Geita Gold Mine, Tanzania
The Geita open pit gold mine is 80km south-west of the town of Mwanza in the north-west of Tanzania and is 100% owned by AngloGold Ashanti.
It is the biggest of the group’s eight open-pit mines in Africa and is its only operation in Tanzania.
Prior to April 2004, the mine was managed under the joint venture agreement between Ashanti and AngloGold. Since the merger of these businesses Geita is now a wholly owned subsidiary.
In 2007, Geita produced 327,000oz of gold, equivalent to 6% of group production.
Operations at Geita are slowly improving year-on-year following the more than 50% fall in production for 2006 to 308,000oz. Production for 2007 was 6% better at 327,000oz, while the average grade of ore processed increased from 1.68g/t in 2006 to 2.01g/t in 2007.
Open pit operations commenced in 2000 with recent studies indicating the potential for underground operations.
Geology and reserves
The Geita gold deposit is an Archaean mesothermal orebody, largely hosted in a banded ironstone formation (BIF). Mineralisation is found where auriferous fluids, which are interpreted to have moved along shears often on BIF-diorite contacts, reacted with the BIF. Some lower-grade mineralisation can occur in the diorite as well (usually in association with BIF-hosted mineralisation). Approximately 20% of the gold is hosted in the diorite. As of 31 December, 2007, AngloGold Ashanti reported Geita as having total mineral resources of 109,290kt, with total reserves of 67,989kt.
Mining and processing
Geita is a multiple open-pit operation with underground potential, which is currently serviced by a 6Mtpa carbon-in-leach (CIL) processing plant. Standard open-pit mining methods are employed: hard overburden is drilled and blasted, hydraulic excavators are used to load waste material into a fleet of 100t dump trucks exposing the gold-bearing ore material which is directed to the processing plant.
Production and grades have started to improve at Geita after a disappointing 2006. AngloGold Ashanti projected that gold production at Geita would increase to between 330,000oz and 340,000oz at a cost ranging from $605/oz to $615/oz.
The production problems were made worse by the collapse of part of the Nyankanga pit sidewall during the first quarter of 2007, which covered a portion of the higher grade orebody.
The collapse of the Nyankanga pit in the first quarter delayed access to the higher grade exposed ore in this area and resulted in the mining plan for the year being revised.
Production, and tonnage throughput in particular, was further hindered by wet ore, mill lubrication problems and a full-scale shutdown of the primary crusher for planned maintenance as well as damage to the ball mill discharge which led to reduced processing plant availability.
The resumption of ore mining from Nyankanga in the third quarter of 2007 led to a marked improvement in production over that period, however harder material and poor grades saw a reduction in plant throughout which flowed through to reduce gold throughout in Q4.
AngloGold Ashanti reported a 9% fall in cash costs to $452/oz with the increased level of production. Reduced expenditure on equipment re-builds and contractor services also contributed to the containment of costs. Capital expenditure for 2007 was $27m (2006: $67m) which was spent largely on the replacement of heavy earthmoving equipment.
AngloGold Ashanti has undertaken numerous studies of the Geita site and surrounding areas and identified.
At the end of 2007 advanced grade control drilling had begun at the Star & Comet project in preparation for the start of mining in the second quarter of 2008. Exploration activities during 2007 focused on strike additions at Area 3 and the detection of regolith gold anomalies below laterite cover through air core drilling.
Early results suggest the potential for an approximately 1.7km zone of mineralisation on strike at Area 3. The regolith programme identified a 2km gold in saprolite anomaly that requires follow-up drilling.
The results of a scoping study into the underground potential at Nyankanga and Geita Hill are forthcoming are yet to be finalised.
In March 2009, Lake Victoria Mining Company provided an update on drilling progress at its Geita prospect. The project shares an 11km northern boundary with AngloGold’s Geita mine.
Exploration reverse circulation drilling started in January 2009. Four major target locations have been tested. There are five major target locations.
A total of 6,000m of drilling, with anticipated pre-drilling hole depths of 150m, will be covered by the Geita programme.
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