Cobra Resources plc had reported results from 4 of 18 recently completed Reverse Circulation drill holes from Blue Rose, a copper-gold-molybdenum prospect within the Manna Hill Copper Project, located in the Nackara Arc, South Australia. Extensive, high-grade copper-gold and ancillary molybdenum mineralisation, adding scale to historical intersections. Standout results include: MHRC0018: 20m at 0.78% Cu, 0.14 g/t Au from 38m, and 74m at 1.02% Cu, 0.25 g/t Au from 70m, including: 14m at 1.52% Cu, 0.42g/t Au from 88m.
MHRC0017: 86m at 0.60% Cu, 0.14 g/t Au from 18m, including: 12m at 1.05% Cu, 0.09g/t Au from 32m, 12m at 1.10% Cu, 0.53 g/t Au from 58m. Drilling confirms down-dip continuity to the historical shallow, high-grade intersection within RABR822 of 47m at 2.2% Cu and 0.76 g.t Au from 11m. Preliminary interpretations infer a width of mineralisation of approximately 70m.
Additional diamond drilling is planned to validate true width estimates. Copper and separate outstanding molybdenum intersections include: MHRC0003: 56m at 0.34% Cu from 34m, including: 18m at 0.52% Cu from 38m, and 14m at 0.21% Cu, 0.01% Mo from 122m, and 10m at 0.12% Mo from 144m, including 2m at 0.38%Mo from 146m. Molybdenum grades are high and may add considerable upside.
The fact that molybdenum mineralisation is independent of copper-gold sulphides simplifies processing. Molybdenum is a primary pathfinder for porphyry vectoring and identifying the potassic alteration zone, which can host higher-grade copper mineralisation. The intersected molybdenum grades and their direct association to narrow, porphyry type intrusive(s) is evidence of a much larger mineral system.
These initial results, and the geological observations from the remaining drillholes, combine to strongly support scale within the Blue Rose skarn and a greater porphyry system. Results are partial for MHRC0003 and MHRC0001 with gold assays outstanding. Results from a further 14 completed RC drillholes are expected throughout March.
Requisite approvals have been received in respect of a planned programme comprising 29 RC drillholes and 3 diamond drillholes at Blue Rose. Cobra has a 12-month option to acquire the Manna Hill Project and is focusing initially on the Blue Rose priority prospect where previous drilling intersected copper-gold mineralisation along 1.6km of strike immediately adjacent to a geophysical anomaly interpretated as a porphyry intrusion. Under the Manna Hill Option Agreement, Cobra sought to test several geological observations that have implications for a large-scale mineral system at Blue Rose.
This included testing for the continuity of Blue Rose Skarn mineralisation at both depth and with increased strike. Initial results have been received from drill holes within Blue Rose 'Skarn' mineralisation. Results remain pending for: Further drillholes at Blue Rose testing depth and along-strike continuity.
Drillholes targeting skarn-style mineralisation at Neptune Rose - a geophysical target aligned north of and parallel to Blue Rose. Drilling targeting the Black Baccara Porphyry target; a large geophysical target north-west of the Blue Rose Skarn. A total of 18 drillholes (3,200m) were completed in February.
Unexpected excess water was encountered in many drillholes and resulted in some holes being terminated before targeted depths. Holes were terminated in a manner that shall enable targeted depths to be achieved with diamond tails should results warrant further drilling. Initial results have been received from: MHRC0001: 0 - 156m, MHRC0003: 0 - 156m, MHRC0017: 0 - 150m, MHRC0018: 0 - 150m.
Based on pXRF and visual observations MHRC0017 and MHRC0018 were prioritised for assay. MHRC0017 and MHRC0018 were designed to test the continuity of primary mineralisation below high-grade intersected within RABR822 of 47m at 2.2% Cu and 0.76 g.t Au from 11m. MHRC 0017 demonstrated that mineralisation is continuous through the transition zone from oxidized to primary mineralisation.
Most of the mineralisation in the intersection 86m of 0.60% copper and 0.14 g/t gold is considered to occur in the transitional zone. MHRC0018 intersected two distinct zones: An oxide intersection of 20m at 0.78% Cu, 0.13g/t Au from 38m downhole, and A primary sulphide zone of 74m at 1.02% Cu, 0.25 g/t Au from 70m downhole. This intersection is entirely within primary sulphide mineralisation.
Mineralisation intersected by drillholes MHRC0017 and 0018 has a true width of approximately 70m where downdip continuity appears strong. MHRC0018 is the best primary sulphide result reported from the project. MHRC0003 has established continuity of mineralisation associated with two dykes and mineralisation intersected in the following holes: Mineralisation within MHRC0003 shows connectivity between shallow oxide mineralisation within RABR205 that intersected 43m at 0.6% Cu from 12m and diamond drillhole BRDD003 that contains multiple low-grade zones and included: 16.15m at 0.51% Cu, 17.8m at 0.08% Mo from 144.2m, 5.8m at 0.13% Mo from 156.2m and 26.7m at 0.43% Cu from 195m.
Molybdenum mineralisation occurs in association with bedding-concordant dioritic intrusive rocks in each of these three drillholes. Recognition of this rock type/mineralisation relationship is expected to materially assist exploration for the porphyry-style mineralisation which is thought likely to exist nearby. High-grade (in excess of 1% copper) primary mineralisation lies open beneath the 130 metre vertical depth reached by drillhole MHRC0018.
Down-dip extensions of this mineralisation present an attractive target for planned diamond drilling. As the remaining drill-return assays are received over the coming fortnight, mineralisation geometry will be modelled, geochemical trends will be identified, and next steps will be determined. The Manna Hill Project presents South Australia's premier porphyry prospect in the state that holds around 70% of Australia's copper reserves.
The project is comprised of multiple early-stage porphyry and skarn prospects. The project also includes the Luron Carlin style gold prospect and multiple historic goldfields where over 30koz Au were reported to have been produced. This style of mineralisation remains underexplored and highly prospective.
The project sits along the national railway and Barrier Highway between the mining hub of Broken Hill, a port and base metals smelter, and the City of Adelaide.
