Cretaceous-Earliest Tertiary Basin Development, Deformation, and Magmatism in Southern Tibet: Implications for Pre-Indo-Asian Collision Lithospheric Structure

在碰撞事件之前，大陆碰撞造山带是如何受到沿会聚边缘运行的构造过程的预条件的？青藏高原被公认为碰撞造山带的原型，是研究这一问题的理想天然实验室，因为它包含了碰撞前的安第斯式弧形构造以及新生代碰撞构造的记录。青藏高原演化的一般模型首先假定地壳厚度和地幔结构的初始条件，这对模型的结果有很大的影响。然而，对这些假设的地质支持很少。这项研究综合了藏南拉萨地体广泛暴露的白垩纪和最早的第三纪盆地充填和火成岩的地质填图和构造、地层学、沉积学和年代学研究，以提供新的碰撞前应变史、盆地发展史、古地理、剥蚀和岩浆活动的约束。希望将这些新的约束条件与前人的研究相结合，形成一个统一的构造模式，为印亚碰撞前藏南地区的岩石圈结构提供现实的初始条件。这一结果应该对中亚新生代造山作用的模式以及总体上的碰撞造山作用具有广泛的意义。

How are continental collisional orogens preconditioned by tectonic processes that operate along convergent margins prior to the collisional events? The Tibetan plateau, which is generally accepted as the archetype of collisional orogens, is a perfect natural laboratory to study this question because it contains a record of pre-collisional, Andean-style arc-related tectonics as well as collisional tectonics during the Cenozoic. General models for Tibetan Plateau evolution begin with assumptions of initial conditions for crustal thickness and mantle structure that strongly influence the results of the models. However, geological support for these assumptions is scarce. This study is integrating geologic mapping and structural, stratigraphic, sedimentologic, and geochronologic studies of widely exposed Cretaceous and earliest Tertiary basin fill and igneous rocks in the Lhasa terrane of southern Tibet to provide new constraints on the pre-collisional history of strain, basin development, paleogeography, denudation, and magmatism. It is hoped that integration of these new constraints with previous studies will lead to a unified tectonic model that provides realistic initial conditions for the lithospheric structure of southern Tibet prior to the Indo-Asian collision. The results should have broad implications for models of Cenozoic orogeny in central Asia, as well as collisional orogenesis in general.