Minera Tres Valles mining complex (MTV) is a Cu-Ag stratabound, manto-type deposit.

The MTV Project consists of two main deposit areas about 5km apart. The Don Gabriel area hosts the Don Gabriel Manto and Don Gabriel Vein deposits. The Papomono (“PPM”) area consists of seven known deposits: Massivo, Cumbre, Mantos Connection, PPM South, Mantos North, PPM North, and Epithermal.

Papomono
The dominant sulphides in the deposit are in decreasing order: chalcocite-covelite (~85%), bornite (~6%), enargite (~5%) and chalcopyrite (~4%). It is important to mention that the bulk of the chalcocite at MTV is hypogene. Very few parts were observed with supergene chalcocite. In places where intense fracturing and faulting occurs, the action of oxidizing agents generates oxide copper minerals: chrysocolla, malachite, brochantite and atacamite. For this reason, the traditional vertical zonation of oxides on top and sulphides in deeper parts are not identified in Papomono and the main oxide zones are related to more fractured zones, sometimes deeper than preserved sulphides.

The most common deposit geometry is the manto-type (stratiform). The individual “mantos” have a thickness that ranges from 2 to 50m, up to 500m strike extension and length along dip reaching 600m. Examples of this type of deposit geometry are the PPM South, Mantos Connection, and the Mantos North deposit. The other common geometry is vein-type, with a thickness between 2 and 15m, strike length from 100 to 420m and 100 to 250m deep. Dip angle is generally steep, between 80° and 90° to the west. There are also sets of tens of cm-thick N-S veins dipping 55° to the east. These sets of veins occur in clusters of 10 to 30 narrow, around 50m long, massive chalcocite veins.

One specific and important geometry is observed in only one deposit, PPM Massivo. It is a complex geometry which resulted from the intersection of at least three different mineralization controls in the same area: the Papomono Fault system, the favorable strata (mantos) and the N-S set of small veins dipping east. The resulting geometry is roughly an inverse triangle or a truncated rhomb shape, which has 440m strike, up to 190m wide and 190m high.

Finally, there is a cylinder-shape geometry related to the intrusive plug of Cumbre. This deposit is vertical, with at least 400m deep (310m from the bottom of exploited Cumbre pit) and an average diameter of 180m. A near surface oxide mineralized zone was hosted in the upper part of intrusive as well in the contact zones with volcanic to volcanoclastic rocks of the Quebrada Marquesa Formation and was already exploited by open pit. Deeper zones in Cumbre present disseminated chalcocite and bornite mineralization.

Don Gabriel
The mineral deposit of Don Gabriel is formed of two main zones:
- An upper deposit of “manto” type, medium copper grade, with a set of stratabound disseminated, fine chalcocite, mineralization approximately 100m thick, dipping 30° SSW.
- A lower deposit, vein-shaped (straight-tabular), sub-vertically oriented N45°W, with intense strong to spotty mineralization or veinlets type (stockwork or sheeted veinlets), high copper grade, with chalcocite, digenite and some bornite.

Whereas the first type is hosted mainly in andesite amygdaloidal levels, the second type has medium to coarse porphyritic andesite and/or dioritic to microdioritic dikes as host rock, which underlies the level of coarse sandstone. The layers of sandstone serve as a guide-level separating the two main units. It is used as a sharp limit between the two geological models, Don Gabriel Mantos and Don Gabriel Veins.

The vertical-tabular mineralization seems to be intimately linked to the presence of dioritic dikes, which, in turn, are related to an intrusive stock to the W and SW, and outcrops at the bottom of the ravine near the mineral deposit. Such stock was also intercepted by several drill holes a little further to the east. Those dikes found in such drill holes may also be observed in the mine’s roads cut, as a 2 to 10m-thick dike swarm, which follows the same N45-50°W direction of the mineralization.

Considering the clear relationship between the vein shape mineralization and such dikes, it is possible to speculate the presence of a metasomatic component in its genesis, despite no distinctive skarn mineral being observed, only epidote and chlorite. Another possibility is that the dioritic magma emplaced areas of structural weakness, also employed by the mineralizing fluids immediately after the igneous siting (tardi- magmatic event). In some areas, mineralization zones are also observed, with similar characteristics to the “mantos”, chalcocite disseminated mineralization with pervasive albite, which makes it possible to glimpse the potential presence of stratabound deposits, but not stratiforms, as a set of parallel veins restricted to favorable stratigraphic levels (e.g. mineral deposits El Soldado or El Espino). Another aspect worth mentioning is the common presence of veins or disseminated hematite surrounding the best mineral grade sectors.

