.元素地球化学数据表明,花岗闪长岩具有高Al2O3,富Na2O,低TiO2等特点,属于准铝质、钙碱性岩石系列,微量元素富集大离子亲石元素(LILE),亏损高场强元素(HFSE)和重稀土元素,显示Nb和Ta的负异常,具有明显的岛弧型岩石的地球化学特征,岩石成因可能与班公湖-怒江洋壳板片俯冲所诱发的岩浆活动有关.结合区域构造演化,天宫尼勒铜金矿床形成于班公湖-怒江洋向南(即冈底斯地块)俯冲碰撞闭合之前的岛弧环境.
展开▼
