华南、华北地块中生代构造演化与超高压变质岩的折返机制

Mesozoic Tectonic Evolution of the North and South China Blocks and Exhumation Mechanism of the Ultra-high Pressure Metamorphic Rocks

本文在讨论中国东部现有构造演化模式基础上,着重从华北与华南地块之间板块尺度的动力学过程剖析秦岭—大别中生代造山带构造演化,以及大别—苏鲁超高压变质地体的形成和折返过程。晚二叠世一中三叠世华南地块向华北地块持续挤压,陆壳大规模俯冲导致超高压变质作用的产生,而华北地块在晚三叠世至早保罗世发生快速逆时针旋转,使大别—苏鲁带由挤压转为张扭性环境,使得这一地区上地幔深度的超高压变质地体快速折返至下地壳。由于超高压变质地体侵位后,地壳结构、构造的差异,在南北地块的进一步挤压下,造成中国东部晚侏罗世—早白垩世郯庐断裂带的巨大左行剪切。

On the basis of a review of the available tectonic evolution models of eastern China, a new model for the Mesozoic tectonic evolution of the Qinling-Dabie erogenic belts and the process of formation and exhumation of the Dabie-Sulu ultra-high pressure (UHP) metamorphic terrane is proposed, with emphasis on the geodynamic process between the North and South China blocks at the plate scale. The South China block persistently pressed the North China block from the Late Permian to Middle Triassic; deep subduction of continental block resulted in UHP metamorphism. The quick counter-clockwise rotation of the North China block during the Late Triassic to Early Jurassic brought about transformation the tectonic environment in the Dabie-Sulu belt from compresso-shear to tenso-shear. As a result, the UHP metamorphic terrane at the upper mantle depth was quickly exhumed to the lower crust. As there exist differences in cructal structure and tectonics after emplacement of the UHP metamorphic terrane, further north-south compression resulted in great sinistral shear of the Late Jurassic-Early Cretaceous Tanlu fault in eastern China.