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Jien Zhang - One of the best experts on this subject based on the ideXlab platform.
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a devonian to Carboniferous intra oceanic subduction system in western junggar nw china
Lithos, 2011Co-Authors: Jien Zhang, Wenjiao Xiao, Songjian AoAbstract:Abstract The Devonian and Carboniferous Rock assemblages in Western Junggar, southern Altaids, include ophiolitic melanges and coherent units. At Baijiantan, Yeyagou and Dagun Devonian gabbros and one group of volcanic Rocks (type I lava) generally crop out as blocks in a matrix of ultramafic Rocks and/or mudstone. They have a depleted light rare earth element (LREE) and mid-oceanic ridge basalt (MORB)-like signature with a small negative Nb anomaly, suggesting formation in a back-arc basin. Another group of volcanic Rocks (type II lava) from Baijiantan, Yeyagou, Western Karamay and Maliya includes alkaline basalt, basanite, andesite, dacite and trachyte that contain microphenocrysts of clinopyroxene–plagioclase, amygdales filled with chalcedony and calcite, and accessory pyrite and ilmenite. The type II lavas are further subdivided into five sub-types: (1) Type II 1 lava is strongly enriched in LREE with incompatible trace element ratios similar to oceanic island basalt (OIB), suggesting derivation from enriched mantle. (2) Type II 2 lava and tuff are slightly LREE-enriched, with a marked negative Nb anomaly and Th/Yb-enrichment indicating that they were generated in a supra-subduction zone (SSZ). (3) Type II 3 lava is also moderately enriched in LREE suggesting derivation from a more-enriched MORB mantle. (4) Type II 4 lava is enriched in LREE and has high Nb/Yb values close to those of OIB. It is extensively depleted in Nb suggesting a source containing a mixture of enriched and SSZ mantle. (5) Type II 5 lava has MORB-like REE patterns, and Nb/Yb and Th/Yb ratios. Based on field structural data, and the contemporaneity of the Baogutu adakite, a high-Mg diorite dike and the Miaoergou charnockite, these enriched and depleted magmatic features suggest generation in an intra-oceanic subduction zone influenced by ridge-trench interaction. The Altaids in Western Junggar are characterized by multiple intra-oceanic subduction systems, which may have continued to operate to the late Carboniferous.
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A Devonian to Carboniferous intra-oceanic subduction system in Western Junggar, NW China
Lithos, 2011Co-Authors: Jien Zhang, Wenjiao Xiao, Chunming Han, Qigui Mao, Qianqian GuoAbstract:Abstract The Devonian and Carboniferous Rock assemblages in Western Junggar, southern Altaids, include ophiolitic melanges and coherent units. At Baijiantan, Yeyagou and Dagun Devonian gabbros and one group of volcanic Rocks (type I lava) generally crop out as blocks in a matrix of ultramafic Rocks and/or mudstone. They have a depleted light rare earth element (LREE) and mid-oceanic ridge basalt (MORB)-like signature with a small negative Nb anomaly, suggesting formation in a back-arc basin. Another group of volcanic Rocks (type II lava) from Baijiantan, Yeyagou, Western Karamay and Maliya includes alkaline basalt, basanite, andesite, dacite and trachyte that contain microphenocrysts of clinopyroxene–plagioclase, amygdales filled with chalcedony and calcite, and accessory pyrite and ilmenite. The type II lavas are further subdivided into five sub-types: (1) Type II 1 lava is strongly enriched in LREE with incompatible trace element ratios similar to oceanic island basalt (OIB), suggesting derivation from enriched mantle. (2) Type II 2 lava and tuff are slightly LREE-enriched, with a marked negative Nb anomaly and Th/Yb-enrichment indicating that they were generated in a supra-subduction zone (SSZ). (3) Type II 3 lava is also moderately enriched in LREE suggesting derivation from a more-enriched MORB mantle. (4) Type II 4 lava is enriched in LREE and has high Nb/Yb values close to those of OIB. It is extensively depleted in Nb suggesting a source containing a mixture of enriched and SSZ mantle. (5) Type II 5 lava has MORB-like REE patterns, and Nb/Yb and Th/Yb ratios. Based on field structural data, and the contemporaneity of the Baogutu adakite, a high-Mg diorite dike and the Miaoergou charnockite, these enriched and depleted magmatic features suggest generation in an intra-oceanic subduction zone influenced by ridge-trench interaction. The Altaids in Western Junggar are characterized by multiple intra-oceanic subduction systems, which may have continued to operate to the late Carboniferous.
