气候变化领域集成服务门户(CCPortal): Middle Miocene Onset of the Litang Fault System Records Kinematic Change in Eastern Tibet

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DOI	10.1029/2023TC007931
	Middle Miocene Onset of the Litang Fault System Records Kinematic Change in Eastern Tibet
	Cao, Kai; Zhang, Di; Shen, Xiaoming; Zhang, Junfeng; Wang, Dun; Xu, Yadong; Wang, Guocan
发表日期	2023
ISSN	0278-7407
EISSN	1944-9194
卷号	42 期号:12
英文摘要	The similar to 400-km-long Litang fault system (LTFS) is a major intracontinental strike-slip fault inside the Chuandian block, eastern Tibet, but its evolution and role in accommodating the India-Asia convergence remain poorly known. Structural analysis shows that the LTFS splits into 5 strands as a left-lateral, right-stepping en-echelon pattern formed under NW-directed compression, subsequently reactivated by transtensive faults under NNE-directed extension. Displaced geological and morphological markers yield a cumulative left-lateral offset of 28.9-42.8 km. Inverse thermal-history modeling of thermochronological data of the faulted rocks reveal accelerated cooling at 38-35 Ma, 16-13 Ma, and 7-5 Ma. The late Eocene rapid cooling is ascribed to the reactivation of the Garze-Litang suture. Rapid cooling events at 16-13 Ma and 7-5 Ma record the onset of transpression and transtension of the LTFS, respectively, yielding a geologic slip rate of 2.6 +/- 0.7 mm/yr. Both bifurcated geometry and slow slip rate of the LTFS since 16-13 Ma indicate diffuse deformation inside the Chuandian block, contrasting with strain localized on fast-slip strike-slip faults on the block margins. This implies a significant kinematic transition in the middle Miocene, such that the extrusion of the segmented mega-blocks has been accommodated by both localized and distributed deformation in eastern Tibet. This tectonic transition could be explained by a change in lithospheric rheology from an earlier rigid state to a viscous state underneath the Chuandian block due to thermal weakening of the lower crust. We thus reconcile the end-member geodynamic models of block extrusion and lower crustal flow in late Cenozoic times. The role of the Litang fault system in Chuandian block, eastern Tibet in accommodating deformation from the India-Asia convergence remains unclear due to the lack of robust constraints on its deformation history. Structural analysis shows that the fault system has 5 left-lateral splays formed under oblique compression and later reactivated in transtension. Displaced lithology and landforms yield a cumulative left-lateral offset of 29-43 km. Thermochronology of apatite and zircon crystals, which measures how fast rocks have cooled as they move from depth to the surface, reveal that rock cooling during 16-13 Ma and 7-5 Ma were controlled by uplifted rocks related to the onset and propagation of the fault system. The long-term slip rate is 2.6 +/- 0.7 mm/yr. The bifurcated pattern with low slip rate of the Litang fault system indicates distributed deformation inside the Chuandian block concurrent with localized deformation on the block margins since similar to 16-13 Ma. This could be explained by a hybrid geodynamic model of micro-block (mega-block sliced by strike-slip faults) extrusion and weakened lower crust preceded by mega-block extrusion accommodated by terrane-bounding strike-slip faults. We propose that this kinematic change has occurred in the middle Miocene, leading to the formation of present-day tectonic configuration in eastern Tibet. The geometry, kinematics, and age of the Litang fault system are reappraisedThe splayed Litang fault system was initiated at 16-13 Ma and expanded at 7-5 MaActive tectonic regime in eastern Tibet has been established since 16-13 Ma
关键词	Tibetan Plateau intracontinent deformation strike slip fault thermochronology kinematic reorganization
英文关键词	RED-RIVER FAULT; ALTYN TAGH FAULT; XIANSHUIHE FAULT; SHEAR ZONE; TECTONIC EVOLUTION; SLIP-RATE; RELIEF GENERATION; WESTERN YUNNAN; PLATEAU MARGIN; HIGH-ELEVATION
WOS研究方向	Geochemistry & Geophysics
WOS记录号	WOS:001125893300001
来源期刊	TECTONICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/282991
作者单位	China University of Geosciences - Wuhan; China University of Geosciences - Wuhan; Sinopec
推荐引用方式 GB/T 7714	Cao, Kai,Zhang, Di,Shen, Xiaoming,et al. Middle Miocene Onset of the Litang Fault System Records Kinematic Change in Eastern Tibet[J],2023,42(12).
APA	Cao, Kai.,Zhang, Di.,Shen, Xiaoming.,Zhang, Junfeng.,Wang, Dun.,...&Wang, Guocan.(2023).Middle Miocene Onset of the Litang Fault System Records Kinematic Change in Eastern Tibet.TECTONICS,42(12).
MLA	Cao, Kai,et al."Middle Miocene Onset of the Litang Fault System Records Kinematic Change in Eastern Tibet".TECTONICS 42.12(2023).