In the Hermes and Bryah JV Projects there are two broad mineralisation styles (Outhwaite, 2013) referred to here as the Peak Hill Type and the Bryah Type.

The Peak Hill Type gold deposits are hosted in rocks that are generally highly deformed (four or more fold events) and metamorphosed (up to amphibolite facies), generally represented by the Peak Hill Schist Formation. Mineralisation is early in the paragenesis, (syn- to post-D1 isoclinal folding) with folded mineralisation commonly observed. Previously mined examples include Peak Hill Main/Five-Ways, Mt Pleasant, Jubilee, Wilgeena and St Crispin. The Hermes deposits may be examples of unmined mineralisation that belongs in this category.

The local controls on this deposit class are difficult to identify, because of the effects of strong, post - mineralisation deformation, and probable remobilisation of Au. Despite this problem, some similarities between the deposits have been recognised:

• Located on a major structural and metamorphic gradient. The Peak Hill camp, Hermes, Wilgeena and Central Bore all lie around a significant gradient from high-strain, highly metamorphosed rocks at the core of uplifted basement blocks, outwards to lower-strain, less metamorphosed rocks. This gradient is a transitional structural zone up to a few kilometres wide. This zone was probably a major fluid conduit during early deformation, and hence a first-order corridor for Au exploration;
• Located at or around mafic-sedimentary contacts. With the exception of Central Bore, which is on a granite-sedimentary contact, all of the mentioned Peak Hill-style occurrences are closely associated with mafic rocks within dominantly sedimentary sequences. The mafic rocks are typically amphibolite, after dolerite or basalt, but high-Mg to ultramafic rocks are noted at Hermes, Wilgeena, and possibly the Peak Hill camp (high Cr and Mg);
• Early structures. A likely early age on the controlling structural corridor has been recognised, based on the repetition of stratigraphy, which was then folded together during the identifiable fold events. The identification of early, controlling structures has proven difficult, due to the overprint of subsequent deformation events;
• Strong plunge controls. Due to the multiple folding events these deposits have strong plunge controls, meaning they can have small surface footprints – especially when considering their general lack of pathfinder anomalism (see below). Exploration must take this fact into account;
• Limited geochemical signature. Wilgeena, Central Bore, St Crispin, Pelorus and possibly Peak Hill have a limited range of pathfinder elements associated with the Au mineralisation – scattered W, Bi, Pb and Zn, but very little else. Hermes is a clear exception however, as limited multi-element analysis has shown that this system has a strongly developed pathfinder association, similar to that found in typical Archean Au systems: As, Sb, Mo, W, Bi, etc.

Hermes
At Hermes the Hawkeye, Trapper, Klinger, Winchester & Blake deposits are sub -parallel, northeast trending, mineralised zones. Mineralisation at all deposits is typically associated with quartz veins at or near the sheared contact of mafic amphibolite footwall and hangingwall quartz- biotite-sericite schists. Graphitic schist occurs to a minor extent on the hangingwall and footwall sides of the mineralisation at Trapper, Klinger and Blake. The base of strong oxidation varies from 20m to 30m vertically below surface at Hawkeye & Winchester, and from 25m to 45m at Trapper, Klinger & Blake. Transition to fresh rock occurs at approximately 30m to 50m and 40m to 65m, respectively.

In general, the mineralised quartz veins, foliation and relict bedding are steeply NW-dipping to sub-vertical in both the Hawkeye and Trapper deposits and high-grade shoots are interpreted to plunge shallowly to the north within the mineralised plane.

Hermes South
Gold mineralisation occurs within a predominantly metasedimentary sequence of the Proterozoic Peak Hill Schist and mafic units. The Peak Hill Schist comprises quartz-sericite schist and quartz-muscovite schist and is located on the south-western extreme of the Marymia Inlier.

Mineralisation at Hermes South is associated with the development of strong linear fabrics and quartz veining dipping at 65 degrees to the south in fairly predictable and consistent zones.

Open Pit Mining at Billabong is at Hermes Complex, which is about 65 kilometres from Plutonic. The Hermes Complex consists of two project areas –

• Hermes Project – It has following four open pit cutbacks –
o Trapper
o Klinger
o Hawkeye
o Winchester.

• Hermes South Project – It has following one open pit –
o Wilgeena.

The Hermes Project commenced being mined in December-2017 and paused in May-2019, as below –
• Trapper Pit started in December-2017 & paused in April-2019. Trapper was mined in four stages
• Hawkeye Pit started in December-2017 & paused in January-2019
• Klinger Pit started in April-2018 & paused in December-2018
• Winchester Pit ran for a month in May-2019, contour mining near surface deposit only.

