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Three mafic-hosted, magnetite-related prospects called Jameson, Navigator and Latitude Hill occur in the most evolved, upper parts of the 1078 Ma layered intrusions belonging to the Giles Complex, Musgrave Province, Western Australia. The hosting layered intrusions are dominated by leucogabbronorite, gabbro and troctolite and each has a significant Fe-Ti oxide component comprising heavily disseminated, semi-massive and massive magnetite and ilmenite forming layers. Low grade Cu and PGE mineralization at Jameson and Navigator is strongly correlated with the presence of titaniferous magnetite. Copper, Au, Pt, Pd and S concentrations are low to very low below the first appearance of magnetite, but shift to significantly higher concentrations upon the first appearance of sulfide, which coincides with an increase in Fe 2 O 3 + TiO 2 + V 2 O 5 concentrations. Copper grades up to 0.42 wt.% and Pt + Pd + Au grades to 2 ppm are associated with S concentrations that rarely exceed 0.4 wt.%. There is a very low sulfide abundance, typically <1 modal%, dominated by Cu-rich sulfides, bornite and chalcopyrite (Cu/S ratios are typically >1). Cobalt-rich pentlandite and millerite are trace sulfides in these prospects, but pyrrhotite is rare or absent. Some of the Pt and Pd peaks are stratigraphically off-set from Cu and Au peaks. Mineralization is further characterised by high Cu/Ni ratios and low S/Se ratios indicating Ni partitioning into silicates prior to sulfide formation and very low or no crustal contamination. The Cu/Pd ratios at Jameson and Navigator show a clear shift from low Cu/Pd ratios below the sulfide-bearing magnetite zone to high Cu/Pd ratios above the base of the mineralization, highlighting that reef-type mineralization has been intersected. Mantle-normalised PGE patterns for Jameson and Navigator are PPGE > IPGE, which is typical for magnetite-related, reef-type Cu-PGE deposits. The Jameson mineralization is related to a <4 m thick magnetitite and has many characteristics that closely resemble reef-type mineralization in the Stella Intrusion, South Africa, whereas Navigator mineralization occurs in a >70 m thick, magnetite-bearing gabbronorite and websterite sequence and has more in common with reef-type mineralization at Rio Jacaré in Brazil. The Latitude Hill prospect is characterised by a >200 m thick zone of layered, semi-massive to massive magnetite, but it differs from Jameson and Navigator by having a sulfide assemblage dominated by pyrrhotite and very low whole rock Cu, Pt, Pd and Au grades. High Cu/Pd and S/Se ratios indicate that this intrusion experienced an earlier sulfide saturation event and that crustal contamination was an important factor in the formation of the sulfides at this prospect. A relatively flat mantle-normalised PGE pattern for samples from this prospect is similar to that from the Main Magnetite Layer from the Upper Zone of the Bushveld Complex. [ABSTRACT FROM AUTHOR]

More than 20 layered intrusions were emplaced at c. 1075 Ma across > 100 000 km 2 in the Mesoproterozoic Musgrave Province of central Australia as part of the c. 1090–1040 Ma Giles Event of the Warakurna Large Igneous Province (LIP). Some of the intrusions, including Wingellina Hills, Pirntirri Mulari, The Wart, Ewarara, Kalka, Claude Hills, and Gosse Pile contain thick ultramafic segments comprising wehrlite, harzburgite, and websterite. Other intrusions, notably Hinckley Range, Michael Hills, and Murray Range, are essentially of olivine-gabbronoritic composition. Intrusions with substantial troctolitic portions comprise Morgan Range and Cavenagh Range, as well as the Bell Rock, Blackstone, and Jameson–Finlayson ranges which are tectonically dismembered blocks of an originally single intrusion, here named Mantamaru, with a strike length of > 170 km and a width of > 20 km, constituting one of the world's largest layered intrusions. Over a time span of > 200 my, the Musgrave Province was affected by near continuous high-temperature reworking under a primarily extensional regime. This began with the 1220–1150 Ma intracratonic Musgrave Orogeny, characterized by ponding of basalt at the base of the lithosphere, melting of lower crust, voluminous granite magmatism, and widespread and near-continuous, mid-crustal ultra-high-temperature (UHT) metamorphism. Direct ascent of basic magmas into the upper crust was inhibited by the ductile nature of the lower crust and the development of substantial crystal-rich magma storage chambers. In the period between c. 1150 and 1090 Ma magmatism ceased, possibly because the lower crust had become too refractory, but mid-crustal reworking was continuously recorded in the crystallization of zircon in anatectic melts. Renewed magmatism in the form of the Giles Event of the Warakurna LIP began at around 1090 Ma and was characterized by voluminous basic and felsic volcanic and intrusive rocks grouped into the Warakurna Supersuite. Of particular interest in the context of the present study are the Giles layered intrusions which were emplaced into localized extensional zones. Rifting, emplacement of the layered intrusions, and significant uplift all occurred between 1078 and 1075 Ma, but mantle-derived magmatism lasted for > 50 m.y., with no time progressive geographical trend, suggesting that magmatism was unrelated to a deep mantle plume, but instead controlled by plate architecture. The Giles layered intrusions and their immediate host rocks are considered to be prospective for (i) platinum-group element (PGE) reefs in the ultramafic–mafic transition zones of the intrusions, and in magnetite layers of their upper portions, (ii) Cu–Ni sulfide deposits hosted within magma feeder conduits of late basaltic pulses, (iii) vanadium in the lowermost magnetite layers of the most fractionated intrusions, (iv) apatite in unexposed magnetite layers towards the evolved top of some layered intrusions, (v) ilmenite as granular disseminated grains within the upper portions of the intrusions, (vi) iron in tectonically thickened magnetite layers or magnetite pipes of the upper portions of intrusions, (vii) gold and copper in the roof rocks and contact aureoles of the large intrusions, and (viii) lateritic nickel in weathered portions of olivine-rich ultramafic intrusions. [ABSTRACT FROM AUTHOR]