柴达木第三纪转换裂陷盆地形成演化及动力学

Evolution and dynamics of the Qaidam Tertiary transform rift basin in Qinghai

运用沉积体系组合 ,构造地层分析和岩浆热流体标志综合分析的方法 ,探讨了柴达木第三纪转换裂陷盆地形成演化及动力学过程 ,笔者认为 :柴达木第三纪盆地是以扩展裂陷为主的单型盆地 ,可划分为扇三角洲沉积体系 ,水下洪积扇 近岸浊流沉积体系 ,辫状河三角洲沉积体系 ,常态湖三角洲体系和湖泊沉积体系在湖盆演化的不同阶段 ,形成冲积扇 扇三角洲 滨浅湖 砾质辫状河沉积 ,近岸水下重力流 中深湖 扇三角洲 ,扇三角洲 中浅湖 河流三种湖盆充填形式。依据古构造运动界面和相应整合界面 ,将第三纪盆地划分为三个构造层序 ,分别对应于初始裂陷 ,伸展扩张裂陷和转换坳陷三个发展过程。柴达木第三纪转换裂陷盆地形成演化主要受控于地幔热柱的形成和衰减作用 ,同时喜马拉雅运动等运程应力作用对盆地的演化至关重要。

The evolution and dynamics of the Qaidam Tertiary transform rift basin in Qinghai are explored on the basis of the analysis of sedimentary system associations, tectonics and stratigraphy, and magmatic hydrothermal fluid in dicators. The Qaidam Tertiary basin is a simple basin created by extensional faulting-dominated processes, and may be composed of the following depositional systems such as fan delta, subaqueous pluvial fan-nearshore turbidity currents, braid delta, perennial lake delta, and lake depositional systems. During different stages of the basin evolution, there occurred three types of filling patterns of alluvial fan-fan delta-littoral and shallow lake-gravelly braided stream deposits, nearshore subaqueous gravity flow-deep lake-fan delta deposits, and fan delta-littoral and shallow lake-river deposits. Furthermore, the Tertiary basin may undergo three evolutionary stages of initial rifting, extensional faulting, and transform and subsidence, all of which led to the formation of three tectonic sequences identified with the aid of palaeotectonic bounding surfaces and associated conformities. The formation and evolution of the basin are considered to be constrained by the formation and waning of mantle plumes and stress processes of the Himalayan orogeny.