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M Santosh - One of the best experts on this subject based on the ideXlab platform.
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Geochemical systematics of the Mauranipur-Babina greenstone belt, Bundelkhand Craton, Central India: Insights on Neoarchean Mantle Plume-arc accretion and crustal evolution
Elsevier, 2018Co-Authors: S.p. Singh, M Santosh, C Manikyamba, K.s.v. Subramanyam, Rajanikanta M. Singh, Chandan B. KumarAbstract:The Neoarchean Bundelkhand greenstone sequences at Mauranipur and Babina areas within the Bundelkhand Gneissic Complex preserve a variety of magmatic rocks such as komatiitic basalts, basalts, felsic volcanic rocks and high-Mg andesites belonging to the Baragaon, Raspahari and Koti Formations. The intrusive and extrusive komatiitic basalts are characterized by low SiO2 (39–53 wt.%), high MgO (18–25 wt.%), moderately high Fe2O3 (7.1–11.6 wt.%), Al2O3 (4.5–12.0 wt.%), and TiO2 (0.4–1.23 wt.%) with super to subchondritic (Gd/Yb)N ratios indicating garnet control on the melts. The intrusive komatiitic suite of Ti-enriched and Al-depleted type possesses predominant negative Eu and positive Nb, Ti and Y anomalies. The chemical composition of basalts classifies them into three types with varying SiO2, TiO2, MgO, Fe2O3, Al2O3 and CaO. At similar SiO2 content of type I and III basalts, the type II basalts show slightly high Al2O3 and Fe2O3 contents. Significant negative anomalies of Nb, Zr, Hf and Ti, slightly enriched LREE with relatively flat HREE and low ∑REE contents are observed in type I and II basalts. Type III basalts show high Zr/Nb ratios (9.8–10.4), TiO2 (1.97–2.04 wt.%), but possess strikingly flat Zr, Hf, Y and Yb and are uncontaminated. Andesites from Agar and Koti have high SiO2 (55–64 wt.%), moderate TiO2 (0.4–0.7 wt.%), slightly low Al2O3 (7–11.9 wt.%), medium to high MgO (3–8 wt.%) and CaO contents (10–17 wt.%). Anomalously high Cr, Co and Ni contents are observed in the Koti rhyolites. Tholeiitic to calc alkaline affinity of mafic-felsic volcanic rocks and basalt–andesite–dacite–rhyolite differentiation indicate a mature arc and thickened crust during the advanced stage of the evolution of Neoarchean Bundelkhand greenstone belt in a convergent tectonic setting where the melts were derived from partial melting of thick basaltic crust metamorphosed to amphibolite-eclogite facies. The trace element systematics suggest the presence of arc-back arc association with varying magnitudes of crust-Mantle interaction. La/Sm, La/Ta, Nb/Th, high MgO contents (>20 wt.%), CaO/Al2O3 and (Gd/Yb)N > 1 along with the positive Nb anomalies of the komatiite basalts reflect a Mantle Plume source for their origin contaminated by subduction-metasomatized Mantle lithosphere. The overall geochemical signatures of the ultramafic-mafic and felsic volcanic rocks endorse the Neoarchean Plume-arc accretion tectonics in the Bundelkhand greenstone belt. Keywords: Bundelkhand craton, Greenstone belts, Mantle dynamics, Plume-arc accretion, Neoarchean crustal evolutio
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geochemical systematics of the mauranipur babina greenstone belt bundelkhand craton central india insights on neoarchean Mantle Plume arc accretion and crustal evolution
Geoscience frontiers, 2017Co-Authors: S.p. Singh, M Santosh, C Manikyamba, K.s.v. Subramanyam, Rajanikanta M. Singh, Chandan B. KumarAbstract:Abstract The Neoarchean Bundelkhand greenstone sequences at Mauranipur and Babina areas within the Bundelkhand Gneissic Complex preserve a variety of magmatic rocks such as komatiitic basalts, basalts, felsic volcanic rocks and high-Mg andesites belonging to the Baragaon, Raspahari and Koti Formations. The intrusive and extrusive komatiitic basalts are characterized by low SiO 2 (39–53 wt.%), high MgO (18–25 wt.%), moderately high Fe 2 O 3 (7.1–11.6 wt.%), Al 2 O 3 (4.5–12.0 wt.%), and TiO 2 (0.4–1.23 wt.%) with super to subchondritic (Gd/Yb) N ratios indicating garnet control on the melts. The intrusive komatiitic suite of Ti-enriched and Al-depleted type possesses predominant negative Eu and positive Nb, Ti and Y anomalies. The chemical composition of basalts classifies them into three types with varying SiO 2 , TiO 2 , MgO, Fe 2 O 3 , Al 2 O 3 and CaO. At similar SiO 2 content of type I and III basalts, the type II basalts show slightly high Al 2 O 3 and Fe 2 O 3 contents. Significant negative anomalies of Nb, Zr, Hf and Ti, slightly enriched LREE with relatively flat HREE and low ∑REE contents are observed in type I and II basalts. Type III basalts show high Zr/Nb ratios (9.8–10.4), TiO 2 (1.97–2.04 wt.%), but possess strikingly flat Zr, Hf, Y and Yb and are uncontaminated. Andesites from Agar and Koti have high SiO 2 (55–64 wt.%), moderate TiO 2 (0.4–0.7 wt.%), slightly low Al 2 O 3 (7–11.9 wt.%), medium to high MgO (3–8 wt.%) and CaO contents (10–17 wt.%). Anomalously high Cr, Co and Ni contents are observed in the Koti rhyolites. Tholeiitic to calc alkaline affinity of mafic-felsic volcanic rocks and basalt–andesite–dacite–rhyolite differentiation indicate a mature arc and thickened crust during the advanced stage of the evolution of Neoarchean Bundelkhand greenstone belt in a convergent tectonic setting where the melts were derived from partial melting of thick basaltic crust metamorphosed to amphibolite-eclogite facies. The trace element systematics suggest the presence of arc-back arc association with varying magnitudes of crust-Mantle interaction. La/Sm, La/Ta, Nb/Th, high MgO contents (>20 wt.%), CaO/Al 2 O 3 and (Gd/Yb) N > 1 along with the positive Nb anomalies of the komatiite basalts reflect a Mantle Plume source for their origin contaminated by subduction-metasomatized Mantle lithosphere. The overall geochemical signatures of the ultramafic-mafic and felsic volcanic rocks endorse the Neoarchean Plume-arc accretion tectonics in the Bundelkhand greenstone belt.
