越南东北部Cat Ba岛泥盆系-石炭系过渡层的初探     

Toshifumi KOMATSU  Reishi TAKASHIMA  TA Hoa PHUONG  Tran Huyen DANG  Duc Phong NGUYEN  Huu Hung NGUYEN  Satoru KATO  Kento HIRATA  Takumi MAEKAWA 《地球学报》2012,33(S1):38-38

The Pho Han Formation is exposed on southern Cat Ba Island, Hai Phong Province in northeastern Vietnam, and intercalates the Devonian and Carbonif-erous (D-C) boundary (Ta and Doan, 2007; Komatsu et al., 2012). The D-C boundary section consists mainly of limestone beds, numbered from 1 to 167, interca-lated with alternating black organic-rich shales. The limestone yields abundant brachiopods, crinoid-stems and conodonts. Preliminary investigations on strati-graphy (conodont biostratigraphy and δ13C) and sedi-mentology of beds 113-133 were undertaken in this study.  相似文献   

The Khao Que-Tam Tao gabbro-granite massif, Northern Vietnam: A petrological indicator of the Emeishan plume     

A. G. Vladimirov  P. A. Balykin  Phan Luu Anh  N. N. Kruk  Ngo Thi Phuong  A. V. Travin  Tran Trong Hoa  I. Yu. Annikova  M. L. Kuybida  E. V. Borodina  I. V. Karmysheva  Bui An Nien 《Russian Journal of Pacific Geology》2012,6(5):395-411

New data obtained on the Khao Que-Tam Tao gabbro-granite pluton (Northern Vietnam) are discussed. It was established that this pluton was formed at the Permian-Triassic boundary (250.5 ± 3.2 Ma, ⁴⁰Ar/³⁹Ar isotopic age). Morphologically, it represents a hypabyssal fracture intrusion. The first stage was marked by the intrusion of the picrobasaltic melt, the differentiation of which resulted in the formation of the layered peridotite-gabbro series and the quartz-bearing monzodiorites and granophyres in its endocontact at the final stage. At the second stage, the Khao Que peridotite-gabbro massif was broken in its central part by a fault, along which the Tam Tao granodiorite-granite massif was localized. Numerical simulation using the COMAGMAT program for the basic system and geochemical estimates for the granite system allow the statement that the mafic and granitic melts evolved independently, and their final products were quartz-bearing monzodiorite and granophyre, on the one hand, and aplites and pegmatites, on the other hand. The compositional correlation of the Permian-Triassic magmatic associations in Northern Vietnam (the Nui Chua gabbro pluton and the Khao Que-Tam Tao gabbro-granite and Pia Bioc granite plutons) and in Southeast China (flood basalts) allows these complexes to be regarded as a part of a single large igneous province produced by the Emeishan plume activity.  相似文献   

Three-dimensional hydrostratigraphical modelling to support evaluation of recharge and saltwater intrusion in a coastal groundwater system in Vietnam     

Vu Thanh Tam  Okke Batelaan  Tran Thanh Le  Pham Quy Nhan 《Hydrogeology Journal》2014,22(8):1749-1762

Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.  相似文献   

The photochemical formation of a titan haze analog. Structural analysis by x-ray photoelectron and infrared spectroscopy     

Buu N. Tran  John J. Chera 《Icarus》2003,162(1):114-124

The photochemical flow reactor (D.W. Clarke et al., 2000, Icarus 147, 282-291) has been modified to minimize the incorporation of oxygen and other impurities in the photoproducts. A mixture of gases that approximate their mixing ratios on Titan (N₂, CH₄, H₂, C₂H₂, C₂H₄, and HC₃N) (0.98, 0.018, 0.002, 3.5 × 10⁻⁴, 3 × 10⁻⁴, 1.7 × 10⁻⁵, respectively) was irradiated in the flow photochemical reactor using a 185-nm source to give a Titan haze analog as a solid product. X-ray photoelectron spectroscopy (XPS) gave a composition of 93.3% C, 5.3% N, and 1.4% O. Of the 93.3% carbon, high-resolution XPS revealed that 81.2% was present as CH, CC, and CC groups, 12.1% may be CO, CN, CN, CN, and/or CN groups, 5.3% as a CN group. The peak for N was symmetrical and was assigned to the CN while that for oxygen was assigned to the CO and/or the CO group. Some of these assignments were confirmed by FTIR spectroscopy. The polymeric product had a C:N ratio of 17.6, which is significantly greater than that for Titan haze analogs prepared in discharge reactions. When the polymer was exposed to air for seven days the oxygen content increased by 6% along with an increase in the infrared absorption at 1710 cm⁻¹ assigned to the CO group of a ketone. The oxidation is attributed to the reaction of oxygen with free radicals trapped in the polymer matrix. It is proposed that the photochemical initiation of Titan haze formation from compounds formed from starting materials formed high in Titan’s atmosphere is a more plausible model than haze formed in reactions initiated by solely by discharges. These data will be helpful in the interpretation of the data returned from the Huygens probe of the Cassini mission.  相似文献   

