蔚县煤田地质构造的演化及特征

On the Evolution and Characteristics of Geologic Stracture in Yuxian Coal Field

燕山西段有许多中生代煤盆地。对这些煤盆地质构造演化和构造特征的研究,不仅可以了解侏罗系煤系地层的发育和分布规律,寻找新的煤田,而且对了解燕山西段地质构造演化和构造特征也具有重要意义。通过对区内构造层的划分和其演化特征的分析,区内地质构造演化可划分为三个阶段:1)太古代地槽发展阶段;2)元古代—古生代为地台盖层发展阶段;3)中生代—新生代为断块构造阶段。为了分析区内构造演化特征,我们还根据矿区内均匀分布的200多个钻孔资料,采用了多项式趋势分析的数学模型,利用计算机进行了趋势分析,拟合出1—4次多项系数。结果证明常规构造分析和数学地质分析完全吻合。矿区内地质构造特征可归为三点:(1)矿区地质构造为一复向斜。该复向斜受太古代古侵蚀面的古地理控制并经过后期构造旋回发育而成。(2)燕山运动把矿区改造成断陷盆地。喜山运动使断陷盆地继续发展。(3)中生代中晚期的辉绿岩侵入和侧向挤压,在矿区内产生一些规模较小的褶皱和断层。同时,我们还讨论了燕山西段侏罗系煤田的空间分布规律,各煤田中聚煤中心和富煤带的分布规律,和各煤田地质构造的后期改造。

Nowaday several coal basins formed at mesogoic era exist in the western seg- ment of Yanshan mountains.Through researching on the evolution and the characteristic features of the geological structure in these basins,we may understand the regularity of the developement and distribution of the Jurassic coal series so as to discover new coal fields, and also it is important in clarifying the evolution and characteristic features of the geologic structures in this segment. Based on both the division of structural laygers and the analysis of its evolutionary characteristics,the tectonic evolutional history in this area can be divided into three stages: (1)Archaean geosyncline developement stage; (2)Proterozoic—Palaeozoic platform cover developement stage; (3)Mesozoic—Cenozoic faulted block structure developement stage. In order to analyse the characteristics of the tectonic evolution in this area,on the ba- sis of more than two hundreds dirlling materials homogenously distributed in this coal field, we adopt the mathematic model of mutinomial trend analysis,and make the trend analysis by means of computer,thus draw up one to four oder multinomial coefficients.The results calculated prove that the mathematical geological analysis is entirely coincident with that of the traditional geologic approach. The characteristic features of the geological stucture in this area may be summarized into three main points: (1)The geological structure style in this area is a synclinorium,which was controlled by the palaeogeography of the Archaean palaeo—erosion surface and was formed by the later tectonic cycles. (2)The synclinorium in this area was transformed into faulted—subsided basin as the resuet of the Yanshan movement.The Hemalaya movement promoted the fault—subsided basin to develope Continuously. (3)The intrusion of the dialases in the mid—late mesozoic era altogather with the later- al compression gave rise to several folds and faults of smaller scale. Meanwhile,the authors also discuss on the distribution regularity both of the Jurassic coal series and of the coal accumulated centres and rich coal zones,as well as the later transformation of the geological structures in this western segment of Yanshan mountains.