Geology and geochemistry of Hadean zircon-bearing supracrustals from Quad Creek, eastern Beartooth Mountains, Montana, USA

Quad Creek Paleoarchean quartzites (∼3300 Ma) in southern Montana contain >3900 Ma detrital zircons. Although an accessible resource for investigating Hadean (>3850 Ma) crust distinct from the well-known Narryer Gneisses in Australia and Acasta Gneisses in Canada, the outcrop-scale geological and geochemical context of these rocks is not well documented. New mapping reveals a varied suite of isoclinally folded, sheared and variably deformed chromiterich banded and massive quartzites, garnet-bearing siliceous paragneisses, amphibolite, quartzbiotite schists and a suite of inter-bedded quartz+magnetite rocks (banded iron-formation, BIF). Conventional ion microprobe U-Pb zircon ages of different populations from these units show neoform growth or outgrowth rims on inherited detrital igneous cores at ∼3350 Ma, ∼2900 and later (<2500 Ma) that match those for regional metamorphic events evidenced elsewhere in the Wyoming Craton. Weighted mean 207Pb/206 Pb ages for the youngest concordant igneous zircon cores indicate that the maximum age of deposition for the supracrustals is ∼3300 Ma. These data support the notion that the oldest crust tapped by the Quad Creek quartzites is comparable in age to the ca. 3960 Ma Acasta Gneiss Complex. This similarity is suggestive of a linkage between the geology of the Wyoming Craton and the Western Slave Province. An ancient supercraton called Sclavia could provide the mechanism for this linkage. Sediment source(s) for some other Paleoarchean supracrustals were also contaminated by Hadean crust suggests that pre-3900 Ma zircons are present in similarly-aged basins elsewhere in North America and perhaps also remnants of Sclavia. The Slave and Wyoming craton may be the modern components of a 'Slave clan' which contains the remnants of Sclavia.