Peru

Colquijirca (El Brocal) Operation

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Overview

Mine TypeUnderground
Commodities
  • Gold
  • Silver
  • Zinc
  • Lead
  • Copper
Mining Method
  • Sub-level stoping
  • Room-and-pillar
  • Unconsolidated rockfill
  • Cemented (undefined) backfill
Production Start... Lock
Mine Life2033
ShapshotColquijirca is one of the largest producers of Zn Pb-Ag and Cu (Au) in Peru.

El Brocal exploits two adjoining mines: Tajo Norte (Colquijirca), an open-pit operation that produces silver, lead, zinc and copper ores; and Marcapunta, an underground mine that produces copper minerals.

The Tajo Norte is currently undergoing a transition to a “mixed” ore that contains both polymetallic ore and copper ore, intertwined, which makes it very complex to recover them in the shape of commercial concentrates.

The Marcapunta underground mine is progressing according to plan and is expected to reach 9,000 tpd by the end of 2023 with sustained stable copper and gold production and strong economic margins.
Related AssetsMarcapunta Mine, Tajo Norte Mine

Owners

SourceSource
CompanyInterestOwnership
Sociedad Minera El Brocal S.A.A. 38.57 % Indirect
Compania de Minas Buenaventura S.A.A. 61.43 % Indirect
Colquijirca is held within the operating entity, Sociedad Minera El Brocal (El Brocal), of which Buenaventura is a 61.43% owner with the remaining 38.57% ownership controlled by Sociedad Minera EL Brocal S.A.A.

Contractors

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Deposit type

  • Epithermal
  • Vein / narrow vein
  • Porphyry
  • Carbonate hosted

Summary:

The mineral deposits of the Colquijirca district belong to a member of the family of porphyry copper (Cu) related deposits known as Cordilleran deposits. These types of deposits, which are generally formed in the upper parts of a porphyry Cu, are fundamentally characterized by prominent zoning with internal parts that are dominated by Cu and external zones where Zn, Pb and Ag are the main economically-interesting elements. In the case of the Colquijirca district, and specifically the area between the Marcapunta Norte and Colquijirca sectors, such zoning generally consists of three zones, which mineralogically consist mainly of enargite in the internal parts; chalcopyrite in the intermediate parts; and sphalerite and galena in the external parts (El Brocal, 2021).

Due to the advance of stoping over the years, the Colquijirca deposit is currently exposed, which facilitates the geological identification of the Tertiary basin. Asymmetric anticlines and synclines composed of carbonate and detrital rocks, attributed to the Eocene-Oligocene Calera Formation, can be found and considered as the host of mineralization. The deposit also presents volcano-clastic intercalations (ash tuffs), which is evidence of volcanic activity that was contemporaneous to sedimentation. In addition, with the review of 5 drillholes, the Shuco conglomerate sequence of the upper Eocene has been identified in depth, which underlies Lower Calera and overlies in depositional contact with the Mitú sandstones of the Permian-Triassic (Megard, 1978). To the south, at Smelter and Marcapunta, the sequence is uplifted and intruded by domes and dykes of dacitic composition due to the diatreme, which shows strong advanced argillic alteration and is recognized as the focus of mineralization in the mining district.

The Marcapunta diatreme-dome complex, which is exposed in the center of the Colquijirca district (Sillitoe 2000; Bendezú et al. 2003; Sarmiento 2004), is one of a series of Miocene volcanic edifices, including Cerro de Pasco and Yanamate. It consists of multiple lava-dome intrusions of mainly dacitic composition. Injection and explosion breccias and pyroclastic layers, typical of diatreme conduits, are widely recognized at depth. The inward dipping normal fault, located in peripheral areas suggests that the entire edifice collapsed, probably before the main mineralization episodes (Bendezú et al. 2003).

