The main deposit type in the Aurizona project area is greenstone-hosted orogenic gold, a subtype of the larger orogenic class of gold deposits.

The primary mineralization style on the Property consists of orogenic-style gold deposits, typically associated with the quartz diorite and feldspar quartz diorite units in brittle-ductile structures like the ASZ. Significant gold occurrences in the project area include the Piaba, Boa Esperança, Tatajuba and Genipapo deposits, as well as the Mestre Chico and Micote targets.

Piaba is a structurally-controlled, tabular, orogenic gold deposit with a strike length of ~3.3 km, width of 10 – 50 m, and down-dip extent of at least 700 m, beyond which the deposit is sparsely explored. The deposit is hosted in the brittle-ductile ASZ that is ENE-WSW striking and steeply north dipping to the NNW.

Within the Piaba deposit, the ASZ system is divided into ten shear zones and/or brittle faults, partially segmenting the deposit with limited offsets. The maximum offset observed is 100 m, whereas most offsets are in the order of 10 m. The Pirocaua fault zone at the east-northeast end of the deposit is a significant structure. This brittle fault zone is up to 350 m wide and locally disrupts the Piaba gold zone with a maximum offset of 75 m. At the western end of Piaba on section 1900W there is a northwest striking fault, which truncates the gold zone at depth. Near surface mineralization continues west of the fault in Piaba west area although the possible offset of the mineralization at depth has not been tested.

Mineralization is primarily hosted in the quartz diorite that is also described as a dike-like c. 2.0 Ga granophyric granodiorite (e.g. Freitas and Klein, 2013; Klein et al., 2015) but has also been interpreted as a cataclasite unit. Ore-related alteration includes strong to intense sericite carbonate-silica-sulphide alteration in the central part of the structure (i.e. in the quartz diorite) flanked by chlorite-dominant alteration in the footwall and hangingwall. Gold occurs in thin, millimetre to centimetre-scale, and quartz -carbonate ± sulphide± tourmaline bearing shear veins. Native gold is rarely observed at wall rock-vein contacts. Sub-horizontal quartz-carbonate extensional veins commonly cut shear veins and can contain gold. Increased vein density and sulphide abundance are the best indicators of gold mineralization.

The Boa Esperança deposit is located approximately one kilometre south of the Piaba deposit and consists of four sub-parallel gold-bearing zones that are continuous along strike for ~1000 m. The four gold-bearing zones are each about 5 ± 2 m wide and developed in a corridor ranging from 40 – 75 m in width, narrowing to 20 m at the northeastern end where there are generally just two zones. The four gold bearing zones coalesce within the saprolite and laterite portions of the eastern margin of the deposit. The deposit extends to at least 230 m below the surface and is hosted within a brittle-ductile structure trending ENE-WSW and dipping steeply (80°–90°) to the NNW.

Mineralization is hosted in strongly altered and deformed Aurizona Group rocks, likely derived from the adjacent Aurizona Group diorite, gabbro, and minor metasedimentary rocks. The mineralized corridor shows moderate to strong silica-sericite-albite-carbonate alteration, along with increased disseminated pyrite (2 – 5 modal percent) and density of quartz-carbonate-sulphide veins.

The Tatajuba deposit is also hosted within the ASZ, with the eastern end of the deposit located ~2 km west of the western end of the Piaba deposit. The Tatajuba deposit comprises a tabular zone that is east-west striking and steeply north-dipping; the zone measures ~700 m long, 5 – 30 m thick and 300 m in downdip extent. Within the eastern portion of the Tatajuba deposit, the ASZ system is interpreted to be cross-cut by subvertical NNW-trending structures. The maximum offset observed is between sections 200E and 300E, where the deposit is offset by 10 m, through sinistral shearing and/or faulting.

Gold mineralization is hosted in a subvertical to north dipping quartz diorite unit with concordant shear veins and moderately south dipping extensional veins. The quartz diorite shows granular cataclastic texture and is silica-carbonate-sericite-altered, grading outward into strongly chlorite-carbonate altered rocks. Shear and extension veins are mostly restricted to the tabular quartz diorite unit, with shear veins sub-concordant to this unit and consisting of quartz ± carbonate ± chlorite ± pyrite ± arsenopyrite. Extension veins appear to be moderately south dipping to sub-horizontal and consist of quartz with ~1–10% pyrite. Visible gold occurs in both vein types but is most abundant within the extension veins. Gold values are correlated with arsenic and associated with arsenopyrite.

The Genipapo North and South deposits are located about one kilometre east of the eastern margin of the Piaba deposit, with Genipapo North approximately 400 m north of Genipapo South. These deposits form in splays off the ASZ. The geology, geochemistry and magnetic data indicate a horsetail structure off the ASZ structure. Numerous fault structures and discontinuous splays of metavolcanoclastic and ultramafic units have been interpreted at Genipapo and the surrounding area. The metavolcaniclastic sequences are comprised of metatuffs, metagraywackes, phyllites and are in fault contact with ultramafic rocks. Gold mineralization is associated with shear-hosted smoky quartz veins and millimetre-scale extensional veins that form a stockwork. The mineralization forms in quartz ± albite ± sericite alteration with pyrite and arsenopyrite minerals. There is a strong correlation between gold and arsenic.

