Deposit Type
The San Agustin Project does not fit entirely into an epithermal classification. The San Agustin deposit appears genetically and spatially related to a quartz monzonite stock with intense phyllic alteration and local tourmaline breccias. These factors may point towards a telescoped system associated with a deeper porphyry centre. This is supported by broad zones of potassic alteration that are overlapped by pervasive phyllic alteration; however, locally on the surface and in some drill holes, boiling textures, suggestive of an epithermal system do occur. Mineralization is mainly associated with pyrite that fills fractures, is disseminated, and occurs in the matrix of hydrothermal breccias. These form an extensive system of sulphide stockworks and disseminated mineralization dominated by pyrite.

San Agustin is interpreted to be a porphyry-style gold system related to Eocene aged intrusions emplaced into Cretaceous clastic and carbonate sedimentary rocks in an extensional tectonic setting. Gold mineralization occurs throughout the magmatic-hydrothermal system in space and time and is spatially related to early potassic development and an overprint of phyllic alteration. Supergene alteration, formed as a product of acid leaching, resulted in argillic-quartz alteration assemblages within the oxide zone of the deposit. The main gold event is associated with magmatic hydrothermal fluids corresponding to phyllic alteration. The gold system was overprinte ........

San Agustin is a contract-operated mine and Owner-operated process facility using conventional equipment and conventional mining methods.

The San Agustin mine is a relatively low-grade gold deposit that benefits from a low strip ratio and disseminated mineralization that is amenable to bulk mining activities and good heap leach recoveries. Situated in a semi-arid environment surrounded by moderate topography, the oxide material that hosts the mineralization is relatively shallow with no major impediments to mining.

There are seven mine phases remaining in the LOM plan and the final pit dimensions are approximately 1.6 km long (east-west) by 1.1 km wide (north-south) and up to 140 m deep. The final pit contains approximately 36.6 Mt of ore and 28.7 Mt of waste for an overall strip ratio of 0.78 (waste:ore) including mining dilution and ore losses applied in the mine schedule. Production is expected to be limited to 11 Mt/year for ore over the course of the mine life. As a result, it is expected that 344 koz of gold will be placed on the heap leach pad from August 2021 through the end of 2024 for a remaining mine life of 3.5 years.

The mining method consists of traditional drill-and-blast operations followed by excavator loading of rigid-body haul trucks (100 t class) for ore transport to the crusher and waste transportation to designated WRSF locations.

Approximately 16.7 Mm3 of waste storage space was defined outside the current and ........

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The San Agustin Project is an open pit mine with a heap leach operation using a multiple-lift, single-use leach pad. There are two crushing plants at San Agustin: a 17,000 t/d plant and a 13,000 t/d plant. The ore is crushed (P80 22 mm) at a total rate of approximately 30,000 t/d, stockpiled, reclaimed, agglomerated, and stacked on the leach pad with a mobile conveyor stacking system. The stacked ore is leached with a low-grade cyanide solution and the resulting pregnant solution is processed through a 1,200 m3/hr gravity-cascade carbon adsorption circuit to extract gold and silver. A small 250 m3/hr Merril Crowe plant was added in 2020 to treat pregnant solutions for some gold extraction and additional silver recovery from the overall circuit. The loaded carbon is trucked to Argonaut’s La Colorada mine for carbon stripping and smelting. Precipitate from the Merrill-Crowe plant is also shipped to La Colorada for smelting.

Heap Leaching
The existing heap leach pad is a m ........