Mexico

Bolivar Mine

Click for more information

Categories

Overview

Mine TypeUnderground
Commodities
  • Copper
  • Silver
  • Gold
  • Zinc
Mining Method
  • Room-and-pillar
  • Sub-level stoping
  • Longhole stoping
Production Start... Lock
Mine Life2027
ShapshotOn April 16, 2021, the Company announced the approval by its Board for an investment of $28 million for the construction of a magnetite processing plant at the Bolivar Mine.

Although the Board approved this investment, the construction of the proposed magnetite processing plant has yet to take place and there is no indication that such construction shall take place in the foreseeable future.
Related AssetBolivar Expansion Project

Owners

SourceSource
CompanyInterestOwnership
Sierra Metals Inc. 100 % Indirect
Dia Bras Mexicana SA de CV (operator) 100 % Direct
Sierra Metals Inc. owns 100% of the Bolivar Mine through Dia Bras Mexicana.

Contractors

Lock

- subscription is required.

Deposit type

  • Skarn
  • Carbonate replacement

Summary:

The Bolivar deposit is a Cu-Zn skarn and is one of many precious and base metal deposits of the Sierra Madre belt, which trends north-northwest across the states of Chihuahua, Durango and Sonora in northwestern Mexico (Meinert, 2007). The deposit is located within the Guerrero composite terrane, which makes up the bulk of western Mexico and is one of the largest accreted terranes in the North American Cordillera. The Guerrero terrane, proposed to have accreted to the margin of nuclear Mexico in the Late Cretaceous, consists of submarine and lesser subaerial volcanic and sedimentary sequences ranging from Upper Jurassic to middle Upper Cretaceous in age. These sequences rest unconformably on deformed and partially metamorphosed early Mesozoic oceanic sequences.

The Piedras Verdes district is made up of Cretaceous andesitic to basaltic flows and tuffs intercalated with greywacke, limestone, and shale beds. Cu-Zn skarn mineralization is in carbonate rocks adjacent to the Piedras Verde granodiorite. Mineralization exhibits strong stratigraphic control and two stratigraphic horizons host the bulk of the mineralization: an upper calcic horizon, which predominantly hosts Zn-rich mineralization, and a lower dolomitic horizon, which predominantly hosts Cu-rich mineralization. In both cases, the highest grades are developed where structures and associated breccia zones cross these favorable horizons near skarn-marble contacts.

The Bolivar deposit is classified as a high-grade Cu-Zn skarn and exhibits many characteristics common to this deposit type (Meinert, 2007). The term skarn refers to coarse-grained calcium or magnesian silicate alteration formed at relatively high temperatures by the replacement of the original rock, which is often carbonate-rich.

Skarn alteration and mineralization at the Bolivar property is hosted primarily in a package of sedimentary rocks that occur as a layer or lens within the LVS (Reynolds, 2008). All sedimentary units have undergone low grade metamorphism. The lowermost sedimentary horizon observed is a dolostone which ranges from 24 m to 40 m in thickness. The lower part of the dolostone horizon is interlayered with siltstone. To the south, progressively less of the sedimentary sequence is cut out by granodioritic intrusive rocks and the dolostone is observed to be underlain by a siltstone horizon. The lower siltstone unconformably overlies the LVS. The dolostone is overlain by a discrete layer of siltstone. The average thickness of this siltstone unit is 12 to 30 m. Horizons of argillaceous dolostone (50 m thick) and argillaceous limestone (9 m thick) are above the siltstone marker layer. The uppermost sedimentary horizon is a limestone with local chert and argillaceous laminations. The vertical thickness of this horizon varies considerably in cross-section (108 to 173 m) and this variation is attributed to paleo-topographic relief. The upper contact of the limestone is an unconformity with the LVS.

The most important igneous rocks on the property are the Piedras Verde granodiorite and related dikes and sills. All are slightly porphyritic but none are a true porphyry. The Piedras Verde granodiorite exhibits a range of textural variations and compositions. The average composition is very similar to plutons related to Cu skarns (Meinert, 2007). There is no indication of an Au association.

The dikes locally cut the granodiorite, have planar, chilled contacts, and are generally finely crystalline. Both their texture and crosscutting relations suggest that the dikes are younger and shallower than the granodiorite. Both granodiorite and andesite dikes have alteration and locally skarn, along their contacts. In addition, endoskarn affects both the granodiorite and in rare cases, the andesite dikes. Thus, these rocks are older than or at best coeval with alteration/mineralization. The presence of skarn veins cutting an andesite dike is clear evidence that at least some skarn is later than at least some of the andesite dikes. A closer association of granodiorite with skarn alteration and mineralization is suggested by local K-silicate veining of the granodiorite and the zonation of skarn relative to this contact.

