Summary:
Dominant host rock of the Kora Consolidated-Irumafimpa vein systems is the highly sheared and deformed Bena Bena formation, composed of low grade metamorphosed phyllites and amphibolites, intruded by the Elandora porphyry at the northwest end of the vein system. Mineralisation on the property includes gold, silver, and copper in low sulphidation epithermal Au-telluride veins (Irumafimpa), Au-Cu-Ag quartz-sulphide veins of Intrusion Related Gold Copper (‘IRGC’) affinity at Kora Consolidated, indications of porphyry Cu Au systems (Blue Lake) and alluvial gold.
The Kora Consolidated-Irumafimpa mineral zone occurs in the centre of a large mineralised system, approximately 5 km x 5 km in area, that has been subject to drilling in parts and comprises several individual zones of vein and porphyry-style mineralisation. The Kora Consolidated-Irumafimpa (including Kora, Eutompi and Kora North) vein deposits have been demonstrated from drilling results and underground development to be a continuous mineralised structural system.
The Kora Consolidated mineral zone comprises a K1 footwall lode and a K2 hanging wall lode separated by varying widths of 0 to 15 m. In parts there is interstitial mineralisation between K1 and K2 known as the Kora Link lode and about 90 to 150 m to the east lies the parallel Judd lode. The Judd lode (J1) as well as J2 to J4 mineralised zones appear to be a vein system similar to the Kora Consolidated zone, but as yet has not been fully defined by drilling.
Kora Consolidated vein system is a broad northwest trending mineralised zone more than 2.5 km long and up to 60 m wide in which individual veins vary from less than one metre wide with pinch and swell features over short distances (Au telluride lodes at Irumafimpa) to more continuous veins up to several metres wide (Au, Cu – rich quartz and sulphide lodes, IRGC).
Kora Consolidated-Irumafimpa Vein Systems
The Kora Consolidated-Irumafimpa vein systems is interpreted to contain two stages of mineralisation. The earliest is a sulphide-rich Cu-dominant stage. This is overprinted by a quartz-rich, Au-dominant crustiform quartz vein to breccia system with high grade gold associated with tellurides (e.g. Calaverite AuTe), reaching a vein intrusive style of mineralisation at Kora Consolidated containing Au and Cu mineralisation with minimal tellurides.
Stage 1 is the earliest period of alteration and is characterised by silicification and fuchsite alteration of phyllitic wall rock.
Stage 2 mineralisation comprises coarse-grained idiomorphic quartz and pyrite (typically euhedral) veins with base metals. Volumetrically this early mineralisation appears to be the most abundant mineralisation. At Kora Consolidated the mineralisation comprises massive pyrite veins to pyritic breccias, grading to pyrite-chalcopyrite-bornite veins characterised by elevated Zn, Pb, Sn, W, Bi, and Sb in an intrusive vein style mineralisation. Higher copper grades, in the order of 2% Cu, occur at Kora (Coote, 2018; Muller et al., 2019). There appears to be a lateral zonation to lower copper grades at Irumafimpa.
Stage 3 mineralisation is the dominant gold-bearing stage and is characterised by crustiform, vuggy and colloform quartz veins, quartz breccias, and xenomorphic pyrite. At Irumafimpa most of the gold occurs as the gold tellurides calaverite and kostivite, which are concentrated at vein margins. Significant native gold has been locally observed and is probably a result of either oxidation of tellurides at Irumafimpa, or as primary native gold at Kora Consolidated. Kora Consolidated is characterised as a vein intrusive style mineralisation containing minimal tellurides.
Stage 4 is manifested as local brecciation and deposition of low temperature quartz along with minor copper mineralisation.
Dominant host rock of the Kora Consolidated-Irumafimpa vein systems is the highly sheared and deformed Bena Bena Formation, composed of low grade metamorphosed phyllites and amphibolites, intruded by the Elandora porphyry at the northern end of the vein system.
The current mineralisation is part of a broad northwest trending mineralised zone more than 2.5 km long and up to 60 m wide in which individual veins vary from less than one metre wide with pinch and swell features over short distances (Au telluride lodes at Irumafimpa) to more continuous veins up to several metres wide (Au, Cu – rich quartz and sulphide lodes) and 100’s of metres of geological continuity at Kora.
The Kora Consolidated comprises two parallel, steeply west dipping, north-south striking quartzsulphide vein systems, K1 and K2, within an encompassing dilatant structural zone hosted by phyllite. An additional structure, the Kora Link, has also been defined for part of the area between K1 and K2. The current Kora Consolidated resource estimate area covers an area of approximately 1,250 metres along strike by 1,050 to 1,150 m vertically. Kora Consolidated is along strike to south from the previously mined Irumafimpa deposit.
Judd Vein System
The Judd lode is a narrow, (4.9 m average width in the MRE 2022) intrusive related quartz-sulphide, Au-Cu-Ag vein system, similar to Kora Consolidated located approximately 90 to 150 m east of and parallel to Kora Consolidated on ML150. The system consists of four known narrow veins with significant inter-vein separation, steeply dipping and with a similar strike direction as Kora. The vein of most interest is the western vein, J1 and at the close of date of the MRE 2022, this has been subject to development drives on two levels (1,235 and 1,265 level) totalling 692 m and 197 face sample lines for 1,478 samples. This work indicated significant geological continuity with variable grade continuity, significant mineralisation with potential for economic extraction, material from the development drives was treated by the process plant and achieved similar recoveries for gold and copper to that achieved with Kora material. K92ML has carried out diamond drilling from both underground and surface to define part of the Judd J1 vein system in the development area. Underground diamond drilling has concentrated on the J1 vein, with some holes being extended to intersect the other veins (J2, J3, and J4) previously documented by Barrick and HPL and which remain under-explored.
The Judd vein system was partially tested by Barrick surface holes that were drilled to test the Kora Consolidated lodes at depth. This sporadic drill testing returned a maximum intersection of 3 m @ 278 g/t Au. Core samples illustrate two types of Judd vein mineralisation, a quartz dominant, Au-rich component, and a sulphide dominant, Cu-rich vein style. Surface mapping and sampling has indicated a mineralised strike length of over 2.5 km.
Dominant host rock of the Judd vein system is the highly sheared and deformed Bena Bena Formation, composed of low grade metamorphosed phyllites and amphibolites, intruded sometimes by thin intermediate intrusives of dacitic composition in sub-concordant positions.
The dimensions of the wireframe interpretation used in MRE are 800 m in strike length and 500 m to 700 m in the dip direction. The Judd vein system is interpreted where it has been sporadically intercepted in diamond drill holes from surface and underground in the ML150 and passing into EL470 to the south for a total distance of 2.5 km. This shows potential that is yet to be developed. The J1 gold grade continuity and mineralisation pinches and swells along the drive. The gold grades vary with ranges of similar grades typically between 5 up to 30 m along the drive, the variability is usual for this type of mineralisation.