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A high‐resolution velocity and anisotropy model of the uppermost mantle under the Hainan Island and surrounding areas is obtained by a tomographic inversion of 8192 Pn arrival‐time data hand‐picked from high‐quality seismograms recorded at a total of 137 seismic stations of our recently deployed HAVESArray portable seismic network and Chinese provincial stations. Our new model shows obvious velocity and anisotropic structural features related to the distribution of Quaternary volcanic rocks on the surface. Extensive low Pn velocity anomalies are detected under the Weizhou Island, northern Hainan Island, southern Leizhou Peninsula, southern South China, and around the Pearl River Mouth Basin (PRMB), whereas high Pn velocity anomalies are imaged under the PRMB and areas of 108°–109°E and between the Baise‐Hepu fault and the Wuchuan‐Sihui fault. The Pn fast propagation directions exhibit a radiated pattern around the PRMB. Integrated with previous global and regional tomographic models, our present results indicate that the Hainan plume is upwelling around the PRMB in the upper mantle, and then plume‐related flow is split into several branches under the volcanoes in the northern Hainan Island, southern Leizhou Peninsula and Weizhou Island. This flow pattern could be associated with the westward deep subduction of the Philippine Sea and Pacific plates and eastward deep subduction of the Indian plate. Our results provide new insights into the formation mechanism of the Hainan‐Leizhou and Weizhou volcanoes. Plain Language Summary: The Quaternary volcanism in the Hainan and surrounding areas was very intense, and there were many periods of volcanic eruptions in the geologic history. The link among the Hainan, Leizhou, and Weizhou volcanoes is still unclear. Pn wave glides in the uppermost mantle and first arrives at a station within a certain epicentral distance. Therefore, Pn tomography has obvious advantages for revealing high‐quality velocity and anisotropy structural features of the uppermost mantle in the study region. Extensive low Pn velocity anomalies are revealed under the northern Hainan Island, southern Leizhou Peninsula, Weizhou Island, southern South China Block and around the Pearl River Mouth Basin (PRMB), whereas a radiated pattern of Pn fast‐propagation directions around the high‐V PRMB is revealed. These results suggest that multiple branches of mantle flows may exist under the Hainan, Leizhou, and Weizhou volcanoes from the Hainan mantle plume, probably due to the westward deep subduction of the Pacific plate and eastward deep subduction of the Indian plate. Key Points: A high‐resolution Pn anisotropy tomographic model in Hainan Island and surrounding areas is obtained with manually picked travel‐time dataSignificant low‐V anomalies are revealed in the northern Hainan Island, southern Leizhou Peninsula and Weizhou IslandA radiated pattern of anisotropy around the PRMB suggests the existence of multiple branches of the Hainan mantle plume [ABSTRACT FROM AUTHOR]

Our general understanding of mantle composition and dynamics mainly comes from the composition of lavas from oceanic intraplate volcanoes. They are generally accepted to originate from deep, relatively stationary mantle plumes. Many groups of seamounts comprising the West Pacific Seamount Province (WPSP), however, do not form long-lived, narrow and continuous chains of volcanoes with clear age progression; thus, their origin does not seem to fit this general model. Here we show a wide compositional spectrum of lavas from the Pako guyot within the Magellan seamount trail (MST), an age-progressive but short-lived volcanic chain in the WPSP. For the first time, both extreme high μ  = 238U/204Pb mantle (HIMU)- and enriched mantle 1 (EM1)-like mantle plume components occur in a single seamount in the Pacific Ocean. Based on alteration resistant trace element and Sr–Nd–Pb–Hf isotopic compositions, the Pako lavas fall into three distinct groups. Group 1 has a distinctive HIMU composition with high (206Pb/204Pb)i ratios (20.41–20.94) similar to the Arago (also known as 'Young Rurutu' or 'Atiu') hotspot composition, suggesting derivation from a HIMU mantle source. Groups 2 and 3 EM1-like lavas comprise the dominant rock type and display the largest Sr–Nd–Pb–Hf isotopic variations that can be best explained by mixing between melts of focal zone (FOZO) and EM1-like mantle components. Additionally, olivine phenocrysts from Group 3 EM1-like lavas have high Ni contents, Fe/Mn and Mn/Zn ratios and low Zn/Fe*10 000 ratios, which can be explained through fractional crystallization of high-pressure partial melts from fertile peridotite. The EM1-like Groups 2 and 3 lavas are compositionally similar to the Rarotonga hotspot composition, suggesting that the MST is possibly an old trace of the Rarotonga hotspot, which is most likely a long-lived hotspot generated above a deep mantle plume. Combined with existing geochemical and tectonic data, we propose that the Magellan seamounts were likely derived from partial melting of a heterogeneous mantle plume containing HIMU, FOZO and EM1-like components. Alternatively, they could have been derived from the Arago and Rarotonga mantle plumes, each having its distinct compositional signature. The occurrence of HIMU- and EM1-like mantle plume components in a single volcano suggests that the superposition of compositionally different hotspot volcanic trails in the South Pacific could have played an important role in the generation of the WPSP. [ABSTRACT FROM AUTHOR]

