Vietnam’s bauxite bounty

Vietnam is rich in bauxite resources. The deposits and occurrences are distributed over wide areas, especially in north-east Bac Bo and the Highlands (Tay Nguyen). Two types of bauxite deposits are identified; one type caused by residual weathering of Permian sediments, and the second being lateritic bauxite formed via weathering of Neogene to early Quaternary basalts.

This article aims to evaluate the general properties and distribution of Vietnam’s bauxite resources and their potential in the development of a Vietnamese aluminium industry up to 2020, which is currently focused on the exploitation of bauxite deposits in the Highlands (Tay Nguyen) and establishment of aluminium production.

Table 1: Quality and reserve of bauxite deposits in Lang Son province

The bauxite ores appear either in deluvial placer ore or as primary ore in limestone. The deluvial ore bodies occur in various sizes, from hundreds to thousands of metres thick to tens of metres thick. The ore recovery ratio changes considerably, but usually from 0.9 to 1.1 tonnes per 1m³ blocks.

In the outcrops of primary ore, the thickness of the bauxite seam ranges from 10 to 30 metres, even up to 50 metres in some places. Bauxite lies on the eroded surface of massive limestones of Permian age, hence mining is rather easy. The main mineral composition consists of monohydrate bauxite (boehmite and diaspore). Analysis of bauxite samples confirmed the presence of small amounts of gallium, vanadium, chromium, nickel and cobalt.

In this region, there are three main areas of bauxite deposits, namely Lang Son, Cao Bang and Ha Giang (Dong Van plateaux). Bauxite is largely found in the form of deluvial concentrations of boulders, blocks or broken pieces mixed with reddish soil along the valleys intercalated in the karstic mountain blocks of limestone.

In Lang Son province, there are 36 bauxite deposits and occurrences with a total reserve of 28.787m tonnes, grading 44.7-58.8% Al₂O₃, divided into three deposit groups as: Lang Son, Bang Mac and Bac Son. Three deposits in the Lang Son group, named Ma Meo, Dong Dang and Tam Lung, have been prospected in detail by a cooperation project with Hungary during 1966-67 (see Table 1).

In Cao Bang province, 35 deposits and occurrences of bauxite have been evaluated with a total reserve of 76.825m tonnes. These have been divided into three deposit groups, known as Tap Na, Ha Quang and Quang Hoa.

In Ha Giang province, 27 deposits and occurrences of bauxite have been evaluated, with a total reserve of 49.323m tonnes, grading 35-45% Al₂O₃ in the Dong Van stone plateaux (which was recognised by UNESCO as a Global Geopark in 2010).

Bauxite has also been found in Lai Chau and Dien Bien, Nghe An province, but these areas have not yet been evaluated in detail.

The Lo Son bauxite deposit in Hai Duong province, which has a total reserve of 122,000 tonnes, grading 52% Al₂O₃, was exploited by developers from Japan during 1937-1943. At present, the Hai Duong grindstone plant has mining for production of synthetic corundum.

The total bauxite reserve of the north-east Bac Bo region is 155.657m tonnes.





Weathered bauxite in south Vietnam

Systematic studies on weathered bauxite have been undertaken since 1975, right after the liberation of south Vietnam. Before 1975, J. Berrange documented the existence of lateritic bauxite in weathered basalt, but no exploration had been carried out.

From 1976 to 1980, a geological survey of south Vietnam was undertaken, identifying all lateritic bauxite deposits. Following this, geological exploration was carried out within the framework of the cooperation project with COMECO (CSSR). This was undertaken in Dac Nong, Bao Loc, Phuoc Long, Konplong, Van Hoa and Quang Ngai.

Bauxite deposits in Dac Nong and Bao Loc areas, which are the most promising in terms of large reserves, good ore quality and condition, have been prospected in detail.

Ore quality depends on grain size proportions. The average grade of crude ore is 36-39% Al₂O₃, 5-9% SiO₂, 25-29% Fe₂O₃ and 4-9% TiO₂, with a siliceous modulus (MSi) of 5-20.

