The Mount Isa copper orebody as a whole covers an extent of over 4kms and a vertical extent of 1800 metres (Lilly et al, 2017).

Cu mineralisation occurs in extensive zones of silica-dolomite alteration. The main mineralised bodies include the 1100, 1900, 200, 500, 650, 3000 and 3500 orebodies.

The Cu orebodies fall into two broad orientation groups: the 500, 1900N and 3500 orebodies are broadly stratabound and dip west at between 60 and 80 degrees; and the 1100, 1900S, 3000, 200 and 650 orebodies dip moderately to steeply west-southwest (ie with an approximate 15 degree sinistral rotation from the orientation of bedding) (Miller, 2007). The 1100, 1900, 3000 and 3500 orebodies show local plunge variations which are broadly parallel to the intersection between bedding in the Urquhart Shale and the underlying basement contact with the Eastern Creek Volcanics. The 1100 and 1900 orebodies show a subhorizontal plunge, while the 3000 and 3500 orebodies plunge moderately to the north. The 200, 500 and 650 orebodies also show a moderate north plunge.

The Mount Isa Cu and Zn-Pb-Ag deposits are hosted within the Mesoproterozoic Urquhart Shale of the 1670Ma Mount Isa Group.

Major Host Rock: Variably laminated mudstones and siltstones which vary from siliceous to carbonate-rich, with significant and extensive accumulations of fine grained pyrite.
Minor Host Rock: A minor amount of copper mineralisation and associated alteration occurs in the Spear Siltsone, which overlies the Urquhart Shale. Copper mineralisation and silica dolomite alteration also encroach slightly on the underlying Native Bee siltstone in the 3500 orebody.

Mineralisation in the copper orebodies occurs as a mixture of veins and wallrock replacement, Miller (2007) noted that Cu-hosting structures have a steep S-pitching intersection with bedding and are consistent with sinistral-reverse slip on bedding.

Cu mineralisation occurs in association with an extensive zone of “silica-dolomite” alteration. The high grade core of the copper deposit is hosted in brecciated and intensely silicified Urquhart Shale. The high grade siliceous zone is surrounded by a zone of dolomite.

Mount Isa X41 and Enterprise Copper Mine:
Mineralisation occurs generally as breccia hosted massive to disseminated chalcopyrite in “silica dolomite” altered pyritic dolomitic siltstone.

Black Rock Cave:
Copper mineralisation occurs generally within a Chalcocite Zone that lies above the Leached Primary material. The zone is interpreted to lie outside of the SilicaDolomite alteration.

The copper orebodies are accessed via two vertical shafts as well as a decline from surface. The X41 shaft services the southern portion (X41 mine) of the copper operations, whilst the R62 shaft services the northern deep portion (Enterprise mine) of the copper operation. The decline is used for the movement of large equipment as well as for egress. A further two vertical shafts are used for hoisting of ore. These are U62 and M62 shafts. M62 shaft is an internal shaft and hoists ore from the Enterprise mine. The ore from both Enterprise mine and X41 mine is hoisted up the U62 shaft to surface.

In the Mount Isa copper mine orebodies, sub-level open stoping, coupled with secondary and tertiary stoping is used to extract the ore. Blocks of ore 40 m-wide, 40 m-long at full orebody height are removed. To do this, 5.0 m x 5.0 m drilling sublevels are developed at 40 m intervals. At the bottom of the stope, a number of drawpoints are mined and equipped to extract the ore.

The broken ore falls to the bottom of the stope, and is extracted at the drawpoints by diesel-powered LHD wheel loaders with a 6.1 cu m bucket capacity. Then the ore is either tipped directly into the passes to feed the crusher or, if the stope is a long way from the crusher, into articulated haulage trucks. After crushing, the ore is sent via a 1.6 km cable belt to the U62 hoisting system, where 36 t skips take it to the surface.

The Enterprise and X41 copper mines are backfilled using a mixture of cement and tailings called ‘paste’. The slurry is a mixture of Portland cement and concentrator tailings, whilst the rock is sourced from surface stockpiles, from the heavy media rejects from the lead concentrator, or slag waste from the copper smelter. The mixture sets into a hard, rock-like formation, providing a stable face to enable extraction of the adjacent ore pillar.

Once the ore is loosened by drilling and blasting, it is mucked, crushed and hauled to the surface where it is put through the concentrating process.

The Black Rock Cave project further develops the existing copper resource at Mount Isa Mines, and will use sub-level caving to improve the economic viability of extracting ore from the existing ore body.

The first production ore from the Black Rock Cave has come online following the development of the mining levels, with the underground ore body expected to yield around 1.8 million tonnes of copper ore from 2020 to 2024.

Copper ore is mined in the X41 and Enterprise underground mines, where it is roughly crushed, then hoisted to the surface for processing. From here, it is fed through a series of ball mills that grind the rock into a fine dust.

This dust is then mixed with water and reagents in the concentrator’s flotation circuit. The reagents help to separate the valuable mineral content from waste rock and iron sulphide particles like pyrite – or “fools gold”. Air is forced through the slurry creating bubbles, which float to the surface and attract and bind to the copper particles. The glossy, mineral-laden “froth” is then skimmed off the top and dried. The greenish powder that remains once the water content of the froth has evaporated is copper concentrate. But it’s not pure copper yet, it’s a copper iron sulphide, made up of about 35 per cent pure copper.

Copper concentrate is fed into the ISASMELT furnace, where it is heated to 1185 degrees Celsius. This process melts the c ........