Tạp chí của Viện Khoa học Địa chất và Khoáng sản
Application of artificial intelligence in geophysical anomaly analysis from electromagnetic data
Electromagnetic field data plays an extremely important role in representing geological structures and anomalous objects that exist from shallow depths to several tens of kilometers. The application of Artificial Intelligence (AI) in the analysis workflow of such geophysical data can bring practical benefits, such as providing fast and accurate results while saving expert resources. In this study, we focus on building a complete low-frequency electromagnetic (magnetotelluric) dataset by supplementing missing survey data and identifying underground anomalous objects from high-frequency electromagnetic data (Ground Penetrating Radar) based on diffraction mechanisms. The general AI model is developed based on interconnected neural network layers, including different networks such as MLP and CNN, to implement tasks of constructing a complete electromagnetic field dataset for the Olympic Dam mineral area in Australia, and distinguishing subsurface scattering objects from Ground Penetrating Radar data in Dong Nai province, Vietnam.
Research on late Devonian – early Carboniferous deep-water sedimentary rocks in Central Vietnam: stratigraphic and geotectonic implications
Detailed analysis of two deep – water mass – transport deposit (DWMTD) sections (Quang Trach, Huong Son) and two siliceous microfossil – bearing sections (Minh Hoa, Duc Tho) in Central Vietnam’s Truong Son Fold Belt (TSFB) (Northeastern Indochina Terrane) reveals a NW – trending deep – water continental slope system existed throughout the Upper Devonian–Lower Carboniferous. Radiolarians and tentaculitoids from Ngoc Lam Formation (Minh Hoa section) constrain deposition to the Upper Devonian, while cherts from Thien Nhan Formation (Duc Tho section) yield Tournaisian – early Visean radiolarians. Geochemical and lithological data indicate Minh Hoa cherts formed near the continental rise, while Duc Tho cherts accumulated on the continental slope. Two DWMTDs further confirm a continental margin setting. This system extends into Central Laos; however, it contrasts with the Loei Fold Belt (Western Indochina), NE Thailand – where an oceanic crust existed during the Late Devonian – Early Carboniferous period, and arc – related subduction volcanism occurred in the Carboniferous. At the TSFB, the absence of true oceanic crust likely prevented Carboniferous–age subduction and magmatic arc activity.
Normalization of geochemical data in sediments by XRF for environmental change research: A case study of a sediment core from the Ba Lat estuary.
This study examines the application of centered log-ratios (clr) normalization and pairwise log-ratios (pwlr) techniques to chemical composition derived from XRF core-scanning (XRF-CS) and portable XRF (pXRF) analyses of an undisturbed sediment core from the Ba Lat estuary. Results show that, once clr normalization is applied, both datasets exhibit consistent geochemical trends, despite discrepancies in the detected data. This process effectively minimizes the influence of sediment characteristics, water content, organic matter, and instrument-specific variability, thereby producing a dataset suitable for robust multivariate statistical analysis, as confirmed by reliable geochemical correlations. Similarly, the pwlr transformation reduces noise and corrects asymmetries in environmentally sensitive element pairs, further enhancing data reliability. By applying clr and pwlr techniques to two independent XRF datasets obtained using different instruments from the same core, this study successfully identifed the historical 1971 typhoon-flood event, recorded as an anomalous sediment layer at 65–68 cm depth. These findings highlight the importance of clr and pwlr transformations as crucial preprocessing steps in handling XRF-derived chemical data for sedimentological and paleo-environmental researches.
