The Experts below are selected from a list of 3399 Experts worldwide ranked by ideXlab platform
Lili Tong - One of the best experts on this subject based on the ideXlab platform.
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, M Santosh, Yongjun Li, Baokai Yang, Bing Zhang, Lili TongAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, Lili Tong, M Santosh, Baokai Yang, Bing ZhangAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
M Santosh - One of the best experts on this subject based on the ideXlab platform.
-
multi stage crustal melting from late permian back arc extension through middle triassic continental collision to late triassic post collisional extension in the east kunlun orogen
Lithos, 2020Co-Authors: M Santosh, Xu Zhao, Junhao Wei, Jan Marten Huizenga, Jiajie Chen, Dianzhong WangAbstract:Abstract The East Kunlun Orogen is an important part of the East Tethys region and has received significant attention with regards to the evolution of the Tethys Ocean. This contribution presents geochronological, whole-rock major and trace Element geochemical, and Sr-Nd-Hf isotopic data of magmatic rocks within the Kengdenongshe polymetallic deposit in the eastern part of the East Kunlun Orogen. Here, we report zircon U Pb ages of ca. 257 Ma and ca. 211 Ma for granite porphyry intrusions, and ca. 240 Ma for the rhyolitic tuff. These rocks are characterized by high SiO2, variable Al2O3 and K2O, low Na2O, MgO and CaO contents, and high A/CNK ratios, which is typical of S-type granitic rocks. They exhibit large-ion Lithophile Element enrichment, depletion of high field strength Elements, have low (La/Yb)N ratios, and negative Eu anomalies. They also display variable (87Sr/86Sr)i ratios (0.709981 to 0.720907), negative eNd (t) values (−8.7 to −5.5), and a wide (enriched) zircon eHf (t) range (−10.1 to −0.8). The geochemical and isotope data indicate magma derivation through dehydration melting of heterogeneous crustal sources including clay-poor meta-sedimentary rocks and amphibolite, which are both parts of the East Kunlun Orogen basement. These results provide evidence for the evolution of the Paleo-Tethys Ocean in the East Kunlun Orogen including Late Permian (266–255 Ma) back-arc extension, Late Permian to Middle Triassic (255–240 Ma) subduction, Middle Triassic (240–225 Ma) continental collision, and Late Triassic (
-
early neoproterozoic ca 913 895 ma arc magmatism along the central western korean peninsula implications for the amalgamation of rodinia supercontinent
Precambrian Research, 2019Co-Authors: Weon Seo Kee, M Santosh, Sung Won Kim, Sanghoon Kwon, Youn Joong JeongAbstract:Abstract Neoproterozoic arc magmatism in or around the Korean Peninsula provides important insights into the history of the Rodinia supercontinent. Here we report the petrology, zircon U-Pb ages, geochemistry, and Hf isotope data from the Early Neoproterozoic (ca. 913–895 Ma) igneous complexes (gabbro, diorite and granitic dyke) in the northern part of the Gogunsan Islands along the southwestern margin of the Hongseong–Imjingang Belt in the central–western Korean Peninsula. The gabbro and diorite- yielded zircon U–Pb ages of ca. 913 Ma, and ca. 909–899 Ma, respectively. The granitic dykes within this complex show ages of ca. 903–895 Ma. The gabbro-diorite, and granite belong to the subalkaline series, and are characterized by large ion Lithophile Element (LILE) enrichments, Nb–Ta troughs, and depletion in P and Ti anomalies similar to magmatism in the continental arc setting. The initial 176Hf/177Hf ratios and eHf(t) values obtained of zircon grains are in the ranges of 0.282132–0.282268 and –2.7 to 2.3 for gabbro, 0.282010–0.282363 and –6.4 to 6.0 for diorite, and 0.282071–0.282285 and –5.0 to 2.6 for granitic dykes, suggesting juvenile crust production with mixing of older crust materials. In combination with previously published U-Pb ages and geochemical features of Late Paleoproterozoic, Mesoproterozoic, and Early Neoproterozoic rift-related rocks in and around the central–western Korean Peninsula, the Early Neoproterozoic arc magmatism reported in this study provides clear evidence for a tectonic transition from the disruption of the Columbia supercontinent to the amalgamation and disruption of Rodinia supercontinent.
