Mexico

Mercedes Mine

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Overview

Mine TypeUnderground
StatusActive
Commodities
  • Gold
  • Silver
Mining Method
  • Mechanized Cut & Fill
  • Overhand Cut & Fill
  • Longitudinal open stoping
  • Split-shooting
  • Room-and-pillar
  • Sub-level caving
  • Sub-level stoping
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Mine Life... Lock
SnapshotOn April 21, 2022, Bear Creek completed its acquisition of the Mercedes Mine.

During 2023, mine planning and development will shift toward higher-grade deposits utilizing cut and fill mining methods, which is expected to support increased production. As infrastructure development in previously shut down operations returns to levels, they will be brought back into production and are expected to significantly increase mill feed grade. The anticipated inclusion of ore from Marianas, San Martin and Rey de Oro during 2023 is expected to improve the overall grade profile as the year progresses.

Owners

SourceSource
CompanyInterestOwnership
Bear Creek Mining Corp. 100 % Indirect
On April 21, 2022, Bear Creek Mining Corp. acquired a 100% interest in the Mercedes gold and silver mine in the state of Sonora, Mexico.

Contractors

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Deposit type

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

Summary:

Gold-silver mineralization on the Mercedes property is hosted within epithermal, low-sulphidation (adularia-sericite) veins, stockwork, and breccia zones. These deposits form on predominately felsic subaerial volcanic complexes in extensional and strike-slip structural regimes. Near-surface hydrothermal systems, including surface hot springs and deeper hydrothermal fluid-flow zones, are the sites of mineralization. Mineral deposition takes place as the fluids undergo cooling by fluid mixing, boiling and decompression.

Eleven individual deposits have been mined or are currently in production, and seven additional deposits have been identified and are currently in the early exploration or drill definition stage. These deposits occur in three main areas: the prolific Mercedes trend – a major vein that hosts the Mercedes, Aida, Barancas, Gap, Laguna and Marianas deposits; the Rey de Oro area that hosts the Rey de Oro and Klondike deposits; and the Diluvio area that hosts the Diluvio, Lupita and San Martin deposits. Additional mineralized zones proximal to existing workings have been identified and are at the exploration or drill definition stage. Mineralization at Mercedes is primarily hosted in epithermal veins and related structures.

The geology of the Mercedes area is dominated by two northwest trending arches, cut by numerous northwest trending high-angle structures, which have exposed older marine sediments and overlying interbedded volcaniclastic sediments and lithic to quartz crystal lithic tuff units.

Over 16.5 km of veins have been identified within or marginal to the andesite-filled basins, which constitute a primary exploration target on the property. Major veins typically trend N30º-70ºW at 60º to 90º dips following the major regional structural pattern. Veins typically dip at greater than 60º, but locally range as low as 25º.A total of 16 low-sulphidation, epithermal vein/stockwork/breccia zones, have been identified on the Mercedes property and have been divided into three sub-district areas.

Mercedes Area (Mercedes-Barrancas)
The Mercedes vein system is the most prominent and continuous mineralized zone identified on the property, consisting of multiple quartz-carbonate veining, traced almost continuously on strike for nearly 3.5 km. The Mercedes fault system consists of numerous anastomosing strands within a zone over 50 m wide, where complex, multi-stage, anastomosing vein/breccia/stockwork zones 1 m to 15 m wide are emplaced in extensional open areas. The vein mineralogy (multiple quartz and carbonate stages) and morphology is quite variable along strike and down dip, where highly brecciated mineralized green-grey sugary to chalcedonic quartz is found cemented by 15% to 80% late stage grey calcite, rhodochrosite, and/or brown-black manganese-iron carbonates.

Klondike Area (Klondike-Rey de Oro)
The Klondike vein system differs from that at Mercedes, in that it forms as a tectonic breccia zone rather than fissure fill vein. The Klondike vein system trends N70ºW, dipping 65º to 80º southwest and is approximately 800 m long, with a maximum vertical range of nearly 300 m and width ranging from 0.5 m to over 50 m. Within the breccia zone, fissure filling veins over 0.5 m wide are rare, while variable lenses of brecciated white to green or grey quartz and abundant manganese carbonates and calcite are found. The overall zone of crackle brecciation and stockwork veining with silicification and strong manganese-iron oxides may be up to 50 m in width.

Diluvio Area (Lupita-Diluvio)
The Lupita vein zone outcrops on the surface for 1,800 m, ranging from 1 m to 5 m in thickness. The vein zone, consisting in multi-stage quartz-carbonate ± adularia veining, follows a contact between the overlying andesite package and underlying felsic package, and extends continuously down dip in places more than 450 m along most of the west half of the surface outcrop, and recent discoveries seem to suggest an extension up to 1 km east of the outcrop. Most importantly, at depths of 200 m to 300 m, the Diluvio zone reveals an extensive zone of multistage quartz-carbonate ± adularia vein breccias, stockwork, and hydrothermal breccia up to 150 m thick that is primarily hosted in the lithic tuff-volcaniclastic sequence. Based on geologic interpretation, it is proposed that mineralized fluid that circulated along the Lupita Fault infiltrated the tuff/volcaniclastic sequence due to its porosity and structural control, creating a large scale stockwork deposit. Diluvio therefore is the only mineral deposit in the district with the lower lithic tuff/volcaniclastic sequence as the primary host.

