内蒙古索伦地区辉长岩侵入体对上二叠统林西组烃源岩的影响

THE INFLUENCE OF INTRUSIVE ROCK ON THE EVOLUTION OF HYDROCARBON SOURCE ROCKS IN SUOLUN COUNTY,INNER MONGOLIA

内蒙古上二叠统林西组具有潜在的较大生烃能力.在烃源岩生烃过程中侵入岩体起到了一定的控制作用.因此针对索伦地区辉长岩侵入体对林西组烃源岩的影响进行了岩石学、有机地球化学等方面的研究,发现似层状辉长岩侵入体对围岩的影响范围仅相当于岩体自身厚度.在侵入界面的外侧,烃源岩具有变质分带现象以及有机质含量低、高熟和裂缝发育的特点,其根源是辉长岩体侵入时的较高温度和压力造成的.辉长岩侵入时带来的高温促进了烃源岩的热演化,并提高了有机质成熟度和生烃量;高压使围岩产生的大量裂缝为烃源岩排烃提供了通道.

The Upper Permian Linxi formation in Inner Mongolia has a great potential of hydrocarbon.During the evolution of hydrocarbon source rocks,the intrusive gabbro plays a controlling role.Based on the analyses of lithology and organic geochemistry,the influence of the gabbro body on the hydrocarbon source rocks of Linxi formation is studied.It is found that in Linxi formation in Suolun area,the influencing range of gabbro intrusion to the surrounding hydrocarbon source rocks is just as wide as the width of the intrusive rock itself.Outside the intrusive body,hydrocarbon source rocks are characterized by metamorphic zonation,with low organic matter content,high maturity and developed cracks,which are caused by the high temperature and pressure when the gabbros form.The high temperature greatly accelerates the thermal evolution of the hydrocarbon source rocks,increasing the hydrocarbon generating quantity.The high pressure produces a quantity of cracks,which provide channels for the expulsion of the hydrocarbon.