O’Brien Gold Project, Canada

The O’Brien gold project in Québec, Canada is being developed by gold exploration company Radisson Mining Resources.

The company announced a positive Preliminary Economic Assessment (PEA) for the gold project in July 2025.

The PEA projects an 11-year mine life with an average steady-state gold production of 70 koz/annum (Years 2-8).

The initial capital expenditure for the mining project is projected at C$175m ($126.47m), with life-of-mine sustaining capital estimated at C$173m.

The mined material is planned to be processed at the Doyon gold mill, which is part of IAMGOLD’s Doyon-Westwood mine complex. A milling assessment has confirmed the potential viability of processing material from the O’Brien site at this neighbouring facility.

O’Brien Gold Project Location

The O’Brien Gold Project is situated in the Abitibi region of northwestern Québec, around 1km north of Cadillac.

The project is accessible via gravel roads from provincial Highway 117. It is located roughly 50km east of Rouyn-Noranda, 30km west of Malartic, and 55km west of Val d’Or.

The gold project encompasses a contiguous block of 146 exploration claims, covering 7,137.74 hectares, along with a mining concession of 288.19 hectares.

Doyon mill, which will process the mined material, is positioned 21km west of O’Brien and can be reached directly via Trans-Canada Highway 117.

Geology and Mineralisation

The O’Brien Gold Project is situated along the Cadillac-Larder Lake Fault Zone (CLLFZ) in the southeastern Cadillac Mining Camp (CMC) of Québec. This structure, associated with around 40 gold deposits, spans a 25km stretch from the former Mouska mine to the former Lapa-Cadillac mine.

The project is spread across the Piché Group volcanic rocks and the CLLFZ, with most gold mineralisation occurring in the Piché Group, except for the Vintage Zone in the Cadillac Group. Historical gold production at the O’Brien mine came primarily from four high-grade quartz veins in the eastern part, yielding significant visible gold.

Current mineralization is defined in two areas- O’Brien East, hosting Zone 36 East and the Kewagama area, and O’Brien West, an extension of the historical Thompson-Cadillac mine.

Zone 36 East contains the majority of current resources, with narrow, high-grade veins similar to those historically mined. In the Kewagama area, gold is found in smaller veins within the Piché Group.

The O’Brien deposit is characterised as a greenstone-hosted quartz-carbonate vein deposit, a subtype of lode gold deposits also known as mesothermal or orogenic gold deposits.

Mineral Resource Estimate

The Mineral Resource Estimate (MRE) for the O’Brien project, originally disclosed in March 2023, was based on 325,509 metres of drilling completed by the end of 2022.

Indicated resources totalled 1,517,000 tonnes at a grade of 10.26 g/t Au, amounting to 501,000 ounces, using a 4.5 g/t gold cut-off grade.

Inferred resources stood at 1,616,000 tonnes with a grade of 8.66 g/t Au, totalling 446,000 ounces at the same cut-off grade.

Mining at O’Brien Gold Project

The PEA outlines an 11-year mine life, involving the extraction of 4.57 million tonnes of mineralised material and 3.31 million tonnes of waste rock.

The mining operation will be conducted entirely underground using long-hole stoping with cemented rock backfill.

Access to the mine will be via twin 4.5m by 4.5m ramps extending to a depth of 950m, with 86km of development.

Equipment will include 20-tonne trucks, with rock haulage aided by vertical conveyors transporting materials from the 300m level to a surface run-of-mine pad.

The design does not use any infrastructure from the historic O’Brien Mine, but a shaft at the historic Kewagama Mine site will be reused for ventilation. Mined material will be trucked to the processing facility.

During Years 2 to 8, when the gold project is in steady-state operation, production from stopes will average 1,160 tonnes per day (tpd).

Processing

The metallurgical results showed that gold recoveries ranged from 86% to 96% based on various flow sheet options compatible with the Doyon mill, requiring minimal additional capital.

The Doyon mill, currently operating at about 3,000 tonnes per day (tpd), uses a conventional cyanidation process. It processes material with a primary crusher and a two-stage SAG/Ball mill grinding at 75 µm (P80), followed by leaching through Carbon-in-Leach and Carbon-in-Pulp circuits. The PEA proposes a Gravity-Flotation-Regrind-Leach flow sheet, with Radisson making an investment to upgrade the inactive gravity and flotation circuits at Doyon.

The life-of-mine average gold recovery with the proposed flow sheet is estimated at 87%, based on 90% recovery for the O’Brien sample with an average grade of 6.3 g/t Au. A grade-recovery model applied to the PEA’s expected average head-grade of 5.0 g/t Au, after processing low-grade development materials, supports this estimate.

O’Brien’s gold mineralisation is linked with pyrite and arsenopyrite. The metallurgical program found average arsenic levels of 0.4% to 0.5% in whole rock and 4.6% in flotation concentrate, which is pertinent for tailings deposition or selling concentrate to an off-take agent.

These levels align with benchmarks from similar projects in Québec’s Abitibi region and offtake thresholds for high-grade gold concentrates. The PEA plans for tailings deposition post-leach without a segregated impoundment, though additional capital would be required if one becomes necessary.

Contractors Involved

The O’Brien Gold Project PEA was completed by Ausenco Engineering Canada as lead consultant.

Ausenco was responsible for metallurgy, processing design, infrastructure and financial modelling. InnovExplo carried out the mine design and mine scheduling, while BBA was responsible for water management, surface facilities, and a review of the project’s environmental assessment procedure and permitting requirements.

SLR Consulting (Canada) prepared the gold project’s MRE.