The DeGrussa Operations includes both the DeGrussa and Monty Copper-Gold Mines.

DeGrussa
The DeGrussa Mine lies within the Proterozoic-aged Bryah rift basin that is enclosed between the Archaean Marymia Inlier to the north and the Proterozoic Yerrida basin to the south. The principal exploration targets in the Doolgunna Project area are Volcanogenic Hosted Massive Sulphide (VHMS) deposits located within the Proterozoic Bryah Basin of Western Australia. The style of mineralisation is considered to be from VHMS mineralisation.

The DeGrussa sulphide lode generally strikes towards NE with a strike length of approximately 230m, very steeply dipping towards the south with a plunge generally trending SW and having a vertical extent of about 180m.

The Conductor 1 orebody lies north of DeGrussa and generally strikes ENE dipping approximately 65° to the SE with a high-grade plunge trending SW. It has a strike length of about 540m with a vertical extent of 420m.

Conductor 4 orebody lies to the east of DeGrussa and Conductor1 and are stratigraphically deeper. They have an overall strike length of 470m and vertical extent of 260m. The upper sulphide lode strikes towards ENE with an approximate dip of 47° to the SE and high-grade plunge trending SE. The lower sulphide lode strikes E, dipping approximately 45° to the S with a SW high grade plunge.

Conductor 5 orebody is east of Conductor 4 and has a strike length up to 380m and a vertical extent of 470m. The sulphide lode strikes ESE with an approximate dip of 45° to the SSW and high-grade plunge trending SE.

Monty
The Monty Mine lies within the Proterozoic-aged Bryah rift basin that is enclosed between the Archaean Marymia Inlier to the north and the Proterozoic Yerrida basin to the south. The principal exploration targets in the Springfield Project area are Volcanogenic Hosted Massive Sulphide (VHMS) deposits located within the Proterozoic Bryah Basin of Western Australia. The style of mineralisation is considered to be from VHMS mineralisation.

The Monty massive sulphide mineralisation generally strikes east and steeply dips to the northwest between 75-85°.

Production was sourced from the DeGrussa and Monty Mines with the mine remaining in balance between production and back-fill. Mine production rates from DeGrussa were slightly lower than planned due to contractor equipment and manning constraints. Monty mine production rates continued to exceed forecast.

The mining operations strategy adopted for the DeGrussa and Monty operations targets the blending of the material from both mines and scheduling to have both life of mine plans completed as close to the same time as practicable. The updated underground Ore Reserve continues to support this strategy with DeGrussa producing approximately 1.2Mtpa and Monty producing approximately 0.4Mtpa.

DeGrussa Mine
The underground mining method is long-hole open stoping (both transverse and longitudinal) with minor areas of jumbo cut and fill or uphole benching in some of the narrower areas. The primary method of backfill is paste fill. The sequence aims for 100% extraction of the orebody.

Primary mining methods employed are sub-level open stoping (SLOS) and long-hole open stoping (LHOS) with fill. Cut and fill techniques are also employed in remnant areas. Primary fill material is paste with minor use of cemented rock fill and rock fill when appropriate.

Monty Mine
The underground mining method is long-hole open stoping (both transverse and longitudinal) with minor areas of jumbo cut and fill or uphole benching in some of the narrower areas. The primary method of backfill is paste fill. The sequence aims for 100% extraction of the orebody.

Primary mining method employed is long-hole open stoping (LHOS) with fill. Primary fill materials are cemented aggregate fill (CAF) and rock fill.

The DeGrussa Copper Mine commenced commissioning of its 1.5Mtpa concentrator in September 2012. During its first 18 months of operation, the milling circuit experienced numerous issues. The majority of these problems originated from the very fine feed particle size distribution fed into the processing plant.

Mill throughput increased following primary screen and pebble crusher installations, and SAG mill optimisation in FY15.

Currently the DeGrussa processing plant has a capacity of 1.6Mtpa.

Initiall design (2012)
The processing plant includes primary crushing, primary closed circuit milling, secondary closed circuit milling, conventional three stage flotation including concentrate regrind and tailings disposal.

The design of the DeGrussa grinding circuit is a typical SAG and ball mill (SAB) type. A single Metso C140 jaw crusher operating with a closed side setting of 125mm crushes pre-blended run of mine (ROM) material to 80% passing (P80) 146mm which is then conveyed to a 4,200t primary crushed ore storage bin. The material is reclaimed via one of three vibrating feeders which deliver ore to the primary mill. The installed primary mill is an Outotec 7.30m x 3.35m effective grinding length (EGL) grate discharge SAG mill with 3.4MW installed power. The mill is also installed with Turbo Pulp Lifters (TPL) in lieu of standard radial pulp lifters.

Once material is discharged from the primary mill the slurry is pumped to a cluster of four CVX500 cyclones which are designed to achieve a P80 of 180µm. The cyclone underflow gravitates to the SAG mill feed chute via the primary flash flotation cell and the cyclone overflow gravitates to the ball mill discharge hopper. This slurry, along with the ball mill discharge, is pumped to the secondary cyclone cluster including twelve 250CVX cyclones which are designed to achieve a P80 of 45µm. Secondary cyclone underflow gravitates to the ball mill feed chute via the secondary flash flotation cell whilst secondary cyclone overflow gravitates to the flotation circuit.

The installed secondary mill is an Outotec 4.7m x 7.5m grate discharge ball mill with 2.6MW installed power. The ball mill is also installed with Turbo Pulp Lifters (TPL) in lieu of standard pulp lifters.

Grinding Improvement (2015)
• Primary cyclones replaced with screen to improve mass transfer to secondary milling circuit for particle size distribution control and optimal chalcopyrite liberation for flotation;
• Pebble crusher installed for breakage of critical size particles in the primary milling circuit;
• Wear improvement initiatives to push out maintenance shutdown frequency.

The DeGrussa processing plant has a capacity of 1.6Mtpa. DeGrussa producing approximately 1.2Mtpa and Monty producing approximately 0.4Mtpa.

DeGrussa
The underground Ore Reserve estimate is based on an operating 1.6 Mtpa process plant producing a 24.5% copper-concentrate that contains gold and silver. Mill feed is sourced from DeGrussa and Monty with DeGrussa supplying approximately 1.2 Mtpa. DeGrussa copper recovery models based on Copper:Sulphur ratio were used in the determination of the underground Ore Reserve estimate. Average weighted LOM copper recovery is 91.9%. Gold recovery was fixed at 47%. Silver recovery was fixed at 49%.

Monty
The underground is based on an operating 1.6 Mtpa process plant producing a 24.5% copper concentrate that contains gold and silver. Mill feed is sourced from DeGrussa and Monty with Monty supplying approximately 0.4 Mtpa. Monty copper recovery model is based on Copper:Sulphur ratio were used in the determination of th ........