滇西三江地区中生代盆—山动力学耦合初论

盆地和相邻造山带在动力学机制上的耦合关系是当前大陆动力学研究的热点,滇西三江地区中—新生代盆山格局是开展这一研究的典型实例。晚三叠世思茅盆地从前陆盆地向裂谷盆地的转换过程,与造山带演化的主碰撞阶段和后碰撞阶段相关,是研究的切入点。通过分析研究区中—新生代盆—山耦合过程及其沉积响应、地球物理和岩浆岩地球化学特征来探讨其深部动力学过程的一致性和连续性。研究表明三江地区中—新生代盆山演化经历了"盆转山"(T1—T2)、"山控盆"(T3—E1)以及盆—山共变(E2—Q)三个阶段;思茅陆相断陷湖盆通过盆地内沉积相迁移、层序建造、基底变形,尤其是沉积旋回来响应深部动力学过程;岩石圈速度结构剖面揭示出思茅盆地的下地壳和岩石圈地幔P波速度增大,莫霍面加深;结合思茅盆地两侧中生代岩浆岩活动期次和地球化学特征,底侵作用、拆沉作用和俯冲板片断离作用可能是盆山动力学耦合的深部作用模式。

Initial Exploration to Mesozoic Basin-Orogen Dynamical Coupling of "Sanjiang" (Nujiang River-Jinsha River-Lancang River)Region, Western Yunnan

The coupling relations on dynamic mechanism between basin and adjacent orogenic belt are a research front of continental dynamics. The current typical basin-orogen pattern of the Sanjiang region (means three rivers, i.e.: Nujiang River-Jinsha River-Lancang River) is an ideal region to carry out this study. The conversion from foreland basin to rift basin of the Simao basin is involved with orogenic evolution. Therefore, it could be a breakthrough point of this research. The research methods include analysis to basin-orogen coupling process and its sedimentary responses, geophysics and geochemical characteristics of igneous rocks. Studies have shown that its Meso-Cenozoic basin-orogen evolutional history include three phases: basin orogen transition(T_1-T_2), orogen control basin (T_3-E_1) and basin-range covariation (T_3-E_1); The Simao lacustrine basin responds deep dynamical process by facies migration, sequences formation, deformation of basement and sedimentary cycle; the velocities structure section of lithosphere reveals that lower crust and lithosphere mantle under the Simao basin have a higher P wave velocity, and the Moho interface seems deeper; in addition, combining with characteristics of magmatic movement sequence and geochemistry, writers consider that basic magma underplating, lithosphere delamination and subduction slab-off might be the deep dynamical models of the basin conversion.