鲜水河断裂带南段深部电性结构特征研究

摘要

通过对新都桥-小金剖面的大地电磁测深及重磁实测资料研究,结合区域地质资料,对鲜水河断裂带南段及邻区深部构造、壳内高导层、电性结构与历史地震的关系进行了研究.结果表明:(1)鲜水河断裂带深浅表现出不同特征,浅部是以地壳脆性-剪切带为主的断裂系统,深部是以走滑型-壳幔韧性剪切带为主的断裂系统,断裂呈花状形态,深部到达上地幔;(2)在丹巴构造带及鲜水河断裂带的中下地壳,广泛发育壳内高导层,其分布具有不均匀性,且与断裂带构造活动有关;(3)在鲜水河断裂带的走滑剪切作用下,上地壳物质发生原地重熔产生花岗岩浆是折多山花岗岩形成的主要机制;(4)鲜水河断裂带地震发生机理与塑性软弱层密切相关,受塑性软弱层拖拽作用,应力区集中在高阻体脆性介质内部靠近断层一侧,使得岩石破碎而发生地震.%Based on research of measured data of the magnetotelluric and gravity-magnetic profile of Xinduqiao-Xiaojin,combined with regional geological data,the relationship between deep structure,crustal conductivity layer,electrical structure and historical earthquake of the southern section of the Xianshuihe fault zone and adjacent areas is studied.The results are shown as follows.First,the Xianshuihe fault zone shows different forms in deep and shallow parts.The shallow fault system is mainly a brittle shear zone in the crust and the deep fault system is mainly strike-slip ductile shear zones in the crust and mantle with a flower morphology and reaching the upper mantle in the deep part.Second,crustal conductivity layers are widely developed in the middle and lower crust of Danba tectonic belt and Xianshuihe fault zone,indicating inhomogeneity,related to the fault movement.Third,remelting of the upper crust may be the main mechanism of Zheduoshan granite.Fourth,the earthquake mechanism is controlled by the fault zone in the Xianshuihe fault zone and closely related to the weak layer as well.It is mainly controlled by shearing of strike-slip faults between plates in the shallow part.The stress is concentrated within the high resistance and brittle medium near the fault,where medium changes in the turning points,resulting rock breaking and earthquakes.