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Elena S Rubanova - One of the best experts on this subject based on the ideXlab platform.
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crustal melting and magma mixing in a Continental Arc setting evidence from the yaloman intrusive complex in the gorny altai terrane central asian orogenic belt
Lithos, 2016Co-Authors: Ming Chen, Min Sun, Guochun Zhao, M M Buslov, Elena S Rubanova, Keda Cai, Anna V KulikovaAbstract:Abstract Granitoids and their hosted mafic enclaves may retain important information on crust–mantle interaction, and thus are significant for study of crustal growth and differentiation. An integrated petrological, geochronological and geochemical study on the granitoid plutons of the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt, was conducted to determine their source nature, petrogenesis and geodynamics. Mafic enclaves are common in the plutons, and a zircon U–Pb age (389 Ma ± 4 Ma) indicates that they are coeval with their granitoid hosts (ca. 393–387 Ma). Petrographic observations reveal that these mafic enclaves probably represent magmatic globules commingled with their host magmas. The relatively low SiO2 contents (46.0–60.7 wt.%) and high Mg# (38.9–56.5) further suggest that mantle-derived mafic melts served as a crucial component in the formation of these mafic enclaves. The granitoid hosts, including quartz diorites and granodiorites, are I-type in origin, possessing higher SiO2 contents (60.2–69.9 wt.%) and lower Mg# (32.0–44.2). Their zircon Hf and whole-rock Nd isotopic compositions indicate that the magmas were dominated by remelting of Neoproterozoic (0.79–1.07 Ga) crustal materials. Meanwhile, the geochemical modeling, together with the common occurrence of igneous mafic enclaves and the observation of reversely zoned plagioclases, suggests that magma mixing possibly contributed significantly to the geochemical variation of the granitoid hosts. Our results imply that mafic magmas from the mantle not only provided substantial heat to melt the lower crust, but also mixed with the crust-derived melts to form the diverse granitoids. The oxidizing and water-enriched properties inferred from the mineral assemblages and compositions imply that the granitoid plutons of the Yaloman intrusive complex were possibly formed in a Continental Arc-related setting, which is also supported by their geochemistry. The Devonian granitoids from the Gorny Altai terrane show remarkable temporal–spatial–petrogenetic affinities to the counterparts from the Altai-Mongolian terrane, indicating that these two terranes were possibly under subduction of the same oceanic plate (i.e., the Ob-Zaisan Ocean). The voluminous granitoids signify significant crustal recycling and growth as a response to the underplating of extensive mantle-derived basaltic melts.
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geochemical study of the cambrian ordovician meta sedimentary rocks from the northern altai mongolian terrane northwestern central asian orogenic belt implications on the provenance and tectonic setting
Journal of Asian Earth Sciences, 2014Co-Authors: Ming Chen, Guochun Zhao, M M Buslov, Elena S RubanovaAbstract:Abstract The Altai-Mongolian terrane (AM) is a key component of the Central Asian Orogenic Belt (CAOB), but its tectonic nature has been poorly constrained. This paper reports geochemical compositions of Cambrian–Ordovician meta-sedimentary rocks from the northern AM to trace their source nature and depositional setting, which in turn place constraints on the geodynamic evolution of the AM. The Cambrian–Ordovician meta-sedimentary rocks from the northern AM show variable major-element compositions, with negative correlation between SiO2 and TiO2, Al2O3, Fe2O3T, MgO and K2O. Their high ICV values (1.18–2.53) and relatively low CIA values (37.9–76.3) indicate that the sediments were immature and probably underwent mild to moderate chemical weathering. The low-SiO2 samples are characterized by relatively restricted SiO2/Al2O3 (mostly 2.60–6.07) and low Rb/Sr ratios (0.02–1.89), implying their proximal deposition without obvious sedimentary sorting and recycling. In contrast, the high-SiO2 samples show much higher SiO2/Al2O3 ratios (15.4–19.9) possibly due to sedimentary sorting and/or silicification. All these samples yield relatively high Al2O3/TiO2 ratios (15.6–22.8), strong LREEs/HREEs differentiation ((La/Yb)N = 4.86–10.7) and obvious negative Eu anomalies (δEu = 0.61–0.83). Combined with their Th/Sc, Zr/Sc, La/Th and Co/Th ratios comparable with intermediate-acidic magmatic rocks, we infer that these kinds of magmatic rocks served as a major source for the investigated meta-sedimentary rocks. The TiO2, Al2O3 and Fe2O3T + MgO concentrations are mostly higher than typical sediments from passive margin, and the Th/U, La/Sc, Th/Sc, Eu/Eu∗, Zr/Hf, Zr/Th and La/Th ratios are quite similar to sediments from Continental Arcs. These data suggest that the Cambrian–Ordovician meta-sedimentary rocks from the northern AM were most likely deposited in an environment related to a Continental Arc setting rather than a passive regime. These rocks show strong similarities to their counterparts in the Chinese Altai (CA, southern AM) and Tseel terrane (southeastern extension of the CA in western Mongolia) in terms of geochemical compositions and depositional setting. With combination of recent isotopic studies for detrital zircons, our data suggest that the AM probably represented a coherent accretionary prism along a Continental Arc in the early Paleozoic.
