新疆阿舍勒铜矿容矿围岩蚀变的低钠晕及其意义

THE SODIUM DEPLETION AND ITS SIGNIFICANCE OF THE HOST VOLCANIC ROCKS IN ASHELE COPPER MINE,XINJIANG

新疆阿舍勒铜矿的容矿围岩是一个套双峰式海相火山岩组合.围岩蚀变由多期次叠加和变质作用的影响而变得极为复杂,以细碧质岩石的青盘岩化、石英角斑质火山碎屑岩的黄铁绢英岩化为主要特点.更有意义的是,虽然原岩属钠质火山岩系,但容矿围岩无论是酸性次火山岩还是基性火山岩,蚀变后都具有低钠的共同特点.这对于同类矿床具有找矿意义.低钠晕是海底火山喷气过程中高温气液交代而成,可作为海底火山喷发矿床的一个成因和找矿标志.

The volcanic rocks hosting the Ashele copper deposits are bimodal ones. Spilites beneath the No. 1 ore deposit are altered mainly by chlorite,carbonate and minor quartz and sericite. They are characterized by low K2O and Na2O, but high MgO and volatiles such as H2O+ and CO2. Quartz-keratophyric tuffs host the No. 2 barite-polymetallic deposit. They are altered by pyrite, sericite and quartz, with a chlorite-carbonate-rich core just below the stratiform orebodies and characterized by low Na2O content,relatively high volatile and high K2O chemically. So,both No. 1 and No. 2 ore deposits have a -common feature of sodium depletion in footwall or/ and hostrocks. This feature can be used as a useful pathfinder to volcanic-hosted massive sulfide deposits.