Before the onset of modern style plate tectonics and the Wilson cycles in the late Archean, it is thought that smaller units of continental crust, called cratons, roamed the oceanic crust over a more vigorously convecting mantle. These cratons already show structures that suggest that they collided and accreted back in the day. Also, it is assumed that by the end of the Archean, 70% of today's crust had already been formed, though probably not at greater depths, and with a significant change around the time tectonics kicked in.

The Wikipedia article suggests 3 formation processes, but the cite link is broken.

1) surface crust was thickened by a rising plume of deep molten material, 2) successive subducting plates of oceanic lithosphere became lodged beneath a proto-craton in an under-plating process, 3) accretion from island arcs or continental fragments rafting together to thicken into a craton

My questions would be: Would uplift by a rising plume or underplating lift the originally basaltic material high enough for erosion to kick in and produce felsic/silicate/continental sediments, pre 2.5Gy ? Was the basement already solid enough to support the weight of mountains ? If i am not mistaken, todays exposed metamorphic old shields underwent low pressure metamorphosis of already felsic material. What do we know about the emplacement of the sediments from which they formed ?

I can easily split into several questions, no question.

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    $\begingroup$ I've had some classes on this, but I'm not confident enough to answer... You should have a look at the literature on tonalite-trondhjemite-granodiorite genesis, as they are a major component of Archean cratons. There are several hypothesis on their genesis, like plume underplating or Bédard's delamination: doi.org/10.1016/j.gca.2005.11.008 $\endgroup$ Jan 6, 2020 at 16:18
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    $\begingroup$ You're welcome. I also remember that Kerguelen's plateau is considered by some a modern analogue of a continental crust nucleus, a proto-craton if you like. I couldn't find a paper relevant to this, but this one seems to conclude the opposite for Iceland... doi.org/10.1111/j.1365-3121.2008.00839.x $\endgroup$ Jan 7, 2020 at 12:49
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    $\begingroup$ News that offer a simplified, almost unified approach to generation of early continental crust: nature.com/articles/s41561-019-0520-6. $\endgroup$
    – user18607
    Jan 14, 2020 at 16:25
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    $\begingroup$ Nice study, thanks for sharing! I still see a little "chicken and egg" issue: they explain how to form TTGs by intracrustal differentiation... which means that to produce continental crust, you need some (mafic) crust in the first place! :D $\endgroup$ Jan 14, 2020 at 16:50
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    $\begingroup$ Impact melting and weathering as hypothetical contributions to early continental crust ? researchportal.port.ac.uk/portal/files/1357984/… $\endgroup$
    – user18607
    Jan 24, 2020 at 10:54


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