广西苍梧宝山铜多金属矿床花岗岩锆石U-Pb年龄及其地质意义

摘要

The Baoshan deposit is a Cu-polymetallic deposit associated with quartz porphyry in Cangwu County of Guangxi,located in the southeastern margin of the Dayaoshan uplift.Zircon LA-ICP-MS U-Pb tests were carried out for the granodiorite,fine-grained granite and quartz porphyry from the orefield.Three analyses for the granodiorite yielded ages of 433.7±1.2 Ma,435.0±1.2 Ma and 449.7±2.3 Ma,one analysis for the fine-grained granite gave an isochron age of 100.4±0.5 Ma,and two analyses of quartz porphyry yielded isochron ages of 95.4±0.7 Ma and 92.5±0.5 Ma.Our results showed that the Baoshan Cu-polymetallic orefield experienced multi-period magmatic activity,including the Late Ordovician,Early Silurian,Early Cretaceous and early stage of Late Cretaceous.Zircon U-Pb age of the ore-related quartz porphyry indicates that this deposit was formed in the early stage of Late Cretaceous.These high-precision granite U-Pb data provide important chronological evidence for further study of the magmatic activity and metallogeny of ore deposits in the Dayaoshan area.%广西苍梧县宝山矿床位于大瑶山隆起区的东南部,是一个与石英斑岩有关的铜多金属矿床.本文对该矿区内花岗闪长岩、细粒花岗岩和石英斑岩进行了单颗粒锆石LA-ICP-MS U-Pb测年,获得了3件花岗闪长岩的206Pb/238U加权平均年龄分别为433.7±1.2 Ma、435.0±1.2 Ma和449.7±2.3 Ma;1件细粒花岗岩的206Pb/238U加权平均年龄为100.4±0.5 Ma,2件石英斑岩样品的206Pb/238U加权平均年龄分别为95.4±0.7 Ma和92.5±0.5 Ma.本文认为,宝山矿区存在晚奥陶世、早志留世、早白垩世晚期和晚白垩世早期等多期岩浆活动,与成矿有关的石英斑岩锆石U-Pb年龄揭示宝山铜铅锌多金属矿床形成于晚白垩世早期.这些高精度花岗岩锆石U-Pb测年数据为进一步深入研究大瑶山地区的岩浆活动及其成矿作用提供了重要的年代学依据.