内蒙古西部额济纳旗及邻区石炭系-二叠系烃源岩演化特征及影响因素

摘要

通过对额济纳旗及其邻区石炭系-二叠系烃源岩演化程度的平面展布和纵向分布特征的研究,结合对华力西中晚期-喜马拉雅期侵入岩露头分布和构造活动特征的分析,认为华力西晚期、燕山期侵入岩与构造活动对区内石炭系-二叠系烃源岩的演化程度影响较大,印支期侵入岩和构造活动仅对部分地区烃源岩成熟度有影响,喜马拉雅期构造活动对区内烃源岩演化程度无影响.区内石炭系-二叠系系阿木山组(干泉组)和下-中二叠统菊石滩组烃源岩过成熟主要受华力西晚期侵入岩和构造活动的影响,上二叠统哈尔苏海组烃源岩演化程度受燕山期侵入岩和构造活动的影响.明确了不同期次侵入岩和构造活动对石炭系-二叠系烃源岩演化程度影响的平面展布特征.综合研究认为,区内石炭系-二叠系烃源岩不存在区域变质,成熟度总体为成熟-高成熟,部分剖面(井)烃源岩演化程度较高(达到过成熟),是由侵入岩的热接触变质和构造活动的动力变质造成的.石炭系-二叠系沉积之后,岩浆活动和构造活动相对较弱的地区石炭系-二叠系烃源岩演化程度适中,为成熟-高成熟.%Based on the characteristics of planar and longitudinal distribution of the evolution degrees of Carboniferous-Permian hydrocarbon source rocks in Erin Banner and its vicinities, together with the study of the outcrop distribution of intrusive rocks of middle-late Hercynian to Himalayan period and their activity characteristics, the authors hold that the evolution degree of CarboniferousPermian hydrocarbon source rocks was mainly controlled by intrusive rocks and tectonic activity of late Hercynian and Yanshanian period. The intrusive rocks and tectonic activity of Indo-Chinese period only affected the evolution degree in several sections, and the intrusive rocks and tectonic activity of Himalayan period failed to affect the evolution degree. Over-mature hydrocarbon source rocks of Carboniferous-Permian Amushan Formation (Ganquan Formation) and Lower-Middle Permian Jushitan Formation were mainly affected by intrusive rocks and tectonic activities of late Hercynian period, and the intrusive rocks and tectonic activities of Yanshanian period affected Upper Permian Haersuhai Formation. On such a basis, the effects of different stages of intrusive rocks and tectonic activities on the plane distribution of evolution degrees of Carboniferous-Permian hydrocarbon source rocks are determined. It is considered that there existed no regional metamorphism of Carboniferous-Permian hydrocarbon source rocks, the general maturity was mature-highly mature, the evolution degree of several sections was higher (over-mature), caused by thermal metamorphism of intrusive rocks and dynamic metamorphism of tectonic activitiesy. The evolution degree of Carboniferous-Permian hydrocarbon source rocks in the region of weak magmatism and tectonic activities after Carboniferous-Permian was moderate (mature-highly mature).