Peru

Ayawilca Project

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Categories

Overview

Mine TypeUnderground
StagePreliminary Economic Assessment
Commodities
  • Zinc
  • Tin
  • Lead
  • Silver
Mining Method
  • Cut & Fill
  • Sub-level stoping
  • Cemented paste backfill
  • Unconsolidated rockfill
Mine Life14.4 years (as of Jan 1, 2021)
ShapshotA Preliminary Economic Assessment dated 14 October 2021 indicates that Ayawilca has the potential to be a Top-10 global zinc producer.

Owners

SourceSource
CompanyInterestOwnership
Tinka Resources Ltd. 100 % Indirect
The Project is held 100% by Tinka, through its wholly-owned subsidiary, Tinka Resources S.A.C.

Contractors

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Deposit type

  • Manto
  • Carbonate replacement

Summary:

The regional setting, geometry, and zinc mineralogy indicates that the Zinc and Tin Zones of the Ayawilca deposit are CRDs, of which there are several other type examplesin central Peru (e.g., Cerro de Pasco, Morococha, Colquijirca, and San Gregorio). These deposits typically develop when hydrothermal fluids replace carbonate rocks proximal to an intrusive body, although in some cases the causative intrusive body is not observed. CRDs are considered more distal from the source than porphyry and skarn deposits, but closer to the source than intermediate- (or low-) sulphidation epithermal precious metals deposits.

The Ayawilca deposit differs from most other CRDs in central Peru in that there is an early tin–copper mineralization event associated with pyrrhotite. The QPs note that early pyrrhotite tin–copper mineralization is reported at the Cerro de Pasco deposit, although apparently it is not so well developed as at Ayawilca.

The oldest rocks mapped on the Property are phyllite metamorphic rocks which belong to the Devonian Excelsior Group. These outcrop in the north–central and eastern portions of the Project area, and consist of light coloured quartz–sericite–chlorite phyllite and minor graphitic schist. Foliations strike generally northwest–southeast with gentle to moderate dips to the southwest and northeast. The large phyllite outcrop is interpreted to be the core of an anticline (basement high) bounded by two sub-parallel northwest-trending Andean faults approximately 2 km apart, and crosscut by several northeast-trending trans-tensional faults.

The Project hosts several styles of mineralization within numerous deposits, zones, and target areas. Mineral Resources have been estimated at the Ayawilca deposit within the Zinc and Tin Zones, and the Colquipucro deposit. Other target areas on the Property that warrant additional exploration work and include Chaucha, Zone 3, Valley, Far South, Yanapizgo, Pucarumi, and Tambillo.

Ayawilca Zinc–Lead–Silver Mineralization
Zinc mineralization within the Ayawilca deposit is predominantly hosted within a sequence of limestone breccia, limestone, dolomite, calcareous siltstone, arenite, and greywacke, of the Pucará Group. The Zinc Zone is made up of multiple, gently-dipping, sulphide lenses or “mantos”, generally with vertical thicknesses of between 10–30 m (locally thicker) within four areas (West, South, Central, and East). At the West and South areas the mantos are stacked on top of each other to form almost continuous zone with vertical thicknesses up to 150 m, comprising several flat-dipping mantos each up to 70 m thick.

The four structural zones span 2.1 km in the northeast–southwest direction and 1.3 km in the north– south direction. Each zone has been modelled separately. The West area measures approximately 640 m in length in the north–south direction and 300–450 m in the east-west direction, while the South area measures approximately 550 m in length in the northeast–southwest direction and 250 m in the northwest–southeast direction.

Zinc mineralization occurs as massive to semi-massive sulphide replacements of the carbonate rocks and is thought to be controlled by multiple, sub-parallel, east–west-, and northeast–southwest- trending structures, as well as low angle thrust faults. The mineralized zones are interpreted to be generally gently dipping, replacing favourable sedimentary units. Zinc occurs as various generations of sulphide impregnations (mostly marmatite, a high-iron variety of sphalerite also known as “black jack”) and sphalerite (with purple to red–brown tones) accompanied by abundant pyrite, pyrrhotite, chlorite, iron carbonate (siderite), and magnetite. Less common sulphides include galena, chalcopyrite, arsenopyrite, and silver sulphosalts. Multi-element geochemistry indicates that indium is correlated with the zinc mineralization.