Physico-chemical conditions of Au mineralisation at the Xa Loi deposit, the Central Truong Son Belt, Vietnam: Insights from fluid inclusion studies
A fluid inclusion study of quartz from the Xa Loi gold deposit in Vinh Ô commune, Vinh Linh district, Quang Tri province, located in the Truong Son belt of central Vietnam, was conducted to elucidate the physicochemical conditions of the hydrothermal fluids responsible for gold mineralization. The fluid inclusions are dominated by liquid–vapor types, with homogenization temperatures ranging from 180°C to 370°C and clustering mainly between 240°C and 300°C, indicating medium- to high-temperature hydrothermal conditions consistent with deep metamorphic environments. The fluid salinities vary from 4.97 to 9.88 wt% NaCl equivalent (commonly 5–7 wt%), and the calculated fluid densities range from 1.28 to 1.35 g/cm³ (average 1.31 g/cm³), suggesting low- to medium-salinity, H₂O-rich fluids formed under high-temperature and high-pressure conditions. The trapping pressures are estimated at 64.2–70.3 MPa, corresponding to depths of 4.66–4.95 km, while the pH values range from 6.22 to 6.33 (average 6.27), indicating a slightly neutral environment favorable for the transport and precipitation of gold together with sulfide minerals. These characteristics indicate that the ore-forming fluids at Xa Loi exhibit typical features of orogenic gold systems, formed under medium-grade metamorphic conditions, high pressures, and intense compressional tectonics. The results not only shed light on the source and mechanisms of gold deposition at the Xa Loi deposit but also provide a scientific basis for guiding exploration for gold mineralization within the Truong Son belt.
Distribution characteristics of natural radionucclides in seawater and surface sediments in Cua Day - Cua Hoi waters, Thanh Hoa, Gulf of Tonkin, Vietnam
The characterization of naturally occurring radionuclides in seawater and seafloor surface sediments is necessary to assess marine environmental characteristics and their direct impact on marine ecosystems and indirect impacts on human health. The coast of Thanh Hoa, Vietnam is known for many mines and titanium ore points and is a key economic region in the coastal estuarine area. This study determined the concentration of naturally occurring radionuclides (210Po, 210Pb, 226Ra, 234U and 238U) in seawater and (226Ra, 228Ra (232Th) and 40K) surface sediments at stations with sampling depths varying from 0-30m of seawater. In this study, twenty-three samples of seabed sediment at the coast of Thanh Hoa, Vietnam were collected and measured using a high-purity germanium detector (HPGe). The average activity of 226Ra, 228Ra (232Th) and 40K is 30.3±1.94, 53.3±2.98 and 673±38.5 Bq.kg-1, respectively. There is a strong correlation between those radionuclides and withe silt and clay, which suggests that these radionuclides may be of similar material origin. The particle size of seabed sediments in the study area has a significant effect on natural radioactive nuclear activities and spatial distribution. Naturally occurring radionuclei (210Po, 210Pb, 226Ra, 234U, and 238U) in seawater were various in difference sampling stations, and seawater depths which were observed 0.77, 0.78, 9.09, 49.8, and 54.3 mBq L-1, respectively. The results showed an disequilibrium between 210Po and 210Pb and that the 210Po/210Pb ratios differed in depth. High 226Ra, 234U, and 238U activities may be associated with titanium deposits along coastal, estuarine sediment sources. There is a relationship between 226Ra and 210Pb operations with sampling depth, distance from shore, while it is negligible recorded for 210Po, 234U, and 238U. The spatial distribution is divided into two regions, in which the estuarine (near-shore) area has higher radionuclide activity than the offshore zone. The results support the conclusion that the origin of sedimentary material is related to estuaries and transported from land sources.
Characterization of finite strain ellipsoid of the Late Permian-Early Triassic metamorphic complexes in the Kon Tum terrain
The parameters of finite strain ellipsoid determined from the regional metamorphic rocks record the relevant tectonic regime. The ductilely deformed Late Permian-Early Triassic metamorphic rocks, formed at depth, are widely exposed in the Kon Tum terrane and record a long tectonic history. In order to characterize the Late Permian-Early Triassic tectonic regime for the Kon Tum terrane, 20 oriented samples of gneiss and crystalline schist were selected from the Kham Duc, Ngoc Linh, and Kan Nack complexes for analyzing the finite strain ellipse by Rf/Phi method and determination of the finite strain ellipsoid from a combination of 3 thin sections oriented perpendicularly to the three principal strain axes. The analysis results indicate that the Late Permian-Early Triassic metamorphic rocks in the Kon Tum terrane are characterized by 3-dimensional finite strain ellipsoids with maximum stretching axis X elongated in a northwest-southeast direction and a maximum shortening axis Z nearly vertically. These strain geometries are consistent with a northwest-southeast striking extensional regime during the Late Permian-Early Triassic with vertical shortenning during exhumation of ductile rocks in the Kon Tum terrane.