Fraukje M Brouwer - One of the best experts on this subject based on the ideXlab platform.
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meso neoproterozoic Arc related sediments of the xiahe group in the qinling block central china implications for the paleogeographic reconstruction of rodinia
Precambrian Research, 2021Co-Authors: Limin Zhao, J P Zheng, Hua Xiang, Guoqing Wang, Wenjiao Xiao, Ming Chen, Fraukje M BrouwerAbstract:Abstract The Meso-Neoproterozoic Rodinia supercontinent formed a coherent large landmass, which was later dispersed over all current major continents and a number of microcontinents. The Qinling block is a Precambrian Continental mass, located in the Qinling orogenic belt, which marks the junction of the North China and South China cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of metasedimentary rocks from the Xiahe Group, which is a key unit of the Precambrian basement in the Qinling block, to constrain the paleogeographic reconstruction of Rodinia. The studied metasedimentary rocks have detrital zircon ages of 3054–1082 Ma that peak at 1172 Ma and 1582 Ma. The protoliths of the metasedimentary rocks are mainly shales and wackes with maximum depositional ages from 1147 to 1082 Ma, representing a part of a Continental Arc-related sedimentary sequence. Combining our results with existing data, we propose that their protoliths constituted a sedimentary series including an older sequence of basement and a younger sequence with depositional ages between 1262 and 840 Ma. The detritus that is older than 1266 Ma was sourced from the Continental margin of the Indian craton, which was part of the Columbia supercontinent. There was a Paleo-Mesoproterozoic Continental nucleus in the Qinling block that split from the margin of the Indian craton during the breakup of Columbia. The source rocks for the younger detritus were Arc magmatic rocks in the Qinling block, which formed in a Continental Arc by oceanic lithosphere subduction during the assembly of Rodinia. A sequence of oceanic subduction beneath the Continental nucleus of the Qinling block (1262–981 Ma), Arc-continent collision between the Continental nucleus and the Indian craton (981–911 Ma), continuous subduction of oceanic crust beneath the block with formation of a mature volcanic Arc (929–833 Ma), and Continental rifting (833–774 Ma) during the formation of the Qinling block was identified. The block faced the Neoproterozoic ocean during the assembly of Rodinia, and finally rifted off the supercontinent during its breakup to form an isolated Arc terrane
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geochemical and zircon u pb hf isotopic study of metasedimentary rocks from the huangyuan group of the central qilian block nw china implications for paleogeographic reconstruction of rodinia
Precambrian Research, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Fraukje M BrouwerAbstract:Abstract We present a systematic study of micaschists and felsic gneisses from the Huangyuan Group of the Central Qilian block in NW China, with aims to unravel the connection with the Rodinia supercontinent. The micaschists have detrital zircon ages of 2895–928 Ma that peaking at 1.80–1.40 Ga. They show strongly increasing zircon eHf(t) values of −8.1 to +12.1 from 1.6 Ga to 1.4 Ga. Detrital zircon ages from the felsic gneisses are dominantly 960–913 Ma with eHf(t) values of −0.1 to −10.7. The micaschists have a wide range of whole-rock major element compositions, and the felsic gneisses have higher SiO2 contents, combined with lower other major element contents than those of the micaschists. All samples have trace element compositions consistent with upper Continental crustal origin. The protoliths of the micaschists are dominantly shales and minor wackes with maximum depositional ages from ca. 1317 to 928 Ma. The protoliths of the felsic gneisses are mostly wackes with a maximum depositional age of ca. 927 Ma. The source materials for these metasedimentary rocks originated from intermediate to felsic igneous rocks. The variable maximum depositional ages of the metasedimentary rocks in the Huangyuan Group indicate that their protoliths constituted a sedimentary series with a long history of deposition starting at ca. 1317 Ma in an oceanic island Arc-related basin that developed through a transitional Continental Arc-related basin into an active Continental marginal basin at ca. 927 Ma. It is inferred that the 1795–1321 Ma detritus was sourced from juvenile Arc crust at the margin of the Indian or the Western Australian craton. The source rocks for 1317–913 Ma detritus were Arc magmatic rocks formed during assembly of Rodinia. A sequence of initial intra-oceanic subduction (ca. 1317–967 Ma) and continuous oceanic crust-continent subduction with formation of a mature Continental Arc (ca. 967–896 Ma) at the margin of Rodinia during the formation of the Central Qilian block is suggested.
