GeologyRocksEarth's crust
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First crust (oceanic) is I'd
Thu, 03/15/2007 - 21:01Differentiation of Earth is early - absolutely first crust probably ultrabasic mantle composition.
First crust proper (oceanic) is I'd have thought likely to be basaltic from partial melt of mantle at mid-ocean ridges. First continental crust likely to be andesitic from partial melt of subducted oceanic lithosphere.
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You could consider two
Mon, 04/09/2007 - 07:44You could consider two episodes of geochemical differenciation (first and second).
The first one, was related with the cooling of the molten Earth during and after accrection process of Earth´s formation.
The second one due to parcial melting and/or fractionated differenciation processes during the Archean >2.5Gy. For instance: transition from TTG (tonalite-trondhjemite-granodiorite) to felsic granitoids.
Recently I read a book where you can learn more about that:
Kent C. Condie (2005): Earth as an Evolving Planetary System. Elsevier Academic Press.
Salud
Javi
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Earth's crust
Submitted by simonc8788 on Thu, 03/15/2007 - 13:51.Does anyone know what the (likely) composition of the first crust to form would be? I know there are no igneous (or sedimentary) rocks that old, but can we tell from the metamorphic rocks what the original crust were likely to be composed of? Am I right in thinking that the Earth was not internally fractionated at this time?