鄂尔多斯盆地北部山西组、下石盒子组物源分析

ANALYSIS OF THE MATERIAL SOURCES OF SHANXI FORMATION AND SHIHEZI FORMATION IN NORTH E'ERDUOSI BASIN

随着鄂尔多斯盆地北部上古生界二叠系碎屑岩气藏的不断发现 ,其物源引起了人们特别的关注和重视。应用数理统计的方法 ,结合轻重矿物、岩屑组成的分布特征 ,并与源岩对比 ,分析探讨了该地区二叠系山西组、下石盒子组的物源问题。分析结果表明 :①盆地西缘地区与西部苏里格庙地区是截然不同的两个物源体系 ;②盆地西部苏里格庙地区与中东部地区物源母岩有着较强的亲缘性 ,但同时也存在着一定的差异性 ,即西部地区母岩以沉积变质岩 (石英岩 )和中基性火山岩为主 ,中东部地区主要以酸性侵入岩为主。这些分析和结论不但澄清了鄂尔多斯盆北部上古生界物源研究中长期存在的问题 ,而且使我们对盆地西部到东部的山西组和下石盒子组碎屑成分含量变化规律有了新的认识。

Because of discovering successively clastic rock gas reservoirs in Permian of Upper Paleozoic in North E'erduosi Basin,the special attention has been paid to the material sources of these reservoirs.By applying mathematical statistics and in combination with the distribution characteristics of light & heavy minerals and debris composition,the source areas of the Shanxi Formation and Shihezi Formation of Permian in the region are analyzed in contrast with native rocks.The analytic results show that ① the material source system at west basin margin area is obviously different from that at Suligemiao area in the west part of the basin;and ② the native rocks at Suligemiao area have a close affinity with those in the middle-east part of the basin,however there is still a certain difference,i.e.the native rocks in the west part are mainly composed of sedimentary metamorphic rocks (quartzite) and neutral-basic igneous rocks,and those in the east part are mainly composed of acidic intrusive rocks.Not only the problems existing in the research on the material sources of Upper Paleozoic in North E'erduosi Basin have been settled but also a new knowledge of the change law of dedris content in Shanxi Formation and Lower Shihezi Formation from west to east in the basin is achieved on the basis of these analyses and conclusions.