Short-term episodicity of Archaean plate tectonics

Abstract

By combining geochemical data and geodynamical models, evidence is provided to address the existence and style of Archaean plate tectonics, a topic of vigorous debate for decades. Using careful analyses of lithostratigraphic Archaean assemblages and numerical model results, we illustrate that a short-term episodic style of subduction was a viable style of tectonics in the early Earth. Modeling results show how, due to the low strength of slabs in a hotter Earth, frequent slab break-off events prevented a modern-style long-lived subduction system, and resulted in frequent cessation and re-initiation of the subduction process on a typical time scale of a few million years. Results fit with geochemical observations that suggest frequent alternation of arc-style and non-arc-style volcanism on a similarly short time scale. Such tectonics could provide the link between early pre-plate tectonic style of tectonics (or stagnant-lid convection) and modern-style plate tectonics, in which short-term episodes of proto-subduction evolved over time into a longer-term, more successful style of plate tectonics as mantle temperature decayed.

Regimes of subduction and lithospheric dynamics in the Precambrian: 3D thermomechanical modelling

“…11d) suggests that slab break-off could occur for longer model runtime. This has already been observed by van Hunen and van den Berg (2008) and Moyen and van Hunen (2012).…”

“…Van Hunen and van den Berg (2008) and Moyen and van Hunen (2012) found what can be called 'episodic subduction' as they observed multiple slab break-off under similar conditions. We therefore suggest that our observed dripping subduction regime could correspond to episodic subduction at its early stage.…”

The Majorqaq Belt: A record of Neoarchaean orogenesis during final assembly of the North Atlantic Craton, southern West Greenland

“…Condie and Benn, 2006;Garde et al, 2000;Nutman and Friend, 2007, Nutman et al, in press;Van Kranendonk, 2010). There is a growing consensus that lateral accretionary processes began in the Mesoarchaean (Brown, 2007;Moyen and van Hunen, 2012;Naeraa et al, 2012;Shirey and Richardson, 2011;Tappe et al, 2011), though early subduction may have been intermittent with frequent slab-breakoff, potentially causing the observed bimodal style of supra-subduction calc-alkaline and plume-generated komatiite volcanism (Dziggel et al, 2014;Kamber, 2015;Moyen and van Hunen, 2012;Wyman et al, 2002). Petrologic evidence for early subduction-driven continental thickening includes high-pressure mafic and pelitic amphibolites in the Barberton terrain, Pilbara, and Salem crustal block (Anderson…”

The Neoarchean ultramafic–mafic complex in the Yinshan Block, North China Craton: Magmatic monitor of development of Archean lithospheric mantle

“…The slab breakoff commonly occurred in the terminal stage of subduction owing to gravitational settling (Wortel and Spakman, 2000;Pe-Piper et al, 2009;Moyen and Van Hunen, 2012). The broken slab would also terminate associated continental arc magmatism (Chung et al, 2005).…”