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Ghana
Chirano Mine

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 Location:
94 km SW from Kumasi, Ghana

  Address:
P.O. Box 57
Bibiani
Ghana
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeOpen Pit & Underground
Commodities
  • Gold
Mining Method
  • Truck & Shovel / Loader
  • Sub-level caving
  • Longhole open stoping
  • Dry waste backfill
Processing
  • Smelting
  • Agitated tank (VAT) leaching
  • Carbon in leach (CIL)
  • Carbon adsorption-desorption-recovery (ADR)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life2026
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.
Latest NewsAsante announces update regarding acquisition of the Chirano gold mine     June 1, 2022


Owners

Source: p. 66
CompanyInterestOwnership
Kinross Gold Corp. 90 % Indirect
Chirano Gold Mines Ltd. (operator) 100 % Direct
Chirano Gold Mines Limited (“CGML”) is 90% owned by Kinross with the remaining 10% owned as a carried interest by the Government of Ghana.

Deposit Type

  • Breccia pipe / Stockwork
  • Vein / narrow vein
  • Mesothermal


Summary:

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 the Paboase Bulge there are several parallel lodes, whereas elsewhere along the mineralized horizon there is commonly only a single zone is evident.

Most of the deposits dip steeply to the west, however shallow west, vertical and steep east dips occur locally. The mineralization plunges either directly down dip or steeply northwards. The mineralization demonstrates excellent continuity, there being no known gaps due to oblique faults or dykes.

Unusually flat dips have been noted in short sections of the lode horizon at Mamnao Central (39,850 N to 39,975 N), Obra South (36,850 N to 36,950 N), Sariehu (38,400 N), and Akoti South (34,635 N), however these areas do not demonstrate any spatial relationship with thicker or higher grade mineralized intervals.

In some of the deposits, thicker zones of gold mineralization appear to have formed where nearby parallel lodes have coalesced. Such deposits have a single thick zone in the core of the deposit, which splits into two or three thinner zones along strike. Tano is the best example of this type of deposit geometry.

Deformation.
The deposits comprise fractured, veined, altered and slightly pyritic mafic volcanics and granite. Within each deposit there is generally a positive correlation between the intensity of fracturing and brecciation and intensity of gold mineralization, however the degree of fracturing varies greatly between the deposits.

The gold mineralization at Obra is generally hosted in severely deformed and brecciated granite (cataclasite), whereas much of the Tano lode is less fractured and can be considered more of a stockwork or vein swarm.

At Obra there is clear evidence that brecciation, veining and alteration have been prolonged, or the result of repeated episodes of deformation, and diamond drill core shows a complex array of small scale structures that often appear ambiguous or contradictory. For example, some rock fragments in the Obra cataclasite contain veins that predate the brecciation and later veins cut through the breccia. Fragments of altered and unaltered rock are juxtaposed in some parts of the breccia, implying alteration before deformation, however adjacent fragments show alteration that overprints the brecciation. In addition, stylolites have been observed to cut across the breccia and early veins, but are cut by later veining.

Veining.
All the gold deposits at Chirano contain numerous quartz and ankerite veinlets and there is generally a positive correlation between intensity of veining and elevated tenor of gold mineralization. The majority of observed veining is oriented parallel to the dip of the overall mineralized zone horizon, however veins have also been noted to dip more shallowly to the west, and some deposits have a sub-horizontal vein set in addition to the dominant west-dipping vein set.

The shallowly west-dipping veins have been interpreted to result from 'west-block-up' shearing in the mineralized zone. The veinlets are mostly a few millimeters to a few centimeters thick. More massive vein quartz (sometimes meters thick) occurs locally, usually on the eastern side of a deposit close to a footwall shear and usually carries only low gold grades. This feature has been observed at Sariehu and Tano.

The quartz veins vary in style from early veins (which may be recrystallized, folded, boudinaged, corroded by pressure solution, offset by micro faults or truncated at the edges of clasts) to late quartz veins (which may be undeformed and exhibit evidence of internal zonation such as carbonate crystals lining the vein selvedge). Some veins contain pyrite replacing hematite in the adjacent rock (sulphidation). At Obra the ankerite veins tend to comprise irregular networks, and may have formed early in the paragenetic history.

Sulphide Development.
The deposits contain trace amounts of pyrite, typically 1% or 2% by volume, rarely exceeding 5% by volume. It is noted that the surrounding barren rocks contain lower levels of disseminated sulphides than the mineralized horizon. Mineralogical studies indicate that the pyrite has a very high gold content.