Mineralization at the Bolivar property is hosted by skarn alteration in carbonate rocks adjacent to the Piedras Verde granodiorite (Meinert, 2007). Orientations of the skarn vary dramatically, although the majority are gently-dipping. Thicknesses vary from 2 m to over 20 m. Skarn mineralization is strongly zoned, with proximal Cu-rich garnet skarn in the South Bolivar area, close to igneous contacts, and more distal Zn-rich garnet+pyroxene skarn in the northern Bolivar and southern skarn zones near El Val. The presence of chalcopyrite+bornite dominant skarn (lacking sphalerite) in the South Bolivar area, along with K-silicate veins in the adjacent granodiorite suggests that this zone is close to a center of hydrothermal fluid activity. In contrast, the main Bolivar Mine is characterized by Zn>Cu and more distal skarn mineralogy such as pyroxene>garnet and pale green and brown garnets.

Alteration is zoned relative to fluid flow channels. From proximal to distal, the observed sequence is: red-brown garnet to brown garnet with chalcopyrite ± bornite ± magnetite to green garnet ± pyroxene with chalcopyrite + sphalerite to massive sulfide (sphalerite ± chalcopyrite ± galena) to marble with stylolites and other fluid escape structures.

Mineralization exhibits strong stratigraphic control and two stratigraphic horizons host the majority: an upper calcic horizon, which predominantly hosts Zn-rich mineralization, and a lower dolomitic horizon, which predominantly hosts Cu-rich mineralization. In both cases, the highest grade are developed where fault or vein structures and associated breccia zones cross these favorable horizons near skarn-marble contacts. Meinert (2007) suggested that hydrothermal fluids moved up along the Piedras Verdes Granodiorite contact, forming skarn and periodically undergoing phase separation that caused brecciation. Zones of breccia follow faults like the Rosario, Fernandez, and Breccia Linda trends as well as nearly vertical breccia pipes such as La Increible.

Reserves

Lock

- subscription is required.

Mining Methods

Lock

- subscription is required.

Comminution

Crushers and Mills

Lock

- subscription is required.

Processing

Lock

- subscription is required.

Production

CommodityProductUnits2023202220212020201920182017
Copper Equivalent Metal in concentrate k lbs 00000000000000000000000000000021,32318,338
Copper Metal in concentrate k lbs 0000000000000000000017,22715,056
Silver Metal in concentrate koz 000000000000452327
Gold Metal in concentrate oz 00000000000000003,9682,880
Silver Equivalent Payable metal koz 000000003,6232,920
Copper Equivalent Payable metal k lbs 000000000019,18317,747
Zinc Equivalent Payable metal k lbs 000000000043,64437,914
Silver Equivalent Metal in concentrate koz
^ Guidance / Forecast.

Operational metrics

Metrics202220212020201920182017
Daily processing rate 00000000000000002,948 t2,535 t
Daily processing capacity 00000000000000003,600 t3,000 t
Tonnes processed 0000000000000000000000000001,031,750 t887,237 t
Daily ore mining rate 0000

Production Costs

CommodityUnits202320222021202020192018
Cash costs (sold) Copper Equivalent USD 000 000 000 000 1.73 / lb   1.44 / lb  
Cash costs (sold) Zinc Equivalent USD 000 0.72 / lb   0.63 / lb  
Cash costs (sold) Silver Equivalent USD 000 10.3 / oz   7.61 / oz  
All-in sustaining costs (sold) Copper Equivalent USD 000 000 000 000 2.86 / lb   2.13 / lb  
All-in sustaining costs (sold) Zinc Equivalent USD 000 1.19 / lb   0.94 / lb  
All-in sustaining costs (sold) Silver Equivalent USD 000 17 / oz   11.3 / oz  
^ Guidance / Forecast.

Operating Costs

Currency2022202120202019201820172016
Total operating costs ($/t milled) USD 52.1  32  24.3  29.4  27.7  24.9  24.4  

Financials

Units2023202220212020201920182017
Capital expenditures (planned) M USD  ....  Subscribe
Sustaining costs M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 2   11.1  
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 14.1   15.6  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 52.5   44.9  
Gross profit M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 8.2   6.1  
After-tax Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe -3.6   -3.2  
EBITDA M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 11   11.9  

Heavy Mobile Equipment

Lock

- subscription is required.

Personnel

Mine Management

Source Source
Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Jun 1, 2023
....................... Subscription required ....................... Subscription required Subscription required May 31, 2023
....................... Subscription required ....................... Subscription required Subscription required May 31, 2023
....................... Subscription required ....................... Subscription required Subscription required Jun 1, 2023

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2022
Subscription required Subscription required Subscription required 2021
Subscription required Subscription required Subscription required 2020
Subscription required Subscription required Subscription required 2019

Aerial view:

Lock

- subscription is required.