中国典型大型走滑断裂及相关盆地成因研究

Genetic analysis of typical strike-slip faults and related basins in China

扭动走滑构造是最常见的构造样式之一,走滑拉分盆地也是重要的含油气盆地类型。大地构造运动本质是岩石圈在区域应力场作用下的变形过程,然而真正将走滑断裂和走滑拉分盆地的成因以及它们的特征和岩石圈性质联系起来研究的文献却很少。显然,区域应力场是形成构造运动的前提条件,是外因,决定了运动的基本方式,如走滑、拉张或挤压等(构造类型);而岩石圈是构造运动的主体,是内因,其性质决定了形成构造的规模和具体形态(样式)。中国境内发育的大量走滑断裂体系和走滑盆地展示:古老克拉通上发育大面积分布的多条小位移走滑断裂体系,如塔里木盆地古生代走滑断裂体系;被后期热活动破坏了的克拉通发育多条扭动断裂系,例如华北克拉通东部的郯庐断裂系、兰聊—盐山断裂系、太行山东麓断裂系,并和区域拉张应力场耦合形成雁列式断陷群(如渤海湾盆地);相对较弱的古生代基底岩石圈发育大型单一走滑断层,如郯庐断裂东北段,并沿断裂发育一些相互独立的走滑拉分盆地;而在固结较差的中新生代造山带往往形成一条平直的大型走滑断层,例如阿尔金走滑断裂、海原断裂等。本文内因外因相结合,从扭动应力场和岩石圈强度以及流变学特征,建立了不同岩石圈性质下下部韧性层和顶部(上地壳或上地壳上部)刚性层之间的耦合作用机制以及扭动构造形成和演化模式,较好地解释了中国陆内发育的典型走滑断裂和走滑拉分盆地的成因机制。

Strike-slip faults and strike-slip pull-apart basins are widely distributed in China.At present,few researches are concerned with the large variety patterns of strike-slip faults related to the different rheological structures of the lithosphere.There is no doubt that the lithosphere is the subject of the tectonic movement driven by regional stress field,hence,the stress field determines the way of movement,such as strike-slipping,stretching etc.,whilst the nature of a lithosphere determines the movement scale and its specific form.Study of the large quantity and variety forms of strike-slip faults and basins show:many small strike-slip faults are distributed widely in the ancient craton,e.g.,the strike-slip fault systems of Paleozoic strata in the Tarim Basin;a“destroyed craton”develops multiple strike-slip fault belts,e.g.,the Tan-Lu fault belt,Lanliao—Yanshan fault belt and the eastern piedmont fault zone of Taihang Mountain in the eastern part of the North China Craton,and it can couple with the regional extensional stress field to form an echelon grabens(like the Bohai Bay Basin);large strike-slip faults(such as the northeastern segment of the Tan-Lu fault)develop on the relatively weak Paleozoic lithosphere,and its related independent strike-slip pull-apart basins.In the Meso-Cenozoic orogenic belt with poor consolidation,a linear large strike-slip fault is often formed,e.g.,the Altyn and Haiyuan faults.Based on the strike-slip stress field and the strength and rheological characteristics of the lithosphere,we establish the coupling mechanism between the lower ductile-layer and the top brittle-layer of lithosphere properties.On this basis,the formation and evolutionary models of strike-slip faults with different lithosphere properties are established to better explain the genetic mechanisms of typical strike-slip faults and related basins developed in China.