Magmatic ore deposits in mafic–ultramafic intrusions of the Giles Event, Western Australia

Abstract

More than 20 layered intrusions were emplaced at c. 1075 Ma across N100 000 km 2 in the Mesoproterozoic Over a time span of N200 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 N50 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.

New insights into the petrogenesis of the Jameson Range layered intrusion and associated Fe-Ti-P-V-PGE-Au mineralisation, West Musgrave Province, Western Australia

“…From 2004, the GSWA mapped the West Musgrave Province on a 1:100,000 scale (Howard et al 2011b). A comprehensive account of the petrogenetic aspects and the prospectivity of the Giles Complex was produced by Maier et al (2014Maier et al ( , 2015.…”

“…However, the Alcurra Dolerite Suite hosts a number of recently discovered magmatic sulphide occurrences, such as Nebo-Babel (Seat et al 2007), Manchego (Karykowski et al 2015) and Halleys . Detailed reviews of the Musgrave Province including its mineral potential as well as its tectonic evolution are provided by Glikson et al (1996), Smithies et al (2008), Maier et al (2015) and Howard et al (2015).…”

“…Moreover, a direct U-Pb zircon age of 1076 ± 4 Ma was obtained from a G1 leucogabbro east of the Jameson Range . According to Maier et al (2015), the Jameson Range represents the upper part of a tectonically dismembered portion of an originally contiguous body termed BMantamaru Intrusion^. Outcrop in the Jameson Range is generally poor with the basal and top contacts of the intrusion not being exposed.…”

Evaluation of Platinum Group Elements (PGE) Potentials of Ultramafic Rocks of the Paleoproterozoic Nyong Series, Southeast Cameroon

“…Ultramafic rocks are often found in large intrusions where differentiated rock types commonly occur in layers (Ballhaus and Ryan, 1995, Maier et al, 2015Randive et al, 2015). Examples of these rocks include pyroxenite, peridotite, hornblendite, anorthosite, dunite, gabbro and norite.…”

Contact-style magmatic sulphide mineralisation in the Labrador Trough, northern Quebec, Canada: implications for regional prospectivity

“…The orientation of the mafic rocks is of major importance in designing effective ore targeting trend towards relatively unevolved compositions with height across the Idefix sill. While this could suggest that the Idefix sill has been tectonically overturned, it is also known that many mafic intrusions show basal reversals on the scale of meters to hundreds of meters in relation to a progressively decreasing trapped liquid component with height in the sill (e.g., Wingellina Hills;Maier et al 2015).…”