Mineralization
The district hosts two main types of epithermal mineralization: (1) disseminated high-sulfidation Au–(Ag) mineralization, hosted by volcanic rocks from the Marcapunta complex, and (2) sulfide-rich Cordilleran polymetallic deposits hosted in the carbonate rocks of both the Pucará Group and the Pocobamba Formation.

High sulfidation Au-(Ag) epithermal.
Mineralization consists of oxide veinlets and disseminations hosted in vuggy silica. Typical gold and silver concentrations in vuggy silica are on the order of 0.2- 3 and 10-70 g/t, respectively (Vidal et al. 1997) and Ag/Au ratios vary from 10 to 30. The deep parts of the vuggy silica contain unoxidized Au- (Ag) minerals, which are composed of less than 5% of disseminated sulfides by volume, and sulfide veins composed mainly of pyrite-enargite, chalcocite, covellite and sphalerite with the presence of clays, mainly kaolinite, but also smectite and/or illite. The vuggy silica and surrounding quartz-alunite zones, which do not have veinlets, contain minor amounts of Au-(Ag), suggesting that most of the precious metals precipitated during veinlet formation.

Cordilleran Epithermal
A significant feature is the high total sulfide content, which fluctuates between an average 30 and 50% of the volume on average. The most abundant minerals are pyrite, which crystallized during an early silica-pyrite stage, followed by enargite-pyrite and, finally, late-stage chalcocite (Bendezú 2007). The strongly oxidized zones, originally composed of enargite-pyrite, show Ag/Au ratios ranging from 80 to 120, much higher than those found in the Au-(Ag) minerals disseminated throughout Oro Marcapunta (10 to 20). Another important characteristic of the Cordilleran type mineralization in the Colquijirca district is the mineralogical zoning:
1) A Cu- (Au - Ag) core dominated by enargite and generally accompanied by alunite assemblages.
2) An intermediate Cu- (Zn - Pb - Ag - Bi) zone dominated by chalcopyrite, sphalerite and galena; and
3) An external Zn - Pb- (Ag) envelope composed mainly of sphalerite and galena.

Cordilleran veins systematically cut the precious metal veins in the easternmost part of the Marcapunta Oeste project. The quartz-alunite zones developed during the high sulfidation epithermal event contain Au (Ag) veins, which were cut by pyrite-rich veinlets (enargite) generated during the Cordilleran event. In addition, most of the cavities within the vuggy silica contain intergranular enargite fillings from the Cordilleran stage, which in part destroy earlier Au-(Ag) veinlets with quartz-alunite assemblages.

The Colquijirca deposit exposes three zones. The deepest part of the southwest sector of North Pit shows a core of tubular shape, which is essentially constituted by enargite plus variable amounts of pyrite and quartz. This core has an envelope composed of chalcopyrite and variable amounts of tennantite, in addition to sphalerite and galena. In turn, this envelope is surrounded by a relatively extensive zone composed of sphalerite and galena. This last zone, whose largest extension is towards the north of the district, constitutes the bulk of the Colquijirca deposit (North Pit) currently in exploitation. To the south of North Pit, the enargite core extends for more than 2 km becoming thicker and wider as it approaches the Marcapunta volcanic complex.

The sector called Marcapunta Norte, located immediately south of North Pit, is the extension of the Colquijirca deposit. This sector is composed of two internal zones: The first is composed of enargite and that the second of polymetallic nature, i.e., of chalcopyrite, tenantite, sphalerite and galena. Unlike sectors located further south, the Marcapunta Norte sector is characterized by the fact that it has undergone a process of supergene enrichment. This process has generated chalcocite bodies, which have been superimposed to the enargite zone and to a lesser degree, to the polymetallic zone composed of chalcopyrite, tenantite, sphalerite and galena; this formed a sector of relative mineralogical complexity, especially in terms of intergrowths.

The mineralized structure of the Central Upper Mantle is hosted in carbonate rocks of the Middle Member of Calera Formation and has a sub-horizontal stratiform geometry of N160° strike and 06N dip. The structure has an approximate length of 520m, a width of 270 m and an average thickness of 21 m. The occurrence of structures secant to the bedding, such as breccia bodies and veins, is less common.