Narrow, high grade marmatite-sphalerite veins and mantos cut through the Goyllar sandstone, and occasionally have broken through to the surface (e.g., in the West and South areas). Veins are typically 0.2–1.0 m in width. At Pucarumi,zinc oxide mineralization is hosted by favourable bedforms in Chulec Formation limestone.

Late carbonate–sphalerite–galena–proustite veins within the South and West areas are interpreted to be steeply-dipping, exhibit epithermal textures, and are interpreted to be the last mineralization event. This style of vein mineralization has not been modelled as part of the Mineral Resource; however, these veins can have very high silver grades and offer further potential for later exploration.

At the South area, pervasive carbonate alteration of limestone accompanied by galena and silver sulphide minerals, including polybasite and freibergite, was intercepted in the southwestern-most drill holes peripheral to the Zinc Zone at the Silver area, and remains open in all directions.

Zinc mineralization is generally associated with argillic alteration within the carbonate host rocks. Disseminated clots of white clays (dickite) are common within and near the mineralization. Dickite and illite are widespread and were identified using short-wave infrared spectrometry. Higher temperature clays, such as pyrophyllite, are observed in the Central area, suggesting a possible thermal aureole centred on this zone.

Ayawilca Tin–Copper Mineralization
The tin mineralization (Tin Zone), which occurs with minor copper as chalcopyrite, is hosted in massive to semi-massive pyrrhotite mantos typically 5–10 m in vertical thickness(up to 50 m) typically at, or near, the contact of the Pucará Group carbonate rocks and the Excelsior Formation phyllite, although tin bearing mantos also occur higher in the limestone sequence especially at the South area. Quartz–tin–copper stockwork mineralization also occurs within the phyllite in some areas beneath the pyrrhotite mantos.

Reserves

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Mining Methods

  • Cut & Fill
  • Sub-level stoping
  • Cemented paste backfill
  • Unconsolidated rockfill

Summary:

The Ayawilca deposit is planned to be mined using underground mining methods. To define the mining method, the University of British Columbia (UBC) mining method selection system was applied, together with consideration of aspects such as safety, the geometry of the resources, the distribution of grades, the scale of production and mining costs. Based on this analyses, two suitable mining methods were selected:
- Overhand cut-and-fill (OCF) with pillars;
- Sub-level stoping (SLS).

The mining strategy involves dividing the deposit into five zones by spatial location and by mining method:
- OCF with pillars: Central and East areas;
- SLS: West, South areas and Silver Zones.
The netsmelter return cut-off was defined at US$65/t, asit covers mining, processing, general and administrative costs and sustaining capital costs, and was determined to be a reasonable balance considering the margin per tonne of material mined while still having a reasonable resource extraction and mine life.

The production rate was set at 8,500 t/d after considering the sustainable rate achievable from the multiple mining areas. Optimizations were completed using the mineable shape optimiser (MSO) unit within Datamine software. The SMU length and height were fixed values, whereas the width varied by zone and mineralized structure, from 5–45 m. Sections of 5 x 5 m were defined for the development drives and the Central area pillars.

A mining recovery of 95% was assumed for the SLS method and a 100% mining recovery was used for the OCF with pillars method. In the areas to be mined by OCF with pillars, it was assumed that pillars will be recovered in the last years of the mine plan. A recovery of 70% was assumed for these pillars, because the rock conditions may not be entirely favorable due to the initial mining within the zone.

A variable mining dilution assumption (% dilution) was applied, depending on the mining method, and consisted of internal dilution based on the defined stope sizes. No external unplanned dilution was included in the 2021 PEA since the stopes are generally continuous in nature. Future studies may result in the stope shapes being refined to potentially consider less internal dilution.

