In the study of isotopic geochronology of grauitoids in the southern part of Xizang plateau, 103 mica and zircon ages were determined by K-At method and U-Pb method. Based upon the above mica and zircon ages of variou...In the study of isotopic geochronology of grauitoids in the southern part of Xizang plateau, 103 mica and zircon ages were determined by K-At method and U-Pb method. Based upon the above mica and zircon ages of various types of granitoid, together with their geological setting, three intrusive stages have been distinquished for granitoids in Southern Xizang : the first stage, 120--70 m. y. (late Yenshanian) ; the second stage,50---30 m.y. (early Himalayan) ; the third stage, 20--10 m.y. (late Himalayan). It is evident from the characteristic zonal distribution patterns of granitoids and the spacial-temporal consistency in their isotopic geochronology that there exists a close inter-connection between the subduetion stage and the collision stage.展开更多
Fourty-four isotopic ages have been determined by K-Ar and U-Th-Pb methods for late Palaeozoic granites in Nan Ling Region,South China.All dating values variate within the ranges of 231-348 m.y.From the obtained dates...Fourty-four isotopic ages have been determined by K-Ar and U-Th-Pb methods for late Palaeozoic granites in Nan Ling Region,South China.All dating values variate within the ranges of 231-348 m.y.From the obtained dates,further evidence has been found that there do exist late Palaeozoic granites, which can be subdivided into late Devonian and Permian granites. Within the late Devonian terrain, there is a granitic intrusive, namely granodiorite with zircon U-Th-Pb age of 348 m.y.,while ten granitic intrusives have been recognized within the Permian terrain where granites are predominant, yielding biotite K-Ar age of 236-289 m.y. (λβ= 4.72 ×10^-10y.^-1,λR=5.57×10^-11y.^-2) and zireon U-Th-Pb age ranging from 231--280 m.y.respeetively. It is obvious from the dates that intrusive activities if granitic magma extensively took place in Nan Ling re,on during the late Palaeozoic, although no records of orogenic movements have been found, indicating that the faulta are the main factor controlling the activities of granitic magma, whereas the orogenic movements are not the only prerequisite to the formation of granitic magma, and the intrusive activities.展开更多
文摘In the study of isotopic geochronology of grauitoids in the southern part of Xizang plateau, 103 mica and zircon ages were determined by K-At method and U-Pb method. Based upon the above mica and zircon ages of various types of granitoid, together with their geological setting, three intrusive stages have been distinquished for granitoids in Southern Xizang : the first stage, 120--70 m. y. (late Yenshanian) ; the second stage,50---30 m.y. (early Himalayan) ; the third stage, 20--10 m.y. (late Himalayan). It is evident from the characteristic zonal distribution patterns of granitoids and the spacial-temporal consistency in their isotopic geochronology that there exists a close inter-connection between the subduetion stage and the collision stage.
文摘Fourty-four isotopic ages have been determined by K-Ar and U-Th-Pb methods for late Palaeozoic granites in Nan Ling Region,South China.All dating values variate within the ranges of 231-348 m.y.From the obtained dates,further evidence has been found that there do exist late Palaeozoic granites, which can be subdivided into late Devonian and Permian granites. Within the late Devonian terrain, there is a granitic intrusive, namely granodiorite with zircon U-Th-Pb age of 348 m.y.,while ten granitic intrusives have been recognized within the Permian terrain where granites are predominant, yielding biotite K-Ar age of 236-289 m.y. (λβ= 4.72 ×10^-10y.^-1,λR=5.57×10^-11y.^-2) and zireon U-Th-Pb age ranging from 231--280 m.y.respeetively. It is obvious from the dates that intrusive activities if granitic magma extensively took place in Nan Ling re,on during the late Palaeozoic, although no records of orogenic movements have been found, indicating that the faulta are the main factor controlling the activities of granitic magma, whereas the orogenic movements are not the only prerequisite to the formation of granitic magma, and the intrusive activities.