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seismic tomographic evidence for upwelling Mantle Plume in ne china
Physics of the Earth and Planetary Interiors, 2016Co-Authors: M SantoshAbstract:Abstract In this study, we collected teleseismic data recorded by permanent and mobile seismic stations and carried out a teleseismic P-wave tomographic study. The results reveal low velocity perturbation regions at the central part of NE China and specifically in the Songliao basin at different depths, which correspond to the location of a proposed upwelling Mantle Plume identified by receiver function in a recent study. Receiver function data show a predominantly mafic/ultra-mafic lower crust in the Songliao basin, in contrast to the predominantly felsic lower crust in the other regions. The vestige of upwelling Mantle Plume is well defined at the Mantle transition region. Based on the above results, we suggest that the volcanism in NE China and the Songliao basin formation might be related to Mesozoic Mantle Plume beneath NE China. We also evaluate alternate models on lower crustal delamination contributing to the volcanism in NE China following collision and amalgamation between the Siberia craton and the North China–Mongolian block during late Jurassic and early Cretaceous.
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perovskite and baddeleyite from kimberlitic intrusions in the tarim large igneous province signal the onset of an end carboniferous Mantle Plume
Earth and Planetary Science Letters, 2013Co-Authors: Dongyang Zhang, M Santosh, Zhaochong Zhang, Zhiguo Cheng, Huang He, Jianli KangAbstract:Several tens of kimberlitic pipes and dykes are exposed in the Wajilitag area in the western Tarim large igneous province. Here we report for the first time secondary ion mass spectrometric U–Pb age data on perovskite and baddeleyite grains in a kimberlitic pipe and a kimberlitic dyke from the Tarim Craton. The perovskite yielded a well-defined intercept age of 299.87 4.3 Ma, which is consistent with its corresponding concordia and 206 Pb/ 238 U ages, corrected for the common Pb contribution, of about 300 Ma. The baddeleyite separated from two kimberlitic samples from a dyke display identical concordia U–Pb ages of 300.87 4.7 Ma and 300.57 4.4 Ma. Our age data show that the kimberlitic intrusions were emplaced at ca. 300 Ma, rather than in the late Permian as previously regarded. These new ages are slightly older than the eruption ages of Tarim flood basalts (291–273 Ma), offering a critical regional time marker for the onset of Permo-Carboniferous magmatism in the Tarim Craton. Detailed petrographic observations did not reveal any ultrahigh pressure mineral assemblage in the Wajilitag kimberlitic intrusions. Phlogopites from these intrusions show eNd(t) values of þ3.7 to þ 4.2. The baddeleyites which are texturally primary and therefore inferred to have crystallized directly from the kimberlitic magma, yield a range of eHf(t) from þ 4.8 to þ8.7. These results combined with previously reported geochemical data, suggest that the Wajilitag kimberlitic intrusions were most likely derived from a moderately refractory and depleted subcontinental lithosphere Mantle, metasomatized by subduction components associated with an early-middle Paleozoic convergent regime. The kimberlitic magma was generated by small-degree partial melting of the lithospheric Mantle in response to the impingement of the Tarim Mantle Plume. Thus, our new geochronological data suggest the arrival of the Mantle Plume beneath the Tarim lithosphere at least 10 million years before the onset of Tarim flood basalt volcanism. The end-Carboniferous Wajilitag kimberlitic intrusions, the oldest known phase associated with Carboniferous magmatism in the Tarim Craton, signals the initial magmatic pulse triggered by Mantle Plume impingement.
Yigang Xu - One of the best experts on this subject based on the ideXlab platform.
