博格达山前褶皱带的再研究

A RESTUDY FOR PRE--BOGDA MOUNTAIN FOLDED ZONE

博格达山前褶皱带是我国最复杂、最雄伟的山前构造单元之一。作者从彩红外航摄照片的解译入手,结合对露头的观察和近年大量勘探资料的利用,重新研究了博格达山前地区的构造,订正和描述了这个以大型带状复式背向斜和叠瓦状断裂伴生的弧状构造系统;探讨了形成机制;指出这里发育的只是大型逆掩断裂,不是推覆体;燕山期的构造特别强烈的根本原因是山前坳陷没有固化基底;博格达山前坳陷是直接继承海西地槽的晚期坳陷渐进演变而成的,故是一种新类型。

Pre—Bogda mountain folded zone is one of the most complicate and grand tectonic unit at pre—mountain area in China. Starting with analysis of the aerial colour infrared photography and combining with the survey of outcrops and use of the vast exploration data in recent years, the writers restudied the structure of pre—Bogda mountain area and correctly described this arched tectonic system which is composed of large anticlinorium and synclinoria and imbricated faults. The writers also probed into the mechanism of formation of tectonic structure and pointed out that only many large reverse faults, rather than tectonic nappe, developed in here. The cardinal cause of these particular violent structure formed in Yenshan movement was the result of pre—mountain depression without a consolidated basement. The pre—Bogda mountain depression was formed by directly succeeded to the gradually evolution of late—Hercynian geosyncline, so it is a new type of pre—mountaln depression.