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Rongguo Zheng - One of the best experts on this subject based on the ideXlab platform.

  • early paleozoic tectonic evolution of the northern west junggar nw china constraints from early cambrian middle silurian felsic plutons of the chagantaolegai ophiolitic melange
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng, Jianhua Liu, Jin Zhang
    Abstract:

    Abstract The early Paleozoic tectonic evolution of the Junggar Ocean (a major branch of the southern Paleo-Asian Ocean (PAO)) remains a topic of debate. This study mapped the Chagantaolegai ophiolitic melange (COM) in the northern West Junggar (NWJ) on a large scale and identified several tectonically juxtaposed lithotectonic units, including the ophiolite suite and felsic plutons. The ophiolite suite mainly comprises serpentinized ultramafic rock, pyroxenolite, gabbro, dolerite, Plagiogranite, basalt, volcanic rock, and radiolarian chert. Zircon U–Pb ages for two Plagiogranite samples yielded ages of 515 ± 4 Ma and 513 ± 6 Ma, constraining the existence of the Junggar Ocean to the Early Cambrian at least. The felsic plutons can be subdivided into two groups. Group I (503–481 Ma), which intruded into the COM, shows low-K, calc-alkaline features with remarkable depletion of Nb, Ta, and Ti, resembling rocks formed in an intra-oceanic arc. Group II (435–428 Ma) was found on both sides of the COM and displays high-K, calc-alkaline series characteristics, similar to the Silurian to Early Devonian A-type granites in the NWJ, implying a post-collisional environment. Based on a combination of existing observations and our new observations and data with regional geological evidence, our new data indicate that the NWJ underwent a transition from the tectonic processes of seafloor spreading and subduction to arc–arc collision and post-collisional extension during the Early Cambrian–Early Devonian.

  • evolution of the early paleozoic hongguleleng balkybey ocean evidence from the hebukesaier ophiolitic melange in the northern west junggar nw china
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng
    Abstract:

    Abstract The Hebukesaier ophiolitic melange is located in West Junggar, northwest China. Based on detailed field mapping, we identified three rock assemblages in the melange: ophiolite, seamount, and rhyolite porphyry. The ophiolite comprises mainly metaperidotites, pyroxenites, gabbros, dolerites, diabase dike, Plagiogranites, basalts and cherts. Two gabbro and one Plagiogranite samples have ages of 512 ± 9 Ma, 505 ± 5 Ma and 502 ± 5 Ma, respectively, which constrain the formation time of the oceanic crust. The geochemical characteristics of the basaltic rocks (gabbros and basalts) suggest that the ophiolite formed by intrusion of mid-ocean ridge melts. The ocean island basalts occur as tectonic blocks within the melanges that coexist closely with marble, siliceous mudstone and chert, with formation characteristics of a seamount. The Early Silurian rhyolite porphyry samples (435 ± 2 Ma) are characterized by high Al2O3 (14.30–15.31 wt%), Sr/Y (22.26–78.42) and (La/Yb)N (20.27–24.24), similar to those of Late Silurian–Early Devonian adakitic rocks (420–411 Ma) from the Xiemisitai Mountains. Furthermore, the rhyolite porphyry samples display high positive eHf(t) values and low Mg values as well as low concentrations of compatible elements (Cr, Co and Ni), suggesting that the rhyolite porphyry originated from partial melting of lower juvenile crust. The rhyolite porphyry displays spatio-temporal characteristics similar to those of the post-collision plutons (434–405 Ma) of the Xiemisitai Mountains. The rhyolite porphyry intruded the ophiolite in the melange, implying that the Hongguleleng–Balkybey Ocean closed prior to the Early Silurian. Our results, combined with other geological evidence, indicate that the northern West Junggar underwent ocean basin spreading, intra-oceanic subduction, arc–arc collision, the closure of the ocean and post-collisional extension during the Middle Cambrian–Early Devonian.

Gain S. - One of the best experts on this subject based on the ideXlab platform.

  • Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran
    'Geological Society of America', 2020
    Co-Authors: Moghadam, Hadi Shafaii, Stern R. J., Griffin W. L., Khedr M. Z., Kirchenbaur M., Ottley C. J., Whattam S. A., Kimura J.-i., Ghorbani G., Gain S.
    Abstract:

    How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harzburgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10−63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, Plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including Plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99−92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for ∼7 m.y. THO igneous rocks have variable εNd(t) of +5.7 to +8.2 and εHf(t) ranging from +14.9 to +21.5; zircons have εHf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation

  • Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran
    'Geological Society of America', 2020
    Co-Authors: Moghadam, Hadi Shafaii, Stern R. J., Griffin W. L., Khedr M. Z., Kirchenbaur M., Ottley C. J., Whattam S. A., Ghorbani G., Kimura J-, Gain S.
    Abstract:

    How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harz burgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10-63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, Plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including Plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99-92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for similar to 7 m.y. THO igneous rocks have variable epsilon Nd(t) of +5.7 to +8.2 and epsilon Hf(t) ranging from +14.9 to +21.5; zircons have epsilon Hf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation

Yaqi Yang - One of the best experts on this subject based on the ideXlab platform.

