内蒙古赛乌素金矿成矿流体特征

Ore-forming fluids of Saiwusu gold deposit,Inner Mongolia,China.

内蒙古赛乌素金矿是华北地台北缘金成矿带内的中低温热液型矿床。金的矿化类型是以石英脉型和蚀变岩型为主。矿体的形成与外围的晚古生代碱性花岗岩有着密切的成因联系,主要经历了四期流体成矿作用。成矿前期伴随花岗岩体的侵位及岩浆热液的活动,在早期近东西向的断层带内充填乳白色石英大脉,构成矿脉的主体,但无金成矿;初期成矿阶段富含 CO_2-CH_4-H_2O 的流体活动,叠加在石英大脉之上,形成块状黄铁矿—浅色石英矿体;主期成矿阶段,混合了地表水的岩浆期后热液与围岩发生物质交换,形成富含 CH_4-H_2O 的流体和网脉状多金属硫化物—烟灰色石英矿体,主成矿期热液温度的降低及流体组成的变化是金沉淀成矿的主要原因;成矿后期形成的碳酸盐—石英脉体,基本无矿化。

The Saiwusu is one of the low-middle hydrothermal deposits in the gold belt of the north margin of North China Craton. The deposit was related to the Late Paleozoic alkaline granitoids distributed beside it, and the mineralization type is mainly quartz veins and altered rocks. Four successive crystallization stages are recorded during the formation of gold deposit. Stage Ⅰ- the milky quartz veins were developed in earlier WE-trending faults belt associated with the intrusion of the granitoids and fluid activity, and no clear evidence was found for gold deposition during this stage. Stage Ⅱ - massive pyrite--clear quartz ores formed in earlier milky quartz veins and the fluids were CO2-CH4-H2O type. Stage Ⅲ- the main episode of gold deposition, network polymetallie sulfide minerals and grey color quartz ores deposited from CH4-H2O fluid. Temperature reducing and compositions change of ore-forming fluids resulted from exchange between fluid, surface water and wall rocks were the main causes for gold deposition. Stage Ⅳ- quartz and carbonate mineral veins were formed and weak gold mineralization happened.