The Early Mesozoic NE-SW Extensional Model and Exhumation Processes at the Southeastern Margin of the Central Asian Orogenic Belt: Insights from the Strain and Kinematic Vorticity Analysis of the Sonid Zuoqi Ductile Detachment Zone
作者机构：East China Univ Technol Nanchang 344000 Peoples R China
出 版 物：《ACTA GEOLOGICA SINICA-ENGLISH EDITION》 (地质学报（英文版）)
年 卷 期：2024年第98卷第5期
页 面：1141-1153页
核心收录：
学科分类：07[理学] 0708[理学-地球物理学]
基 金：National Natural Science Foundation of China
主 题：strain simple shear pure shear kinematic vorticity ductile detachment zone METAMORPHIC CORE COMPLEX ANGLE NORMAL FAULTS INNER-MONGOLIA CRUSTAL GROWTH NORTH CHINA EVOLUTION ORIGIN REGION AGE
摘 要：The Sonid Zuoqi ductile detachment zone is located at the southeastern margin of the Central Asian orogenic belt (CAOB), striking EW and dipping to the S. The major rock type of the Sonid Zuoqi ductile detachment zone is mylonite derived from granite. The sequence of mylonite features is: (1) S and C foliations of mylonite, and (2) extensional crenulation cleavage (ecc) or C and the kinematic vorticity (Wk) value changed from 0.70 to 0.95 and from 0.37 to 0.69, respectively; the strain type of the mylonites within the Sonid Zuoqi ductile detachment zone is compressional to planar strain. The strong deformation mylonite and Halatu plutons yielded a zircon U-Pb age of 244 Ma and a zircon (U-Th)/He age of 214 Ma, respectively. Based on the strain and kinematic vorticity analysis, together with the zircon U-Pb and zircon (U-Th)/He ages and the regional tectonic background, the study area experienced three stage evolution: tangential simple-shear (244 Ma), simple-shear-dominated general shear represented by upper crustal extension (224 Ma) and pure-shear-dominated general shear represented by the Halatu pluton doming (214 Ma), which constrained the early Mesozoic NE-SW crustal extension at the southeastern margin of the CAOB. This NE-SW extension probably originated from the post-orogenic extensional collapse of the CAOB, subsequent exhumation being controlled by the far afield effects of the closure of the Mongol-Okhotsk belt.
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