Although this ore is of medium quality, it can be upgraded by simple washing (plus 1mm) to a commercially saleable product of 44-53% Al₂O₃ with silica, iron and titanium dioxide proportionally reduced. The main mineral composition is trihydrate, gibbsite and goethite, with smaller amounts of carbonate, ilmenite and anatase etc. The general distribution of the bauxite makes it easy to mine with a small layer of soil covering the deposits.

After the results of the geological investigation and prospecting, which occurred up until 1990, it was found that the total reserve of lateritic bauxite in south Vietnam is 4.708bn tonnes, in which the Quang Nam-Quang Ngai is 1.494m tonnes; Phu Yen is 33,230 tonnes; Gia Lai-Kon Tum is 367.39m tonnes; Dac Nong is 2.299bn tonnes, Lam Dong is 788.4m tonnes; and Binh Phuoc-Dong Nai is 1.257bn tonnes (see Table 2).

In the Dac Nong deposit area there are 12 deposits, with primary exploration carried out at six deposits; Quang Son, Nhan Co, Gia Nghia, North Gia Nghia, Dak Song and Trung Duc. The total reserve is 2.299bn tonnes; concentrated ores have a reserve of 941.38m tonnes with an average Al₂O₃content of 48.3%, SiO₂ content of 2.6%, Fe₂O₃ at 18.93%, MSi at 18.5% and a recovery of 44.6%.

Table 2: Lateritic bauxite deposits in south Vietnam

The draft ‘Zonation project for exploration, exploitation and production of aluminium up to 2020, vision to 2025 of Vietnam’ was drawn as following:

Vietnam’s total output of aluminium and aluminium hydroxide to 2020 (and vision to 2025) is forecast to reach 6.3m tpa and 650,000 tpa, respectively.

Conclusions

In past 50 years, the geological association of Vietnam has made significant achievements in the discovery and evaluation of the country’s bauxite deposits. Two major types of industrial bauxite deposit have been found Ð the weathered deposits of lateritic bauxite and residual bauxite from re-deposition Ð of which the lateritic bauxite of the Highlands have a great reserve.

Up to now Vietnam’s geological branch has identified 147 deposits and occurrences, of which five are large, 12 are moderate and 43 are small deposits. The country’s total reserves of bauxite are 4.863bn tonnes, making Vietnam one of the largest potential sources of bauxite in the world.

Some deposits or deposit groups have been prospected in detail and on basis of gathered data, it is possible to estimate the feasibility of bauxite exploitation and aluminium production. The draft on general scheme of Vietnam’s development of an aluminium industry was approved, for which the large projects will require cooperation and investment from foreign countries.

In order to the target to manufacture of 6.3m tpa of aluminium by 2020, and to strengthen domestic companies, we call upon and welcome foreign companies investing in the development of Vietnam’s aluminium industry.

References:

Dinh Van Dien et al., 1979. Mineral resources of North Vietnam, Volume 4, Non-ferrous, precious, rare metals. General Department of Geology, Ha Noi.

Le Van Trao, Pham Van Man, 1995. Bauxites of Vietnam. Proceedings of the third Geological Conference on occasion of the 50^th Anniversary of the Geological organisation of Vietnam, Volume II, Minerals, p.85-97, Geological Survey of Vietnam, Ha Noi.

Nguyen Duc Hue, 2006. Study of scientific base and practice for constructing the norm of reserve and resource ranking for bauxite mineral resource of Vietnam. In: Record of science Ð technological projects of natural resources and environment Branch in 2002-2006. Ministry of Natural resources and Environment, Ha Noi.

Nguyen Xuan Ba, 2006. Global situation on bauxite mining and alumina - aluminium production and development orientation for aluminium industry in Vietnam. Proceedings of 17^th National Conference of mining science and technology, Vietnam Association of mining Science and Technology, Ha Noi.

Contributor: Dr Tran Kim Phuong, Vietnam Institute of Geosciences and Mineral Resources (VIGMR), Thanh Xuan, Hanoi, Vietnam. phuongicf@gmail.com