Deciphering the metamorphic architecture and magmatic patterns of large hot orogens: Insights from the central Grenville Province

The Precambrian paleogeography of Laurentia

“…The Grenvillian orogeny was a protracted interval of continentcontinent collision (ca. 1.09 to 0.98 Ga) leading to amphibolite to granulite facies metamorphism throughout the orogen (Carr et al, 2000;Rivers, 2008Rivers, , 2012Indares, 2020). Note that while the terms Grenvillian orogeny and Grenville belt have been used rather loosely in the literature to refer to any late Mesoproterozoic orogenic belt, the timeline of orogenesis on the Laurentia margin has more nuanced constraints than this usage.…”

Ultrahigh-temperature granulite-facies metamorphism and exhumation of deep crust in a migmatite dome during late- to post-orogenic collapse and extension in the central Adirondack Highlands (New York, USA)

“…The inferred peak assemblage of plagioclase ± K-feldspar + quartz + garnet ± sillimanite + liquid + ilmenite ± rutile is stable from the solidus at amphibolite-facies conditions through UHT granulite-facies conditions, and so the peak P-T conditions cannot be inferred from the stable mineral assemblage alone. Overlaying isopleths for the grossular component of garnet from several samples should show peak P-T conditions where grossular isopleths intersect the peak mineral assemblage (Li et al, 2019;Indares, 2020). Calcium diffusion in garnet is much slower than that of Fe and Mg, resulting in little change from peak conditions, whereas the higher Fe and Mg diffusion rates probably capture retrograde conditions at the solidus (Chakraborty and Ganguly, 1992;Hollis et al, 2006;Li et al, 2019).…”

Crustal thickness of the Grenville orogen: A Mesoproterozoic Tibet?

“…The deepest-seat rocks crop out in the western Grenville in Ontario (Rivers et al, 2002), where eclogites along ABT yield early Ottowan (~1090 Ma; Marsh and Culshaw, 2014) metamorphic ages and underwent granulite-to amphibolite-facies overprinting. In contrast, the high-P counterpart in central Grenville was metamorphosed during mid-to late-Ottawan (Indares, 2020). The Adirondack Highlands and the Lowlands were both subject to intense metamorphism during the Shawinigan orogeny, but only the Adirondack Highlands were overprinted by high-grade Ottawan-age metamorphism.…”

“…In this section, we briefly review the geologic history and structure of the Grenville Province. Figure 11 in Hynes and Rivers (2010) is an excellent schematic tectonic cartoon, and Rivers (2015) provide a comprehensive review of the structural framework and litho-tectonic units with updated nomenclatures from the LITHOPROBE program.The amalgamation of Rodinia is reflected by a series of orogenic events in Laurentia: the accretionary Elzivirian orogeny (1245-1220 Ma), the arc-collisional Shawinigan orogeny (1190-1140 Ma), and finally the continent-continent collisional Grenville orogeny (1090-980 Ma) that is subdivided into Ottawan (1090-1020 Ma) and Rigolet (1015-980 Ma) stages (Rivers, 2012; Chiarenzelli et al, 2010;Indares, 2020). In older nomenclatures, Shawinigan was also a part of the Grenville cycle.…”

“…The amalgamation of Rodinia is reflected by a series of orogenic events in Laurentia: the accretionary Elzivirian orogeny (1245-1220 Ma), the arc-collisional Shawinigan orogeny (1190-1140 Ma), and finally the continent-continent collisional Grenville orogeny (1090-980 Ma) that is subdivided into Ottawan (1090-1020 Ma) and Rigolet (1015-980 Ma) stages (Rivers, 2012; Chiarenzelli et al, 2010;Indares, 2020). In older nomenclatures, Shawinigan was also a part of the Grenville cycle.…”