青海东昆仑哈西亚图矿区花岗闪长岩锆石U-Pb年龄与岩石地球化学特征

哈西亚图铁多金属矿位于东昆仑构造带,是区域较为典型的一处矽卡岩型矿床.文章对矿区花岗闪长岩开展了LA-ICP-MS锆石U-Pb同位素测定与岩石地球化学研究,结果表明花岗闪长岩中锆石的年龄为(240.1±0.8)Ma(MSWD=0.62),形成于中三叠世,岩石为准铝高钾钙碱性系列,轻稀土富集,轻重稀土分馏明显,具弱的负铕异常,富集大离子亲石元素(Rb、K等),同时表现出“TNT”(Ta、Nb、Ti)负异常等俯冲带幔源岩石的成分特点.依据岩石学、地球化学特征并结合同时期大地构造背景认为:花岗闪长岩产于中生代岩浆弧环境,区域同时期花岗闪长岩与石英闪长岩有着相同的物质来源与产出背景.在其他具有矽卡岩型矿化潜力的区域,今后找矿工作中应注重花岗闪长岩的成矿作用.

Zircon U-Pb age and geochemical characteristics of granodiorite from the Haxiyatu iron-polymetallic ore district in Eastern Kunlun

Abstract: The Haxiyatu iron-polymetallic deposit is one of the typical deposits with the contribution of mantle-derived components in East Kunlun region. The authors carried out LA-ICP-MS zircon U-Pb dating of main and trace elements in the granite porphyry. LA-ICP-MS dating of zircons from the quartz diorite yielded an age of 246.8±1.8 Ma (MSWD=0.074), suggesting that the rock was formed in middle Triassic and should belong to metaluminous high potassium calc alkaline series, characterized by obvious fractionation of REE, enrichment of LREE and slightly negative Eu anomaly. The granodiorite is enriched in LILE (such as Rb, Ba and K), and relatively depleted in HFSE (such as Ta, Nb and Ti). According to lithological and geochemical characteristics as well as geotectonic background in the same period, the granodiorite was probably produced in Mesozoic magmatic arc environment, with the same source material from the crust-mantle mixing as the quartz diorite. In other strata of skarn mineralization potential, due attention should be paid to granodiorite mineralization in future prospecting work.