Metamorphism in Neoarchean Granite-Greenstone Belts: Insights from the Link between Elu and Hope Bay Belts (∼2.7 Ga), Northeastern Slave Craton

Origin, Accretion, and Reworking of Continents

“…As shown in Figure 4a, the metamorphic evolution of Neoarchean terranes in the NCC, no matter whether they are low-grade granite-greenstone belts or high-grade gneiss terranes, is dominated by anticlockwise P-T paths mostly involving isobaric cooling (IBC). Similar anticlockwise P-T paths have also reported in other Archean cratons, such as the Kaapvaal craton (Figure 4b; Kamber et al, 1996;Kramers et al, 2001;Rollinson, 1989;Tsunogae et al, 1992), Superior craton (Figure 4c; Percival, 1994), East Antarctica (Figure 4d); Sandiford, 1985;Tsunogae et al, 1999;Zulbati & Harley, 2007), Wyoming craton (Maas & Henry, 2002), Slave craton (Mvondo et al, 2017), and Southern India craton (Raith et al, 1990(Raith et al, , 1999. The IBC-type anticlockwise P-T paths generally reflect metamorphism related to the intrusion and underplating of large voluminous mantle-derived magmas.…”

“…(5) Anticlockwise P-T paths involving isobaric cooling reconstructed for many Archean cratons. Available data show that the metamorphic evolution of Archean rocks from many Archean cratons is characterized by anticlockwise P-T paths involving isobaric cooling (Ge et al, 2003;Halpin & Reid, 2016;Jayananda et al, 2000;Kamber et al, 1996;Kramers et al, 2001;Maas & Henry, 2002;Mvondo et al, 2017;Percival, 1994;Raith et al, 1990Raith et al, , 1999Rollinson, 1989;Sandiford, 1985;Tsunogae et al, 1992Tsunogae et al, , 1999Zhao et al, 1998Zhao et al, , 2001Zhao et al, , 2005Zulbati & Harley, 2007), though clockwise P-T paths were also reported for kyanite-bearing assemblages in Archean greenstone belts (Collins & Van Kranendonk, 1997). There is a broad consensus that anticlockwise P-T paths involving isobaric cooling reflect the metamorphism related to the intrusion and underplating of large amounts of mantle-derived magmas (Bohlen, 1991).…”

“…The metamorphism of Archean cratons is generally characterized by (a) large-scale regional metamorphism, in contrast with Proterozoic and Phanerozoic metamorphism that is limited largely to linear structural belts (orogens); (b) low-to medium-pressure greenschist facies, amphibolite facies, and granulite facies metamorphism that happened at a normal geothermal gradient range (10-30 °C/km); (c) absence of high-pressure blueschist facies and high-pressure or ultrahigh-pressure eclogite facies metamorphism; and (d) metamorphic P-T paths dominated by anticlockwise type involving isobaric cooling (Ge et al, 2003;Halpin & Reid, 2016;Jayananda et al, 2000;Kamber et al, 1996;Kramers et al, 2001;Maas & Henry, 2002;Mvondo et al, 2017;Percival, 1994;Raith et al, 1990Raith et al, , 1999Rollinson, 1989;Sandiford, 1985;Tsunogae et al, 1992Tsunogae et al, , 1999Zhao et al, 1998Zhao et al, , 2001Zhao et al, , 2005Zulbati & Harley, 2007). Some clockwise P-T paths were also reported for a few Archean terranes, but they were all post-3.0 Ga in metamorphic age (e.g., Hölttä & Paavola, 2000;Taylor et al, 2010;Valli et al, 2004), supporting the idea that modern-style plate tectonics had not been operative until ∼3.0 Ga (Gamal El Dien et al, 2020) since clockwise P-T paths and especially those involving isothermal decompression are generally considered to reflect initial crustal thickening by subduction followed by rapid exhumation.…”