RED ROCK RESOURCES PLC Red Rock Resources Plc. (‘Red Rock' or ‘the Company') announced that further to the announcement of 11 October 2021 and later updates, the results of the reverse circulation (RC) drill programme at the Luanshimba copper-cobalt project in the Haut-Katanga Province of the Democratic Republic of Congo. The Luanshimba project is operated by Red Rock Galaxy SA, an 80% owned Congolese subsidiary of Red Rock.
The drill programme was carried out by Rubaco SARL, with geological supervision being provided by Minerals Exploration Associates SARL (‘Minex Consulting SARL' or ‘Minex'). Red Rock owns 80% of the Luanshimba Project, which is situated 65 km south-east of the provincial capital of Lubumbashi in Haut-Katanga, in a 420 hectare prospecting license (PR13513) in the Congolese Copper belt. The tenement is situated along a disrupted anticline with Roan sediments draping off a nearby basement dome.
Drilling tends to confirm the historical geological overview that most of the permit is underlain by a gently NW-plunging asymmetric syncline whose westerly limb is best revealed by probing in Luanshimba North. Here, there is a thick sequence of interbedded siltstones, shale and dolomite that is probably correlative of the Zambian Kitwe formation which includes the ‘Ore Shale' horizon. There is a tendency for thicker dolomite to prevail in the more northerly holes which would equate more likely with the Upper Roan.
However, the sequence is severely disrupted by thick breccias that may have an easterly to NW-SE orientation. However, without diamond drill core, the positioning of the optimum ore bands and their equivalence with the Katangan Mines Series still needs to be determined. In both Kilembwe and Luanshimba North prospects, the RC drilling was placed along 14 cross-sections 100 metres apart; 12 are oriented SSW-NNE, approximately perpendicular to the presumed structural and stratigraphic strike.
The remaining 2 are situated in the Luanshimba East Prospect. While relatively few potentially economically significant intercepts were documented, 1-6m segments of sub-marginal Cu (0.1-0.4% Cu) along with Co close to or just above the 0.1% cut-off occur mostly in dolomite and immediately adjacent siltstones. The possibility of redox contrasts and a less permeable capping by pelitic sediments cannot be ruled out.
In the Kilembwe area, siltstones, silty arenites and shales dominate over dolomitic beds and in the southernmost holes overlie sandstone and arkosic arenites typical of the footwall to mineralization in the Zambian stratigraphy. However, the inferred arcuate easterly trending fault and associated breccias disrupt the sequence and bring the footwall arenites much closer to the surface in the southern holes. Despite the absence of Cu in the footwall sandstones, the Cu soil geochemical anomaly still persists until the edge of the permit because of redistribution by weathering from siltstones, breccias and dolomites that overlie arenites.
Sub-marginal Cu and significant cobalt occur mostly in argillaceous sediments much more frequently than in dolomite, particularly where they have been fractured and brecciated while localized enrichment occurs in association with shallow weathered breccias and fault gouge. With only 2 holes at Luanshimba East and deep weathering, results are too sparse to comment with authority except that some significant superficial enrichment was noted (DRC023). The sequence appears to be highly disturbed by faulting as both sandstone and dolomite are juxtaposed.
Regarding copper, good results were received from two holes DRC014 and DRC021 in both Kilembwe and Luanshimba North prospects. DRC 014 revealed 1m at 1.45% Cu using a cut-off grade of 1% Cu and 6m at 0.61% Cu with a cut-off grade of 0.5% Cu, while DRC021 returned 3m at 1.14% Cu with a cut-off grade of 1% Cu. In both holes the mineralised zone occurs as hypogene chalcopyrite hosted in a greenish grey dolomite underlying 5 to 10 metres thick carbonaceous shale carrying pyrite.
This might indicate the hole intersected a more distal pyrite zone, and the chalcopyrite occurring below indicates a vector towards better copper mineralization. Additional holes showed modest to mediocre Cu values at a cut-off grade of 0.5% Cu. DRC019 drilled in Luanshimba North intersected 3m at 0.70% Cu.
In this hole, copper occurs as chalcopyrite in the same greenish-grey dolomite underlying the carbonaceous shale. At Luanshimba East, DRC023 contained 2m at 0.70% Cu hosted in the lateritic overburden and is most likely associated with superficial secondary enrichment. The Luanshimba North Prospect is believed to occur in the Kitwe Formation or its Katangan equivalent and locally is characterised by dolomite, dolomitic siltstone alternating with chert, carbonaceous shale, argillaceous siltstone and in places intensely brecciated zones.
Copper mineralisation is displayed as disseminated and blebby chalcopyrite overlying a pyritic zone characterised by fine grained disseminated pyrite hosted in the carbonaceous shale. Regarding cobalt analyses, good results were obtained from most of the RC holes drilled in the Kilembwe Prospect. Cobalt mineralisation occurs as heterogenite in replacement mode within fault gouges and strongly brecciated layers affecting the Mindola Formation.
Good results were received from DRC015 which intersected 43m at 0.13 % Co including 11m at 0.20% Cu hosted in a brecciated argillaceous arenite. DRC014 cut 12m at 0.11% Co hosted in fault gouge. DRC008 reveals 3m at 0.37% Co related to a fault gouge that overlies 13m at 0.10% Co hosted in a brecciated argillaceous arenite.
DRC010 shows 8m at 0.14% Co hosted in fault gouge. In the Luanshimba East Prospect, excellent results were received from DRC023 with 5m at 0.78% Co including 2m at 1.59% Co. Here, cobalt mineralisation occurs as superficially enriched heterogenite hosted in the lateritic overburden and is associated with low grade copper.
In both Luanshimba North and East Prospects, cobalt mineralisation occurs as matrix replacement associated with black iron oxides hosted in fault gouge (DRC024) and/or in weathered fractures in carbonaceous shale and dolomite. An examination of the overall thickness and the grade of the intercepts identified two separate zones: the first coincides with the Kilembwe Prospect which occurs in the Mindola Formation. Supergene oxide mineralisation is mostly related to the faulting system in this target.
A plot of the cumulative thickness of the cobalt intercepts shows a SSW-NNE trend and is open towards the SW. Note that the cobalt mineralisation intercepted in the DRC014 (1m at 1.14% Cu and 0.16% Co) is apparently not related to any fault system. On the contrary, the cobalt mineralisation lies within both argillaceous dolomite and dolomite associated with a reduced litho-facies that may also be responsible for enhanced copper grades.
