The Ernest Henry Deposit is an Iron Oxide Copper Gold (IOCG) hosted within a sequence of moderately SSE-dipping, intensely altered Paleoproterozoic intermediate metavolcanic and metasedimentary rocks of the Mt Isa group. Copper occurs as chalcopyrite within the magnetite-biotitecalcite-pyrite matrix of a 250 x 300 m pipe like breccia body. The breccia pipe dips approximately 40 degrees to the South and is bounded on both the footwall and hanging wall by shear zones. The main orebody starts to split from the 1575 level into a South-East lens, and from the 1275 level into the South-West lens. Both lenses are separated from the main orebody by waste zones, termed the Interlens and South-West Shear Zone, respectively. The orebody is open at depth.

The Ernest Henry copper-gold deposit is hosted in a hydrothermal breccia pipe plunging at roughly 45 degrees to the south, bounded between two shear zones. At depth, the orientation of shearing appears to be having a greater effect on the orebody and the primary mineralised lenses are becoming more elongate north-south, separating into discrete pods and lenses.

The Ernest Henry deposit is hosted entirely in felsic intermediate metavolcanic rocks, within a unit of the Mount Fort Constantine Volcanics, circa 1800 to 1750 million years. Regionally these lithologies lie adjacent to a large meta-diorite body which traverses the deposit from the south-west to the north-east. Timing of mineralisation at the Ernest Henry d ........

Ernest Henry is an underground mining operation employing sub-level caving ore extraction method. There is also an underground primary crusher and ore handling system. Ore is brought to surface via a 1,000m hoisting shaft with a hoisting capacity in excess of 6Mt ore per annum. The operation also has an effective and sophisticated above and below ground water management system.

The mine design uses 25 m sublevel spacing, 15 m drive spacing (centre to centre), 6 m wide cross cuts and a standard SLC drill and blast design. These design parameters are in line with benchmarked mines and assessed to be geotechnically stable.

A minimum mining width for cave propagation is in the order of 140 m based on empirical cavability assessments.

All major infrastructure for the mine has been constructed including underground crusher, conveyor system, hoisting shaft, pumping and ventilation systems. Access to the underground mine is via an in-pit portal and decline.

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