The pyrite may be very fine grained and disseminated throughout the rock mass, as at Obra, or occur as cubic euhedra a millimeter or two in diameter (and rarely larger at Tano and Sariehu). Pyrite may also occur as rare aggregates to a centimeter in size, and has also been observed to form concentrations along stylolites. The quartz-carbonate veins can also contain pyrite, and pyrite has also been noted as an alteration selvedge to the quartz-carbonate veins. Pyrite also occurs disseminated through the altered host to veining.


Mining Methods

  • Truck & Shovel / Loader
  • Sub-level caving
  • Longhole open stoping
  • Dry waste backfill


Summary:

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.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher 1
Cone crusher 2
Pebble crusher 1
Ball mill 3

Summary:

Processing capacity is 3.5 Mt/a using a conventional three-stage crushing circuit, followed by primary and secondary ball mills for fine grinding.


Processing

  • Smelting
  • Agitated tank (VAT) leaching
  • Carbon in leach (CIL)
  • Carbon adsorption-desorption-recovery (ADR)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

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 ........

Recoveries & Grades:

CommodityParameter2021202020192018201720162015
Gold Equivalent Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required92.192.291.490.6
Gold Equivalent Head Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required2.182.442.12.51

Production:

CommodityUnits2021202020192018201720162015
Gold Equivalent oz  ......  Subscription required  ......  Subscription required  ......  Subscription required226,699246,027211,954256,098
All production numbers are expressed as metal in doré.
Subscription required - Subscription is required.

Operational Metrics:

Metrics202120202019201820172016
Ore tonnes mined  ......  Subscription required  ......  Subscription required2,569 kt2,013 kt2,410 kt2,722 kt
Annual milling capacity  ......  Subscription required  ......  Subscription required3.5 Mt3.5 Mt3.5 Mt3.5 Mt
Tonnes processed  ......  Subscription required  ......  Subscription required3,457 kt3,506 kt3,438 kt3,458 kt
Subscription required - Subscription is required.

Reserves at December 31, 2021:
Mineral reserves Cutoff grade: 0.29 to 1.90 g/t Au.

CategoryTonnage CommodityGradeContained Metal
Proven 5,600 kt Gold 1.5 g/t 271 koz
Probable 10,160 kt Gold 2.2 g/t 718 koz
Proven & Probable 15,750 kt Gold 2 g/t 989 koz
Measured 9,206 kt Gold 1.4 g/t 422 koz
Indicated 18,894 kt Gold 1.2 g/t 712 koz
Measured & Indicated 28,100 kt Gold 1.3 g/t 1,134 koz
Inferred 6,048 kt Gold 1.9 g/t 372 koz

Commodity Production Costs:

CommodityUnits2021202020192018201720162015
Cash costs (sold) Gold Equivalent USD  ......  Subscription required  ......  Subscription required  ......  Subscription required 768 / oz 797 / oz 921 / oz 691 / oz
Subscription required - Subscription is required.

Financials:

Units2021202020192018201720162015
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required24   46.6   46.6   30.5  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required286   317.6   258.5   302.3  
Operating Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required-6.2   -27.5   -58   -70.1  
Gross profit M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required-10.5   -21.1   -41.1   -58.3  
Subscription required - Subscription is required


Heavy Mobile Equipment:

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Apr 7, 2022
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....................... Subscription required ....................... Subscription required Subscription required Apr 7, 2022
....................... Subscription required ....................... Subscription required Subscription required Apr 7, 2022
Subscription required - Subscription is required.

Staff:

EmployeesContractorsYear
Subscription required Subscription required 2021
Subscription required Subscription required 2020
Subscription required Subscription required 2019
Subscription required Subscription required 2018
Subscription required Subscription required 2017
Subscription required Subscription required 2016

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2021
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................................... Subscription required 2020
................................... Subscription required 2020
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................................... Subscription required 2019
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................................... Subscription required 2019
................................... Subscription required 2019
Annual Information Form 2018
Financial Review 2018
Management Discussion & Analysis 2018
Press Release 2018
Year-end Mineral Reserves 2018
Annual Information Form 2017
Financial Review 2017
Management Discussion & Analysis 2017
Year-end Mineral Reserves 2017
Annual Information Form 2016
Annual Report 2016
Other 2016
Press Release 2016
Annual Report 2014
Press Release 2014
Technical Report 2009
Subscription required - Subscription is required.

News:

NewsDate
Asante announces update regarding acquisition of the Chirano gold mine June 1, 2022
Asante announces purchase of Chirano gold mine in Ghana April 25, 2022
Asante Gold Enters into Exclusivity Agreement with Kinross Gold to Purchase Chirano Gold Mine in Ghana April 6, 2022

Aerial view:

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