Analysis using the Sensitive High Resolution Ion Microprobe (SHRIMP) shows that the Yongsheng pluton, located to the south of Huadian County, Jilin Province, in the North China Craton, has a zircon U-Pb isotopic empla...Analysis using the Sensitive High Resolution Ion Microprobe (SHRIMP) shows that the Yongsheng pluton, located to the south of Huadian County, Jilin Province, in the North China Craton, has a zircon U-Pb isotopic emplacement age of (31.6±1.3) Ma. It is therefore the youngest exposed pluton so far recognized in eastern China. Although geochemical data indicate intensive crystal fractionation, the Sr-Nd isotopic features suggest that the magmatic source region of the lithospheric mantle was weakly depleted. This implies that the previous enriched lithospheric mantle had been replaced by juvenile asthenospheric mantle before or during the Palaeogene. This recognition has great significance for future work on the Mesozoic-Cenozoic geological evolution and deep geological processes in eastern China.展开更多
Light gray to yellowish brown youngest Toba tuff(YTT)ash,preserved in the Quaternary sediments of India,have been used as a tool to know depositional and bracketing time period of the same in the sediments through app...Light gray to yellowish brown youngest Toba tuff(YTT)ash,preserved in the Quaternary sediments of India,have been used as a tool to know depositional and bracketing time period of the same in the sediments through applications of luminescence dating to interpret age connotation of various geological events.Pre-and post-tephra sediments of YTT ash beds from Hudki and Sukali areas of Purna alluvial basin,Central India have been optically dated to interpret the depositional age and bracketing time of the tephra within sedimentary sequences.These sediments are yellowish brown,thinly bedded,laminated,silty clay and host laterally extend discontinued beds of 0.15–0.20 m thickness.The ash is light gray,fine grained and powdery in nature,massive to structureless and lacks any sign of retransportation and redeposition,hence,considered as primary in nature.Total four sediment samples,one each from pre-and post-tephra lithounits of both the localities have been dated through optically stimulated luminescence technique(OSL)equipped with single aliquot regenerative(SAR)procedure on the feldspar grains.It shows pre-and post-tephra ages of 57±5 and 70±4 ka respectively for Hudki and 66±5 and 67±4 ka for Sukali localities.These depositional ages suggest that the ash was bracketed within sediments thousands years after YTT eruption.It is correlatable with the previously reported depositional and absolute ages for the YTT ash from the localities of Ghoghara and Khuntheli,Son Valley;Tejpur,Madhumati River Basin and Jwalapuram,Jurreru Valley.These ages also provide an idea about the period of existence of biological communities represented by the remains of faunal and vegetational activities before and during settlement of the YTT ash in the basin area.展开更多
Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as pla...Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with the δ18O-based age, it is suggested that ash Layer A is correlated to the youngest Toba tuff(YTT), Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic eruption event.展开更多
Wenwen,China’s youngest backpacker,is turning six and has hiked through the Himalayas and may be going on a desert journey this year.Wenwen has been on adventures across China with her parents,Pan Tufeng and Yuan Dua...Wenwen,China’s youngest backpacker,is turning six and has hiked through the Himalayas and may be going on a desert journey this year.Wenwen has been on adventures across China with her parents,Pan Tufeng and Yuan Duan,soon after she展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 49872031) and Jilin Excellent Youth Fund.
文摘Analysis using the Sensitive High Resolution Ion Microprobe (SHRIMP) shows that the Yongsheng pluton, located to the south of Huadian County, Jilin Province, in the North China Craton, has a zircon U-Pb isotopic emplacement age of (31.6±1.3) Ma. It is therefore the youngest exposed pluton so far recognized in eastern China. Although geochemical data indicate intensive crystal fractionation, the Sr-Nd isotopic features suggest that the magmatic source region of the lithospheric mantle was weakly depleted. This implies that the previous enriched lithospheric mantle had been replaced by juvenile asthenospheric mantle before or during the Palaeogene. This recognition has great significance for future work on the Mesozoic-Cenozoic geological evolution and deep geological processes in eastern China.
基金financially supported by Science and Engineering Research Board(SERB),New Delhi,India in the form of major research project(No.SB/S4/ES-692/2013)awarded to AKS。
文摘Light gray to yellowish brown youngest Toba tuff(YTT)ash,preserved in the Quaternary sediments of India,have been used as a tool to know depositional and bracketing time period of the same in the sediments through applications of luminescence dating to interpret age connotation of various geological events.Pre-and post-tephra sediments of YTT ash beds from Hudki and Sukali areas of Purna alluvial basin,Central India have been optically dated to interpret the depositional age and bracketing time of the tephra within sedimentary sequences.These sediments are yellowish brown,thinly bedded,laminated,silty clay and host laterally extend discontinued beds of 0.15–0.20 m thickness.The ash is light gray,fine grained and powdery in nature,massive to structureless and lacks any sign of retransportation and redeposition,hence,considered as primary in nature.Total four sediment samples,one each from pre-and post-tephra lithounits of both the localities have been dated through optically stimulated luminescence technique(OSL)equipped with single aliquot regenerative(SAR)procedure on the feldspar grains.It shows pre-and post-tephra ages of 57±5 and 70±4 ka respectively for Hudki and 66±5 and 67±4 ka for Sukali localities.These depositional ages suggest that the ash was bracketed within sediments thousands years after YTT eruption.It is correlatable with the previously reported depositional and absolute ages for the YTT ash from the localities of Ghoghara and Khuntheli,Son Valley;Tejpur,Madhumati River Basin and Jwalapuram,Jurreru Valley.These ages also provide an idea about the period of existence of biological communities represented by the remains of faunal and vegetational activities before and during settlement of the YTT ash in the basin area.
基金The National Natural Science Foundation of China under contract Nos 41106052 91228101 and 41306056the Fundamental Research Funds for National Nonprofit Institute Grant under contract No.JG0910
文摘Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with the δ18O-based age, it is suggested that ash Layer A is correlated to the youngest Toba tuff(YTT), Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic eruption event.
文摘Wenwen,China’s youngest backpacker,is turning six and has hiked through the Himalayas and may be going on a desert journey this year.Wenwen has been on adventures across China with her parents,Pan Tufeng and Yuan Duan,soon after she
