Wonawinta Silver and Base Metals Project

History - The Wonawinta mine was originally developed by Cobar Consolidated Resources Ltd in 2011/12 as a shallow silver oxide project. Between 2012 and 2014 two of the four approved pits were commenced and their associated waste dumps were constructed. A Processing Plant and associated Run-of-Mine (ROM) Pad, stockpile areas, offices, workshops and water management structures were constructed along with the initial lifts of the Tailing Storage facility.  During this period the plant was modified with a log washer removed and a 400kw ball mill introduced to the flow sheet.  A larger 1800kw drive ball mill was installed in early 2015 by Black Oak Minerals specifically to grind the Mt Boppy gold ores which are considerably harder than the local Manuka ores.

Current - Manuka Resources Limited acquired the project in late 2016 and initiated a thorough review of operational history and identified various improvements which could be introduced at the site leading to a proposed restart of operations in early 2020.   During the non-operational review period, the company completed engineering reviews to allow for certification of the last tailings wall lift completed in 2013 by Cobar Consolidated and conducted a number of site audits for the EPA and Resources Regulator.  A comprehensive plant refurbishment plan was scoped and executed in late 2019 at a cost of some $5m.  This included stripping and inspecting all rotating machinery, repairs to the mill gearbox and installation of a fully refurbished mill motor (ABB) and numerous overdue maintenance projects.  A lift of the tailing storage facility was commenced in December 2019.

Development - The company will infill drill the current oxide resources on the mining lease to produce mineable reserves whilst testing the deeper mineralised sulphide ores (Ag, Pb, Zn) on the lease. This will occur whilst toll processing of the Mt Boppy gold ore is carried out.  Scoping studies have been completed to determine approximate capital estimates to add flotation capability to the existing flowsheet.  This would allow the plant to process its own sulphides or toll process third-party sulphides in the region, taking advantage of the strategic positioning of the Wonawinta plant in the southern extent of the Cobar basin.

Figure 2 Wonawinta plant flowsheet for initial Mt Boppy processing

Figure 3 Looking south at the Wonawinta plant