Mineralogically, the Central Upper Mantle consists essentially of enargite, accompanied by variable amounts of pyrite. Less important phases include luzonite, colusite and an even small quantity of occurrences of chalcocite, tenantite, ferberite and bismuthinite.

The Central Upper Mantle contains enargite-luzonite (Cu3AsS4) with grades varying between 1 and 3% Cu and 0.3 and 1% As. Ag contents vary between 15 and 30 g/t. Some internal sectors of the Central Upper Mantle show gold values between 0.3 and 0.7 g/t. Gangue minerals include quartz, alunite, zunyite and clays, mainly kaolinite, dickite, illite and smectite.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Summary:

Plant 1 – Crushing Stage
Dump trucks deliver fresh ore to a coarse ore bin, which has a capacity of 100 tonnes and is equipped with a rock breaker as well as a stationary 20” opening grizzly. The grizzly’s passing size directly feeds a 47” x 33” jaw crusher operating with a 4” close side setting. The crusher discharge is conveyed to a primary 8’ x 20’ double-deck classification vibrating screen whose passing ½” stream becomes the final product from the crushing plant that is conveyed to a stockpile. The coarse stream from the primary screen feeds a secondary closed-circuit crushing-classification stage consisting of a secondary cone crusher operating with a close-side setting of 47 mm and a secondary doubledeck vibrating screen with a ½” passing size. A fraction of the secondary vibrating screen’s coarse stream feeds a tertiary cone crusher operating in open circuit with a close-side setting of 13mm. Alternatively, the secondary screen’s coarse fraction feeds a second tertiary cone crusher with a close-side setting of 10mm operating in open circuit. Product from both tertiary cone crushers becomes final product from the crushing plant that is conveyed to the stockpile.

The crushing plant’s final product sizing approximately P80= ½” is stored on two covered stockpiles of 6,000 tonnes and 2,000 tonnes each.

Plant 1 – Grinding & Classification
The grinding and classification stage consists of primary grinding in an open circuit followed by a classification stage, where hydrocyclones feed the coarse fraction to a secondary grinding stage that operates in a close-circuit with a multi-deck vibrating screen. A fine ore reclaim system feeds the primary grinding stage, which consists of a 7” x 12” and 550 HP single rod mill operating in open circuit. The rod mill product feeds a hydrocyclone classification stage. The hydrocyclone’s coarse fraction feeds the secondary ball mill consisting of a 16.5” x 23’ and 400 HP ball mill. Ball mill discharge along with hydrocyclones fines stream feeds six multi-deck (5 decks) vibrating screens. The screen’s passing (fine fraction) fraction becomes final grinding product and feeds the flotation stage. The screen’s coarse fraction is returned to the ball mill.

Plant 2 – Crushing, Washing & Classification Stage
Dump trucks deliver material to a coarse ore bin of 300 tonnes capacity equipped with a rock breaker and a stationary grizzly. The grizzly’s passing size directly feeds a roller crusher with 536 hp. The crusher discharge is conveyed to a washing stage consisting of a rotary washing trommel of 3.6 m diameter and 12 m long that discharges onto two doubledeck 10’ x 24’ banana screens operating in series (primary and secondary). Oversize from the primary banana screen feeds a secondary crushing stage operating in open circuit and consisting of a 500 tonnes capacity hopper feeding two parallel gyratory crushers. Discharge from the secondary crushers joins the oversize from the secondary banana screen to feed a tertiary crushing stage consisting of a 400 tonnes hopper feeding a high pressure grinding rolls unit (HPGR). Discharge from the HPGR feeds a single 15’ x 26’ banana screen whose passing stream become final product from the crushing plant that is conveyed to a fines stockpile (overall coarse fraction). The coarse stream from the tertiary banana screen is recirculated back to the tertiary crushing stage.