Overview
The open pit mine plan for the Don Gabriel Manto was developed by IMC staff in March 2018, and the underground mine plan for the Papomono Masivo inclined block cave and front cave were developed by Wood staff in July 2018. The integrated plan for the open pit and underground operations (integrated case), supporting the mine plan, was prepared by Wood staff in August 2018.

Slope Angles
The slope angle design for the Don Gabriel pit is based on two reports by E-Mining. The first is “Informe Extendido – Estimación de Parámetros de Diseño y Análisis de Estabilidad Rajo Don Gabriel” dated May 2011, and the second is an addendum dated April 2012. The two reports specified the same geotechnical design. The interramp slope angle was specified by E-Mining as 52º. The height of continuous slope could not exceed 150 m without the inclusion of an additional 20 m catch berm. This would limit the overall angle to about 50º. The E-Mining analyses looked at possible largescale slope failures (low probability) and bench scale failures. The bench scale issues, maintenance of catch berms and retention of most failures on the catch berms, were the main considerations for the interramp slope angle recommendations.

Mining Phases
The Don Gabriel phase designs are based on analysis performed by Tetra Tech and summarized in the PowerPoint presentation “Optimización y Diseño – Rajo Don Gabriel Minera Tres Valles”, dated December 22, 2017. IMC also ran independent analyses to verify the final pit design.

The Tetra Tech analysis proposed dividing Don Gabriel into five mining phases. Figure 16-1 shows the relative locations of the phases. It is noted that the designs are conceptual in nature; in particular access roads were not included. IMC updated the designs to make the phases operational. It is assumed that most of the Don Gabriel ore and waste will exit the pit on contour since the pit is cut into a hill, so internal roads are expected to be fewer than in more typical open pits.

The final mining phases are a combination of MTV, Tetra Tech, and IMC designs. There will be six pit phases, numbered 2 through 7.
• Phases 2 and 3 are MTV designs for short-term planning in the north part of the Don Gabriel deposit. These phases replace the Tetra Tech phase 1 pit. The MTV phase 1 pit has been completed • Phases 4, 5, 6, and 7 are the IMC/Tetra Tech phases 2, 3, 4, and 5.

The mining phases amount to 5.17 Mt at 0.81% TCu and 0.71% recoverable copper (RecCu) for 92.7 million contained copper pounds and 81.1 million recoverable copper pounds. The metallurgical recovery averages about 87.4%. Total material in the pit is 27.2 Mt for a waste:ore ratio of 4.3 to 1. The indicated recovery and payable copper are slightly higher than the Mineral Reserve in Table 15-1. The Mineral Reserve is based on acid leaching for 2018, thus the difference. The biggest operational challenge will be the IMC’s pit phase 6. At about the 1560 bench, the phase 6 wall will catch up to the phase 5 wall. All the material between the 1560 bench and the 1470 flat will have to exit the pit to the north. This means waste will exit to the north and go around the pit to get to the south waste storage area. The second issue is the bottom several benches of the phase are in the narrow wedge between phase 3 and phase 4.

Waste Rock Storage Facilities
A waste rock storage facility (WRSF) was designed for the Don Gabriel open pit. Based on the mine production schedule, the total waste rock volume is anticipated to be about 22 Mt.

Papomono Masivo
Caving and stoping mining methods were analyzed, assessing low mining cost and high dilution ratio scenarios versus higher mining cost and lower dilution ratio scenarios. Studies completed by INGEROC in 2013 had recommended the combined use of sub-level caving and inclined block caving methods for the recovery of Papomono Masivo sector.

Caveability and Fragmentation of Inclined Block Cave
The fundamental viability for the use of the inclined block caving mining method is that the rock mass will fail and cave for a given area opened (critical hydraulic radius at caving) with subsequent growth of the cave upwards (advance vertically with the draw of material) such that the cave is self-sustaining until it reaches the surface or breaks all of the in-situ orebody column.