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early neoproterozoic magmatism in the central qilian block nw china geochronological and petrogenetic constraints for rodinia assembly
Geological Society of America Bulletin, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Ke Wang, Fraukje M BrouwerAbstract:The supercontinent Rodinia existed as a coherent large landmass from 900 to 750 Ma and is now dispersed over all current major continents. Controversy has long surrounded the reconstructions of the East Asian blocks in Rodinia, especially the South China craton and nearby microcontinents. The Central Qilian block is a Precambrian microcontinent in the early Paleozoic Qilian orogenic belt, which is located in the northeastern part of the Qinghai-Xizang (Tibet) Plateau and marks the junction of the North China, South China and Tarim cratons. The formation and tectonic affinity of the Precambrian basement in the Central Qilian block is unclear, which affects our understanding of the assembly of Rodinia. The Huangyuan Group and the Maxianshan Group crop out in the eastern part of the block and represent the lower part of the basement. In this paper, we present a systematic study of the petrology, whole-rock geochemistry, and geochronology of amphibolites and orthogneisses from the Huangyuan and Maxianshan Groups. The protolith of the amphibolites was tholeiitic and calc-alkaline gabbro or gabbroic diorite formed in a Continental Arc environment, with laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) zircon U-Pb ages of 967–957 Ma, a wide range of eHf(t) values of –3.74 to +5.06 and TDM1 model ages peaking at 1470 Ma and 1607 Ma. Minor inherited zircon grains with older ages of 1207–1515 Ma were collected from the amphibolites. The primitive magma was derived from partial melting of a spinel-facies fertile (lherzolite) lithospheric mantle that was modified by fluids and melts from a subducted slab. Fractionation of olivine, Fe-Ti oxides and plagioclase played a dominant role in the magma differentiation for gabbroic rocks in the Huangyuan Group, while fractionation of olivine and clinopyroxene controlled differentiation to form Maxianshan Group gabbros. The protolith of orthogneisses includes weakly peraluminous I-type and A2-type granites with consistent LA-ICPMS zircon U-Pb ages of 963–936 Ma, a wide range of eHf(t) values of –3.86 to +6.15 and TDM2 model age peaks at 2001 Ma and 1772 Ma. A few inherited zircon grains yield ages of 1033–2558 Ma. The peraluminous I-type granites resulted from a low-pressure partial melting process and the peraluminous A-type granites were derived from a charnockite source heated by large-scale magmatic underplating. Fractionation of plagioclase, biotite, and K-feldspar from the magma played the main role during the generation of the granitoids. The intrusion of these granites is related to a back-Arc extension. It is inferred that the lower part of Precambrian basement of the Central Qilian block is composed mainly of early Neoproterozoic rock assemblages formed in a trench-Arc-basin system during the assembly of the Rodinia supercontinent, with probable existence of late Paleoproterozoic to Mesoproterozoic Continental nuclei. Combining our results with existing data, we identify a sequence of initial intra-oceanic subduction (ca. 1121–967 Ma) in front of a Continental nucleus, continuous subduction of oceanic crust beneath the Continental mass with formation of a mature Continental Arc and a back-Arc basin (ca. 967–896 Ma) and Continental rifting (
Continental Arc after ca. 967 Ma, the Central Qilian block was located at the margin of Rodinia and faced the Neoproterozoic Mirovoi Ocean. The breakup of the supercontinent left the Central Qilian block as a late Neoproterozoic isolated Arc terrane.
