Individual mining operations, including mining at Fifteen Mile Stream, have focussed on quartz-vein hosted gold deposits within the Goldenville Formation, typically associated with the limbs and hinges of anticlines. This setting is often referred to as ‘Meguma style’ gold mineralization and a number of workers have drawn parallels with a similar style of gold mineralization in the Victorian Goldfields of eastern Australia (e.g. Christie et al, 1999) .

At Fifteen Mile Stream, the highest gold grades are typically associated with beddingparallel tabular quartz veins. However, the host rock material between quartz veins also carries significant gold grades. It is the quartz vein hosted gold mineralization augmented by disseminated style mineralization that forms the basis of a geological model associated with the ongoing exploration and development of the Fifteen Mile Stream gold deposit.

Mineralization at Fifteen Mile Stream is focused in the hinge of a regional anticline and generally conforms to a saddle-reef style model where veins and related alteration occur in bedding-parallel structures resulting from folding. Fold related strain is focused within the softer meta-mudstone units thus mineralization is generally controlled by stratigraphy, with bedding-parallel quartz veins and related alteration mainly confined to meta-mudstone intervals. True saddle-reef quartz veins do not occur within any of the mineralized zones. However a thick bedding-parallel quartz vein referred to as the ‘Big Bull Vein’ in the centre of the district is interpreted as a saddle-reef vein.

Gold mineralization within the FMS is largely hosted by bedding-parallel quartz veins that are buckled and folded with the enclosing sedimentary beds. Two main vein styles include massive milky white veins and laminated veins, the latter typically smoky in colour and characterized by vein-parallel inclusions. Weak wall rock alteration spatially associated with the veins includes carbonitization and, locally, sericitization. Associated sulphide mineralization includes arsenopyrite, pyrite and pyrrhotite with the pyrrhotite frequently hosting minor chalcopyrite. Arsenopyrite modally comprises trace amounts of around three percent and occurs as equant, subhedral grains 1-5mm in diameter.

Gold occurs as coarse (>1mm) grains in quartz veins and locally as finer (<1mm) grains in wall rock. Coarse gold in veins is commonly found at vein-wall rock boundaries and with sulphide minerals.

Anomalous gold values in the range of 0.1 to 4.0 gpt Au were frequently returned for intervals without any quartz veins or visible gold and the nature of this mineralization is not well understood. However, high gravity recovery for similar mineralization at the Beaver Dam and Touquoy deposits suggest the gold occurs as free gold, possibly associated with sulphide minerals.

Mineralization in the Hudson Zone is confined to the Egerton-McLean stratigraphy and is similar in character to that noted in the Egerton-McLean Zone i.e. coarse gold in veins and finer free gold in altered wall rock. The Fifteen Mile Stream Anticline in the Hudson Zone is overturned as in the Egerton-McLean Zone. However the fold in the Hudson area is tight with a narrow, angular hinge and lacks the complex decametre folds that characterized the Egerton-McLean Zone. The lack of folding in the hinge area results in a smaller mineralized zone due to the lack of repetition.

Historic drilling in the 149 East Zone documented a few auriferous intervals. Recent drilling in this area in late 2009 by Acadian (Graves, 2010) intersected a wide interval of predominantly green banded meta-mudstone similar in appearance to the Orient Mudstone in the hinge of the anticline. The core lacks abundant veining and alteration typically associated with mineralization in the Egerton McLean Zone. The historic mineralized intervals appear to be represented by minor dark meta mudstone in the recent drill holes. Notably, a grain of gold was present within the green banded mudstone in the absence of veins or alter-ation. As in the Hudson Zone the fold in this area is tight, relatively horizontal and does not show evidence of significant fold repetition.

The Plenty Zone occurs on the south limb of the Fifteen Mile Stream Anticline approximately 400 m southwest of the Egerton-McLean area. The mineralized zone is controlled by stratigraphy and bedding-parallel quartz veins that are steeply dipping. Gold was reported to occur in quartz veins and argillite (meta-mudstone) (Morris, 1986).

Mining is based on conventional open pit methods suited for the project location and local site requirements. The mining fleet will include diesel powered down the hole (DTH) drills with 144 mm bit size for production drilling, diesel-powered RC drills for bench- scale grade control drilling, 5 m3 bucket size diesel hydraulic excavators and 7 m3 bucket sized wheel loaders for production loading, and 64 t payload rigid-frame haul trucks and 41 t articulated trucks for production hauling, plus ancillary and service equipment to support the mining operations. In-pit dewatering systems will be established for each pit. All surface water and precipitation in the pits will be handled by submersible pumps.

Mine operations will continue at Touquoy and will move to Beaver Dam once the Touquoy open pit is exhausted in 2023.

Two independent stand-alone open pit operations at Fifteen Mile Stream and Cochrane Hill will run concurrently with the Touquoy and Beaver Dam operations. At Fifteen Mile Stream, ore will be hauled to a crusher that will be located 1,500 m southeast of the pit, which will feed the process plant. Waste rock will be split into potentially acid-generating (PAG) and non-potentially acid generating (NPAG) material and deposited into WRSFs to be situated 700 m south of the pit or will be used as rock fill in construction of the TMF to be located 1,700 m east of the pit.

At Fifteen Mile Stream, the Egerton–MacLean pit is split into south and north phases with the higher-grade and lower strip ratio south phase mined ahead of the north phase. The Hudson and Plenty pits are mined as one phase each. Starting in 2021 an 8.5-year mine production schedule is developed.

A process facility with a nominal treatment rate of 2.0 Mt/a has been designed to recover and concentrate gold from ore mined at the proposed Fifteen Mile Stream open pit. The plant operates two shifts per day, 365 d/a at an overall plant availability of 92%. The process plant will produce a gold concentrate to be transported and further treated at the Touquoy process plant.

Run of mine ore will be hauled from the open pit to a crushing facility that includes a jaw crusher as the primary stage and cone crushers for secondary and tertiary size reduction.

Crushed ore will be ground by a ball mill in a closed circuit with cyclones. Centrifugal gravity separation units will be installed to obtain GRG from the primary cyclone underflow stream. Gravity separation units will treat 50% of the ball mill circulating load. The overflow from the primary cyclone with P80 of 150 µm will report to conventional rougher flotation cells. Rougher flotation concentrate will be subject to one stage cleaning mainly to decrease the amount of concentrate prior to thickening.

Final tailings from the conventional flotation will be pumped to the TMF. Gold concentrate will be thickened and pressure-filtered before being transported by truck to the Touquoy process plant.

The process plant will consist of the following unit operations:

• Crushing:
- Primary crushing by jaw crusher;
- Secondary crushing by cone crusher;
- Tertiary crushing by cone crusher;
- Associated conveying, screening and dust suppression systems;

• Grinding and flotation:
- Grinding by ball mill with a primary cyclone;
- Gravity concentrator for recovery of GRG;
- Flotation by conventional flotation;
- Cleaner flotation;

• Dewatering and concentrate handling:
- Concentrate dewatering and load out;
- Tailings disposal to the TMF.