Mineralogical studies have identified opaque minerals, including iron oxides, pyrite, gold, electrum, stibnite, and rare pyrargyrite, within a gangue of substantial chalcedony, quartz, and carbonate. In addition to hematite, manganese oxides are an important component in some mineralized zones, possibly remnant after dissolution of manganese carbonates. Due to the depth of oxidation, sulphides are rarely observed. The few exceptions include one hole at depth in Klondike (visible galena and sphalerite) and hole L11-133D at Diluvio, which had an unoxidized vein interval containing widely disseminated pyrite, galena, sphalerite, and silver sulphosalts with greater than 500 gpt Ag.

Metallurgical studies have identified the presence of very small quantities of native gold, native silver, electrum, pyrargyrite, stibnite, galena, sphalerite, and chalcopyrite in heavy mineral concentrates. Copper minerals such as malachite and chrysocolla are most common as fracture fillings in breccias at Klondike, although rare specks are also seen in the Mercedes and LupitaDiluvio veins.

The vein mineralogy exhibits:
- Multiple stages of quartz-carbonate and adularia/cemented by quartz pulses, as well as multiple stages of rhodochrosite and siderite pulses and barren calcite;
- A complex paragenesis: hydrothermal brecciation, multiple stages pre-syn and post-mineral tectonic brecciation and faulting;
- Quartz types: cover spectrum in colors, and occurring as chalcedony, sugary, granular and/or coarsely crystalline;
- Textures: crustiform, colloform, banded, lattice etc. (during the boiling);
- Rare specks of visible gold (VG) reported, associated locally to copper carbonates, green quartz, hematite.

The deposit geochemistry reveals that:
- There is no statistical correlation between Au and Ag distribution;
- The Ag:Au ratio is low in all veins, ranging from 5-13:1;
- No lateral or vertical Ag:Au zonation has been identified in any of the vein ore bodies due to complex multi-stage vein deposition and repeated brecciation, which has juxtaposed events;
- The dominant alteration consists of oxidation + chlorite + silicification, with pronounced depth of oxidation, from surface down to 500-600 m, where the veins still appear strongly oxidized;
- There is no evidence of refractory behavior in any of the deposits.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

COVID-19 pandemic impacted production in early 2020 for approximately 3 months.
CommodityUnits202320222021202020192018201720162015
Gold koz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe6069839384
Silver koz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe191309338425383
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.

Operational metrics

Metrics20232021202020192018201720162015
Tonnes milled  ....  Subscribe  ....  Subscribe  ....  Subscribe667,723 t665,522 t683,545 t713,475 t
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe691,267 t699,312 t492,140 t
Daily milling capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe2,200 t2,200 t
Annual production capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe155 koz of gold metal in doré
Annual production capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe594.83 koz of silver metal in doré
Total tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe851,588 t840,084 t
Daily mining rate  ....  Subscribe  ....  Subscribe  ....  Subscribe2,388 t2,302 t
Daily ore mining rate  ....  Subscribe  ....  Subscribe  ....  Subscribe1,894 t1,916 t
^ Guidance / Forecast.

Production Costs

CommodityUnits2023202220212020201920182017
Cash costs (sold) Gold USD  ....  Subscribe  ....  Subscribe 1,034 / oz   908 / oz   706 / oz  
Cash costs (sold) Silver USD  ....  Subscribe 12 / oz   10 / oz   9 / oz  
Cash costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 1,022 / oz **   885 / oz **   676 / oz **  
All-in sustaining costs (AISC) Gold USD  ....  Subscribe  ....  Subscribe 1,240 / oz  
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe 1,263 / oz   1,073 / oz   854 / oz  
All-in sustaining costs (sold) Silver USD  ....  Subscribe 15 / oz   13 / oz   11 / oz  
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 1,260 / oz **   1,060 / oz **   832 / oz **  
^ Guidance / Forecast.
** Net of By-Product.

Operating Costs

Currency2021202020192018
UG mining costs ($/t milled) USD 39.9  43.5  60.7  59  
Processing costs ($/t milled) USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
G&A ($/t milled) USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Total operating costs ($/t milled) USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe

Financials

Units202220212020201920182017
Sustaining costs M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 10.5   7   9.2  
Capital expenditures M USD  ....  Subscribe  ....  Subscribe 18.8   17.4   18.2  
Growth Capital M USD  ....  Subscribe 8.3   10.4   9  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe 83.4   86.1   112.1  
Operating Income M USD  ....  Subscribe -1.2   4.1   34.3  
After-tax Income M USD  ....  Subscribe

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Dec 1, 2023
....................... Subscription required ....................... Subscription required Subscription required Dec 31, 2021
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....................... Subscription required ....................... Subscription required Subscription required Oct 12, 2023
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EmployeesContractorsTotal WorkforceYear
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Aerial view:

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