U-pb zircon ages of granites from the Song Chay complex, Hoang Su Phi, Ha Giang, and their geological implications
Granitoids of the Song Chay Complex occupy nearly 89% of the study area. The lithological assemblage includes: Phase I-two-mica granite, fine-grained muscovite granite with deformation features, granitic gneiss, and porphyritic granite; Phase II—muscovite granite and massive two-mica granite; and Phase III-pegmatite and aplite granite. Zircon grains were separated from biotite granitic gneiss (HS.1168), massive muscovite granite (HS.1248), and massive two-mica granite (HS.3054), which belong to Phase I and Phase II of the Song Chay Complex in the Hoang Su Phi area. U-Pb zircon ages were determined using LA-ICP-MS, yielding weighted mean ²⁰⁶Pb/²³⁸U ages ranging from 431 to 433 Ma, corresponding to the Middle Silurian (Wenlock epoch). Combined with the oscillatory zoning characteristics observed in zircon, these ages are interpreted as the magmatic crystallization age of the granites.
The main contents of the new geological, georesource map of Việt Nam and adjacent sea areas scale 1:1,000,000 with a summary of its explanatory book.
Geology of Việt Nam and its adjacent sea areas composed of seven major supersequences spanning from the Archean to the Phanerozoic. (I) Meso–Neoarchean Supersequence: Exposed in the Hoang Lien Son terrane, this sequence includes biotite gneiss and amphibolite intruded by tonalite-trondhjemite-granodiorite (TTG) granitoids, with U-Pb zircon ages of 2900–2835 Ma. (II) Paleoproterozoic Supersequence: Characterized by two-mica–kyanite schists. It also includes granosyenite and metagabbro intrusions (2325–2295 Ma) and amphibole–sillimanite–garnet gneiss in the Nui Con Voi area, both overprinting metamorphosed to amphibolite–granulite facies. (III) Middle Meso–Neoproterozoic Supersequence: Composed of biotite–granite–sillimanite plagiogneiss and graphite-bearing crystalline schist (Pt2–Pt31). The Posen batholith, an I-type granite dated 762–758 Ma. (IV) Neoproterozoic–Silurian Supersequence: exposures include metapelitic turbidites with minor garnet-amphibolite (Pt3–Ꞓ1), phosphorite-rich carbonates (Ꞓ1), and shelf to deep-marine turbidites (Ꞓ2–O1) with diverse benthic fossils. In the Việt Nam–Laos terrane, greenschists, and amphibolites are common. The Hiep Duc ophiolite assemblage (518–500 Ma) includes basalt to dacite metavolcanic and siliciclastic turbidites. Associated granitoids include I-type granites (476–470 Ma) of the Long Dai arc affinity and S-type orogenic granites (450–443 Ma), reflecting the closure of the Prototethys via dual subduction beneath the Kon Tum and Việt Nam–Laos terranes. Upper Silurian units are limited in extent but contain brachiopods, corals, fish, and plants similar to those found in South China assemblages. (V) Devonian–Middle Permian Supersequence: Lies disconformably atop older rocks and consists of terrigenous to carbonate–siliceous sediments, with fossiliferous horizons marking the Frasnian–Famennian boundary in central Việt Nam and the Famennian–Tournasian transition in the northeast. The Song Ma ophiolite assemblage (360–335 Ma) records a Paleo-Tethyan oceanic branch. Carbonate-platform deposits (C1v–P3w) are widely spread along with carbonate–siliceous sequences, volcanic rocks (andesite–basalt–rhyodacite), and I-type granites (300–270 Ma) formed the Mekong magmatic arc. (VI) Upper Permian, Wuchiapingean–Middle Jurassic Supersequence: In the north, Emeishan-type basaltic flows and intrusions (258–253 Ma) associated with intracontinental rifts. They are overlain by coal-bearing paralic deposits containing Cathaysia flora, interbedded with bauxite and calcareous