河北燕山地区地质构造基本特征

本文所称燕山没有严格的地质、地理概念,系泛指河北北部以及部分北京、天津,约为北纬39°40′—42°之间的广大范围。这一地区的地质构造特征先后有不少地质学者以不同的学术观点著文研究过,各有独创的认识和见解。在一比二十万区域地质调查和前人工作的基础上,本文试图反映该地区当前研究现状和探索一些地质构造现象,为今后进一步研究起一个“抛砖引玉”的作用。文中引用的资料主要为一比二十万区调成果和本队有关同志的专题性科研论文以及研究单位、大专院校等的论著。由于笔者水平所限,引用或分析不当之处,请批评指正。

BASIC CHARACTERISTICS OF THE GEOLOGICAL STRUCTURES OF THE YANSHAN AREA,HEBEI PROVINCE

The"Zanshan area"refers to northern Hebei,Beijing and Tianjin in general,covering a broad area largely between latitudes 39°40’—42°N. The area is characterized by complex geological structure and rich mineral resources. The exposed strata include the Archean,lower Proterozoic,Sinian suberathem,Paleozoic （the Silurian and Devonian absent） and Mesozoic. The magmatic activity has been widespread and strong,characterized by a multistage history in time and distinct orientation and zoning in space. There have been volcanic-intrusive processes of different characters at various geological stages from Archean to Cenozoic times. According to the history of geological development,the tectonic evolution of the area may involve four stages: the stage of formation and folding of the early Proterozoic geosyncline,the stage of inheritance and development of the late Proterozoic （Sinian suberathem） parageosyncline,the stage of continuous development of the Paleozoic platform and the stage of reactivation of the Mesozoic platform. The four evolutional stages exhibit marked changes in nature and direction of tectonic movements and in deformation. The main fracture zones in the Yanshan area have the following characteristics: generally the E-W zones are older,while the NE-NNE zones are younger （except a few older NE-NNE-trending fractures）; some E-W fracture zones gradually swing northwards from east to west;and the magmatic activity is very closely related to the fracture zones. The authors hold that regularities in time and space are available governing the formation and development of the geological structures of the Yanshan area located at northeastern margins of the north China plate. In time,pre-Mesozoic diastrophism was dominated by E-W trend,while postMesozoic diastrophism was dominated by NE-NNE trend; in space,the area has been affected by both the Mongolian plate to its north and the Pacific plate to its east,thus forming the peculiar fault-block structural features characterized by the intersection of two different directions.