辽西北地金矿床1号矿脉地质特征及流体包裹体研究

Geological characteristics and fluid inclusions of the No. 1 vein in Beidi Gold Deposit in western Liaoning Province

1号矿脉为北地金矿区主要工业矿脉,产于燕山期石英二长岩内,受南北向断裂构造控制。对北地金矿床金矿石进行了镜下鉴定、电子探针分析和流体包裹体岩相学、显微测温研究。结果表明,北地金矿床中金矿物主要以银金矿为主,成矿作用可分为热液成矿期和表生氧化期,其中热液成矿期具有多阶段性特点,围岩蚀变发育。金矿石石英中主要发育含CO_2包裹体、气液二相包裹体、含CO_2三相包裹体和纯CO_2包裹体,成矿过程中流体经历了NaCl-H_2O-CO_2体系的不混溶作用;成矿流体具有低盐度(1.63%~9.34%NaCl_(eqv))、低密度(0.66~0.96 g/cm^3)的特点;成矿温度集中于260℃~320℃,成矿压力为63~124 MPa,成矿深度为6.39~9.26 km。综合分析确定,矿床成因类型为受断裂构造控制的中温热液脉型金矿床。

The No. 1 vein of the Beidi Gold District is the main industrial vein in the mining area,which occurs in the quartz monzonite of Yanshan period and is controlled by the NS fault structure. Microscopic identification,electron microprobe analysis and fluid inclusion analysis of the ore in the Beidi Gold Deposit were carried out as well as studies on its petrography and microscopic temperature measurement. The results show that the gold minerals in the Beidi Gold Deposit are mainly silver and gold. Mineralization is divided into 2 stages： hydrothermal mineralization stage and supergene oxidation stage. Among them,the hydrothermal mineralization period is characterized by multistage and the alteration of surrounding rocks. Gold-bearing quartz mainly consists of CO2 inclusions,gas-liquid two-phase inclusions,CO2-containing three-phase inclusions and pure CO2 inclusions. During the ore-forming process,the fluid underwent immiscibility in the NaCl-H2O-CO2 system. The ore-forming fluid is characterized by low salinity（ 1. 63 %-9. 34 %Na Cleqv） and low density（ 0. 66-0. 96 g/cm3）. The metallogenic temperature concentrated between 260 ℃ and 320 ℃. The ore-forming pressure is 63-124 MPa. The ore-forming depth is 6. 39-9. 26 km. The genetic type of the deposit is determined to be a mesothermal hydrothermal vein gold deposit controlled by the fault structure.