Nguyen Hoang

Major, trace element, and isotopic compositions of Vietnamese basalts: Interaction of hydrous EM1-rich asthenosphere with thinned Eurasian lithosphere

Abstract Intraplate magmatism affected much of Indochina following the mid-Miocene cessation of South China Sea opening. Thick basalt plateaus formed on accreted terrains of varying age as extensional fractures were reactivated following the Indo-Eurasian collision. The basalts are part of a diffuse igneous province affecting much of eastern and southeastern Asia and western Pacific marginal basins. Most Indochina basalt centers comprise two eruptive episodes, an early (lower) series of high-Si0 2, low-FeO * quartz and olivine tholeiites, tapping a relatively-refractory, lithospheric mantle-type source, and a later (upper) series of low-SiO 2, high-FeO * olivine tholeiites, alkali basalts, and basanites, tapping a fertile, asthenospheric source. This pattern is observed elsewhere in the region (e.g., Hainan Island) and resembles several continental flood basalt provinces. While some crustal contamination is suggested, incompatible trace element and strontium, neodymium, and lead isotopic compositions reflect secular changes from the inferred lithospheric to asthenospheric reservoirs. Lower Series basalts reflect hybrids of 206Pb/ 204Pb-rich EM2 and N-MORB reservoirs, with high K 2O/P 2O 5 and low Rb/Sr and Ba/Nb ratios, consistent with the involvement of lithospheric mantle. In contrast, Upper Series basalts show lower K 2O/P 2O 5 and higher Rb/Sr and Ba/Nb ratios and reflect hybrids of 206Pb/ 204Pb-poor EM1 and N-MORB sources. These resemble anomalous (A) -MORB compositions that are typical of eastern/southeastern Asian and western Pacific marginal basin asthenosphere. Despite its resemblance to Indian Ocean (I-) MORB, A-MORB “plum-pudding” asthenosphere may be explained in terms of an endogenous Asian model whereby EM1-rich subcratonic lithosphere was entrained by asthenosphere extruded by the Indo-Eurasian collision. This model is consistent with the restriction of diffuse regional magmatism to the late Cenozoic (i.e., following tectonic extrusion), evidence for shallow, thermally-anomalous mantle, and absence of A-MORB signatures from the pre-extrusion continental mantle.

Regulation of dendritic cell function by insulin/IGF-1/PI3K/Akt signaling through klotho expression

Abstract Insulin or insulin-like growth factor 1 (IGF-1) promotes the activation of phosphoinositide 3 kinase (PI3K)/Akt signaling in immune cells including dendritic cells (DCs), the most potent professional antigen-presenting cells for naive T cells. Klotho, an anti-aging protein, participates in the regulation of the PI3K/Akt signaling, thus the Ca2+-dependent migration is reduced in klotho-deficient DCs. The present study explored the effects of insulin/IGF-1 on DC function through klotho expression. To this end, the mouse bone marrow cells were isolated and cultured with GM-CSF to attain bone marrow-derived DCs (BMDCs). Cells were treated with insulin or IGF-1 and followed by stimulating with lipopolysaccharides (LPS). Tumor necrosis factor (TNF)-α formation was examined by enzyme-linked immunosorbent assay (ELISA). Phagocytosis was analyzed by FITC-dextran uptake assay. The expression of klotho was determined by quantitative PCR, immunoprecipitation and western blotting. As a result, treatment of the cells with insulin/IGF-1 resulted in reducing the klotho expression as well as LPS-stimulated TNF-α release and increasing the FITC-dextran uptake but unaltering reactive oxygen species (ROS) production in BMDCs. The effects were abolished by using pharmacological inhibition of PI3K/Akt with LY294002 and paralleled by transfecting DCs with klotho siRNA. In conclusion, the regulation of klotho sensitive DC function by IGF-1 or insulin is mediated through PI3K/Akt signaling pathway in BMDCs.