shales. In the Kon Tum terrane, granulite-grade rocks dominate. In contrast, in the Việt Nam–Laos terrane, S-type granites (258–248 Ma) are associated with the Indosinian orogeny and thrusting in the Truong Son belt. Post-orogenic sequences include terrigenous–carbonate rocks, rhyodacite, and granites (245–230 Ma). In the north, Upper Triassic to Middle Jurassic sediments are primarily composed of coarse clastics, with coal beds and abundant plant fossils. In contrast, marine deposition persisted in southern regions during the Jurassic. (VII) Upper Jurassic–Quaternary Supersequence: Includes Cretaceous coarse red clastic deposits and calc-alkaline volcanic–plutonic rocks (120–95 Ma), along with a 90 Ma dyke system—all components of the Da Lat Cretaceous magmatic arc. Paleogene units comprise potassic–alkaline volcanic and intrusive rocks (35–25 Ma) of limited extent. Eocene–Oligocene sediments are mainly deltaic clastics deposited in syn-rift settings. Miocene–Quaternary sediments are post-rift shallow marine deposits forming part of the region’s petroleum systems and are widely distributed across the East Sea. Diffuse Miocene–Quaternary basaltic fields (tholeiitic to alkaline) with bauxite–laterite weathering crusts developed in stages from 15.8 Ma to the present, both onshore and offshore. Of the natural resources, the following categories may be worth listing: (I) Mineral resources: The metallic mineral resources: In iron and ferrous metallic resources, Fe, Ni-Cu, W, and Cr-bearing ores formed industrial mines such as Thach Khe, Nui Phao W-polymetal mine, and Ban Phuc Ni-Cu-Co mine. The largest resource among the base metals (Sb, Cu, Pb-Zn, and Sn) is Pb-Zn ore, with a series of deposits in the Cho Don-Cho Dien (Bac Kan) region. The Sin Quyen Cu-Au ore deposit (an IOCG type) is considered one of the region’s largest mines. Valuable primary and placer tin ores are found in Quy Chau-Quy Hop, Son Duong, and Lam Dong. Light metals, such as Al and Ti, are great potential. Al includes two popular deposit types: bauxite from sedimentary and from volcanic weathering genesis. The large Ti depossits, which are coastal ilmenite-bearing placer, found mainly in Ninh Thuan-Binh Thuan. Precious native and placer gold is widely distributed, but a typical representative is the Phuoc Son – Bong Mieu gold mine, which has been mined for centuries. The rare earth element group has high potential and is found in two major types. The hydrothermal vein type was discovered in Lai Chau, Yen Bai, and Lao Cai. The other is ion-absorbed in weathered zones, recently explored and found in the Ben Den (Lao Cai) area. Non-metallic mineral resources: among industrial materials, apatite is associated with metamorphosed sediments in NW-SE-oriented bands in Lao Cai. Barite with a modest distribution area is discovered in northern Việt Nam. Fluorite, in contrast, appears as accessory minerals in several rare earth and W-multiple metal ore deposits (e.g., Nui Phao mine). Ceramic materials, including kaolin and feldspar, are found in industrial mines across Việt Nam. Glass-quality sand with large reerves is exposed in several coastal provinces in the northern and central regions. Additionally, the potential of dolomites and quartzites are considerable. The most popular gemstones in Việt Nam are ruby and sapphire, which are found in Luc Yen, Yen Bai and Quy Chau-Quy Hop (Nghe An. (II) Energy resources: Việt Nam’s energy resources include coal, oil, gas, uranium ore, and geothermal energy. Among the coal mines, the Quang Ninh Mesozoic coal basin is the most valuable. Additionally, coal reservoirs in Tertiary basins, both onshore and offshore are promising. Uranium ore deposits