Remodelling and re-interpretation of the geological and geophysical signatures of the Blue Rose prospect by the EL 2938 Joint Venture has indicated good potential for discovering a large porphyry copper-gold deposit at depth, beneath historical...
Remodelling and re-interpretation of the geological and geophysical signatures of the Blue Rose prospect by the EL 2938 Joint Venture has indicated good potential for discovering a large porphyry copper-gold deposit at depth, beneath historical shallow exploratory drilling. Therefore Pacific Magnesium Corp., as part of its commitment to earn a 51% share of the EL entitlement from Giralia Resources, applied for and was granted PACE Initiative funding from PIRSA to assist in drilling a deep diamond hole to test this porphyry target, which the farminee believes has characteristics similar to the 440-450 Ma (Ordovician) age porphyry deposits formed in the Lachlan Fold Belt of NSW, such as those being mined at Cadia-Ridgeway, North Parkes and Lake Cowal. A discrete circular magnetic anomaly in the western portion of the Blue Rose prospect is the principal indication of the buried target, while a coincident chargeability-resistivity IP anomaly has also been modelled as occurring beneath a zone of >1000 ppm Cu intersected in past drilling. Previous RC drill holes completed at Blue Rose by Lynas Gold had intersected disseminated and quartz vein - hosted sericite-pyrite at the base of several holes, apparently coincident with the top of the IP chargeability anomaly over a strike length of about 1 km. This chargeability anomaly, and the associated 2 km wide band of sericite-pyrite altered calc-silicate rocks (formerly carbonate-rich clastic rocks), are considered to represent the upper phyllic alteration halo above a potassic (magnetite -?K felspar/biotite) ?pipe-shaped porphyry target zone. The potassic magnetic porphyry target was inferred by Pacific Magnesium from its magnetic modelling to lie beneath the previous drilling, and to be slightly offset from the phyllic alteration halo. A linear, magnetite-rich portion of an interpreted co-genetic skarn is located 1 km east of the inferred porphyry target, and has encouraging copper and gold grades (up to 48 m @ 1.01 g/t Au, 0.82% Cu) over broad intervals associated with magnetite - rich calc-silicate rocks. Monzonite dykes with biotite selvedges have been intersected in shallow drill holes testing this linear magnetic portion of the skarn. The dykes and their fluid inclusions provide additional evidence of a mineralising intrusion at depth within the Blue Rose system. Previous drilling tested neither the magnetic anomaly nor adequately tested the IP anomaly. In the PACE-funded drilling programme, two RC precollars (BRDD005 and 006) were drilled first, to 155.0 m and 44.5 m respectively, after which, although two deep diamond drill tails had originally been planned to test the modelled magnetic source, only a single diamond hole, BRDD006, was completed to a total depth of 440.0 m. It encountered altered and sulphidic (pyrite) - rich sedimentary rocks, with minor copper sulphides, in the buried Neoproterozoic basement: however, no significantly magnetic rocks capable of explaining the modelled magnetic target were penetrated. Remodelling of the target body by geophysical consultants is planned prior to further drill testing. The monzonite porphyry dykes, plus the copper-gold-molybdenum mineralisation with associated hyper-saline fluid inclusions, that are seen in diamond cores recovered to date from beneath the Blue Rose copper oxide mineralisation zone, are still considered to confirm the appropriateness of the porphyry style target selected in this exploration project area.
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