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crustal melting above a Mantle Plume insights from the permian tarim large igneous province nw china
Lithos, 2019Co-Authors: Yigang Xu, Yuting Zhong, Roland Mundil, Teal R Riley, Le ZhangAbstract:Abstract Low Nb Ta rhyolites from the Permian Tarim Large Igneous Province (LIP) represent the melting products of continental crust above a Mantle Plume. Zircon U Pb dating reveals that the Kuchehe and Dawanqi rhyolites were erupted at 292.6 ± 0.5 Ma and 274 ± 2 Ma respectively. Both rhyolite groups are characterized by pronounced negative Nb Ta anomalies, crust-like trace element ratios and negative eNd-Hf(t) values, consistent with a crustal origin. Newly acquired data, combined with available data in the literature, clearly show that there is an increasing trend of zircon saturation temperature (TZr) from 794 to 827 °C to 886–936 °C for the early to middle stage (293–287 Ma), followed by a decreasing TZr of 803–908 °C for the late stage (287–274 Ma) of the Tarim magmatism. The temporal changes in TZr for the Tarim rhyolites are interpreted to reflect the crustal melting behavior above a Mantle Plume, such that fusible materials in the crust melt at an earlier stage and refractory materials melt at a later stage. The gradual decrease in TZr, towards the final stage of the Tarim rhyolitic magmatism, reflects the gradual ‘decay’ of thermal input from Mantle Plume to the lithosphere in the region. This thermal model is also applicable to describe the crustal melting behavior in the Chon Aike silicic LIP of Patagonia and the Snake River Plateau-Yellowstone Plateau volcanic provinces.
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anticlockwise p t evolution at 280 ma recorded from ultrahigh temperature metapelitic granulite in the chinese altai orogenic belt a possible link with the tarim Mantle Plume
Journal of Asian Earth Sciences, 2014Co-Authors: Laixi Tong, Yigang Xu, Peter A Cawood, Xin Zhou, Yibing ChenAbstract:Abstract An ultrahigh-temperature (UHT) metapelitic granulite assemblage consisting of garnet(g)–spinel(sp)–orthopyroxene(opx)–sillimanite(sil)–cordierite(cd)–ilmenite(ilm)–biotite(bi)–plagioclase(pl)–quartz(q) occurs within migmatitic paragneiss near Kalasu in the Chinese Altai, NW China. Textural relations, mineral compositions and P-T estimates, indicate three stages of mineral assemblages: (1) pre-peak prograde stage (M1) consisting of a sp–sil-bearing or sp–opx-bearing inclusion assemblage, with low-Al2O3 contents (4–5 wt.%) in orthopyroxene and P-T conditions of ∼7 kbar and ∼890 °C, (2) peak UHT stage (M2) comprising a g–opx–cd-bearing coarse-grained assemblage, with high-Al2O3 contents (8–9 wt.%) in orthopyroxene and peak conditions of ∼8 kbar and ∼970 °C, and (3) post-peak HT stage (M3) containing an oriented opx–bi–sil-bearing assemblage in matrix, with moderate amounts of Al2O3 (6–7 wt.%) in orthopyroxene and P-T conditions of 8–9 kbar and ∼870 °C. The three discrete stages define an anticlockwise P-T path involving initial prograde heating and post-peak near isobaric cooling. Such a near isobaric cooling anticlockwise P-T path suggests that UHT metamorphism likely occurred in an overall extensional tectonic setting with associated underplating of Mantle-derived mafic magma. A SHRIMP zircon U–Pb age of 278 ± 2 Ma obtained from the metapelitic granulite indicates UHT metamorphism in the Altai orogen occurred during the Permian, coeval with spacially associated Mantle-derived mafic intrusions (∼280 Ma) and the Tarim Mantle Plume (∼275 Ma). Thus, the Permian UHT metamorphism of the Chinese Altai is likely associated with underplating and heating of Mantle-derived mafic magma as a result of the Tarim Mantle Plume.
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origin of two types of rhyolites in the tarim large igneous province consequences of incubation and melting of a Mantle Plume
Lithos, 2014Co-Authors: Yigang Xu, Yuting Zhong, Roland Mundil, Xianhua Li, Wei Tian, Yueheng Yang, Shimai ShangguanAbstract:Abstract The Early Permian Tarim Large Igneous Province (LIP) in northwestern China contains a large area of silicic volcanics (~ 48,000 km 2 ) which are spatially and temporally associated with mafic–ultramafic rocks. In order to understand the behavior of crust above a Mantle Plume, selected rhyolitic samples are investigated in terms of U–Pb zircon dating, geochemical and isotopic analyses. The Tarim rhyolites have high A/CNK ratios (= molar Al 2 O 3 /CaO + Na 2 O + K 2 O), Fe # , Ga/Al ratios, concentrations of high field strength elements (HFSEs) such as Zr and Nb, and rare earth elements (REEs), along with high zircon saturation temperatures (872–940 °C), typical of aluminous A-type granitoids. Two contrasting rock types have been recognized. The low Nb–Ta type rhyolites are mainly associated with the first phase of the Tarim flood basalt magmatism at ~ 290 Ma. They are characterized by negative Nb–Ta anomalies, low e Nd (t) and e Hf (t) values, and high 87 Sr/ 86 Sr(t) and δ 18 O zircon values, consistent with a derivation from continental crustal source. The high Nb–Ta type rhyolites and their plutonic equivalents are associated with the second episode of Tarim magmatism (283–272 Ma). They are characterized by small negative to positive Nb–Ta anomalies, oceanic island basalt (OIB)-like trace element ratios, low 87 Sr/ 86 Sr(t) and high e Nd (t) and e Hf (t) values. These high Nb–Ta rhyolites are best interpreted as hybrid products of crystal fractionation of mafic magmas, coupled with crustal assimilation. The temporal and compositional evolution of the Tarim rhyolites reflects various extents of thermal and mass exchange between Mantle-derived basaltic magma and crustal material above a Mantle Plume. When the Plume head rises to the base of the Tarim craton, it first melts enriched components in the lithospheric Mantle (~ 290 Ma), part of which may have ponded near the crust–Mantle boundary and induced crustal anatexis leading to the formation of the low Nb–Ta type rhyolites. At ~ 280 Ma, large magma chambers and plumbing systems were formed due to increasing magma supply rate during decompression melting of the Mantle Plume. This led to the formation of a mafic–ultramafic and felsic association of which the high Nb–Ta type rhyolites are a part.
