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TitleProject Unit 13-008. Geology and geochemistry of the Thunder Intrusion, Midcontinent Rift, Thunder Bay, Ontario
AuthorSappin, A A; Houlé, M G; Lesher, C M; McNicoll, V J
SourceSummary of field work and other activities, 2013; by Ontario Geological Survey; Ontario Geological Survey, Open File Report 6290, 2013 p. 57.1 - 57.7
Alt SeriesEarth Sciences Sector, Contribution Series 20130268
PublisherOntario Geological Survey
Mediapaper; on-line; digital
File formatpdf
AreaThunder Bay
Lat/Long WENS-89.3333 -89.2667 48.5500 48.5167
Subjectsmetallic minerals; structural geology; igneous and metamorphic petrology; intrusive rocks; mafic rocks; ultramafic rocks; mineralization; nickel; copper; lithology; magmatic deposits; bedrock geology; metavolcanic rocks; cores; field relations; alteration; sills; Thunder intrusion; Shebandowan greenstone belt; midcontinent rift; Precambrian
Illustrationslocation sketch maps; geochemical analyses
ProgramMafic-Ultramafic Ore Systems, Targeted Geoscience Initiative (TGI-4)
LinksOGS OFR 6290 Online - En ligne (pdf, 204 MB)
AbstractThe Thunder intrusion is a mineralized mafic to ultramafic intrusion located on the outskirts of Thunder Bay, ON, which was explored by Rio Tinto (formerly Kennecott Canada Exploration Inc.) in 2005 and 2007 (Bidwell and Marino, 2007). Rio Tinto currently holds the mineral claims. The intrusion is interpreted to be associated with the early magmatic stages of the Midcontinent Rift (MCR) based on geochemical similarities to the mafic and ultramafic rocks of the Nipigon Embayment (Hollings et al. 2007). However, unlike other mineralized MCR intrusions, the Thunder intrusion has relatively low nickel tenor (< 0.08%) and a large range in PGE tenors (combined platinum-palladium values > 0.5 g/t; Bidwell and Marino 2007). The intrusion is also the only known mineralised MCR intrusion hosted within the Archean Shebandowan greenstone belt as all the others intrude the Mesoproterozoic Sibley Group and/or the Archean Quetico metasedimentary subprovince (Figure 57.1; Williams et al. 1991; Hart and McDonald 2007).
Summary(Plain Language Summary, not published)
This report highlights results from geological mapping of the Thunder intrusion with the inclusion of whole rock geochemistry. This is a MSc thesis study and collaborative project between the Geological Survey of Canada, the Ontario Geological Survey, and Lakehead University as part of the Ni-Cu-PGE-Cr project, Targeted Geoscience Initiative-4 (TGI-4; Ames et al., 2012). The main objective is to characterise the petrology, mineralization, and alteration footprint of the Thunder intrusion within the context of the MCR as a whole, in order to identify criteria for targeting buried mineralization.