摘要
本文据北京西山北岭向斜的有关地质资料,运用岩组分析、有限应变分析、递进应变分析以及弹塑性有限元模拟等方法进行综合分析,对北岭向斜的性质,成因机制,变形历史进行了讨论。认为北岭向斜的“弯月形”的主体构造格架是形成于印支期,在SN向的水平力的挤压下,出现以纵弯褶皱为主并伴有压扁作用的一次递进变形。该向斜核部NE向的燕山期构造变形对该主体构造格架的改造作用甚微。本文强调指出,应用综合分析法则是全面了解褶皱成因机制的有效途径。
Folds are the results of plastic progressive deformation of rooks. The major Indosinian struoture of the Beilin syncline in the Western Hills, Beijing, is a crescent-shaped synclinal structure Consisting of three hinge zones of fold—the Fenghuang shan syncline, the Nanjiao fold group and the Taipingshan syncline; and its Yanshanian core structure trends NE. Based on the geological structural features of the syncline, the nature, formational mechanism and deformation history of the syncline are studied in this paper using the comprehensive methods including the microstucture analysis, petrofabric analysis, finite strain analysis, progressive strain analysis of the syntectonic fibrous pressure shadows and twodimensional elasticoplastic deformation finite element analysis of rocks. Then the authors draw the conclusions: (1) The crescent-shaped major structure of the Beilin syncline was formed from flexural folding accompanied by flattening during the Indosinian progressive deformation marked by near-N-S horizontal compression. During this period, the hardened Fangshan dome at the eastern side of the Berlin syncline acted as a 'central object' of pressure shadows, thus causing the major structure to assume a crescent shape. (2)The NE-trending core structure of the syncline fomned during the yanshanian movement had little influence on the Paleozoic major structure. This paper emphasizes that only based on a wealth of geological data and using the Comprehensive methods, can we gain a Complete and detailed knowledge of the formational mechanism and deformation history of folds.
出处
《地质论评》
CAS
CSCD
北大核心
1991年第4期319-328,共10页
Geological Review
