内蒙古阿拉善欧布拉格铜-金矿床的成矿时代

Metallogenic Epoch of the Oubulage Copper-Gold Deposit in the Alashan Area,Inner Mongolia Autonomous Region

欧布拉格铜-金矿床位于内蒙古西部阿拉善地区,是一处远景具大型规模的铜-金矿床。矿床赋存于二叠系下统火山岩和次火山岩中,容矿岩石主要为石英斑岩和英安质熔结火山角砾岩、流纹质火山角砾岩。本文选取矿区出露的与矿化最为密切的样品,采用颗粒锆石U-Pb法和40Ar/39Ar法测定了成矿期石英斑岩脉和含矿石英脉的年龄,获得成矿期石英斑岩的锆石U-Pb年龄为277.4±3 Ma,铜-金矿体中石英的40Ar/39Ar年龄为264.26±0.46 Ma。这一结果揭示,欧布拉格铜-金矿是海西晚期形成的。结合阿拉善地区的朱拉扎嘎金矿和呼伦西白金矿都是海西晚期形成的情况分析,表明海西晚期是中国西部最重要的铜(金)矿化期之一。

The Oubulage copper-gold deposit locates in the Alashan region of west Inner Mongolia Autonomous Region,was found recently in an assessment performed by team 511,Inner Mongolia Nonferrous Metals Geological Exploration Bureau.With large scale potentiality,the deposit distributes in lower Permian volcanic rock and subvolcanic rock,the main hosting rocks are quartz porphyry,dacitic melted volcanic breccia and liparitic volcanic breccia.Single zircon U-Pb and quartz ^40Ar/^39Ar methods are applied to determine U-Pb ages of quartz porphyry vein of metallogenic epoch,and ^40Ar/^39Ar age of ore-bearing quartz vein.The experiment results show that the age of quartz porphyry is 277.4±3 Ma and the age of ore-bearing quartz vein is 264.3±0.5 Ma,indicating that Oubulage copper-gold deposit was formed in the late Hereynian Period.This copper-gold deposit and other gold deposits in the same area,such as Zhulazaga gold deposit and Hulunxibai gold deposit,all were formed in the late Hereynian Period,implying that Hereynian Period is a major copper-gold ore-forming epoch in the west of China.