滇东北峨眉山玄武岩区的沉积型铜矿床

Sedimentary copper deposit in Emeishan basalts, northeastern Yunnan Province

在滇东北峨眉山玄武岩分布区上二叠统宣威组中发现沉积型铜矿床。文章对此类沉积型铜矿床的地质特征和成矿作用特征进行了较系统的研究,结合矿物成分和硫同位素测试结果,探讨了矿床的形成过程和找矿前景。研究表明,区内沉积型铜矿床主要有两种矿化类型:结核状铜矿化和浸染状铜矿化,矿石矿物以辉铜矿、斑铜矿、铜蓝等为主;成矿受上二叠统宣威组沉积地层控制,与峨眉山玄武岩喷溢形成的古火山构造和古地形以及火山期后的热泉活动关系密切,有机质在成矿过程中可能发挥了作用;成矿过程可能从沉积成岩阶段一直延续到成岩期后。区域上假整合覆盖于上二叠统峨眉山玄武岩之上的宣威组沉积岩系具有良好的找矿前景。

A sedimentary copper deposit was discovered in Upper Permian （P2x） Xuanwei Formation of Emeishan basalts in northeastern Yunnan Province, and the nodular copper mineralization and disseminated copper mineralization were recognized in the ore district. The ore minerals of nodular copper mineralization are mainly chalcocite, bornite and covellite, and the host rocks are greenish gray and purplish red thin-layered silt mudstone in the middle part of P2x. The ore minerals of disseminated copper mineralization are mainly chalcocite and chalcopyrite, together with a small amount of native copper, and the host rocks are bluish gray and brownish gray argillite containing organic matter in the lower to middle part of P2x. A preliminary study shows that the paleotopographic and paleovolcanic structures formed by Permian volcanic event control the sedimentation of Late Permian in the area, and that the copper mineralization is controlled strictly by Upper Permian （P2x） Xuanwei Formation and is closely related to post-volcanic activity of the hot spring. The organic matter might have played an important role in the mineralization, and the ore-forming process lasted from the diagenetic stage to the postdiagenetic stage. The sedimentary-petrologic province of Upper Permian （Pax） Xuanwei Formation in unconformity with the Emeishan basalts has good ore-search prospects.