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J P Zheng - One of the best experts on this subject based on the ideXlab platform.
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origin of volcanic ash beds across the permian triassic boundary daxiakou south china petrology and u pb age trace elements and hf isotope composition of zircon
Chemical Geology, 2013Co-Authors: Qiuling Gao, Ning Zhang, Wenchen Xia, Qinglai Feng, Zhongqiang Chen, J P ZhengAbstract:Abstract Abundant volcanic ash layers, largely altered to clay, characterize the Permian–Triassic boundary beds of the Daxiakou section, South China. Volcanism may have had an important role in the Permian–Triassic mass extinction, so it is important to understand the origin of these ash beds. The lithology of ash bed 260, as constrained by modes of crystal fragments (66.7% plagioclase, 7.2% alkali feldspar, and 26.1% quartz), suggests that the ash represents dacitic Volcanism. The U–Pb ages, trace elements and Hf-isotope compositions of zircons from ten ash beds have been analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons can be divided into two groups: magmatic zircons (~ 97%, 227–279 Ma) and inherited zircons (~ 3%, 678–2424 Ma). Magmatic zircons have Y, Hf, Th and U contents and Nb/Ta ratios typical of zircons from silicic calc-alkaline Volcanism. e Hf (t) values of magmatic zircons vary from − 10.9 to + 5.3, implying magmatic mixing between juvenile crustal material (probably Neoproterozoic in age) and ancient crustal material (probably Archean). Beds 252–259-b have relatively depleted Hf-isotope compositions with e Hf (t) values of − 10.9–+ 5.3 and averages of − 5.0–− 2.5, while other beds have e Hf (t) values of − 10.8–+ 4.4 (mostly − 10.8–− 3.5) and averages of − 8.9–− 6.8, implying more input of juvenile crustal material in the Volcanism of Beds 252–259-b. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggests that the Volcanism producing the ashes took place along the convergent continent margins during the formation of the Pangea supercontinent. This intense silicic Volcanism may have played an important role in causing the Permian–Triassic mass extinction in South China.
Qiuling Gao - One of the best experts on this subject based on the ideXlab platform.
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origin of volcanic ash beds across the permian triassic boundary daxiakou south china petrology and u pb age trace elements and hf isotope composition of zircon
Chemical Geology, 2013Co-Authors: Qiuling Gao, Ning Zhang, Wenchen Xia, Qinglai Feng, Zhongqiang Chen, J P ZhengAbstract:Abstract Abundant volcanic ash layers, largely altered to clay, characterize the Permian–Triassic boundary beds of the Daxiakou section, South China. Volcanism may have had an important role in the Permian–Triassic mass extinction, so it is important to understand the origin of these ash beds. The lithology of ash bed 260, as constrained by modes of crystal fragments (66.7% plagioclase, 7.2% alkali feldspar, and 26.1% quartz), suggests that the ash represents dacitic Volcanism. The U–Pb ages, trace elements and Hf-isotope compositions of zircons from ten ash beds have been analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons can be divided into two groups: magmatic zircons (~ 97%, 227–279 Ma) and inherited zircons (~ 3%, 678–2424 Ma). Magmatic zircons have Y, Hf, Th and U contents and Nb/Ta ratios typical of zircons from silicic calc-alkaline Volcanism. e Hf (t) values of magmatic zircons vary from − 10.9 to + 5.3, implying magmatic mixing between juvenile crustal material (probably Neoproterozoic in age) and ancient crustal material (probably Archean). Beds 252–259-b have relatively depleted Hf-isotope compositions with e Hf (t) values of − 10.9–+ 5.3 and averages of − 5.0–− 2.5, while other beds have e Hf (t) values of − 10.8–+ 4.4 (mostly − 10.8–− 3.5) and averages of − 8.9–− 6.8, implying more input of juvenile crustal material in the Volcanism of Beds 252–259-b. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggests that the Volcanism producing the ashes took place along the convergent continent margins during the formation of the Pangea supercontinent. This intense silicic Volcanism may have played an important role in causing the Permian–Triassic mass extinction in South China.
Trond H Torsvik - One of the best experts on this subject based on the ideXlab platform.
