Magmatic ore deposits in mafic-ultramafic intrusions of the Giles Event , Western 1 Australia 2

12 More than 20 layered intrusions were emplaced at c. 1075 Ma across >100 000 km 2 in the 13 Mesoproterozoic Musgrave Province of central Australia as part of the c. 1090–1040 Ma Giles 14 Event of the the Warakurna Large Igneous Province (LIP). Some of the intrusions, including 15 Wingellina Hills, Pirntirri Mulari, The Wart, Ewarara, Kalka, Claude Hills, and Gosse Pile contain 16 thick ultramafic segments comprising wehrlite, harzburgite, and websterite. Other intrusions, 17 notably Hinckley Range, Michael Hills, and Murray Range, are essentially of olivine-gabbronoritic 18 composition. Intrusions with substantial troctolitic portions comprise Morgan Range and 19 Cavenagh Range, as well as the Bell Rock, Blackstone, and Jameson–Finlayson ranges which are 20 tectonically dismembered blocks of an originally contiguous intrusion, here named Mantamaru, 21 with a strike length of >170 km and a width of > 20 km, constituting one of the world’s largest 22 layered intrusions. 23 Over a time span of > 200 my, the Musgrave Province was affected by near continuous high24 temperature reworking under a primarily extensional regime. This began with the 1220–1150 Ma 25 intracratonic Musgrave Orogeny, characterized by ponding of basalt at the base of the lithosphere, 26 melting of lower crust, voluminous granite magmatism, and widespread and near-continuous, 27 mid-crustal ultra-high-temperature (UHT) metamorphism. Direct ascent of basic magmas into the 28 upper crust was inhibited by the ductile nature of the lower crust and the development of 29 substantial crystal-rich magma storage chambers. In the period between c. 1150 and 1090 Ma 30 magmatism ceased, possibly because the lower crust had become too refractory, but mid-crustal 31 reworking was continuously recorded in the crystalisation of zircon in anatectic melts. Renewed 32 magmatism in the form of the Giles Event of the Warakurna LIP began at around 1090 Ma and was 33 characterized by voluminous basic and felsic volcanic and intrusive rocks grouped into the 34 Warakurna Supersuite. Of particular interest in the context of the present study are the Giles 35 layered intrusions which were emplaced into localized extensional zones. Rifting, emplacement of 36 the layered intrusions, and significant uplift all occurred between 1078 and 1075 Ma, but mantle37 derived magmatism lasted for >50 m.y. , with no time progressive geographical trend, suggesting 38 that magmatism was unrelated to a deep mantle plume, but instead controlled by plate 39 architecture. 40 The Giles layered intrusions and their immediate host rocks are considered to be prospective 41 for (i) platinum group element (PGE) reefs in the ultramafic–mafic transition zones of the 42 intrusions, and in magnetite layers of their upper portions, (ii) Cu–Ni sulfide deposits hosted within 43 magma feeder conduits of late basaltic pulses, (iii) vanadium in the lowermost magnetite layers of 44 the most fractionated intrusions, (iv) apatite in unexposed magnetite layers towards the evolved 45 top of some layered intrusions, (v) ilmenite as granular disseminated grains within the upper 46 portions of the intrusions, (vi) iron in tectonically thickened magnetite layers or magnetite pipes of 47 the upper portions of intrusions, (vii) gold and copper in the roof rocks and contact aureoles of the 48 large intrusions, and (viii) lateritic nickel in weathered portions of olivine-rich ultramafic intrusions. 49