湖南瑶岗仙钨矿花岗岩中暗色包体的发现及其地球化学特征

Dark Inclusion in the Yaogangxian Granite,Hunan Province and its Geochemical Characteristics

湖南瑶岗仙钨矿区与成矿有关的碱长花岗岩内除含有云英岩包体和早期花岗岩包体外,还有一种特殊的暗色包体。该暗色包体矿物组成复杂,包括钠长石、钾长石、石英、白云母、电气石、绿泥石、白铁矿、磁黄铁矿以及少量黄铜矿、闪锌矿、方铅矿等硫化物。通过对比暗色包体、寄主碱长花岗岩以及铁镁质包体矿物学及地球化学特征,初步认为暗色包体可能是由铁镁质包体蚀变而来,其地球化学特征受到寄主花岗岩强烈影响。暗色包体中产出大量白铁矿和绿泥石,由此说明,瑶岗仙岩体岩浆演化晚期属于一个温度较低并呈弱酸性的环境。

In addition to the greisens and early granite inclusions,special dark inclusions were found in the alkali feldspar granite of the Yaogangxian deposit.Compositions of these dark inclusions are very complex,containing albite,K-feldspar,quartz,muscovite,tourmaline,chlorite,marcasite,pyrrhotite and some other sulfides such as chalcopyrite,sphalerite,and galena.After studying mineralogical and geochemical characteristics of the dark inclusions,host alkali feldspar granite and mafic enclaves,we concluded that the dark inclusions are metasomatic alteration products of the mafic enclaves and their geochemical characteristics were strongly affected by the host granites.Meanwhile,significant amounts of marcasite and chlorite in the dark inclusions indicated the evolution environment of the later period Yaogangxian magmatic fluids is a lower temperature and lower salinity environment.