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
It is stratigraphically evident that the Bendong granodiorite massif intruded into the late Protorozoic Szupu Group and is unconformably overlain by the Banxi Group.The isotopic age of the massif has been measured by ...It is stratigraphically evident that the Bendong granodiorite massif intruded into the late Protorozoic Szupu Group and is unconformably overlain by the Banxi Group.The isotopic age of the massif has been measured by U-Th-Pb, Rb-Sr, and K-Ar mcthods. The age from the Wetherill concordia curve of accessory minerals (1100m.y.), U-Th-Pb monozite age (1100m.y.), in which the four groups of internal ages are close to each other, and Rb-Sr total-rock isochron age (1063±95m.y.) are in good agreement within the measured error. The initial Sr^87/Sr^86 ratio is 0.7001±0.0039 and two Rb-Sr internal isochran ages are 406 and 410 m.y. respectively. It is concluded from the results that (1) Bendong massif was formed 1063±95m.y. ago. The magma from which the massif was derived must have come from the mantle; (2) A strongest metamorphism oceurred about 410 m.y. ago after the formation of the massif and (3) The Banxi Group of South China is stratigraphically equivalent to the Qingbaikou Group in the Yenshan Rcgion of North China. The Szupu orogenic movement leading to the unconformity between the Szupu and Banxi Groups is corresponding to the Jingyu orogenic movement in the Yenshan Region.展开更多
109 isotopic ages have been determined and collected in the recentten years, Most of them belong to Yenshanian, within which an early period (140--180m.y.) and a mid.late period (120-130m.y.) are distinguished. Granod...109 isotopic ages have been determined and collected in the recentten years, Most of them belong to Yenshanian, within which an early period (140--180m.y.) and a mid.late period (120-130m.y.) are distinguished. Granodiorite is predominant in early Yenshanian, and the related ore deposits are mainly of skarn character with mesothermal vein fillings being secondary in importance. During the mid-late Yenshanian, granite prevails and are accompanied by iron mineralization. From early to mid-late Yenshanian, the magmatie activity exhibites a striking regularity of variation in composition from intermediateacid servations, indicate that pegmatites in the Tanba region are related to Caledonian migmatization and have been reworked by two separated events at 120--130 m.y. (northern zone) and 70--80m.y. (southern zone) respectively. The migmatization progress has resulted in the formation of muscovite and biotite, thus offering an important eluc to the genesis of industrial muscovite. Three episodes of magmatic emplacement (590--720 m.y., 800-900 m.y., and more than 960 m.y.) in late Proterozoic times are also reeognized in this region.展开更多
The concentrations of radiogenic Ar^40 and cosmogenic Ar^32 in Anlung chondrite have been measured by the isotopic dilution technique. A ultrahigh-vacuum system have been designed for extracting and purifying the gase...The concentrations of radiogenic Ar^40 and cosmogenic Ar^32 in Anlung chondrite have been measured by the isotopic dilution technique. A ultrahigh-vacuum system have been designed for extracting and purifying the gases in the sample. These data provide a K^40-Ar^40 age of 3.28 b.y. and an exposure age of 3.0 m,y. for this chondrite.Based on these results, we have discussed the origin and the former environment of stone meteorite.展开更多
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.
文摘It is stratigraphically evident that the Bendong granodiorite massif intruded into the late Protorozoic Szupu Group and is unconformably overlain by the Banxi Group.The isotopic age of the massif has been measured by U-Th-Pb, Rb-Sr, and K-Ar mcthods. The age from the Wetherill concordia curve of accessory minerals (1100m.y.), U-Th-Pb monozite age (1100m.y.), in which the four groups of internal ages are close to each other, and Rb-Sr total-rock isochron age (1063±95m.y.) are in good agreement within the measured error. The initial Sr^87/Sr^86 ratio is 0.7001±0.0039 and two Rb-Sr internal isochran ages are 406 and 410 m.y. respectively. It is concluded from the results that (1) Bendong massif was formed 1063±95m.y. ago. The magma from which the massif was derived must have come from the mantle; (2) A strongest metamorphism oceurred about 410 m.y. ago after the formation of the massif and (3) The Banxi Group of South China is stratigraphically equivalent to the Qingbaikou Group in the Yenshan Rcgion of North China. The Szupu orogenic movement leading to the unconformity between the Szupu and Banxi Groups is corresponding to the Jingyu orogenic movement in the Yenshan Region.
文摘109 isotopic ages have been determined and collected in the recentten years, Most of them belong to Yenshanian, within which an early period (140--180m.y.) and a mid.late period (120-130m.y.) are distinguished. Granodiorite is predominant in early Yenshanian, and the related ore deposits are mainly of skarn character with mesothermal vein fillings being secondary in importance. During the mid-late Yenshanian, granite prevails and are accompanied by iron mineralization. From early to mid-late Yenshanian, the magmatie activity exhibites a striking regularity of variation in composition from intermediateacid servations, indicate that pegmatites in the Tanba region are related to Caledonian migmatization and have been reworked by two separated events at 120--130 m.y. (northern zone) and 70--80m.y. (southern zone) respectively. The migmatization progress has resulted in the formation of muscovite and biotite, thus offering an important eluc to the genesis of industrial muscovite. Three episodes of magmatic emplacement (590--720 m.y., 800-900 m.y., and more than 960 m.y.) in late Proterozoic times are also reeognized in this region.
文摘The concentrations of radiogenic Ar^40 and cosmogenic Ar^32 in Anlung chondrite have been measured by the isotopic dilution technique. A ultrahigh-vacuum system have been designed for extracting and purifying the gases in the sample. These data provide a K^40-Ar^40 age of 3.28 b.y. and an exposure age of 3.0 m,y. for this chondrite.Based on these results, we have discussed the origin and the former environment of stone meteorite.