Backfill will be required to support the proposed mining methods. A combination of rock fill and paste backfill is proposed:
- SLS stopes: will require paste fill; the mining method assumes continuous mining in a retreat fashion;
- OCF: will require rock and paste fill; the mining method assumes primary stopes filled with paste, and secondary stopes are filled with rock fill.

The stope fill volume required was provisionally estimated at 15.8 Mm3. Consideration of inputs such as the rock geomechanical properties and the mine design and stoping sequence indicated that there was a stope volume of about 3.34 Mm3 that did not require any fill materials. The LOM design assumed that 12.46 Mm3 of backfill material would be required, consisting of:
- Rock fill: 3.3 Mm3;
- Paste fill: 9.2 Mm3.

The mine is planned to access the mineralization through a system of three main ramps, which will access the five proposed main mining zones.

The ramp system will have variable gradients, including:
- Maximum gradients of ±13%;
- Gradients on curves of ± 8–10%;
- Gradients on the sublevels, accesses and chambers of ±0.5–1%.

The mine plan assumes the following:
- A 2,815 m ramp will be developed from level 4,170 to access the South area. This area will be later accessed by the second ramp that will be developed for the Silver area from level 3,880. This ramp will be 713 m long;
- The West area will have an independent ramp access of 3,430 m length. The portal will be located at an elevation of 4,280 masl;
- During Year 7, a 2,995 m ramp will be constructed from elevation 4,095 masl to access the Central area. A 199 m cross-cut will be developed on level 3,845, and will connect to the East area. The East area will have a 1,964 m long ramp to support mining activities;
- A 377 m long connection ramp will join the Central and West areas to provide haulage flexibility and alleviate congestion. This will allow either the Central or the West area ramps to be used.

Comminution

Crushers and Mills

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Processing

  • Jameson Cell Flotation
  • Dewatering
  • Filter press

Summary:

Processing of the zinc mineralization will be through a conventional primary crushing, semi-autogenous grinding (SAG), secondary ball mill grinding, lead and silver flotation, zinc flotation, concentrate thickening and filtration. The concentrator plant will produce two concentrates: a zinc concentrate and a lead–silver concentrate. A portion of the tailings will be mixed with cement and used as structural mine backfill material in the underground operations, while the remainder will be thickened and filtered, then disposed of on a filtered tailings storage facility (TSF). Process water will be recycled as much as possible to minimize water usage.

An 8,500 t/d throughput rate was selected as the basis for the 2021 PEA. A lean, fit-for-purpose plant design standard was used, to cover the required duty for the projected 14 year mine life. The design will accommodate nominal operation with a small degree of capacity flexibility for upsets and variability, but has no consideration or allowance for any expansion.

The processing plant will consist of the following unit operations:
- Primary jaw crushing;
- Crushed ROM handling;
- SAG milling;
- Ball mill secondary grinding in a closed circuit with hydrocyclone classification;
- Lead circuit, including rougher flotation, cleaner flotation;
- Zinc circuit, including rougher flotation, regrind, cleaner flotation;
- Concentrate dewatering (zinc and lead–silver concentrates);
- Flotation tailings thickening, filtration and stacking onto a filtered TSF;
- Tailings backfill plant;
- Fresh and reclaim water supply;
- Reagent preparation and distribution.

The ball mill discharge will feed the lead–silver flotation Jameson flotation cells. This circuit will comprise of rougher and cleaner flotation stages.

The zinc flotation circuit will consist of rougher, regrind, cleaner and cleaner–scavenger stages. Jameson pneumatic flotation cells will be used in the zinc flotation circuit to produce a zinc concentrate. Jameson-type cells were selected because of the capacity for fine air bubble generation, intense mixing, high bubble loading, and efficient froth washing which promote higher grade concentrates when compared to conventional mechanical cells.

The zinc concentrate high-rate thickener underflow will be pumped to a press filter to produce a final concentrate cake. Concentrate cake will be trucked to a local refinery forsale.

The lead flotation concentrate will be pumped to a concentrate tank, and then pumped to a vacuum disc filter. Final concentrate cake will be transported by truck to a port for sale.

