Cobre Ltd (ASX:CBE) has received a trade-off study that supports in-situ copper recovery (ISCR) of copper-silver mineralisation at the Ngami Copper Project in the Kalahari Copper Belt in Botswana.
The trade-off study — completed by METS Engineering — was designed to evaluate and rank the application of ISCR, underground and open-pit methods for mining/extraction of copper-silver mineralisation along the extensive strike of drill-tested mineralisation, which is estimated to contain between 103 and 166 million tonnes at 0.38% to 0.46% copper.
Cobre CEO Adam Wooldridge said: “The results from the trade-off study provide further support for our journey towards an in-situ copper-silver development at Ngami and justify further metallurgical, engineering and financial modelling.
"We look forward to reporting these results to the market as we progress towards completing our scoping study.”
Trade-off study findings
METS developed process flowsheets, process descriptions, mechanical equipment lists and process design criteria for the three mining/extraction options — open-pit, underground and ISCR — which were used to develop capital and operating estimates for each.
The trade-off study found the preferred extraction and process flowsheet to consist of an in-situ copper-silver well field, silver precipitation circuit and solvent extraction and electrowinning process which offers the best profit margin. This was based on analysis and current understanding of the geology, mineralisation of the ore body, metallurgy, mining, processing options and costs.
Under the study, extraction via ISCR returns robust economics — using a conservative copper recovery and price — justifying the next stage of engineering and design work to complete the financial capex and opex models.
Cobre hopes to bring the target into a JORC-compliant resource category, subject to results of an infill drill program. Cobre says there is potential for hybrid underground and surface in-situ developments to target high- and low-grade portions of that resource.
Work will now focus on completing the scoping study which will include results from ongoing hydrogeological modelling being and further metallurgical test work.
Advanced met test work
The company is now undertaking advanced metallurgical test work, including bottle roll, column, leach box and residue testing with results expected over the next four to five months, which will form the basis for estimating in-situ copper-silver recoveries and subsequent design of the pilot extraction program.
More than 50 kilograms of core samples have been selected from several diamond drill holes at the project’s Comet and Interstellar targets for further metallurgical test work.
Porosity, permeability, density, column leach, leach-box and residue tests will be undertaken along with mineralogy analysis. The test work, to be undertaken over four months, is expected to provide an estimate of the in-situ copper and silver recoveries along with metallurgical information needed to design a follow-on pilot plant.