Ahafo Mine

Newmont
 

Key Facts

Commodity Gold
Location Ghana
Latitude: 7 deg 2 min N
Longitude: 2 deg 21 min W
Map
Satellite Image
Owner Newmont
Production Gold, 17t in 2009
Silver 4.2m oz in 2009
Deposit Type brecciated and hydrothermally altered shear zone
Reserves & Resources 8.4mt @1.17g/t proven reserve
(Dec 31, 2009)
Mining Type Open Pit
Processing Method CIL
Employee approx 3528 employees and contractors
Contact Information C825/26 Lagos Street
East Legon, Accra,
GHANA
Phone: +233 (21) 701 1852
Fax: +233 (21) 701 1855

Overview

The Ahafo operation is located in the Brong-Ahafo Region of Ghana, approximately 180 miles (290 kilometers) northwest of Accra. Ahafo poured its first gold on July 18, 2006 and commenced commercial production in August 2006. Ahafo sold 520,800 ounces of gold in 2008.

Newmont currently operate three open pits at Ahafo with reserves contained in 17 pits. The process plant consists of a conventional mill and carbon-in-leach circuit.

Location

The property is located in the Brong Ahafo region of west-central Ghana, about 30 kilometres south of Sunyani and 290 km northwest of the capital city of Accra.

Geology and Mineralization

The license is located in the Yamfo-Sefwi gold belt, a well-defined zone of many gold occurrences that trends 20 - 30° east of north and stretches northwards from the Ghanaian border with Cote d'Ivoire for a distance of about 200 km. Intruded along this trend are a series of hornblende granodiorites which preferentially exploit a major regional break separating Lower Birimian sediments from Upper Birimian volcanics. The property covers 3 segments of the granodiorite - metasediment contact.

This major break has been mapped for a strike length of 6.4 km in the northern part of the license and for an additional 6.4 km in the southern part and marks the contact between Birimian metasediments to the west and a complex of multiphase granodiorite intrusions to the east. This structure hosts the Yamfo deposit as well as significant mineralization at Kenyase and at Subenso. Thirteen km of the prospective structure occur within the license boundary.

In general, gold mineralization is associated with a brecciated and hydrothermally altered shear-zone of granodiorite lying in thrust/wrench contact with underlying graphitic phyllites of the Birimian Supergroup. The phyllities also contain scattered pods of gold mineralization, but these appear to be limited to a zone lying no more than 20 m from the granodiorite. The thrust contact always dips east at angles varying from 30° to 65°.

Gold mineralization is also associated with a shear zone about 1.2 km east of the granodiorite - metasediment contact that was expressed by a low-level soil geochemical target. The granodiorite hosted shear zone is subparallel to the main trend and dipping from 60° east to sub-vertical.

Geochemical soil sampling identified 8 major gold anomalies, 7 of which are named in alphabetical order Zone A through G, and an eighth zone named Sika Aminaso.

Mining & Operations

Newmont currently operate three open pits at Ahafo with reserves contained in 17 pits. The process plant consists of a conventional mill and carbon-in-leach circuit.

Ahafo are currently mining a number of open pits with the majority of ore coming from the Apensu and Awonsu working areas. A blend of both primary and oxide ore is fed to the mill to balance the head grade and recovery in the leach circuit. Ahafo operate a 54 x 75" gyratory crusher for primary ore and a toothed roll, sizer for oxide ore. This is followed by an SABC circuit comprising a 34 x 16.4ft, 13MW semi-autogenous grinding (SAG) mill in closed circuit with 2, 600kW pebble crushers. SAG milling is followed by a 24 x 39ft, 13MW ball mill in closed circuit with a cluster of 26 inch cyclones. After classification, the milling product is thickened and the overflow is fed to carbon-in-leach tanks.