Geochemistry of late miocene-pleistocene basalts in the Phu Quy island area (East Vietnam Sea): Implication for mantle source feature and melt generation

The chemical compositions of late Miocene Pleistocene basalts in Phu Quy island defines two major geochemical groups that reflect the formation and development of the island. The early low alkaline, TiO2 and P2O5, and high SiO2 group, comprising olivine and tholeiitic basalts, forms the base of the island. The later high alkaline, TiO2, and P2O5, and low SiO2 group, produced by central-type volcanic eruptions consisting of alkaline olivine and olivine basalts, overlies the early eruptive group. Crustal contamination may be expressed by the positive correlation between Ba/Nb and SiO2, which are higher in early eruptive basalts, possibly reflecting the involvement of crustal material, either in the source region or interaction of the melt on the way to the surface. However, negative relationship between Ba and SiO2, and positive correlation between Nb/Y and Zr/Y observed for two basaltic series may reflect the effect of melting pressures and degrees of partial melting. Methods of calculating the primitive basaltic melts based on the principle of olivine incremental additions to the basalt until the composition is equilibrated with the residual olivine at Fo89-90 may be used. The computed results show that the early basalts were generated under pressures of about 18-20 Kb (ca. 55-60 km) and the later basalts were formed in the pressure range of 20 to 25 Kb (corresponding to the depths about 60 to 75 km). The close range of melting pressures suggests decompression polybaric melting of a mantle source, which allows for mixing of various melt portions, resulting in the formation of geochemically linear relationship. It has been demonstrated that the post-opening volcanism was unrelated to an important tectonic phase and that the calculated extension factor () for the regional major extension fault systems is not significant (ca. 1.3) to trigger mantle melting. Therefore, the infiltration of asthenospheric flows resulting from the Neo-Tethys closure following the collision between India and Eurasia in the late Tertiary, may not only raise the mantle temperature leading to the melting but also appear to be the major driving force of marginal sea opening in the western Pacific, including the East Vietnam Sea.

Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region

Study of petrological and geochemical characteristics of mantle peridotite xenoliths in Pliocene alkaline basalt in Nghia Dan (West Nghe An) was carried out. Rock-forming clinopyroxenes, the major trace element containers, were separated from the xenoliths to analyze for major, trace element and Sr-Nd isotopic compositions. The data were interpreted for source geochemical characteristics and geodynamic processes of the lithospheric mantle beneath the region. The peridotite xenoliths being mostly spinel-lherzolites in composition, are residual entities having been produced following partial melting events of ultramafic rocks in the asthenosphere. They are depleted in trace element abundance and Sr-Nd isotopic composition. Some are even more depleted as compared to mid-ocean ridge mantle xenoliths. Modelled calculation based on trace element abundances and their corresponding solid/liquid distribution coefficients showed that the Nghia Dan mantle xenoliths may be produced of melting degrees from 8 to 12%. Applying various methods for two-pyroxene temperaturepressure estimates, the Nghia Dan mantle xenoliths show ranges of crystallization temperature and pressure, respectively, of 1010-1044°C and 13-14.2 kbar, roughly about 43km. A geotherm constructed for the mantle xenoliths showed a higher geothermal gradient as compared to that of in the western Highlands (Vietnam) and a conductive model, implying a thermal perturbation under the region. The calculated Sm-Nd model ages for the clinopyroxenes yielded 127 and 122 Ma. If the age is meaningful it suggests that there was a major geodynamic process occurred beneath Western Nghe An in the middleEarly Cretaceous that was large enough to cause perturbation in the evolutional trend of the Sm-Nd isotopic system.

GEOCHEMISTRY AND PETROGENESIS OF VOLCANIC ROCKS AND THEIR MANTLE SOURCE IN THE EAST VIETNAM SEA AND ADJACENT REGIONS IN THE CENOZOIC

The East Vietnam Sea is one of the largest marginal basins in western Pacific Ocenan, formed by breaking of continental margin in the Late Mesozoic. Geochemical data of the Miocene - Pleistocene bazanic samples collected in the East Sea and neighboring areas show two major eruption trends that reflect the formation and development of the region. The early eruption event is characterized by low alkaline, TiO2, Na2O, K2O and P2O5, and high SiO2 group, comprising olivine and tholeiitic bazans. The later eruption demonstrates high alkaline, TiO2, Na2O, K2O and P2O5, and low SiO2 group, mainly generated by central-type volcanic eruptions, consisting of alkaline olivine and olivine bazans. Distinctive geochemistry of the volcanic rocks within the East Vietnam Sea and adjacent areas is illustrated by wide range of Magnesium index (Mg#= 35-75). At the values of Mg#>65, the relation between Mg# and major oxides is unclear. In contrast, Mg# 65 (Olivine differentiation) the isotope ratios start changing. The primitive components are computed based on the principle of olivine compensation. The computed results show that the critical pressure for Tholeiite melting was estimated from ~11.97-20.33 Kb (ca. 30 - 60 km deep) and the Alkaline melting pressure varies from ~16.87-34.93 Kb (corresponding to the depths of ~60 km to 100 km). The continuous range of melting pressures suggests two trends of tholeiitic and alkaline eruptions occurr at various depths in the same magmatic source. Hight temperature and melting pressure of the primitive magma are dependent on partial melting pressure. Possibly, this process was triggered by the asthenosphere intrusion resulted from the closure of the Neo-Tethys following the India - Eurasia collision. This event has not only made the mantle hotter and easily melted but also triggered the opening of the marginal seas, including the East Vietnam Sea.