Wenjiao Xiao - One of the best experts on this subject based on the ideXlab platform.
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meso neoproterozoic Arc related sediments of the xiahe group in the qinling block central china implications for the paleogeographic reconstruction of rodinia
Precambrian Research, 2021Co-Authors: Limin Zhao, J P Zheng, Hua Xiang, Guoqing Wang, Wenjiao Xiao, Ming Chen, Fraukje M BrouwerAbstract:Abstract The Meso-Neoproterozoic Rodinia supercontinent formed a coherent large landmass, which was later dispersed over all current major continents and a number of microcontinents. The Qinling block is a Precambrian Continental mass, located in the Qinling orogenic belt, which marks the junction of the North China and South China cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of metasedimentary rocks from the Xiahe Group, which is a key unit of the Precambrian basement in the Qinling block, to constrain the paleogeographic reconstruction of Rodinia. The studied metasedimentary rocks have detrital zircon ages of 3054–1082 Ma that peak at 1172 Ma and 1582 Ma. The protoliths of the metasedimentary rocks are mainly shales and wackes with maximum depositional ages from 1147 to 1082 Ma, representing a part of a Continental Arc-related sedimentary sequence. Combining our results with existing data, we propose that their protoliths constituted a sedimentary series including an older sequence of basement and a younger sequence with depositional ages between 1262 and 840 Ma. The detritus that is older than 1266 Ma was sourced from the Continental margin of the Indian craton, which was part of the Columbia supercontinent. There was a Paleo-Mesoproterozoic Continental nucleus in the Qinling block that split from the margin of the Indian craton during the breakup of Columbia. The source rocks for the younger detritus were Arc magmatic rocks in the Qinling block, which formed in a Continental Arc by oceanic lithosphere subduction during the assembly of Rodinia. A sequence of oceanic subduction beneath the Continental nucleus of the Qinling block (1262–981 Ma), Arc-continent collision between the Continental nucleus and the Indian craton (981–911 Ma), continuous subduction of oceanic crust beneath the block with formation of a mature volcanic Arc (929–833 Ma), and Continental rifting (833–774 Ma) during the formation of the Qinling block was identified. The block faced the Neoproterozoic ocean during the assembly of Rodinia, and finally rifted off the supercontinent during its breakup to form an isolated Arc terrane
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geochemical and zircon u pb hf isotopic study of metasedimentary rocks from the huangyuan group of the central qilian block nw china implications for paleogeographic reconstruction of rodinia
Precambrian Research, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Fraukje M BrouwerAbstract:Abstract We present a systematic study of micaschists and felsic gneisses from the Huangyuan Group of the Central Qilian block in NW China, with aims to unravel the connection with the Rodinia supercontinent. The micaschists have detrital zircon ages of 2895–928 Ma that peaking at 1.80–1.40 Ga. They show strongly increasing zircon eHf(t) values of −8.1 to +12.1 from 1.6 Ga to 1.4 Ga. Detrital zircon ages from the felsic gneisses are dominantly 960–913 Ma with eHf(t) values of −0.1 to −10.7. The micaschists have a wide range of whole-rock major element compositions, and the felsic gneisses have higher SiO2 contents, combined with lower other major element contents than those of the micaschists. All samples have trace element compositions consistent with upper Continental crustal origin. The protoliths of the micaschists are dominantly shales and minor wackes with maximum depositional ages from ca. 1317 to 928 Ma. The protoliths of the felsic gneisses are mostly wackes with a maximum depositional age of ca. 927 Ma. The source materials for these metasedimentary rocks originated from intermediate to felsic igneous rocks. The variable maximum depositional ages of the metasedimentary rocks in the Huangyuan Group indicate that their protoliths constituted a sedimentary series with a long history of deposition starting at ca. 1317 Ma in an oceanic island Arc-related basin that developed through a transitional Continental Arc-related basin into an active Continental marginal basin at ca. 927 Ma. It is inferred that the 1795–1321 Ma detritus was sourced from juvenile Arc crust at the margin of the Indian or the Western Australian craton. The source rocks for 1317–913 Ma detritus were Arc magmatic rocks formed during assembly of Rodinia. A sequence of initial intra-oceanic subduction (ca. 1317–967 Ma) and continuous oceanic crust-continent subduction with formation of a mature Continental Arc (ca. 967–896 Ma) at the margin of Rodinia during the formation of the Central Qilian block is suggested.