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submarine palaeoenvironments during emeishan flood basalt Volcanism sw china implications for plume lithosphere interaction during the capitanian middle permian end guadalupian extinction event
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Paul B. Wignall, Mike Widdowson, Dougal A Jerram, Xulong Lai, Yadong Sun, David P G Bond, Trond H TorsvikAbstract:Plume-induced lithospheric uplift and erosion are widely regarded as key features of large igneous province (LIP) emplacement, as is the coincidence of LIP eruption with major extinction and oceanic anoxic events (OAE). The Emeishan LIP, which erupted during the Capitanian (formally ‘end Guadalupian’) extinction event, has provided the most celebrated example where advocates argue that in excess of 500 m of axisymmetric uplift occurred over >30 000 km2 causing extensive radially-distributed erosion and alluvial fan formation. However, the recognition of submarine and phreatomagmatic-style Volcanism, as well as syn-volcanic marine sediments interbedded in the eruptive succession, now requires further examination to this simple plume – uplift model. Here we present data from newly-discovered sections from the center of the putative uplifted area (around Lake Er Hai, SW Yunnan Province,) that provide a more complete history of the Emeishan Volcanism. These reveal that platform carbonate deposition was terminated by rapid subsidence, followed quickly by the onset of Volcanism. For at least the lower two thirds of the 4-5 km thick lava pile, eruptions continued at or below sea level, as testified by the presence of voluminous mafic volcaniclastic deposits, pillow lavas and development of syn-volcanic reefal limestones in the Emeishan inner zone. Only in the later stages of eruption did terrestrial lava flows become widely developed. This onset of Volcanism in a submarine setting and the consequent violent, phreatomagmatic-style eruptions may have exacerbated the cooling effects of Volcanism during the Capitanian. The late Permian of SW China at the time of the Emeishan was an extended area of thinned lithosphere with epeiric seas, which appear to have been sustained through the onset of LIP emplacement. Therefore, whilst there remains substantial geochemical support of a plume origin for Emeishan Volcanism, LIP emplacement cannot be ubiquitously associated with regional pre-eruption uplift particularly where complex lithospheric structure exists above a plume.
Zhongqiang Chen - One of the best experts on this subject based on the ideXlab platform.
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origin of volcanic ash beds across the permian triassic boundary daxiakou south china petrology and u pb age trace elements and hf isotope composition of zircon
Chemical Geology, 2013Co-Authors: Qiuling Gao, Ning Zhang, Wenchen Xia, Qinglai Feng, Zhongqiang Chen, J P ZhengAbstract:Abstract Abundant volcanic ash layers, largely altered to clay, characterize the Permian–Triassic boundary beds of the Daxiakou section, South China. Volcanism may have had an important role in the Permian–Triassic mass extinction, so it is important to understand the origin of these ash beds. The lithology of ash bed 260, as constrained by modes of crystal fragments (66.7% plagioclase, 7.2% alkali feldspar, and 26.1% quartz), suggests that the ash represents dacitic Volcanism. The U–Pb ages, trace elements and Hf-isotope compositions of zircons from ten ash beds have been analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons can be divided into two groups: magmatic zircons (~ 97%, 227–279 Ma) and inherited zircons (~ 3%, 678–2424 Ma). Magmatic zircons have Y, Hf, Th and U contents and Nb/Ta ratios typical of zircons from silicic calc-alkaline Volcanism. e Hf (t) values of magmatic zircons vary from − 10.9 to + 5.3, implying magmatic mixing between juvenile crustal material (probably Neoproterozoic in age) and ancient crustal material (probably Archean). Beds 252–259-b have relatively depleted Hf-isotope compositions with e Hf (t) values of − 10.9–+ 5.3 and averages of − 5.0–− 2.5, while other beds have e Hf (t) values of − 10.8–+ 4.4 (mostly − 10.8–− 3.5) and averages of − 8.9–− 6.8, implying more input of juvenile crustal material in the Volcanism of Beds 252–259-b. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggests that the Volcanism producing the ashes took place along the convergent continent margins during the formation of the Pangea supercontinent. This intense silicic Volcanism may have played an important role in causing the Permian–Triassic mass extinction in South China.
Qinglai Feng - One of the best experts on this subject based on the ideXlab platform.
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origin of volcanic ash beds across the permian triassic boundary daxiakou south china petrology and u pb age trace elements and hf isotope composition of zircon
Chemical Geology, 2013Co-Authors: Qiuling Gao, Ning Zhang, Wenchen Xia, Qinglai Feng, Zhongqiang Chen, J P ZhengAbstract:Abstract Abundant volcanic ash layers, largely altered to clay, characterize the Permian–Triassic boundary beds of the Daxiakou section, South China. Volcanism may have had an important role in the Permian–Triassic mass extinction, so it is important to understand the origin of these ash beds. The lithology of ash bed 260, as constrained by modes of crystal fragments (66.7% plagioclase, 7.2% alkali feldspar, and 26.1% quartz), suggests that the ash represents dacitic Volcanism. The U–Pb ages, trace elements and Hf-isotope compositions of zircons from ten ash beds have been analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons can be divided into two groups: magmatic zircons (~ 97%, 227–279 Ma) and inherited zircons (~ 3%, 678–2424 Ma). Magmatic zircons have Y, Hf, Th and U contents and Nb/Ta ratios typical of zircons from silicic calc-alkaline Volcanism. e Hf (t) values of magmatic zircons vary from − 10.9 to + 5.3, implying magmatic mixing between juvenile crustal material (probably Neoproterozoic in age) and ancient crustal material (probably Archean). Beds 252–259-b have relatively depleted Hf-isotope compositions with e Hf (t) values of − 10.9–+ 5.3 and averages of − 5.0–− 2.5, while other beds have e Hf (t) values of − 10.8–+ 4.4 (mostly − 10.8–− 3.5) and averages of − 8.9–− 6.8, implying more input of juvenile crustal material in the Volcanism of Beds 252–259-b. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggests that the Volcanism producing the ashes took place along the convergent continent margins during the formation of the Pangea supercontinent. This intense silicic Volcanism may have played an important role in causing the Permian–Triassic mass extinction in South China.
