Beaudette, Mélanie; Ross, Pierre-Simon 
ORCID: https://orcid.org/0000-0002-5302-698X et Davis, Donald W.
(2024).
No longer an arc: The Parent Group, a newly recognized component of the 1.88 Ga Circum-Superior large igneous province, Quebec, Canada.
Precambrian Research
, vol. 403
.
p. 107310.
DOI: 10.1016/j.precamres.2024.107310.
Résumé
In northernmost Quebec (Canada), the 1.88 Ga Circum-Superior large igneous province is traditionally thought to be represented only by the Chukotat Group –renowned for its Ni-Cu-Co-PGE ore deposits – within the Southern Domain of the Cape Smith Belt (Ungava Orogen). The Parent Group, just to the north, in the Northern Domain of the Cape Smith Belt, is commonly interpreted as a younger volcanic arc related to subduction, after a phase of continental to oceanic rifting which produced the Southern Domain. But the Parent Group is poorly known, poorly dated, and its origin remains unclear. This study improves the volcanic, stratigraphic, petrological, geochronological and tectonic understanding of the Parent Group. The Parent Group in the mapped area is dominated by mafic to intermediate volcanic rocks, with a small component of dacite. The mafic to intermediate rocks contain two thirds lavas (mostly sheet lavas, with minor pillowed flows) and one third volcaniclastic rocks. Volcanism was subaqueous, as shown by pillow lavas, hyaloclastites, volcaniclastic turbidites, and interbedded mudstone and iron formation. The trace elements patterns of the tholeiitic and of some transitional affinity rocks of the Parent Group resemble those of modern MORBs, suggesting seafloor spreading. In contrast, trace elements in calc-alkaline and other transitional rocks share similarities with modern volcanic arcs. MORB-like and arc-like rocks are intimately interbedded in the volcanic sequence. The arc signature might be related to contamination of the mantle-derived, MORB-like magmas by continental crust of the Superior Province. New U-Pb dating of the Parent Group shows that it fits within the 1883–1881 Ma peak magmatism for the Circum-Superior large igneous province. Although the Chukotat Group to the south is, on average, more primitive and perhaps less contaminated than the Parent Group, the Chukotat Group shares many geochemical similarities. They might both be related to a mantle plume impacting the Superior Craton, with mafic to ultramafic magmatism concentrated at the thinner craton margins.
| Type de document: | Article |
|---|---|
| Mots-clés libres: | proterozoic greenstone belts; Cape Smith belt; Circum-Superior large igneous province; crustal contamination |
| Centre: | Centre Eau Terre Environnement |
| Date de dépôt: | 31 juill. 2024 20:14 |
| Dernière modification: | 31 juill. 2024 20:14 |
| URI: | https://espace.inrs.ca/id/eprint/15493 |
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