大别山高压-超高压岩石折返与扬子北缘构造变形的关系

Relation between exhumation of HP-UHP metamorphic rocks and deformation in the northern margin of the Yangtze Block.

大别山造山带及其"前陆"形成于三叠纪,是华北陆块与扬子地块经长期构造演化、最终碰撞的产物。研究表明,该"前陆"实际是扬子地块中部的九岭基底隆升带演化相关的褶皱-逆冲推覆构造带。综合横贯大别山造山带的大地电磁探测、宽角反射与折射地震探测、天然地震波(P波)层析成像研究、莫霍面地震反射图像,揭示大别山造山带及扬子地块北缘的地壳物性、速度结构、莫霍面错断、变形特征等,发现该区上、下地壳结构具有不一致性,总体表现为鱼骨刺状;并结合地表地质调查,推断扬子地块北缘深层向南逆冲的构造与大别山超高压变质岩的形成及折返过程密切相关,而浅部构造向北的逆冲推覆构造与大别山造山带向南的逆冲推覆构成对冲构造样式。最后,本文讨论了该区大地构造演化和背景,分析了其动力学机制。

The Dabie Orogen and its 'foreland' result from Triassic collision of the North China Continental Block to the Yangtze Block.This research reveals that the 'foreland' is in fact one fold-thrust fold belt related to the evolution of the Jiuling Basement Uplift Zone in the Central of the Yangtze Block.Combined with magnetotelluric sounding data,wide-angle reflection,seismic refraction,P-wave tomography,seismic reflection imaging of the MOHO surface,it reveals that the crustal architecture has difference between the upper and the lower crusts,like fish-bone shape based on rock properties,velocity,MOHO offset and deformation.It is deduced that the south-directed thrusting in the deep of the north Yangtze Block is closely related to the exhumation of the HP-UHP rocks of the Dabie Orogen based on surface geology and the mentioned-above architecture.However,the shallow structures are opposite thrust style composed of the north-directed thrusts of the north Yangtze Block and the south-directed thrusts of the Dabie Orogen.At last,the tectonic evolution and setting and deformation regimes are discussed and analyzed in this paper.