Topic > the evolution of the earth's crust - 2318

INTRODUCTION The formation of the earth's crust began during the Hadean eon, shortly after the Chaotian interval of core formation and solidification of the magma ocean (Allegre et al., 2008 ; Elkins-Tanton, 2008; Rudge et al., 2010). This process began with the differentiation of the crust-mantle zones from a large terrestrial silicate reservoir (BSE), which is also believed to have produced the first continuous terrestrial crust (Allegre et al., 2008). However, entire rock imprints of the original Hadean crust have not been preserved in the known geological record and can only be inferred by isotopic analyzes (Tessalina et al., 2010; Rizo et al., 2012). The only continuous trace of this primordial crust is found in rare detrital zircon grains within sandstone units (Jack Hills) of the Yilgarn craton in Western Australia (Compston and Pidgeon, 1986; Kemp et al., 2010). Extensive study has surrounded the Jack Hills zircon and has produced various geodynamic models for the early Earth, as well as controversial observations and interpretations (Valley et al., 2002; Harrison et al., 2008). For these reasons, the search for Late Archean igneous complexes has become of primary interest for understanding crustal evolution from within the Earth that would otherwise be unavailable for study (Smithies et al., 2005; Nebel et al., 2013). “Igneous Province” (LIP) was introduced to incorporate the range of recognized, immense, crustal emplacements of extrusive and intrusive mafic (Mg, Fe-rich) rock related to the decompression of the hot, molten, buoyant mantle rising from the Earth's interior (Coffin and Eldholm, 1991). This alteration of mass and energy is also thought to have occurred in specific cycles of geological time as opposed to the normal crust…mid-paper…mantle plumes, forming the first persistent oceanic lithosphere as observed in Nebel et al . (2013). This initial lithosphere may have been buoyant enough to form cratonic cores (Nebel et al., 2014). Subduction is believed to be an essential process in the formation of modern continental crust, however this model of early formation does not imply subduction or the pre-existence of continental crust. I conclude that crustal evolution was a gradual process that may have required only the melting of substantial mantle plumes and the formation of original crustal material, which agrees with the interpretations of Nebel et al. (2013), although opposed to new observations (i.e. Valley et al., 2014), suggest a much colder Hadean crust. Therefore future models of initial crustal formation will be developed by the presence of cooler (wetter) or warmer (drier) conditions at the Earth's surface.