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early neoproterozoic magmatism in the central qilian block nw china geochronological and petrogenetic constraints for rodinia assembly
Geological Society of America Bulletin, 2020Co-Authors: Wenjiao Xiao, J P Zheng, Ke Wang, Fraukje M BrouwerAbstract:The supercontinent Rodinia existed as a coherent large landmass from 900 to 750 Ma and is now dispersed over all current major continents. Controversy has long surrounded the reconstructions of the East Asian blocks in Rodinia, especially the South China craton and nearby microcontinents. The Central Qilian block is a Precambrian microcontinent in the early Paleozoic Qilian orogenic belt, which is located in the northeastern part of the Qinghai-Xizang (Tibet) Plateau and marks the junction of the North China, South China and Tarim cratons. The formation and tectonic affinity of the Precambrian basement in the Central Qilian block is unclear, which affects our understanding of the assembly of Rodinia. The Huangyuan Group and the Maxianshan Group crop out in the eastern part of the block and represent the lower part of the basement. In this paper, we present a systematic study of the petrology, whole-rock geochemistry, and geochronology of amphibolites and orthogneisses from the Huangyuan and Maxianshan Groups. The protolith of the amphibolites was tholeiitic and calc-alkaline gabbro or gabbroic diorite formed in a Continental Arc environment, with laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) zircon U-Pb ages of 967–957 Ma, a wide range of eHf(t) values of –3.74 to +5.06 and TDM1 model ages peaking at 1470 Ma and 1607 Ma. Minor inherited zircon grains with older ages of 1207–1515 Ma were collected from the amphibolites. The primitive magma was derived from partial melting of a spinel-facies fertile (lherzolite) lithospheric mantle that was modified by fluids and melts from a subducted slab. Fractionation of olivine, Fe-Ti oxides and plagioclase played a dominant role in the magma differentiation for gabbroic rocks in the Huangyuan Group, while fractionation of olivine and clinopyroxene controlled differentiation to form Maxianshan Group gabbros. The protolith of orthogneisses includes weakly peraluminous I-type and A2-type granites with consistent LA-ICPMS zircon U-Pb ages of 963–936 Ma, a wide range of eHf(t) values of –3.86 to +6.15 and TDM2 model age peaks at 2001 Ma and 1772 Ma. A few inherited zircon grains yield ages of 1033–2558 Ma. The peraluminous I-type granites resulted from a low-pressure partial melting process and the peraluminous A-type granites were derived from a charnockite source heated by large-scale magmatic underplating. Fractionation of plagioclase, biotite, and K-feldspar from the magma played the main role during the generation of the granitoids. The intrusion of these granites is related to a back-Arc extension. It is inferred that the lower part of Precambrian basement of the Central Qilian block is composed mainly of early Neoproterozoic rock assemblages formed in a trench-Arc-basin system during the assembly of the Rodinia supercontinent, with probable existence of late Paleoproterozoic to Mesoproterozoic Continental nuclei. Combining our results with existing data, we identify a sequence of initial intra-oceanic subduction (ca. 1121–967 Ma) in front of a Continental nucleus, continuous subduction of oceanic crust beneath the Continental mass with formation of a mature Continental Arc and a back-Arc basin (ca. 967–896 Ma) and Continental rifting (
Continental Arc after ca. 967 Ma, the Central Qilian block was located at the margin of Rodinia and faced the Neoproterozoic Mirovoi Ocean. The breakup of the supercontinent left the Central Qilian block as a late Neoproterozoic isolated Arc terrane.
Ming Chen - One of the best experts on this subject based on the ideXlab platform.