Gerard J.m. Versteegh - One of the best experts on this subject based on the ideXlab platform.
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Aliphatic and aromatic biomarkers from Carboniferous coal deposits at Dunbar (East Lothian, Scotland): Palaeobotanical and palaeoenvironmental significance
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Maria-fernanda Romero-sarmiento, Armelle Riboulleau, Marco Vecoli, Fatima Laggoun-défarge, Gerard J.m. VersteeghAbstract:Carboniferous (Visean) coals from Dunbar, East Lothian, Scotland, contain well-preserved miospore and megaspore assemblages suggesting a lycopod-dominated forest ecosystem with some ferns, sphenopsids and pteridosperms. The low rank of the coals and the well defined microflora permit assessment of the palaeoenvironmental significance of lipid biomarkers during the Early Carboniferous. Rock-Eval, petrographic, and lipid analyses indicate a fully terrestrial depositional environment. Although we also present and discuss a wide diversity of other lipid biomarkers (alkanes, hopanoids, steroids), we focus on the terrestrial-derived biomarkers. Combustion-derived PAHs pyrene, fluoranthene, benzo[a]anthracene, chrysene and triphenylene indicate the occurrence of forest fires in the study areas during Early Carboniferous times. Alkyldibenzofurans are considered to derive from lichen-biomass. Retene, cadalene, simonellite, tetrahydroretene and kaurane are poorly specific and can derive from a variety of early Palaeozoic land plants. Abietane, phyllocladane, ent-beyerane and 4β(H)-eudesmane, as well as bisnorsimonellite, diaromatic totarane, diaromatic sempervirane and 2-methylretene, however, as yet had only been reported from conifers, which do not appear in the fossil record until the Late Carboniferous. Within the lower Carboniferous forest ecosystem, arborescent lycopsids and pteridosperms are proposed as alternative sources for these compounds.
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Aliphatic and aromatic biomarkers from Carboniferous coal deposits at Dunbar (East Lothian, Scotland): Palaeobotanical and palaeoenvironmental significance
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Maria-fernanda Romero-sarmiento, Armelle Riboulleau, Marco Vecoli, Fatima Laggoun-défarge, Gerard J.m. VersteeghAbstract:International audienceCarboniferous (Viséan) coals from Dunbar, East Lothian, Scotland, contain well-preserved miospore and megaspore assemblages suggesting a lycopod-dominated forest ecosystem with some ferns, sphenopsids and pteridosperms. The low rank of the coals and the well defined microflora permit assessment of the palaeoenvironmental significance of lipid biomarkers during the Early Carboniferous. Rock-Eval, petrographic, and lipid analyses indicate a fully terrestrial depositional environment. Although we also present and discuss a wide diversity of other lipid biomarkers (alkanes, hopanoids, steroids), we focus on the terrestrial-derived biomarkers. Combustion-derived PAHs pyrene, fluoranthene, benzo[a]anthracene, chrysene and triphenylene indicate the occurrence of forest fires in the study areas during Early Carboniferous times. Alkyldibenzofurans are considered to derive from lichen-biomass. Retene, cadalene, simonellite, tetrahydroretene and kaurane are poorly specific and can derive from a variety of early Palaeozoic land plants. Abietane, phyllocladane, ent-beyerane and 4β(H)-eudesmane, as well as bisnorsimonellite, diaromatic totarane, diaromatic sempervirane and 2-methylretene, however, as yet had only been reported from conifers, which do not appear in the fossil record until the Late Carboniferous. Within the lower Carboniferous forest ecosystem, arborescent lycopsids and pteridosperms are proposed as alternative sources for these compounds
