【摘要】 云南大坪金矿是哀牢山金矿带中最重要的金矿之一,主要赋存在受到强烈韧性剪切和水-岩反应的加里东期闪长岩中,是典型的韧性剪切带控矿型金矿。本文对大坪金矿绢英岩化近矿围岩中的热液绢云母进行了40Ar-39Ar定年,得到其坪年龄为33.76±0.65Ma,相应的反等时线和正等时线年龄分别为33.55±0.74Ma和33.57±0.74Ma,显示大坪属于喜马拉雅早期金矿。这些年龄数据与哀牢山金矿带中广泛出现的喜马拉雅期煌斑岩脉年龄(33～34Ma)非常接近,显示金矿与上地幔部分熔融形成的煌斑岩之间可能存在成因上的联系。喜马拉雅早期,本区在地壳拉张和强烈韧性剪切条件下,Moho面上升,地幔物质部分熔融并上涌,形成大量煌斑岩等基性岩脉,地幔排气形成的深源地幔流体和下地壳脱水形成的富CO2流体混合,沿韧性剪切带上升,并与糜棱岩化的加里东期闪长岩围岩发生水-岩反应,局部发生流体沸腾作用,导致成矿流体物理化学条件的改变和矿石矿物的沉淀,在剪切带脆性构造中形成含金石英脉。更多还原

【Abstract】 Being one of the largest gold deposits in the Ailaoshan gold belt in Yunnan Province, the Daping gold mine occurred in a strongly mylonitized and sericitized Caledonian diorite batholith, and is a typical ductile shear zone-controlled gold deposit. 40Ar/ 39Ar dating was performed on hydrothermal sericite collected from mylonitized and sericitized diorite around rock of the Daping gold deposit, which yielded a set of age data, i.e., plateau age of 33.76±0.65 Ma, inverse and normal isochronal ages of 33.55±0.74 Ma and 33.57±0.74 Ma, respectively. These age data are very similar to ages （33³4 Ma） of the lamprophyre dykes, which are extensively distributed in the Ailaoshan gold belt, suggesting that gold mineralization of the Daping mine was closely related to the Cenozoic lamprophyre dykes, which were generated by partial melting of the upper mantle. From early of the Cenozoic Era, upwelling of the Moho and partially melted upper mantle caused by crustal extension and strong ductile deformation resulted in formation and intrusion of large amounts of lamprophyre dykes. The mantle-derived fluids formed by the upper mantle degassing and the CO₂-riching fluids from the lower crust released by dehydration and roasting triggered by the rising hot mantle magma’s heat mixed and migrated up along micro-fractures in the shear zone, and reacted with the mylonitized and sericitized diorite around rock, and finally deposited the ore minerals in the brittle structures of the shear zone because of water-rock interaction and boiling.更多还原