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identification of an ancient Mantle reservoir and young recycled materials in the source region of a young Mantle Plume implications for potential linkages between Plume and plate tectonics
Earth and Planetary Science Letters, 2013Co-Authors: Xuance Wang, Zhengxiang Li, Yigang Xu, Xianhua Li, Jie Li, Xianghui LiAbstract:Whether or not Mantle Plumes and plate subduction are genetically linked is a fundamental geoscience question that impinges on our understanding of how the Earth works. Late Cenozoic basalts in Southeast Asia are globally unique in relation to this question because they occur above a seismically detected thermal Plume adjacent to deep subducted slabs. In this study, we present new Pb, Sr, Nd, and Os isotope data for the Hainan flood basalts. Together with a compilation of published results, our work shows that less contaminated basaltic samples from the synchronous basaltic eruptions in Hainan–Leizhou peninsula, the Indochina peninsula and the South China Sea seamounts share the same isotopic and geochemical characteristics. They have FOZO-like Sr, Nd, and Pb isotopic compositions (the dominant lower Mantle component). These basalts have primitive Pb isotopic compositions that lie on, or very close to, 4.5- to 4.4-Ga geochrons on 207Pb/204Pb versus 206Pb/204Pb diagram, suggesting a Mantle source developed early in Earthʼs history (4.5–4.4 Ga). Furthermore, our detailed geochemical and Sr, Nd, Pb and Os isotopic analyses suggest the presence of 0.5–0.2 Ga recycled components in the late Cenozoic Hainan Plume basalts. This implies a Mantle circulation rate of >1 cm/yr, which is similar to that of previous estimates for the Hawaiian Mantle Plume. The identification of the ancient Mantle reservoir and young recycled materials in the source region of these synchronous basalts is consistent with the seismically detected lower Mantle-rooted Hainan Plume that is adjacent to deep subducted slab-like seismic structures just above the core–Mantle boundary. We speculate that the continued deep subduction and the presence of a dense segregated basaltic layer may have triggered the Plume to rise from the thermal–chemical pile. This work therefore suggests a dynamic linkage between deep subduction and Mantle Plume generation.
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a permian large igneous province in tarim and central asian orogenic belt nw china results of a ca 275 ma Mantle Plume
Geological Society of America Bulletin, 2010Co-Authors: Chuanlin Zhang, Zhengxiang Li, Yigang Xu, Xianhua Li, Gang Zhou, Haimin YeAbstract:New sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, geochemical data, and a synthesis of existing stratigraphic, geochronologic, and geochemical results from the Tarim block and the Central Asian orogenic belt in northwestern China suggest the presence of a Permian (ca. 275 Ma) large igneous province (the Bachu large igneous province). The large igneous province consists predominantly of coeval mafic rocks (basalts and mafic-ultramafic intrusions) having an aerial coverage of more than 600,000 km 2 , and its formation was accompanied by voluminous emplacement of A-type granites. This large igneous province, interpreted to be of Mantle Plume origin, is ∼15 m.y. older than the ca. 260 Ma Emeishan large igneous province in southwestern China and ∼25 m.y. older than the 251 Ma Siberian Trap in Russia. Such a sudden flair up of Plume activity in the Permian may represent the early stage of the Pangean superPlume event. The Permian Plumes likely played a role in late Paleozoic rapid continental crustal growth in the Central Asian orogenic belt. In addition, there appear to be two types of Mantle geochemical provinces (domains) in the region, a long-term enriched Tarim province and a subduction-metasomatized and depleted Central Asian orogenic belt province.
Xianhua Li - One of the best experts on this subject based on the ideXlab platform.