Touro is located about 20 km southwest of the Piaba deposit. The Touro deposit is hosted in a coarse-grained DRT and strongly deformed MVC rocks from Aurizona Group. A regional northeast- southwest treading mylonitic shear zone the host rocks which are cut by late andesite and aplite to pegmatite dykes.

The Aurizona Mine is currently an operating open pit mine with ore processing by gravity concentration and cyanide leach (CIL) circuit which restarted operations in 2018 after three years on care and maintenance. This PFS considers the addition of an underground mine beneath the existing Piaba pit that will assist in extending the mine life to 2032. The additional open pit areas of Tatajuba and Genipapo have been incorporated in the mine plan.

Boa Esperança
Criteria used for the Piaba and Piaba East pits in laterite and saprolite are considered to be relevant and are applied in the Boa Esperança pit design. The Boa Esperança pit is only 52 m deep at its maximum depth which is less than the depth of Piaba and Piaba East, both which have shown stability with the design parameters.

Tatajuba, Genipapo North and South
Geotechnical guidance for the outlying areas of Tatajuba, Genipapo North and South have relied upon the earlier work for Piaba as guidance for the PFS. The majority of Tatajuba is in lateritic and saprolitic material (61%) which is expected to behave in a manner similar to the Piaba pits. The thickness of the laterite and saprolite material totals a maximum of 46 m. The transition and fresh rock account only for 22% and 17% respectively and are predominantly at the east and west extents of the pit with a maximum combined thickness of 65 m. The geotechnical design parameters used at Tatajuba are the same as at Piaba.

Underground
The underground mine provides feed to the mill starting in 2023 but is at full capacity in 2026 onwards. Peak underground production is 1.36 Mt in 2027.

The underground mine is developed using conventional longhole mining methods. In locations where the stope thickness is less than 8.0 m wide mining was done by Longhole Open Stoping with Permanent Rib Pillars (LHwPRP). For stopes wider than 8.0 m the mining method was Longhole Open Stoping with Cemented Rockfill (LHwC).

Stope Design
A level spacing of 23 vertical m was chosen for all stoping areas. Subdivision of the underground mine into separate mining areas provides the opportunity to optimise level spacing and location for each of the separate mining areas should that prove advantageous in future studies. A stope development drift height of 4.5 m was selected to suit medium-sized mobile production equipment. Thus, all production stopes were designed to be 18.5 vertical m in height (23 m less 4.5 m). A minimum stope design width of 1.8 m true width was applied. Longhole stope outlines were designed on 5 m-spaced sections using the 2.0 g/t Au grade shell and vein wireframe as a guide. There are several areas where two or more (up to four) potentially sub parallel economic veins are located in close proximity to each other on the same level. Based on geotechnical advice a minimum 5 m interval was applied between adjacent stopes. Where the vein interval was less than 5 m, multiple veins were included in the stope outlines if the resulting grade exceeded cut-off grade. Overall, the underground mine has a total strike length in the order of 2.3 km in length. The deposit was divided into the following seven mining zones, each with an average strike length of the mining areas varied from 200 m to about 500 m in length:
• Zone 1-2;
• Zone 3 – Single stope available for test mining;
• Zone 4;
• Zone 5 Upper- commencing above a 10 m high sill pilar;
• Zone 6 Upper- commencing above a 10 m high sill pilar;
• Zone 5-6 Lower – commencing at the base of the deposit and including one level of uphole stoping to define the base of the 10 m high sill pill;
• Zone 7.

Recovery of Pillars
The rib pillars incorporated in the LHwPRP mining method are unrecoverable. In order to quickly advance production of higher grade ore in Zones 5 and 6 a 10 m sill pillar is planned to separate Zone 5 Upper and Zone 6 Upper from Zone 5/6 Lower below. The half-height stopes below the sill pillar in Zone 5/6 Lower are recovered by the drilling of up-holes and will not be backfilled. Rib pillars will be left behind, similar to the other stopes. In order to manage the performance of the inter-lode pillars, one of the veins would be left unmined on the sub-level directly below the sill pillar (i.e., where two veins are present, only one is be mined; where three veins are present, only the outer two are mined).

The crown pillar separates the open pit from the underground stoping operation. A preliminary crown pillar with a thickness slightly in excess of the recommended 50 m was designed below the open pit floor. The lower 29.5 m (25 m of pillar and the 4.5 m drift) of the crown pillar is partially recoverable from underground near the end of underground mine life under particular mining constraints:
• Maximum stope width (HW-FW) to be 8m with cablebolt support of the stope hangingwall and roof.
• Mining will only be undertaken within the lower 29.5 m of the crown pillar during the dry season near to the end of mine life.
• Drive through water bulkheads will be installed in the overcut accesses for each level to contain water infiltration from the open pit during the wet season. A system will be put in place to drain the water from behind the bulkhead so that access can be re-established in the following dry season.
• The stopes within the crown pillar will be backfilled with cemented rock fill to act as a plug and limit water flow into the undercut and lower mining blocks.
• The overcuts above mined stopes should be tight-filled with uncemented rockfill. The purpose of the back fill is to provide long-term support for the crown pillar.
• Instrumentation should be installed in the permanent crown to monitor pillar performance.