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meso neoproterozoic Arc related sediments of the xiahe group in the qinling block central china implications for the paleogeographic reconstruction of rodinia
Precambrian Research, 2021Co-Authors: Limin Zhao, J P Zheng, Hua Xiang, Guoqing Wang, Wenjiao Xiao, Ming Chen, Fraukje M BrouwerAbstract:Abstract The Meso-Neoproterozoic Rodinia supercontinent formed a coherent large landmass, which was later dispersed over all current major continents and a number of microcontinents. The Qinling block is a Precambrian Continental mass, located in the Qinling orogenic belt, which marks the junction of the North China and South China cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of metasedimentary rocks from the Xiahe Group, which is a key unit of the Precambrian basement in the Qinling block, to constrain the paleogeographic reconstruction of Rodinia. The studied metasedimentary rocks have detrital zircon ages of 3054–1082 Ma that peak at 1172 Ma and 1582 Ma. The protoliths of the metasedimentary rocks are mainly shales and wackes with maximum depositional ages from 1147 to 1082 Ma, representing a part of a Continental Arc-related sedimentary sequence. Combining our results with existing data, we propose that their protoliths constituted a sedimentary series including an older sequence of basement and a younger sequence with depositional ages between 1262 and 840 Ma. The detritus that is older than 1266 Ma was sourced from the Continental margin of the Indian craton, which was part of the Columbia supercontinent. There was a Paleo-Mesoproterozoic Continental nucleus in the Qinling block that split from the margin of the Indian craton during the breakup of Columbia. The source rocks for the younger detritus were Arc magmatic rocks in the Qinling block, which formed in a Continental Arc by oceanic lithosphere subduction during the assembly of Rodinia. A sequence of oceanic subduction beneath the Continental nucleus of the Qinling block (1262–981 Ma), Arc-continent collision between the Continental nucleus and the Indian craton (981–911 Ma), continuous subduction of oceanic crust beneath the block with formation of a mature volcanic Arc (929–833 Ma), and Continental rifting (833–774 Ma) during the formation of the Qinling block was identified. The block faced the Neoproterozoic ocean during the assembly of Rodinia, and finally rifted off the supercontinent during its breakup to form an isolated Arc terrane
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crustal melting and magma mixing in a Continental Arc setting evidence from the yaloman intrusive complex in the gorny altai terrane central asian orogenic belt
Lithos, 2016Co-Authors: Ming Chen, Min Sun, Guochun Zhao, M M Buslov, Elena S Rubanova, Keda Cai, Anna V KulikovaAbstract:Abstract Granitoids and their hosted mafic enclaves may retain important information on crust–mantle interaction, and thus are significant for study of crustal growth and differentiation. An integrated petrological, geochronological and geochemical study on the granitoid plutons of the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt, was conducted to determine their source nature, petrogenesis and geodynamics. Mafic enclaves are common in the plutons, and a zircon U–Pb age (389 Ma ± 4 Ma) indicates that they are coeval with their granitoid hosts (ca. 393–387 Ma). Petrographic observations reveal that these mafic enclaves probably represent magmatic globules commingled with their host magmas. The relatively low SiO2 contents (46.0–60.7 wt.%) and high Mg# (38.9–56.5) further suggest that mantle-derived mafic melts served as a crucial component in the formation of these mafic enclaves. The granitoid hosts, including quartz diorites and granodiorites, are I-type in origin, possessing higher SiO2 contents (60.2–69.9 wt.%) and lower Mg# (32.0–44.2). Their zircon Hf and whole-rock Nd isotopic compositions indicate that the magmas were dominated by remelting of Neoproterozoic (0.79–1.07 Ga) crustal materials. Meanwhile, the geochemical modeling, together with the common occurrence of igneous mafic enclaves and the observation of reversely zoned plagioclases, suggests that magma mixing possibly contributed significantly to the geochemical variation of the granitoid hosts. Our results imply that mafic magmas from the mantle not only provided substantial heat to melt the lower crust, but also mixed with the crust-derived melts to form the diverse granitoids. The oxidizing and water-enriched properties inferred from the mineral assemblages and compositions imply that the granitoid plutons of the Yaloman intrusive complex were possibly formed in a Continental Arc-related setting, which is also supported by their geochemistry. The Devonian granitoids from the Gorny Altai terrane show remarkable temporal–spatial–petrogenetic affinities to the counterparts from the Altai-Mongolian terrane, indicating that these two terranes were possibly under subduction of the same oceanic plate (i.e., the Ob-Zaisan Ocean). The voluminous granitoids signify significant crustal recycling and growth as a response to the underplating of extensive mantle-derived basaltic melts.