in sandstone strata found in Pa Rong-Pa Lua (Central region) are considered high potential. Oil and gas are primarily discovered in Tertiary sedimentary basins located on the continental shelf. The first oil and gas in Việt Nam was discovered and exploited in the Cuu Long basin. Continental geothermal resources are exposed as hot spring sources, concentrated mainly in the coastal areas of the Central region. Several geothermal sources have been identified in association with Tertiary sedimentary basins in the shelf region. In addition to the above-mentioned natural resources, water and geo-heritage resources can also be listed as valuable. (III) Water resource: Việt Nam is not considered a country of plentiful water resources with total average yearly surface water discharge in Việt Nam is about 830 billion m3 and 26 groundwater-bearing units, among them the water-bearing units in Quaternary loose sediments, in Paleo-Mesozoic carbonate beds, and Neogene-Quaternary basalts are the essential aquifers for the economy and people's livelihood. According to insufficient statistics, there are about 400 occurrences of these mineral resources all over the country. up to 2012, there have been 304 sources, of which there are 268 (on the mainland) with a temperature of 30° C or higher, that have been attributed to the thermal water kind. Mineral mud is found with some sources of hot-mineral water, but the investigation and research of this type of resource has not been noticed, so there is not enough statistical data and accurate assessment. (IV) Geoheritages: The internationally accredited international heritage includes natural heritages (Ha Long -Cat Ba Bay, Phong Nha - Ke Bang_; Global UNESCO Geoparks (Dong Van Rock Plateau, Non Nuoc Cao Bang, Lang Son, Dak Nong) and Cuc Phuong National Park, Pu Luong and Ngoc Son - Ngo Luong Nature Reserves.
Analysis of Geochemical Data for Identifying Sn and W Anomalies in the Dong Van Area, Northeastern Vietnam
Dong Van is an area that is assessed to have potential for polymetallic mineralization in the Northeast of Vietnam. A total of 890 geochemical samples of bottom mud sediments were used to study polymetallic mineralization, thereby identifying Sn, W anomalies in the area. In addition, statistical analysis helps to identify geochemical anomalies in the Dong Van area. Statistical methods and cluster analysis of geochemical data show that the elements Pb, As, Bi, Li, Sn, W, Ta, Ce, Ag, Sb, and Be are good indicator elements, in which the elements Sn, W follow a geometric distribution. Based on the 3-sigma rule, the geochemical anomalies in the content of Sn, W elements reflect the concentration of Sn, W mineral bodies in the area. Trend analysis was applied to determine the spatial variation and relationship between the searched indicator elements and the anomalous areas, which showed that the relative changes in the content of the indicator elements and they can be considered regular. Furthermore, the fit of the Trend functions obtained from the Sn, W elements followed the fourth-order Trend surface model. This result shows that the Trend models can be useful in studying geochemical anomalies and that the Trend analysis helps to determine the concentration areas of the indicator elements in the Dong Van area. In addition, the statistical analysis shows significant potential in using bottom mud sediment samples to investigate polymetallic mineralization. In addition, the geochemical data can help to evaluate the geochemical anomalies of the indicator elements and map the mineral prospectivity of the Dong Van area, Northeast Vietnam. Keywords: Sn-W mineralization, statistical evaluation, Dong Van, Vietnam.
