Cusi Mine Expansion Project

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Mine TypeUnderground
StagePreliminary Economic Assessment
  • Silver
  • Lead
  • Zinc
  • Gold
Mining Method
  • Bench & Fill
  • Room-and-pillar
Backfill type ... Lock
Mine Life... Lock
ShapshotThe Cusi Mine was classied as non-core in the Company’s Q4 2022 results.
Related AssetCusi


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



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Deposit type

  • Vein / narrow vein


Mineral Deposit Mineralization at the Cusi Mine has been variously described as a) low-sulfidation epithermal (Ciesielski, 2007), b) high-sulfidation epithermal (SGS, 2008) and linked epithermal-base metal system (Meinhert, 2006). Meinhert (2006) notes that although shallow (<100 m) historic mining is reported to have encountered grades exceeding 1,000 oz/ton Ag, the veins currently exposed are more base-metal rich than would be expected in an epithermal system. However, Sierra Metals geologists consider the abundance of base metals on the property to be primarily a function of depth of exposure and SRK agrees with this interpretation. Mineralization occurs along narrow fractures containing quartz, sphalerite and galena, and wall rock alteration consists primarily of silicification and the development of clays and iron oxides. The veins contain quartz with crustiform and banded textures typical of epithermal systems. The current geologic model for the Cusi property is described as follows: The country rock on the property consists primarily of felsic volcanics interpreted to represent a caldera with a resurgent dome. Magma is interpreted to have intruded along the Cusi fault, a regional NW-trending, right-lateral strike-slip fault, and a subsequent eruption produced the collapsed caldera and Upper Volcanic Series felsic tuffs. A resurgent dome then arose within the caldera on the western side of the Cusi fault. This dome was then dissected by numerous northeast-trending, left-lateral faults, which acted as conduits for hydrothermal fluids and now host mineralized veins. Two of the vein sets at Cusi are relatively large and have been mapped along strike for nearly a kilometre each. These vein sets, dilatational areas and structural intersections have historically been found to be reliable targets for mineralization. The veins are composed of both wide, continuous areas of mineralization as well as zones of numerous smaller swarms of veins or stockwork veinlets. The mineralization is predominately Ag and Pb-rich with lesser amounts of Au, Zn and Cu present in some areas. SRK is of the opinion that the geologic model developed by Sierra Metals, which focuses primarily on the interpretation of the discrete veins and their related splays/stockwork zones, is appropriate for the deposit type and mining method, and that this has been borne out by a history of production. Mineralization and Alteration Numerous epithermal mineralized veins exist on the property. Typically, these are moderately to steeply dipping to the southeast, southwest, and north, ranging from less than 0.5 m to 2 m thick, and extend 100 m to 200 m along strike and up to 400 m down-dip. Small open pits were typically developed at vein intersections. The epithermal mineralization associated to structures, breccias and filling fractures ranging from less than 1 m to 10 m thick, with a polymetallic filling of Ag-Pb-Zn sulphides and minor contents of copper and variable contents of gold. Crustiform and banded epithermal textures are common, and there is pervasive silicification with some sericite and disseminated pyrite. Zones with argillic alteration are common at the borders of the pervasive silicification, including kaolinite and montmorillonite. Oxidation is characterized by hematite, limonite and manganese oxides. Zones of micro-veinlets and dissemination associated to intense fracturing related to the main structures are observed in the area of Promontorio. In Eduwiges, veins and zones of “stockwork” of quartz with pyrite and silicification alteration of 60 m to 150 m width and 200 m to 250 m extension are observed (Geomaps, 2012). Low-grade mineralized areas exist adjacent to major structures, and they show intense fracturing and are commonly laced with quartz veinlets forming a stockwork mineralized halo around more discrete structures. The country rock in these zones is variably silicified. Pyrite and other sulfide minerals are disseminated in the silicified country rock and are also clustered in the quartz veinlets. A well-developed mineralized stockwork zone is in the Promontorio area, especially proximal to the Cusi fault. These stockwork zones are the current targets for expansion and infill drilling, and their importance to the greater Cusi area is being studied in greater detail as a part of current exploration efforts.



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Mining Methods


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Crushers and Mills

Milling equipment has not been reported.



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Silver M oz 33
Lead kt 25
Zinc kt 15
Gold koz 14
All production numbers are expressed as payable metal.

Operational metrics

Daily ore mining rate  ....  Subscribe
Daily processing capacity  ....  Subscribe
Annual ore mining rate  ....  Subscribe
Waste tonnes, LOM  ....  Subscribe
Ore tonnes mined, LOM  ....  Subscribe
Total tonnes mined, LOM  ....  Subscribe
Tonnes processed, LOM  ....  Subscribe
* According to 2020 study.

Production Costs

Cash costs Silver Equivalent USD  ....  Subscribe
Assumed price Lead USD  ....  Subscribe
Assumed price Zinc USD  ....  Subscribe
Assumed price Silver USD  ....  Subscribe
Assumed price Gold USD  ....  Subscribe
* According to 2020 study / presentation.

Operating Costs

Total operating costs ($/t milled) USD 35.2 *  
* According to 2020 study.

Project Costs

MetricsUnitsLOM Total
Expansion CapEx $M USD  ......  Subscribe
Sustaining CapEx $M USD  ......  Subscribe
Working capital $M USD  ......  Subscribe
Closure costs $M USD  ......  Subscribe
Total CapEx $M USD  ......  Subscribe
UG OpEx $M USD  ......  Subscribe
Processing OpEx $M USD 132.1
G&A costs $M USD 14
Total OpEx $M USD  ......  Subscribe
Income Taxes $M USD  ......  Subscribe
Royalty payments $M USD  ......  Subscribe
Gross revenue (LOM) $M USD  ......  Subscribe
EBITDA (LOM) $M USD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax NPV @ 5% $M USD  ......  Subscribe
After-tax NPV @ 10% $M USD  ......  Subscribe
After-tax NPV @ 8% $M USD  ......  Subscribe
After-tax IRR, %  ......  Subscribe

Heavy Mobile Equipment


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Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Aug 31, 2020
....................... Subscription required ....................... Subscription required Subscription required Aug 31, 2020


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