Summary:
The Jervois project lies within the eastern part of the Arunta Region, which forms part of the North Australian Craton. Copper mineralisation at the project is hosted by a lower-to-middle amphibolite grade metasedimentary sequence of the Bonya Metamorphics.
The project area lies on the south-eastern edge of the Jervois Range. The proposed mining activity is focused along the range of low hills and rises running approximately north to south through the middle of the project area, forming a J-shape.
This distinctive J-shape of the Bonya Schist outcrop has been interpreted as the result of re-folding of pre-existing folds, and as a drag feature to a regional Jervois fault that lies to the west. The more resistant lithologies feature as a series of hills that prominently define the J-structure on aerial photographs and satellite images.
The mineralisation style is generally stratabound and contained within steeply dipping lenticular bodies (lodes). The mineralised sequence has a strike length of some 12km and a stratigraphic thickness up to about 600m.
Copper-gold-silver mineralisation mostly occurs as massive to semi-massive layers of sulphides. Sulphides also occur in associated quartz veins and as thin interlayers in meta-mudstone and calcsilicates.
The major mineral deposits in the Jervois Project area – Reward, Bellbird and Rockface – are generally sub-vertical strata-bound lodes that form a distinctive, kilometre-scale, J-fold within the host rock.
The geology, mineralisation and mineral Resources are focused on the copper-gold-silver (Cu-Au-Ag) Reward, Bellbird and Rockface deposits. Lead-zinc (Pb-Zn) mineralisation such as the Reward South deposit are not developed within the document.
At all three Cu-Au-Ag deposits, the mineralization is broadly similar, although each deposit differs in its detail, especially the local geological structures.
Mineralisation is hosted by various units of the Bonya Metamorphics, mostly occurring as massive to semi-massive layers of sulphides. Sulphides also occur as associated quartz veins and as thin interlayers in meta-mudstone and calc-silicates. The mineralisation typically consists of chalcopyrite and pyrite.
Alteration zones are associated with mineralisation and magnetite forms part of the alteration assemblage and is ubiquitous in the mineralized areas of Reward and Rockface, but less so at Bellbird. Sulphide textures vary from finely disseminated to stringers and veinlets to semi-massive.
The thickness of the mineralised zones vary extensively, from less than a meter to more than twenty meters.
Two main styles of mineralisation and alteration/metamorphic mineral assemblages are recognised as:
› Lower grade, primary syn-depositional or strata bound sulphides; and
› higher grade, structurally controlled shoots, representing both remobilised strata bound syngenetic mineralisation, and a possible late tectonic intrusion-related mineralising event.
Structurally controlled shoots are the result of reworked and remobilised primary strata-bound base metal mineralisation, during and after peak metamorphism, by granite intrusions. The shoots are observed as massive or semi-massive sulphide-magnetite veins and chalcopyrite-rich brecciated veins.
Oxidation due to surface weathering effects is relatively limited, with the oxidised zone being transitional from surface to base of oxidation (approximately 10-15 m below surface). No significant zone of complete oxidation can be delineated in the mineralisation.
Dimensions
The Reward deposits strike over 1.5 km. Within the structural corridor lie five high grade shoots each approximately 200m in length and plunge steeply south up to 800 m below the surface. Two lodes lie to the east in the footwall of the reward structure.
The Rockface deposits strike over 0.4 km. Within the hook of “J” structure, there are four defined lodes which range from 100 m to 300 m in length and plunge 900 m steeply to East.
The Bellbird deposits strike over 1.3 km. Within the structural corridor lie three defined lodes ranging from approximately 200 m to 500 m in length, and plunge moderately North. Three mineralised structures lie in the hanging wall position of the main structure and two oblique lodes lie to the east of the Bellbird structure.