库车盆地铜矿化与盐丘系统的关系

Relationship between surface copper mineralization and salt dome system in Kuqa basin

库车盆地新近系发育一系列盐丘体,遥感解译和野外地貌调查共发现36个盐丘体,主要分布在南部的秋里塔格构造带和北部的克拉苏构造带,沿近东西向断裂呈带状分布。在盐丘体的发育过程中,盐丘体、围岩及围岩中发育的断裂与破碎带等构成一个盐丘体系统。调查显示铜矿化发育在盐丘体附近,位于盆地南、北两大构造带(背斜带)轴部偏两翼处,共有砂岩型、泥岩型、灰岩型3种类型,主要矿物为氯铜矿,矿化层位于上新统的康村组和中新统的吉迪克组。扫描电镜分析发现,盐丘体中盐岩样品含有自然铜、氯铜矿,表明盐丘体可以为地表铜矿化提供铜源,而卤水中的盐分来自盐丘体中盐、膏的溶解。盐丘系统不但为地表铜矿化提供铜源,而且其卤水对铜的富集、运移起到载体作用。存在于盐丘系统围岩并与后期盐丘体相伴生的断裂、节理、破碎带,为含铜卤水的迁移提供通道,盐丘体后期的构造挤压力,成为含铜卤水的运移动力。因此,盐丘系统发育过程对碎屑岩型铜矿形成起到关键性控制作用。

A series of Neogene salt domes are developed in Kuqa basin.Up till now,36 salt domes have been found by remote sensing and field morphologic investigation,which are mainly scattered in Qiulitage tectonic belt in the south and Kelasu tectonic belt in the north,exhibiting EW-trending faulted zonal distribution.During the deve-lopment of the salt domes,salt domes and wall rocks as well as fault structures and shatter zones developed in wall rocks constitute a salt dome system.Surface copper mineralization is developed near the salt dome,lies at the axial parts of the two large tectonic belts（anticlinal belts）,somewhat close to the two limbs,and consists of four types,i.e.,sandstone type,mudstone type,limestone type and sulfide-bearing quartz vein type.The main mineral in the first three types is atacamite,and the mineralized horizons are located in Pliocene Kangcun Formation and Miocene Jidike Formation.Scanning electron microscopic analysis reveals that salt rock samples from the salt dome contain native copper and atacamite,suggesting that the salt dome could provide copper for surface copper mineralization,whereas the salt in the brine was derived from the solution of salt and gypsum in the salt dome.The salt dome system not only provided brine and copper source for surface copper mineralization but also served as carrier for copper enrichment and migration through the brine formed by solution.The faults,joints and shatter zones that existed in the wall rocks of the salt body and were associated with later salt domes provided channels for the migration of copper-bearing brine.The late stage structural compression acted as the driving force for the migration of copper-bearing brine.