Abra is a world class base metals deposit with a globally significant resource of lead-silver which transitions into gold- copper rich mineralisation at depth.

The Abra deposit lies within sediments of the Proterozoic Edmund Group. Abra is a base metal replacement-style deposit hosted by sediments. The primary economic metal is lead. Silver, copper, zinc and gold are also present but are of much lower tenor.

The deposit can be divided into two main parts. The upper “Apron” zone comprises strataform massive and disseminated lead- sulphides (galena) and minor copper sulphides (chalcopyrite) within a highly altered sequence of clastic and dolomitic sediments. Alteration products include jasperlitic rich sediments (the “Red Zone”) and a distinctive stratiform zone of hematatite-magnetite alteration (the “Black Zone”. The Apron zone extends for 1,000m along strike, 700m down dip and dips gently south.

The “Core” zone underlies the Apron and comprises an elongate funnel shaped body of hydrothermal breccias, veining and intense alteration overprinting gently south dipping sediments. The veining and breccia zones in the Core typically dip steeply to the north. High grade lead sulphide mineralisation is predominantly hosted in intensely veined zones. High grade zinc sulphide mineralisation (sphalerite) is found in the central parts of the Core. Copper (chalcopyrite) and gold mineralisation is sporadically found throughout the upper parts of the Cor ........

Underground mining using long-hole open stoping has been selected as the primary mining method, with paste backfill. However, certain shallow dipping areas within the Apron Zone will be mined as room and pillar. Ground conditions are expected to allow relatively large stopes to be employed.

Using available geotechnical data, an overbreak of less than 0.5 metres was estimated and a dilution of such was applied to all hangingwall stopes. The grade of dilution hangingwall material for stope shapes was also estimated (Apron Zone hangingwall dilution grade 4.8% lead and Core Zone hangingwall dilution grade 4.2% lead). This confirmed the mining grade factors considering the reasonable grade of dilution material. Pillars were not designed but an allowance for Ore loss in pillars was included in the stope recovery factor. Consequently, a range of stope recoveries were applied for different mining methods. These range from 75% in the room and pillar areas, up to 95% for long-hole open stoping areas, where no pillars are planned. Based on this, the Ore Reserve estimate assumes an average overall stope recovery of 85%. Given the relatively high grade of dilution hangingwall material, an overall mining dilution factor of 5% was applied. Minimum mining width was assumed to be 5 metres.

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