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洛古河矿床为额尔古纳地块东北部的一个以铅锌为主、伴生铜钼的多金属矿床。为确定该矿床的成因、形成时代及构造背景,开展矿床地质特征研究和同位素测年工作。矿床地质研究表明,该矿床的主矿体主要呈层状、似层状和透镜状,赋存于额尔古纳河组大理岩与黑云母二长花岗岩的接触带附近;矿石中金属矿物主要为方铅矿、闪锌矿、黄铜矿、黄铁矿、辉钼矿,矿石构造以浸染状构造和细脉状构造为主;围岩蚀变类型主要包括矽卡岩化、硅化、绢云母化、碳酸盐化和绿帘石化。同位素测年结果表明,钻孔中矿体附近的黑云母二长花岗岩锆石U-Pb年龄变化范围为137 Ma±3 Ma~123 Ma±1 Ma,加权平均值为131.4 Ma±2.1 Ma(n=21,可信度95%);矿区内花岗斑岩锆石U-Pb年龄变化范围为129 Ma±1Ma~116Ma±2Ma,加权平均值为121.8Ma±1.9Ma(n=16,可信度95%);矽卡岩型多金属矿石中辉钼矿Re-Os模式年龄为127.1 Ma±2.1 Ma。综合分析认为,洛古河矿床属接触交代型多金属矿床,黑云母二长花岗岩为成矿岩体,成岩成矿时代为130 Ma~120 Ma,属大兴安岭北部早白垩世强烈构造岩浆作用的产物。结合区域构造演化及同时代同类矿床对比分析,初步认为洛古河多金属矿床成岩成矿作用发生于蒙古—鄂霍次克洋俯冲闭合后的造山后伸展的构造背景。
The Luogu River deposit is a lead-zinc-dominated polymetallic deposit with copper and molybdenum in the northeast of the Erguna block. In order to determine the genesis, formation age and tectonic setting of this deposit, the study on the geological characteristics of the deposit and the dating of isotopes are carried out. The study of deposit geology shows that the main ore body of the deposit is mainly layered, stratified and lenticular and occurs near the contact zone between the Ergun granite and the Ergun granulite in the Erguna Formation. The metal minerals in the ore are mainly The galena, sphalerite, chalcopyrite, pyrite, molybdenite and ore are dominated by disseminated structures and fine vein structures. The types of wall rock alteration mainly include skarnization, silicification, silk Michemization, carbonation and green curtain petrochemical. The isotopic dating results show that the zircon U-Pb ages of biotite monzogranite near the orebodies in the borehole range from 137 Ma ± 3 Ma to 123 Ma ± 1 Ma with a weighted average of 131.4 Ma ± 2.1 Ma (n = 21, 95% confidence). The zircon U-Pb ages of the granite porphyry in the mining area range from 129 Ma ± 1Ma to 116Ma ± 2Ma with a weighted average of 121.8Ma ± 1.9Ma (n = 16, 95%). The Re-Os mode age of molybdenite in skarn-type polymetallic ores is 127.1 Ma ± 2.1 Ma. The comprehensive analysis shows that the Luogu deposit belongs to the metasomatic polymetallic deposit and the biotite monzogranite is a metallogenic rock. The diagenetic mineralization age is 130 Ma to 120 Ma, which belongs to the strong tectonic magmatic activity of the Early Cretaceous in the Greater Khingan Range. Based on regional tectonic evolution and comparative analysis of contemporaneous deposits of the same type, the diagenetic and mineralization of the Luogu polymetallic deposit was initially thought to occur after the orogenic extension of the Mongolian-Okhotsk subduction.