滇西腾冲麻栗坝钼-铜-铅-锌矿床锆石LA-ICP-MSU-Pb和辉钼矿Re-Os年龄及其地质意义

Zircon LA-ICP-MS U-Pb Age and Molybdenite Re-Os Dating of the Maliba Molybdenum-Copper-Lead-Zinc Deposit and Its Geological Significance in the Tengchong Area,Western Yunnan

麻栗坝钼铜铅锌矿床位于三江特提斯成矿带的西南端,赋矿岩体为黑云母二长花岗岩,属于腾冲花岗岩带古永复式岩体小龙河序列.黑云母二长花岗岩锆石LA-ICP-MS U-Pb年龄为78.6±1.2 Ma,属于燕山晚期,相当于晚白垩世;矿体中辉钼矿的Re-Os等时线年龄为78.5±3.7 Ma,略晚于成岩时间,为本区首次获得的精确成矿年龄.其中,辉钼矿的Re、Os同位素特征表明成矿物质主要来源于地壳.麻栗坝钼铜铅锌矿床成矿年龄、成矿岩体年龄接近,约为78 Ma,与小龙河岩体年龄（79～65 Ma）在误差范围内一致,表明矿床的热液演化活动时间较短,矿化和成岩均发生在岩浆活动的早期阶段.它们同为燕山晚期,是在新特提斯洋渐次东向俯冲过程中地壳加厚重熔引发的岩浆活动与热液作用的产物.

The Maliba molybdenum-copper-lead-zinc deposit is located in the southwest of the Sanjiang Tethys metallogenic belt and is hosted in the biotite adamellitic pluton, which belongs to the Xiaolonghe sequence of the Guyong pluton in the Tengchong granite belt. LA-ICP-MS zircon U-Pb dating of the biotite adamellite yielded the age of 78.6±1.2 Ma, corresponding to the Late Cretaceous and the Late Yanshannian. The Re-Os isotopic dating of molybdenite from the Maliba ore body yielded the isochron age of 78.5±3.7 Ma, slightly later than the diagenetic time, representing the first reported high precision ore-forming age in this area. Re-Os isotopes of molybdenite suggest that the major ore-forming material derived from crust. The Maliba molybdenum-copper-lead-zinc deposit has the ore-forming age similar to the intrusion age （-78 Ma）, which is consistent with the Xiaolonghe intrusion age （79-65 Ma）, indicating that the timing of hydrothermal activity was short and both ore-mineralization and intrusion-formation occurred in the early stage of magma activities. They were formed at the late stage of Yanshan and were produced during the gradually eastward subduction process of Neo-Tethys and by magmatic and hydrothermal activities caused by remelting of crustal.