辽宁宽甸东北沟钼矿床辉钼矿Re-Os年龄及其地质意义

Re-Os Isotopic Age and Geological Significances of the Dongbeigou Molydbenum Deposit in Kuandian,Liaoning Province

为研究辽宁宽甸地区近年来新发现的东北沟钼矿的成矿时代及其物质来源,对东北沟钼矿床中的5件辉钼矿样品进行了Re-Os同位素地球化学测试和定年。结果表明,辉钼矿的模式年龄为127.1~132.6 Ma,等时线年龄为(128.1±5.1)Ma,与赋矿围岩二长花岗岩的成岩时代(129.4 Ma)一致,由此认为二者均为燕山期构造-岩浆-成矿作用的产物;辉钼矿Re含量为(5.10~23.38)×10^(-6),与内生钼矿床辉钼矿Re含量对比介于壳源-壳幔混合源之间,初步判定东北沟钼矿成矿物质来源介于壳源与壳幔混合源之间,有可能以壳幔混合源为主。结合区域构造演化,认为东北沟钼矿可能是古太平洋板块向欧亚大陆俯冲构造背景下岩浆活动的产物。

The Dongbeigou molybdenum deposit is a newly discovered large-sized cryptoexplosive breccia-type molybdenum deposit in the Kuandian area, Liaoning Province. Molybdenite was selected from for Re-Os dating. Five sam- ples have Re-Os isotopic model ages of 127. 1 Ma to 132.6 Ma, yielding an isochron age of 128. 1±5.1 Ma, which con- sistent with the intrusive age of ore-bearing monzogranite（ 129.4 Ma）. It can thus be concluded that both monzogranite and molybdenum deposit were formed in Early Cretaceous. Rhenium content in the molybdenite ranges from 5. lOx 10-6 to 23.38 ~ 10-6, in the range between crust and crust-mantle mixed sources, suggesting that the ore-forming material might be derived from crust or a mixed crustal-mantle source. Combed with the tectonic evolution history of the region, we also infer that the Dongbeigou molybdenum deposit is likely to be the product of subduction of the Pacific plate beneath Eurasia plate.