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geochemical study of the cambrian ordovician meta sedimentary rocks from the northern altai mongolian terrane northwestern central asian orogenic belt implications on the provenance and tectonic setting
Journal of Asian Earth Sciences, 2014Co-Authors: Ming Chen, Guochun Zhao, M M Buslov, Elena S RubanovaAbstract:Abstract The Altai-Mongolian terrane (AM) is a key component of the Central Asian Orogenic Belt (CAOB), but its tectonic nature has been poorly constrained. This paper reports geochemical compositions of Cambrian–Ordovician meta-sedimentary rocks from the northern AM to trace their source nature and depositional setting, which in turn place constraints on the geodynamic evolution of the AM. The Cambrian–Ordovician meta-sedimentary rocks from the northern AM show variable major-element compositions, with negative correlation between SiO2 and TiO2, Al2O3, Fe2O3T, MgO and K2O. Their high ICV values (1.18–2.53) and relatively low CIA values (37.9–76.3) indicate that the sediments were immature and probably underwent mild to moderate chemical weathering. The low-SiO2 samples are characterized by relatively restricted SiO2/Al2O3 (mostly 2.60–6.07) and low Rb/Sr ratios (0.02–1.89), implying their proximal deposition without obvious sedimentary sorting and recycling. In contrast, the high-SiO2 samples show much higher SiO2/Al2O3 ratios (15.4–19.9) possibly due to sedimentary sorting and/or silicification. All these samples yield relatively high Al2O3/TiO2 ratios (15.6–22.8), strong LREEs/HREEs differentiation ((La/Yb)N = 4.86–10.7) and obvious negative Eu anomalies (δEu = 0.61–0.83). Combined with their Th/Sc, Zr/Sc, La/Th and Co/Th ratios comparable with intermediate-acidic magmatic rocks, we infer that these kinds of magmatic rocks served as a major source for the investigated meta-sedimentary rocks. The TiO2, Al2O3 and Fe2O3T + MgO concentrations are mostly higher than typical sediments from passive margin, and the Th/U, La/Sc, Th/Sc, Eu/Eu∗, Zr/Hf, Zr/Th and La/Th ratios are quite similar to sediments from Continental Arcs. These data suggest that the Cambrian–Ordovician meta-sedimentary rocks from the northern AM were most likely deposited in an environment related to a Continental Arc setting rather than a passive regime. These rocks show strong similarities to their counterparts in the Chinese Altai (CA, southern AM) and Tseel terrane (southeastern extension of the CA in western Mongolia) in terms of geochemical compositions and depositional setting. With combination of recent isotopic studies for detrital zircons, our data suggest that the AM probably represented a coherent accretionary prism along a Continental Arc in the early Paleozoic.
M M Buslov - One of the best experts on this subject based on the ideXlab platform.
