Stanniferrous granites of Vietnam: Rb-Sr and Ar-Ar isotope age,composition, sources,and geodynamic formation conditions     

Anh  Phan Luu  Vladimirov  A. G.  Kruk  N. N.  Polyakov  G. V.  Ponomarchuk  V. A.  Hoa  Tran Trong  Phuong  Ngo Thi  Kuibida  M. L.  Annikova  I. Yu.  Pavlova  G. G.  Kiseleva  V. Yu. 《Doklady Earth Sciences》2010,432(2):839-845

Doklady Earth Sciences - Stanniferrous granite-leucogranite massifs in Vietnam to which the bedrock and placer commercial deposits of cassiterite are associated (Timtuc etc.) are of late Cretaceous...  相似文献   

Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface   总被引：2，自引：2，他引：0  

Taro Uchimura  Ikuo Towhata  Trinh Thi Lan Anh  Jou Fukuda  Carlos J. B. Bautista  Lin Wang  Ichiro Seko  Taro Uchida  Akira Matsuoka  Yosuke Ito  Yuichi Onda  Sho Iwagami  Min-Seok Kim  Naoki Sakai 《Landslides》2010,7(3):351-357

A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors.  相似文献   

Geochemistry,zircon U–PB ages and HF isotopes of the Muong Luan granitoid pluton,Northwest Vietnam and its petrogenetic significance     

Pham T. Hieu  Nong T. Q. Anh  Pham Minh  Nguyen T. B. Thuy 《Island Arc》2020,29(1)

The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian–middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO₂ contents (59.9–75.1 wt%) and high K₂O contents. They display typical features of I‐type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I‐type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA–ICP–MS U–Pb zircon is at 242–235 Ma, corresponding to Indosinian time. Zircon ε_Hf values of –5.6 to –10.4, in combination with moderate Mg values of 34–45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (T_DM2 = 1624–1923 Ma).  相似文献   

Arsenic in groundwater of the Red River floodplain, Vietnam: Controlling geochemical processes and reactive transport modeling   总被引：4，自引：0，他引：4  

Dieke Postma  Flemming Larsen  Mai Thanh Duc  Pham Quy Nhan 《Geochimica et cosmochimica acta》2007,71(21):5054-5071

The mobilization of arsenic (As) to the groundwater was studied in a shallow Holocene aquifer on the Red River flood plain near Hanoi, Vietnam. The groundwater chemistry was investigated in a transect of 100 piezometers. Results show an anoxic aquifer featuring organic carbon decomposition with redox zonation dominated by the reduction of Fe-oxides and methanogenesis. Enhanced P_CO2 pressure causes carbonate dissolution to take place but mainly in the soil and unsaturated zone. The concentration of As increases over depth to a concentration of up to 550 μg/L. Most As is present as As(III) but some As(V) is always found. Arsenic correlates well with NH₄, relating its release to organic matter decomposition and the source of As appears to be the Fe-oxides being reduced. Part of the produced Fe(II) is apparently reprecipitated as siderite containing less As. Results from sediment extraction indicate most As to be related to the Fe-oxide fractions. The measured amount of sorbed As is low. In agreement, speciation calculations for a Fe-oxide surface suggest As(III) to constitute only 3% of the surface sites while the remainder is occupied by carbonate and silica species. The evolution in water chemistry over depth is homogeneous and a reactive transport model was constructed to quantify the geochemical processes along the vertical groundwater flow component. A redox zonation model was constructed using the partial equilibrium approach with organic carbon degradation in the sediment as the only rate controlling parameter. Apart from the upper meter a constant degradation rate of 0.15 C mmol/L/yr could explain the redox zonation throughout the aquifer. Modeling also indicates that the Fe-oxide being reduced is of a stable type like goethite or hematite. Arsenic is contained in the Fe-oxides and is first released during their dissolution. Our model further suggests that part of the released As is adsorbed on the surface of the remaining Fe-oxides and in this way may be retarded.  相似文献   

Effect of the bubble size on the dynamic adsorption of frothers and collectors in flotation     

Anh V. Nguyen  Chi M. PhanGeoffrey M. Evans 《International Journal of Mineral Processing》2006

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Projected 21st century climate change on snow conditions over Shasta Dam watershed by means of dynamical downscaling          下载免费PDF全文

Toan Trinh  M. Levent Kavvas  Kei Ishida  Kara Carr  Noriaki Ohara 《水文研究》2017,31(16):2887-2901

