A REE pattern as observed in an intra oceanic tonalite (plagiogranite) such that flatter and low HREE, similar to the primitive mantle with no Eu anomaly. Under what conditions such REE pattern can be achieved? The Hf-O isotope composition of these TTG rocks strongly suggests depleted mantle. Can such a REE pattern be achieved by shallow partial melting of amphibolite underplate?
Suggestions?
Can you be more specific. First, where is the plagiogranite? Is it in an ophiolite? Second, is it LREE depleted.?
These are the near-trench Early Cretaceous (123 Ma) tonalite-trondhjemite plutons in southern Alaska emplaced in the arc-forearc setting. I attached two figures for you.
There is a lot of variation in the REE patterns, but most don't really look like MORB. This suggests multiple sources, consistent with melting in a complex forearc basement.
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