赞比亚谦比西铜矿花岗岩年龄及其指示意义

Age of granites from the Chambishi copper mine in Zambia and its implications

赞比亚谦比西铜矿位于新元古代卢菲利安弧构造带内。矿体呈似层状分布于新元古代罗安组的砂页岩中。罗安组地层不整合于古元古代穆瓦系砂砾岩之上,穆瓦系砂砾岩不整合于下部谦比西花岗岩基底之上。锆石U-Pb测年结果表明谦比西花岗岩年龄为(1984±6)Ma^(1986±6)Ma;穆瓦系年龄上限为(1932±8)Ma。谦比西花岗岩岩石地球化学、稀土元素与球粒陨石配分特征均表现为S型花岗岩的特征。区域地质资料表明,可能由于古元古代班韦卢地块与坦桑尼亚太古宙克拉通碰撞作用诱发了卢菲利安古元古代花岗岩基底的形成;太古宙刚果克拉通于早元古代(2100~1800 Ma)期间活化,并形成一稳定块体。

The Chambishi copper mine in Zambia is located in the central Africa copper-cobalt metallogenic belt.The bedded orebodies occur in the Neoproterozoic sandshales of Roan Formation.The Roan Formation unconformably overlies the Early Proterozoic sandy conglomerate of Muwa System,which in turn overlies the lower Chambishi granite basement.U-Pb zircon dating yielded the age of1984±6-1986±6Ma for Chambishi granite,and the upper age limit is1932±8Ma for Muwa System.The lithogeochemistry and chondrite-normalized REE patterns of Chambishi granites have the characteristics of S-type granites.Combined with the data of regional geological evolution,the authors believe that Archean Congo craton may have experienced activation over a large area during Early Proterozoic period,and a stable ancient block had been formed in the Early Proterozoic period.