Marvel Gold Ltd (ASX:MVL) has intersected karst horizons in the majority of holes drilled to date at Lakanfla Gold Project in western Mali at various depths and thickness within the first 60 metres from surface.
The presence of karsts as a result of dissolution of carbonate rocks explains the extensive gravity lows seen at Lakanfla and are an important proof of concept because the dissolution is thought to be responsible for upgrading lower level gold into a potentially economic supergene enrichment zone.
First phase drilling began earlier this month, with eight holes for 1,653 metres out of a planned total of 3,800 metres completed to date.
First critical step
Executive director Chis van Wijk said: “We are encouraged that the rock types encountered by drilling to date have confirmed the presence of a karst at Lakanfla.
“This is the first critical step in the Lakanfla deposit model being pursued by Marvel.
“Our remaining holes are spaced around the 7-kilometre strike of gravity lows that we now know exist due to karst formation and carbonate rock dissolution processes."
Results by year-end
Due to the distance from the laboratory and the associated logistics of transporting the mass of samples collected during the program, Marvel Gold plans to despatch all samples at the conclusion of drilling, which is now expected to be mid-November.
The company expects results to be reported throughout December and these will confirm whether the extensive karst horizons are mineralised.
In a gold region
There are several reasons to be optimistic about the mineralisation potential at Lakanfla:
- It is 6 kilometres from Sadiola, one of Mali’s largest gold deposits;
- It is on the Senegal Mali Shear Zone, a structure responsible for a substantial number of large-scale gold deposits;
- There are extensive artisanal workings targeting high-grade veinlets in metasediments to the northwest of Target Zone 1; and
- The granite intrusion is mineralised, having been the focus area of historical drilling.
Artisanal gold workings
Lakanfla hosts a significant number of active and historic artisanal gold workings which are coincident with major geochemical and gravity anomalies.
Significantly, there is evidence of ground collapse at surface, as well as extensive voids and anomalous stratigraphy in drilling which are indicative of karst-style dissolution at depth within mapped carbonate rock units.
Karstification occurs when soluble carbonate-bearing units, for example, limestones, dolomites or marbles are dissolved.
The residuum left behind may be comparatively upgraded in certain insoluble minerals, in this case, the element of interest being gold.
This is one of the processes of supergene enrichment and this model is geologically analogous to the 4.5 million-ounce Yatela deposit around 35 kilometres northwest.
Of the historical drilling that has been undertaken at Lakanfla, 35 holes coincide with the priority targets, however, the majority of these holes were drilled no deeper than 75 metres.
Valid exploration target
Marvel Gold believes that a valid exploration target of this style exists at Lakanfla.
The company understands that the Sadiola gold mine will require additional oxide feed in the relative near-term and given Lakanfla’s proximity to the Sadiola processing plant, any discovery may be significant.