Identification of Archaean plate tectonic processes from multidimensional discrimination diagrams and probability calculations

摘要

We applied our group's previously published multidimensional diagrams in 2006-2012 and corresponding probability estimates in 2011-2012 to geochemical data for Archaean rocks compiled from cratons in Australia, South Africa, Brazil, Canada, and India. Tectonic processes similar to present-day plate tectonics evidently were active at least since the Palaeoarchaean (~3570 Ma). This seems to be true in spite of a presumably hotter Earth at that time. For the eastern part of the Pilbara craton (Australia), a Palaeoarchaean (3570-3450 Ma) and Mesoarchaean (2900 Ma) continental arc setting apparently evolved to a collision (Col) setting during the Neoarchaean (2600 Ma). We infer an island arc (LA) environment for Kambalda (Australia) during the Neoarchaean (2700 Ma). For the Barberton belt (South Africa), a transition from a mid-ocean ridge regime during the older part of the Palaeoarchaean (3470 Ma) to an LA setting during the younger part (3300-3260 Ma) is likely. We inferred an arc environment for the Sao Francisco craton (Brazil) and the Rio Maria terrane (Brazil) during the Mesoarchaean (3085-2983 Ma and 2870 Ma, respectively), whereas a within-plate setting is clearly indicated for the Carajas metallogenic province (Brazil) during the Neoarchaean (2740-2700 Ma). We also recognize an IA regime for the Mesoarchaean (3000 Ma) North Caribou and Neoarchaean (2700 Ma) Abitibi greenstone belts (Canada), and for the Gadwal greenstone belt (Lndia) during the Neoarchaean (2700-2500 Ma). A Col setting was inferred for the Archaean sanukitoid suite (Canada) and the Kolar suture zone (India) during the Neoarchaean (2700-2660 Ma and 2630-2520 Ma, respectively).