黑龙江东安金矿床流体包裹体特征及矿床成因研究

Study on the characteristics of fluid inclusions and implications for deposit genesis of Dong'an gold deposit,Heilongjiang province

东安金矿床受断裂构造和中酸性侵入体联合控制,流体包裹体研究表明,石英中主要发育气液二相及少量单液相包裹体,成矿流体属H2O-NaCl体系类型。成矿流体具有低盐度(0.7%~3.05%NaCl)、低密度(0.7~0.94 g/cm3)的特征,成矿温度为110.8~337.7℃,主体成矿温度区间为160~180℃,成矿压力为7.61~20.19 MPa,主体成矿深度为1.6~1.8 km。氢、氧同位素分析显示,成矿流体δDSMOW值为-90‰^-98‰,δ18OH2O值为0.6‰~4.0‰,表明成矿流体主要来自大气降水。典型的围岩蚀变有冰长石化、硅化、绢云母化。综合研究表明,东安金矿床属于由近中性、还原的低温流体形成的低硫化型浅成低温热液金矿床。

Dong＇ an gold deposit is controlled by both fault structure and intermediate-acid intrusive rocks. The fluid inclusion study shows that there are air-aqueous two-phase and few pure aqueous phase inclusions in quartz. It is indicated that the ore-forming fluid belongs to H2O-NaCl system and the fluid is characteristic of low salinity （0.37 % - 3.05 % NaCl） and low density （0.7 - 0.94 g/cm^3 ）. The formation temperature ranges from 110.8 ℃ to 337.7 ℃. The main ore-forming temperature is between 160 ℃and 180 ℃. The value of pressure is from 7.61 MPa to 20.19 MPa and the main ore-forming depth is from 1.6 km to 1.8 km. Based on the compositional analytical results of fluid inclusions, the value of 8DSMOW is between -90 ‰ and - 98 ‰, while that of δ^18OH2O is from 0.6‰ to 4.0‰. It is concluded that the ore forming fluids mainly originated from meteoric water. The typical alterations of wallrock are adulariazation, silicification, sericitization. In general, it is a low sulfuration epithermal gold deposit related to nearly neutral, reductive and low temperature fluid.