The Gramalote Ridge and Trinidad deposits are considered to be examples of structurally-controlled intrusive-related gold deposits.

Intrusive-related gold deposits have many synonyms, including Intrusion-related gold systems, gold porphyries, and plutonic-related gold quartz veins. The deposit model that follows is abstracted from Lefebure and Hart (2005).

The deposit shows a number of the features of intrusive-related gold deposits, including:

• Alteration and mineralization are structurally controlled, restricted to small haloes along veins, sheeted veins and stockworks arrays;
• Sulphides content is less than 5%;
• Some evidence indicates that the host rock is directly related to fluids evolved from the cooling pluton, including pegmatite, aplite and K-feldspar alteration (Rodríguez, 2009).

The QP is of the opinion that exploration programs that use a structurally-controlled, intrusive-related gold model are applicable to the Project area.

The Project is located in the northern portion of Colombia’s Central Cordillera. The terrane primarily comprises a metamorphic basement complex and the Antioquia Batholith. The Cajamarca–Valdivia basement terrane (Cediel and Ciceres, 2000 and Cediel et al, 2003) consists of early Paleozoic metamorphic rocks; as well as ophiolitic, oceanic, volcanic, and intrusive rocks.

In the general Project area, the main compositional types within the Antioquia Batholith are t ........

The 2020 PEA is based on mining of the Gramalote Ridge deposit only. No mining is envisaged for the Trinidad deposit in the 2020 PEA.

A conventional open pit truck and shovel operation is planned. A SMU size of 10 m x 10 m x 10 m was used was used for benchmarking the mineral resource model. No additional dilution factor or mining loss was applied to the grades in the mine plan.

The Gramalote Ridge pit will have four phases, consisting of three phases in the main pit, and a small satellite pit that will have a single phase.

The main ramps were designed to 30 m width for two-way access, and are assumed to have a 10% gradient. The lowest benches will have a 15 m wide ramp, and will be single-lane. Pit benches are assumed at 10 m intervals, with pre-split drilling at 20 m depths, drilling two benches at a time.

The mine planning strategy includes the use of stockpiles for oxide and sulphide materials. Three stockpiles are planned:

• High-grade sulphide stockpile; approximate 6.5 Mt capacity; =0.66 g/t Au material for the initial years, variable thereafter to optimize head grade;

• Low-grade stockpiles; approximate 46.3 Mt capacity; =0.29–=0.66 g/t Au material;

• Oxide stockpiles; approximate 4.5 Mt capacity; =0.25 g/t Au material.

All stockpile areas will have access ramps that are 30 m wide and a maximum 8% grade as well as a temporary slope angle of 30º.

A waste rock storage faci ........

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The proposed plant will process ROM mill feed material at a rate of 11 Mt/a to produce doré bars, using conventional equipment and processes. The process plant will consist of primary crushing, two-stage grinding with flash flotation, conventional froth flotation, flotation tailings pumping, concentrate regrinding, concentrate leach, CCD thickening, carbon-in-pulp (CIP), carbon desorption, gold recovery by zinc precipitation (Merrill Crowe), and cyanide destruction of CIP tailings slurry before the tailings are pumped to the tailings management facility (TMF).

The flotation circuit configuration will consist of a forced air rougher/cleaner configuration with the cleaner tailings being returned to the head of the rougher bank. The cyclone overflow slurry will flow by gravity into the flotation feed distribution box, where the incoming slurry will be distributed into two parallel streams each feeding a rougher flotation bank. Slurry will flow into an agitated conditioning tan ........