-
origin of sanukitoid and hornblendite enclaves in the dajitu pluton from the yinshan block north china craton product of neoarchaean ridge subduction
International Geology Review, 2014Co-Authors: M SantoshAbstract:A Neoarchaean sanukitoid pluton that was intruded into the base of the Guyang greenstone belt in the Yinshan Block of the North China Craton hosts a number of hornblendite enclaves. Geochemically, the pluton is characterized by high MgO, Mg#, Cr, Ni, large-ion Lithophile Element (LILE), and heavy rare earth Element (HREE) contents and low TiO2 and high-field strength Element (HFSE) contents, and has relatively low Sr/Y ratios and negative Eu anomalies. Whole-rock Sr–Nd isotopic analyses indicate that it has eNd(t) values of +1.4 to +2.0. These geochemical and isotopic characteristic suggest that the sanukitoid was formed under a low-pressure and high-temperature environment by slab melting and assimilation of hornblendite enclaves. The hornblendite enclaves show high MgO, Mg#, Cr, and Ni contents, high and variable K2O, LREE, and Th contents, enrichment in LILEs and LREEs, and depletion in HFSEs. They have high Y contents and relatively low Sr/Y values, strongly negative Eu anomalies, and whole-rock eNd(t...
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, M Santosh, Yongjun Li, Baokai Yang, Bing Zhang, Lili TongAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, Lili Tong, M Santosh, Baokai Yang, Bing ZhangAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
Gaoxue Yang - One of the best experts on this subject based on the ideXlab platform.
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, M Santosh, Yongjun Li, Baokai Yang, Bing Zhang, Lili TongAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
-
geochronology and geochemistry of basalts from the karamay ophiolitic melange in west junggar nw china implications for devonian carboniferous intra oceanic accretionary tectonics of the southern altaids
Geological Society of America Bulletin, 2013Co-Authors: Gaoxue Yang, Lili Tong, M Santosh, Baokai Yang, Bing ZhangAbstract:New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic melange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the melange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic melange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km 2 . The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na 2 O + K 2 O (3.7–8.5 wt%) and TiO 2 (1.5–3.1 wt%); large ion Lithophile Element and light rare earth Element enrichment and heavy rare earth Element depletion; very weak or no Eu anomalies (Eu/Eu ∗ = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic melange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block.
Xinyu Wang - One of the best experts on this subject based on the ideXlab platform.
-
carboniferous bimodal volcanic rocks in the eastern tianshan nw china evidence for arc rifting
Gondwana Research, 2017Co-Authors: Yunying Zhang, Long Du, Zongying Huang, Xiaoping Long, Chao Yuan, Xinyu WangAbstract:Abstract Detailed geochronological, geochemical, and Sr–Nd isotopic data are presented for late Paleozoic volcanic rocks in the Dashitou area from the Eastern Tianshan, NW China, aiming to constrain their petrogenesis and tectonic implications. The Dashitou volcanic rocks show a bimodal distribution in composition, with dominant rhyolite and subordinate basalt. LA–ICPMS zircon U–Pb age indicates that the volcanic rocks were erupted at 330 ± 3 Ma. The basaltic rocks are medium-K calc-alkaline, enriched in light rare earth Element (LREE) and large ion Lithophile Element (LILE; Ba and U), and depleted in high field strength Element (HFSE; Nb, Ta, and Ti). These features, together with their depleted isotopic signature (initial 87Sr/86Sr = 0.7035 to 0.7039, eNd(t) = 6.8 to 7.1), suggest that they were likely derived from a depleted mantle source metasomatized by subduction-related fluids. The rhyolitic rocks are high-K calc-alkaline and exhibit characteristics of A2-type granite, with typical enrichment in alkalis, Zr, and Nb and depletion in Sr, P, and Ti. They are characterized by positive eNd(t) values (6.2–6.5) with young Nd model ages (0.57–0.58 Ga). Results of MELTS modeling imply that they were unlikely produced by fractional crystallization of coeval basaltic rocks. Instead, they were probably generated by partial melting of juvenile basaltic crust as a result of magma underplating. The geochemical and Sr–Nd isotopic characteristics, coupled with regional geology, indicate that the formation of the Dashitou bimodal volcanic rocks involves an extensional regime associated with a subduction-related environment. The rifting of the Dananhu–Harlik arc in response to the retreat of the subducting Northern Tianshan oceanic lithosphere may account for the Dashitou bimodal volcanic rocks.
