鄂尔多斯—中秦岭—四川东部的重力异常场与深部地壳结构

本文基于在跨越鄂尔多斯盆地、中秦岭造山带与渭河盆地、四川盆地东部长达1010km的综合地球物理探测剖面,实地采集的最新高精度重力位场数据,分析了不同构造单元的重力位场特征,构建了该剖面区域的地壳密度结构模型.进而通过分析地壳内部不同密度界面的横向差异特征及分区,确定了该剖面区域内的断裂分布,提出了鄂尔多斯盆地—中秦岭造山带—四川盆地的"盆-山-盆"型构造体系的新认识.

Gravity anomalies and deep crustal structure of the Ordos basin—middle Qinling orogen—eastern Sichuan basin

In this research, the latest field gravity data along a 1010 km-long geophysical profile crossing the Ordos basin, Weihe basin, Middle Qinling orogen and eastern Sichuan basin are collected. Based on this gravity data set, the gravity anomalies in different tectonic units are analyzed, the crustal density model along this profile is constructed, and the undulation and cross difference of density interfaces in crust and the distributional characteristics of faults around this profile are discussed.#br#The research results show that in the Ordos basin, the Bouguer gravity anomalies vary gently. The densities vary mainly in vertical direction. Interfaces are simple and smooth. And there are few faults. In the Weihe basin between the Qinling orogen and the Ordos basin, the Bouguer gravity anomalies are very low. There exists a gravity gradient belt corresponding to the big fault north of the middle Qinling oroge. The Moho interface uplift is about 10 km beneath this area. In the middle Qinling orogen, the Bouguer gravity anomalies vary strongly. Densities change in both lateral and vertical directions. The interfaces in crust are not so clear as those in its two sides. There are a lot of faults, and the Moho interface sinks a little. In the Sichuan basin, the Bouguer gravity anomalies vary smoothly. The density structure varies mainly in vertical direction. Interfaces are more simple and smooth, and there are few faults. These features are similar to those in the Ordos basin.#br#According to our research, there exist obvious differences between the middle Qinling orogen, Ordos basin and Sichuan basin in Bouguer gravity anomalies, crustal density models, undulation of interfaces in crust, and distribution of faults.#br#At last, this study suggests that the North Qinling fault and Ankang fault are the northern and southern contact zones of the middle Qinling orogen in the gravity profile. There exists a "basin-orogen-basin" distinctive tectonic system in the North China craton-middle Qinling orogen-Yangzi craton with its special resent characters of evolution.