新疆哈图金矿床流体包裹体理化特征与成矿意义

Physicochemical characteristics of fluid inclusions of the Hatu gold deposit,Xinjiang and their metallogenic significances

哈图金矿床位于新疆北部准噶尔盆地西缘哈图断裂和安齐断裂夹持的狭长地带中。矿床受安齐断裂及其周围伴生的次一级断裂的控制,主要产出石英脉型和蚀变岩型2种金矿体。根据矿物共生关系和脉体穿插关系,将哈图金矿床从早到晚划分为3个成矿阶段。石英脉流体包裹体研究显示,矿体存在3种类型的流体包裹体,分别为Ⅰ型:富液相L+V两相包裹体;Ⅱ型:富气相L+V两相包裹体;Ⅲ型:CO2-H2O型三相包裹体。早阶段发育Ⅰ型、Ⅱ型和Ⅲ型包裹体,均一温度293～379℃,流体盐度为1.0%～5.7%。中(主)阶段发育Ⅰ型、Ⅱ型和Ⅲ型包裹体,均一温度213～291℃,流体盐度为0.5%～5.9%。晚阶段只发育Ⅰ型包裹体,均一温度148～216℃,流体盐度为1.4%～4.0%。经过压力和深度计算,成矿压力为49～97 MPa,对应深度在4.8～9.4 km。根据哈图金矿石英的δ18OV-SMOW值为20.4‰～21‰,计算得到平衡水的δ18OH2O值在8.6‰～14.7‰,同时测得石英包裹体水的δ18DH2O为-77.2‰～-64.5‰。和前人研究结果对比,认为哈图金矿床为造山型中-低温热液金矿床,成矿流体是以大气降水为主体受岩浆和变质影响的低盐度CO2-H2O体系。

The Hatu gold deposit is located in a narrow and long zone sandwiched between the Hatu and Anqi faults in the western margin of the Junggar basin, northern Xinjiang. The deposit is controlled by the Anqi fault and surrounding secondary faults. There are mainly two kinds of gold ore bodies, including the quartz vein type and altered rock type. There ore-forming stages in the Hatu gold deposit has been identified based on the relationships of mineral paragenesis and cross-cutting veins. The study of fluid inclusions in quartz veins shows that there are three types of fluid inclusions in ores of the deposit. Type Ⅰ is a liquid-rich inclusion with two phases(L+V). Type Ⅱ is a vapor-rich inclusion with two phases(L+V). Type Ⅲ is a CO2-H2O-bearing inclusion with three phases. The Type I, Type II and Type III inclusions are all developed in the early stage. Their homogenization temperatures vary from 293 to 379 ℃, and their fluid salinities vary from 1% to 5.7% NaCleqv. The Type I, Type II and Type III inclusions are also developed in the middle stage(the main ore-forming stage). Their homogenization temperatures vary from 213 to 291 and the℃ ir fluid salinities vary from 0.5% to 5.9% NaCleqv. In the late hydrothermal stage, only Type I inclusions are developed, with their homogenization temperatures ranging from 148 to 216 ℃, and the fluid salinities ranging from 1.4% to 4% NaCleqv. Based on the pressure and depth calculation, the metallogenic pressures of inclusions vary from 47 to 97 MPa and the corresponding depths are ranging from 4.8 to 9.4 km. The δ18OV-SMOW values of the quartz vary from 20.4‰ to 21‰. The calculated δ18OH2Ovalues of the balanced water vary from 8.6‰ to 14.7‰. The δ18DH2O value of fluid the inclusion fluids in quartz are ranging from-77.2‰ to-64.5‰. Compared with results of the previous studies, we have proposed that the Hutu gold deposit is an orogenic type medium-low temperature hydrothermal gold deposit, and the ore-forming fluid is a low salinity and low density CO2-H2 O system with dominant meteoric water influenced by magmatic and metamorphic hydrothermal waters.