Geology
The Jervois project is centered on a 12-kilometre-long mineralised strike following the distinctive shape of a JFold. This structure hosts significant ore reserves, distributed across multiple orebodies, with copper showings identified both at the surface and through drilling. The continuous mineralisation along the fold highlights extensive resource potential for both open pit and underground mining. Advanced geophysical techniques, including Induced Polarisation (IP) and Downhole Electromagnetic (DHEM) surveys, have been instrumental in the exploration of the J Fold, providing critical insights into the subsurface geology and guiding drilling campaigns.
Figure 1. The distinctive shape of a J Fold hosting the three major deposits Reward, Bellbird, and Rockface as well as numerous prospects along the entire J-fold series of hills.
Three major orebodies—Reward, Bellbird, and Rockface—form the cornerstone of the Jervois project. Reward, located on the eastern limb of the J Fold, is planned to be developed using a combination of an open pit and two underground mining operations. Bellbird, situated on the western limb, will also be exploited through both open pit and underground methods. These deposits are well-defined and strategically positioned, offering favourable conditions for resource extraction.
Rockface, located near the hinge of the J Fold to the south, is renowned for its exceptionally high copper grades. This orebody will be developed as an underground mine and plays a central role in the economic viability of the project. The Rockface deposit was discovered by drilling an IP anomaly, demonstrating the effectiveness of geophysics in identifying high-value targets. DHEM surveys continue to be used to guide drilling at Rockface and other deposits, leading to the discovery of extensions for the three main orebodies and additional brownfields targets along the J- fold.
The success of geophysical methods, combined with extensive drilling, has not only defined the key orebodies but also revealed the broader potential of the J-Fold. Copper showings are present throughout the structure, indicating opportunities for further exploration and resource expansion. Together, Reward, Bellbird, and Rockface, supported by ongoing discoveries and advancements in exploration, establish the Jervois project as a significant contributor to the region’s mining potential.
KGL is working with leading consultants to evaluate development scenarios at Jervois in order to maximise development economics while minimising environmental impact.
KGL is also working closely with all stakeholders including the Northern Territory Government and local communities on the Jervois development.
Figure 2. Diamond Drilling at Rockface
The Company has sought to employ financial resources in the most efficient way, engaging in cost effective exploration while minimising corporate costs.
KGL also acquired in 2015 two exploration licences at Yambah, 60km north and northeast of Alice Springs, because of the similarity of the style and age of the mineralisation to Jervois which is 150km to the east. Limited work has been done under KGL ownership on these tenements, however the geology indicates excellent exploration potential that would be accretive to the Jervois development story.
Mineralisation
The Jervois Project is located on four Mineral Licences (ML 30180, ML 30182 and ML 30829) located within EL 25429 held by Jinka Minerals, a subsidiary of KGL Resources. ML32277 held by Jinka Minerals contains the Projects groundwater borefield, some 20km to the north of the mine area.
Base metal mineralisation at Jervois is hosted within a lower- to middle-amphibolite grade metasedimentary sequence known as the Bonya Metamorphics. This unit, part of the Aileron Province in the Palaeoproterozoic eastern Arunta Region, experienced peak metamorphism during the high-temperature, low-pressure Strangways Event.
The main mineralisation at Jervois is occurring within steeply dipping, lenticular lodes composed of calc-silicate, garnet-chlorite-magnetite rock, and garnet-magnetite quartzite. These lodes are set within a broader succession of spotted andalusite-cordierite schist and quartz-sericite-magnetite schist.
Mineralization at Jervois characterised as a hybrid SEDEX‐VHMS deposit by Schmid & Schaubs (CSIRO) in 2015. The characterisation of mineralisation style was interpreted as:
- Cu‐Pb‐Zn mineralisation that is stratiform and extends over several kilometres along strike with repeating stratigraphy due to isoclinal folding.
- Mineralisation occurred syngenetically and possibly epigenetically during a hydrothermal exhalative event, prior to metamorphism and deformation.
- The sedimentary host rock and mineral zonation suggest a SEDEX deposit, however the high-grade copper suggests VHMS deposits.
Figure 3. Magnetite and chlorite altered section of Psammopelite comprising a discordant breccia, the breccia comprises a dense open to closed framework of magnetite altered psammopelite enclaves locally with some containing secondary biotite and pyrite.
Figure 4. A high-strained mineralisation section from Rockface north lodes. The mineralisation comprises chalcopyrite which mantles and includes and earlier pyrite phase. The sulphide mineralisation is localised along discrete domains of boudinage psammitic bands. Associated with the sulphide mineralisation is a secondary coarse-grained biotite phase. The scale bar in the corner is 5cm.