Carboniferous-permian lithostratigraphic units in the duyen hai zone (coastal zone) of north-east vietnam
Carboniferous-Permian deposits are widespread in the Duyen Hai Zone (Coastal Zone) of Northeast Vietnam, but at the moment, lithostratigraphic units of these sequences used for geological mapping always are controversal debate topic and question for discussions. Previous researchs have shown that, lithostratigraphic units for Carboniferous-Permian deposits on the basis of fossil age (Dovjikov A. E. et al. 1965; Nguyen Quang Hạp 1967; Pham Van Quang 1970; Nguyễn Văn Liêm 1974, 1978, 1980; Nguyen Cong Luong 1980, 1985, 2001). Basis on characteristic lithological composition of rocks, the following lithostratigraphic units of Carboniferous-Permian deposits in the Duyen Hai Zone are recognized: Con Voi Formation (D3-C1 cv), Pho Han Formation (D­3-C1 ph), Carboniferous-Middle Permian Sequence and Bai Chay Formation (P3 bc).
Overview of the Late Triassic plant fossil assemblage of the Nong Son coal basin and some comments on paleobotany and paleobotany
The Nong Son coal basin is one of the 5 Late Triassic Nori-Ret coal- bearing sedimentary basins of Vietnam with a graben-type geological structure. The coal-bearing formation has a distinct characteristic: the sediments of the lower part are uncomformably upon the older formations, and in the upper part they are uncomformably covered by formations of the Jurassic sea-continental sedimentary group. Late Triassic plant fossils in the coal-bearing sediments of the Nong Son basin were collected and studied a long time ago (Counillon H., 1903, 1908, 1914; Bourret R., 1925). Later Vietnamese geologists have cooperated with foreign geologists in the process of geological mapping as well as in-depth research, more plant fossils are discovered. (Trần V.T. và Vũ K., 2011; Cát Nguyên Hùng và nnk., 1996; Nguyễn C. H., 1983; Vũ Khúc và nnk.,1984 và Serra C.V. và Franceschi, D. D., 1999). Plant fossils are mainly distributed in sediments of the Suon Giua Formation (the upper part of the Nong Son group). Up to now, the number of species (including open nomenclature) of the plant fossil of Nong Son coal basin has reached about 60, is most of which belong to 2 taxon groups Pteridophyta and Cycadophyta and rich representatives of the Dipteridaceae family; it is also the third most abundant assemblage– after of Hon Gai and Suoi Bang assemblages) and it belongs to Hon Gai flora. The plant fossil assemblage of the Nong Son coal basin has a similar composition to that collected in other coal basins of the same age (Sam Nua, Song Da, Yen Chau, Quang Ninh). This plant fossil assembage represented by Hon Gai flora which is comparable with coeval floras of adjacent regions of Vietnam (such as: Soppong, Phong Sa Ly- Laos, Huổi Hin Lat – Thailand, Ypinlang- Yunnan- China) as well as those of the western margin of Pacific Ocean (such as: Primoria- Far East Russian, Deadong – Korea, Nariwa, Yamaguchi- Japan, Krusin- Malaysia, Bintan- Indonesia) They have common characteristics of being a mixture of Southern Hemisphere elements (Gondwana: Glossopteris indica, Palaeovittar kurzii, Taeniopteris spatulata) and of Northern Hemisphere – Cathaysia floras). The presence of Gondwana ancient elements as well as the mixture of Gondwana and Cathaysia floras are inffered by the separation, dript, and assembly of the Sibumasu continent in its geological evolutionary history with Indochina terrane. Sedimentary studies show that this ancient plant lived in sedimentary environments including pre-mountains, alluvial plains, and the transition from lake facies to river-beds Along with the sediment containing the plant fossil assemblage of Nong Son coal basin, there are georesources that have been exploited (coal), have been researched (uranium) and building materials (sand, gravel, limestone, marble...).
Analysis of hydro-geological structure to determine the interaction between Red river surface water and groundwater in Hanoi area
The study of the interaction between surface water and groundwater plays a crucial role in assessing groundwater recharge sources and the impact of groundwater on surface flow. Although numerous studies have examined the interaction between the Red River’s surface water and groundwater in the Hanoi region at various riverside locations, a detailed analysis of the hydrogeological structure of the riverbed to comprehensively evaluate this interaction has not yet been conducted. This study aims to fill that gap. The results have delineated the distribution of hydrogeological structures in the Red River’s riverbed in the Hanoi area and calculated the hydraulic resistance of riverbed for each zone, providing essential scientific insights for the management and exploitation of water resources.
