At Northparkes, the Goonumbla Volcanics are a folded sequence of trachyandesitic to trachytic volcanics and volcaniclastic sediments that are interpreted to have been deposited in a submarine environment.

In the Northparkes region the Goonumbla Volcanics have been intruded by equigranular monzonite stocks. Quartz monzonite porphyry pipes and dykes, some of which are associated with mineralisation, have intruded both the Goonumbla Volcanics and the equigranular monzonite stocks.

The Northparkes deposits are typical porphyry copper systems in that the mineralisation and alteration are zoned around quartz monzonite porphyries. The porphyries form narrow (typically less than 50 metres in diameter) but vertically extensive (greater than 900 metres) pipes. Mineralisation extends from the porphyries into their host lithology. The E26 and E48 deposits range from 60 to 400m in diameter (>0.4% copper) and extend vertically for more than 900m.

Sulphide mineralisation occurs in quartz stockwork veins, as disseminations and fracture coatings. Highest grades are generally associated with the most intense stockwork veining. Sulphide species in the systems are zoned from bornite dominant cores, centred on the quartz monzonite porphyries, outwards through a chalcopyrite dominant zone to distal pyrite. As the copper grade increases (approximately >1.2% Cu), the content of covellite, digenite and chalcocite associated with the bornite mineralisation also increases. Gold normally occurs as fine inclusions within the bornite.

The alteration zonation is complex but tends to be zoned around the quartz monzonite porphyries with a central K-feldspar altered zone surrounded by biotite magnetite alteration. The K-feldspar alteration zone at E26 is well developed and extends up to 100 metres outboard from the porphyry. This is in contrast to E22, E27 and E48 where K-feldspar alteration is generally less than 10 metres outboard from the porphyries. The biotite magnetite zone is strongly developed at the E22, E27 and E48 deposits, and forms a zone up to 200 metres from the porphyry. It is this biotite-magnetite zone that forms the distinctive annular magnetic features at E22 and E27.

A central white sericite-quartz +/- alunite alteration zone occurs at E26, and to a lesser extent at E48, and is generally associated with the high grade zones within the deposits. At E48, an alteration assemblage of hematitesericite+/ carbonate occurs both within and proximal to the mineralisation.

In 2015 our E48 Lift 1 block cave mine became the world's most automated underground mine with 100% automated loaders. The driver-less loaders run themselves – moving and dumping the ore.

We began production from our E26 Sub Level Cave in 2016. Sub Level Caving is a mining method during which slim blocks of ore are released by successively blasting and undermining small panels.

In order to recover copper and gold from the ore, it is processed through several stages including grinding, flotation, concentrate thickening and finally filtration.

Moisture from waste materials is extracted and recycled in our ore processing plant. Tailings are then transferred to our Tailings Storage Facilities, creating a dry surface. To reduce dust, we are growing crops on the surface of the facilities.

The concentrate is transported to port by road and rail in shipping containers. These containers are then tipped directly into the ship using a specially designed crane attachment called a rotainer. The concentrate is not removed from the containers until it is loaded into the ship ready for its final journey to our customers.