Overview

Deposit type

• Sedimentary

Summary:

The Carborough Downs project is located on the north-western flank of the Bowen Basin, a sedimentary basin comprising Permian to Triassic age geology. In the vicinity of the project site, the Bowen Basin geology has been folded, forming a broad syncline that plunges and opens to the north. The project site is located on the western limb of the syncline.

Subsequent magmatism has resulted in the formation of localised intrusions of igneous rock within the Bowen Basin sediments. The Bowen Basin sediments are typically overlain by more recent Triassic and Cainozoic age deposits. These deposits (and the upper profile of the Bowen Basin sediments) have been extensively modified by long periods of weathering.

The stratigraphy of the project site and its surrounds includes the following (in descending order):
• Localised alluvium associated with North Creek (not present within the project site);
• Cainozoic sediments, including the Suttor Formation, associated colluvium, weathered sediments, and residual soils;
• Triassic sediments of the Rewan Group;
• Permian coal measures, comprising the Rangal Coal Measures (including the target Leichhardt seam) and the underlying Fort Cooper Coal Measures; and
• A localised Cretaceous granitoid intrusion.

Alluvium is not present within the project site. The distribution of alluvium is limited to localised deposits associated with North Creek and its floodplain. The floodplain alluvium thickness is variable, and ranges from a few centimetres at the edge of the floodplain to approximately 3 m thick on the banks of North Creek. The creek channel is incised into the floodplain alluvium and there is typically a thin covering of bed sands present in the creek bed. Alluvium is not present outside this localised area.

The Cainozoic sediments are a weathered profile of sandstone, mudstone, other sediments and residual soils. The Cainozoic sediments are characteristically fine-grained, clay-bound and poorly consolidated. The Cainozoic sediments are widely distributed over the project site and its surrounds. The Cainozoic sediments underlie the alluvium (where present). Elsewhere, the Cainozoic sediments are typically located at the ground surface. The Cainozoic sediments are between 5 m and 18 m thick within the project site. The Cainozoic sediments are up to approximately 30 m thick in the vicinity of North Creek east of the project site and in the elevated areas to the north-west of the project site.

The Rewan Group is a fine to medium grained sandstone, siltstone and shale. The Rewan Group subcrops below the alluvium and Cainozoic sediments (where present) and dips to the north-east. As the Rewan Group dips, its thickness increases from 50 m in the western part of the project site to 360 m in the north-eastern part of the project site.

The Permian coal measures include the Rangal Coal Measures and the Fort Cooper Coal Measures. The Permian coal measures comprise a sedimentary sequence with interbedded coal seams. The coal seams include:
• The Leichhardt seam targeted by the project and the surrounding mines, including Millennium Mine, Daunia Mine, Poitrel Mine and Moorvale Mine; and
• The Vermont seam targeted by the surrounding mines.

The Permian coal measures underlie the alluvium, Cainozoic sediments and Rewan Group (where present). Within the project site, the Permian coal measures are located at depths of between 100 m to 440 m.

The Permian coal measures dip to the north-east. As they dip, the thickness of the coal measures and the depth of the coal seams increase. The thickness of the Permian coal measures ranges from approximately 70 m in the western part of the project site to approximately 150 m in the north-eastern part of the project site. The depth of cover above the Leichhardt seam increases from approximately 110 m in the west of the project site to 450 m in the northeast of the project site.

A Cretaceous granitoid outcrops 5 km to the south-east of the project and comprises gabbro, leuco-diorite, diorite and granodiorite.

Within Carborough Downs South, economic coal is contained within the Permian Rangal Coal Measures (RCM) within the Bowen Basin.

Locally, the RCM are unconformably overlain by Tertiary sediments and basalt flows.

The sequence dips generally towards the north east at around 5-9 degrees, and becomes steeper around faults and at depth to the west.

The Leichhardt seam hosts the bulk of the resource at Carborough Downs South and is typically present as a clean 5.5 m seam of coal.

The Leichhardt seam mined in surrounding mines has been proven it can be washed to produce a hard-coking coal and a PCI secondary product for export markets.

The Vermont Upper seam is also classified resource in areas where it is >1.5 m thick.

Dimensions
The Carborough Downs South area covers a roughly rhombus shaped area in plan of 2.1 km by 3.3 km oriented in a NW-SE direction, covered by Fitzroy’s MDL 3046 as described above. The Leichhardt subcrops to the west of the lease, and occurs between 170 m and 670 m depth of cover within the lease.

Mining Methods

• Longwall
• Bord-and-pillar
• Continuous

Summary:

Carborough Downs Coal Mine (CDCM) is an operating underground longwall and bord and pillar mine located approximately 15 km east of Moranbah Township in Central Queensland. CDCM commenced bord and pillar mining in 2006 and longwall mining in 2009 and produces export coking and Pulverised Coal Injection (PCI) coal. The CDCM EA prescribes a maximum coal extraction rate of 5 Million tonnes per annum of Run-Of-Mine (ROM) coal.

