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Publication Type:

Journal Article


Precambrian Research, Volume 396, p.107169 (2023)






LASS-ICP-MS, Neoarchean tectonics, Sanukitoids, superior province, u-pb geochronology


<p>The metasedimentary subprovinces of the Superior Province provide critical insights into the tectonic style and thermal state prevailing during its Neoarchean cratonic assembly. The Pontiac subprovince consists of metamorphosed turbiditic sequences with minor interlayered mafic volcanic rocks that are intruded by abundant mafic to felsic plutonic rocks of different geochemical affinities, and for which the source, timing, deformation, and relationship to metamorphism and gold endowment are poorly constrained. Petrological, geochemical, isotopic (Lu-Hf zircon), and geochronological (U-Pb zircon and monazite) data reveal three plutonic events consisting of 1) c. 2764&nbsp;Ma medium-pressure TTG gneiss, interpreted as the local basement to the Pontiac supracrustal sequences; 2) syn- to late- sedimentary c. 2690–2670&nbsp;Ma juvenile (mean εiHf&nbsp;=&nbsp;4.02&nbsp;±&nbsp;1.12) monzonite sanukitoid and highly potassic calc-alkaline sills and plutons; and 3) voluminous c. 2670–2620&nbsp;Ma S-type granite sourced by protracted partial melting of sedimentary rocks at depth. This succession in the intrusive record combined with syn-depositional volcanism and subsequent Barrovian metamorphism of the metasedimentary host rock is consistent with a transition from a continental rift setting to crustal thickening via terrane assembly and challenges early models of arc accretion.</p>