柴达木盆地柴中隐蔽断裂带的成因及其深部找藏

摘要

Qaizhong fault zone located in the central Qaidam Basin trends EW. The Indian plate underthrust Eurasian plate intensively in multi-stages during Himalayan period and Qaidam Basin remained in regional compression background. Based on analysis of palaeogeographic changes, basin superposition and isotopic age information for the Arkin, Qilian and Kunlun Mountains around the basin Qaizhong fault zone may be generated contemporanously with the break up of Proterozoic Rodinia ancient continent. They all belong to the huge EW-trending Dabie Mountain-Qinling-Kunlun orogenic belt. Qaidam Basin was exposed to Jinning, Caledonian, Hercynian and Yanshan movement, especially the Himalayan orogeny and the early structures are obscured by the later ones in this area. Combined with the very thick Quaternary cover (12-17km) and other factors Qaizhong fault zone is of hidden and complex feature and is often ignored.Formation of the fault zone is closely related to the deep crust-mantle processes to which. consistence of the EW trending Qaizhong fault with the boundaries of double-shell high-conductivity layer and crustal high-conductivity layers in the area attest. By using the relationship of high-frequency magnetic anomalies with saitbed and basal fault zone, we can effectively search for deep gas fields; it is hopefully to discover terrestrial or marine oil-gas reservoirs at the intersection region of Qaizhong fault and fault zone at the basin boundary.%柴中断裂带位于柴达木盆地的中部,呈EW向展布,由于喜山期印度板块多期次向欧亚板块强烈俯冲,致使柴达木盆地处于挤压的区域构造背景中,通过古地理变迁、盆地叠合研究和盆地周缘的阿尔金山、祁连山、昆仑山大量同位素年龄资料分析得知:柴中断裂可能与元古宙罗迪尼亚(Rodinia)古陆裂解同期生成,同属大别山-秦岭-昆仑山EW向巨型造山带的范畴.因柴达木盆地经历了晋宁、加里东、海西和燕山运动,特别是喜马拉雅造山运动影响,导致了该区晚期构造掩盖了早期构造特征,再加之极厚的第四系覆盖(12～17km)等因素,致使柴中断裂带具有其隐蔽性和复杂性,常被人们忽视.它的成因主要是与深部壳幔过程密切相关,区内双壳高导层与壳内高导层的分布界限,正和柴中断裂带走向(EW向)一致,这是有力的佐证.运用高频磁异常与膏盐层和基底断裂带的关系,可以有效地寻找深部气田.在柴中断裂带与盆地边界断裂的交汇处有望寻找陆相和海相油藏.