Bauxite mining is generally a relatively shallow, surface mining operation which removes a near surface 2-10 m layer of aluminium-rich material (Bardossy and Aleva 1990; Hickman et al. 1992). Bauxite develops over almost all types of geology but over one-third of the world's bauxite is formed on sedimentary rocks. Lateritic bauxite comprises 85 % of the total world tonnage of bauxite mined (Bardossy and Alena 1990). Karst-bauxite is also quite extensive, including large areas of central and northern China but a smaller percentage (15 %) of bauxite is mined from them. A third form of bauxite, detrital bauxites are of minor importance globally, although deposits are found in northeast China and the Korean peninsular (Bardossy and Aleva 1990; Hickman et al. 1992).
Bauxite ore, which is mined for its aluminium oxide content, varies from relatively low grades deposits in the Darling Range of Western Australia which contain 30-40 % aluminium oxide to higher grades elsewhere which contain 40-60 % aluminium oxide (Bardossy and Aleva 1990; Hickman et al. 1992). For rehabilitation, the most significant consequence of variation in grade is that much larger areas are disturbed by mining for low grade ore, and larger amounts of residue are generated for disposal. Apart from variation in aluminium oxide concentrations in the ore, iron oxide and silicate levels also vary significantly which affects not only the extraction process but also the mineralogy and properties of the residues.
Apart from the Darling Range deposits in southwestern Australia at 31-34 oS, most economic reserves are located between 25 oN and 20 oS (Bardossy and Aleva 1990). Globally, the five major bauxite provinces are: South American Platform province; West African province; Indian Province; Southeast Asia province and; North and West Australian province (Bardossy and Aleva 1990). Clearly within this range of latitudes, mining for bauxite occurs in a wide range of climates (Table 1). One of the world's major bauxite mining operations is located in the southwest of Western" Australia with a mediterranean climate (Nichols et al. 1985; Marshall 1991). Deposits such as those in Weipa, and Gove in northern Australia are in regions with a semiarid tropical climate. Those in Brazil and Jamaica experience more humid tropical climates. Climatic constraints for rehabilitation therefore will differ considerably between these areas in ways which are discussed below.
|Publication Type:||Conference Paper|
|Murdoch Affiliation:||School of Environmental Science|
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