ASX-listed gold producer and explorer Regis Resources has unveiled its plans to develop the Garden Well Main and Rosemont Stage 3 underground mines in Western Australia.

This initiative is set to increase the firm's underground ore reserves and contribute to a steady state annualised gold production target of between 100koz to 120koz from FY27.

Garden Well Main, situated nearly 750m north of the existing Garden Well South underground mine, has a mining inventory that includes 36% indicated mineral resources, 24% inferred mineral resources, and 41% exploration target.

This amounts to 3.2Mt at 2.8g/t Au for 295koz of contained gold, using a 2.2g/t cut-off grade.

The new Garden Well Main underground mine will tap into a mining domain located beneath the current Garden Well open pit, with mineralisation identified from 250m to 500m below ground level.

The estimated pre-production capital ranges from A$75m ($49.7m) to A$95m ($62.9m), with development starting immediately and the first ore expected in Q1 FY26.

It is expected to produce 60koz to 70koz of gold annually, with a life of mine (LOM) All-In Sustaining Cost (AISC) estimated at $2,050-2,150 per oz.

Regis has been operating underground at Rosemont since 2019, encompassing the Rosemont Main, Central, and South areas.

The Rosemont Stage 3 expansion, located 100m south of the current operations, will deepen the Rosemont South area by 300m to a total depth of 700m below ground level.

This extension is expected to support reserve growth and life extensions, with a mining inventory of 1.7Mt at 2.8 g/t Au for 157koz contained gold, including a probable ore reserve of 490kt at 2.6g/t Au for 41koz.

The remainder consists of inferred mineral resources and exploration targets. With pre-production capital estimated at $45m to $55m, development is underway, and the first ore is also scheduled for Q1 FY26.

The mine aims to reach an annualised gold production target of 40koz to 50koz, with a project LOM AISC estimated at $2,400-2,500 per oz.