Olivine‐hosted melt inclusions have the potential to provide direct evidence about the nature of the mantle sources of magmas. In this study, we report the major and trace element and Sr–Nd–Pb–Hf isotope compositions of the Lijiang picrites from the Emeishan large igneous province, as well as major and trace element and Pb isotopic compositions of olivine‐hosted melt inclusions in the picrites. Using these data, we infer the nature of the mantle sources for the Lijiang high‐Ti picrites (Ti/Y = 645–654), and compare them with the Dali low‐Ti picrites (Ti/Y = 351–408). Lijiang melt inclusions have highly heterogeneous Pb isotope compositions (208Pb/206Pb = 2.015–2.201, 207Pb/206Pb = 0.812–0.882, 260 Ma age‐corrected) that overlap the majority of the fields from FOZO to enriched mantle 1 (EM1). The primitive mantle‐normalized trace element patterns of these melt inclusions reveal an enriched composition with depletions in Ba, Nb, Ta, Zr, and Hf. We suggest that an old recycled GLOSS II‐like sediment was probably the main component that imparted the EM1 signature into the sources of the Lijiang picrites. Furthermore, we reverse calculated the mantle potential temperature (Tp) beneath Lijiang and Dali using the Al‐in‐ol temperature. The estimated mantle Tp beneath Lijiang is lower than Dali. We infer that the Lijiang picrites might have originated from the mantle plume with lower thermal energy, corresponding to the waning stage of the axis of the Emeishan mantle plume. Our study suggest that high‐Ti magmas of the Emeishan large igneous province were derived from those parts or stages of the mantle plume with lower thermal energy. Key Points: Highly heterogeneous Pb isotope compositions of olivine‐hosted melt inclusions are found in the Lijiang picritesGLOSS II‐like subduction sediments are responsible for the enriched mantle 1‐like component in the source of the Emeishan large igneous province (LIP)Thermal variation of the mantle plume controlled the types and distribution of basaltic magmas in the Emeishan LIP [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at ∼1.9 Ga. After cratonization, the NCC was essentially stable until the Mesozoic, when intense felsic magmatism and related mineralization, deformation, pull-apart basins, and exhumation of the deep crust widely occurred, indicative of destruction or decratonization. Accompanying this destruction was significant removal of the cratonic keel and lithospheric transformation, whereby the thick (∼200 km) and refractory Archean lithosphere mantle was replaced by a thin (<80 km) juvenile one. The decratonization of the NCC was driven by flat slab subduction, followed by a rollback of the paleo-Pacific plate during the late Mesozoic. A global synthesis indicates that cratons are mainly destroyed by oceanic subduction, although mantle plumes might also trigger lithospheric thinning through thermal erosion. Widespread crust-derived felsic magmatism and large-scale ductile deformation can be regarded as petrological and structural indicators of craton destruction. ▪ A craton, a kind of ancient continental block on Earth, was formed mostly in the early Precambrian (>1.8 Ga). ▪ A craton is characterized by a rigid lithospheric root, which provides longevity and stability during its evolutionary history. ▪ Some cratons, such as the North China Craton, can be destroyed by losing their stability, manifested by magmatism, deformation, earthquake, etc. [ABSTRACT FROM AUTHOR]

