摘要
四川盆地广元北部地区地质研究程度相对较低，文中通过野外地质调查和构造平衡演化剖面绘制及分析，对该地区构造特征及分区开展工作。研究认为：研究区构造变形强烈，西北地区主要发育复向斜、复背斜、倒转褶皱等构造，东南地区主要发育脆性特征明显的构造，深部发育双重构造和背冲断块等，即NW—SE向，变形特征整体表现为由塑性到脆性的转变；该地区构造演化可划分为多个阶段，二叠纪之前构造伸展和构造挤压发生多次转换，二叠纪之后基本上以构造挤压为主，在多期构挤压和伸展中，燕山运动至喜马拉雅运动造成的构造缩短量最大，各地质历史时期总共缩短了29.0 km，缩短率达到43.2%；根据构造变形强度变化及演化特征，研究区分为4个构造单元，即西北区、中北区、中南区和东南区，构造变形由韧性变形过渡到韧脆性特征和脆性变形，构造变形程度由强到弱。
Abstract
The degree of geological research in northern Guangyuan area of Sichuan Basin is relatively low. In this paper, the tectonic characteristics and tectonic zoning of the study area are carried out through field geological survey and the drawing of structural balance evolution profile. It is concluded that the tectonic deformation in the study area is strong. Synclinorium, anticlinorium and inverted folds are the main structures in the northwest region, however, the structures with obvious brittle characteristics are more common in the southeast region, besides, duplex structures and pop-ups can be found in the deep. That is, the whole tectonic deformation shows a transition from plasticity to brittleness in the NW￣SE direction. The tectonic evolution can be classfied into several stages. Tectonic extension and compression switched to each other for many times before Permian, while it was dominated by tectonic compression after Permian. In the multi-stage tectonic compression and extension, the largest structure shortening happened from Yanshan movement to Himalayan movement, and the total shorten amount in different tectonic periods was about 29.0 km, with a shortening rate of 43.2%. According to the change of tectonic deformation and evolution characteristics, the study area is divided into four tectonic units, namely northwest unit, north central unit, south central unit and southeast unit. Tectonic deformation transits from ductile deformation to ductile-brittle deformation, and even to brittle deformation, furthermore, the degree of tectonic deformation changes from strong to weak.
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