Plate tectonics in relation to mantle temperatures and metamorphic properties

Abstract

When plate tectonics emerged and how it has evolved over Earth history are two of the most fundamental challenges in Earth Sciences. These questions are tackled using a holistic approach to analyze tectonic styles in the history of Earth, giving rise to the interpretation of two styles of plate tectonics since the Archean. In these interpretations, there are different styles of deformation and metamorphism between early times dominated by warm subduction, and later times preferring cold subduction. The two styles of plate tectonics are recorded by different properties of regional metamorphism at convergent plate boundaries, which are linked to the differences in mantle temperature between the Archean and Phanerozoic. A transition to modern plate tectonics is recorded by the signature of blueschist facies metamorphism developed in the Neoproterozoic. This is consistent with geological evidence for the operation of ancient plate tectonics since the early Archean. The temporal cooling of the mantle explains the geochemical trends of mantle-derived melts, the likely change from numerous small plates to fewer but larger plates, changes in thickness and preservation of oceanic crust and lithosphere in accretionary and collisional orogens, and led to the oxygenation of the surface environment providing the environments needed to foster life.