Passing stream from the secondary banana screen feeds a Four-stage classification plant. The first stage consist of a single primary hydrocyclone whose underflow feeds the secondary classification stage using a multi-deck high frequency vibrating screen. The fines fraction from the primary and secondary stage feed the tertiary stage consisting of 22 hydrocylones. Overflow stream (fines) from the tertiary stage feed the quaternary stage consisting of 16 hydrocyclones. The coarse stream from the secondary stage feeds the fines stockpile. The underflow stream from the tertiary stage feeds primary grinding stage. The underflow from the quaternary stage feeds the fines flotation plant. The overflow stream from the quaternary stage feed a 20 m diameter clarifier whose discharge is split between the fines flotation plants and the ultrafines flotation plant.

Plant 2 – Grinding
The coarse fraction from the washing, crushing and classification stage are stored in a 50,000 tonnes capacity stock pile. Ore is reclaimed from the stockpile using a front-end loader to feed a hopper that subsequenlty feeds the primary grinding stage. The primary grinding stage consists of two ball mills operating in parallel; the first unit is a 9.5’ x 14’ and 600 kW and the second unit is a 20’ x 30’ and 6500 kW. Both ball mills operate in close-circuit with 10 units of a high frequency multi-deck vibrating screen. The passing stream from the classification screens feeds the conditioning tank to the flotation stage.

(Translating from Spanish)
During 2021, Capital shutdowns were carried out at plants to perform repairs and replace critical equipment in order to increase their readiness and reliability.

At Plant 1, the Sandvik CJ412 crusher was replaced with a Metso C-130 on the crushing line. In the grinding section, the #2 Comesa 7x12 mill was replaced and the pumps were relocated to optimize their operation in the #1 grinding and tailings pump positions 18A/B to reduce maintenance costs.

At Plant 2, the washing drum and three Ludovici sieves in the crushing zone were replaced. The HPGR crusher rollers were also replaced in the grinding area, along with the 6500Kw motor, LRS starter, and 20x30 mill speed reducer.

Processing

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Production

CommodityProductUnits2023202220212020201920182017
Gold Metal in concentrate koz 0000000000002123
Silver Metal in concentrate koz 0000000000000000000000003,9024,084
Zinc Metal in concentrate t 00000000000000000000000000000045,59351,511
Lead Metal in concentrate t 00000000000000000000000000020,58220,313
Copper Metal in concentrate t 00000000000000000000000000000046,23145,097
Zinc Concentrate kt 00000000093
Copper Concentrate kt 000000000000183
Lead-Silver Concentrate kt 0000000042
^ Guidance / Forecast.

Operational metrics

Metrics202220212020201920182017
Daily processing rate 0000000000
Daily processing capacity 0000000000000000000020,000 t20,000 t
Tonnes processed 00000000000000000000000000006,633,879 t5,687,581 t
Ore tonnes mined 000000000000006,633,879 t5,687,581 t

Production Costs

CommodityUnits202220212020201920182017
Cash costs (sold) Lead USD 0000 0000 0000 1,230 / t  
Cash costs (sold) Zinc USD 0000 0000 0000 2,071 / t   1,569 / t   1,915 / t  
Cash costs (sold) Copper USD 0000 0000 0000 5,385 / t   5,487 / t   5,119 / t  
Cash costs (sold) Silver USD 000 000 000 12.6 / oz  
Cash costs (sold) Gold USD 0000 0000 0000 1,317 / oz  

Financials

Units202220212020201920182017
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 29.6   61.1  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 333.6   322.7  
Operating Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 36.5   25.8  
Gross profit M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 37   68.3  
Pre-tax Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 26.7   14.3  
After-tax Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 7.6   10.4  
Book Value M USD  ....  Subscribe

Heavy Mobile Equipment

Fleet data has not been reported.

Personnel

Mine Management

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EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2022
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