Coal of Maules Creek associated with the early Permian age Maules Creek Formation of the Maules Creek Sub-basin.

The basement of the Maules Creek Sub-basin is formed by the Boggabri Volcanics. The rhyolitic volcanics are overlain by the Leard Formation, a thin unit comprised of black claystone and rare, thin coal seams. The Maules Creek Formation is up to 800 m thick within Aston’s mining authorities and sits conformably on the Leard Formation.

Within CL 375, the Maules Creek Formation contains 15 named coal seam groups, which exhibit splitting towards the north-east. This seam splitting has resulted in the recognition of up to 39 individual seam plies resulting in complex geological modelling. The identified coal measures generally dip towards the south- east with a flattening of dip occurring in the far south-eastern corner of CL 375 (coal lease).

Dips range from 1 to 7 degrees but are within the range of comfortable open cut mining operations. Dip direction is generally consistent across the deposit.

Coal will be extracted from all 15 defined seams, via open cut methods down to the Templemore seam. All seam groups situated stratigraphically below the Braymont Seam lap onto the basement volcanics. The depth of weathering across the modelled area varies from 6 m to 113 m with the average depth of around 25 m.

Maules Creek Coal Mine (MCCM) is an open cut coal mine with an approved maximum ROM coal production rate of 13 Mtpa to December 2034. Pre-mining clearance activities including ecological, archaeological and soil analysis were undertaken in line with the relevant approvals and management plans.

Topsoil was reclaimed from the area to be mined and stockpiled for later use on rehabilitation areas. Overburden is blasted prior to being removed by loader and / or excavator and trucks before proceeding with coal extraction.

During the second half of the FY20, Maules Creek reached pit bottom in the first of three planned locations. Access to pit bottom has created in-pit dump space that has delivered shorter overburden haulage distances and elevations than have been experienced in the last two years. In-pit dumping is expected to increase to 100% of overburden material in FY23.

Autonomous haulage (AHS) of overburden has commenced. The second AHS fleet is scheduled to be commissioned in Q3 FY21 with the remaining three fleets scheduled to commence at six month intervals over the following 18 months.

The CHPP utilises an industry standard Dense Medium Cyclone (DMC)/Reflux Classifier process to remove a proportion of rock impurities from the coal and ensure product specifications are maintained. The Maules Creek CHPP has a nameplate capacity of 1800 tph and consists of a dense medium cyclones (+1.7 mm square mesh equivalent), spirals (-1.7 mm – 0.125 mm) and a conventional thickener and belt press filter.

The operation produces three products as follows:
- SSCC - fluidity > 50 dd/min, CSN > 3, Ash < 8% (ad);
- PCI - CV > 6478 kcal/kg NAR, Ash < 8% (ad);
- Thermal

COAL HANDLING AND PROCESSING
Product coal generated by the MCCM includes bypass coal (i.e. ROM coal that is crushed and screened but not washed in the CHPP) and washed coal that is processed in the CHPP. The product coal is stockpiled and then reclaimed and fed via conveyors to the Train Loading Facility. Once loaded, trains travel from the MCCM via the Maules Creek Rail Spur, Sha ........