内蒙古别鲁乌图铜多金属矿床锆石U-Pb年龄和S、Pb同位素特征及其地质意义

为了明确内蒙古别鲁乌图铜多金属矿床的成矿年龄与矿床成因,对该矿床中与成矿关系密切的流纹岩进行了锆石U-Pb年龄以及主要金属硫化物的S、Pb同位素测试。其中流纹岩的锆石206Pb/238U加权平均年龄为(271.7±1.6)Ma(MSWD=1.02),显示成矿作用发生于二叠纪。金属硫化物的S同位素分析结果显示δ34SV-CDT值分布在-0.6‰~1.0‰之间,平均为0.49‰,变化范围较窄,显示S的来源单一;Pb同位素组成比较集中,206Pb/204Pb为18.207~18.674,207Pb/204Pb为15.620~15.699,208Pb/204Pb为38.144~38.790,具有壳幔混源的特征。S、Pb同位素特征均指示成矿物质主要来源于岩浆热液。结合区域地质、矿床地质、空间分带等特征以及S、Pb同位素组成可知,别鲁乌图铜多金属矿床为VHMS型矿床,形成于二叠纪陆缘弧裂谷中。

Zircon U-Pb Age and S-Pb Isotope Features of the Bieluwutu Copper-polymetallic Deposit and Their Geological Significance

To clarify the metallogenic age and genesis of the Bieluwutu copper-polymetallic deposit,zircon U-Pb age of the ore-related rhyolite and sulfide S-Pb isotopes were analyzed.The weighted mean zircon 206Pb/238U age of the rhyolite is(271.7±1.6)Ma(MSWD=1.02).This suggests that the ore-related rhyolite and the Bieluwutu copper-polymetallic deposit was formed in the Permian.Sulfur isotope data show that theδ34SV-CDT variation is small(-0.6‰to 1.0‰,average 0.49‰),implying that the sulfur may have come from a single source.The sulfide lead isotope compositions are relatively consistent,i.e.,206Pb/204Pb(18.207-18.674),207Pb/204Pb(15.620-15.699)and 208Pb/204Pb(38.144-38.790),featuring a mixed crust-mantle source.These S-Pb isotopic compositions indicate that the ore-forming materials were principally originated from magmatism.Evidence from regional and local geology,mineralization zonation and sulfur and lead isotopes support that the Bieluwutu copper-polymetallic deposit belongs to VHMS-type and was formed in an intra-arc rift during the Permian.