147 / 2014-09-25 09:49:54

Structural Geometries And Kinematic Process Of Intracontinental Daloushan, Southeastern Margin Of The Tibetan Plateau: Implications For A Transfer Of Tectonism In The Yangtze Block Interiors

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The Daloushan located in the center of the upper Yangtze Continental Block, southeastern margin of the Tibetan Plateau, is thought to represent the main center of shortening resulting from eastward growth of the Tibetan Plateau and NW-ward thrusting of the Xuefeng Orogen. Structural data, fault-slip analysis and apatite fission-track ages are used to decipher the geometry, deformational characteristics and kinematic evolution of the Daloushan. The Daloushan is subdivided into two domains: the eastern domain, governed by W- to NW-verging thrusting and deformation with dextral transpression and the western domain, governed by S-vergent thrusting and deformation. Both domains experienced four episodes of deformation, synchronous with four-stage of post-Late Mesozoic denudation history. The latter is demonstrated by the eastward propagation of rapid cooling from ~20-5 Ma, at a rate of ~0.1 mm/yr. Two compressional, approximately E-W and S-N shortening directions generated sets of superimposed folds, (bedding perpendicular) conjugate joint sets. These sets could be attributed to NW-ward diachronous deformation of the Xuefeng Orogen with reactivation of boundary strike-slipping faults (i.e., S-N striking Nanchuan-Zunyi fault, and NW-striking Ziyun-Luodian fault) during the Early-Late Cretaceous and Late Cretaceous (~80 Ma), respectively. During the Late Paleogene (~40-20 Ma) NE-SW oriented, and during the Late Cenozoic (~10-5 Ma) NW-SE oriented shortening occurred in correlation to eastward growth of Tibetan Plateau. It thus suggests an intracontinental transfer of Paleo-Pacific Tectonic Domain to Tethys-Himalayan Domain occurred across the Daloushan, followed by disappearance of the paleo-Yangtze basin.