航磁所反映的祁连褶皱系区域构造及基底性质

THE REGIONAL TECTONICS OF QILIAN FOLDSYS TEM AND ITS BASEMENT PROPERTY REFLECT EDBY MEANS OF AEROMAGNETIC SURVEY

祁连山以它独特的构造格局和地貌景观展现在青藏高原的东北部。前人对它的区域构造特征以及大地构造分区提出过许多论著,但由于高原缺氧,人烟稀少,交通不便,给从事野外地质和地球物理调查带来了不少困难,在这样的地区开展航磁调查,其重要性是不言而喻的。 1983年我单位在祁连山地区进行了1:1,000,000航磁概查(面积约24万KM^2)。由于区内具有良好的地球物理前提,所以能够为研究区域构造和寻找矿产资源提供极为重要的资料(图1)。

In QiLian Shan area, We have carried out the aeromagnetic survey in broad outline of 1:1 , 000,000, which fills in the gaps of the aeromagnetic survey, and provides plenty of data for the research in the geological tectonics of this area and the Prediction of mineral resources.By means of the analysis of the magnetic field, We seem that the boundary line that consists the first-order tectonic unit reflect clearly on the southern fringe of Alashan fracture, on the northern fringe of Chaidamu fracture and Altun fracture etc. At the same time, we propose the new view on the exact division at the position of the Northern QiLian fracture, Altun fracture and the Northern fringe fracture of Chaidamu. The northern QiLianfracture may be drawed 20-30km away from Hei Heucourse-onthe south of QiLian County; The Altun fracture may be drawedalong the demarcation line passing through Suoerkuli-Alksai-Anxi;The northern fringe of Chaidamu fracture may be drawed alongthe demarcation line passing through Lenghu-Saishentengshan-Qinghainanshan etc.According to the data of the aeromagnetic survey and other geophysical prospection, A fault group in direction N-E that is aot recognized at present may be divided anew. Namely. The Yu-Men Zhen-Wulanbulak fracture, Zhang yeh-Muli xiang fracture andMen-Yuan fracture etc. They belong to the tenso-shear structure,which is simillar to the fracture in the direction N-W thet belongs to the products contemporaneously, all of which composed altogether the structural framework of this area. That the basement is composed of QiLian Shan fold System, not only is proterozoic Erathem, but also Archaeozoic Erathem.