There are two conditions in caving mechanics (Brown, 2004): in a stress cave, the cave advance is vertically upward and in a subsidence cave, the cave advance is sideways. At the start of a new sector the caving advance is general vertically upwards.

A caveability assessment was undertaken using Laubscher’s empirical stability chart version 2001 (Brown, 2004), based on worldwide experience on caving and stable situations in terms of the hydraulic radius (area divided by perimeter) for a range of MRMR values.

To estimate the required minimum hydraulic radius (HR = area/perimeter) of the footprint required to initiate caving (self-sustaining to surface), a RMRL value of 27 will be used for the start of caving. Assuming that the initial caving front will be polygonal, an A-type curve will be used.

Mining Layout of Inclined Block Cave
A work plan was derived, based on the following concepts:
• Investment limit: Project initial infrastructure (civil and mining) whose costs should not exceed US$10 million as the initial capital cost, excluding mobile equipment
• Attain a production capacity of 2,000 t/d.

Design of the first phase must allow for flexibility of construction of the second phase. The base of the Papomono Masivo inclined block caving layout was a 10 x 10 x 10 m operational grid with 130 draw points and five levels. The two-phase plan consists of:
• Prepare a sufficient and minimum base area to ensure caving with HR = 9 m, i.e. an area of 3,000 m2 plus a supplemental area to ensure continuity of development. The initial caved area corresponds to a zone 60 m long by 50 m wide, which results in a HR of 13, exceeding the minimum HR of 9 m which will assure the starting and propagation of caving. Besides this initial area, the adjacent drifts will also be developed so as to ensure uninterrupted operations while the second phase is being developed
• The initial area is bigger than what is strictly needed for caving in order to achieve the initiation and propagation of the caving with a limited extraction, and to allow for the gradual fracturing and collapse of the cave back without producing cavities in the cave vault, to prevent potential air blasts
• Develop the second phase after verifying the initial caving, until the total area to be mined using 130 draw points is reached.

Ventilation
The ventilation strategy for the inclined block cave maintains existing fresh air intakes from the North and South portals.

Vitiated air will be exhausted through a new adit that will be located at the “Narbona” tunnel. The main existing ventilation raise will be used as an exhaust system to serve the mine main access and the haul truck circuit.

The total air requirement for the project is estimated at 103 m3 /s. The air will be taken from the main access to be distributed to the different levels in the southern area by the local air intake system consisting of galleries, raises, secondary and ancillary fans.

Material Handling
The material handling system assumes extraction using mining by means of 3.5 yd3 load-haul-dump (LHD) equipment, conveying ore from the mining points to ore passes that will be located in the main haulage tunnel. These ore passes will include a grizzly, regulating ore size to 80 cm maximum and the eventual use of an existing mobile hammer for secondary reduction.

Minera Tres Valles’ process starts by receiving ore from both of the company’s own mines as well as third parties at the main Ore Stockyard. The different batches are loaded into a primary jaw crusher that reduces the rock to fragments smaller than < 90 mm. From this stage, the ore is sent to a standard cone type secondary crusher, which produces fragments no bigger than < 25 mm (1”).

This material is sent to the tertiary crusher, where the grain size is < 14 mm. Finally, the ore is sent to the quaternary crusher, which reduces the size of the stacking ore to < 6 mm (or ¼”).

In the fourth quarter of 2019, the configuration of the crusher was modified to a three-stage configuration where either the tertiary or quaternary crusher is utilized in the circuit depending on the type of ore being put through the SX-EW plant in order to optimize grind size. This application is expected to continue going forward producing efficiencies to the operation.

MTV currently produces high-grade copper cathodes using a heap-leach and SX/EW process.

The crushed material is agglomerated, and water and acid are added to commence the leaching process. The agglomerated material is trucked to the heap leach area and stacked by front-end loaders. A grid of hoses with drippers is placed over the heaped material and the first phase of intensive leaching to recover the oxide mineralization during the first three-month period commences using constant and high acidconcentration irrigation. The product of this first leaching stage is the “oxide-pregnant each solution” (oxide-PLS), which has a high copper content and is accumulated in a pond at the bottom of the leach pads. For the subsequent six months, the material is irrigated on an intermittent basis, with lower acid concentration to extract the copper from sulphides (chalcocite, covellite and some bornite). The resulting PLS (sulphidePLS) is stored in another pond.

The oxi ........