桐柏山L构造岩形成机制构造解析及其对造山带演化的制约  

The Structural Formation Mechanism of L Tectonites in Tongbai Mountain and its Constraints on the Orogenic Evolution

作　　者：刘欢[1] 林寿发[1,2] 宋传中[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]加拿大滑铁卢大学地球科学系

出　　处：《地质学报》2016年第6期1098-1111,共14页Acta Geologica Sinica

基　　金：国家自然科学基金(编号41272222);中国地质调查科研项目<扬子板块北缘中生代构造演化与成矿>支持的成果

摘　　要：桐柏杂岩中发育一套典型的L构造岩,其构造位置位于桐柏造山带核部,被两条近似对称的韧性剪切带所夹持,北侧剪切带左旋,南侧剪切带右旋。由于L构造岩构造位置特殊,其位于剪切带、桐柏背形、桐柏穹窿等多种构造体的交叉部位,L构造岩的构造成因解析可以为桐柏造山带的形成演化提供重要制约。通过对桐柏造山带L构造岩的构造成因机理解析和其变形温压条件的研究,同时结合前人对桐柏山其它主要构造单元的研究,我们提出,桐柏山L构造岩的形成主要受其南北两侧两条韧性剪切带控制,传统意义的桐柏杂岩体白垩纪之前与南北一体的韧性剪切带沿近似东西方向发生管状韧性剪切,剪切作用形成了一套典型的L构造岩。L构造岩的形成指示了桐柏山单元可能经历了一期中下地壳物质的管状的韧性的向东剪切流动,后期白垩纪桐柏山核部的L构造岩经历了大规模的岩浆上升与浮力增加,该L构造岩同剪切带一起发生隆升但管状剪切构造特征并未被改造,随着不均匀隆升桐柏山出现了现今的几何学特征。L构造岩反映出管状剪切形成了现今桐柏造山带近东西向线状构造样式的主体。Within the Tongbai complex contains a typical rock unit called L tectonites,which is tectonically located within the core of the Tongbai orogenic belt and bounded by two symmetrical ductile shear zones（sinistral zone in the north and dextral zone in the south）.Because of the special tectonic position of L tectonites,which is located in the intersection parts of shear zones,Tongbai antiform,Tongbai doom and so on,the formation mechanism of the L tectonites can be provide an important constraints on better understanding the evolution of Tongbai orogenic belt.By the study of structural mechanism and deformation conditions of L tectonites,and along with previous research results of other main tectonic units in the Tongbai Mountain,it can be suggested that the formation process of L tectonites in Tongbai was mainly controlled by the two ductile shear zones in the north and south sides of the Tongbai complex.Before Cretaceous,Tongbai complex rock unit underwent near EW-trending pipy ductile shearing with the ductile shear zones,resulting in the formation of a set of typical L tectonites.The formation of L tectonites indicates the Tongbai orogenic belt might go through an eastward pipy ductile shearing of the middle and lower crust material,followed by a large-scale magmtic ascending and increasing buoyancy of L tectonites in the core of Tongbai Mountain in late Cretaceous.The L tectonites ascended with the shear zones but the main feature has not been transformed and presents today＇s geometry characteristics with uneven uplifting of the Tongbai Mountain.The L tectonites might reflect that pipy shearing gave rise to the main structural characteristics of Tongbai orogenic belt with a nearly east-west linear structure style.

关 键 词：桐柏造山带 L构造岩 管状剪切 桐柏杂岩 早白垩纪 

分 类 号：P542[天文地球—构造地质学]