内蒙古锡林郭勒地区上古生界极低级变质作用:伊利石和镜质体反射率的证据  

The very low grade metamorphism in the Upper Paleozoic in Xinlingol area of Inner Mongolia,NE China:Evidence from studies of illite and vitrinite reflectance

作　　者：胡大千[1] 韩春元[2,3] 马瑞[1] 刘越[1] 王静[3] 高正虹 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国矿业大学,北京100083 [3]中国石油华北油田公司,任丘062552

出　　处：《岩石学报》2012年第9期3042-3050,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41172039);国土资源部油气专项(2009GYXQ12-03)资助

摘　　要：本文使用D/max-2500X射线衍射仪研究了内蒙古锡林郭勒地区上古生界泥质岩石伊利石的成因标志,讨论了有机质镜质体反射率对变质温度的表征。研究区上古生界泥质岩石伊利石的标型特征为:伊利石结晶度分布于0.28～>0.77之间,平均值0.40;伊利石(白云母)多型以2M1型为主,2M1+1Md多型和1Md多型相对较少;伊利石(白云母)b0值变化于8.983～9.046之间,平均值9.019,指示其形成于成岩-极低级变质作用。有机质镜质体反射率具有示踪变质温度的作用,应用Barker and Pawlewiez(1986,1994)、Barker and Goldsteinl(1990)和Mullis et al.(2001)建立的镜质体反射率地质温度计,对研究区上古生界泥质岩石变质温度进行了估算,揭示古地温处于136～321℃之间,温度估算值主要分布在180～260℃之间,平均值为245℃,这表明研究区上古生界遭受了成岩-极低级变质作用,变质程度属近变质带。研究区上古生界泥质岩石的Ro值主要分布在1.01%～3.67%之间,表明有机质演化处于成熟-过成熟阶段,泥质岩石具有生烃的能力,部分层位可能具有形成油气资源的潜力。This paper deals with the genetical characteristics of illite in the Upper Paleozoic pelitic rocks in the Xilingol regions of Inner Mongolia using D/max-2500 X-ray diffraction and the relationship between organic matter vitrinite reflectance and metamorphic temperature.The typomorphic features of illite in the Upper Paleozoic pelitic rocks in the area under study are：crystallinity is 0.28~〉0.77,averaged at 0.40;illite（muscovite） polymorphism is dominated by 2M1,and 2M1＋1Md and 1Md polymorphisms are less developed;illite（muscovite） b dimension changes from 8.983 to 9.046,with an average of 9.019.These characteristics reveal the illite was formed at diagenetic to very low-grade metamorphic conditions.Organic matter vitrinite reflectance in the area can be used to reveal the metamorphic temperature.Using the vitrinite reflectance thermometer proposed by Barker and Pawlewiez（1986,1994）,Barker and Goldsteinl（1990） and Mullis et al.（2001）,the metamorphic temperature of the Upper Paleozoic pelitic rocks in the area has been estimated to be from 136~321℃,averaged at 245℃ and concentrated around 180~260℃.This indicates that the study area has undergone very low-grade metamorphism and the metamorphic grade belongs to anchizone.The Ro value of the Upper Paleozoic pelitic rocks in the studied area is mainly concentrated in 1.01%~3.67%,showing that the organic matter is at its mature to over-mature evolution stage and the pelitic rocks in the area was able to produce hydrocarbons.Hence,some horizons in the studied area have the potential of generating oil and gas resources.

关 键 词：上古生界泥质岩石 伊利石 镜质体反射率 地质温度计 极低级变质作用 内蒙古 

分 类 号：P588.3[天文地球—岩石学]