基于重力资料的马达加斯加岛及邻区盆地构造单元分布特征

A study of the distribution characteristics of basin tectonic units based on gravity data in Madagascar and its adjacent basins

随着非洲油气资源对外开放程度的加大,为我国海外石油勘探提供了机遇。非洲低勘探程度区油气地质资料匮乏,矿产资源丰富,为了利用地球物理资料研究马达加斯加岛构造特征,本文搜集了研究区已有的重力资料。根据布格重力异常,采用沉积层重力异常提取、最小曲率位场分离、归一化总水平导数垂向导数(NVDR-THDR)、曲率属性深度反演等识别出断裂信息和盆地边界,结合地质资料、地球物理资料,分析了主要断裂的地质及地球物理特征,确定了研究区内的断裂特征和盆地分布。通过研究,推断了研究区内一级断裂9条,二级断裂11条,断裂走向主要为NNE向、NE向和近NS向;结合断裂分布和前人研究现状,重新划分了马达加斯加岛塔姆塔夫盆地、穆伦达瓦盆地和马任加盆地的边界及内部隆坳构造格架,识别了7个坳陷和3个隆起,隆坳构造呈"两坳夹一隆"带状分布。该研究成果可以为马达加斯加岛及邻区油气和矿产资源勘探提供地球物理依据。

With offering the increasing opening exploration of oil and gas resources to the oversea exploration companies in Africa which remains in an early exploration stage,a good opportunity is provided for the companies in China.In this study,the gravity data of this research area were collected in order to study the tectonic characteristics of Malagasy Island,which has insufficient oil and gas geological data but abundant mineral resources.The faults and the boundaries of this basin were identified according to the response of the gravity anomaly to the sediments by the separation method of the minimum curvature,the vertical derivative of the normalized total horizontal derivative(NVDR-THDR)and the inversion of the depth of the curvature attribute,with Bouguer gravity anomaly.The geological and geophysical characteristics of the main faults were analyzed,and the distribution characteristics of faults and basins were determined,which were based on the geological and geophysical data.According to this research,there are 9 primary faults and 11 secondary faults inferred in this study area trending NNE,NE and nearly NS.The tectonics of Tamatave Basin,Morondava Basin and Majunga Basin were re-divided into 7 depressions and 3 uplifts combined with the distribution of faults from this study and previous studies,which are shown as a zonal distribution like"two depressions with one uplift".This research can provide geophysical information for exploration of oil,gas and mineral resources in Madagascar and its adjacent regions.