Backfill
The following advantages of cemented rockfill (CRF) were noted as follows:
• The CRF option does not have any limitations or complexity associated with backfill delivery to any stopes in the mine plan.
• The CRF option allows most of the stopes in the mine plan to be filled with uncemented rockfill which is considerably cheaper than cemented paste fill. Hence the demand for cemented fills is
far lower with the CRF option.
• A fully automated CRF plant would allow dayshift production of backfill to meet the demand. The preferred option for the filling of completed stopes was therefore uncemented and cemented rockfill and this was carried through to the PFS level design. Based on the test work results , MineFill developed the following CRF general specifications:
• CRF density – 1.98 t/m3;
• Aggregate top size of 75 mm;
• 60% passing 10 mm;
• <5% passing 2 mm;
• Coarse stockpile – 10 mm to 75 mm;
• Fines stockpile – 2 mm to 10 mm;
• Water to cement ratio of 1.2 for end-dumped fills;
• Nominal binder content of 3% to achieve 0.25 MPa at 7 days.

Primary Crushing
ROM is trucked from the open pits and dumped directly into the crusher feed bin or stockpiled on the ROM storage pad and then reclaimed by a front-end loader to the 120 m3 ROM bin. The ore is reclaimed by an apron feeder.

The ROM is fed onto the vibrating grizzly feeder where the screen oversize is directed to the jaw crusher (Metso C120 type with a 160kW motor). The jaw crusher crushes the ore to a P80 of approximately <120 mm. The crushed ore, along with the vibrating screen undersize material, is conveyed to the SAG mill feed surge bin.

Mill Feed System
The SAG mill feed surge bin has a live capacity of 9 minutes (45 m3). The crushed material is reclaimed from the surge bin by an apron feeder onto a belt conveyor to feed the SAG mill. During crusher operation, the surge bin feed rate exceeds the discharge rate, and the feed is diverted from the bin. The diverted ore is conveyed to an emergency stockpile for reclaim by FEL during crusher or ROM feed outages. The crushed ore dead stockpile has 30 hours of storage capacity.

Grinding
The grinding circuit consists of a SAG mill (8.5 m diameter x 4.0 m EGL with a 5,300 kW variable
frequency drive) in open circuit with a small pebble recycle stream and a ball mill (5.5 m diameter x 7.4 m EGL with a 3,800 kW fixed speed drive) in closed circuit with cyclones.

The SAG mill discharge is screened by a short trommel screen that is integrated with the SAG mill. The trommel screen has an opening of 10mm (slot width). Steel balls are manually added into the SAG mill and ball mill on a batch basis as grinding media.

One magnet and one metal detector are provided to remove and detect any metal.

The SAG mill trommel undersize and the product from the ball mill discharges by gravity into the cyclone feed pump box where the slurry is pumped to the cyclones for classification. The cyclone underflow returns to the ball mill, creating a circulating load to the ball mill of approximately 250%. The cyclone overflow with a P80 of 75 µm flows by gravity to the pre-leach thickener prior to subsequent cyanidation treatment. The pulp density of the cyclone overflow is approximately 32% w/w solids.

Dilution water is added to the grinding circuit as required. Lime is added to the SAG mill to maintain a slurry pH of 10.5 or higher.

The grinding mills have 9.1 MW of total installed grinding power providing sufficient power for the duty feed rate at the predicted feed blends in the LOM plan. During times when the feed contains less than 50% of the harder fresh rock material the comminution circuit can handle a higher throughput, up to 10,000 t/d or higher, without sacrificing grind size. A pebble crusher, which was deferred from the original mill upgrade in 2019, is expected to be installed in 2022 to handle an increasing portion of fresh rock.

The Aurizona process plant currently treats the ore via a conventional cyanidation process. Runof mine (ROM) ore is processed using a conventional primary crusher and SAG-Ball mill comminution circuit followed by gravity circuit, CIL process and associated gold recovery and carbon handling circuits to produce gold doré. The process plant was upgraded during the recent construction project in 2018-2019 and recommenced operations in May 2019. The leach/CIP circuit was subsequently converted to a CIL circuit in 2020.

The process plant was upgraded to treat 8,000 t/d ore (2.9 Mt/a) based on a blend of laterite/ saprolite, transition and fresh rock. The process plant has been generally treating ore feed grades nominally ranging from 1 g/t to 2 g/t, mainly saprolite and transition ore blends, and achieving approximately 90.5% average recovery. The process plant is not expected to require any major modifications with the mine expansion plans, including the Piaba underground, howev ........