The Cowal gold deposits (E41, E42, E46, Galway, and Regal) occur within the 40km long by 15km wide Ordovician Lake Cowal Volcanic Complex, east of the Gilmore Fault Zone within the eastern portion of the Lachlan Fold Belt. There is sparse outcrop across the Lake Cowal Volcanic Complex and, as a consequence, the regional geology has largely been defined by interpretation of regional aeromagnetic and exploration drilling programs.

The Lake Cowal Volcanic Complex contains potassium rich calc-alkaline to shoshonitic high level intrusive complexes, thick trachyandesitic volcanics, and volcaniclastic sediment piles. The Cowal Complex is a strong regional magnetic high anomaly with a sharp linear western margin, represented by the Gilmore Fault Zone, separating the Lake Cowal Volcanics from the relatively low magnetic response of sediments to the west.

Similar Ordovician magmatic rocks are found over a large area of the eastern Lachlan Fold Belt and are commonly associated with copper-gold mineralisation (e.g., Northparkes, Cadia, Peak Hill, and Gidginbung). The main diorite intrusion at E42 has a K-Ar dating of 456 ± 5 Ma (Early to Mid- Ordovician). The gold deposits at Cowal are structurally hosted, epithermal to mesothermal gold deposits occurring within and marginal to a 230 m thick dioritic to gabbroic sill intruding trachyandesitic volcaniclastic rocks and lavas.

The overall structure of the gold deposits is complex but in general consists of a faulted antiform that plunges shallowly to the north-northeast. The deposits are aligned along a north-south orientated corridor with bounding faults, the Booberoi Fault on the western side and the Reflector Fault on the eastern side (the Gold Corridor).

The mineralisation at the Cowal Mine comprises four deposits: GRE46, E41, E42 and E46.

The GRE46 deposit is subdivided into the open pit and underground resources. The GRE46 zone trends north-south, dips vertical to -70° west, and extends approximately 1,650m along strike, 175m across strike and up to 800m down dip. Individual lenses in the GRE46 mineralised zone are 1.0m to 15m wide, 25m to 250m long, and extend 50m to 200m down dip. Lenses consist of narrow high-grade quartz carbonate, pyrite and base metal veins controlled within a structural north-south corridor, occasional zones of grade enrichment occur in dilatant structures within the deposit known as Quartz Sulphide Breccias. Host lithology varies from poorly mineralised massive intrusive diorites and fine volcaniclastic sediments through to the preferential host of Trachyandesite lava, lenses of coarse to conglomeritic volcaniclastic sediments to the south and the Dalwhinnie Andesitic sill in the east.

The E41 West mineralisation strikes north-northeast and dips -70° east, and measures 750m along strike and 250 m across strike. Individual mineralised zones are 35 m to 50m wide and extend down dip for 125m. The E41 East mineralisation strikes east-west and dips -35° to -80° south, and measures 475m along strike and 500 m across strike. Individual mineralised zones are 35m to 50m wide and extend down dip for 225m.

The E42 deposit dips -35° to -45° to the south west with an approximate extent of 850m by 850m and extends 500m down dip. Mineralisation is contained within small discontinuous veins contained within larger mineralised envelopes approximately 50m wide.

The E46 deposit mineralisation trends north-northeast, dips -40° west to flat-lying, and measures approximately 650m along strike and 17m across strike. Individual zones are approximately 50m wide and extend 200m down dip.

The Cowal operation is currently an open pit mining operation utilising conventional drill and blast, load and haul methodologies, mining nominally 9m benches as 3 x 3m flitches. Mining commenced in 2005 and processing started in 2006. Mining is carried out with a company-owned fleet of mining equipment. Ore is hauled by truck from the pit face to either a stockpile area or directly fed into the primary crusher.

Primary crushing:Metso 54-75 Superior MK-II gyratory crusher

Grinding Plant Equipment:FFE 36' x 20.5' SAG. FFE 22' x 36.5' ball mill

Grinding Media:Forged steel, 125mm balls (SAG mill), 105mm balls (ball mill)

Screening plant/equipment:Schenck Vibrating (SAG discharge), Delkor Linear (COF)

Recycle crusher:2 x Sandvik H6800 hydrocone cone crushers.

The Cowal processing plant was commissioned in May 2006 and consists of crushing, two stage grinding, sulphide flotation, regrind and CIL recovery. The plant currently processes around 9.0Mtpa.

Mineral liberation/recovery
Method: flotation, regrind, CIL of floatation concentrate and tail.
Equipment: 2 x SK1200 and 10 x OK200TC (flotation), Metso Vertimill (VTM1000WB), 2 x Metso 355kW SMDs, Con Pre-ox - 4,000m3, 2 x 4,000m3 Con Leach, 6 x 1,000m3 Con CIL, 7 x 2,400m3 Tail CIL.

Refining - 10t AARL elution circuit, ANSAC regeneration kiln.
Gravity Circuit - Falcon concentrator / Acacia Reactor.