Numerous alkaline basaltic dykes crosscut the Early Permian Xiaohaizi wehrlite in drill-cores and syenite intrusion in the Tarim large igneous province, NW China. One basaltic dyke contains abundant clinopyroxene macrocrysts with strong resorption textures. Such a textural disequilibrium is consistent with their contrasting chemistry between the macrocrysts (Mg# = 80–89) and the host dyke (Mg# = 39, corresponding to Mg# = 73 of clinopyroxene in equilibrium with the dyke), indicating that they are not phenocrysts. The clinopyroxene macrocrysts are characterized by low TiO 2 (0.26–1.09 wt.%), Al 2 O 3 (1.15–3.10 wt.%) and Na 2 O (0.16–0.37 wt.%), unlike those in mantle peridotites but resembling those in layered mafic intrusions in the same area. The clinopyroxene macrocrysts and the clinopyroxenes from the Xiaohaizi cumulate wehrlites define a coherent compositional trend and have identical trace element patterns, pointing to a comagmatic origin for these crystals. Accordingly, the macrocrysts cannot be xenocrysts foreign to the magmatic system. Rather they are antecrysts that crystallized from progenitor magmas and have been reincorporated into the host dyke before intrusion. The 87 Sr/ 86 Sr i (0.7035–0.7037) and εNd i (4.5–4.8) of the clinopyroxene macrocrysts with high Mg# (80–89) are apparently lower and higher than their respective ratios of the clinopyroxenes in the wehrlites (Mg# = 75–84, 87 Sr/ 86 Sr i = 0.7038–0.7041, εNd i = 1.0–1.9). This difference in isotopes can be accounted for by assimilation and fractional crystallization (AFC) process operated during the formation of the Xiaohaizi intrusion. In this sense, the clinopyroxene macrocrysts record the composition of the uncontaminated Tarim plume-derived melts. [ABSTRACT FROM AUTHOR]

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-Al 2 O 3 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-Al 2 O 3 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 Al 2 O 3 (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. [ABSTRACT FROM AUTHOR]

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. 276Ma and ca. 278Ma, respectively. Together with previously reported geochronological data, the diverse intrusive and extrusive rocks in Tarim show a peak age at ca. 275Ma. 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 εNd(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 15Ma earlier than the Emeishan plume in southwestern China. [ABSTRACT FROM AUTHOR]

Abstract: The ~260Ma Emeishan Large Igneous Province (ELIP) in southwest China has previously been demonstrated to provide compelling evidence for pre-volcanic crustal doming in support of the mantle plume hypothesis. However this has been questioned by Ukstins-Peate and Bryan (2008) by showing hydrothermal magmatic activity at the Daqiao section. To solve this argument, a detailed characterization of the contact between the Emeishan basalts and the Maokou Formation was carried out. The contact is shown to be an unconformity, which is characterized by paleokarst on top of the Maokou Formation, including paleokarst relief, sinkholes, caves, tower karst and its corresponding rocks (such as kaolinite, bauxite and ferruginous duricrust and collapsed breccias, etc.). This paleokarst unconformity was in turn covered or infilled by the Emeishan basalts and tuffs, suggesting that uplift and erosion occurred prior to the eruption of the ELIP. The extent of erosion of the Maokou Formation indicates the ELIP can be divided into three roughly concentric zones: the inner, intermediate, and outer zones. The paleokarst features on the top of Maokou Formation vary across the ELIP. In the inner zone, a likely sinkhole and an incision valley with 450m relief in height are found. In the intermediate zone, various paleokarst landforms such as karst relief, sinkholes and tower karsts are well developed. Some sinkholes that developed in the Qixia Formation below the Maokou Formation imply that the paleorelief is more than 350m in height. In the outer zone, the paleokarstic surface is a paleo-weathering layer with minor karstification and development of caves at 10–50m. This spatial variation of the paleokarst reflects variation of uplift height across the ELIP. The extent of minimal uplift is estimated to be at least 450m in the inner zone, 350m in the intermediate zone, whereas uplift is minor (tens-50m) in the outer zone. The magnitude and shape of the uplift is roughly consistent with that predicted by mantle plume models. The paleokarst was formed after the deposition of the Maokou Formation and the eruption of the Emeishan basalts at the end-Guadalupian and indicates a short duration of uplift. Thus this study lends further support to domal uplift prior to the Emeishan flood volcanism, but also to the mantle plume initiation model for the generation of the ELIP. [Copyright &y& Elsevier]

