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Wu Genyao - One of the best experts on this subject based on the ideXlab platform.
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intraplate extension prior to continental extrusion along the ailao shan red river Shear Zone
Geology, 1997Co-Authors: Sunlin Chung, Tung Yi Lee, Peiling Wang, Chinyu Chen, Nguyen Trong Yem, Tran Trong Hoa, Wu GenyaoAbstract:Left-lateral movement of the Ailao Shan–Red River Shear Zone lends support to the hypothesis of continental extrusion resulting from the collision of India with Asia. Our new observations from northwestern Yunnan, China, and northwestern Vietnam on different sides of the Shear Zone demonstrate that the sinistral offset was ∼600 km according to correlations of Permian-Triassic flood basalt successions and late Paleogene highly potassic mafic magmas. We conclude that the Shear was propagating on the South China continental margin and does not correspond to a suture between South China and Indochina. Furthermore, the highly potassic magmas were emplaced from ca. 40 to 30 Ma, before the Shear movement, which was caused by the late Oligocene to early Miocene (ca. 27–22 Ma) extrusion activity. This suggests that a late Eocene to early Oligocene intraplate extension, possibly induced by delamination of thickened continental lithosphere, took place in northwestern Yunnan (or eastern Tibet) as a response to the India-Asia collision. This extension, and sea-floor spreading of the South China Sea that began ca. 30 Ma, could have accounted for the initiation of the Ailao Shan–Red River Shear Zone.
M P Searle - One of the best experts on this subject based on the ideXlab platform.
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role of the red river Shear Zone yunnan and vietnam in the continental extrusion of se asia
Journal of the Geological Society, 2006Co-Authors: M P SearleAbstract:The 1000 km long NW–SE-striking, left-lateral Ailao Shan–Red River Shear Zone runs from the southeastern corner of Tibet to the Gulf of Tonkin and the South China Sea. It has been used as the prime example of a lithospheric-scale strike-slip fault that has accommodated between 500 and 1000 km of southeastwards extrusion of Indo-China away from the Indian plate indentor. Central to the model of continental extrusion is that such faults cut through the entire lithosphere, that Shear heating resulted in high-grade metamorphism and local anatexis, and that the ages of Sheared granites along the fault also date the timing of strike-slip Shearing. However, structural data from the Red River Shear Zone clearly show that vertical strike-slip faulting post-dated metamorphism and granite emplacement. Most granites along the Shear Zone are mantle-related granodiorites or within-plate alkali granites formed prior to Shearing along the Red River Shear Zone. Left-lateral kinematic indicators are ubiquitous within the Red River mylonites, but they are always lower-temperature fabrics, formed after peak sillimanite metamorphism and after granite crystallization. It is suggested that left-lateral strike-slip Shearing along the Red River Shear Zone started after 21 Ma, not at 35 Ma as previously thought, and the fault was purely a crustal structure. None of the geological features used to propose the 500–1000 km offsets are robust, and the total finite offset remains unknown.
Sunlin Chung - One of the best experts on this subject based on the ideXlab platform.
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intraplate extension prior to continental extrusion along the ailao shan red river Shear Zone
Geology, 1997Co-Authors: Sunlin Chung, Tung Yi Lee, Peiling Wang, Chinyu Chen, Nguyen Trong Yem, Tran Trong Hoa, Wu GenyaoAbstract:Left-lateral movement of the Ailao Shan–Red River Shear Zone lends support to the hypothesis of continental extrusion resulting from the collision of India with Asia. Our new observations from northwestern Yunnan, China, and northwestern Vietnam on different sides of the Shear Zone demonstrate that the sinistral offset was ∼600 km according to correlations of Permian-Triassic flood basalt successions and late Paleogene highly potassic mafic magmas. We conclude that the Shear was propagating on the South China continental margin and does not correspond to a suture between South China and Indochina. Furthermore, the highly potassic magmas were emplaced from ca. 40 to 30 Ma, before the Shear movement, which was caused by the late Oligocene to early Miocene (ca. 27–22 Ma) extrusion activity. This suggests that a late Eocene to early Oligocene intraplate extension, possibly induced by delamination of thickened continental lithosphere, took place in northwestern Yunnan (or eastern Tibet) as a response to the India-Asia collision. This extension, and sea-floor spreading of the South China Sea that began ca. 30 Ma, could have accounted for the initiation of the Ailao Shan–Red River Shear Zone.
Dalai Zhong - One of the best experts on this subject based on the ideXlab platform.