Correlation network analysis of rare earth elements, uranium, and thorium in primary and weathered rare earth ore in the Then Thau-Ta Chu Phung area, Lai Chau province
The study applied correlation network analysis to clarify the relationships among rare earth elements (REEs), uranium (U), and thorium (Th) in rare earth ore samples from the Thèn Thầu – Tả Chu Phùng area (Lai Châu province). A total of 296 primary ore samples and 147 weathered ore samples were analyzed for elemental concentrations using the ICP-MS method. The results show that, in the primary ores, 119 elemental pairs exhibited correlations, including 114 positive and 5 negative correlations; the network density reached 0.78, reflecting a tightly interconnected elemental structure. In the weathered ores, there were 109 correlated elemental pairs (101 positive and 8 negative correlations), with the network density decreasing to 0.71, indicating that the network structure was weakened due to weathering processes. In the primary ores, elements such as Th, Dy, Er, Y, Gd, and Nd played central roles, reflecting an endogenous origin; Th was the dominant node and served as a geochemical indicator for delineating primary rare earth ore prospects based on primary geochemical anomalies. In the weathered ores, the network structure changed significantly, with elements such as Sm, Eu, Gd, and Sc becoming prominent, and Sc replacing Th as the central element. These elements act as indicators for the exploration of REE mineralization within the weathered crust (secondary ores). U exhibited very low centrality, indicating a strong tendency for dispersion of this element in oxidizing environments.
International experience and proposal of some solutions to complete the policy of mine closure in Vietnam
The article analyzes current policies on environmental rehabilitation and mine closure in Vietnam, and compares them with international experience from some developed countries such as Australia, the United States, China and Russia. Based on the analysis and comparison, the authors identify shortcomings in state management of mine closure activities, as well as assess the environmental - social - financial risks arising in this process and propose solutions to optimize benefits at the regional scale. The research methods applied include multidimensional policy analysis (including SWOT and PESTLE), quantitative analysis of risk data and cost-benefit modeling. The research results show that Vietnam needs to improve the legal framework on mine closure, improve monitoring mechanisms and increase the participation of local communities, and apply GIS technology and artificial intelligence (AI) technology in post-mining monitoring. The application of site-specific technical solutions (for coal, titanium, limestone, metal ore, etc.) is an effective approach to environmental rehabilitation and sustainable land use after mining. The paper also proposes a mine closure risk assessment model as a tool to support policy planning and decision making for the post-mining phase.
Early warning of flash flood and landslide in Vietnam: Current situation and solutions for the future
Flash floods and landslides are natural disasters that frequently occur and cause serious consequences in Vietnam. This article assesses the current status of early warning, including achievements and remaining limitations, analyzes factors affecting warning effectiveness, including technical, organizational, social and economic factors, proposes comprehensive and detailed solutions, focusing on improving forecasting capacity, improving the monitoring system, enhancing community participation, applying advanced technology, emphasizing the importance of inter-sectoral coordination and support from the government and international organizations, and highlights prospects and specific steps for Vietnam to build an effective and sustainable early warning system, contributing to socio-economic development and environmental protection.
