内蒙古中部地区晚古生代地层接触变质作用研究初探

A study of contact metamorphism of Late Paleozoic strata in the Middle of Inner Mongolia.

内蒙古中部晚古生代地层由于中生代岩浆的侵入,部分发生接触变质,变质程度多处于沸石相或葡萄石-绿纤石相。通过对典型剖面的泥质岩石中的粘土矿物、伊利石结晶度以及镜质体反射率的分析,得出以下结论：（1）粘土矿物以伊利石和绿泥石为主,只在极少数样品中有伊蒙混层和蒙脱石,多数缺乏伊绿混层;（2）伊利石结晶度为0.22-0.40;（3）镜质体反射率Ro值为1.5-4.0。其结果表明：在岩浆侵入地区有小规模的接触变质,为极低级变质带,并未发生大规模的低绿片岩相的区域变质,而且这种变质只影响到晚二叠世以前沉积的地层和油气,分布范围有限。

Some of the Late Paleozoic strata in the middle Inner Mongolia developed zeolite-and/or prehnite-pumpellyite facies contact metamorphism due to the intrusion of Mesozoic magmas.Studies of clay minerals,illite crystallinity and vitrinite reflectance of typical profile indicate that（1） illite and chlorite are the dominant clay minerals,interlayered illite and smectite（I/S） or smectite are present in very few samples,and in most cases interlayered illite and chlorite（I/C） are rare;that（2） illite crystallinity ranges from 0.22 to 0.40;and that（3） the vitrinite reflectance values（Ro） are in the range of 1.5—4.0.The results suggest that only very low-grade contact metamorphism rather than large-scale greenschist facies regional metamorphism developed in the limited areas affected by the magmatic intrusion,and this low-grade metamorphism affected only sedimentary strata and oil resources formed before the Late Permian.