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Obuasi mine, Ghana

29th July 2016

By: Sheila Barradas

Creamer Media Research Coordinator & Senior Deputy Editor

  

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Name: Obuasi mine.

Location: The mine is located in the Ashanti region of Ghana about 320 km north-west of the capital Accra.

Controlling Company: AngloGold Ashanti.
Brief Description: Mining operations at Obuasi have primarily been underground to a depth of 1 500 m. Following a two-year review of operational efficiencies, the mine was placed on limited operating status at the end of 2014.

Brief History: Underground production at Obuasi was continuous from 1897 to 2014. At the end of 2014, production was temporarily suspended while decline development continued and a feasibility study was progressed.

A phase of openpit mining was conducted from 1988 to 2000, with small intermittent openpit mining beyond that period.
Products: Gold.
Geology/Mineralisation: Obuasi is located within the Obuasi concession area, in south-western Ghana, along the north- easterly-striking Ashanti volcanic belt. The deposit is one of the most significant Proterozoic gold belts discovered to date. The Ashanti belt predominantly comprises sedimentary and mafic volcanic rocks, and is the most prominent of the five Birimian Supergroup gold belts found in Ghana. The belt is a 300 km wrench-fault system that propagated from Dixcove in the south-west to beyond Konongo in the north-east.

Gold mineralisation is associated with and occurs within graphite-chlorite-sericite fault zones. These shear zones are commonly associated with pervasive silica, carbonate and sulphide hydrothermal alteration, and occur in tightly-folded Lower Birimian schists, phyllites meta-greywackes and tuffs along the eastern limb of the Kumasi anticlinorium.

Reserves: Proven and probable mineral reserves as at December 31, 2015, were estimated at 19.55-million tonnes, grading 9.14 g/t of gold. Mineral reserves below infrastructure were estimated at 2.26-million tonnes, grading 21.57 g/t of gold.
Resources: Exclusive mineral resources as at December 31, 2015, were estimated at 99.19-million tonnes, grading 7.53 g/t of gold. Mineral resources below infrastructure are estimated at 11.61-million tonnes, grading 13.54 g/t of gold.
Mining Method: Mine designs are done to delineate development layouts and production stopes by taking into consideration economic cutoff grade and geotechnical design parameters for each mining block, mining level and section. The underground development system extends to a depth of 1 500 m from surface. Mining levels are situated between 15 m and 20 m intervals, with major levels between 30 m and 60 m intervals. Underground production has recently been by open-stope mining – longitudinal and transverse – and sublevel caving methods with future designed production envisioned to take place using longhole open stope or underhand drift-and-fill mining methods.

Major Infrastructure and Equipment: Existing infrastructure includes a 2.4-million-tonne-a-year processing plant with flotation and BIOX; underground development, hoisting shafts and associated infrastructure; power and water reticulation, office complexes, workshops and company housing estates. The current tailings storage facility is close to closure and plans for a new dam have been prepared for submission to government authorities.

The current processing plants can treat oxide and fresh material. The main plant is configured for flotation and BIOX treatment that is required for the underground refractory sulphide ore type.

Prospects: Underground production was suspended in late 2014, with activities restricted to production from developed stopes and the processing of surface mining tailings. AngloGold remains committed to finding long-term solutions for the redevelopment of Obuasi.
A feasibility study will be finalised during 2016, when the schedule for the potential restart of underground production can be determined.

Contact Person: Senior VP investor relations and group communications – global, Stewart Bailey.

Contact Details:
AngloGold Ashanti,
tel + 27 11 637 6000,
email sbailey@anglogoldashanti.com, and
website http://www.anglogoldashanti.com.

Edited by Tracy Hancock
Creamer Media Contributing Editor

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