Age constraints and geochemical evolution of the Neoarchean mafic–ultramafic Wabassi Intrusive Complex in the Miminiska–Fort Hope greenstone belt, Superior Province, Canada

• Published in: Precambrian research 2016-11, Vol.286, p.101-125
• Main Authors: Sappin, A.-A., Houlé, M.G., Lesher, C.M., McNicoll, V., Vaillancourt, C., Kamber, B.S.
• Format: Article
• Language: English
• Subjects: Layered intrusion; Mafic intrusion; Miminiska–Fort Hope greenstone belt; Neoarchean; Superior Province; Ultramafic intrusion
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2016.09.018

•Max, Wabassi Main, and Wabassi South intrusions form the Wabassi Intrusive Complex.•Wabassi Intrusive Complex formed between 2728 and 2727Ma.•All parental magmas are basaltic (up to ∼12% MgO).•Max intrusion may be the most prospective area for Ni–Cu–(PGE) exploration.•Oxtoby Lake intrusion younger (2717Ma) and unrelated to Wabassi Intrusive Complex. The ca. 2.75–2.71GaMiminiska–Fort Hope greenstone belt (MFHGB) of the eastern Uchi domain of the Superior Province (northern Ontario) contains numerous mafic and ultramafic intrusions hosting Ni–Cu–(PGE) occurrences. The most significant, the mafic–ultramafic Wabassi Intrusive Complex and the nearby mafic Oxtoby Lake intrusion, formed between 2728 and 2727Ma and at ca. 2717Ma, respectively. The Max, Wabassi Main, and Wabassi South parts of the Wabassi Intrusive Complex and the Oxtoby Lake intrusion have been studied to establish their petrogenesis and metallogenesis, and to compare them to the highly prospective 2734Ma mafic–ultramafic intrusions in the McFaulds Lake greenstone belt∼120km to the north that host world-class Cr-(PGE), significant Ni–Cu–(PGE), and potentially significant Fe–Ti–V mineralization. The ca. 2728Ma ultramafic-dominated Max intrusion is relatively homogeneous in composition, comprising mainly harzburgite, lherzolite, and wherlite with minor olivine orthopyroxenite, orthopyroxenite, websterite, and mesocratic gabbroic rocks. It also contains disseminated to patchy net-textured Fe–Ni–Cu–(PGE) sulfides. In contrast, the ca. 2727Ma Wabassi Main intrusion is a layered mafic-dominated intrusion that consists of: (1) a basal zone containing leucocratic to mesocratic olivine gabbronorite and olivine norite, troctolite, lherzolite, and harzburgite with high Cr contents, olivine with Mg#78–72, orthopyroxene with Mg#84–67, clinopyroxene with Mg#95–91, and plagioclase with An96–37, (2) a lower zone containing mesocratic olivine gabbronorite-gabbro-norite and up to 10% Fe–Ti oxides, olivine with Mg#64–19, orthopyroxene with Mg#67–58, clinopyroxene with Mg#80–56, and plagioclase with An79–46, (3) a middle zone containing leuco- to mesocratic gabbronorite with up to 8% Fe–Ti oxides, orthopyroxene with Mg#57–56, clinopyroxene with Mg#73–66, and plagioclase with An71–63, and (4) an upper zone containing mesocratic gabbronorite, gabbro, and ferrogabbroic rocks with up to 50% Fe–Ti oxides, up to 8% apatite, low Cr and high P contents, orthopyroxene with Mg#44, clinopyroxene with Mg#60, and plagioclase wit