宽裂谷的构造样式与成因机制

宽裂谷是一类重要的大陆伸展构造样式,野外工作与物理模拟、数值模拟相结合是研究宽裂谷构造样式的主要方法。国外学者对宽裂谷进行了较多研究,集中于其形成与持续时间、构造样式、岩浆活动特征等方面。试图在广泛的国内外文献综合分析的基础上,介绍宽裂谷的定义及其构造特征,通过盆岭省和爱琴海盆地的地质剖面验证宽裂谷构造样式,进而分析其成因机制。宽裂谷的形成受控于区域性的低角度拆离面,它同时控制了变质核杂岩的发育,拆离面之上发育高角度断层控制的掀斜断块。控制宽裂谷构造样式的参数主要有:伸展应变速率及地壳组成、初始的地壳厚度和岩石圈热状态、岩石圈的机械不稳定程度、岩石圈抗张强度与重力的对比关系。动力学机制上,宽裂谷可能主要由被动裂谷成因机制控制;运动学机制上,宽裂谷通常由简单剪切或简单剪切与纯剪分层拆离机制控制。以期对认识中国东北地区宽裂谷系统的构造样式与成因提供帮助。

Structural Style and Genetic Mechanism of Wide Rifting

Wide rifting is one of an important continental extension modes,and field work combined with numerical and analogue modeling is main method to investigate wide rifts. Foreign scholars did lots of research on wide rifts,which mainly focused on the timing and duration of deformation processes,structural styles and magmatism. This paper,based on the study of a great deal of relevant publications,introduces the definition and structural characteristics of wide rifting,which will be verified by geologic profile of both Basin and Range and Aegean regions,and then analyses its genetic mechanism. The formation of wide rifts is dominated by a regional low-angle detachment,which also controlled the development of metamorphic core complexes,above which formed higher-angled block faulting. Parameters controlling the modes of wide rifting mainly contain:The strain rate and crust compositions,initial crustal thickness and thermal conditions,the level of mechanical instability of lithosphere,the competition between the total resistance of the lithosphere and the gravitational forces. Wide rifting may be mainly explained by passive genesis from dynamic mechanism,and it can be controlled by simple shear or decoupled extension. Through this study, we try to improve our understanding of structural styles and genetic mechanism of wide rift system in northeast China.