-
carboniferous bimodal volcanic rocks in the eastern tianshan nw china evidence for arc rifting
Gondwana Research, 2017Co-Authors: Yunying Zhang, Long Du, Zongying Huang, Xiaoping Long, Chao Yuan, Xinyu WangAbstract:Abstract Detailed geochronological, geochemical, and Sr–Nd isotopic data are presented for late Paleozoic volcanic rocks in the Dashitou area from the Eastern Tianshan, NW China, aiming to constrain their petrogenesis and tectonic implications. The Dashitou volcanic rocks show a bimodal distribution in composition, with dominant rhyolite and subordinate basalt. LA–ICPMS zircon U–Pb age indicates that the volcanic rocks were erupted at 330 ± 3 Ma. The basaltic rocks are medium-K calc-alkaline, enriched in light rare earth Element (LREE) and large ion Lithophile Element (LILE; Ba and U), and depleted in high field strength Element (HFSE; Nb, Ta, and Ti). These features, together with their depleted isotopic signature (initial 87Sr/86Sr = 0.7035 to 0.7039, eNd(t) = 6.8 to 7.1), suggest that they were likely derived from a depleted mantle source metasomatized by subduction-related fluids. The rhyolitic rocks are high-K calc-alkaline and exhibit characteristics of A2-type granite, with typical enrichment in alkalis, Zr, and Nb and depletion in Sr, P, and Ti. They are characterized by positive eNd(t) values (6.2–6.5) with young Nd model ages (0.57–0.58 Ga). Results of MELTS modeling imply that they were unlikely produced by fractional crystallization of coeval basaltic rocks. Instead, they were probably generated by partial melting of juvenile basaltic crust as a result of magma underplating. The geochemical and Sr–Nd isotopic characteristics, coupled with regional geology, indicate that the formation of the Dashitou bimodal volcanic rocks involves an extensional regime associated with a subduction-related environment. The rifting of the Dananhu–Harlik arc in response to the retreat of the subducting Northern Tianshan oceanic lithosphere may account for the Dashitou bimodal volcanic rocks.
Chao Yuan - One of the best experts on this subject based on the ideXlab platform.
-
carboniferous bimodal volcanic rocks in the eastern tianshan nw china evidence for arc rifting
Gondwana Research, 2017Co-Authors: Yunying Zhang, Long Du, Zongying Huang, Xiaoping Long, Chao Yuan, Xinyu WangAbstract:Abstract Detailed geochronological, geochemical, and Sr–Nd isotopic data are presented for late Paleozoic volcanic rocks in the Dashitou area from the Eastern Tianshan, NW China, aiming to constrain their petrogenesis and tectonic implications. The Dashitou volcanic rocks show a bimodal distribution in composition, with dominant rhyolite and subordinate basalt. LA–ICPMS zircon U–Pb age indicates that the volcanic rocks were erupted at 330 ± 3 Ma. The basaltic rocks are medium-K calc-alkaline, enriched in light rare earth Element (LREE) and large ion Lithophile Element (LILE; Ba and U), and depleted in high field strength Element (HFSE; Nb, Ta, and Ti). These features, together with their depleted isotopic signature (initial 87Sr/86Sr = 0.7035 to 0.7039, eNd(t) = 6.8 to 7.1), suggest that they were likely derived from a depleted mantle source metasomatized by subduction-related fluids. The rhyolitic rocks are high-K calc-alkaline and exhibit characteristics of A2-type granite, with typical enrichment in alkalis, Zr, and Nb and depletion in Sr, P, and Ti. They are characterized by positive eNd(t) values (6.2–6.5) with young Nd model ages (0.57–0.58 Ga). Results of MELTS modeling imply that they were unlikely produced by fractional crystallization of coeval basaltic rocks. Instead, they were probably generated by partial melting of juvenile basaltic crust as a result of magma underplating. The geochemical and Sr–Nd isotopic characteristics, coupled with regional geology, indicate that the formation of the Dashitou bimodal volcanic rocks involves an extensional regime associated with a subduction-related environment. The rifting of the Dananhu–Harlik arc in response to the retreat of the subducting Northern Tianshan oceanic lithosphere may account for the Dashitou bimodal volcanic rocks.