Mining to date has only been within the Leichardt coal seam. The entire ML area is fully permitted to mine the Vermont seam throughout, which underlies the Leichardt seam 40-60m. Mining of the Vermont coal seam would extend the mine life by another 15-20 years after the Leichardt seam has been mined out.

Underground longwall mininng method to be used until the end of 2023, whereafter the longwall relocates to Ironbark. Mining of Vermont seam will be by Bord and Pillar & Longwall Mining Methods. Bord and Pillar (3 units) for 8-10 years. Longwall recommences in the 2030’s for a further 5-8 years.

Mining at Carborough Downs Mine is currently within the Leichardt seam where the virgin gas content needs to be pre-drained before mining to ensure safe operating conditions. As a result, Carborough Downs utilises a combination of surface to in-seam drilling (SIS) and underground in-seam drilling (UIS) to drain the gas to acceptable limits prior to mining. Surface to in-seam drilling is the primary means of gas drainage at Carborough Downs mine.

A pipeline gathering network has been installed to connect SIS gas wells and to deliver this coal seam gas to an onsite compressor station. The compressed coal seam gas is then transferred via a pipeline to the Moranbah Gas Processing Facility for domestic gas distribution.

The mine produces metallurgical coal sold to meet the growing needs of international steel demand.

The bord and pillar mining method involves dividing the target coal seam with underground roadway excavations. The coal seam is initially excavated along mined roadways (called ‘main headings’). The main headings are intersected at regular intervals by connecting roadways (called ‘cut-throughs’). Collectively, the main headings and cut-throughs are the bords. The cut-throughs are typically mined perpendicular to the primary headings creating a block-like array (or panel) of coal pillars bounded by the bords. Bell outs (small, fan shaped coal excavations) are also created at the ends of the bords to maximise coal extraction.

Mining is carried out by a continuous miner (cutting machine) that loads coal onto a shuttle car which transports and loads the coal onto an underground conveyor belt system. Once a bord is excavated to the required distance, the continuous miner moves to the next mining area and roof support is installed in the previous bord. The coal pillars support the overlying strata as the bords are mined and remain in place after the completion of mining.

PROJECT MINE LAYOUT
The width of the roadways (bords) will be 6 m. The final coal pillars will be 24 m by 24 m of solid coal. The coal extraction height will vary between 4.6 m and 6.0 m.

The project bord and pillar mine layout has been specifically designed with sufficient roadway and pillar strength to ensure that there will be no caving and the underground workings will be stable and safe. Consequently, the bord and pillar mining will not result in any significant surface subsidence above the underground workings.

Comminution

Crushers and Mills

Processing

• CHPP
• Jameson Cell Flotation
• Spiral concentrator / separator
• Wash plant
• Flotation
• Dense media separation

Summary:

An overland conveyor transfers raw coal from the underground mine for processing on site at a modern Coal Handling and Processing Plant (CHPP). The Carborough Downs CHPP operates seven days a week and is capable of processing 1,000 tonnes per hour.

The mine produces predominantly coking coal with PCI coal as a secondary product.

Coal from the underground workings is transported via overland conveyor to a ROM coal stockpile north-west of the conveyor drift portal. ROM coal is then transported from the ROM stockpile by an overland conveyor to the CHPP. ROM coal is washed at the CHPP. Product coal is transported from the CHPP via an onsite rail loop and train loading facility. Product coal is railed to the Dalrymple Bay Coal Terminal, for export.

CHPP Hub comprises 2x nominal 500tph CHPP Modules (stand alone), greater than 1Mt ROM coal stockpile and 750Kt product stockpile site, able to blend from multiple coal value locations.

Multiple product CHPP modules separated by size and density to multiple coal product specs.

Primary and secondary Dense Media Cyclones with spirals and TBS circuits and Jamieson cell allow ultrafine coal recovery.

Rejects drying circuits with rejects disposal to Dry Rejects Emplacement Area (DREA).

Two export products will be produced from the Project, a low ash coking fraction (HCC) and a pulverised coal injection fraction (PCI). An overall yield of approximately 77% is predicted, of which approximately 63% is expected to be HCC and 14% PCI. After processing, the product coal will be stockpiled at the existing CDCM product coal handling facility and loaded onto trains using the existing rail load-out.

Water Supply

Summary:

The Coal Handling and Preparation Plant (CHPP) utilizes only recycled water in its processing and mine affected water is applied for on-site uses wherever possible.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Executive General Manager	Andrew Vella		Dec 29, 2023
General Manager/SSE	Russell Uhr		Dec 19, 2023
Maintenance Superintendent	Louis le Roux		Dec 19, 2023
Mining Manager	Stephen Curtis		Dec 19, 2023
Process Manager	Andrew Hodgson		Dec 19, 2023