Nakano N.,Kyushu University |
Osanai Y.,Kyushu University |
Van Nam N.,Vietnam Institute of Geosciences and Mineral Resources
Journal of Mineralogical and Petrological Sciences | Year: 2016
We report first finding of low-temperature eclogite-facies metamorphism from the Red River shear zone in northern Vietnam that has been known as the Paleogene high-temperature metamorphic belt. The rock is extremely aluminous (50.13 wt% Al2O3) and oxidized [Fe3+/(Fe3+ + Fe2+) = 0.89] emery-type rock. Its composition is also characterized by very low SiO2, CaO, and Na2O with high concentrations in high field strength elements, suggesting that the protolith is lateritic bauxite. The analyzed rock is composed mainly of porphyroblastic titanomaghemite, kyanite, allanite, and chloritoid with abundant fine-grained corundum in the matrix. The mineral paragenesis and phase equilibria modeling suggest that the aluminous rock underwent a clockwise pressure-temperature trajectory with the peak metamorphic condition corresponding to low-temperature eclogite- facies approximately 520-550 °C at 1.2-1.5 GPa. Monazite U-Th-Pb dating constrains the timing of the metamorphism to be older than 214 Ma. Our results require two geological events; 1) tropical weathering and bauxitization on the erosional surface, and 2) pre-Late Triassic subduction of supracrustal materials most likely during the Permo-Triassic collisional events in East and Southeast Asia. Our study provides the first evidence for the subduction of supra-continental crustal materials up to 40-50 km depth during the collision between the Indochina and South China blocks.
Hung L.Q.,Vietnam Institute of Geosciences and Mineral Resources |
van N.T.H.,Vietnam Institute of Geosciences and Mineral Resources |
Duc D.M.,Vietnam National University, Hanoi |
Ha L.T.C.,Central Vietnam Institute for Water Resources |
And 3 more authors.
Landslides | Year: 2015
The purpose of this study is to carry out a regional landslide susceptibility mapping for the upper Lo River catchment (ULRC) in northern Vietnam, where data on spatial distribution of historic landslides and environmental factors are very limited. Two methods, analytical hierarchy process (AHP) and weighted linear combination (WLC), were combined to create a landslide susceptibility map for the ULRC study area. In the first step, 216 existing landslides that occurred in the study area were mapped in field surveys in 2010 and 2011. A spatial database including six landslide factor maps related to elevation, slope gradient, drainage density, fault density, types of weathering crust, and types of land cover was constructed from various sources. To determine the relative importance of the six landslide factors and their classes within the landslide susceptibility analysis, weights of each factor and each factor class were defined by expert knowledge using the AHP method. To compute the landslide susceptibility, defined weights were assigned to all factor maps in raster format using the WLC method. The result is a landslide susceptibility index that is reclassified into four susceptible zones to produce a landslide susceptibility map. Finally, the landslide susceptibility zonation map was overlaid with the observed landslides in the inventory map to validate the produced map as well as the overall methodology. The results are in accordance with the occurrences of the observed landslides, in which 47.69 % of observed landslides are located in the two most susceptible zones (very-high-susceptibility zone and high-susceptibility zone) that cover 40.96 % of the total area. As the approach is able to integrate expert knowledge in the weighting of the input factors, the actual study shows that the combination of AHP and WLC methods is suitable for landslide susceptibility mapping in large mountainous areas at medium scales, particularly for areas lacking detailed input data. © 2015 Springer-Verlag Berlin Heidelberg
Le H.T.,Vietnam National University, Hanoi |
Ngo H.T.T.,Vietnam Institute of Geosciences and Mineral Resources
Toxicological and Environmental Chemistry | Year: 2013
The seasonal variations of Cd, Pb, and Cu in the water, sediments, and freshwater fish (Hypophthalmichthys molitrix, Cirrhinus molitorella, and Oreochromis mossambicus) of four lakes in Hanoi, Vietnam, were investigated. Samples for analysis were taken four times from April 2010 to March 2011. The levels in water were lower than the Vietnamese standards, except for Pb, but they were all much higher than the Canadian standards for protection of aquatic life; in the sediments, they were higher than world average levels. Bioaccumulation of the three metals in fish was site-dependent and species-dependent, but correlations of their levels in fish to those in water and sediments were weak. Levels of Pb in fish exceeded those of the UK and the WHO standards, and the recommended values of Vietnam for human consumption. Overall, the results show that the lakes are polluted with these metals, and consumption of high quantities of fish from them may be problematic. The outcome of this research helps to establish background data for future monitoring. © 2014 Taylor & Francis.
Hieu P.T.,Hefei University of Technology |
Hieu P.T.,CAS Institute of Geology and Geophysics |
Chen F.-K.,Hefei University of Technology |
Thuy N.T.B.,Vietnam Institute of Geosciences and Mineral Resources |
And 2 more authors.
