Reply to “Paleo- to Mesoarchean polymetamorphism in the Barberton granite-greenstone belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt: Discussion” by M. Brown

Were modern-type subduction-accretion–like processes already operative in the Archean, or did a hotter Archean Earth with consequently weaker lithosphere prevent this and favor gravitationally driven vertical tectonics? Brown’s comment on Cutts et al. (2014) weighs in on this central controversy around the likely geodynamic environments that prevailed in the Archean Earth, and he focuses on the Barberton granite-greenstone belt as one of the type localities of Archean crustal processes in the world. In the Barberton granite-greenstone belt, 3.55–3.45 Ga trondhjemite gneisses and associated high-pressure amphibolite-facies metamafic and metasedimentary rocks are structurally juxtaposed against lower-greenschist-facies rocks of the Onverwacht Group (...