The Chirano gold deposits can be described as epigenetic, mesothermal gold deposits, demonstrating a strong structural control and a brittle structural style. They are hosted by mafic volcanics and granite, ranging from stacked parallel veinlet systems to vein stockworks, breccias and cataclasites. The veinlets are dominated by quartz, with lesser ankerite, calcite, albite and traces of pyrite and hematite. The deposits show varying degrees of ankerite-albite-muscovite-pyrite alteration superimposed on earlier hematite alteration.

The deposits occur close to a major fault (the Chirano Shear), and is considered likely that any new deposits found will also be closely associated with faulting. In particular, individual deposits are often closely associated with small dextral jogs in the host structure. Although the currently known gold deposits are in granite, there are also strong gold anomalies in Birimian metasediments elsewhere within the mine area, which require concerted follow-up exploration.

The deposits range in strike length from 150 meters to 700 meters, and range in thickness from a few meters over 70 meters. They vary from rather tabular (Obra, Sariehu, Suraw) to more pipe-like (Tano and Akoti North) morphologies. The longer, the more tabular bodies generally comprise at least two shorter lenticular shoots, such as the Obra main and north lenses. These lenses may be separated by a small dextral jog such as those at Obra and Sariehu. Within th ........

Chirano is an open-pit and underground operation located in southwestern Ghana, approximately 100 kilometres southwest of Kumasi, the country’s second largest city. Chirano includes the following deposits: Akwaaba, Kolua, Suraw, Akoti, Paboase, Tano, Obra, Sariehu and Mamnao.

The Chirano gold mine started production in October 2005 with a surface mining operation from three open pits. Surface operations stopped at the end of the second quarter of 2017. Since then, gold production has been primarily from three underground mining operations, until the second quarter of 2019 when surface operations re-commenced. To date, three additional underground mines have been added bringing the total number of underground mines operated by Chirano to six.

Chirano mines are utilizing longitudinal modified sub-level caving mining method and a long hole open stoping mining method with waste rock backfill.

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Processing capacity is 3.5 Mt/a using a conventional three stage crushing circuit, followed by primary and secondary ball mills for fine grinding. After grinding and 24 hours of cyanide leaching, a CIL circuit extracts gold in solution to activated carbon. A conventional carbon elution and electro-winning circuit recovers gold which is then smelted to gold doré for shipment to international gold refiners. Gold recovery using the above described process istypically 91 to 92%.

Ore is transported to the plant by truck and deposited onto the Run-Of-Mine pad (ROM). Crushing of the ore takes place in three stages; a primary jaw crusher that reduces ore to less than 150mm; a secondary cone crusher and two tertiary cone crushers. Secondary crushed ore is conveyed to a screening section before two tertiary stage crushers.

Crushed ore is transferred from the fine ore bin at a controlled rate to the primary ball mill (a converted SAG mill) by means of a conveyor belt. Wat ........