AVZ Minerals Ltd (ASX:AVZ) (OTCMKTS:AZZVF) (FRA:3A2) has updated the Manono Lithium and Tin Project resource in the Democratic Republic of Congo (DRC) to 401 million tonnes of spodumene-rich fresh pegmatite at a grade of 1.65% lithium oxide (Li2O), after including results from the recent pit floor drilling program at the Roche Dure pit.
Roche Dure resource at a cut-off of 0.5% Li2O as at 1 May 2021
AVZ managing director Nigel Ferguson said: “Geological modelling of the pit floor has confirmed the presence of high grade, fresh pegmatite in all of the nine resource holes drilled on sections 7100mN to 7300mN at Roche Dure.
“This additional information has resulted in the upgrade of some 12 million tonnes of Inferred Resources to Indicated Resources.
“Positive impact on the optimised DFS”
Ferguson added: “These additional tonnes, located at shallow depth in the existing pit, are expected to result in fundamental improvements to the mine design and mining schedule as the optimised mine model will treat the wedge material as ore, rather than waste.
“The lower strip ratio resulting from the increase in ore mined over the optimised mine plan, coupled with lower LOM cost assumptions, is expected to have a positive impact on the optimised DFS to be completed next month which will greatly assist our discussions with prospective financiers.”
Wedge drilling
The pumping of water from the Roche Dure pit was completed in February 2020. This provided drill rig access to determine the nature of the mineralisation in the area beneath the pit floor.
This area is referred to as the ‘wedge’ and was a portion of the mineral resource previously classified as inferred that could not be accurately evaluated with data acquired in the earlier drilling phases.
A total of nine diamond drill holes, inclined to the northwest and ranging between 72 metres and 276 metres in depth, were completed during 2020 and 2021.
The drilling has confirmed the continuity of the pegmatite and mineralisation within the ‘wedge’.
Resource upgrade
The updated resource included an updated geological model, based not only on the additional data, but also from a reinterpretation of previous data.
AVZ’s primary aim of the update was to upgrade the inferred resource material in the wedge to at least an indicated resource category.
The addition of the nine diamond holes drilled from the pit floor resulted in the wedge material being upgraded to indicated resources.
Tin potential
Roche Dure tin resource at a cut-off of 500 ppm tin as at 1 May 2021
An updated tin resource in remnant weathered pegmatite has been generated, requiring further investigation.
Given the marginal costs involved in mining the weathered material, the generally low cost of creating a high-value tin concentrate from weathered cassiterite-bearing rock, and the additional value that could be derived from tantalum, it is considered to have reasonable prospects for eventual economic extraction.