Biostratigraphic and sedimentologic investigations in 67 sections have been carried out for the Middle Permian Maokou Formation that immediately underlies the Emeishan flood basalts in southwest China. The results suggest a domal crustal thinning before the emplacement of the Emeishan large igneous province. Variably thinned carbonates in the Maokou Formation are capped by a subaerial unconformity, which is generally manifested by karst paleotopography, paleoweathering zone, or locally by relict gravels and basal conglomerates. Provenance analysis indicates that these gravels and conglomerates were mainly derived from the uppermost Maokou Formation. Therefore, the stratigraphic thinning likely resulted from differential erosion due to regional uplift. Iso-thickness contours of the Maokou Formation delineate a subcircular uplifted area, in accordance with the crustal doming caused by a starting mantle plume as predicted by experimental and numerical modeling. The duration of this uplift is estimated to be less than 3 Myr and the magnitude of uplift is greater than 1000 m. The sedimentary records therefore provide independent supporting evidence for the mantle plume initiation model for the generation of the Emeishan flood basalts. [Copyright &y& Elsevier]

The contribution of recycled oceanic crust to the mantle source of mid-ocean ridge basalts (MORBs) remains a subject of debate, as radiogenic isotopes alone yield ambiguous insights. Here, we present comprehensive data on whole-rock major element, trace element, and Mo–Nd–Hf isotopic compositions for MORB samples from International Ocean Discovery Program Expedition 349 sites U1431E and U1433B in the eastern (ESB) and southwestern (SWB) subbasins, respectively, of the South China Sea (SCS). The δ98/95Mo values of the SCS MORBs exhibit a significant range (from −0.80‰ to +0.05‰), in contrast to the restricted composition observed in MORBs (δ98/95Mo = −0.19‰ ± 0.01‰). The ESB MORBs display extremely light Mo isotopic compositions (δ98/95Mo = −0.80‰ to −0.24‰) with Nd Hf isotopic compositions similar to those of Pacific MORB, whereas the SWB MORBs show higher δ98/95Mo values (−0.44‰ to +0.05‰) and depleted Nd Hf isotopic compositions. The δ98/95Mo values of the SCS MORBs are negatively correlated with Ce/Mo ratios and positively correlated with ε Hf values, suggesting the incorporation of dehydrated slab components into the source of the SCS MORBs. The subbasin-scale mantle heterogeneity in the SCS can be best explained by varying degrees of interaction between a mantle plume and stagnant slabs in the mantle transition zone, as suggested by mantle tomography. The rigid stagnant slab in the mantle transition zone beneath the SWB largely impeded the upwelling of the mantle plume, whereas the slab beneath the ESB was disrupted by the plume and subsequently transported into the upper mantle. This study, therefore, provides compelling evidence for the involvement of recycled oceanic slabs in generating MORB and the influence of an ascending mantle plume on seafloor spreading in a continental marginal sea. Mantle recycling processes in marginal sea basins exhibit distinct characteristics compared to those occurring in open oceans. • The SCS MORBs mainly show much lower δ98/95Mo values than global MORB. • Extremely light Mo isotopes in the SCS MORBs result from abundant ROC in the source. • The Mo isotopic compositions of the SCS MORBs exhibit subbasin-scale variations. • Plume-stagnant slab interaction leads to large-scale mantle heterogeneity in the SCS. [ABSTRACT FROM AUTHOR]

Abstract Testing the hypothesis that the Hainan mantle plume triggered the opening of the South China Sea (SCS) and interacted with the spreading ridge is important for the purpose of understanding the dynamics of the evolution of the SCS. This study examined the most primitive olivine (Fo = 83.1–87.1) and spinel (Cr# = 28–60%) in the basalt and glassy samples collected from Hole U1431E of International Ocean Discovery Program (IODP) Expedition 349, with the goal of estimating the crystallization temperature. Spinels mostly enclosed by olivines have low Fe3+ and Ti contents and show compositional equilibrium with the host olivines. The application of the Al-in-olivine thermometer provided crystallization temperatures for the studied samples, which varied from 1208 ± 29 °C to 1287 ± 29 °C. When extrapolating to primitive olivine of Fo = 90, the crystallization temperature of primitive olivine is approximately 1350 °C, which is much higher than that of other primitive mid-ocean ridge basalt (MORB) but comparable to that of Iceland oceanic island basalt (OIB). Therefore, the mantle potential temperature at the extinct ridge of the SCS at ~16 Ma is much higher than that beneath a normal mid-ocean ridge, manifesting the mantle plume-ridge interaction during the last spreading of the SCS. Given the lack of thick oceanic crust, seamount chains or lineaments in the SCS, we propose that this plume impacted on the SCS might be eclogite-rich and of low buoyancy. Highlights • Primitive olivine in the SCS MORB has high crystallization temperature of ~1350 °C. • Mantle plume had interacted with the spreading mid-ocean ridge of the SCS. • The plume impacted on the SCS might be eclogite-rich and of low buoyancy. [ABSTRACT FROM AUTHOR]

