Most of the geologic characterization articles read that the basement rocks in most parts of the world are the plutonic rocks mainly granite and the metamorphic rocks. But, in some areas, especially in coastal aquifers, basalt basements are evident. So, can anyone explain it to me how the basalt basements could be created? In what situations could a basalt layer be underlying the granite and the other metamorphic rocks?
Thanks for your valuable contributions in advance!
By basalt basement I would guess it would have been the ocean floor when it formed. Alternatively, a basalt plateau from a long episode of extrusion of lava from a hot spot.
Later on granite can be intruded after subduction and in places it could overlie the basalt. For metamorphic rocks to lie on top that would mean that basalt is also metamorphosed. Alternatively, collision of continents could also bring older rocks (basalt) below younger ones (metamorphic).
Basaltic underplating of continental crust could also generate basalt 'basement' that underlies the silicic crust I'd guess....plenty of examples in the literature!
i found an article that maybe it can be useful for your question.
https://escholarship.org/uc/item/8nm9s2b3
please read this.
sincerely yours
In addition to the aforementioned comments you may also think of former back-arc basins that could be underlain either by thinned continental crust with strips of oceanic (basaltic) crust or completely by basaltic crust that may became intruded later on by granitic rocks. These former back-arc basins are potential candidates for sedimentary basins underlain by `basaltic basement´. If you research the literature for former back-arc basins you may find some examples.
Kind regards
Jens
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