Overview

Deposit type

• Replacement
• Vein / narrow vein
• Sediment-hosted

Summary:

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 (Pb). Silver (Ag), copper (Cu), zinc (Zn) and gold (Au) are also present but are of much lower tenor.

The mineralisation included in this MRE can be divided into two main parts, the upper “Apron Zone” and the lower “Core Zone”.

The Apron Zone is comprised of stratiform massive and disseminated lead sulphide (galena), with minor antimony sulphide rich in zinc and silver (tetrahedrite), copper sulphide (chalcopyrite) and zinc sulphide (sphalerite) mineralisation within the lower conglomerate unit of the Edmund Basin Kiangi Creek Formation (KCLC) and the Upper Carbonate Unit of the Irregully Formation (UID). It extends for over 1,200m along strike and 750m down dip, dipping gently south.

Alteration products include jaspilitic rich sediments (Red Zone), barite alteration zone (Barite Zone) and a distinctive stratiform zone of hematite-magnetite alteration (Black Zone). In 2022, following considerable UG GC drilling, a distinct Red Zone Cap has been defined at the top of the Apron Zone, forming an impermeable barrier and trapping the mineralising fluids. No significant mineralisation occurs within the Red Zone Cap.

The primary mineralisation orientation within the Apron Zone is the stratiform orientation with secondary (high-grade) mineralisation occurring sub-vertically on a similar orientation to the core mineralisation lodes located underneath.

The Core Zone underlies the Apron Zone immediately below the Upper Irregully Carbonate Domain (“UID”). It is comprised of an elongate funnel-shaped body with intense chlorite alteration overprinting the clastic sediments from the Irregully Formation. Within the Core Zone, the high-grade lead sulphide mineralisation is predominantly hosted in intensely veined and brecciated zones with some disseminated fine-grained mineralisation present along preferred stratigraphic horizons, dipping gently to the south. The veining orientation is broadly east-west (110-290°), with sub-vertical dips varying from moderate north to steep south from south to north throughout the deposit. The vein mineralisation comprises quartz ± barite-dolomite + galena ± magnetite in the central to northern parts, with the addition of jaspilite observed in veins along the southern margin. High-grade zinc sulphide mineralisation (sphalerite) is found in the central and northeast portions of the Core Zone.

Copper (chalcopyrite) and gold mineralisation is sporadically found throughout the Core Zone but forms a semi-coherent body at the base of Core Zone which extends from 300m to 750m below surface and can be traced for over 1,000m along strike.

Dimensions
The Mineral Resource estimate encompasses all of the Abra Deposit which extends for 1200 m along strike and 800 m across-strike. The Mineral Resource lies between 250 m and 750 m below surface.

Mining Methods

• Longhole open stoping

Summary:

The Updated Mine Plan continues to assume long-hole open stoping (“LHOS”) is the primary mining method for Abra, with cement paste backfill.

In the steeply dipping Core Zone, MSO shapes generated were found to be representative of minable shapes, requiring only limited changes to the final stope shape. These sub-vertical stopes were designed with 25m sub-levels and a minimum mining width of 4m. The stopes ranged from 4m to 30m in width and the length of the stopes was limited to 10m based on the permissible undercut span of paste-fill.

The design of the Apron stopes was more difficult due to the variable flat dipping nature of the Apron Zone mineralisation ranging between 10 to 40 degrees. Manual stope shape drafting was required to reconcile against the MSO shapes. Blast hole lengths were limited to 25m for drilling accuracy, and this determined the sub level height intervals. Stope panels with dips greater than 31 degrees were designed with 15m sublevels and stope panels with dips between 22 and 59 degrees were designed with 10m sublevels. For the Apron stopes a minimum mining width of 3.5m was selected and a minimum footwall rill angle of 40 degrees set. The Apron stopes horizontal widths vary between 10 to 20m and the stope heights vary between 5 and 35m depending on ore thickness and whether multiple lodes can be mined in one stope.

The mining recoveries and dilution factors for development and stoping activities were estimated based on the rock mass characteristics, the mining environment, and the chosen mining method. Development designs assumed 100% ore recovery in all drives. A dilution factor of 5% was applied to all development grades. Stope designs assumed 5% ore loss to account for mining related issues including remote loader limitations and any ore/waste misallocation errors.