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structure kinematics and ages of transpression during strain partitioning in the chongshan Shear Zone western yunnan china
Journal of Structural Geology, 2010Co-Authors: Bo Zhang, Jinjiang Zhang, Dalai ZhongAbstract:Abstract The Chongshan Shear Zone extends from the eastern Himalayan Syntaxis to the Lincang Granitic pluton in Yunnan Province, China. The structure and kinematics show that the Shear Zone comprises mainly of mylonitic gneiss–migmatite and schist with a dextral-dominated strike-slip motion in an N–S trending northern segment, and a sinistral strike-slip Shear in NW–SE trending middle and southern segments. Both were developed under a bulk, regional-scale sinistral transpression. SHRIMP and LA-ICPMS U–Pb and 40 Ar/ 39 Ar dating reveal two Tertiary magmatic events along the Zone, followed by younger sinistral strike-slip Shear. The Eocene magmatic event (c. 55–38 Ma), followed by metamorphism at c. 36 Ma, happened before the strike-slip motion. The strike-slip Shear along the Zone began c. 32 Ma, which generated Shear heating from 32 to 22 Ma. The 40 Ar/ 39 Ar ages of syn-kinematic micas, range from 19 to 14 Ma, and indicate that the strike-slip Shear continued to this time with coeval transpressional exhumation and uplift of the metamorphic rocks along the Biluoxueshan–Chongshan chain. The Chongshan Zone is thus a Cenozoic Shear Zone, which was contemporaneous with motion on the left-lateral Ailao Shan-Red River Shear Zone and the right-lateral Gaoligong Shear Zone, and should be important in accommodating the northwards movement of India during collision. During Oligocene to Miocene times, the continental block that was extruded between the Ailao Shan-Red River and Gaoligong Shear Zones was dismembered into at least two major fragments by the Chongshan Shear Zone.
Bo Zhang - One of the best experts on this subject based on the ideXlab platform.
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Cenozoic Exhumation of the Ailaoshan‐Red River Shear Zone: New Insights From Low‐Temperature Thermochronology
'American Geophysical Union (AGU)', 2020Co-Authors: Wang Yang, Bo Zhang, Wang Yuejun, Schoenbohm, Lindsay M., Zhang Peizhen, Sobel, Edward R., Zhou Renjie, Shi Xuhua, Zhang Jinjiang, Stockli, Daniel F.Abstract:Continental-scale Shear Zones play an important role in accommodating block extrusion and rotation as shown by deformation on the Ailaoshan-Red River Shear Zone (ASRRSZ) in the SE Tibetan Plateau. This study presents 13 apatite (U-Th)/He, 11 zircon (U-Th)/He, and three apatite fission track dates, together with thermal modeling in the Ailaoshan and Xuelongshan segments (ALSZ and XLSZ) of the Shear Zone to investigate its Cenozoic exhumation history and mechanism, which are critical for understanding its tectonic and landscape evolution. Our results, combined with published chronologic data, reveal that Shear Zone rocks along the ALSZ experienced prominent and rapid cooling from high temperature (>500°C) to 120–60°C at a rate of 75–100°C/Myr during 29–17\ua0Ma with northwestward younging onset. A second, lower magnitude accelerated cooling occurred at 14–10\ua0Ma along the ALSZ at a rate of 20–30°C/Myr, with a later initiation on the XLSZ at ~5\ua0Ma and continuing to present with a cooling rate of ~20°C/Myr. Thermal modeling reveals a single rapid cooling phase with a rate of 17–14°C/Myr in the Eocene to early Oligocene for samples outside the Shear Zones. These three fast cooling episodes are directly related to deformation stages including crustal shortening across the SE plateau, sinistral ductile Shearing along the ASRRSZ, and dextral faulting with a dip-slip component on the Red River and Weixi-Qiaohou faults along the Shear Zone flanks. Furthermore, the northward migration of kinematic reversal and associated cooling along strike since the mid-late Miocene likely reflects the northward advance of the eastern Himalayan syntaxis
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structure kinematics and ages of transpression during strain partitioning in the chongshan Shear Zone western yunnan china
Journal of Structural Geology, 2010Co-Authors: Bo Zhang, Jinjiang Zhang, Dalai ZhongAbstract:Abstract The Chongshan Shear Zone extends from the eastern Himalayan Syntaxis to the Lincang Granitic pluton in Yunnan Province, China. The structure and kinematics show that the Shear Zone comprises mainly of mylonitic gneiss–migmatite and schist with a dextral-dominated strike-slip motion in an N–S trending northern segment, and a sinistral strike-slip Shear in NW–SE trending middle and southern segments. Both were developed under a bulk, regional-scale sinistral transpression. SHRIMP and LA-ICPMS U–Pb and 40 Ar/ 39 Ar dating reveal two Tertiary magmatic events along the Zone, followed by younger sinistral strike-slip Shear. The Eocene magmatic event (c. 55–38 Ma), followed by metamorphism at c. 36 Ma, happened before the strike-slip motion. The strike-slip Shear along the Zone began c. 32 Ma, which generated Shear heating from 32 to 22 Ma. The 40 Ar/ 39 Ar ages of syn-kinematic micas, range from 19 to 14 Ma, and indicate that the strike-slip Shear continued to this time with coeval transpressional exhumation and uplift of the metamorphic rocks along the Biluoxueshan–Chongshan chain. The Chongshan Zone is thus a Cenozoic Shear Zone, which was contemporaneous with motion on the left-lateral Ailao Shan-Red River Shear Zone and the right-lateral Gaoligong Shear Zone, and should be important in accommodating the northwards movement of India during collision. During Oligocene to Miocene times, the continental block that was extruded between the Ailao Shan-Red River and Gaoligong Shear Zones was dismembered into at least two major fragments by the Chongshan Shear Zone.
