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Mantle plumes can encounter stagnant slabs in the mantle transition zone (MTZ) during their ascent from the lower mantle to Earth's surface. However, the interactions between stagnant slabs and mantle plumes remain poorly understood. This study presents new data on the spatial thermal-lithological-chemical heterogeneity in the mantle over a vast area of Southeast Asia that reflects the variable influence of a late Cenozoic mantle plume. Site U1433 of International Ocean Discovery Program (IODP) Expedition 349 in the southwest sub-basin of the South China Sea (SCS) is located near the center of this seismically imaged mantle upwelling. This area also contains midocean ridge basalt (MORB) derived from a peridotite-dominated and normal temperature mantle source with a depleted Nd-Hf and enriched 207Pb/206Pb isotopic composition. In contrast, MORB from Site U1431 of IODP Expedition 349 within the eastern sub-basin of the SCS and other intraplate basalts from the Hainan-Leizhou area, the eastern Indochina block, and elsewhere in the SCS are dominantly sourced from higher temperature pyroxenite-enriched mantle material that records mantle plume activity. These observations are in contrast with previous models involving a single plume rising from the lower mantle beneath the SCS that then tilted toward Hainan Island, China. Instead, it is likely that the observations from this region are indicative of plume-stagnant slab interaction. The shallow upper mantle beneath Site U1433 has not been influenced by a mantle plume as the presence of stagnant slabs within the MTZ prevented further upwelling of the plume. In contrast, a mantle plume passed through the weaker MTZ within the eastern sub-basin and circum-SCS areas, allowing plume-related magmatism to occur. The bifurcation of a deep-rooted mantle plume by stagnant slabs in the MTZ produced a cluster of small mantle upwellings that ascended to shallow depths, consistent with new multiscale global tomographic data for Southeast Asia. [ABSTRACT FROM AUTHOR]

Paleogene mafic potassic and ultrapotassic volcanic rocks in western Yunnan, China, show a compositional spectrum from potassic trachybasalt to latite (MgO = 6·24–21·8 wt %; SiO2 = 44·5–59·1 wt %). These rocks have high K2O (3·07–5·28 wt %), relatively low Na2O (0·99–4·18 wt %) and high K2O/Na2O ratios (0·91–3·89). They share geochemical features such as depletion of Ta, Nb and Ti relative to other similarly incompatible elements and enriched Sr–Nd isotopic compositions (initial 87Sr/86Sr of 0·7056–0·7101; &varepsilon;Nd(t) of –0·97 to –4·36). The rocks contain abundant olivine and clinopyroxene phenocrysts and xenocrysts. Clinopyroxene phenocrysts show complex zoning patterns (e.g. normal, reverse and oscillatory) and are all characterized by high Mg-number (0·77–0·90), low TiO2 (0·13–0·29 wt %), Al2O3 (0·73–1·68 wt %) and Na2O (0·22–0·42 wt %) with similar Ti/Al (0·06–0·16) and convex-upward rare earth element (REE) patterns, which are apparently in equilibrium with the host melts. Green cores in some clinopyroxene phenocrysts are characterized by low Mg-number (0·50–0·74) and Ti/Al (<0·05), high Al2O3 (1·66–3·63 wt %), Na2O (0·87–2·17 wt %) and AlVI/AlIV (0·38–0·76), and have chondrite-normalized REE patterns convex-upward from La to Dy and convex-downward from Dy to Lu. We interpret these green cores as xenocrysts from the wall-rocks. All these observations indicate complex magma chamber processes including extensive fractional crystallization, phenocryst accumulation and multiple melt replenishment of similar parental melts with discernible, but limited crustal contamination. All the olivine crystals (Fo = 94–75%) have high CaO contents (>0·1 wt %), indicative of a magmatic origin. The NiO decrease with decreasing Fo is consistent with the effect of fractional crystallization. High-Mg olivines (i.e. those with Fo > 90) are best interpreted as having crystallized from the ultrapotassic magma system (vs mantle olivines) because their spinel inclusions have high Cr-number and low Al2O3 and TiO2, consistent with a magmatic (vs mantle) origin. High fO2 values calculated from the spinels indicate that the parental melts were oxidized, with high Fe3+/FeTot or low Fe2+/FeTot, which explains the high Mg-number [= Mg/(Mg + Fe2+)] of the melts and the high-Mg olivines. The high fO2 of the ultrapotassic magmas is probably inherited from their high fO2 metasomatically enriched lithospheric mantle source. Very low-degree partial melting of metasomatized mantle lithosphere best explains the petrogenesis of these ultrapotassic rocks. The metasomatism may have been relatively recent, probably since the Emeishan flood basalt magmatism in the late Paleozoic in the region. The metasomatic agent may be dominated by a carbonatitic melt, which has imprinted the enriched Sr–Nd–Pb isotopic signature and incompatible element enrichments with conspicuous negative Ta–Nb–Ti anomalies seen in the resulting potassic and ultrapotassic volcanic rocks. Fractionation of Ti-rich amphiboles during melt ascent may have also magnified the geochemical signatures of these rocks. [ABSTRACT FROM PUBLISHER]

