东昆仑它温查汉西花岗闪长斑岩年代学、岩石学、地球化学特征及其成矿意义

Chronological, petrologic and geochemical characteristics of Tawenchahanxi granitic diorite porphyry in East Kunlun Mountains and its metallogenic significance

它温查汉西铁多金属矿床是东昆仑祁漫塔格成矿带新发现的又一典型矽卡岩型矿床。利用LA-ICP-MS锆石U-Pb定年方法,获得矿区主要成矿岩体花岗闪长斑岩的成岩年龄为236.0±2.3Ma,该结果与前人利用^(40)Ar-^(39)Ar法获得的矽卡岩型磁铁矿矿石中白云母229.9±3.5Ma的等时线年龄一致。花岗闪长斑岩为过铝质高钾钙碱性系列,成因类型属于Ⅰ型;微量元素配分型式表现为轻稀土元素和高场强元素富集、重稀土元素和大离子亲石元素亏损、中等负Eu异常的特征。花岗闪长斑岩形成于晚古生代—早中生代构造-岩浆旋回的碰撞-后碰撞阶段,与区域上大规模的幔源岩浆底侵及其与壳源岩浆的混合作用有关。

The Tawenchahanxi Fe-polymetallic deposit is another typical skarn type deposit newly discovered in the Qimantag metallogenic belt of East Kunlun Mountains. Using LA-ICP-MS zircon U-Pb isotope dating, the authors obtained the petrogenetic age of the granitic diorite porphyry(236.0±2.3Ma.) which is the main ore-forming rock mass in the mine. The result is in agreement with previous isochron age of 229.9±3.5Ma of the muscovite separated from skarn magnetite ore by the ^(40)Ar-^(39)Ar incremental heating method. Petrologic and geochemical data indicates that it is a peraluminous granite and belongs to the Ⅰ type high K calc-alkaline series, enriched in LREE and HFSE but depleted in HREE and LILE. The rare earth patterns of rocks/chondrite show medium negative Eu anomalies. In addition, the diorite porphyry might have been formed at the collision-post collision stage of Late Paleozoic to Early Mesozoic tectono-magmatic cycle, which was also related to regional large-scale mantle magma underplating and crust-mantle magma mixing.