Terramin’s South Gawler Project (SGP) is located along the southern margin of the Gawler Ranges, northern Eyre Peninsula, South Australia. The project comprises a group of 10 Exploration Licences totalling 3887 km2 and one Exploration Licence Application (ELA 2017/122, subsequent licence, Figure 1) covering 493 km2, all held by Menninnie Metals Pty Ltd (MMPL), a wholly-owned subsidiary of Terramin (Figure 1).
From 21/06/2017 the project is being explored under an earn-in joint venture agreement with Evolution Mining Limited (Evolution) whereby:
- Evolution can earn 70% equity in the project for A$4 million exploration spend over four years
- Terramin may then elect to contribute, otherwise Evolution can earn an additional 10% (total 80%) by spending a further A$2 million over two years, after which a pro-rata period will operate
- Evolution can withdraw from the project after a minimum spend of A$500,000 within the first year
The SGP covers extensive exposures of the Gawler Range Volcanics (GRV) formed by large-scale eruptions of felsic magmas associated with the widespread emplacement of high-level granitic intrusions and associated mineralising systems (Figure 2) approximately 1.59 billion years ago. The GRV and underlying metamorphic rocks are prospective for a range of mineral deposit styles that include various combinations of gold, silver, copper, molybdenum, lead, zinc, rare earth elements, graphite and tin ± tungsten. The prospectivity is evidenced by numerous mineral occurrences in the region, and the presence of several significant deposits (Figure 2). The latter include the 42Moz Paris silver deposit located just 6km to the south of EL 5430 and the 7.7Mt Menninnie Dam lead-zinc-silver deposit located on the SGP’s EL 5949 (Figures 1, 2).
The Menninnie Dam deposit – the largest undeveloped lead-zinc deposit in South Australia – consists of two main mineralised zones: the Menninnie Central zone, and the nearby Viper zone. The lodes at Menninnie Central and Viper have been combined to estimate a JORC 2004 compliant Inferred Resource totalling: 7.7Mt @ 3.1% Zn, 2.6% Pb and 27g/t Ag, at a 2.5% Pb+Zn cut-off (ASX: TZN 1st March 2011).
The SGP is flanked by several significant gold prospects that are yet to be fully evaluated. These include Barnes-Baggy Green, Weednanna, and Parkinson Dam along the southern margin of the GRV (Figure 2) and the Nankivel prospect, located 2km east of the Paris deposit, where recent drilling is showing evidence for the presence of a large porphyry copper-gold system. The Glenloth and Tarcoola goldfields and the Tunkillia gold deposit flank the GRV to the northwest.
Two broad groupings of GRV are recognised: an upper (younger) group consisting of extensive comparatively flat-lying flow units of porphyritic dacite and rhyolite, and a lower (older) group that is more compositionally and texturally varied (rhyolitic to basaltic lavas and tuffs) and locally more steeply tilted. The lower GRV and underlying metamorphic basement rocks host most of the mineral deposits and occurrences mentioned above, contributing to a general perception that mineralising fluids have been unable to penetrate the upper GRV. This perception is false.
The southern Gawler Ranges region in the Gawler Craton of South Australia is increasingly becoming recognised as an under-explored province with high discovery potential. The SGP covers much of the highly prospective ground between the two principal locations where the Mineral Systems Drilling Program (MSDP) was recently carried out (August 2015 to April 2016). The MSDP was a major world-first collaboration of mineral explorers, drillers, government agencies and research institutes. The Government of South Australia contributed $2.5m and this investment was leveraged overall into an $8m program through partner contributions and in-kind support. The MSDP, which included field mapping programs, recorded new occurrences of:
- epithermal veining and alteration in the upper GRV,
- skarn-related Pb-Zn±Ag mineralisation,
- altered GRV volcaniclastic rocks locally hosting Pb-Zn±Ag mineralisation,
- volcaniclastic rocks within the GRV – locally altered and hosting anomalous Pb-Zn±Ag,
- greisen associated with Hiltaba granites.
All these occurrences are close to the western margin of the SGP and they show some similarities to hydrothermal vein/breccia systems and volcaniclastic rocks (likely fluid/metal “sponges”) identified within the SGP area. The MSDP has contributed to the rapid growth of evidence showing that hydrothermal systems related to Hiltaba-GRV magmatism are widespread within and adjacent to the GRV, which is consistent with the JV’s exploration model for discovery of IOCG deposits in its project area.