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TitleEvidence of magmatism and rifting in the southern Superior Craton from the Temagami Geophysical Anomaly
AuthorAdetunji, A Q; Ferguson, I JORCID logo; Vayavur, R; Cheraghi, S; Naghizadeh, M; Whymark, W; Smith, R S; Ayer, J; Craven, J A
SourcePrecambrian Research vol. 362, 106310, 2021 p. 1-19,
Alt SeriesNatural Resources Canada, Contribution Series 20210231
Mediapaper; digital; on-line
File formatpdf; html
NTS41I/09; 41I/10; 41I/15; 41I/16
AreaSheppard Township; Afton Township; Mackelcan Township; McConnell Township; Rathbun Township
Lat/Long WENS -80.7000 -80.3000 47.0000 46.7000
Subjectstectonics; structural geology; geophysics; economic geology; Science and Technology; Nature and Environment; geological history; tectonic history; magmatism; intrusions; alteration; rifting; subsidence; depositional history; sedimentation; geophysical surveys; magnetotelluric surveys; magnetic surveys; gravity surveys; seismic reflection surveys; anomalies; bedrock geology; basement geology; structural features; lithology; sedimentary rocks; iron formations; igneous rocks; intrusive rocks; mafic intrusive rocks; ultramafic rocks; crustal structure; rifts; structural controls; anisotropy; mineral deposits; nickel; copper; ore mineral genesis; Archean; Paleoproterozoic; Temagami Geophysical Anomaly; Huronian Supergroup; Superior Craton; Temagami Greenstone Belt; Neoarchean; Huron-Nipissing Magmatic Belt; East Bull Lake Intrusive Suite; Sudbury Igneous Complex; Sudbury Structure; Gowganda Formation; Nipissing Diabase; Southern Province; Grenville Front; platinum group elements; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; geophysical profiles; 3-D models; schematic models
ProgramTargeted Geoscience Initiative (TGI-6) Digital Geoscience and Method Development Project
Released2021 07 12
AbstractThe Temagami Geophysical Anomaly (TGA) is situated in the Paleoproterozoic Huronian Supergroup near the southern margin of Archean Superior craton, along strike from the Temagami Greenstone Belt, 50 km northeast of world-class metal endowment in the Sudbury Igneous Complex. It has been attributed to coincidental geophysical responses from Neoarchean iron formation and a Paleoproterozoic mafic-ultramafic intrusion. The TGA is investigated using integrated magnetotelluric, magnetic, gravity and seismic reflection datasets to further define the geometry of its sources; to define structures in overlying Huronian Supergroup rocks; and to examine the geometrical relationship of Archean basement structure, the Proterozoic mafic-ultramafic intrusion, and Proterozoic rift structures.
Geophysical results reveal a strong conductor, interpreted to be iron formation, extending downwards from the Archean basement surface and enveloping the upper northern margin of a large magnetic, dense body at 5 km depth. The geometry of the features indicates mafic-ultramafic intrusion adjacent to greenstone rocks. Alignment of the long-axis of the intrusion with the greenstone belt suggests control on the intrusion process by the Neoarchean structures. The 60x10x10 km TGA intrusion lies within the mantle-plume, rift-related Huron-Nipissing magmatic belt and interpreted to be a member of the 2.491-2.475 Ga East Bull Lake intrusive suite. Based on this genetic relationship, the intrusion probably contributes significantly to Ni-Cu-PGE endowment of the Sudbury region. The spatial correlation of the intrusion with an overlying 20 km wide, 4.5 km deep, fault-bounded rift basin is attributed to crustal subsidence triggered by the intrusion. Seismic reflection and magnetotelluric results show younger Huronian Supergroup rocks record the transition to sedimentation on a laterally-extensive passive margin. An electrically-anisotropic, moderately-conductive layer in the Gowganda Formation is related to alteration during intrusion of the 2.200 Nipissing Diabase.
Summary(Plain Language Summary, not published)
The Temagami Geophysical Anomaly (TGA) near Sudbury ON is one of North America's largest, and also poorly understood, magnetic anomalies The TGA was investigated with magnetotelluric, gravity, magnetic, and seismic reflection methods to discern the origin of this feature. The TGA is shown to extend from ~3 km to 8 km depth and is magnetic, dense, with a northern margin that is electrically conductive. The main anomaly is interpreted to be caused by shallow crustal Archean banded iron formations above mafic-ultramafic intrusions deeper in the upper to middle crust. This research was conducted within the Targeted Geoscience Initiative program of NRCan in collaboration with the Metal Earth Project of the Mineral Exploration Research Centre of the Harquail School of Earth Sciences at Laurentian University.

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