摘要
准噶尔盆地的基底结构与属性一直是地学界关注的焦点问题之一.横跨准噶尔盆地北部,走向近东西的克拉玛依—喀姆斯特地震剖面提供了该盆地北部详细的地壳与上地幔顶部的速度结构与构造,特别是基底顶界面的速度.沿剖面发现了数条走向近南北的"H"型超壳断裂,它们没有明显的断差,断裂处反射系数明显降低,介质的Q值减小,推测具"开裂"性质;利用盆地内1:20万重磁数据完成了重磁联合反演,获得了沿剖面的地壳与上地幔顶部的二维密度结构与二维磁性结构.根据在一定深度范围内介质的速度-密度-岩性之间的关系,确定了盆地北部基底岩性分布.结果表明,准噶尔盆地北部的基底多处为基性和超基性物质,推测为深部(上地幔)物质沿超壳断裂进入地壳内部并对地壳物质进行改造的结果.这一推断得到盆地内部高磁性、高重力异常的支持,也与盆地具有较高的地壳平均速度相一致.综合其他地球物理与地质资料综合分析,给出了综合地质解释剖面,建立了准噶尔盆地北部基底结构与属性的动力学模型.
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.
出处
《地球物理学报》
SCIE
EI
CSCD
北大核心
2008年第6期1767-1775,共9页
Chinese Journal of Geophysics
基金
国家自然基金项目(40652002)
中国科学院知识创新方向性项目(kzcx3-sw-143)
中国科学院“百人计划”择优支持项目
国家973课题(G1999043301)联合资助
关键词
准噶尔盆地
天然地震转换波探测
重磁联合反演
基底结构
基底属性
动力学模型
Junggar basin, Seismic converted wave prospecting, Joint inversion of gravity with magnetism, Basement structure, Basement property, Geodynamic model