The mineralised sequence spans a strike length of approximately 12 kilometres and reaches a stratigraphic thickness of up to 600 metres. This extensive and well-defined geological setting underpins the resource potential and development of the Jervois project.
Figure 5. Reverse Circulation (RC) Drilling at Bellbird South looking west towards the prominent prospective ridge.
Resource
Mining Associates was commissioned by KGL Resources to complete updated Mineral Resource estimates for the Reward, Bellbird, and Rockface deposits, which form the majority of the delineated resource at the Jervois Copper Project. The target commodity is copper, with subordinate silver, gold, lead, and zinc. Incorporating results from KGL’s 2024 exploration program, the most recent resource estimate was announced on 25th November 2024.
Since acquiring Jervois in 2011, the copper Mineral Resources at the project have been significantly upgraded. The 2024 exploration program further added 4.1 Mt to the underground resource, increasing the contained copper to over 500,000 tonnes. This update has been used to revise the mine plan and deliver an updated feasibility study.
Confidence in the resource estimates has been significantly enhanced, with over 60% of the total copper Mineral Resources now classified in the Measured or Indicated categories. The total copper resource estimates are as follows:
- 27.45 Million tonnes at 1.87% Copper, 0.24g/t Gold and 25.3g/t Silver,
- containing 513.4kt copper and 22.37 million ounces silver, and 214,500 ounces of gold
Advances in the resource base when compared with the previously reported estimate, are due to the confirmatory infill drilling undertaken since 2022, coupled with improved understanding of the geological controls on mineralisation. This was achieved through the systematic incorporation of drill results in the geological models and adapting the drill plans accordingly.
Resources update in detail
The progress in upgrading of the mineral Resource at the Jervois Copper Project is shown below.
The latest Resource Estimates for the Reward, Rockface and Bellbird deposits are detailed below in Table 1.
Table 1- Jervois Copper Project Current Resources (Released to the ASX on 29/11/2024)
Improved Geological Model
During the last 5 years, the KGL geology team has greatly improved the understanding of the controls of mineralisation and disposition of the mineralised lodes. As outlined in the August 2019 JORC report, improved field protocols, supplementing legacy core-logging codes, were introduced in 2017 for lithology, alteration, mineralisation, and structures.
The result has greatly enhanced geological understanding and consistency in logging of lithology, alteration, mineralisation, and structural domains and subgroups. KGL now recognises two main styles of mineralisation and alteration/metamorphic mineral assemblages:
- Lower tenor, primary syn-depositional or stratabound disseminated sulphides, and
- Higher grade, structurally controlled shoots representing both remobilised stratabound syngenetic mineralisation, possibly related to a late regional intrusion-related mineralising event.
Higher grade mineralised shoots are the result of reworked and remobilised primary strata-bound base metals during deformation. During late-stage deformation, regional-scale granite intrusions likely provided the heat and fluids that remobilised copper from primary (stratabound) units into structural traps such as anticlinal fold hinges. The structural framework for this is supported by research from the Northern Territory Geological Survey (e.g., McGloin et al. 2019 and Weisheit et al. 2019). The shoots are observed as massive or semi-massive sulphide-magnetite veins and chalcopyrite-rich brecciated veins.
At Rockface, on the western side, high-grade shoots of bornite copper mineralisation have been discovered. Textural evidence indicates that this is a very late-stage hydrothermal replacement of earlier chalcopyrite mineralisation. This discovery underscores the complexity of the mineralising processes at Jervois and highlights the significance of integrating detailed geological, structural, and textural analyses into exploration and development strategies.
Figure 6. A section of core from Rockface (KJCD481D3), featuring massive relict chalcopyrite enclaves mantled by secondary biotite. Encompassed within the sulphide section are large clast of psammopelite and magnetite. A late coarse grained muscovite phase defines a foliation through the sulphide section. Crystallization of the psammopelite clasts has also produced coarse grained secondary muscovite within the magnetite alteration zones. This may suggest the secondary muscovite recrystalised during the subsequent chalcopyrite event and prior to the late bornite replacement. The foliation is discordant to the S1-S2 composite layering and possibly reflects the S3 foliation. The relative timing relationship constraining the mineralisation to a syn D3 deformation. The scale bar on the left side corner is 5cm.
The improved geological model, upon which this resource update is based, widens opportunities to target higher grade extensions and repetitions within favourable host rocks and structures in other areas adjacent to known deposits and in other prospects at Jervois and the surrounding Unca Creek tenement.