Journal of Geodynamics | Year: 2013
The late Permian granitoids exposed in the Phan Si Pan zone of northwestern Vietnam consist mainly of the Ye Yen Sun metaluminous granites and the Nam Xe-Tam Duong peralkaline granites. Laser ablation inductively coupled plasma mass spectrometry U-Pb zircon analysis reveals that both the granite suites were emplaced from 253Ma to 251Ma. They have a distinctive A-type geochemistry of high 10,000×Ga/Al ratios of 3.0-5.7 and are also characterized by elevated contents of high field strength elements, A/CNK values of 0.85-1.58, negative Eu-anomalies. Magmatic zircons from the granitoids exhibit positive initial eHf values ranging from 6.4 to 15.9 and yield single-stage depleted mantle Hf model ages of 257-663Ma. This Hf isotopic feature implies significant contribution of juvenile mantle material to the magmas of the spatially and temporally associated Ye Yen Sun metaluminous and Nam Xe-Tam Duong peralkaline granites. © 2012 Elsevier Ltd.
Hieu P.T.,University of Science |
Yang Y.-Z.,Hefei University of Technology |
Binh D.Q.,Vietnam Institute of Geosciences and Mineral Resources |
Nguyen T.B.T.,Vietnam Institute of Geosciences and Mineral Resources |
And 2 more authors.
International Geology Review | Year: 2015
The Hai Van granitoid complex constitutes an important part of the Indosinian batholith of the northern Kontum massif in central Vietnam. The Kontum massif is a key region for understanding the palaeo-Tethyan accretionary history and the crustal evolution of the Indochina terrane. In this study, zircon U-Pb ages and geochemical data on the Hai Van complex are reported to shed more light on these geological processes. Zircon U-Pb isotopic analyses of six representative samples by the LA-ICP-MS technique show that granitoids from this complex crystallized between 242 and 224 Ma, indicating a prolonged period of magmatism in a late orogenic stage. Rocks from the Hai Van complex have S-type geochemical characteristics with high SiO2, Na2O + K2O, and Zr contents as well as typical S-type minerals such as cordierite and muscovite. Trace elements of the samples are depleted in Ba, Nb, P, Sr, and Ti and enriched in Rb, K, Th, U, and Pb. Negative Eu-anomalies indicate feldspar fractionation during magma crystallization. The Hai Van granitoids exhibit Nd-Hf isotopic features similar to Proterozoic rocks exposed in South China, with low initial εHf and initial εNd values and two-stage Hf model ages of 1.9-1.7 Ga. It is suggested that during the palaeo-Tethyan orogeny, central Vietnam experienced strong early Mesozoic magmatism that originated from partial melting of crustal material similar in composition to the basement of the South China block. © 2015 © 2015 Taylor & Francis.
Tien Bui D.,Telemark University College |
Ho T.-C.,Vietnam Institute of Geosciences and Mineral Resources |
Pradhan B.,University Putra Malaysia |
Pradhan B.,Sejong University |
And 3 more authors.
Environmental Earth Sciences | Year: 2016
The main objective of this study is to propose and verify a novel ensemble methodology that could improve prediction performances of landslide susceptibility models. The proposed methodology is based on the functional tree classifier and three current state-of-the art machine learning ensemble frameworks, Bagging, AdaBoost, and MultiBoost. According to current literature, these methods have been rarely used for the modeling of rainfall-induced landslides. The corridor of the National Road 32 (Vietnam) was selected as a case study. In the first stage, the landslide inventory map with 262 landslide polygons that occurred during the last 20 years was constructed and then was randomly partitioned into a ratio of 70/30 for training and validating the models. Second, ten landslide conditioning factors were prepared such as slope, aspect, relief amplitude, topographic wetness index, topographic shape, distance to roads, distance to rivers, distance to faults, lithology, and rainfall. The model performance was assessed and compared using the receiver operating characteristic and statistical evaluation measures. Overall, the FT with Bagging model has the highest prediction capability (AUC = 0.917), followed by the FT with MultiBoost model (AUC = 0.910), the FT model (AUC = 0.898), and the FT with AdaBoost model (AUC = 0.882). Compared with those derived from popular methods such as J48 decision trees and artificial neural networks, the performance of the FT with Bagging model is better. Therefore, it can be concluded that the FT with Bagging is promising and could be used as an alternative in landslide susceptibility assessment. The result in this study is useful for land use planning and decision making in landslide prone areas. © 2016, Springer-Verlag Berlin Heidelberg.
Ho H.H.,Catholic University of Leuven |
Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources |
Swennen R.,Catholic University of Leuven |
Cappuyns V.,Catholic University of Leuven |
And 5 more authors.
Soil and Sediment Contamination | Year: 2013
The Cam River mouth (Haiphong Province) is one of the main river mouths of the Red River System, which is one of the most important water resources in Northern Vietnam. Over the past 50 years, the strong socio-economic development in the area has caused a considerable contamination with heavy metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) and arsenic. In this study, the vertical and horizontal distributions of heavy metals and arsenic in sediments from the Cam River mouth were investigated. In addition, the history, origin, and degree of contamination were assessed. Normalized (with respect to Al) heavy metal and arsenic concentrations in sediment cores and absolute dates obtained from the 137Cs analysis were used to reconstruct the pollution history of the river mouth. As, Cu, Mn, Pb, and Zn concentrations increase rapidly by approximately two times or more from 1954 to 1975, and then remain nearly unchanged from 1975 until 2008, whereas Co, Cr, and Ni concentrations slightly increase from 1954 until 2008. In addition, background values for heavy metals and arsenic have also been determined with regard to the period before 1954. In the study area, Co, Cr, Cu, Ni, Mn, and Zn are evaluated as minorly enriched, whereas As and Pb are classified as moderately enriched. Generally, the anthropogenic activities in the Haiphong harbor and industrial zone locally contribute to the contamination by heavy metals and arsenic in the Cam River mouth. © 2013 Copyright Taylor and Francis Group, LLC.
