Earth's oldest stable crust in the Pilbara Craton formed by cyclic gravitational overturns

Hf-Nd Isotopes in Archean Marine Chemical Sediments: Implications for the Geodynamical History of Early Earth and Its Impact on Earliest Marine Habitats

“…These studies confirmed a shift in the trace element composition of weathered uppermost continental crust from (ultra)mafic to more felsic at 2.7 Ga. Furthermore, Wiemer et al [13] showed that dense (ultra)mafic stacks and underlying felsic proto-continental crust in the ca. 3.4 Ga old Pilbara Craton was reorganized via gravitation overturns, allowing felsic continental crust to reach the uppermost continental levels and be available for subaerial weathering and erosion processes.…”

“…Applying this novel geochemical proxy to Archean samples opens the unique opportunity to not only trace weathering and erosion processes of the earliest uppermost continents, but also indirectly unravels the geodynamical evolution of Archean continents and the combined nutrient fluxes into the earliest marine habitats on Earth. Archean continental crust is predominantly mafic to ultramafic in composition and the uppermost continental levels consist of stacked basaltic lithologies and oceanic plateaus with abundant TTGs in middle to lower crustal levels that have episodically been brought to the uppermost continental levels via gravitational overturns [1,13]. Hence, Archean continents were predominantly submerged and the uppermost continental crust was mostly covered by oceans and not available for subaerial weathering and erosion processes [5].…”

“…These findings in combination have major implications on the geodynamical evolution of the Archean continents and, of course, on the nutrient flux derived from the continents into the earliest marine habitats on Earth. However, clastic sediments in worldwide-distributed greenstone belt successions, e.g., [10][11][12], indicate that at least parts of more evolved continental crust were already subaerial weathered and eroded during the Meso-and Paleoarchean, potentially uplifted by gravitational overturn of felsic proto-crust [13]. The urgent scientific questions remain to which amount and when evolved continental crust was available for chemical weathering and erosion processes to affect Archean seawater chemistry and the coincident flux of (bio)available nutrients into the earliest marine habitats on Earth.…”

Generation of Earth's Early Continents From a Relatively Cool Archean Mantle

“…Together, these observations are consistent with a tectonic setting mainly dominated by vertical tectonics, periodically fuelled by magmas derived from anomalously hot mantle sources, such as plumes (Fischer & Gerya, ; Van Kranendonk, ). In such a scenario, continental crust would be produced via intracrustal melting and differentiation and dense mafic residua would be continuously removed via Rayleigh‐Taylor instabilities (RTIs; Wiemer et al, ). Owing to the higher T P , the RTIs would induce decompression melting of the asthenosphere, which would add heat to further assist continued TTG magma generation (Bédard, ).…”

A Review of Paleo- to Neoarchean crustal evolution in the Dharwar craton, Southern India and the transition towards a Plate Tectonic regime

“…On the other hand, the role of vertical (autochthonous) tectonics in granite-greenstone terranes, driven by processes such as sagduction or partial convective overturn have been advocated from several locations based on structural fabrics and shear sense indicators. These dome and keel structures relate to ascent of granitoid domes and coeval development of supracrustal synclines, due to gravity driven Rayleigh-Taylor type instabilities (RTI) (Mareschal and West, 1980;Hickman, 1984;Bouhallier et al, 1993Bouhallier et al, , 1995Choukroune et al, 1995;Chardon et al, 1996Chardon et al, , 1998Collins et al, 1998;Thebaud and Rey, 2013;Van Kranendonk et al, 2007Wiemer et al, 2018).…”