A conventional high rate thickener is proposed for tailings thickening. Tailings will be dewatered and the underflow will report to a filter press where it will be further dewatered to produce a filter cake.

Part of the filtered tailings will be stored on the surface in compacted piles in a dedicated filtered TSF. The remainder will report to a mine backfill plant where it will be mixed with cement and transported underground to be deposited mine voids for permanent storage. The thickener overflow water will be returned to the processing plant as process water.

Recoveries & Grades:

CommodityParameterAvg. LOM
Zinc Recovery Rate, % 92
Zinc Head Grade, % 5.56
Zinc Concentrate Grade, % 50
Lead Recovery Rate, % 85
Lead Head Grade, % 0.2
Lead Concentrate Grade, % 50
Silver Recovery Rate, % 45
Silver Head Grade, g/t 14.5
Silver Concentrate Grade, g/t 2,272

Production

CommodityProductUnitsAvg. AnnualLOM
Zinc Concentrate kt 3094,450
Zinc Payable metal M lbs 4,112
Zinc Metal in concentrate M lbs 4,905
Lead Payable metal k lbs 129,125
Lead Metal in concentrate k lbs 137,642
Silver Payable metal koz 8,649
Silver Metal in lead concentrate koz 6329,122
Zinc Equivalent Payable metal k lbs 4,372,606
Lead-Silver Concentrate kt 8.7125

Operational metrics

Metrics
Daily ore mining rate 8,500 t *
Daily processing capacity 8,500 t *
Ore tonnes mined, LOM 43,526 kt *
Tonnes processed, LOM 43,526 kt *
* According to 2021 study.

Production Costs

CommodityUnitsAverage
Credits (by-product) Zinc USD 000
Cash costs (sold) Zinc USD 000
Cash costs (sold) Zinc USD 0000000
All-in sustaining costs (sold) Zinc USD 0000000
Assumed price Lead USD 000
Assumed price Zinc USD 00
Assumed price Silver USD 00
* According to 2021 study / presentation.
Net of By-Product.

Operating Costs

Currency2021
UG mining costs ($/t milled) USD 32.8 *  
Processing costs ($/t milled) USD 7.1 *  
G&A ($/t milled) USD 4.27 *  
Total operating costs ($/t milled) USD 44.2 *  
* According to 2021 study.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M USD 263.9
Sustaining CapEx $M USD 186.9
Closure costs $M USD 15.2
Total CapEx $M USD 450.8
UG OpEx $M USD 1,427
Processing OpEx $M USD 309
G&A costs $M USD 186
Total OpEx $M USD 1,922
Mining Taxes $M USD 54.8
Income Taxes $M USD 446.2
Total Taxes $M USD 585.9
Royalty payments $M USD 114
Net revenue (LOM) $M USD 4,156
Net Operating Income (LOM) $M USD 2,120
Pre-tax Cash Flow (LOM) $M USD 1,654
After-tax Cash Flow (LOM) $M USD 1,068
Pre-tax NPV @ 8% $M USD 720
After-tax NPV @ 5% $M USD 604
After-tax NPV @ 10% $M USD 347
After-tax NPV @ 8% $M USD 433
Pre-tax IRR, % 42.6
After-tax IRR, % 31.9
Pre-tax payback period, years 2
After-tax payback period, years 2.6

Heavy Mobile Equipment

Ref. Date: October 14, 2021

SourceSource
HME TypeModelQuantity
ANFO Loader 25
Bolter 4
Drill Atlas Copco Simba 11
Grader 8
Jumbo 4
Rockbreaker 4
Scaler 8
Scoop Tram 15
Truck (fuel / lube) 8
Truck (haul) 85
Truck (water) 4

Personnel

Mine Management

Source Source
Job TitleNameProfileRef. Date
Consultant - Mining & Costs Edgard Vilela LinkedIn Oct 14, 2021
Consultant - Recovery Methods & Costs Adam Johnston LinkedIn Oct 14, 2021
President and CEO Graham Carman LinkedIn Feb 6, 2024

Aerial view:

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