  • early paleozoic tectonic evolution of the northern west junggar nw china constraints from early cambrian middle silurian felsic plutons of the chagantaolegai ophiolitic melange
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng, Jianhua Liu, Jin Zhang
    Abstract:

    Abstract The early Paleozoic tectonic evolution of the Junggar Ocean (a major branch of the southern Paleo-Asian Ocean (PAO)) remains a topic of debate. This study mapped the Chagantaolegai ophiolitic melange (COM) in the northern West Junggar (NWJ) on a large scale and identified several tectonically juxtaposed lithotectonic units, including the ophiolite suite and felsic plutons. The ophiolite suite mainly comprises serpentinized ultramafic rock, pyroxenolite, gabbro, dolerite, Plagiogranite, basalt, volcanic rock, and radiolarian chert. Zircon U–Pb ages for two Plagiogranite samples yielded ages of 515 ± 4 Ma and 513 ± 6 Ma, constraining the existence of the Junggar Ocean to the Early Cambrian at least. The felsic plutons can be subdivided into two groups. Group I (503–481 Ma), which intruded into the COM, shows low-K, calc-alkaline features with remarkable depletion of Nb, Ta, and Ti, resembling rocks formed in an intra-oceanic arc. Group II (435–428 Ma) was found on both sides of the COM and displays high-K, calc-alkaline series characteristics, similar to the Silurian to Early Devonian A-type granites in the NWJ, implying a post-collisional environment. Based on a combination of existing observations and our new observations and data with regional geological evidence, our new data indicate that the NWJ underwent a transition from the tectonic processes of seafloor spreading and subduction to arc–arc collision and post-collisional extension during the Early Cambrian–Early Devonian.

  • evolution of the early paleozoic hongguleleng balkybey ocean evidence from the hebukesaier ophiolitic melange in the northern west junggar nw china
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng
    Abstract:

    Abstract The Hebukesaier ophiolitic melange is located in West Junggar, northwest China. Based on detailed field mapping, we identified three rock assemblages in the melange: ophiolite, seamount, and rhyolite porphyry. The ophiolite comprises mainly metaperidotites, pyroxenites, gabbros, dolerites, diabase dike, Plagiogranites, basalts and cherts. Two gabbro and one Plagiogranite samples have ages of 512 ± 9 Ma, 505 ± 5 Ma and 502 ± 5 Ma, respectively, which constrain the formation time of the oceanic crust. The geochemical characteristics of the basaltic rocks (gabbros and basalts) suggest that the ophiolite formed by intrusion of mid-ocean ridge melts. The ocean island basalts occur as tectonic blocks within the melanges that coexist closely with marble, siliceous mudstone and chert, with formation characteristics of a seamount. The Early Silurian rhyolite porphyry samples (435 ± 2 Ma) are characterized by high Al2O3 (14.30–15.31 wt%), Sr/Y (22.26–78.42) and (La/Yb)N (20.27–24.24), similar to those of Late Silurian–Early Devonian adakitic rocks (420–411 Ma) from the Xiemisitai Mountains. Furthermore, the rhyolite porphyry samples display high positive eHf(t) values and low Mg values as well as low concentrations of compatible elements (Cr, Co and Ni), suggesting that the rhyolite porphyry originated from partial melting of lower juvenile crust. The rhyolite porphyry displays spatio-temporal characteristics similar to those of the post-collision plutons (434–405 Ma) of the Xiemisitai Mountains. The rhyolite porphyry intruded the ophiolite in the melange, implying that the Hongguleleng–Balkybey Ocean closed prior to the Early Silurian. Our results, combined with other geological evidence, indicate that the northern West Junggar underwent ocean basin spreading, intra-oceanic subduction, arc–arc collision, the closure of the ocean and post-collisional extension during the Middle Cambrian–Early Devonian.

Lei Zhao - One of the best experts on this subject based on the ideXlab platform.