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crustal melting and magma mixing in a Continental Arc setting evidence from the yaloman intrusive complex in the gorny altai terrane central asian orogenic belt
Lithos, 2016Co-Authors: Ming Chen, Min Sun, Guochun Zhao, M M Buslov, Elena S Rubanova, Keda Cai, Anna V KulikovaAbstract:Abstract Granitoids and their hosted mafic enclaves may retain important information on crust–mantle interaction, and thus are significant for study of crustal growth and differentiation. An integrated petrological, geochronological and geochemical study on the granitoid plutons of the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt, was conducted to determine their source nature, petrogenesis and geodynamics. Mafic enclaves are common in the plutons, and a zircon U–Pb age (389 Ma ± 4 Ma) indicates that they are coeval with their granitoid hosts (ca. 393–387 Ma). Petrographic observations reveal that these mafic enclaves probably represent magmatic globules commingled with their host magmas. The relatively low SiO2 contents (46.0–60.7 wt.%) and high Mg# (38.9–56.5) further suggest that mantle-derived mafic melts served as a crucial component in the formation of these mafic enclaves. The granitoid hosts, including quartz diorites and granodiorites, are I-type in origin, possessing higher SiO2 contents (60.2–69.9 wt.%) and lower Mg# (32.0–44.2). Their zircon Hf and whole-rock Nd isotopic compositions indicate that the magmas were dominated by remelting of Neoproterozoic (0.79–1.07 Ga) crustal materials. Meanwhile, the geochemical modeling, together with the common occurrence of igneous mafic enclaves and the observation of reversely zoned plagioclases, suggests that magma mixing possibly contributed significantly to the geochemical variation of the granitoid hosts. Our results imply that mafic magmas from the mantle not only provided substantial heat to melt the lower crust, but also mixed with the crust-derived melts to form the diverse granitoids. The oxidizing and water-enriched properties inferred from the mineral assemblages and compositions imply that the granitoid plutons of the Yaloman intrusive complex were possibly formed in a Continental Arc-related setting, which is also supported by their geochemistry. The Devonian granitoids from the Gorny Altai terrane show remarkable temporal–spatial–petrogenetic affinities to the counterparts from the Altai-Mongolian terrane, indicating that these two terranes were possibly under subduction of the same oceanic plate (i.e., the Ob-Zaisan Ocean). The voluminous granitoids signify significant crustal recycling and growth as a response to the underplating of extensive mantle-derived basaltic melts.
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geochemical study of the cambrian ordovician meta sedimentary rocks from the northern altai mongolian terrane northwestern central asian orogenic belt implications on the provenance and tectonic setting
Journal of Asian Earth Sciences, 2014Co-Authors: Ming Chen, Guochun Zhao, M M Buslov, Elena S RubanovaAbstract:Abstract The Altai-Mongolian terrane (AM) is a key component of the Central Asian Orogenic Belt (CAOB), but its tectonic nature has been poorly constrained. This paper reports geochemical compositions of Cambrian–Ordovician meta-sedimentary rocks from the northern AM to trace their source nature and depositional setting, which in turn place constraints on the geodynamic evolution of the AM. The Cambrian–Ordovician meta-sedimentary rocks from the northern AM show variable major-element compositions, with negative correlation between SiO2 and TiO2, Al2O3, Fe2O3T, MgO and K2O. Their high ICV values (1.18–2.53) and relatively low CIA values (37.9–76.3) indicate that the sediments were immature and probably underwent mild to moderate chemical weathering. The low-SiO2 samples are characterized by relatively restricted SiO2/Al2O3 (mostly 2.60–6.07) and low Rb/Sr ratios (0.02–1.89), implying their proximal deposition without obvious sedimentary sorting and recycling. In contrast, the high-SiO2 samples show much higher SiO2/Al2O3 ratios (15.4–19.9) possibly due to sedimentary sorting and/or silicification. All these samples yield relatively high Al2O3/TiO2 ratios (15.6–22.8), strong LREEs/HREEs differentiation ((La/Yb)N = 4.86–10.7) and obvious negative Eu anomalies (δEu = 0.61–0.83). Combined with their Th/Sc, Zr/Sc, La/Th and Co/Th ratios comparable with intermediate-acidic magmatic rocks, we infer that these kinds of magmatic rocks served as a major source for the investigated meta-sedimentary rocks. The TiO2, Al2O3 and Fe2O3T + MgO concentrations are mostly higher than typical sediments from passive margin, and the Th/U, La/Sc, Th/Sc, Eu/Eu∗, Zr/Hf, Zr/Th and La/Th ratios are quite similar to sediments from Continental Arcs. These data suggest that the Cambrian–Ordovician meta-sedimentary rocks from the northern AM were most likely deposited in an environment related to a Continental Arc setting rather than a passive regime. These rocks show strong similarities to their counterparts in the Chinese Altai (CA, southern AM) and Tseel terrane (southeastern extension of the CA in western Mongolia) in terms of geochemical compositions and depositional setting. With combination of recent isotopic studies for detrital zircons, our data suggest that the AM probably represented a coherent accretionary prism along a Continental Arc in the early Paleozoic.