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Aliphatic and aromatic biomarkers from Carboniferous coal deposits at Dunbar (East Lothian, Scotland): Palaeobotanical and palaeoenvironmental significance
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Maria-fernanda Romero-sarmiento, Armelle Riboulleau, Marco Vecoli, Gerard J.m. Versteegh, Fatima Laggoun-défargeAbstract:Carboniferous (Viséan) coals from Dunbar, East Lothian, Scotland, contain well-preserved miospore and megaspore assemblages suggesting a lycopod-dominated forest ecosystem with some ferns, sphenopsids and pteridosperms. The low rank of the coals and the well defined microflora permit assessment of the palaeoenvironmental significance of lipid biomarkers during the Early Carboniferous. Rock-Eval, petrographic, and lipid analyses indicate a fully terrestrial depositional environment. Although we also present and discuss a wide diversity of other lipid biomarkers (alkanes, hopanoids, steroids), we focus on the terrestrial-derived biomarkers. Combustion-derived PAHs pyrene, fluoranthene, benzo[a]anthracene, chrysene and triphenylene indicate the occurrence of forest fires in the study areas during Early Carboniferous times. Alkyldibenzofurans are considered to derive from lichen-biomass. Retene, cadalene, simonellite, tetrahydroretene and kaurane are poorly specific and can derive from a variety of early Palaeozoic land plants. Abietane, phyllocladane, ent-beyerane and 4β(H)-eudesmane, as well as bisnorsimonellite, diaromatic totarane, diaromatic sempervirane and 2-methylretene, however, as yet had only been reported from conifers, which do not appear in the fossil record until the Late Carboniferous. Within the lower Carboniferous forest ecosystem, arborescent lycopsids and pteridosperms are proposed as alternative sources for these compounds.
Martin Sivek - One of the best experts on this subject based on the ideXlab platform.
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lateral development of coalification in the czech part of the upper silesian coal basin and its connection with gas deposits
International Journal of Coal Geology, 2009Co-Authors: Jana Kandarachevova, Lenka Sedlackova, Lada Hýlova, Jakub Jirasek, Martin SivekAbstract:Abstract The degree of coalification is an essential parameter influencing the quality of coal reserves. Modelling of the development of this parameter in the Czech part of the Upper Silesian Coal Basin (Carboniferous, Mississippian to Pennsylvanian — Lower Namurian to Westphalian A) revealed the distribution of coalification within the basin in all its stratal units. The grade of coalification was found in principle to be similar but its intensity in general decreases upwards into the hanging wall. Because of different areal extents of individual stratal units the degree of coalification is demonstrated on the oldest and areally most extensive unit — the Petřkovice Member. The studies and their results presented in this paper are based on more than 29,000 analyses of the dry and ash-free volatile matter ( V daf ) in coal samples from surface and underground boreholes drilled in the years 1946–2000. Three zones of enhanced coalification were distinguished: the Ostrava–Přibor Zone, the Rožnov–Frenstat Zone and the Přibor–Těsin Zone. These zones were found to correlate fairly well with the occurrence of gas deposits confined to the weathered Carboniferous Rock massif or its mantle. Consequently, the degree of coalification does not only determine the quality of coal reserves but may also be used as an auxiliary tool in the search for gas deposits in coal basins.
Lei Zhao - One of the best experts on this subject based on the ideXlab platform.
