大兴安岭南麓地区脉型锡多金属矿床的控矿构造特征

大兴安岭南段西拉沐伦河以北地区发育大量锡多金属矿床,成矿作用与燕山晚期高演化岩浆有关,自岩体向外构成锡钨—铜—铅锌银的良好分带。对这一地区主要脉状锡、铅锌银矿床控矿构造研究显示,成矿中心的锡钨矿与外围的铅锌矿控矿构造性质、控矿特点明显不同。侵入岩附近控制云英岩脉、锡石石英脉的断裂构造相对陡倾,主要形成于岩浆侵入以及挥发份聚集引发的水压致裂,同时受区域应力作用的影响。远离岩体的缓倾斜石英脉以及分布于成矿系统外围的铅锌硫化物脉产状复杂,多为缓倾斜状,不同矿体及同一矿体的不同部位产状不同,但矿石性质相同,控矿断裂主要形成于成矿前,在成矿期伸展背景下重新活化。区域板内伸展的构造背景、成矿中心附近受岩浆侵位的原生断裂以及外围继承性断裂共同构成锡多金属矿控矿构造系统。不同断裂间的关系以及与之对应的矿化分带对锡多金属矿的找矿勘查有重要参考意义。

Characteristics of ore-controlling structures of vein-type Sn polymetallic deposit in the southern area of the Da Hinggan Mountains, Inner Mongolia

A large amount of tin polymetallic deposits have been explored in the north of Xar Moron river in the southern Da Hinggan Mountains, Inner Mongolia. The mineralization is related to the evolution of late Yanshannian granite intrusion. There is apparent zonation distribution of mineralization, i.e., Sn-W mineralization in the center and Cu-Pb-Zn-Ag mineralization in external part. The study result of the ore-controlling structures in the vein-type Sn-Pb-Zn-Ag deposits shows that the ore-controlling structures of the Sn-W veins in the center and the Pb-Zn-Ag veins in the external part are obviously different. The fractures which controlled greisen veins and cassiterite quartz veins formed nearby the granite are relatively steep, the veins were mainly formed in the magmatic intrusion and hydraulic fracturing process, and affected by the regional stress. The lead-zinc sulfide veins and a few quartz veins away from the granite occurred in the periphery of the metallogenic system are mostly in low dip angle with varied spatial occurrence, unless the vein with the similar mineral assemblage and ore structure. Ore-controlling faults are mainly formed before ore-forming and reactivated under the extensional background during mineralization. It is suggested that the ore-controlling tectonic system of tin polymetallic deposits consists of the extension regional tectonic setting, primary fracture near the granite and the reactivation fracture at the periphery. The relationship between different faults and their corresponding mineralization zones is important reference significance for the prospecting of tin polymetallic deposits.