The Karlawinda Gold Project (KGP) is located in the Pilbara region of Western Australia, 70km by road south-east of the town of Newman (Figure 1). Karlawinda is an advanced gold project which includes the Bibra deposit and numerous outstanding exploration targets including the Francopan prospect. The project area is close to key infrastructure and mining support services. Gold mineralisation at the Francopan Prospect was originally discovered by WMC Resources Ltd in 2005. The project was subsequently acquired by Independence Group (IGO) in 2008 resulting in the discovery of the significant Bibra Gold Deposit in 2009. Capricorn acquired the project in February 2016.
At the time of acquisition of KGP from IGO by Capricorn, approximately A$12 million had been spent on regional exploration, resource evaluation and prefeasibility activities.
Since acquisition Capricorn Metals have advanced the project by drilling 147,000 metres and increased the resource by 329% from 650Koz to 2.145Moz. From the estimation of a maiden Ore Reserve in 2018 there has been a 68% increase to 1,201Moz (April 2020). Other key achievements include the granting of a mining lease, approval of all major permits and signing of major agreements.
Geology and Mineral Resources
The KGP is located in the Sylvania Inlier, on the southern margin of the Pilbara Craton. The Sylvania Inlier is a small elongated Archean (>~2.75 Ga) granite-greenstone province which consists of low- to medium-grade metavolcanics, mafic and ultramafic intrusions, and metasedimentary rocks, which have been intruded extensively by granitoid rocks. The gold project lies within the Karlawinda Greenstone Belt which spans the southern margin of the Sylvania Inlier and is part of a large-scale Archaean aged gold mineralized system.
The Bibra gold deposit is the main prospect within the KGP and currently contains a Mineral Resource Estimate of 67.2MT @ 0.8g/t for 1.7Moz Indicated, 19.5MT @ 0.7g/t for 0.4Moz Inferred (refer ASX release 17th April 2020).
The Bibra Deposit has a strike length of over 1.8km and a down dip length of 1.8km and is open along strike and down dip. The geology at Bibra comprises a sequence of alternating Archaean amphibolites and garnet schists with the majority of mineralisation hosted in silicified and magnetite altered, mylonitised sandstone (Figure 3).
Gold mineralisation is present in two parts including laterite and oxide/primary mineralisation. The laterite mineralisation lies just below the surface and consists of pisolitic lateritic duricrust composed of maghemite, goethite and hematite. The laterite zone is 1.25km long by 1.15km wide.
Oxide gold mineralisation occurs below the laterite gold mineralisation, approximately 10 metres below surface, and is hosted in kaolin and smectite rich clays and is approximately 60m deep.
The oxide/primary mineralisation gold mineralisation has developed on at least two parallel, 40m thick, shallow dipping sandstone units, which dip to the west-north-west at 22° (figure 5). The primary mineralisation has developed in two main lodes named the Main footwall and Main Hangingwall. These lodes strike NE-SW and dip west-north-west at 22°. The gold mineralisation is strata-form with lineations identified as controlling higher-grade shoots. The lodes are typically wide intercepts (e.g. 40m @ 0.9 g/t Au) but high-grade shoots have developed parallel to the metamorphic fabric plunging to the west-north-west in a rod-like geometry. Down-plunge the grades and thicknesses remain consistent whilst along strike they are more variable. The primary mineralisation in fresh rock is marked by 3-10% sulphides, subhedral magnetite grains, quartz veins/veinlets, and fine-grained gold.
Outside of the main mineralization, more discrete lodes occur. In the hanging wall to the main mineralisation, Port Rush, Easky, Finns and Easky East ore domains occur and to the south of Bibra, Mineralisation continues south from the main pit area into the Southern Corridor and Tramore lodes.
Regional Exploration Potential
The KGP is 110 km wide by 30 km long and consists of 2,042km2 exploration and mining tenure in the highly prospective geology of the Sylvania inlier.
To date the focus of exploration by CMM has been on increasing the resource at Bibra. This has been successful in increasing the resource by 1.5 Moz to 2.145 Moz since CMM first acquired the KGP. The only drilled prospect outside the Bibra area is Francopan, which is a discovery made by WMC in 2004. Francopan is located 5km to the south-east of Bibra and has similar geology, geometry and grade as Bibra. The detailed work completed at Bibra and Francopan has allowed the identification of key geological features responsible for the gold deposit formation. These key features are being applied through the Karlawinda project tenure to identify areas where new Bibra style gold prospects may occur.
Exploration in the broader area remains at an early stage. Almost no significant, modern gold exploration has been completed on the large Archean greenstone holding outside Bibra. Previous work completed consists of mainly wide spaced aircore holes within 5km of Bibra. Outside this area exploration consists of wide spaced geochemical sampling and airborne geophysics. Near mine and greenfields exploration will increase over the course of 2020 with the aim of discovering more ore feed for the Bibra processing plant.
Bibra Ore Reserve
In April 2020 a recalculated Ore Reserve (refer ASX release 17th April 2020) was estimated for the Bibra Deposit comprising:
43.5 million tonnes @ 0.9g/t Au for 1,201 Moz of gold
- This is a 35% increase from the previously announced Ore Reserve of 892,000oz.
- The Ore Reserve final pit design is a 12-year mine life involving pit staging, with life-of- mine (LOM) stripping ratio of 3.6:1.
- Revised process plant design incorporates tertiary crushing, single Ball Mill comminution circuit followed by a conventional gravity and carbon in leach (CIL) process to treat the ore.
- The Ore Reserve has been estimated using a gold price assumption of A$1600/ounce and a variable cut-off grade of between 0.3g/t and 0.4g/t Au (dependent on ore type).
- Power will be generated on site utilising natural gas via a 56km pipeline connecting to the Goldfields Gas Pipeline (GGP).
The Ore Reserve estimate has been completed on the basis of Modifying Factors used in the Company’s November 2017 Feasibility Study (FS) and updated by subsequent studies including further optimisation and trade-off studies on the process plant and non-plant infrastructure. These studies were completed by a team consisting of Capricorn personnel and independent external consultants.