Petrographic investigations and electron microprobe analyses have been performed on a rare aggregate of clinopyroxene megacrysts collected from Cenozoic basalts in Yinfengling, Leizhou Peninsula of South China. The aggregate, composed of several clinopyroxene megacrysts, shows abundant exsolution lamellae of garnet (Grt) and orthopyroxene (Opx), and granular texture. Cr- and Ti-poor spinels are also present in this sample. They occur predominantly as Sp–Opx–Grt clusters (Cr# = 0.025–0.034) at the interspace between different megacrysts, and subordinately as bleb-shaped (Cr# = 0.025–0.034) or thin-lamella crystals (Cr# = 0.006–0.021) in clinopyroxene. Three different assemblages of exsolution are identified, namely (1) Sp (high Cr/Al) and Opx; (2) Grt–Opx; (3) Sp (low Cr/Al) and Opx. In addition, some garnets were likely developed as response to breakdown of the high-Cr/Al Sp. The homogeneous compositions in all constituent minerals and the good agreement between calculated Cpx/Grt partition coefficients ( K d’s) for trace elements and reference data strongly suggest a chemical equilibrium among coexisting minerals, probably attained by diffusion after the exsolution. Thermobarometric calculation based on exsolved assemblage yields a temperature of 900 ± 30°C and a pressure of 12 ± 2.2 kbar, corresponding to the present-day thermal gradient in the region. Much higher P–T estimates ( T = 1,210 ± 30°C, P = 16.2 ± 3.5 kbar) are obtained for the reconstructed composition of cpx prior to exsolution. The contrast in thermal state before and after the exsolution might reflect the thermal evolution of the lithosphere beneath South China during the Cenozoic. [ABSTRACT FROM AUTHOR]

Chronological, geochemical and Sr–Nd–Pb isotopic analyses have been carried out on the Mesozoic plutons in western Shandong with the aim of characterizing crustal–mantle evolution during the tectono-thermal reactivation of the craton. Detailed SHRIMP zircon U–Pb dating reveals two main periods of Mesozoic activity with contrasting compositions. The older magmatic pulse is manifested by monzonites and monzodiorites from Tongshi for which zircon rims yield a concordant age of 177±4 Ma and the cores have a discordant age of ca. 2.5 Ga. Low MgO and Cr, high Na2O contents and especially their isotopic compositions (87Sr/86Sr < 0.7042, 206Pb/204Pb < 16.8 and εNd ~ -12) are consistent with derivation from late Archean–Paleoproterozoic lower crust. Relatively high HREE contents in these Jurassic plutons indicate a garnet-free source (<32 km), in contrast to the garnet-bearing source (>40 km) of the late Mesozoic high Sr and low Y granitoids from the same region. Distinctively different depths of crustal melting suggest dynamic thickening of the crust by magmatic underplating during the Jurassic and Cretaceous. The younger dioritic plutons from Laiwu and Yinan were emplaced at 132–126 Ma and show relatively high MgO and Cr contents and large isotopic variability. They were likely derived from enriched lithospheric mantle source and were subjected to crustal contamination during magma evolution. Early Cretaceous mantle melting is coeval with the widespread late Yanshanian granitic magmatism in North China. Early Cretaceous time may correspond to a critical period when a temperature increase due to lithospheric thinning allowed the intersection of the local geotherm and the wet peridotite solidus. While some mantle-derived magmas were erupted, most were trapped at variable crustal depths, triggering large-scale concomitant melting of the crust. Lithospheric thinning must have continued until the late Cretaceous because of the change in the source of mafic magmas from lithospheric to asthenospheric at that time. It is proposed that removal of the lithospheric keel beneath the North China craton may have been initiated as early as the Jurassic, but with the most intense period in the Cretaceous between 130–75 Ma. Such a relatively long timescale (~100 Ma) emphasizes the role of thermomechanical erosion by convective mantle in lithospheric thinning beneath this region. [ABSTRACT FROM AUTHOR]

