新疆西准噶尔石屋斑岩型Cu-Au矿点地质特征、成矿流体及成矿潜力

Geology,ore-forming fluids and potential of Shiwu porphyry Cu-Au spot in West Junggar,Xinjiang

石屋Cu-Au矿位于新疆西准噶尔巴尔鲁克山东北部,是近年发现的斑岩型矿点。研究区发育闪长岩、石英闪长岩、石英闪长玢岩和英云闪长斑岩,成矿与晚石炭世石英闪长玢岩有关,矿化以细脉状和浸染状为主。热液蚀变包括钾化、硅化、电气石化、绿泥石化、绿帘石化等。矿石矿物以黄铜矿和黄铁矿为主。含矿石英脉中的流体包裹体可分为富液相(Ⅰ型)、富气相(Ⅱ型)和含子矿物相(Ⅲ型)3类。成矿过程分为3个阶段:早阶段主要发育石英、钾长石,均一温度集中在300~360℃,盐度分为中低盐度和高盐度2类;主阶段主要发育石英、黄铜矿和黄铁矿,均一温度为220~260℃,w(NaCl_(eq))为0.5%~6.9%,为中温低盐度流体,属于H_2O-NaCl-CO_2-C_2H_6-CH_4体系;晚阶段发育石英和方解石,均一温度集中在132~179℃,w(NaCl_(eq))为0.2%~6.2%,为低温低盐度流体,属于H_2O-NaCl-CO_2-CH_4-C_2H_6体系。早阶段和主阶段硫化物的δ^(34)S值为-0.2‰^+2.7‰,表明成矿物质源自岩浆。成矿流体温度、压力的下降和p H值的变化是导致矿质沉淀的主要原因。与区域上大型-超大型斑岩铜矿对比研究,发现石屋铜金矿点在成矿时代、构造背景和成矿岩体氧逸度方面与其相似,因此具有很大的成矿潜力。

The Shiwu Cu-Au ore spot which is located in the northeast of the Barluk Mountains is a newly discovered porphyry ore spot. Mineralization is associated with the quartz diorite porphyry,and the host rocks include diorite,quartz diorite,quartz diorite porphyry and tonalite porphyry. Hydrothermal alterations include potassic alteration,silicification,tourmalinization,chloritization and epidotization. Ore minerals mainly include chalcopyrite and pyrite. Fliud inclusions can be divided into three types： fluid rich type（ Ⅰ-type）,vapor rich type（ Ⅱ-type） and daughter minerals bearing type（ Ⅲ-type） inclusions. Three stages of mineralization can be distinguished in the Shiwu ore spot. Abundant quartz and K-feldspar occurred at the early stage,homogenization temperatures of fluid inclusions are mainly in the range of 300 - 360℃,and salinities have two groups（ high salinity and middle-low salinity）. Minerals of the main stage include quartz,chalcopyrite and pyrite. Homogenization temperatures of fluid inclusions vary from 220℃ to 260℃,and salinities from 0. 5% to 6. 9%; ore-forming fluid which has middle temperature and low salinity belongs to the H_2O-NaCl-CO_2-C_2H_6-CH_4 system. Minerals of the late stage mainly include quartz and calcite. Homogenization temperatures of fluid inclusions vary mainly from 132 to 179℃,and salinities from 0. 2% to 6. 2%; ore-forming fluid which belongs to the H_2O-NaCl-CO_2-CH_4-C_2H_6 system has low temperature and low salinity. Sulfide δ-（34）S values which range from -0. 2 ‰ - ＋ 2. 7 ‰ indicate that the sulfur came from magma. Associated with the fluid ascent,the decrease of temperature and pressure and change of p H seem to have been the factors resulting in the formation of the Shiwu Cu-Au ore spot.Based on the above research,we concluded that the Shiewu ore spot has similar mineralogenetic epoch,tectonic setting and oxygen fugacity with other porphyry Cu deposits in this region and hence it has enormous metallogenetic potentiality.