Minotaur Exploration Limited | ASX:MEP

Exploration for IOCG and ISCG copper-gold giants : How different can they be? A. P. Belperio

SA Exploration and Mining Conference Adelaide, 2 December 2016

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Geophysical Methods in Mineral Exploration

Given ubiquitous and problematic cover over much of Australia, exploration for IOCG style deposits invariably requires a geophysical approach. In this short presentation, I hope to show how that approach needs to be tailored to the mineralogical characteristics of the model target, as well as the problematical issues of getting geophysical signals to "see" through the cover. Simultaneously, we can answer the question of… "are there a broader number of IOCG deposit styles in the Gawler Craton than hitherto documented".

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Fe-Cu-Au Deposit Styles

IOCG's whether magnetite or haematite dominated, are part of a larger family of Fe-Cu-Au deposit styles that include, where host strata/fluids are significantly reduced, an Iron Sulphide (ISCG) style. This style is largely untested in SA and requires a significantly different approach and exploration toolbox

IOCG Deposit

Examples

Mineralisation

Form of Iron

Targeting

Styles

Methodology

Ironstone Hosted

Osborne (part), Starra, Peko, Geko

Cu-Au-Bi

Mag, Po, Hm

Magnetics, Gravity

Haematite Breccia

Olympic Dam, Prominent Hill

Cu-Au-U-REE

Hm

Gravity, IP

Magnetite Breccia

Ernest Henry, Candelaria, Salobo

Cu-Au

Mag, Bio

Magnetics, Gravity

Magnetite-Apatite

Kiruna, Acropolis

minor

Mag

Magnetics

Iron Sulphide

Eloise, Kulthor, Osborne (part), Cormorant, Artemis, Iris

Cu-Au-Zn-Pb-Ag-Co

Po, Py

Electrical Conductivity

Cobaltiferous

Nico

Au-Bi-Co-Cu

Mag, Hm, Bio

Magnetics, Radiometrics

Common Features: Bimodal igneous activity, mantle tapping structures, extensive regional Na and K alteration and widespread Fe metasomatism

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IOCG - ISCG Mineralisation Styles

IOCG deposits (magnetite or haematite-rich; disseminated, breccias) (Ernest Henry, Prominent Hill):

  • Breccia bodies seeking dilational openings

  • Oxidised terranes, magnetically active

  • Fe oxide host bodies (magnetite, haematite) and alteration haloes

    generate gravity and magnetic anomalism

  • Strong IP chargeability anomalies

  • Broad alteration haloes

  • Weak to no EM anomalies

    ISCG deposits (pyrrhotite-rich; massive, high grade) (Eloise, East Osborne, Kulthor, Cormorant, Artemis, Iris):

  • Tabular bodies following fault structures and rheological contacts

  • Reduced terranes, magnetically quiet (carbonaceous and graphitic shales)

  • Fe in form of pyrrhotite and pyrite; may be completely non magnetic

  • Weak to no regional gravity anomalism

  • Strong ground EM anomalies

Note all currently known ISCG deposits in Australia are in the Cloncurry District. Can they exist in the Gawler??

Ernest Henry

Prominent Hill

Eloise Osborne

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