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Date submitted2023-10-04
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Date accepted2024-09-24
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Date published2025-02-25
Crustal movement model in the ITRF2020 – a case study in Northern Vietnam
- Authors:
- Bui Thi Hong Tham
- Phi Truong Thanh
In the North area of Vietnam, the crustal movement velocity of 38 GNSS points belonging to different international Earth reference frames (ITRF2000, ITRF2005, ITRF2008) is adjusted to the international Earth reference frame ITRF2020. This is the latest frame up to now. Since then, the picture of crustal movement in the North area of Vietnam has been unified in a dynamic coordinate system. In the study area, the rate of crustal movement is about 35 mm/year, and the direction of displacement is from northwest to southeast. To build a model of the crustal movement of the Earth in the northern area of Vietnam, the movement velocity data of 38 stations in ITRF2020 is evaluated with high accuracy. All points are also satisfactory. And then, the crustal movement velocity model is built by using the collocation method in the form of the 3-order Markov function. Within 38 stations, 34 stations are used to build the model and 4 remaining stations are used as checked stations. The obtained results show that the Earth's crust movement velocity model has an accuracy of about 2 mm/year for movement velocity and 2 deg for movement direction. This is the first model of Earth's crust movement in the North of Vietnam that has been built in the latest dynamic coordinate system ITRF2020. These results have important significance in the research and practical application of the movement of the Earth's crust. The steps of building the movement velocity model in this study can be applied to other experimental areas in the territory of Vietnam.
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Date submitted2023-03-01
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Date accepted2024-06-03
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Date published2025-02-25
Lamprophyres of the Peshchernoe gold deposit, their geological position, material composition, and metasomatic alterations (Northern Urals)
The article presents the first data on biotite-hornblende lamprophyres discovered at the Peshchernoe gold deposit. We consider the geological position of lamprophyre dikes in the deposit structure and the relationship of these rocks with tectonically weakened and mineralized zones. The data on the structural position of mineralized zones, faults, dike bodies, metasomatic halos, and host volcanogenic-sedimentary rocks confirm the tectonic nature of the Peshchernoe deposit alteration system. Lamprophyre dikes are pre-ore, as evidenced by the superimposed metasomatic mineral associations. We assume that dikes of andesitic rocks, lamprophyres, and subsequently hydrothermal fluids, including ore-bearing ones, were intruded along the fault zone of northeastern strike at different geological times. The description of mineralogical and chemical transformations of lamprophyres, which occurred as a result of alteration, is given. Two stages of metasomatism are distinguished: carbon dioxide (beresitization-listvenitization) and subsequent alkaline (sodic metasomatism). During carbon dioxide metasomatism, dark-coloured minerals are replaced by chlorite, albitization and sericitization of plagioclase occur, and ferruginous dolomite is formed under the influence of a significant supply of CO2. Alkaline (sodic) metasomatism is superimposed on the mineral metasomatic paragenesis of the first stage. We consider metasomatic zoning during sodic metasomatism, manifested in one of the spessartite dikes. Chlorite and relics of magmatic dark-coloured minerals are replaced by magnesite, the supply of Na leads to the appearance of newly formed albite, and the supply of S leads to the formation of pyrite, which concentrates iron from other minerals. As a result of the sodic metasomatism, iron content in carbonates decreases in the direction from the outer metasomatic zone to the inner one. We conclude that it was the alkaline-sulphide sodium solutions that performed the ore-bearing function, and beresitization and listvenitization prepared a favourable environment for ore deposition.
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Date submitted2023-07-07
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Date accepted2023-12-27
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Date published2024-08-26
Landslide hazard assessment in Tinh Tuc town, Cao Bang province, Vietnam using Frequency ratio method and the combined Fractal-frequency ratio method
Landslides are one of the most frequent natural disasters that cause significant damage to property in Vietnam, which is characterized by mountainous terrain covering three-quarters of the territory. In 17 northern mountainous provinces of the country, over 500 communes are at a high to very high landslide hazard. The main goal of this study was to establish landslide hazard maps and conduct a comparative evaluation of the efficiency of the methods employed in Tinh Tuc town, Cao Bang province. The landslide hazard assessment was carried out in this study using the combined Fractal-frequency ratio (FFR) and the Frequency ratio (FR) methods. The FR method is based on the actualist principle, which assumes that future landslides may be caused by the same factors that contributed to slope failure in the past and present. The FFR method is based on the determination of the fractal dimension, which serves as a measure of the landslide filling density in the study area. Eight landslide-related factors were considered and presented in cartographic format: elevation, distance to roads, slope, geology, distance to faults, land use, slope aspect, and distance to drainage. Determining the area under the receiver operating characteristic curve (ROC-AUC) and verification index (LRclass) was performed to assess the performance of prediction models and the accuracy of the obtained maps. As a result, five zones were identified for the study area, characterized by very low, low, moderate, high, and very high landslide hazards. The analysis of the reliability of the obtained landslide hazard maps using the AUC and LRclass indices revealed that the FFR model has a higher degree of reliability (AUC = 86 %, LRclass = 86 %) compared to the FR model (AUC = 72 %, LRclass = 73 %); therefore, its use is more effective.
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Date submitted2008-11-05
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Date accepted2009-01-30
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Date published2009-12-11
Geoeconomic significance of the trans-eurasian transport route
- Authors:
- I. D. Kotliarov
Different possibilities for Russia to organize a global transport project are analyzed on a basis of two concepts (space as an economical resource and control over global transport routes as a necessary element of geopolitical domination). It is shown that it is impossible to use Northern Sea Route as a global transport project and that this is crucial for Russia to set up a railway route between Korea and Europe.