The Rosebery volcanic-hosted massive sulphide (VHMS) deposit is hosted within the world-class Mt Read Volcanics. This Cambrian volcanic belt is an assemblage of lavas, volcaniclastics and sediments deposited in the Dundas Trough between the Proterozoic Rocky Cape Group and the Tyennan Block.

Mineralisation occurs as stacked stratabound massive to semi-massive base metal sulphide lenses. The host lithology lies between the Rosebery Thrust Fault and the Mt Black Thrust Fault which all dip approximately 45° east. Ore mineralogy consists predominantly of sphalerite, galena, chalcopyrite with electrum and minor tetrahedrite.

The orebody has experienced numerous events of folding, shearing and thrusting particularly in the late Cambrian and early Devonian. Lenses in the southern portions of the deposit have experienced metasomatism and replacement by a deep Devonian granitoid resulting in variation of the mineralogy, structure and alteration in these lenses.

Dimensions
The Rosebery Mineral Resource extends from -300mE to 1750mE, -800mN to 3325mN, 1650mRL to 3500mRL (Rosebery Mine Grid coordinates) and is currently open to the north, south and at depth.

Individual lenses vary in size from a few hundred metres up to 1,000m along strike and/or down-dip, with a total strike length of mineralisation reaching approximately 4,000m.

The mineralised lenses range from a minimum of 0.2-0.3m, maximum of 12-36m with an average true thickness of 3-6m.

Mining production is carried out by long-hole open stoping with decline access. Stoping is conducted through both longitudinal retreat and transverse methods.

Mining lenses are divided into panels and are mined using a bottom-up sequence with a number of levels being retreated simultaneously, either towards or away from level access drives. The nature of this mining sequence causes fluctuations in the grade profile in the short-term.

Backfilling of stope voids is carried out using two methods; cemented rock fill (CRF), and rock fill (RF). Up-hole (Crown) retreat stopes are left as open voids due to lack of access for fill placement. These open voids do not result in regional instability. The current mine closure plan identifies approximately 500kt of waste rock that has been stockpiled on the surface that is available for use as backfill when development material becomes insufficient to meet demands.

Average stope strike lengths of 15m were used in W and X Lens while the other lenses used 20m. The height set to 20-25m (floor to floor) and the minimum mining width of 4.5m.

Access to the orebody is through a decline 5.5m H x 5.5m W at a 1:7 gradient. The approximate horizontal standoff distance between the stoping footwall and major infrastructure; i.e. - stockpiles, vent rises, escape-ways and declines is 65-70m.

The current deepest production drive is approximately 1,700m below surface and the deepest economic drill int ........

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