试论中国西部陆内俯冲型前陆盆地的基本特征

Discussion on essential characteristics of intracontinental- subduction type foreland basins in western China

中国西部陆内前陆盆地大多是由陆内(C-型)俯冲形成的。陆内(C-型)俯冲是中国西部大陆构造的一种特殊构造形式,发育在陆内褶皱山系与前陆盆地的结合部位,形成于中国大陆拼接之后。微陆块拼接构成的中国大陆构造是中国西部前陆盆地结构复杂的重要因素;陆内(C-型)俯冲是C-型前陆盆地与C-型造山(冲断)带物质流和能量流循环的内在原因;特提斯洋关闭和印度板块持续推挤是中国西部前陆盆地形成的构造动力学背景。中国西部前陆盆地在成因机制、盆地类型、地质特征及油气成藏等许多方面,与典型的前陆盆地有很大差别。陆内俯冲型(C-型)前陆盆地具有陆相烃源岩、低孔渗性砂岩储层、油气圈闭多样、以喜山期为主多期成藏的特点。

Most of the intracontinental foreland basins in western China were the results of intracontinental subduction (C-subduction), which was a unique tectonic form in western China and developed in the conjunction areas between intracontinental folded mountain systems and foreland basins after the matching of the continents. Tectonics in China's Mainland resulting from matching of micro-continental blocks was the major cause of the complex structures of foreland basins in western China. Intracontinental subduction (C-subduction) was the intrinsic cause of circulation of mass flow and energy flow in type-C foreland basins and type-C orogenic belt (thrust belt). Closing of Tethys and continuous compressing and squeezing of Indian plate were the tectonic dynamics background for the formation of foreland basins in western China. The foreland basins in western China are very different from those typical foreland basins in respects of genetic mechanism, basin types, geologic features and hydrocarbon accumulation. Foreland basins of intracontinental subduction type (type-C) are characterized by continental source rocks, low poroperm sandstone reservoirs, various traps and multiple reservoiring stages mainly in Himalayan period.