• The isotope compositions of Magellan seamount lavas range from HIMU to EM1 plus EM2. • The HIMU-type compositions are widely distributed in the Magellan area. • Overlapping hotspot tracks generated the co-occurrence of HIMU and EM components. • Several seamounts in the Magellan area are not related to any Pacific hotspot. • Melting of diffuse plume materials along lithosphere fractures forms non-hotspot related lavas. An oceanic volcanic chain with linear age–distance relationships is generally attributed to originate from a primary mantle plume. The origin of many seamount groups in the West Pacific Seamount Province (WPSP), however, is enigmatic since they do not form narrow, age-progressive chains of volcanoes, but are characterized by irregular age-distance relationships. To investigate the origin of such seamounts, here we report new 40Ar/39Ar age, major and trace element, and Sr-Nd-Pb-Hf isotope data for lavas from Ita-Mai-Tai, Kocebu, Govorov, Skornyakova, and Gordin seamounts of the Magellan seamount group (MSG) in the WPSP. Lavas from these seamounts cover a wide range of isotopic compositions from high μ (=238U/204Pb) mantle (HIMU) to enriched mantle 1 (EM1) and 2 (EM2). Skornyakova and Govorov seamounts display predominantly EM1-like compositions with one sample from Skornyakova displaying a HIMU-like composition (e.g., (206Pb/204Pb) i = 19.87) and two samples from Govorov displaying EM2-like compositions. Kocebu lavas have HIMU-like isotopic compositions with high (206Pb/204Pb) i (up to 20.26). Together with the HIMU lavas in Pako guyot of the Magellan seamount trail, we propose that the HIMU component is most likely widespread in the Magellan area. The Magellan HIMU-like lavas exhibit slightly elevated (208Pb/204Pb) i for a given (206Pb/204Pb) i ; this signature most likely originates from the Arago mantle plume. The co-occurrence of HIMU, EM1, and EM2 components in the MSG most likely results from overlapping of Arago, Rarotonga, and Samoa hotspot tracks. Combined with previous age data, the ages of EM1-type Ita-Mai-Tai, Skornyakova, and Gordin (84.2–95.4 Ma) seamounts do not lie on any particular South Pacific hotspot tracks, suggesting that they unlikely originated directly from deep mantle plumes. Their plume-like signatures most likely resulted from melting of diffuse plume materials mainly from Rarotonga and Samoa and to a lesser extent Macdonald plumes in the northern EM-domain of Cook-Austral volcanic lineament in response to lithosphere fracturing. We propose that overlapping of different hotspot tracks combined with preferential channeling of new magmas through pre-existing structural weaknesses or volcanic conduits control the complex age-spatial-geochemical relationships of intraplate seamount groups in the WPSP. [ABSTRACT FROM AUTHOR]

