冈底斯成矿带东段的电性结构特征研究

A study on the electrical structure of eastern Gangdese metallogenic belt

冈底斯成矿带为我国著名的成矿区域,其东段存在一系列规模较大的矿床.为了研究冈底斯成矿带东段的电性结构特征,对覆盖主要矿集区的大地电磁测深数据进行全面的处理分析,通过二维与三维反演的综合对比得到了可靠的电性结构模型.结合其他地质与地球物理资料,对电性结构模型进行分析得到冈底斯成矿带东段的矿床分布规律:矿床主要分布在地壳浅表的电性分界面附近;中地壳高导体可能通过上地壳隐伏的南-北向断裂控制着与地壳伸展作用有关的矿床;南-北向张性构造与东-西向逆冲-推覆构造的交汇部位可能是冈底斯成矿带东段重要的成矿区域;下地壳可能受到软流圈物质上涌的影响发生部分熔融,从而与中地壳的高导体共同影响地壳浅部的成矿作用.

The famous Gangdese metallogenic belt hosts many large ore deposits within its eastern part. In order to examine the electrical structure of this region, the magnetotelluric data covering the main ore deposits were carefully processed and analyzed. A reliable electrical model was obtained using both two-dimensional and three-dimensional inversions. Combined with other geological and geophysical observations, our electrical model reveals that the ore deposits distribution can be interpreted as： （1） Ore deposits are located in electrical boundaries in the shallow crust. （2） The conductors observed in middle crust may have played a key role in the distribution of ore deposits, through buried north-south direction faults in the upper crust. （3） We propose that the intersection regions of north-south extensional structures and east-west thrust can be regarded as important metallogenic zones. （4） The lower crust may have been influenced by the asthenospheric upwelling and then became partially melted. The partially melted lower crust, together with the conductors in middle crust may have controlled the mineralization process in the upper crust.