-
carboniferous bimodal volcanic rocks in the eastern tianshan nw china evidence for arc rifting
Gondwana Research, 2017Co-Authors: Yunying Zhang, Long Du, Zongying Huang, Xiaoping Long, Chao Yuan, Xinyu WangAbstract:Abstract Detailed geochronological, geochemical, and Sr–Nd isotopic data are presented for late Paleozoic volcanic rocks in the Dashitou area from the Eastern Tianshan, NW China, aiming to constrain their petrogenesis and tectonic implications. The Dashitou volcanic rocks show a bimodal distribution in composition, with dominant rhyolite and subordinate basalt. LA–ICPMS zircon U–Pb age indicates that the volcanic rocks were erupted at 330 ± 3 Ma. The basaltic rocks are medium-K calc-alkaline, enriched in light rare earth Element (LREE) and large ion Lithophile Element (LILE; Ba and U), and depleted in high field strength Element (HFSE; Nb, Ta, and Ti). These features, together with their depleted isotopic signature (initial 87Sr/86Sr = 0.7035 to 0.7039, eNd(t) = 6.8 to 7.1), suggest that they were likely derived from a depleted mantle source metasomatized by subduction-related fluids. The rhyolitic rocks are high-K calc-alkaline and exhibit characteristics of A2-type granite, with typical enrichment in alkalis, Zr, and Nb and depletion in Sr, P, and Ti. They are characterized by positive eNd(t) values (6.2–6.5) with young Nd model ages (0.57–0.58 Ga). Results of MELTS modeling imply that they were unlikely produced by fractional crystallization of coeval basaltic rocks. Instead, they were probably generated by partial melting of juvenile basaltic crust as a result of magma underplating. The geochemical and Sr–Nd isotopic characteristics, coupled with regional geology, indicate that the formation of the Dashitou bimodal volcanic rocks involves an extensional regime associated with a subduction-related environment. The rifting of the Dananhu–Harlik arc in response to the retreat of the subducting Northern Tianshan oceanic lithosphere may account for the Dashitou bimodal volcanic rocks.
-
triassic granitoids in the eastern songpan ganzi fold belt sw china magmatic response to geodynamics of the deep lithosphere
Earth and Planetary Science Letters, 2010Co-Authors: Chao Yuan, Xiaoping Long, Simon A Wilde, Meifu Zhou, Min Sun, Yongjiu Zhao, Danping YanAbstract:The Songpan Ganzi Fold Belt (SGFB), SW China, was developed from a passive continental margin into an orogenic belt with the consumption of the Paleo-Tethys. During the evolution of the SGFB, numerous Late Triassic granitic plutons formed and exhibited a progressive development from adakite/I-type granite, high Ba–Sr granite, A-type granite and monzonite. Representative Late Triassic plutons were studied to unravel the bewildering evolution of the eastern SGFB. The Menggu Pluton (224 ± 3 Ma) consists of granites with high alkali (K2O+Na2O = 7.85–10.4 wt.%) and adakitic characteristics (Sr/Y = 19–38). The eNdT values (− 2.77 to − 5.03), initial 87Sr/86Sr ratios (0.7050–0.7063) and low Nb/Ta ratios (8–10) are indicative of an origin by partial melting of amphibolitic lower crust. Rocks from the Niuxingou Pluton (215 ± 3 Ma) are richer in K than Na (K2O/Na2O = 1.1–1.5) and contain high Sr (1006–1662 ppm) and Ba (1277–2009 ppm), typical of shoshonite and high Ba–Sr granite. They have less enriched eNdT values (+ 0.08 to − 2.04) and less radiogenic 87Sr/86Sri ratios (0.7047–0.7048), and formed from a mixed melt derived from upwelling asthenosphere and the overlying metasomatised lithospheric mantle. The Taiyanghe Pluton (205 ± 3 Ma) consists of monzonites, with high Al2O3 (> 20 wt.%), but low MgO (0.94–1.39 wt.%). The rocks are richer in Na than K (K2O/Na2O < 0.7), contain high large ion Lithophile Element (LILE) (681–834 ppm Sr and 2142–9453 ppm Ba) and display strongly fractionated REE patterns ((La/Yb)N = 35–63). These features, together with their enriched Nd–Sr isotopic compositions (eNdT = − 4.78 to − 6.50; 87Sr/86Sri = 0.7074–0.7090), suggest that the monzonite probably formed from low degrees of partial melting of metasomatised lithospheric mantle. Although a continuous compressional regime during the Mid- and Late Triassic has been invoked for the SGFB, the generation of crustally derived adakitic and shoshonitic plutons reflect thickening in response to an arc-continental collision accompanied by fracturing of the lithosphere and an extensional regime in the deep lithosphere in the Late Triassic. The 205 Ma Taiyanghe Pluton was emplaced simultaneously with a rapid uplift of the lithosphere, when surface deposits changed from deep-water turbidite to tidal flat sediments. It was therefore generated during decompression, probably related to the rapid removal of the overthickened lithospheric mantle. The Triassic magmatism in the eastern SGFB is therefore important for probing geodynamic processes in the deep lithosphere.