Yep! It's pretty rare and we're still not *quite* sure how - we suspect it's what happens when you try to subduct very young (i.e. hot) oceanic plates. Keyword is "ophiolite"; there's some all around the world, including breathtakingly beautiful exposures in Oman that more or less let you walk through mountains that are beautiful vertical cross-sections of the structure of the mantle :-) I mean, obviously it's weird mantle, in that not much of it gets shoved up on top of continental crust, but!
(Less excitingly, at some ultra-slow-spreading mid-ocean ridges, the mantle gets drawn up slowly enough that it can dissipate sufficient heat that it never melts so you don't form basalts. The South-West Indian Ridge is a good example of this.)
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regna
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Date: 2014-04-22 11:31 pm (UTC)(Less excitingly, at some ultra-slow-spreading mid-ocean ridges, the mantle gets drawn up slowly enough that it can dissipate sufficient heat that it never melts so you don't form basalts. The South-West Indian Ridge is a good example of this.)