科研之友
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摘要
The Tongbai orogen in the middle of the Qinling-Tongbai-Dabie-Sulu orogenic belt is one of the most important portions for understanding the tectonic framework and evolution between the Sino-Korean and Yangtze cratons. In this paper, we report new U-Pb and Ar-40/Ar-39 age data from the Tongbai complex in order to constrain the extensional processes and late exhumation of HP/UHP terranes. Zircon U-Pb dating of different rock types in the Tongbai complex reveals the intrusion of volumino is granitic magmas at 139 +/- 2 Ma, contact metamorphism and migmatization of the Triassic metamorphic enclaves at 136 +/- 2 Ma, and syn-deformational emplacement of pegmatite veins at 131 +/- 1 Ma. Ar-40/Ar-39 thermochronology on hornblende, muscovite and biotite coupled with available structural data indicates two episodes of deformation (cooling) at ca.135-120 Ma and ca. 100-90 Ma. The predominant ductile shearing structures, including regional subhorizontal NWW-SEE stretching lineations in the whole Tongbai complex and sinistral and dextral shear senses along its northern and southern boundaries, were formed during the first deformational episode. Regionally, the Cretaceous magmatism, metamorphism, migmatization, deformation and cooling processes in the Tongbai complex are comparable with those in the Dabie-Sulu region, suggesting the evolution of the Tongbai-Dabie-Sulu orogen within the same extensional tectonic regime during this time. The Cretaceous extensional event is thought to have resulted in the lateral eastward extrusion of the Tongbai-Dabie terrene and exhumation and final exposure of the HP/UHP rocks from mid-upper crustal depths.
- 出版日期2012-3-30
- 单位中国地质科学院地质力学研究所