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origin of two types of rhyolites in the tarim large igneous province consequences of incubation and melting of a Mantle Plume
Lithos, 2014Co-Authors: Yigang Xu, Yuting Zhong, Roland Mundil, Xianhua Li, Wei Tian, Yueheng Yang, Shimai ShangguanAbstract:Abstract The Early Permian Tarim Large Igneous Province (LIP) in northwestern China contains a large area of silicic volcanics (~ 48,000 km 2 ) which are spatially and temporally associated with mafic–ultramafic rocks. In order to understand the behavior of crust above a Mantle Plume, selected rhyolitic samples are investigated in terms of U–Pb zircon dating, geochemical and isotopic analyses. The Tarim rhyolites have high A/CNK ratios (= molar Al 2 O 3 /CaO + Na 2 O + K 2 O), Fe # , Ga/Al ratios, concentrations of high field strength elements (HFSEs) such as Zr and Nb, and rare earth elements (REEs), along with high zircon saturation temperatures (872–940 °C), typical of aluminous A-type granitoids. Two contrasting rock types have been recognized. The low Nb–Ta type rhyolites are mainly associated with the first phase of the Tarim flood basalt magmatism at ~ 290 Ma. They are characterized by negative Nb–Ta anomalies, low e Nd (t) and e Hf (t) values, and high 87 Sr/ 86 Sr(t) and δ 18 O zircon values, consistent with a derivation from continental crustal source. The high Nb–Ta type rhyolites and their plutonic equivalents are associated with the second episode of Tarim magmatism (283–272 Ma). They are characterized by small negative to positive Nb–Ta anomalies, oceanic island basalt (OIB)-like trace element ratios, low 87 Sr/ 86 Sr(t) and high e Nd (t) and e Hf (t) values. These high Nb–Ta rhyolites are best interpreted as hybrid products of crystal fractionation of mafic magmas, coupled with crustal assimilation. The temporal and compositional evolution of the Tarim rhyolites reflects various extents of thermal and mass exchange between Mantle-derived basaltic magma and crustal material above a Mantle Plume. When the Plume head rises to the base of the Tarim craton, it first melts enriched components in the lithospheric Mantle (~ 290 Ma), part of which may have ponded near the crust–Mantle boundary and induced crustal anatexis leading to the formation of the low Nb–Ta type rhyolites. At ~ 280 Ma, large magma chambers and plumbing systems were formed due to increasing magma supply rate during decompression melting of the Mantle Plume. This led to the formation of a mafic–ultramafic and felsic association of which the high Nb–Ta type rhyolites are a part.
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identification of an ancient Mantle reservoir and young recycled materials in the source region of a young Mantle Plume implications for potential linkages between Plume and plate tectonics
Earth and Planetary Science Letters, 2013Co-Authors: Xuance Wang, Zhengxiang Li, Yigang Xu, Xianhua Li, Jie Li, Xianghui LiAbstract:Whether or not Mantle Plumes and plate subduction are genetically linked is a fundamental geoscience question that impinges on our understanding of how the Earth works. Late Cenozoic basalts in Southeast Asia are globally unique in relation to this question because they occur above a seismically detected thermal Plume adjacent to deep subducted slabs. In this study, we present new Pb, Sr, Nd, and Os isotope data for the Hainan flood basalts. Together with a compilation of published results, our work shows that less contaminated basaltic samples from the synchronous basaltic eruptions in Hainan–Leizhou peninsula, the Indochina peninsula and the South China Sea seamounts share the same isotopic and geochemical characteristics. They have FOZO-like Sr, Nd, and Pb isotopic compositions (the dominant lower Mantle component). These basalts have primitive Pb isotopic compositions that lie on, or very close to, 4.5- to 4.4-Ga geochrons on 207Pb/204Pb versus 206Pb/204Pb diagram, suggesting a Mantle source developed early in Earthʼs history (4.5–4.4 Ga). Furthermore, our detailed geochemical and Sr, Nd, Pb and Os isotopic analyses suggest the presence of 0.5–0.2 Ga recycled components in the late Cenozoic Hainan Plume basalts. This implies a Mantle circulation rate of >1 cm/yr, which is similar to that of previous estimates for the Hawaiian Mantle Plume. The identification of the ancient Mantle reservoir and young recycled materials in the source region of these synchronous basalts is consistent with the seismically detected lower Mantle-rooted Hainan Plume that is adjacent to deep subducted slab-like seismic structures just above the core–Mantle boundary. We speculate that the continued deep subduction and the presence of a dense segregated basaltic layer may have triggered the Plume to rise from the thermal–chemical pile. This work therefore suggests a dynamic linkage between deep subduction and Mantle Plume generation.
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u pb ages and hf o isotopes of zircons from late paleozoic mafic ultramafic units in the southern central asian orogenic belt tectonic implications and evidence for an early permian Mantle Plume
Gondwana Research, 2011Co-Authors: Benxun Su, Xianhua Li, Yueheng Yang, Patrick Asamoah Sakyi, Dongmei Tang, Qinghua Xiao, Sanjeewa P K MalaviarachchiAbstract:Abstract U–Pb age and Hf–O isotope data of zircons from the mafic–ultramafic complexes and their related rhyolites and granites in the Eastern Tianshan and Beishan regions were obtained by SIMS and LA-ICPMS. The Hf–O isotopic composition and Hf model age of the zircons are closely related to their tectonic setting and formation age. The zircons from the mafic–ultramafic complexes in the Bogeda–Haerlike and Jueluotage belts have higher eHf(t) (+ 8– + 17) and lower δ18O (+ 4‰– + 6‰), whereas most of the zircons in the gabbros, granites and rhyolite from the Middle Tianshan Massif and Beishan Rift display lower eHf(t) (0– + 8) and higher δ18O (+ 5‰– + 8‰). The positive eHf(t) and relatively lower δ18O values suggest that these mafic–ultramafic complexes were derived from depleted Mantle which was subjected to subduction-related modification processes. The Hf isotopic composition of zircons in the granites has revealed that the growth of juvenile crust was also very significant in the southern margin of the Central Asian Orogenic Belt during the Paleozoic. The Hf model ages of the analyzed zircons, together with the regional geology suggest that the Beishan area had a northward subduction, possibly from ca. 900 Ma to ca. 400 Ma, whereas the Eastern Tianshan had a south-directed subduction most likely from ca. 600 Ma to ca. 310 Ma. Additionally, zircons with ca. 280 Ma U–Pb ages display wider and more scattered eHf(t) and δ18O variations than the relatively older and younger ones, which further support the Early Permian Mantle Plume model.