The identification of an eroded fore-arc crust component in arc magmas is challenging due to the combined effects of mantle metasomatism and crustal assimilation--fractional crystallization. In this study, molybdenum (Mo) isotope compositions are used in conjunction with Sr-Nd-Hf isotopic and elemental data to identify eroded fore-arc crust components in adakites from the Cuyapo and Balungao volcanoes of the northern Bataan segment of the Luzon arc (Philippines). The Mo isotopic ratios (δ98/95Mo, relative to the NIST SRM 3134 standard) of these adakites increase with increasing εNd (+4.3 to +5.6) and Ba/Nb (206--286). The low δ98/95Mo (-0.36‰ to -0.26‰) in the Cuyapo adakites coupled with low Sr-Nd-Hf isotopic ratios suggests contributions from the residual slab, which lost isotopically heavy Mo during dehydration. Interestingly, the high δ98/95Mo (-0.18‰ to 0.00‰) Balungao adakites have Mo-Sr-Nd-Hf isotopic ratios similar to those of the Luzon basement. Fractionated Nb/Ta (16--18) and high Sr/Y indicate the coexistence of melt with residual rutile and garnet ± amphibole assemblages, corresponding to a source region (>-45 km) below the present Luzon crust (-33 km). This thus suggests an origin of heavy Mo from partial melting of eroded crust in the mantle wedge rather than in the upper-plate crust. Our work not only demonstrates that Mo isotopes may be a potential tracer of eroded crust but also highlights that lavas with combined high δ98/95Mo, εNd, and Ba/Nb emplaced at subduction zones with juvenile arc crust may be a result of subduction erosion. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effects of porous gradient composites with hydroxyapatite/zirconia and autologous iliac in repair of lumbar vertebra body defects in dogs. Methods: (I) New porous gradient hydroxyapatite/zirconia composites were prepared using foam immersion, gradient compound and high temperature sintering; (2) A total of 18 adult beagle dogs, aged five to eight months and weighted 10-13 kg, were randomly assigned into two subgroups, which were implanted with new porous gradient hydroxyapatite/ zirconia composites (subgroup A in 12) or autologous iliac bone (subgroup B in 6); (3) The post-operative data were analyzed and compared between the subgroups to repair the vertebral body defect by roentgenoscopy, morphology and biomechanics. Results: The porosity of new porous gradient hydroxyapatite/zirconia composites is at 25 poles per inch, and the size of pores is at between 150 and 300 μm. The post-operative roentgenoscopy displayed that new-bone formation is increased gradually, and the interface between composites and host-bone becomes became blur, and the new-bone around the composites were integrated into host-bone at 24 weeks postoperatively in subgroup A. As to subgroup B, the resorption and restructure were found at six weeks after the surgery, and the graft-bone and host-bone have been integrated completely without obvious boundary at 24 weeks postoperatively. Histomorphologic study showed that the amount of bone within pores of the porous gradient hydroxyapatite/zirconia composites increased continuously with a prolonged implantation time, and that partial composites were degradated and replaced by new-bone trabeculae. There was no significant difference between subgroups (P>0.05) in the ultimate compressive strengths. Conclusion: New porous gradient hydroxyapatite/zirconia composites can promote the repair of bony defect, and induce bone tissue to ingrow into the pores, which may be applied widely to the treatment of bony defect in the future. [ABSTRACT FROM AUTHOR]

The Early Permian Tarim large igneous province (LIP) in northwestern China comprises voluminous basaltic lava flows, as well as ultramafic and silicic intrusions. The age and duration of the Tarim LIP remains unclear, and thus the rate of magma production and models of potential environmental effects are uncertain. Here we present high-precision chemical abrasion--isotope dilution--thermal ionization mass spectrometry zircon U-Pb ages for three newly discovered tuff layers interlayered with lava flows in the Kupukuziman and Kaipaizileike formations in the Keping area (Xinjiang, northwest China). The volcanism of the Kupukuziman Formation is constrained to a short duration from 289.77 ± 0.95 to 289.41 ± 0.52 Ma. An age for the overlying Kaipaizileike Formation is 284.27 ± 0.39 Ma, bracketing the duration of the entire eruptive phase of the Tarim flood basalts at ~5.5 m.y. The low eruption rate and relatively long duration of magmatism is consistent with a plume incubation model for the Tarim LIP. [ABSTRACT FROM AUTHOR]

Acoustic characteristics of pulse detonation engine (PDE) sound propagating in enclosed space are numerically and experimentally investigated. The finite element software LS-DYNA is utilized to numerically simulate the PDE sound propagating in enclosed space. Acoustic measurement systems are established for testing the PDE sound in enclosed space, and the time-frequency characteristics of PDE sound in enclosed space are reported in detail. The experimental results show that the sound waveform of PDE sound in enclosed space are quite different from those in open space, and the reflection and superposition of PDE sound on the walls of enclosed space results in the sound pressure oscillating obviously. It is found that the peak sound pressure level (PSPL) and overall sound pressure level (OASPL) of PDE sound in enclosed space are higher than those in open space and their difference increases with the rise of propagation distance. The results of the duration of PDE sound indicate that the A duration of PDE sound in enclosed space is higher than that in open space except at measuring points located at 2-m and 5-m while the B duration is higher at each of all measuring points. Results show that the enclosed space has a great influence on the acoustic characteristic of PDE sound. This research is helpful in performing PDE experiments in enclosed laboratories to prevent the PDE sound from affecting the safety of laboratory environment, equipment, and staffs. [ABSTRACT FROM AUTHOR]