The geochemistry of oceanic intraplate (primarily oceanic island and seamount) lavas can provide essential information on the composition and evolution of their mantle source and geodynamics. Due to very limited rock sampling of the many mid-Cretaceous Wake seamounts in NW Pacific, the mantle source lithology and petrogenesis of their lavas, and the geodynamic mechanism responsible for generating the lavas have not been fully delineated. In order to help resolve these issues, here we present whole-rock major-trace element and Sr-Nd-Pb-Hf isotopic data for twenty-one lava samples collected from Lamont, Dacheng, Xufu, Penglai, Niulang, Zhinyu, and Zhanlu seamounts in the Southern Wake seamount trail (WST). These lava samples are silica-undersaturated alkali basalt and basanites/nephelinite. They have high CaO, FeOT and TiO 2 contents and CaO/Al 2 O 3 ratios, consistent with their derivation from partial melting of a carbonated peridotite or reaction between carbonated MORB-eclogite-derived silicate melts and fertile peridotite. High Zr/Hf and negative Zr-Hf-Ti anomalies in the most mafic lavas further suggest a contribution from carbonated components in their mantle source. These lavas show FOZO (focal zone)-HIMU (high μ = 238U/204Pb)-like Sr-Nd-Pb-Hf isotopic compositions (e.g., (206Pb/204Pb) i = 19.36–20.72), falling within the Arago (also known as "Young Rurutu" or "Atiu") hotspot field. Combined with the sparse previous age and geochemical data, we propose that WST lavas were most likely derived from partial melting of secondary plume clusters emanating from the top of Arago mantle plume trapped at the mantle transition zone. Alternatively, WST lavas could have come from a number of secondary plumelets emanating from the top of the Pacific Large Low Shear Velocity Province (LLSVP). The simultaneously upwelling secondary plumes or plumelets generated chronologically overlapping, compositionally similar and closely-spaced Wake seamounts atop the moving Pacific plate. • Comprehensive dataset of lavas from southern Wake seamount trail (WST). • Lavas formed from melting of carbonated peridotite or reaction between carbonated eclogite-derived melts and peridotite. • Lavas show FOZO-HIMU Sr-Nd-Pb-Hf isotopic compositions similar to Arago hotspot. • WST originated from partial melting of secondary plumes similar to Arago composition. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: A suite of picrites and basalts from the Muli area, in the northwestern part of the Emeishan continental flood basalt province, provides new and valuable information on the geochemistry of the Emeishan Large Igneous Province (LIP) and its source. The Muli picrites can be classified as type-1 or type-2. The former shows ocean–island basalt-like trace element characteristics, with γOs (260Ma) values and εNd (260Ma) values ranging from +7.5 to +11.5 and from +6.0 to +7.8, respectively. This is the first time that picrites with highly radiogenic Os and high Os contents (up to 3.3ppb) have been recognized in the Emeishan LIP. These characteristics probably reflect a relatively enriched component in the Emeishan LIP source. The type-2 picrites are characterized by non-radiogenic γOs (260Ma) values ranging from −4.2 to −0.3, and they may be further subdivided into type-2A and type-2B picrites. Type-2A picrites contain moderate amounts of the light rare earth elements (LREEs), have low CeN/YbN values (1.1–2.0), and a relatively high initial εNd (+5.0 to +6.6). In terms of Os and Nd isotopes, the Muli type-2A picrites are similar to the Song Da komatiites of Vietnam and the Gorgona Island picrites, revealing the existence of a depleted mantle component in the Emeishan LIP source. In contrast with the type-2A picrites, type-2B lavas exhibit a negative Nb anomaly and relatively lower initial εNd and γOs values (Nb/La>1.8; εNd (260Ma)=−5.5 to +6.4; γOs (260Ma)=−4.2 to −1.9), suggesting that the type-2B lavas have a depleted mantle source, similar to type-2A, but that the type-2B lavas are also influenced by various degrees of mixing of depleted plume-derived melt, sub-continental lithospheric mantle, and/or continental crust. Given that the basalts in the Muli area show similar geochemical features to those of the type-2B picrites, their origins are inferred to be similar. [Copyright &y& Elsevier]

• Two igneous pulses (ca. 290 Ma and 285 Ma) recognized for the Qiangtang-Panjal LIP. • The LIP was generated by a mantle plume and emplacement guided by slab pull forces. • The Neo-Tethys Ocean was initially opened at ∼285 Ma phase. Northward drift of the Cimmerian microcontinents and opening of the Neo-Tethys Ocean in Early Permian are prominent events in northern Gondwana's protracted breakup history. However, the geodynamic setting responsible for these events is controversial. The dispersal of the eastern Cimmerian microcontinents was accompanied by the emplacement of Qiangtang-Panjal large igneous province (QP-LIP). Previously published zircon U-Pb data imply the QP-LIP was emplaced over a long interval (320-280 Ma) but are inconsistent with the short eruption interval constrained by biostratigraphic studies. New secondary ion mass spectrometry (SIMS) zircon U-Pb ages from 15 mafic dikes and gabbroic intrusions from the Southern Qiangtang terrane as well as age data from other parts of the QP-LIP show a much shorter duration (∼ 290 − 285 Ma) for this LIP. The QP-LIP was characterized by an initial ∼290 Ma alkalic and tholeiitic phases and a subsequent ∼285 Ma tholeiitic phase, in agreement with regional biostratigraphic data constraining the timing of departure of the eastern Cimmerian microcontinents from Gondwana at ∼285 Ma and the opening of the Neo-Tethys Ocean. The QP-LIP was most likely the consequence of the arrival in the upper mantle of a mantle plume beneath the northern Gondwanan margin. This event, in combination with slab pull associated with subduction beneath Laurasia, may have caused extension and rifting of east Cimmerian continental fragments from the northern margin of Gondwana. This study may elucidate the mechanism responsible for repeated episodes of one-way northward drifting terranes from northern Gondwana that commenced in Paleozoic. [ABSTRACT FROM AUTHOR]