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a permian large igneous province in tarim and central asian orogenic belt nw china results of a ca 275 ma Mantle Plume
Geological Society of America Bulletin, 2010Co-Authors: Chuanlin Zhang, Zhengxiang Li, Yigang Xu, Xianhua Li, Gang Zhou, Haimin YeAbstract:New sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, geochemical data, and a synthesis of existing stratigraphic, geochronologic, and geochemical results from the Tarim block and the Central Asian orogenic belt in northwestern China suggest the presence of a Permian (ca. 275 Ma) large igneous province (the Bachu large igneous province). The large igneous province consists predominantly of coeval mafic rocks (basalts and mafic-ultramafic intrusions) having an aerial coverage of more than 600,000 km 2 , and its formation was accompanied by voluminous emplacement of A-type granites. This large igneous province, interpreted to be of Mantle Plume origin, is ∼15 m.y. older than the ca. 260 Ma Emeishan large igneous province in southwestern China and ∼25 m.y. older than the 251 Ma Siberian Trap in Russia. Such a sudden flair up of Plume activity in the Permian may represent the early stage of the Pangean superPlume event. The Permian Plumes likely played a role in late Paleozoic rapid continental crustal growth in the Central Asian orogenic belt. In addition, there appear to be two types of Mantle geochemical provinces (domains) in the region, a long-term enriched Tarim province and a subduction-metasomatized and depleted Central Asian orogenic belt province.
S A Gibson - One of the best experts on this subject based on the ideXlab platform.
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olivine chemistry reveals compositional source heterogeneities within a tilted Mantle Plume beneath iceland
Earth and Planetary Science Letters, 2020Co-Authors: Mb Rasmussen, S A Gibson, Sa Halldórsson, Gh GuðfinnssonAbstract:Abstract High-Fo olivine (Fo = Mg/(Mg+Fe) mol%) is an ideal proxy for establishing the compositions of primary melts and their Mantle sources. This has been exploited in establishing lithological variations in the Mantle source regions of oceanic basalts, including in Iceland. However, previous studies on Icelandic olivine lack spatial and temporal coverage. We present high-precision in-situ major, minor and trace element analyses of Fo-rich olivine from a suite of 53 primitive basalts erupted in the neovolcanic rift and flank zones of Iceland, as well as in older regions of Quaternary and Tertiary crust. Most of these samples have previously been analysed for 3He/4He, which ranges from 6.7 to 47.8 RA, the largest span reported for any oceanic island. By combining trace elemental variability with 3He/4He, we assess the extent of lithological variability in the Icelandic Mantle Plume. Trace-element ratios that are likely to preserve information about Mantle source regions (e.g., Mn/Fe, Ni/(Mg/Fe), Ga/Sc, Zn/Fe and Mn/Zn) suggest a peridotitic Mantle source in all rift-related volcanic regions, as well as in the off-rift flank zones of Oraefajokull and Snaefellsnes. However, a signal of a more pyroxenitic Mantle lithology is clearly visible in olivine from the South Iceland Volcanic Zone, which represents the southward propagation of the Eastern Rift Zone, while olivine from Tertiary lavas suggests a mixed peridotite-pyroxenite source composition. We are able to identify four components present in the Icelandic Mantle: a lithologically heterogeneous Plume component with 3He/4He >MORB; a depleted MORB-like peridotite; an isotopically enriched MORB-like peridotite; and a peridotitic component with 3He/4He
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head to tail transition of the afar Mantle Plume geochemical evidence from a miocene bimodal basalt rhyolite succession in the ethiopian large igneous province
Lithos, 2009Co-Authors: Dereje Ayalew, S A GibsonAbstract:Abstract Miocene rhyolites and basalts from the Ethiopian Large Igneous Province (LIP) crop out in north Shewa on the central Ethiopian plateau. The volcanics were emplaced at the onset of development of the Main Ethiopian Rift and postdate eruption of the Oligocene Ethiopian continental-flood basalt (CFB) province by ~ 15 Ma. Variations in major- and trace-element chemistry indicate that fractionation of the north Shewa parental magmas occurred at ~ 15 km depth; this is consistent with geophysical studies which have predicted the presence of gabbroic intrusions in the mid to upper parts of the underlying ~ 50 km thick crust. High-to-moderate [La/Nb]n (1.1–1.4) and Ce/Pb ratios (17–19.5) for the basalts, together with Mantle δ18O values for the rhyolites, suggest that the north Shewa magmas contain only minimal contributions of crustal melts. The formation of the Ethiopian CFB province has been associated with the sub-lithospheric impact of the Afar Mantle Plume ‘starting-head’ whereas recent volcanic activity in the Main Ethiopian rift has been linked to lithospheric extension and adiabatic decompression melting in the steady-state ‘tail’ of the Plume. Rare-earth element (REE) inversion modelling of Oligocene, Miocene and Recent mafic magmas from the Ethiopian LIP has allowed us to determine changes in the amount of partial melting that accompanied the head-to-tail transition of the Afar Plume. The results also provide information on the approximate depth of melting and Mantle potential temperature and allow us to assess how these have varied both spatially and temporally. The REE inversion results suggest that, since the Oligocene, the amount of adiabatic decompression melting has decreased two-fold, from 13 to 7%, and the potential temperature of the Afar Mantle Plume has decreased from ~ 1450 to 1350 °C. The ~ 15 Ma north Shewa basalts formed by slightly lower degrees of partial melting (5%) than those in the present-day rift, presumably due to the presence of thicker lithosphere (60 km) prior to the main phase of rifting during which the lithosphere thinned to ~ 50 km at the rift axis.
