内蒙古鸡冠山钼矿流纹斑岩的成岩年龄及地质意义

Diagenetic Age of Rhyolite Porphyry in the Jiguanshan Mo Deposit,Inner Mongolia and its Geological Implications

内蒙古鸡冠山钼矿床是近年来发现的一个大型斑岩型钼矿床,位于华北克拉通北缘、西拉沐沦钼矿带的中段,产出于一破火山机构的NW侧。矿床矿石矿物辉钼矿Re-Os同位素等时线法测得成矿年龄为151.1±1.3Ma,为晚侏罗世成矿。本文通过SIMS锆石U-Pb年龄法,测定流纹斑岩成岩年龄为148.5±3.3Ma(U-Pb等时线年龄,2σ,MSWD=2.2),为晚侏罗世成岩。该成岩年龄与成矿年龄在误差范围内一致,说明与流纹斑岩有关的岩浆活动可能形成成矿的母岩浆,成岩与成矿近乎同时发生。

The Jignanshan Mo deposit of Inner Mongolia is a newly discovered large porphyry type Mo deposit, It is located in tile middle of Xilamulun molybdenum ore hell, isotope isocbron netbod determined tile metallogenic age to be l Sl.l ：t： 1.3 Ma, indicating mineralization in the late Jurasiv. In this work, zircon SIMS U-Pb isotopic dating was used to estimate the diagenetic age of rhyolite porphyry, yiehling 148.5-3.3Ma （ U-PIp isoehron age, 2a, MSWD=2.2）. It shows the rhyolite porphyry formed in the late Jurassic, largely in agreement with the mineralization age in the range of error. We suggest that the rhyolite porphyry magnlatism nlay Iorm ore -bearing parent magma, anti the diagenesis and mineralization of euiTed at approximately the same time.