Complete human mtDNA genome sequences from Vietnam and the phylogeography of Mainland Southeast Asia

Vietnam is an important crossroads within Mainland Southeast Asia (MSEA) and a gateway to Island Southeast Asia, and as such exhibits high levels of ethnolinguistic diversity. However, comparatively few studies have been undertaken of the genetic diversity of Vietnamese populations. In order to gain comprehensive insights into MSEA mtDNA phylogeography, we sequenced 609 complete mtDNA genomes from individuals belonging to five language families (Austroasiatic, Tai-Kadai, Hmong-Mien, Sino-Tibetan and Austronesian) and analyzed them in comparison with sequences from other MSEA countries and Taiwan. Within Vietnam, we identified 399 haplotypes belonging to 135 haplogroups; among the five language families, the sequences from Austronesian groups differ the most from the other groups. Phylogenetic analysis revealed 111 novel Vietnamese mtDNA lineages. Bayesian estimates of coalescence times and associated 95% HPD for these show a peak of mtDNA diversification around 2.5–3 kya, which coincides with the Dong Son culture, and thus may be associated with the agriculturally-driven expansion of this culture. Networks of major MSEA haplogroups emphasize the overall distinctiveness of sequences from Taiwan, in keeping with previous studies that suggested at most a minor impact of the Austronesian expansion from Taiwan on MSEA. We also see evidence for population expansions across MSEA geographic regions and language families.

Whole genome sequencing and mutation rate analysis of trios with paternal dioxin exposure

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD) or dioxin, is commonly considered the most toxic man‐made substance. Dioxin exposure impacts human health and diseases, birth defects and teratogenesis were frequently observed in children of persons who have been exposed to dioxin. However, the impact of dioxin on human mutation rate in trios has not yet been elucidated at the whole genome level. To identify and characterize the genetic alterations in the individuals exposed to dioxin, we performed whole genome sequencing (WGS) of nine Vietnamese trios whose fathers were exposed to dioxin. In total, 846 de novo point mutations, 26 de novo insertions and deletions, 4 de novo structural variations, and 1 de novo copy number variation were identified. The number of point mutations and dioxin concentrations were positively correlated (P‐value < 0.05). Considering the substitution pattern, the number of A > T/T > A mutation and the dioxin concentration was positively correlated (P‐value < 0.05). Our analysis also identified one possible disease‐related mutation in LAMA5 in one trio. These findings suggested that dioxin exposure might affect father genomes of trios leading to de novo mutations in their children. Further analysis with larger sample sizes would be required to better clarify mutation rates and substitution patterns in trios caused by dioxin.