Thanh L.N.,Free University of Brussels |
Thanh L.N.,Vietnam Institute of Geosciences and Mineral Resources |
de Smedt F.,Free University of Brussels
Environmental Earth Sciences | Year: 2012
A Luoi is a Vietnamese-Laotian border district situated in the western part of Thua Thien Hue province, central Vietnam, where landslides occur frequently and seriously affect local living conditions. This study focuses on the spatial analysis of landslide susceptibility in this 263-km 2 area. To analyze landslide manifestation in the study area, causative factor maps are derived of slope angle, weathering, land use, geomorphology, fault density, geology, drainage distance, elevation, and precipitation. The analytical hierarchical process approach is used to combine these maps for landslide susceptibility mapping. A landslide susceptibility zonation map with four landslide susceptibility classes, i. e. low, moderate, high, and very high susceptibility for landsliding, is derived based on the correspondence with an inventory of observed landslides. The final map indicates that about 37% of the area is very highly susceptible for landsliding and about 22% is highly susceptible, which means that more than half of the area should be considered prone to landsliding. © 2011 Springer-Verlag.
Prosorhynchus Odhner, 1905 (Digenea: Bucephalidae) from the orange-spotted grouper Epinephelus coioides (Hamilton, 1822) (Epinephelidae), including Prosorhynchus tonkinensis n sp, from the Gulf of Tonkin, Vietnam
PubMed | Natural History Museum in London, Justus Liebig University, University of Rostock, Research Institute For Aquaculture No 1 and Vietnam Institute of Geosciences and Mineral Resources
Type: Journal Article | Journal: Zootaxa | Year: 2016
A total of 169 specimens of the orange-spotted grouper Epinephelus coioides (Hamilton) were collected from fishermen and marine fish farms in the Gulf of Tonkin, Vietnam. Five different species of Prosorhynchus Odhner, 1905 were recorded, including P. tonkinensis n. sp. The new species differs from all other Prosorhynchus species in the presence of an indented posterior extremity. It can be distinguished from the most closely related P. atlanticus Manter, 1940 and P. crucibulum Rudolphi, 1819 by the extension of the uterus always to the level of the ovary, the width and premouth distance in the former, and the arched vitellarium and smaller egg size in the latter, and a different host and geographical region. Prosorhynchus sp. A (not fully identified in this study) has been earlier reported from E. coioides from New Caledonia (see Prosorhynchus sp. B of Bray and Justine, 2013), P. luzonicus Velasquez, 1959 is reported throughout South-East Asia, and Prosorhynchus sp. B (no further identification possible based on a single specimen in this study) and P. maternus Bray & Justine, 2006 are reported for the first time from Vietnam. The present study demonstrates a close relationship of the Prosorhynchus species composition in Vietnam with the Indo-Australian region, warranting further comparative studies among the different epinephelids.
Komatsu T.,Kumamoto University |
Huyen D.T.,Vietnam Institute of Geosciences and Mineral Resources |
Huu N.D.,Vietnam Institute of Geosciences and Mineral Resources
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010
In North Vietnam, Lower to Middle Triassic storm- and wave-dominated shelf deposits are widely exposed and yield abundant Tethyan bivalves indicating recovery and diversification following the end-Permian mass extinction. We reconstructed the habitats of characteristic bivalve species on the basis of shell preservation and mode of occurrence. Bivalves that diversified in the Middle Triassic Anisian to Ladinian Stages in the Na Khuat Formation, An Chau Basin, can be divided into four fossil assemblages: (1) an autochthonous to parautochthonous Costatoria goldfussi mansuyi and Trigonodus tonkinensis assemblage (sandy bottom of inner shelf facies); (2 and 3) a parautochthonous to allochthonous Costatoria goldfussi mansuyi and Pteria sturi assemblage, and a Costatoria paucicostata and Hoernesia angusta assemblage (muddy bottom of inner to outer shelf facies); and (4) a typical allochthonous Costatoria ngeanensis and Leptochondria albertii assemblage. These assemblages are characterized by a diversity of species of Costatoria and Trigonodus, and by several genera of twisted Bakevellidae, such as Hoernesia, Langsonella, and Lilangina. These bivalve assemblages are composed of shallow-infaunal and semi-infaunal burrowers and epifaunal species, though in Vietnam the Lower Triassic Induan to early Olenekian bivalves are dominated by epifauna. In the eastern part of the Tethys, infaunal bivalves show a remarkable delay in recovering from the end-Permian mass extinction compared to epifaunal bivalves. © 2010 Elsevier B.V. All rights reserved.