Overbreak was applied to the various stope shapes ranging from 0.2m to 1.0m depending on the regularity of the shape. This resulted in a dilution grade of 2.75% lead for the Apron Zone stopes and 3.5% lead for the Core Zone stopes. Stopes being mined below and adjacent to paste-fill received an additional 2% dilution to account for any paste-fill overbreak. A dilution grade of 2.0% lead was applied to the ore development.

Abra’s underground mine design generates the following mining metrics based on the Updated Mine Plan:
• Average tonnes per vertical metre = 40,000 t/vertical m;
• Total development = 56.3 km; and
• Total stoping tonnes and lead grade = 11.8 Mt @ 7.67% lead.

Underground mining of the first three levels of the mine (1,300mRL, 1,280mRL, and 1,260mRL) commenced in the first half of 2023 and has occurred predominantly in Apron Zone mineralisation. Some initial development has occurred in Core Zone mineralisation on the lowest of the three levels (1,260mRL).

The new Abra Central decline is being developed on the southern side of the orebody to gain access to the 1260mRL to 1250mRL levels on the central and eastern side of the mine. This decline will also enable new drill platforms to be established for multiple parts of the mine including Core lodes and recently discovered mineralisation outside of the MRE.

Mining and processing grade is slowly improving and will continue to do so in the coming months as new work areas are established and the ratio of stoping ore to development ore increases to required production levels.

Comminution

Crushers and Mills

Processing

• Flotation
• Dewatering

Summary:

The selected process flowsheet has been designed to produce a single high-value, high-grade lead- silver concentrate at maximum recovery. The plant flowsheet contains the following processing stages for the production of leadsilver concentrate:

• Three stages of crushing with fine ore bin storage and emergency stockpile with feeder.
• Single stage ball mill.
• Flotation and concentrate regrind to produce a lead/silver concentrate.
• Concentrate dewatering utilising a thickener and a filter to produce a transportable concentrate; and
• Tailings thickening and storage in a designated facility with bypass option to send tailings to the paste fill plant for provision of cemented paste fill to underground.

Grade recovery modelling of flotation data indicates that the Abra process plant will recover 93% lead, producing a lead concentrate expected to contain 75% lead and approximately 129g/t silver.

Several important milestones were achieved, including the completion of commissioning of the processing plant, first ore fed into the plant and first concentrate produced in January 2023. The processing plant achieved in-specification concentrate production from the commencement of concentrate production.

During January to March 2023 the plant only operated for approximately 50 days during this time with low levels of throughput around 2,000t per day increasing to the expected throughput levels of 3,600t per day, with an average of approximately 2,700t per day. The plant operated in a stop-start nature during this period due to ore availability during the commissioning and initial stages of ramp-up.

A significant rainfall event in April 2023 caused road closures and limited Abra mine site access resulting in a reduction in work hours and the closure of the processing plant. The Abra processing plant recommenced ore treatment on 3 May 2023 and other than a planned maintenance shutdown at the beginning of June, the plant operated continuously through to the end of June 2023 and was able to process all the ore mined. The plant’s instantaneous throughput rate was maintained at 150dmt/hr.

Lead metal recovery continued to improve, increasing from 37.7% in January to 86.1% in June. Ongoing improvement is expected to be achieved in metal recoveries with longer more consistent run times and improving feed head grade as stoping increases in the mine’s production profile. Processing plant performance is consistent with process flow-sheet design and throughput rates in each section of the plant is being achieved.

Water Supply

Summary:

A net raw water requirement of approximately 23.4L/s which is expected to be supplied by aquifers within 7km of the proposed processing plant.

Several production water bores have been established adjacent to the sites infrastructure during 2022 and these are tested and ready to adequately provide the water required for the mine processing and other activities.

Initial water being pumped from the underground workings is higher than initially predicted in the hydrology modelling and it is expected to reduce as mining continues, potentially returning the water extraction to longer term model predictions.

During the construction phase of the project excess water is being evaporated.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
Alternate Underground Manager	Brodie Edwards		Oct 14, 2023
General Manager	George Macpherson		Oct 14, 2023
Managing Director and CEO	Tony James		Oct 14, 2023
Processing Manager	Adit Nugraha		Oct 14, 2023
Underground Mine Manager	Jared Murton		Oct 14, 2023