穆龙套金矿地质和地球化学

Geology and Geochemistry of Muruntau Gold Deposit

总结了世界最大造山型金矿穆龙套金矿(黄金储量>6100t)的地质、地球化学特征。穆龙套金矿的赋矿围岩为晚奥陶世-早志留世黑色碳质页岩,矿床产于剪切带和断裂的交汇部位,受韧性剪切带控制。下部有强烈蚀变的白岗岩(约287Ma),矿体北部出露火成岩岩墙(273～286Ma)。金主要赋存于石英脉中,矿石及其围岩蚀变组合的地球化学特征指示了岩浆流体对成矿作用的贡献,但流体包裹体研究表明,成矿流体中绝大多数He来自地壳,惰性气体主要来自大气。金矿年龄被确定为约275Ma(Sm-Nd等时线)、226～254Ma(绢云母40Ar/39Ar坪年龄)和约290Ma(毒砂Re-Os)。在有限的地区内短时期形成巨型金矿需要特殊的机制和长期的流体演化过程。

This paper summarized the geological and geochemical features of the Muruntau gold deposit, the largest orogenic-type gold deposit in the world with gold reservoir of 〉 6100 t. The ore bodies locate at the intersection of shear zones and faults. The wall-rock of the gold veins is black carbon schist of Upper Ordovician-lower Silurian. Alaskite （-287 Ma）, occurring beneath the Muruntau ore body, had been extensively altered. Igneous dikes （273-286 Ma） expose in the north of the ore region. Native gold grains occur in quartz veins. Geochemistry of the alteration assemblages and the ores suggested magmatic contributions of the ore-forming fluid in some degree. The fluid inclusion analysis, however, implied that overwhelming majority of He came from continental crust, and the noble gases were from atmosphere. Age of gold mineralization had been determined to be -275 Ma （Sm-Nd isochrone）, 226-254 Ma （sericite 40Ar/39Ar plateau） and -290 Ma （arsenopyrite Re-Os）. It requires special mechanisms and prolonged fluid evolution for such a giant ore deposit to form within a short time span and within a limited area. Shear zones, which control the terminal location of the Muruntau gold deposit, are the widespread signals and exploration indicators for gold deposits in the Central Asian Metallogenic area.