The Hermes South Project is about 20 kilometres south of Hermes Project. Historically, prior to Billabong takeover, contour mining very near to surface is done in Wilgeena Pit.

All four pits in the Hermes Project area are mined as a conventional open pit excavator-truck mining operation. A mining contractor was engaged for drilling, blasting, loading, hauling, and dumping, as well as civil services for general site maintenance works. The material mined from each pit is being stockpiled adjacent to each pit exit before being loaded onto road trains for transport along the haul road to Plutonic for processing through the existing mineral processing configuration.

The Hermes South Project is about 20 kilometres south of Hermes Project. Historically, prior to Billabong takeover, contour mining very near to surface is done in Wilgeena Pit.

All four pits in the Hermes Project area are mined as a conventional open pit excavator-truck mining operation. A mining contractor was engaged for drilling, blasting, loading, hauling, and dumping, as well as civil services for general site maintenance works. The material mined from each pit is being stockpiled adjacent to each pit exit before being loaded onto road trains for transport along the haul road to Plutonic for processing through the existing mineral processing configuration.

Areas disturbed by mining activities have been stripped of vegetation, topsoil, subsoil, and potentially hardpan duricrust material and stockpiled within designated storage areas for later use in rehabilitation. Laterite waste rock is being used to construct haul roads, erect windrows and sheet ore pads, with surplus material stockpiled in an accessible location for use in haul road maintenance. All other waste rock is being hauled directly to the waste dump, and sequenced so that any potential acid forming or hazardous material is encapsulated within the dump.

Some near surface weathered material is free-dig, but 100% of transitional material and fresh rock is blasted. Blast-hole drilling is undertaken using surface top hammer drill-rigs on 5 m benches using hole sizes up to 115 mm diameter. Drill burden, spacing and sub-drill design is a function of material types and powder factor. Drill and blast of 10 m benches in the upper waste sections of each pit is reviewed. Explosive selection depends on the presence of groundwater and the success of dewatering. The water table at Hermes is estimated at a nominal 29 m below the pit crest. For pit optimisation, ammonium nitrate fuel oil (ANFO) is assumed in the oxide material and emulsion for the remainder of the deposit.

CAT 777F Haul trucks with a load capacity of 90 t is used in conjunction with 120 t class hydraulic excavators in a backhoe configuration to achieve the required waste extraction ratio and selectively mine the ore. In general, 5 m benches are mined on two 2.5 to 3.5 m fitches (allowing for heave after blasting). In harder material, where extensive heaving of blasts occurs, the heave is mined separately down to bench level, followed by two 2.5 m fitches to minimise ore dilution. Ancillary services to support the production fleet include graders and water trucks for haul road maintenance and dozers for maintenance of pit benches, preparation of blasted benches, along with waste dump management.

The mining operation excavate and load ore and waste in accordance with marked ore and waste boundaries to ensure minimum dilution and maximum recovery of ore, with a geologist present during all ore mining. Standard practice to minimise dilution include mining along the strike of ore blocks, mining from hanging wall to footwall contacts, and grader or dozer clean-ups restricted to along strike in the ore zones. Ore and waste boundaries delineated based on grade control sampling results and bench and face mapping. Blocks are marked out by flagging tape and paint for excavation. Blast monitors are installed prior to blasting and surveyed post blast to determine ore movement. Blast design software (such as Shotplus) is used for all blast tie-ins ensuring ore shots are fired in a direction along strike. Ore is stockpiled according to grade and rock type on stockpiles within the Hermes Complex area. Highway-style side-tipping road trains with a nominal payload of 220 t are loaded with ore from stockpiles at Hermes for transportation to the Plutonic ROM pad and stockpiled separately by material type and grade via the Billabong’s owned 64 km haul road. The front-end-loader (FEL) on the Plutonic ROM pad maintains stockpiles. A rock breaker is maintained at both Hermes Complex stockpiles and at the Plutonic ROM pad to break stockpiled oversize ore.

A dedicated fleet of a grader, watercart, and roller maintain the haul road to the Plutonic ROM pad. Low-grade material may be stockpiled for possible processing later in the mine life.

The primary sections of the processing plant that are currently in use are:
• Crushing and conveying
• Ore reclaim and grinding
• Leaching and carbon adsorption
• Carbon stripping, electrowinning, refining and carbon regeneration
• Tailings thickening
• Tailings deposition and storage
• Reagent mixing and handling
• Plant services.