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volcanism in the vitim volcanic field siberia geochemical evidence for a Mantle Plume beneath the baikal rift zone
Journal of Petrology, 2005Co-Authors: Joanne S Johnson, S A Gibson, R N Thompson, G M NowellAbstract:The Baikal Rift is a zone of active lithospheric extension adjacent to the Siberian Craton. The 6-16 Myr old Vitim Volcanic Field (VVF) lies approximately 200 km east of the rift axi's and consists of 5000 km3 of melanephelinites, basanites, alkali and tholeiitic basalts, and minor nephelinites. In the volcanic pile, 142 drill core samples were used to study temporal and spatial variations. Variations in major element abundances (e.g. MgO = 3.3-14.6 wt reflect polybaric fractional crystallization of olivine, clinopyroxene and plagioclase. (0.7039-0.7049), (0.5127-0.5129) and (0.2829-0.2830) ratios are similar to those for ocean island basalts and suggest that the magmas have not assimilated significant amounts of continental crust. Variable degrees of partial melting appear to be responsible for differences in Na2O, P2O5, K2O and incompatible trace element abundances in the most primitive (high-MgO) magmas. Fractionated heavy rare earth element (HREE) ratios (e.g. Gd/Lun > 2.5) indicate that the parental magmas of the Vitim lavas were predominantly generated within the garnet stability field. Forward major element and REE inversion models suggest that the tholeiitic and alkali basalts were generated by decompression melting of a fertile peridotite source within the convecting Mantle beneath Vitim. Ba/Sr ratios and negative K anomalies in normalized multi-element plots suggest that phlogopite was a residual Mantle phase during the genesis of the nephelinites and basanites. Relatively high light REE (LREE) abundances in the silica-undersaturated melts require a metasomatically enriched lithospheric Mantle source. Results of forward major element modelling suggest that Melting of phlogopite-bearing pyroxenite veins could explain the major element composition of these melts. In support of this, pyroxenite xenoliths have been found in the VVF. High Cenozoic Mantle potential temperatures (∼1450° C) predicted from geochemical modelling suggest the presence of a Mantle Plume beneath the Baika1, Rift Zone
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early cretaceous basalt and picrite dykes of the southern etendeka region nw namibia windows into the role of the tristan Mantle Plume in parana etendeka magmatism
Journal of Petrology, 2001Co-Authors: R N Thompson, S A Gibson, A P Dickin, P M SmithAbstract:Abundant dykes in the southern Etendeka region, NW Namibia, mostly contain 8–20% MgO. Almost all can be allocated to previously described Early Cretaceous magma types. Horingbaai-type basalts–picrites occur up to 120 km inland. Some have superficially mid-ocean ridge basalt (MORB)-like compositions: (La/Nb)n 1·0; (Sm/Lu)n 1·5; Nd >8; initial 87Sr/86Sr 0·7032. Others show major- and trace-element, and Sr–Nd–Pb isotopic evidence of contamination during upwelling by up to a few per cent of K-feldspar-rich upper crust. Extremely magnesian olivine macrocrysts (Fo91–93·3) in some Horingbaai picrites indicate that komatiitic (MgO 24%) liquids were associated with this suite, although they were too dense to reach the crustal levels currently exposed. Ferropicrite dykes resemble closely the nearby Etendeka ferropicrite basal lavas, with total iron (as Fe2O3) >MgO; (La/Nb)n 1·0–1·5; (Sm/Lu)n 2·5–7; Nd 2–3, except in samples with geochemical evidence of contamination by Archaean–Proterozoic lower crust. A few low-Ti dykes resemble geochemically the lavas of the main southern Etendeka succession, with (La/Nb)n 2·0–2·5; Nd = 0 to -8; initial 87Sr/86Sr >0·707. Dykes north of the Huab river define a fourth magma type, Nil Desperandum (ND), that may have fed part of the Huab sill complex. The dyke ages are constrained by their field relationships. Ferropicrite and low-Ti dykes are consanguineous with lavas erupted at 133 and 132 Ma, respectively. Both Horingbaai and ND dykes cut 132 Ma Etendeka lavas, and the main swarm of Horingbaai picrites with forsteritic macrocrysts is cut by the 131 Ma Brandberg plutonic complex. Forward and inverse modelling of the genesis of the ferropicrites and the Horingbaai picrite–komatiites gives two temporal ‘windows’ into physicochemical conditions within the head of the impacting Tristan Mantle Plume. At 133 Ma the southern Etendeka lithosphere was >100 km thick and only incipient melting of predominantly Fe-rich peridotite streaks occurred in the rising Plume head (Tp = 1500°C). By 2 my later, pre-Atlantic extension had reduced the lithosphere thickness beneath and adjacent to NW Namibia, and there was intense melting (Tp = 1500–1700°C) of even depleted peridotite in the Plume head.