Proposed solutions to mitigate saltwater intrusion in the luy river catchment, Binh Thuan province
The Luy River’s catchment is characterized by different types of sediment on the two sides of the river. Particularly, sandy dunes composed mainly from sands and some grits, were formed in the Pleistocene. Contrarily, the low-elevation flat plains composed by intercalated clayey sand and thin clay layers, were formed in the Pleistocene and Holocene. Our research results indicate that saltwater zones are scattered, with large variations in salinity spatially. Freshwater-bearing sandy dunes constitute a barrier against saltwater intrusion from sea. Saltwater intrusion in the whole catchment cannot be explained solely by interaction with sea and rivers, but also the result of historical transgressions, during which saline water filled in the sediment pores. Freshening is the dominant hydrochemical process in the aquifers. Saltwater trapped inside clay aquitards and lower aquifers slows down freshening processes and act as a secondary source of salinity when freshwater at shallow depth is extracted for irrigation. Groundwater simulation results indicate that over the next 50 years, saltwater will still be present, even without any pumping. If abstraction continues in the alluvial plains, Saltwater intrusion will reach about 5 km from the river mouth, and salinization will increase in shallow aquifers by upconing and lateral migration. Therefore, we recommend a combination of both structural and non-structural solutions to prevent and mitigate saltwater intrusion as follows: 1) Solutions to change crop structure, adjust irrigation measures according to actual crop needs, increase vegetation, as well as solutions of alternative surface-water storage and use should be encouraged; 2) Groundwater exploitation in the alluvial plain on the left bank of the Luy River should be banned or at least strictly managed by local authorities; 3) Groundwater exploitation should only be carried out in the sand dune systems on the right bank of the Luy River, with pumping rates controlled according to estimated seasonal recharge; and 4) A managed artificial recharge system can be implemented in the sand dunes to replenish fresh water as well as prevent salt water intrusion.
Using statistical and machine learning models for large-scale landslide hazard susceptibility mapping
The main purpose of this article is to establish a susceptibility zonation map of the landslides in Phuoc Thanh commune, Phuoc Son district, Quang Nam province on a large scale using statistical methods and machine learning models. First, the five Landslide Susceptibility Index (LSI) maps were established from two statistical models (Logistic Regression - LR, Discriminant Analysis – DA) and three machine learning models (Bayesian Network – BN, Artificial Neural Network – ANN, Support Vector Machine – SVM) were generated based on seven maps of landslide conditioning factors (slope, curvature, stream power index-SPI, topographic wetness index-TWI, sediment transportation index-STI, land use/land cover and weathering crust). Next, the five LSI maps will be evaluated for performance with the value of Area Under the Curve (AUC) according to the Receiver Operating Characteristic (ROC) curve. The results indicate that the integrated models have given outputs with good forecasting ability. They are also very useful in land-use planning as well as the prevention and mitigation of risks due to landslides and debris flows in the research area and other similar mountainous areas.
Diagenetic processes of the Middle - Upper Cambrian carbonate sediments in the Đồng Văn region, Hà Giang
The Middle - Upper Cambrian carbonate sediments in the Đồng Văn region, Hà Giang, record a complex diagenetic history that has contributed to shaping the evolution of this carbonate succession. This study employs petrographic analysis using optical microscopy and cathodoluminescence (CL) to identify diagenetic processes, including micritization, cementation, dissolution, dolomitization, dedolomitization, and compaction. The results indicate that micritization formed thin micrite coatings around bioclastic fragments and ooids in a very shallow marine environment, while cementation produced four types of early calcite cements: (1) radiaxial fibrous (30-900 μm, syndepositional marine or shallow burial), (2) granular (80-300 μm, meteoric-phreatic or burial), (3) blocky (100-400 μm, meteoric and burial), and (4) syntaxial calcite overgrowth (near-surface marine or meteoric-phreatic). Dissolution is evidenced by fissure filled with micrite and lithoclast, formed due to subaerial exposure during sea-level fall. Dolomitization occurred in two stages: Type 1 (10-30 μm) within fissures, representing early, low-temperature dolomitization (<50-60°C), and Type 2 (50-150 μm) within ooids and microfractures, indicating late-stage, high-temperature dolomitization (>50-60°C), followed by near-surface dedolomitization. Compaction involved two stages, with small stylolites forming in Stage 1 and larger stylolites in Stage 2, following Type 2 dolomitization. The proposed diagenetic sequence highlights a transition from syndepositional marine to meteoric exposure and deep burial, influenced by sea-level fluctuations and tectonic activity on the South China Block. These findings provide a deeper understanding of the controlling factors of early diagenesis in the development of the Middle to Upper Cambrian carbonate system in the Đồng Văn region, Hà Giang.