Summary:
Coppabella Moorvale Joint Venture (CMJV) coal deposits comprises coal seams hosted within a sedimentary interbedded package of sandstone, siltstone and mudstone. The depositional environment is interpreted as entirely alluvial with little evidence supporting marine influence. Sandy river channels traverse extensive peat mires where the peat mounds constrain the channels. Periodic high sediment flow events occasionally breach the peat levy and form lobed splays of sand and silt which cover and compress the peat. Peat growth establishes on the new surface as the locus of deposition shifts away and a second seam is established. This second seam merges with the first seam at the edges of the splay, often at a steep angle due to peat compaction related bed rotation.
The deposit types of Coppabella and Moorvale South are considered to have high geological complexity based on the following factors:
- Presence of intrusive sills and dykes within the Coppabella and Moorvale South deposits. This can have negative impacts on coal product yields as adjacent heat affected coal has a higher relative density and can therefore be lost during lower density washing at the coal handling and preparation plant (CHPP);
- There are multiple thrust faults across Moorvale South. Whilst tonnages maybe be increased in close proximity to the thrust, quality estimates can vary due to duplication of plies within the seams and existence of fault breccia which may lead to increased ROM dilutions.
Burial during the Triassic and Jurassic raised the rank of the coal to low volatile bituminous (ASTM). The major product sourced from the Coppabella and Moorvale deposits is low-volatile PCI coal but coking and thermal fractions are locally generated through beneficiation of the seams at Moorvale. Moorvale South is expected to produce predominantly Semi-Hard Coking Coal through blending of seams within that deposit, with PCI and Thermal produced where the washed qualities don’t support creation of a Semi-Hard Coking Coal (SHCC) product.
Moorvale
The Moorvale deposit lies approximately 15 km to the southwest of Coppabella where the sediments have been raised in a ring around the Bundarra Granodiorite. The strata strike north-east and dip westwards into the Nebo Synclinorium at 6 to 20.
Numerous normal faults radiate away from the Bundarra Granodiorite in a northwest direction and these are likely to be associated with the late movement of the strata associated with the emplacement of this intrusive unit. Reverse faults are also evident at Moorvale mine, these appear to be reactivated faulting of previous normal faults.
The plies of the Phillips and Leichhardt Seams are coalesced across most of the deposit forming a single 10 m thick seam which is the source of all coal production from the mine. To the north and south, several roof splits occur. Below the base of the Leichhardt seam is characterized by a carboneous mudstone unit often referred to as a the HAF (High Ash Floor).
The Vermont seams have been intersected in a few holes at Moorvale mine. However, they are not currently targeted for mining at Moorvale mine as they are considered uneconomic due too high ash content and low yield.
The coal plies at Moorvale retain the regional naming convention and are denoted from top to base as the PHI (Phillips), LU1 (Leichhardt Upper 1), LU2 (Leichhardt Upper 2), LL1T (Leichhardt Lower 1 Top), LL1B (Leichhardt Lower 1 Base), LL2 (Leichhardt Lower 2).
The main seam is also divided according to the coal quality properties which reflect the dulling upwards trend in the coal seams of the RCM. There are 3 working sections with the aim of producing 3 mining products. Generally the Top Working Section (TWS) comprises the Phi ply and LU1 ply to produce a PCI product. The Middle Working Section (MWS) comprises the LU2 and LL1T plies and produces a high ash PCI product. The Lower Working Section (LWS) comprises the LL1B and LL2 plies and produces a coking or PCI product. Ply combinations for the working sections can vary towards the north and south of the deposit, depending on the qualities required to meeting blending requirements.
Moorvale South
The Moorvale South tenements cover an area of the Nebo Synclinorium where the geological structure is dominated by a series of Cretaceous intrusions formed along an east-northeast trending lineament. The westerly dipping seams of the Moorvale deposit strike southwards through MDL 3034 following the arcuate trend around the eastern Bundarra Igneous Complex intrusions, significantly narrowing the main syncline. Several smaller intrusions are inferred to the west including the Daunia intrusion which forms a ring-like structure in the southwest of MDL 3034. The proposed initial mining area is located further south on ML 70354, along the western limb of the Coxendean Syncline where the seams dip to the east between 5 and 20 . Localised intrusions have been encountered through exploration drilling within the Leichardt and Vermont seams in this area, causing the seam to be heat-affected and partially replaced by the intrusion. The intrusion is modelled as parting in this instance.
The project area features a series of faults interpreted from drilling information, geophysical surveys and geological modelling. Interpreted project area thrust faulting is generally observed to trend northwest-southeast and possess displacements of up to =30m.
Identified coal resources are predominantly hosted in the Leichhardt Seam package with lesser contributions from the Vermont Seam. Within ML 70354, the Leichhardt Seam package occurs as 2 seams; the LL2 and LL3, and the Vermont Seam package comprises the VU of the RCM and the VL1 of the FCCM. The LL2 is composed of the LL2T and LL2B plies which together range from 2.8 to 4.8 m thick. The coal is generally banded with the proportion of bright to dull bands increasing towards the base. The LL3 comprises interbedded carbonaceous mudstone and bright coal bands, ranging from 1.0 to 1.6 m thick averaging 1.5 m.
The Vermont Seam occurs approximately 40 m below the LL3 and comprises the Vermont Upper (VU) and Vermont Lower (VL) separated by the Yarrabee Tuff (YT). The VU is further divided into a dull, upper ply (VU1) and brighter lower plies (VU2 and VU3). The combined VU ranges from 2.5 to 3.7 m thick and is heavily intruded and cindered in the southern half of ML 70354. The VL seam is also divided into 3 plies; an upper, banded coal (VL1) and 2 lower, stony coals (VL2 and VL3). The VL1 averages 1.3 m thick and is the only FCCM ply contributing to the Moorvale South resource in the Y-pit and Y-pit North areas only.