Ore-fluid geochemistry of the J0 orebody, Jinchang gold deposit, Heflongjiang province, China

黑龙江省东宁县金厂金矿床是最新发现的特大型金矿床,目前探获黄金资源量86吨,它位于中亚造山带东端的吉黑成矿带,是与中生代中酸性岩浆活动有关的复杂成矿系统,矿化类型可能包括了斑岩型、爆破角砾岩型、浅成低温热液型.研究表明,高丽沟J0号矿体为爆破角砾岩型,热液成矿过程经历了早、中、晚3个阶段,分别形成以石英-黄铁矿、多金属硫化物-石英和碳酸盐为代表的矿物组合,中阶段矿物含自然金最多,次为早阶段矿物.初始成矿流体系统为高温、高盐度、高氧逸度、富CO2的岩浆热液;经减压沸腾,CO2等挥发分大量逸出,流体温度、盐度和氧逸度下降,导致大量金属硫化物及自然金快速沉淀;大气降水混入导致晚阶段流体低温、低盐度、贫CO2,对成矿贡献甚微.总体而言,成矿流体盐度高(11.70%～37.81%NaCl.eq),成矿作用发生在中-高温(238.3～425.7℃)的浅成环境(深633m～2736m).岩浆-流体成矿系统富CO2应发育于大陆碰撞造山带的伸展构造背景,而非大洋板块俯冲诱发的岩浆弧背景.The Jinchang gold deposit, located in Dongning County, Heilongjiang Province, is a giant deposit that has been discovered recently, with resource up to 86 tons of gold. Occurring in the Jilin-Heilongjiang Metallogenic Belt in the eastern Central Asia Orogenic Belt, it is a complex ore-system possibly including porphyry-, explosive breecia- and epithermal-styles. The ore-system is associated with Mesozoic intermediate-acidic volcanic-subvoicanic rocks. The J0 orebody is regarded to be of explosive breccia-type. Studies in ore geology and isotope and fluid inclusion geochemistry show that the ore-forming process of the J0 orebody includes three stages, the early, middle and late stages, characterized by mineral assemblages of quartz-pyrite, quartz-polymetallic sulfides and quartz-carbonate, respectively. Most of the native gold grains are observed in the middle-stage minerals, and next in the early-stage pyrite. The initial ore-fluids were magmatic in origin and characterized by high temperature, high salinity, high oxygen-fugacity and high content of CO(2). Fluid-boiling resulted in release of volatiles such as CO, and decrease in oxygen-fugacity, causing rapid precipitation of sulfides and native gold in middle stage. Meteoric water input made the late-stage fluids dilute, CO(2)-poor and epithermal, and slightly contribute to Au-mineralization. The J0 orebody of the Jinchang gold deposit is holistically an intrusion-related, shallow-developed (633m similar to 2736m), high salinity (11. 70% similar to 37. 81 % NaCl. eq) and medium-to-high temperature (238. 3 similar to 425. 7T) hydrothermal ore-system. The ore-system, characterized by high-content of CO(2), must be developed in extensional regime of a thickened collisional orogen, instead of a magmatic are related to oceanic plate subduction.国家自然科学基金SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)1151131-11442