The Spence porphyry copper deposit is related to three stocks of dacitic porphyries and tourmaline-bearing hydrothermal breccias, which were emplaced in andesitic volcanic rocks of the Upper Cretaceous–Lower Tertiary. Laser 40Ar/39Ar plateau ages in magmatic biotites of pre- and post-mineralization dacitic stocks show evidence that hypogene mineralization (chalcopyrite, pyrite, molybdenite, and lesser amounts of bornite and tennantite) occurred between 56 and 57 Ma.

Unconsolidated gravel deposits and a leach cap cover an oxidation blanket characterized by atacamite, chrysocolla, and minor brochantite, in which the Cu-hydroxychloride is by far the dominating mineral. Underlying the oxide zone is a well-developed chalcocite- and lesser covellite-bearing supergene enrichment blanket.

Spence is enriched and oxidised porphyry copper deposit containing in situ copper oxide mineralisation that overlies a near-horizontal sequence of supergene sulphides, transitional sulphides, and finally primary (hypogene) sulphide mineralisation.

Representative samples from pit walls and drill cores were selected in order to cover most of the hypogene and supergene zones, including chalcopyrite from the hypogene-enriched sulfides and hypogene zones, chalcocite from the supergene-enriched sulfides and hypogene-enriched blankets, chrysocolla from the oxide blankets, and atacamite from the oxide zone within the host rocks and gravels and leach cap.

Spence is Open-cut.

Spence produces copper cathodes and, since December 2020, copper concentrate.

The supergene oxide and sulphide material is currently processed in a leaching operation whereas the hypogene sulphide material provides ore feed to a new conventional sulphide milling and flotation concentrator plant.

Processing facilities including:
* Primary/Secondary/Tertiary crushing circuit. Crushing facilities feed concentrator and leaching processes;
* 1 copper concentrator plant with 95 ktpd capacity. The plant produces copper and molybdenum concentrates (by-products: gold and silver);
* molybdenum plant;
* a 1,000 lps desalinated water plant under a Build, Own, Operate, Transfer (BOOT) agreement;
* Dynamic leach pads: Oxide ore (chemical leaching) and sulphide ore (bacterial leaching);
* Solvent extraction and electrowinning plant. Nominal capacity of tank house: 200 ktpa copper cathode.

On the basis that tailings storage facility anoma ........