中国航磁大地构造单元划分

本文以我国截止到2011年基本覆盖陆域及部分海域的航磁数据编制的全国航磁系列图为基础,以航磁反映的区域磁场和磁性基底起伏特征为依据,汲取主流大地构造观的划分理念,以板块构造理论及大陆动力学思想为指导,以磁场反映的构造特征为切入点,结合重力、遥感、地质资料对中国陆域构造单元进行划分。大地构造单元划分4个级别:一级构造单元为陆块区和造山系,共划分出8个;二级构造单元为陆块、弧盆系和地块,共划分出32个;三级构造单元为盆地、坳陷带(区)和隆起带(区),共划分出85个;四级构造单元为隆起和坳陷,共划分出332个。本划分方案旨在为油气地质构造背景研究及油气勘探提供一份地球物理资料。文中重点讨论了一、二级构造单元界线厘定的磁场依据及与前人划分存在的不同之处,而三、四级构造单元完全依据磁场及磁性基底起伏情况进行划分,并在盆地和坳陷区给出了深度信息,这为油气勘探者提供了必要的技术支撑。同时,借助丰富的航磁信息提示出一些地质构造方面难解现象,供同行专家参考与讨论。

Subdivision of tectonic units in China based on aeromagnetic data

This research is based on the compiled aeromagnetic map of China that almost covers whole China''s continent and part of China''s sea areas since 2011 and the magnetic features and fluctuation of magnetic basement reflected by these maps. Learning from subdivision idea of mainstream tectonic views, guiding by theories of plate tectonics and continental dynamics, and taking the tectonic features reflected by magnetic field as key points, in combination with gravity, remote sensing and geological data, the authors divided the tectonic setting of China into four levels. Eight first-order tectonic units include continental block domains and orogenic systems; thirty-two second order tectonic units include continental blocks, arc-basin systems and land mass; eighty-five third order tectonic units include basins, depression belts (areas), and uplift belts (areas); three hundred and thirty-two fourth order tectonic units include uplifts and depressions. This subdivision provides basic geophysical data for geological and tectonic background research and oil gas exploration. In this paper, the authors discussed the magnetic evidence for delineating boundaries of the first and second order tectonic units, and compared them with previous subdivision of tectonic units in China. The third and fourth order tectonic units were completely defined by the feature of magnetic field and fluctuation of magnetic basement. The magnetic basement depth of basins and depression areas are provided in this study, which provides the necessary technical support for oil and gas prospectors. Meanwhile, aeromagnetic anomalies show some special characteristics that are not consistent with observed geological and tectonic features, which provide raw data for discussion of tectonic features of China.