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Sepon mine, Laos
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30th November 2007
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Name: Sepon mine.

Location: The Sepon copper mine is situated 40 km north of the town of Sepon, in Savannakhet province, south-central Laos.

Brief history: Copper was discovered at Sepon shortly after the discovery of gold. Feasibility studies into the development of the copper project were undertaken in 2002 and construction began in 2003.The operation was commissioned in 2005, with the first copper cathodes produced in March that year.

Brief description: The Sepon copper mine is situated at the same site as the gold operation, and the copper processing plant is located immediately adjacent to the gold plant.

Products: Copper.

Mining method: Openpit.

Reserves: As at June 30, 2006, Sepon mine had a proven reserve of 11-million tons with a 4,68% copper grade and a probable reserve of 3,8-million tons with a 6,11% copper grade.

Resources: As at June 30, 2006, Sepon mine has a total measured resource of 21,7-million tons at a grading of 0,2 g/t, and indicated resource of 7-million tons at a grading of 0,23 g/t and an inferred resource of 48-million tons at a grading of 0,2 g/t.

Geology: The Sepon mineral district stratigraphy comprises Devonian to Carboniferous-aged continental fluvial and shallow-to-deep marine sediments, deposited in a half-graben basin. The sedimentary package has been divided into nine lithology based formations. The dominant fault directions are north-west parallel to the Truongson fault system and east-west parallel to the basin-bounding faults. The copper mineralisation covers a variety of primary and secondary styles. Along the contacts of the intrusive stocks, copper skarns are developed, while outbound of the skarn front, lower temperature silica-sulphide replacement of carbonate rocks is common. Weathering and mobilisation of the primary mineralisation has given rise to a number of secondary ore types. The Khanong copper deposit is a near-surface high-grade supergene-derived chalcocite and oxide copper resource derived from the weathering of a replacement style, semimassive sulphide body, hosted by shallow dipping, highly sheared carbonated rocks.

Major infrastructure and equipment: The Sepon copper mine includes an ore, atmospheric leach, solvent extraction electrowinning copper processing plant. The chalcocite and other copper minerals go through a two-step process comprising an atmospheric leach and subsequent pressure oxidation circuit. The majority of the copper minerals are extracted into a solution using a sulphuric acid/ferric sulphate leach medium, under controlled conditions, in a series of agitated open tanks. The dissolved copper is then recovered in a counter-current decantation thickener circuit, and the final wash liquor is treated in a solvent extraction circuit to extract the copper, which is then electrowon to produce copper cathodes. The residue from the leaching process is subjected to flotation to separate any remaining sulphide. This material will then be releached at elevated temperatures and pressures in an autoclave to extract residual copper.

Prospects: Studies to investigate increasing the processing capacity are underway at the Sepon copper mine. The mine’s resource development programme includes further drilling to extend and close off the Khanong deposit and drilling and feasibility studies to fully assess the Thengkham North and South deposits.

Controlling company: Oxiana (100%).

Contact person: Richard Hedstrom, investor relations.

Unique features: The Sepon copper mine is the most modern and technologically advanced in Asia.

Contact details:
Tel: +61 3 8623 2200
Fax: +61 3 8623 2222

Edited by: Laura Tyrer


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