Discussion on the basement structure and property of northern Junggar basin
准噶尔盆地北部基底结构与属性问题探讨

The basement structure and property of the Junggar basin has long been a focus for geoscientists.A comprehensive geophysical profile,running from Karamay to Karmst in nearly EW direction and located at the northern part of the Junggar basin,provided with a detailed velocity structure of the crust and uppermost mantle,especially the velocity at the top of the basement.Along the profile,several "H" type faults have been located,which cut through the crust without obvious dislocation and have a low reflectivity and Q value at the faults,inferred as extensional faults.A joint inversion of gravity with geomagnetism along the profile was carried out and 2D density and 2D magnetic intensity of the crust and uppermost mantle were obtained using 1:200000 gravitational and geomagnetic anomalies in the Junggar basin.Furthermore,the rock types of the basement for the northern part of the Junggar basin were determined by using the relation among velocity,density and rock type at a certain depth range.The result shows that several sections of the basement along the profile are basic to ultra basic materials,indicating that the mass of the uppermost mantle intruded into the crust and mixed with crustal material.This inference is supported by high velocity,high density and high geomagnetic intensity of the crust.Combining with other geophysical and geological data,we developed a comprehensive geological interpretation profile,which shows a geodynamic model for the structure and property of the northern Junggar basin.