Multi-scale variability of circulation in the Gulf of Tonkin from remote sensing of surface currents by high-frequency radars     

Tran  Manh Cuong  Sentchev  Alexei  Nguyen  Kim Cuong 《Ocean Dynamics》2021,71(2):175-194

Ocean Dynamics - The sea surface velocity measurements obtained during the period of 2014–2016 using two high-frequency radars (HFR), which were installed on the northern coast of Vietnam,...  相似文献   

Predicting soil erosion hazard in Lattakia Governorate(W Syria)   总被引：1，自引：0，他引：1  

Mohammed Safwan  Khallouf Alaa  Alshiehabi Omran  Bao Pham Quoc  Thi Thuy Linh Nguyen  Nam Thai Van  Tran Anh Duong  Harsányi Endre 《国际泥沙研究》2021,36(2):207-220

The main objective of this study is to predict soil erosion in the Lattakia Governorate(WSyria)using the Water Erosion Prediction Project model(WEPP)and to compare the result with that of the RUSLE.Field survey and data collection were carried out,and 44 soil samples were analyzed.In addition,all the necessary input files were prepared for use in the WEPP model and RUSLE.Results show that more than of 80%of the locations studied experience slight to moderate erosion(less than 5 t/ha/y),whereas the rest of the locations experience severe soil erosion hazard.Moreover,the volume of runoff estimated by the WEPP model is in the range of 51e321 mm,and the R^2 between the simulated soil erosion and the predicted runoff reached 0.68.Interestingly,the R^2 between the WEPP model and RUSLE is 0.56,which indicates a good correlation between the two models.  相似文献   

The application of δ¹³C and C/N ratios as indicators of organic carbon sources and paleoenvironmental change of the mangrove ecosystem from Ba Lat Estuary, Red River, Vietnam     

Nguyen Tai Tue  Hideki Hamaoka  Atsushi Sogabe  Tran Dang Quy  Mai Trong Nhuan  Koji Omori 《Environmental Earth Sciences》2011,64(5):1475-1486

In this study, two sediment cores (~70 cm) were collected from separate mangrove forests straddling the Ba Lat Estuary, Red River of northern Vietnam, to examine the origins of sedimentary organic carbon (SOC) and reconstruct the paleoenvironment. In addition, mangrove leaves and particulate organic matter were collected and measured for δ¹³C to trace the origins of SOC. The cores were analyzed by high-resolution sections for δ¹³C, TOC, C/N ratios, sediment grain size, water content, and porosity, with values of δ¹³C, TOC, and C/N ratios ranging from −28.19 to −22.5‰, 2.14–30.94 mg/g, and 10.29–18.32, respectively. The δ¹³C and TOC relationship indicated that there were some small residual effects of diagenetic processes on TOC and δ¹³C values in mangrove sediments. However, the shifts of δ¹³C and C/N ratios from the bottom to the surface sediment of the cores explained the change in organic matter sources, with values of C/N > 12 and δ¹³C < −25‰, and C/N < 12 and δ¹³C > −25‰ indicated terrestrial (e.g., mangrove litter) and marine phytoplankton sources, respectively. The covarying δ¹³C, C/N ratios, and sediment grain sizes during the past 100 years in sediment cores showed that the paleoenvironment may be reconstructed into three environments (subtidal, tidal flat, and intertidal mangrove). General trends in δ¹³C and C/N followed a gradual increase in the C/N ratio and a concomitant decrease in δ¹³C from the subtidal, through to tidal flat, and to the intertidal mangrove. δ¹³C and C/N ratios are therefore effective in measuring the continuum of environmental change in mangrove ecosystem.  相似文献   

Experiments and Dynamic Finite Element Analysis of a Wire-Rope Rockfall Protective Fence     

Phuc Van Tran  Koji Maegawa  Saiji Fukada 《Rock Mechanics and Rock Engineering》2013,46(5):1183-1198

