tailieunhanh - Báo cáo " Late Eocene metamorphism and ductile deformation age of Con Voi range, the Red River shear zone: evidence from the garnet Sm/Nd dating"

Con Voi range in Vietnam was a southeastward continuity of the Red River Ailaoshan tertiary shear zone, a boundary between Indochina and south China blocks during the southeastward extrusion of Indochina block. It composed of high grade metamorphic and strongly deformed rocks with various protoliths. The foliation and schistosity folded to produce a large antiform structure during the late phase of ductile deformation and exhumation. Together with the Ailaoshan, Diancangshan, Con Voi range suffered from an intensively sheared and metamorphosed during the collision of Indian with Eurasian plates. The published radiochronological data indicated that the cooling age took place. | VNU Journal of Science Earth Sciences 23 2007 69-75 Late Eocene metamorphism and ductile deformation age of Con Voi range the Red River shear zone evidence from the garnet Sm Nd dating Nguyen Van Vuong College of Science VNU Received 26 January 2007 Abstract. Con Voi range in Vietnam was a southeastward continuity of the Red River Ailaoshan tertiary shear zone a boundary between Indochina and south China blocks during the southeastward extrusion of Indochina block. It composed of high grade metamorphic and strongly deformed rocks with various protoliths. The foliation and schistosity folded to produce a large antiform structure during the late phase of ductile deformation and exhumation. Together with the Ailaoshan Diancangshan Con Voi range suffered from an intensively sheared and metamorphosed during the collision of Indian with Eurasian plates. The published radiochronological data indicated that the cooling age took place from 28 to 17 . millions years . Those data did not reflect the timing of peak metamorphic event and associated ductile deformation. New Sm Nd isochron age on single garnet extracted from biotite-garnet-silimanite bearing gneiss rock within Con Voi range evidenced that the timing of metamorphic culmination and ductile deformation occurred as early as 36 . ago. This implied that the earliest stage of deformation along the Red River-Ailaoshan shear zone could be at least absorbed partially by the opening of Bac Bo basin. Keywords Red River shear Sm Nd age Late Eocene Metamorphism Deformation. 1. Introduction Con Voi range bounded northeastward by Song Chay fault and southwestward by Song Hong fault was a continuity of the Ailao Shan Red River shear zone which extended approximately 1000km from syntaxis to the Eastern Sea of Vietnam . This shear zone was considered as a boundary between the Indochina block and south China one in Tertiary. It was a narrow zone of amphibolitic-facies gneiss and Tel. 84-4-8585097. E-mail vuongnv@