Abstract
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.