右江复合盆地的沉积特征及其构造演化

THE SEDIMENTARY CHARACTERISTICS AND STRUCTURAL EVOLUTION OF THE YOUJIANG COMPOSITE BASIN

位于华南褶皱带南缘的右江盆地,其发展可分为两个不同的阶段。它的轮廓和结构,与NW向及NE向同沉积断裂关系密切。盆地内的沉积物,分别由特征不同的非补偿性和补偿性沉积相组成两个双层结构。盆地内火山活动发育,也明显的分为两个阶段。海西期,古特提斯洋的发展使哀牢山洋盆开裂,导致了右江地区在拉张应力条件下出现若干NW向裂陷带,这时的盆地具有大陆边缘裂谷特点。东吴运动后开始的印支期,区域应力条件发生变化。滨大平洋构造的发生,使盆地轮廓和结构发生明显变化,与此同时开始的哀牢山洋盆向NE方向的俯冲消减作用,使盆地在新的挤压条件下再次发生张裂和拗陷。进入了弧后盆地发展阶段。印支期末,盆地封闭。

Situated on the southern margin of South China fold belt, the Youjiang basin has gone through two different development stages. Its outline and structure are closely associated with NW-trending synsedimentary faults. The basin consists of compensative and non-compensative sedimentary facies which form two double-layer structures. The volcanisms in the basin are well developed and are obviously divided into two stages: Hercynian and Indosinian periods. In the Hercynian period, the development of Palaeo-Tethys Ocean made Ailaoshan ocean basin split, which gave rise to a number of NW-trending rift belts in Youjiang area under the conditions of tensile stresses. So, the basin has the characteristics of continental marginal rifts. In the Indosinian period, the conditions of regional stresses were changed. The formation of marginal-Pacific tectonics resulted in much change in the outline and structures of the basin. Meanwhile, the subduction of Ailaoshan ocean basin in the northeast resulted in extension fractures and rifts again in the basin under the new conditions of compressions, and the basin was at the growth stage of back-arc basin. At the end of Indosinian period, the basin was closed.