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Tectonic entities connection between West Junggar (NW China) and East Kazakhstan
Journal of Asian Earth Sciences, 2013Co-Authors: Lei ZhaoAbstract:Abstract West Junggar (NW China) and East Kazakhstan are situated in the southwest of the Central Asian orogenic belt (CAOB). Tectonic entities in the two areas share the same tectonic evolution history and make up the famous horseshoe-shaped orocline in Central Asia. This paper presents a newly compiled cross-border tectonic sketch map of West Junggar and East Kazakhstan and proposes the extension of the Chingiz–Tarbagatai belt and the North Balkhash-West Junggar belt. The Chingiz–Tarbagatai Belt in East Kazakhstan consists mainly of Middle-Late Ordovician differentiated volcanic Rocks, pyroclastic sediments and flysch; while in the Tarbagatai Mountain in China, Tarbagatai (Kujibai) ophiolite is newly found with zircon (gabbro) age of 478 ± 3 Ma and the Ordovician flysch metamorphosed to a greenschist facies is distinguished from Devonian–Carboniferous Rock associations. Therefore, the Early Paleozoic Chingiz–Tarbagatai belt of East Kazakhstan evidently extends to the northern part of West Junggar along the Tarbagatai orogenic belt. The North Balkhash-West Junggar belt lying south to the Chingiz–Tarbagatai belt is separated by the EW-trending Baiyanghe–Heshituoluogai depression in West Junggar. Early Ordovician–Early Silurian ophiolitic fragments and related pyroclastic sediments are widely exposed in Tekturmas, North Balkhash and Agadyr of East Kazashtan. Similarly, Early Paleozoic ophiolites have also been verified in Tangbale, Mayile, Baerluke, Darbut and Karamay of West Junggar in recent years. Therefore, nearly all ophiolites in West Junggar and East Kazakhstan are proved to have formed in Early Paleozoic, which suggests that the evolution of the paleo-ocean in the two areas reached its peak in the Early Paleozoic. Based on the ages of the Tangbale, Karamay and Hongguleleng ophiolites, an Early Paleozoic continental accretionary belt extending from Tangbale to Hongguleleng is determined at the NW margin of the Junggar basin for the first time. According to spatiotemporal comparison, ophiolites exposed in West Junggar and East Kazakhstan might originate from the same paleo-ocean tectonic region, and then the North Balkhash in East Kazakhstan and the West Junggar were offset for a long distance with respect to each other by the major Junggar dextral fault. Because of the large-scale accretion of continental crust before Silurian, the Late Paleozoic ocean in West Junggar and East Kazakhstan became smaller with residual nature, and extensive arc-basin-trench systems might be absent during the closure of this residual ocean.
Qianqian Guo - One of the best experts on this subject based on the ideXlab platform.
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A Devonian to Carboniferous intra-oceanic subduction system in Western Junggar, NW China
Lithos, 2011Co-Authors: Jien Zhang, Wenjiao Xiao, Chunming Han, Qigui Mao, Qianqian GuoAbstract:Abstract The Devonian and Carboniferous Rock assemblages in Western Junggar, southern Altaids, include ophiolitic melanges and coherent units. At Baijiantan, Yeyagou and Dagun Devonian gabbros and one group of volcanic Rocks (type I lava) generally crop out as blocks in a matrix of ultramafic Rocks and/or mudstone. They have a depleted light rare earth element (LREE) and mid-oceanic ridge basalt (MORB)-like signature with a small negative Nb anomaly, suggesting formation in a back-arc basin. Another group of volcanic Rocks (type II lava) from Baijiantan, Yeyagou, Western Karamay and Maliya includes alkaline basalt, basanite, andesite, dacite and trachyte that contain microphenocrysts of clinopyroxene–plagioclase, amygdales filled with chalcedony and calcite, and accessory pyrite and ilmenite. The type II lavas are further subdivided into five sub-types: (1) Type II 1 lava is strongly enriched in LREE with incompatible trace element ratios similar to oceanic island basalt (OIB), suggesting derivation from enriched mantle. (2) Type II 2 lava and tuff are slightly LREE-enriched, with a marked negative Nb anomaly and Th/Yb-enrichment indicating that they were generated in a supra-subduction zone (SSZ). (3) Type II 3 lava is also moderately enriched in LREE suggesting derivation from a more-enriched MORB mantle. (4) Type II 4 lava is enriched in LREE and has high Nb/Yb values close to those of OIB. It is extensively depleted in Nb suggesting a source containing a mixture of enriched and SSZ mantle. (5) Type II 5 lava has MORB-like REE patterns, and Nb/Yb and Th/Yb ratios. Based on field structural data, and the contemporaneity of the Baogutu adakite, a high-Mg diorite dike and the Miaoergou charnockite, these enriched and depleted magmatic features suggest generation in an intra-oceanic subduction zone influenced by ridge-trench interaction. The Altaids in Western Junggar are characterized by multiple intra-oceanic subduction systems, which may have continued to operate to the late Carboniferous.