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Deposit Synonyms
Johnnies Hill; Kalkaroo South; Kalkaroo West; Mc 3826; Mc 3827; Mc 4368; Mc 4369
Mineral District
Deposit Summary
124.5Mt @ 0.5% Cu and 0.39g/t Au. Coarse molybdenite is ubiquitous, and a discrete inferred resource of 4.5Mt @ 615ppm Mo was defined. minor vein style U mineralisation, best assay result of 470ppm U in drillhole KKRC070.
Deposit Description
KALKAROO Cu-Au-Mo-Co (As-F-LREE-U) deposit discovered in the late 1970s below cover of 50-60m of Cainozoic sediment. Exploration has identified replacement-style mineralisation located on the northern, and faulted portion of a major structural dome. In gross shape the orebody forms an arcuate, N-dipping sheet, disrupted by faulting at its W end. The ore is sandwiched between well defined Foot and Hanging Walls, and is remarkably consistent and predictable along the 2.5km defined strike. The orebody shows supergene enrichment features in its upper part.
Hydrothermal fluids have replaced particular favourable units in a 150-200m thick mine sequence identified as of the Portia Formation. It has been subdivided into 3 units, a lower marble, middle albitic siltstone/calc-silicate, and upper marble. Footwall metasediment includes magnetite-bearing psammite, and albitic siltstone, hanging wall to mineralisation is lower albitic to upper graphitic pelite. The depositional environment was suggest as shallow water shelf. Structural preparation by major cross-cutting faults appears to have been an important mineralisation control.
Copper-gold mineralisation, typically chalcopyrite-dominant, with associated molybdenite, occurs as quartz breccias and stockworks developed within highly fractured and altered Portia Formation. Where transected by major fault zones, Cu, and especially Au grades, tend to be significantly higher, while Mo is generally absent. Also as stratabound replacement of carbonate, and of pyrite/pyrrhotite, which were in turn developed during diagenesis, replacing chemically reactive carbonate and sulphate bands and nodules in the host Portia Formation sequence. Finally as quartz breccias and stockworks in the crosscutting faults, both laterally outwards and below the mineralised Portia Formation. Minor vein style uranium mineralisation was also recorded, with best assay of 470 ppm U from 109-112m in hole KKRC070.
4 ore types have been identified, supergene free gold, and native copper, largely recoverable by gravity methods; native copper and gold proximal to high-grade primary copper zones, also recoverable by gravity methods; chalcocite-dominant Cu-Au ore; chalcopyrite-dominant Cu-Au ore, with metals recoverable by conventional flotation methods for the latter 2 ore types. Testwork achieved gold recoveries in sulphides averaging 60-65%, with updated testwork improving recovery to 87% from chalcopyrite material, and 78% from chalcocite.
Age dates include host depositional age 1715-1700Ma, 1632-24 Re-Os age (hydrothermal?), Mo sulphide deposition at 1605±12Ma, and Cu-Au and further Mo, mostly at ~1588 to 1583 Ma.
Total resources as announced on 29/3/2017 were 232.5Mt @ 0.49% Cu and 0.37g/t Au (havilahresources.com). Also an additional resource of cap gold of 21.7Mt supergene gold ore at 0.74g/tAu. There is potential for recoverable coarse molybdenite, and cobalt from resources of cobaltiferous pyrite.
Re-assaying of Havilah drill samples at West Kalkaroo returned elevated levels of rare earth elements(REE) from DDH KKAC0421, interval sampled from 72-73metres included 2030ppm(Ce), 2150ppm(La), 1355ppm(Nd) and 366ppm(Pr) - Havilah Resources ASX Media Release 7th January 2020
Discovery Year
? 1992
Commodities
Copper, Gold, Molybdenum, Cobalt
Ore Minerals
Azurite, Bornite, Chalcocite, Chalcopyrite, Copper, Covellite, Gold, Malachite, Molybdenite
Gangue Minerals
Amphibole, Biotite, Calcite, Feldspar, Goethite, Kaolinite, Magnetite, Pyrite, Pyroxene, Quartz, Rutile
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