柴达木盆地狮子沟-油砂山构造带变形特征及成因模拟

Deformation Characteristics and Genesis Simulation of the Shizigou-Youshashan Structural Belt in Qaidamu Basin

通过地震剖面解释、平衡剖面编制、构造物理模拟等综合研究,认为狮子沟-油砂山构造带具有垂向分层、走向分段变形特征。垂向上以T3地震反射层为界划分为深、浅两个构造层,深层变形样式为正断层组成的地堑、半地堑、反转半地堑组合,浅层变形样式为滑脱断层、冲起背斜构造组合。走向上可划分为狮子沟、油砂山、大乌斯三个构造段,其变形样式分别为深层反转、浅层滑脱垂向叠加组合;深层逆冲、浅层背冲垂向叠加组合;深层背冲、浅层逆冲叠加组合。根据不整合面的空间展布、生长地层的发育时间、构造叠加样式等特点,将狮子沟-油砂山构造带中、新生代演化过程划分为早-中侏罗世裂陷、晚侏罗世-晚白垩世挤压坳陷、古新世-始新世弱裂陷、渐新世-中新世弱挤压、上新世-第四纪强烈挤压等五个阶段。构造物理模拟实验证实,早期伸展构造受北北东向单侧拉伸作用控制,而晚期挤压构造受北北东-南南西向双侧不均衡挤压作用控制;膏盐层不均衡分布是影响滑脱变形的主控物质因素。

Our studies of the seismic profiles, balanced profiles as well as physical simulation show that the deformation of the Shizigou-Youshashan structural belt is characterized by longitudinal zonation and vertical stratification. Graben, half graben and inverted half graben are mayor structural styles within deep beds under seismic reflection layer of T3. Décollement structure including the faults and folds developed within the shallow layers above seismic reflection layer of T3. Three structure sections of the Shizigou, Youshashan and Dawusi are divided from west to east. Décollement anticline of the shallow layers superimposing reversed faults of deep layers formed in the west part of the Shizigou structure section. Detachment folds superimposing invertion structure developed in the east part of the Shizigou structure section. Back thrusting overlaping reversed faults formed in the Youshashan structure section and detachment faults overlaying back thrust faults developed in the Dawusi structure section. The structure evolution of the Shizigou-Youshashan structural belt can be divided into five phases, including chasmic stage from Early Jurassic to Middle Jurassic, compressional depression from Late Jurassic to Late Cretaceous, weakly rifting stage from Palaeocene to Eocene, weakly compressing stage from Oligocene to Miocene and intensely compressing stage from Plioeene to Quaternary. Results of physical simulation suggest that stretching structure in early stage is controlled by extensional stress related to sinistral strike-slip of the Ahyn Tagh Fault, and compressing structure in late stage is controlled by anisopleural compression stress related to uplifting of the Kunlun mountain. Maldistribution of gypsum rocks is key factor controlling the compressional deformtion.