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late cretaceous rift related upwelling and melting of the trindade starting Mantle Plume head beneath western brazil
Contributions to Mineralogy and Petrology, 1997Co-Authors: S A Gibson, R N Thompson, A P Dickin, R K Weska, O H LeonardosAbstract:High Mantle potential temperatures and local extension, associated with the Late-Cretaceous impact of the Trindade Mantle Plume, produced substantial widespread and voluminous magmatism around the northern half of the Parana sedimentary basin. Our previous studies have shown that, above the central and eastern portions of the postulated impact zone where lithosphere extension is minimal, heat conducted by the Plume caused large-scale melting of the more fusible parts of the subcontinental lithospheric Mantle beneath the margin of the Sao Francisco craton and the surrounding Brasilia mobile belt. Here we combine geochemical data and field evidence from the Poxoreu Igneous Province, western Brazil to show how more intense lithospheric extension above the western margin of the postulated impact zone permitted greater upwelling and melting of the Trindade Plume than further east. Laser 40Ar/39Ar age determinations indicate that rift-related basaltic magmas of the Poxoreu Igneous Province were emplaced at ˜ 84 Ma. Our detailed geochemical study of the mafic magmas shows that the parental melts underwent polybaric crystal fractionation within the crust prior to final emplacement. Furthermore, some magmas (quartz-normative) appear to have assimilated upper crust whereas others (nepheline- and hypersthene-normative) appear to have been unaffected by open-system crustal magma chamber processes. Incompatible trace element ratios (e.g. chondrite-normalised La/Nb = 1) and isotopic ratios (87Sr/86Sr = 0.704 and 143Nd/144Nd = 0.51274) of the Hy-normative basalts resemble those of oceanic islands (OIB). We therefore propose that these “OIB-like” magmas were predominantly derived from convecting-Mantle-source melts (i.e. Trindade Mantle Plume). Inverse modelling of rare-earth element (REE) abundances suggests that the initial melts were predominantly generated within the depth range of ˜80–100 km, in Mantle with a potential temperature of ˜1500 °C.
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a permian large igneous province in tarim and central asian orogenic belt nw china results of a ca 275 ma Mantle Plume
Geological Society of America Bulletin, 2010Co-Authors: Chuanlin Zhang, Zhengxiang Li, Yigang Xu, Xianhua Li, Gang Zhou, Haimin YeAbstract:New sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, geochemical data, and a synthesis of existing stratigraphic, geochronologic, and geochemical results from the Tarim block and the Central Asian orogenic belt in northwestern China suggest the presence of a Permian (ca. 275 Ma) large igneous province (the Bachu large igneous province). The large igneous province consists predominantly of coeval mafic rocks (basalts and mafic-ultramafic intrusions) having an aerial coverage of more than 600,000 km 2 , and its formation was accompanied by voluminous emplacement of A-type granites. This large igneous province, interpreted to be of Mantle Plume origin, is ∼15 m.y. older than the ca. 260 Ma Emeishan large igneous province in southwestern China and ∼25 m.y. older than the 251 Ma Siberian Trap in Russia. Such a sudden flair up of Plume activity in the Permian may represent the early stage of the Pangean superPlume event. The Permian Plumes likely played a role in late Paleozoic rapid continental crustal growth in the Central Asian orogenic belt. In addition, there appear to be two types of Mantle geochemical provinces (domains) in the region, a long-term enriched Tarim province and a subduction-metasomatized and depleted Central Asian orogenic belt province.
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diverse permian magmatism in the tarim block nw china genetically linked to the permian tarim Mantle Plume
Lithos, 2010Co-Authors: Chuanlin Zhang, Hongyan WangAbstract:Abstract Zircon U–Pb ages and geochemical data are reported for the Piqiang oxide-bearing ultramfic–mafic complex, the Bachu mafic dyke swarm, the Yingan and Kaipaizileike basalts and the Halajun A-type granites in the Tarim Block, Northwest China. The Piqiang complex and the Halajun A-type granites were emplaced at ca. 276 Ma and ca. 278 Ma, respectively. Together with previously reported geochronological data, the diverse intrusive and extrusive rocks in Tarim show a peak age at ca. 275 Ma. Elemental and Nd isotope geochemistry suggests that the spatially and temporally related Piqiang complex (including some dolerite dykes or stocks) and the Halajun A-type granites were formed via crystal fractionation/accumulation of a common Plume-derived parental mafic magma (melting degree > 10%), coupled with variable extents of crustal contamination. Crystal fractionation/accumulation in one or several magma chambers resulted in the diversity of rocks types. The Bachu mafic dyke swarm shares a similar Mantle source with the intrusive rocks in the Piqiang–Halajun area but with a relatively lower degree of partial melting (~ 5%). In contrast, the basalts were derived from a time-integrated, enriched lithospheric Mantle source as suggested by their high-Ti, LREE- and LILE-enriched trace element signature and negative eNd(t) values (− 2.0 ~ −2.6). The synchronous yet diverse range of Permian igneous rocks in Tarim can best be accounted for by a Permian Mantle Plume, which is about 15 Ma earlier than the Emeishan Plume in southwestern China.