东天山四顶黑山层状岩体地质特征及成矿潜力分析

东天山黄山岩带因发育众多镁铁质-超镁铁质岩体和岩浆铜镍硫化物矿床而备受地质学者关注。四顶黑山岩体位于该岩带最东端,具有层状岩体特征;岩石类型有单辉橄榄岩、橄榄辉石岩、橄榄苏长辉长岩、橄榄辉长岩、辉石角闪岩、辉长岩、角闪辉长岩、闪长岩,主要造岩矿物为贵橄榄石、古铜辉石、透辉石、普通角闪石和斜长石,岩体分异较好,蚀变较发育。通过矿物显微结构特征观察以及计算得出:四顶黑山岩体中橄榄石最先结晶,其开始结晶温度大约在1419℃左右;古铜辉石和透辉石在橄榄石之后开始结晶,结晶温度分别在1100℃左右和900～1100℃之间,两矿物相在岩石中可以共存。岩体中橄榄岩相、苏长岩相发育,以及贵橄榄石+古铜辉石的矿物组合特征,表明岩体具有形成铜镍(铂)矿床的有利条件。

Geological Characteristics and Ore-forming Potential of Sidingheishan Stratified Mafic-ultramafic Intrusion in East Tianshan Mountains

The Huangshan mafic-ultramafic rock belt in East Tianshan Mountains has around much interest among geologists due to the development of many mafic-ultramafic intrusions and nickel-copper magmatic sulfide deposits.Located in the eastern part of this belt,the Sidingheishan mafic-ultramafic intrusion is a stratified intrusion composed of clinopyroxene peridotite,olivine pyroxenite,olivine norite-gabbro,olivine gabbro,pyroxene amphibolite,gabbro,hornblende gabbro and diorite,its main rock-forming minerals are chrysolite,bronzite,diopside,hornblende and plagioclase,its differentiation is fairly perfect,and its alteration is well developed.A study of the mineral microstructure characteristics and the calculation show that in Sidingheishan intrusion,olivine was the first crystallized mineral,followed by bronzite and diopside,whose crystallization temperatures were about 1100 ℃ and 900～1100 ℃,respectively,and the two minerals in the rock can coexist.The peridotite facies,norite facies,and the chrysolite + bronzite mineral assemblage show that the Sidingheishan intrusion has favorable conditions for the formation of copper-nickel(platinum) deposits.