The imperative need to protect structures in mountainous areas against rockfall has led to the development of various protection methods. This study introduces a new type of rockfall protection fence made of posts, wire ropes, wire netting and energy absorbers. The performance of this rock fence was verified in both experiments and dynamic finite element analysis. In collision tests, a reinforced-concrete block rolled down a natural slope and struck the rock fence at the end of the slope. A specialized system of measuring instruments was employed to accurately measure the acceleration of the block without cable connection. In particular, the performance of two energy absorbers, which contribute also to preventing wire ropes from breaking, was investigated to determine the best energy absorber. In numerical simulation, a commercial finite element code having explicit dynamic capabilities was employed to create models of the two full-scale tests. To facilitate simulation, certain simplifying assumptions for mechanical data of each individual component of the rock fence and geometrical data of the model were adopted. Good agreement between numerical simulation and experimental data validated the numerical simulation. Furthermore, the results of numerical simulation helped highlight limitations of the testing method. The results of numerical simulation thus provide a deeper understanding of the structural behavior of individual components of the rock fence during rockfall impact. More importantly, numerical simulations can be used not only as supplements to or substitutes for full-scale tests but also in parametric study and design.  相似文献   

Timing of left-lateral shearing along the Ailao Shan-Red River shear zone: constraints from zircon U–Pb ages from granitic rocks in the shear zone along the Ailao Shan Range, Western Yunnan, China     

Yuan Tang  Junlai Liu  My-Dung Tran  Zhijie Song  Wenbin Wu  Zhaochong Zhang  Zhidan Zhao  Wen Chen 《International Journal of Earth Sciences》2013,102(3):605-626

As the boundary between the Indochina and the South China blocks, the Ailao Shan-Red River (ASRR) shear zone underwent a sinistral strike-slip shearing which is characterized by ductile deformation structures along the Ailao Shan range. The timing issue of left-lateral shearing along the ASRR shear zone is of first-order importance in constraining the nature and regional significance of the shear zone. It has been, therefore, focused on by many previous studies, but debates still exist on the age of initiation and termination of shearing along the shear zone. In this paper, we dated 5 samples of granitic plutons (dykes) along the Ailao Shan shear zone. Zircon U–Pb ages of four sheared or partly sheared granitic rocks give ages of 30.9 ± 0.7, 36.6 ± 0.1, 25.9 ± 1.0 and 27.2 ± 0.2 Ma, respectively. An undeformed granitic dyke intruding mylonitic foliation gives crystallization age of 21.8 ± 1 Ma. The Th/U ratios of zircon grains from these rocks fall into two populations (0.17–1.01 and 0.07–0.08), reflecting magmatic and metamorphic origins of the zircons. Detailed structural and microstructural analysis reveals that the granitic intrusions are ascribed to pre-, syn- and post-shearing magmatisms. The zircon U–Pb ages of these granites provide constraints on timing of the initiation (later than 31 Ma from pre-shearing granitic plutons, but earlier than 27 Ma from syn-shearing granitic dykes) and termination (ca. 21 Ma from the post-shearing granitic dykes) of strong ductile left-lateral shearing, which is consistent with previous results on the Diancang Shan and Day Nui Con Voi massifs in the literature. We also conclude that the left-lateral shearing along the ASRR shear zone is the result of southeastward extrusion of the Indochina block during the Indian–Eurasian plate collision. Furthermore, the left-lateral shearing was accompanied by the ridge jump, postdating the opening, of the South China Sea.  相似文献   

Structural controls on the occurrence and morphology of karstified assemblages in northeastern Vietnam: a regional perspective     

Hai Thanh Tran  Bat Van Dang  Chi Kim Ngo  Que Dinh Hoang  Quyen Minh Nguyen 《Environmental Earth Sciences》2013,70(2):511-520

Karstified assemblages occur widely in, and distinctively shape, the geological landscape of the northeastern part of Vietnam. These carbonate rocks were deposited during three major periods of basinal evolution including: (1) Late Cambrian, (2) Early Devonian to Early Carboniferous, and (3) Carboniferous to Earliest Triassic. These sedimentary units contain primary sedimentary structures and have undergone numerous post-depositional geological processes including multiple deformational events, which can be regionally correlated. Several thrusting events and associated folding have led to significant thickening of the carbonate units. The subsequent post-thrusting cross-folding events, followed by several phases of brittle faulting and fracturing further modified the spatial geometry and outcrop of these rocks. The combination and interaction of the primary structures with those formed during the long-lived and complicated deformational history is an important controlling factor in local and regional hydrogeological systems in the region. The geological structures now recorded in the carbonate units ultimately govern the formation of the unique modern surface and sub-surface geomorphology of the karstic terrains in northeastern Vietnam. These structures should be further investigated in the context of water resource assessment and natural hazard prediction and mitigation.  相似文献