Snow is an important component of the Earth's climate system and is particularly vulnerable to global warming. It has been suggested that warmer temperatures may cause significant declines in snow water content and snow cover duration. In this study, snowfall and snowmelt were projected by means of a regional climate model that was coupled to a physically based snow model over Shasta Dam watershed to assess changes in snow water content and snow cover duration during the 21st century. This physically based snow model requires both physical data and future climate projections. These physical data include topography, soils, vegetation, and land use/land cover, which were collected from associated organizations. The future climate projections were dynamically downscaled by means of the regional climate model under 4 emission scenarios simulated by 2 general circulation models (fifth‐generation of the ECHAM general circulation model and the third‐generation atmospheric general circulation model). The downscaled future projections were bias corrected before projecting snowfall and snowmelt processes over Shasta Dam watershed during 2010–2099. This study's results agree with those of previous studies that projected snow water equivalent is decreasing by 50–80% whereas the fraction of precipitation falling as snowfall is decreasing by 15% to 20%. The obtained projection results show that future snow water content will change in both time and space. Furthermore, the results confirm that physical data such as topography, land cover, and atmospheric–hydrologic data are instrumental in the studies on the impact of climate change on the water resources of a region.  相似文献   

A new species Lobophora tsengii sp. nov. (Dictyotales; Phaeophyceae) from Bach Long Vy (Bailongwei) Island,Vietnam     

Sun  Zhongmin  Dao  Minh Dong  Tran  Quoc Toan  Dam  Duc Tien 《中国海洋湖沼学报》2021,39(6):2363-2369

Journal of Oceanology and Limnology - A new species Lobophora tsengii is described from Bach Long Vy (Bailongwei) Island, Haiphong Province, Vietnam. The plants inhabit the subtidal zone and have...  相似文献   

Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C     

Neubeck A  Duc NT  Bastviken D  Crill P  Holm NG 《Geochemical transactions》2011,12(1):6-10

Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.  相似文献   

A study of the connection between tropical cyclone track and intensity errors in the WRF model     

Du Duc Tien  Thanh Ngo-Duc  Hoang Thi Mai  Chanh Kieu 《Meteorology and Atmospheric Physics》2013,122(1-2):55-64

This study examines the dependence of the tropical cyclone (TC) intensity errors on the track errors in the Weather Research and Forecasting (WRF-ARW) model. By using the National Centers for Environmental Prediction global final analysis as the initial and boundary conditions for cloud-resolving simulations of TC cases that have small track errors, it is found that the 2- and 3-day intensity errors in the North Atlantic basin can be reduced to 15 and 19 % when the track errors decrease to 55 and 76 %, respectively, whereas the 1-day intensity error shows no significant reduction despite more than 30 % decrease of the 1-day track error. For the North-Western Pacific basin, the percentage of intensity reduction is somewhat similar with the 2- and 3-day intensity errors improved by about 15 and 19 %, respectively. This suggests that future improvement of the TC track forecast skill in the WRF-ARW model will be beneficial to the intensity forecast. However, the substantially smaller percentages of intensity improvement than those of the track error improvement indicate that ambient environment tends to play a less important role in determining the TC intensity as compared to other factors related to the vortex initialization or physics representations in the WRF-ARW model.  相似文献   

The VLTI – A Status Report     

A. Glindemann  J. Algomedo  R. Amestica  P. Ballester  B. Bauvir  E. Bugueño  S. Correia  F. Delgado  F. Delplancke  F. Derie  Ph. Duhoux  E. di Folco  A. Gennai  B. Gilli  P. Giordano  Ph. Gitton  S. Guisard  N. Housen  A. Huxley  P. Kervella  M. Kiekebusch  B. Koehler  S. Lévêque  A. Longinotti  S. Ménardi  S. Morel  F. Paresce  T. Phan Duc  A. Richichi  M. Schöller  M. Tarenghi  A. Wallander  M. Wittkowski  R. Wilhelm 《Astrophysics and Space Science》2003,286(1-2):35-44

The Very Large Telescope (VLT) Observatory on Cerro Paranal (2635 m) in Northern Chile is approaching completion. After the four 8-m Unit Telescopes (UT) individually saw first light in the last years, two of them were combined for the first time on October 30, 2001 to form a stellar interferometer, the VLT Interferometer. The combination in pairs of all four UTs was completed in September 2002. In this article, we will describe the subsystems of the VLTI and the planning for the following years. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献