Oleanane-type Saponins from Glochidion hirsutum and Their Cytotoxic Activities

Five new oleanane‐type saponins, hirsutosides A – E, were isolated from the leaves of Glochidion hirsutum (Roxb.) Voigt. Their structures were elucidated as 21β‐benzoyloxy‐3β,16β,23,28‐tetrahydroxyolean‐12‐ene 3‐O‐β‐d‐glucopyranoside (1), 21β‐benzoyloxy‐3β,16β,23,28‐tetrahydroxyolean‐12‐ene 3‐O‐β‐d‐glucopyranosyl‐(1 → 3)‐β‐d‐glucopyranoside (2), 21β‐benzoyloxy‐3β,16β,23,28‐tetrahydroxyolean‐12‐ene 3‐O‐6‐acetyl‐[β‐d‐glucopyranosyl‐(1 → 3)]‐β‐d‐glucopyranoside (3), 21β‐benzoyloxy‐3β,16β,23,28‐tetrahydroxyolean‐12‐ene 3‐O‐β‐d‐glucopyranosyl‐(1 → 3)‐〈‐l‐arabinopyranoside (4), and 21β‐benzoyloxy‐3β,16β,23‐trihydroxyolean‐12‐ene‐28‐al 3‐O‐β‐d‐glucopyranosyl‐(1 → 3)‐α‐l‐arabinopyranoside (5). All isolated compounds were evaluated for cytotoxic activities on four human cancer cell lines, HepG‐2, A‐549, MCF‐7, and SW‐626 using the SRB assay. Compounds 1, 2, 4, and 5 showed significant cytotoxic activities against all human cancer cell lines with IC50 values ranging from 3.4 to 10.2 μm. Compound 3 containing acetyl group at glc C(6″) exhibited weak cytotoxic activity with IC50 values ranging from 47.0 to 54.4 μm.

Petrography and geochemistry of Permian basalts of the Cam Thuy formation and their relation to Song Da and Emeishan magmatic rocks

Cam Thuy Permian basalts consisting of thick lava flows and pyroclastic layers appear along both sides of the Song Ma fault zone in Thanh Hoa and in Son La and Ninh Binh provinces, NW Vietnam. The magmatism has been thought to have genetic relationship with Permian volcanism in the Song Da rift zone, which is believed to be part of the Emeishan large igneous province, having been extruded along the Red River shear zone following Paleogene India-Eurasian collision. A set of Cam Thuy volcanic samples including olivine and alkaline basalts was collected in the Lam Son area (Tho Xuan, Thanh Hoa province) to analyze for geochemical major, trace element and Sr-Nd-Pb isotopic composition. The Cam Thuy basalts are high-TiO2, CaO, FeO*, moderate MgO and SiO2 that plot between the Song Da and Emeishan highand low-Ti basalt distribution fields and closely overlap that of Song Da’s high-Ti field. The primitive mantle and chondrite normalized trace element patterns of Cam Thuy basalts are essentially enriched oceanic island basalt (OIB)-like; this feature, together with crustal contamination-free, chondritic Sr, Nd and Pb initial (255Ma) isotopic composition are certainly of asthenospheric origin. These geochemical and isotopic characteristics are closely analogous to those features observed for the Song Da high-Ti basalts, suggesting similarity in their source of origin. Nevertheless, while the Song Da (and Emeishan) magmatism is signified by the presence of both highand low-Ti basalts, with the latter being derived from heterogeneous and partially crustal-material contaminated sources in the lithospheric mantle, this low-Ti volcanic rock type has yet to be discovered in the Cam Thuy formation.

Magma source feature and eruption age of volcanic rocks in the Tram Tau district, Tu Le Basin

A set of samples including porphyritic rhyolite, rhyo-trachyte, trachyte and basalt was collected in the Tram Tau district, Tu Le Mesozoic Basin, in NW Viet Nam for analysis for major, trace, elemental and Rb-Sr and Sm-Nd isotopic compositions. The volcanic rocks are alkaline and highly enriched in trace elements including rare earth elements (REEs). However, primitive mantle and chondrite trace element normalized patterns expose strong negative anomalies for Ba, Sr, Eu and Ti, possibly reflecting fractional crystallization of plagioclase (for Sr and Eu), pyroxene, and especially amphibole (for Ba and Ti). The measured Sr/Sr isotopic ratios, varying between 0.8142 and 0.75283, are plotted against the corresponding Rb/Sr forming an isochron that provides an age of 157± 2.9 Ma with an initial Sr/Sr ratio of 0.708, corresponding to late Jurassic early Cretaceous (J3-K1) in agreement with previously reported data. The corresponding Nd isotopic compositions expressed as Nd (157Ma) vary from -8,27 to 2.32 and the Nd model ages are Mesoproterozoic, ranging from 1 to 1.3 Ga. This highly enriched magma was postulated to have formed by mixing of a depleted mantle and Mesoproterozoic crustal rocks (for example, granite) following a continental extension event. Mixing between crustal rocks having strontium isotopic ratios of 0.715 and 0.730 and a depleted mantle with Sr/Sr ratio of 0.703 would occur, respectively, at 3÷4% and 2÷5% to generate the observed strontium isotopic ratios in the Tram Tau volcanic rocks.