复合陆内山前冲断构造转换类型及其成因

Compound intracontinental piedmont thrust structure transformation and its formation mechanisms

方成名 赵利

FANG Chengming ZHAO Li

1. 中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126; 2. 山东农业大学 资源与环境学院, 山东 泰安 271018

1. Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China; 2. College of Resources and Environment, Shandong Agricultural University, Tai'an, Shandong 271018, China

复合陆内山前厚皮构造向薄皮构造的转换类型决定了中国中西部地区山前复杂冲断结构的形成和发育，任何单一构造模式均不能完全概括和解释构造转换及其结构差异形成的机制。通过深-浅层结构联合对比分析，依据构造位移向前传递扩展的形式及其产生的地质结构特征，将山前厚皮向薄皮构造的转换划分为过渡Ⅰ带、过渡Ⅱ带、过渡Ⅰ+Ⅱ带、无过渡带4类。过渡Ⅰ带、过渡Ⅱ带、过渡Ⅰ+Ⅱ带型通过基底面拆离滑脱实现厚皮向薄皮构造的转换，并视深层次滑脱层与边界条件形成叠瓦逆冲、三角带、双重构造等不同结构样式；无过渡带型主要以大型逆掩断层实现两者之间的突变式转换，无明显的基底面拆离滑脱，形成以大型推覆构造为主的结构样式。构造转换及其冲断结构差异的形成主要源自"镶嵌式"复合大陆因不同的深部地质结构与边界条件在板缘俯冲、碰撞作用力下产生多种形式的构造响应。过渡Ⅱ带、过渡Ⅰ+Ⅱ带型山前冲断构造形成遵循"壳内俯冲与反向拆离冲断"构造模式，无过渡带、过渡Ⅰ带型则分别符合"壳内双向俯冲与均衡隆升冲断"和"多层次基底拆离滑脱冲断"构造模式。

The transformation types from thick-skinned to thin-skinned structures in compound intracontinental piedmont controls the development of complicated thrust structures in central and western China. No single dynamic model can generalize and explain the causes of the multi-type thrust structure. Joint analysis of deep and shallow structures shows that there are four types of transformation from thick-skinned to thin-skinned structures in the piedmont of central and western China. These are named transition zones Ⅰ, Ⅱ, Ⅰ+Ⅱ and the non-transition zone, according to the form of forward transfer and expansion of tectonic displacement and the geological structure it produces. The four transformation types have specific structural characteristics. The first three types are mainly converted by basement detachment and slippage. Due to the development of a deep slippage layer and different boundary conditions, different structural styles such as imbricate thrusting, triangular zone and double structure are formed. As to the non-transition type, overthrust faults accommodate the abrupt transformation between thick-skinned and thin-skinned structures, without obvious basement detachment or slippage. Large-scale nappe structure is the main structural style of this transformation type. The difference of transition type and thrust structure is mainly due to the different intracontinental deformation responses of different deep geological structures and boundary conditions in the compound continents with multi-continental blocks splicing together under the action of plate margin subduction or collision. The formation of transitional zone Ⅱ and transitional zone Ⅰ+Ⅱ piedmont thrust structures follows the structural model of "intracrustal subduction and reverse detachment thrust", while the non-transitional zone and transitional zone I conform to the structural model of "intracrustal bidirectional subduction and balanced uplift thrust" and "multi-level basement detachment and detachment thrust" respectively.

国家科技重大专项"大型油气田及煤层气开发"（2017ZX05005-001）资助。

https://doi.org/10.11781/sysydz201906791