Petrography, chemical composition, and age constraints of mafic intrusions from the Mesoproterozoic Soisson Intrusive Suite in the southeastern Churchill Province (Canada)

Abstract

Several kilometre-scale gabbroic intrusions with well-preserved cumulate textures occur over a ∼180 km northwest–southeast strike length area in the Core Zone, within the southeastern Churchill Province. These intrusions (1312–1311 Ma) are devoid of structural and metamorphic overprint and are mainly composed of olivine gabbro. Their overlapping petrographic, geochemical, and mineralogical characteristics suggest that all of these gabbroic intrusions are co-genetic and form the Soisson Intrusive Suite. The Soisson intrusions formed from basaltic parental magmas with low MgO (∼6–7 wt.%) and high Fe–Ti contents. Overall, they are similarly fractionated at the regional scale and incorporated various amounts of upper crustal material, as indicated by field (e.g., xenoliths, hybrid zones) and geochemical (e.g., high HILE/MILE, depletion in Nb±Ta) evidences. The Soisson Intrusive Suite has petrological, geochemical, and mineral chemistry similarities with the troctolite and olivine gabbro cumulates of the Voisey’s Bay and Mushuau intrusions from the ca. 1363 to 1289 Ma Nain Plutonic Suite (NPS), and appears to be contemporaneous with its younger gabbroic–troctolitic intrusion phase, suggesting that the Soisson Intrusive Suite and the gabbroic–troctolitic intrusions of the NPS were formed by similar petrological processes. Furthermore, like many gabbroic–troctolitic intrusions of the NPS (e.g., Voisey’s Bay intrusion), the Soisson intrusions contain Ni–Cu–Co magmatic sulfide mineralization. Among the Soisson intrusions, the Papavoine intrusion located in the southern part of this intrusive suite may be the most prospective intrusion as a Ni, Cu, and Co exploration target. Overall, the Soisson Intrusive Suite’s similarity with the NPS raises questions about their potential genetic link and magmatic connectivity at depth.