IMX Resources' (ASX: IXR, TSE: IXR) final results from deep copper exploration drilling beneath its Cairn Hill Magnetite-Copper mine in South Australia have confirmed the presence of sulphides with low levels of copper.
The three diamond core holes were drilled to explore for depth extensions to the Iron Oxide Copper Gold mineralisation currently being mined from Cairn Hill.
"These results, while encouraging from a geological perspective, seem to indicate that there is unlikely to be an economic case for extending the current Cairn Hill Mining Operations any deeper than the current pit design," managing director Neil Meadows said.
"That said, we will continue to consider the depth potential at Cairn Hill as well as work with our joint venture partner OZ Minerals on exploration for IOCGs in the broader Mt Woods area."
The company added that the IOCG magnetite alteration thickens and continues beyond all drilling while geological folding was found to have a strong effect on the distribution and grade of copper and magnetite mineralisation.
Deep Exploration Drilling
Two angled diamond core holes CHDCU01 (550.5 metres) and CHDCU02 (600.8 metres) tested target zones beneath Pit 1 and Pit 2 respectively.
CHDCU03 was drilled to a depth of 449.8 metres about 1.2 kilometres to the west of CHDCU02 to explore for western extensions to the magnetite hosted copper-gold mineralisation in an area not previously drilled and that is obscured by a thick sequence of sediments.
The best copper intersections came from CHDCU02, which revealed that the Northern Lode increases from 15 metres wide near the surface to a 50 metre wide zone of dispersed magnetite at 300 metres below the surface.
The structural broadening was associated with an increase in sulphide mineralisation - pyrite and pyrrhotite - and a dispersal of the magnetite alteration however with corresponding weakening of copper levels.
The increase in iron sulphides around the margins of the deposit may be part of a broader halo that surrounds the copper and iron mineralisation.
Greater understanding of this halo could help with refining copper exploration at the Company's Mt Woods Copper-Gold Joint Venture project with OZ Minerals (ASX: OZL).
Down-hole magnetics surveys were conducted on CHDCU01 and CHDCU02 using a Digi-Atlantis three component magnetometer, confirming that had not missed any nearby potentially copper bearing magnetite bodies.
CHDCU03 drilled through 329m of sediments before intersecting the magnetic target that comprises magnetic gneiss interlayered with foliated granite.
The magnetite gneiss is more similar to Snaefell gneiss rather than the massive Cairn Hill magnetite. The best copper assay was 0.6 metres at 970ppm copper and 9% iron.
Copper mineralisation at Cairn Hill is hosted within two near-parallel magnetite rich units named the Northern and Southern Lodes.
Thickening of the magnetite lodes was believed to be the key for finding copper mineralisation, as previous drilling had shown that copper occurs optimally where the magnetite generally assays in excess of 50% iron and the lode is wider than 10 metres.
At the eastern end of Pit 1, the Northern Lode reaches its maximum width at 40 metres and also hosts the highest copper grades (0.5%-1.3% copper).
To the west, the Northern Lode narrows to less than 10 metre wide and the copper grade is lower (0.4%-0.9% copper).
Geological structure mapping of Pit 1 has previously demonstrated that zones of folding have enhanced the width of the magnetite and were associated with improved copper grades.
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