West African focused gold exploration company Cora Gold last month announced the final batch of assay results from the Tekeledougou project, in southern Mali, which confirm that the strike length of gold mineralised structures extends to at least 1.1 km at Kouroudian prospect and 350 m at Woyoni prospect.
The assay result highlights for combined reverse circulation (RC) and core drilling suggest gold is associated with an extensive array of narrow quartz veins splaying off primary shear zones with barren material between the veins, local grades up to 25 g/t, and multiple short vein sets with widths of 1 m to 2 m carrying gold grades ranging from 1 g/t to 4 g/t gold.
“The second phase of drilling which combined both RC and orientated core at Tekeledougou has been of value as it has successfully identified extensions to the mineralised structures and allowed us to better understand the distribution of gold mineralisation at the two prospects, Kouroudian and Woyoni,” says Cora Gold CEO Dr Jonathan Forster.
He says the results suggest that the company is dealing with multiple gold mineralised quartz veins set in “en-echelon fashion”.
“The frequency of the veining and its direct association with gold is encouraging. As is often the case in exploration, the controls to gold mineralisation prove to be more complex than envisaged from the first few drill holes.”
Forster notes that the association with en‐echelon zones of quartz veining mean that the company may elect to consider these as selective rather than bulk mining targets.
“We will continue to evaluate all the drilling data before planning the next stage in the programme at Tekeledougou. In the meantime, we look forward to the forthcoming end of the rainy season in Mali and recommencing our drill programme at our Sanankoro Gold Discovery which we believe has significant large‐scale potential.”
The Kouroudian prospect was subject to a second phase of RC drilling in June, with a total of 15 inclined drillholes (1 461 m) completed with hole lengths between 90 m and 120 m on drill azimuths of about 220º, the company announced in a statement.
“The drilling has now been completed over a strike length of nearly 1 100 m on fences mainly about 80 m apart, with the central 400 m on about 40 m spacings. “A single orientated core “tail” was also completed, central to the prospect with core collected from a depth of 63 m to 174 m. More usually, drilling has extended to vertical depths of about 80 m to 100 m.”
The company indicates that gold mineralisation is observed over the full 1 100 m of the structure and appears to be almost ubiquitously associated with the zones of more intense quartz veining. “As a consequence, fine visible gold can be observed in the pan over significant lengths where quartz veining is observed when RC drilling.”
Gold assays are more variable, ranging from anomalous values of 0.1 g/t gold over multiple metres, through to higher grades over select 1 m to 2 m intervals, usually in the range of 1 g/t to 4 g/t gold, with occasional spot values to 25 g/t gold or even 100 g/t gold.
An alteration halo, including iron carbonate, chlorite, pyrite and localised arsenopyrite, is evident across the prospect, with an indication at present that the gold may be a separate phase.
The company highlights that a total of six RC drillholes amounting to 504 m plus 252 m of pre-collar drilling for core “tails” were completed on two drill fences set about 80 m to the north and south of the previous drilling on azimuths of 220º.
Only anomalous gold values were recovered to the south, but gold intercepts to the north extend the length of the known mineralisation to 350 m. The company says water inflow into the RC holes prevented any deeper reconnaissance drilling.
The central 200 m of the prospect has previously been excavated by artisanal mining leaving behind a 70-m-wide flooded pit to depths of about 10 m to 15 m. The strong ground water flow encountered in RC drilling was overcome by completing four core “tails” on drill fences about 80 m apart over the centre of the prospect.
The company says a total of 411 m of orientated HQ core was drilled to hole lengths ranging from 150 m to 190 m. Fresh rock was generally intercepted from about 75 m to 90 m downhole, indicating that the vertical depth of oxidation lies at about 70 m.
In the excavated pit area, the quartz veining is associated with anomalous gold values of 0.1 g/t over intervals of about 30 m. Within this lie discrete individual intercepts of typically 1 m to 3 m length that commonly lie in the range of 1 g/t gold to 4 g/t gold.
Occasional observations of visible gold in the core supports the indication from bottle roll results that gold may have been introduced as a late phase in the development of the system.