Tạp chí Địa chất

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.

Thu, 02 Oct 2025 00:00:00 +0700

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.

U-pb zircon ages of granites from the Song Chay complex, Hoang Su Phi, Ha Giang, and their geological implications

Thu, 02 Oct 2025 00:00:00 +0700

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.

Characterization of finite strain ellipsoid of the Late Permian-Early Triassic metamorphic complexes in the Kon Tum terrain

Thu, 02 Oct 2025 00:00:00 +0700

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.

Distribution characteristics of natural radionucclides in seawater and surface sediments in Cua Day - Cua Hoi waters, Thanh Hoa, Gulf of Tonkin, Vietnam

Bùi Chí Tiến, Quách Đức Tín, Dương Văn Hào, Nguyễn Minh Quảng, Nguyễn Văn Dũng — Thu, 02 Oct 2025 00:00:00 +0700

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.

Physico-chemical conditions of Au mineralisation at the Xa Loi deposit, the Central Truong Son Belt, Vietnam: Insights from fluid inclusion studies

Thu, 02 Oct 2025 00:00:00 +0700

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.

Normalization of geochemical data in sediments by XRF for environmental change research: A case study of a sediment core from the Ba Lat estuary.

Thu, 02 Oct 2025 00:00:00 +0700

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.

Research on late Devonian – early Carboniferous deep-water sedimentary rocks in Central Vietnam: stratigraphic and geotectonic implications

Thu, 02 Oct 2025 00:00:00 +0700

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.

Application of artificial intelligence in geophysical anomaly analysis from electromagnetic data

Thu, 02 Oct 2025 00:00:00 +0700

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.