  • early paleozoic tectonic evolution of the northern west junggar nw china constraints from early cambrian middle silurian felsic plutons of the chagantaolegai ophiolitic melange
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng, Jianhua Liu, Jin Zhang
    Abstract:

    Abstract The early Paleozoic tectonic evolution of the Junggar Ocean (a major branch of the southern Paleo-Asian Ocean (PAO)) remains a topic of debate. This study mapped the Chagantaolegai ophiolitic melange (COM) in the northern West Junggar (NWJ) on a large scale and identified several tectonically juxtaposed lithotectonic units, including the ophiolite suite and felsic plutons. The ophiolite suite mainly comprises serpentinized ultramafic rock, pyroxenolite, gabbro, dolerite, Plagiogranite, basalt, volcanic rock, and radiolarian chert. Zircon U–Pb ages for two Plagiogranite samples yielded ages of 515 ± 4 Ma and 513 ± 6 Ma, constraining the existence of the Junggar Ocean to the Early Cambrian at least. The felsic plutons can be subdivided into two groups. Group I (503–481 Ma), which intruded into the COM, shows low-K, calc-alkaline features with remarkable depletion of Nb, Ta, and Ti, resembling rocks formed in an intra-oceanic arc. Group II (435–428 Ma) was found on both sides of the COM and displays high-K, calc-alkaline series characteristics, similar to the Silurian to Early Devonian A-type granites in the NWJ, implying a post-collisional environment. Based on a combination of existing observations and our new observations and data with regional geological evidence, our new data indicate that the NWJ underwent a transition from the tectonic processes of seafloor spreading and subduction to arc–arc collision and post-collisional extension during the Early Cambrian–Early Devonian.

  • evolution of the early paleozoic hongguleleng balkybey ocean evidence from the hebukesaier ophiolitic melange in the northern west junggar nw china
    Lithos, 2019
    Co-Authors: Yaqi Yang, Lei Zhao, Rongguo Zheng
    Abstract:

    Abstract The Hebukesaier ophiolitic melange is located in West Junggar, northwest China. Based on detailed field mapping, we identified three rock assemblages in the melange: ophiolite, seamount, and rhyolite porphyry. The ophiolite comprises mainly metaperidotites, pyroxenites, gabbros, dolerites, diabase dike, Plagiogranites, basalts and cherts. Two gabbro and one Plagiogranite samples have ages of 512 ± 9 Ma, 505 ± 5 Ma and 502 ± 5 Ma, respectively, which constrain the formation time of the oceanic crust. The geochemical characteristics of the basaltic rocks (gabbros and basalts) suggest that the ophiolite formed by intrusion of mid-ocean ridge melts. The ocean island basalts occur as tectonic blocks within the melanges that coexist closely with marble, siliceous mudstone and chert, with formation characteristics of a seamount. The Early Silurian rhyolite porphyry samples (435 ± 2 Ma) are characterized by high Al2O3 (14.30–15.31 wt%), Sr/Y (22.26–78.42) and (La/Yb)N (20.27–24.24), similar to those of Late Silurian–Early Devonian adakitic rocks (420–411 Ma) from the Xiemisitai Mountains. Furthermore, the rhyolite porphyry samples display high positive eHf(t) values and low Mg values as well as low concentrations of compatible elements (Cr, Co and Ni), suggesting that the rhyolite porphyry originated from partial melting of lower juvenile crust. The rhyolite porphyry displays spatio-temporal characteristics similar to those of the post-collision plutons (434–405 Ma) of the Xiemisitai Mountains. The rhyolite porphyry intruded the ophiolite in the melange, implying that the Hongguleleng–Balkybey Ocean closed prior to the Early Silurian. Our results, combined with other geological evidence, indicate that the northern West Junggar underwent ocean basin spreading, intra-oceanic subduction, arc–arc collision, the closure of the ocean and post-collisional extension during the Middle Cambrian–Early Devonian.

Moghadam, Hadi Shafaii - One of the best experts on this subject based on the ideXlab platform.

  • Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran
    'Geological Society of America', 2020
    Co-Authors: Moghadam, Hadi Shafaii, Stern R. J., Griffin W. L., Khedr M. Z., Kirchenbaur M., Ottley C. J., Whattam S. A., Kimura J.-i., Ghorbani G., Gain S.
    Abstract:

    How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harzburgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10−63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, Plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including Plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99−92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for ∼7 m.y. THO igneous rocks have variable εNd(t) of +5.7 to +8.2 and εHf(t) ranging from +14.9 to +21.5; zircons have εHf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation

  • Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran
    'Geological Society of America', 2020
    Co-Authors: Moghadam, Hadi Shafaii, Stern R. J., Griffin W. L., Khedr M. Z., Kirchenbaur M., Ottley C. J., Whattam S. A., Ghorbani G., Kimura J-, Gain S.
    Abstract:

    How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harz burgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10-63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, Plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including Plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99-92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for similar to 7 m.y. THO igneous rocks have variable epsilon Nd(t) of +5.7 to +8.2 and epsilon Hf(t) ranging from +14.9 to +21.5; zircons have epsilon Hf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation