Research Institute of Geology and Mineral Resources

Hanoi, Vietnam

Research Institute of Geology and Mineral Resources

Hanoi, Vietnam
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Hieu P.T.,Hefei University of Technology | Hieu P.T.,CAS Institute of Geology and Geophysics | Chen F.,Hefei University of Technology | Me L.T.,Hanoi University of Mining and Geology | And 3 more authors.
International Geology Review | Year: 2012

The location of the suture zone between the South China and Indochina blocks in northwest Vietnam has been under debate for decades. Generally, the boundary between these blocks has been placed along (1) the Ailaoshan-Red River zone or (2) the Song Ma zone. The Sin Quyen Formation, lying between these zones, was previously regarded as a Palaeo-and Mesoproterozoic sequence. It comprises its provenance and tectonic affinity. We analysed detrital zircons from two paragneisses and one migmatite of the Sin Quyen Formation employing laser ablation inductively coupled plasma mass spectrometry U-Pb dating techniques. U-Pb ages of these zircons show three main periods of zircon formation: ∼2.7-3.0, ∼2.2-2.5, and ∼1.8 Ga, suggesting that Sin Quyen rocks were mainly derived from Palaeoproterozoic and Archaean basement units. Inasmuch as the South China basement comprises rocks of similar ages, we conclude that the Sin Quyen Formation belongs to that block. Our new data strengthen the view that the suture between the South China and Indochina blocks is located within the Song Ma zone. In addition, zircons with U-Pb ages >3.0 thousand million years represent the oldest minerals reported in northwest Vietnam so far, indicating the existence of Mesoarchaean crustal remnants in this region. © 2012 Taylor & Francis.

Nakano N.,Kyushu University | Osanai Y.,Kyushu University | Sajeev K.,Indian Institute of Science | Hayasaka Y.,Hiroshima University | And 4 more authors.
Journal of Metamorphic Geology | Year: 2010

The first finding of low-temperature eclogites from the Indochina region is reported. The eclogites occur along the Song Ma Suture zone in northern Vietnam, which is widely regarded as the boundary between the South China and Indochina cratons. The major lithology of the area is pelitic schist that contains garnet and phengite with or without biotite, chloritoid, staurolite and kyanite, and which encloses blocks and lenses of eclogite and amphibolite. The eclogites commonly consist of garnet, omphacite, phengite, rutile, quartz and/or epidote with secondary barroisite. Omphacite is commonly surrounded by a symplectite of Na-poor omphacite and Na-rich plagioclase. In highly retrograded domains, diopside + tremolite + plagioclase symplectites replace the primary phases. Estimated peak-pressure metamorphic conditions based on isochemical phase diagrams for the eclogites are 2.1-2.2 GPa and 600-620 °C, even though thermobarometric results yield higher pressure and temperature conditions (2.6-2.8 GPa and 620-680 °C). The eclogites underwent a clockwise P-T trajectory with a post-peak-pressure increase of temperature to a maximum of >750 °C at 1.7 GPa and a subsequent cooling during decompression to 650 °C and 1.3 GPa, which was followed by additional cooling before close-to-isothermal decompression to ∼530 °C at 0.5 GPa. The surrounding pelitic schist (garnet-chloritoid-phengite) records similar metamorphic conditions (580-600 °C at 1.9-2.3 GPa) and a monazite chemical age of 243 ± 4 Ma. A few monazite inclusions within garnet and the cores of some zoned monazite in garnet-phengite schist record an older thermal event (424 ± 15 Ma). The present results indicate that the Indochina craton was deeply (>70 km) subducted beneath the South China craton in the Triassic. The Silurian cores of monazite grains may relate to an older non-collisional event in the Indochina craton. © 2009 Blackwell Publishing Ltd.

Nguyen T.V.,Clausthal University of Technology | Weller A.,Clausthal University of Technology | Tang D.N.,Research Institute of Geology and Mineral Resources
Near Surface 2010 - 16th European Meeting of Environmental and Engineering Geophysics | Year: 2010

This paper presents new results of geophysical measurement in coastal area of Nam Dinh province. Resistivity imaging was carried out to map the resistivity distribution along a 2 km long profile. Two boreholes were drilled on the same profile. The resistivity of 26 soil samples was determined in laboratory. A comparison between the resistivity of well logging, resistivity imaging and samples shows a good agreement. The resulting resistivity section provides promising 2D image of geological structures. Regarding the resistivity values, fresh water bearing areas can be identified in the Holocene and Pleistocene aquifers. Resistivity imaging has proved to be an appropriate tool to investigate hydrogeological structures in coastal areas.

Yang Y.Z.,Hefei University of Technology | Long Q.,Hefei University of Technology | Hu H.T.,Hefei University of Technology | Hieu P.T.,Hanoi University of Mining and Geology | And 2 more authors.
Acta Petrologica Sinica | Year: 2013

Cenozoic lamprophyre dykes exposed in the Laichau area of northwestern Vietnam hold geological significances for understanding geochemical features and evolution of deep lithosphere in the eastern part of the Tethyan orogenic belt. This study reports geochemical and Sr-Nd-Pb radiogenic isotopic composition of lamprophyre dykes from the Laichau area and discuss their petrogenesis and geological implications. Lamprophyre samples reported here are of calc-alkaline and potassic to ultra-potassic characteristics in major element contents. When compared with relating rocks in the neighbouring areas, lamprophyre dykes from the Laichau area are similar in geochemical composition with alkalic rocks in the Ailaoshan fault zone, but considerable different from volcanic rocks exposed in Hainan and southern Vietnam. The Laichau lamprophyre dykes show enriched isotopic feature of high 87Sr/86Sr ratios, low 143Nd/144 Nd ratios and high radiogenic Pb isotopic composition. Evidence of trace element contents from these lamprophyre samples indicates that the magma source of the lamprophyre dykes likely suffered metasomatic processes or input of sedimentary components before partial melting of the mantle. Low 208Pb */Pb * ratios of lamprophyre samples imply that enrichment of the mantle source producing the Laichau lamprophyre dykes took place recently, probably related to amalgamation of the Indochina block to the Yangtze block during the Late Paleozoic to Early Mesozoic.

Shigeta Y.,National Museum of Nature and Science | Komatsu T.,Kumamoto University | Huu N.D.,Research Institute of Geology and Mineral Resources | Huyen D.T.,Research Institute of Geology and Mineral Resources | Iwakiri N.,Kumamoto University
Paleontological Research | Year: 2010

The discovery of Balatonites sp. in the lower part of the Quy Lang Formation in the Lang Nuoc area, Thanh Hoa Province, Central Vietnam establishes that this portion of the formation is of late Middle Anisian age. This ammonoid's cooccurrence with Costatoria goldfussi mansuyi and Trigonodus tonkinensis suggests that this widely distributed bivalve assemblage in Asian shallow marine facies is at least partly of late Middle Anisian age, and its discovery may provide an important key for the establishment of a precise biostratigraphic framework for the Middle Triassic of Asia. © by the Palaeontological Society of Japan.

Maekawa T.,Kumamoto University | Komatsu T.,Kumamoto University | Shigeta Y.,National Museum of Nature and Science | Huyen D.T.,Research Institute of Geology and Mineral Resources | Tien D.C.,Research Institute of Geology and Mineral Resources
Paleontological Research | Year: 2015

The Early Triassic conodonts Eurygnathodus costatus Staesche, E. hamadai (Koike), Neospathodus cristagalli (Huckriede), and Ns. pakistanensis Sweet are newly reported from the upper part of the Lang Son Formation in Lang Son City, northeastern Vietnam. This association and particularly E. costatus and E. hamadai indicate the lower Smithian (lower lower Olenekian). Thus, the geological age of the upper part of the Lang Son Formation ranges from Induan to early Olenekian, and the stage boundary lies within the upper part of the formation. © by the Palaeontological Society of Japan.

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