华南上地壳速度分布与基底、盖层构造研究

对华南地区有代表性的几条宽角地震剖面进行了研究,利用初动到时资料拟合剖面地带地壳上部详细的速度分布,结合其他地球物理资料与地质资料对地壳基底和沉积盖层的构造进行了综合解释. 结果表明,浙-闽-粤东部地区在地壳基底上分布一系列中生代火山岩断陷盆地,火山岩盖层厚度变化为1000-4000m. 浙西-皖南以及湘-赣地区地壳基底起伏较大,盖层主要为古生界,并发育许多受基底形态与边界断裂控制的小型中生代白垩纪盆地. 华南西部的楚雄盆地为一构造复杂的深坳陷,其中侏罗-白垩系的厚度超过10km,并被分割为东部斜坡和西部坳陷两个单元,而西部坳陷又被一中央隆起分割为东、西两个更次级的凹陷. 区内一些主要的断裂构造在速度等值线图上均有明显的反映,如东部的江绍断裂、莲花山断裂和吴川-四会断裂以及西部的程海断裂和绿汁江断裂都是重要的构造分界,此外众多的基底断裂多是盆地与隆起的边界.

A STUDY ON VELOCITY DISTRIBUTION IN UPPER CRUST AND TECTONICS OF BASEMENT AND COVER IN SOUTH CHINA

A study on five representative wide-anger seismic profiles in South China is completed. The fine velocity distribution patterns are fitted with the travel times of first arrive Pg waves. Combining with other geophysical data and geological data, we make a synthesis explanation for the tectonics of basement and cover. It is proved that some fault basins infilled with Mesozoic volcanic rock above the basement are distributed in the eastern region of Zhejiang, Fujian and Guangdong provinces and the thickness of the volcanic rock layer is 1000-4000m. In the regions of western Zhejiang, southern Anhui, Hunan and Jiangxi Provinces, the basement surges obviously and the cover is mainly Palaeozoic group, and some Mesozoic Cretaceous smaller basins controlled by boundary faults develop there. The Chuxiong basin in western South China is a deep depression with complex structure, in which the thickness of Jurassic-Cretaceous systems is over 10km. This basin is divided into two parts of eastern ascent and western depression, and the western depression is farther divided by a center uplift into two smaller deep depressions. Some Main faults in the researched region are reflected clearly in the contour velocity diagrams. Jiangshan-Shaoxing fault, Lianhuashan fault and Wuchuan-Sihui fault in the eastern region, and Chenghai fault, Luzhijiang fault in the western region are all the important tectonic boundaries, also flock basement faults are primarily the boundaries of the basins and the uplifts.