Serpentine Dehydration and the Mobility of Europium

Abstract

Two distinct styles of continental crust formation, correlative in time, have been identified in the literature (Taylor and McLennon, 1995). However, much is still unknown about the mechanisms for generating new continental crust and why they shifted in Earth history. Continental crust created after 2.6 Ga in subduction arcs displays a prominent negative europium anomaly compared to the element budget of its mantle source. Intra-crustal differentiation with subsequent delamination of a lower Eu-enriched eclogitic crust has been proposed as a mechanism for the Eu depletion observed in upper continental crust, but concerns related to rock mechanics in the rigid lithosphere have yet to be satisfactorily addressed. We hypothesize that the complementary Eu enrichment is to be found in the dehydration residue of subducting slabs, which offers a well-known mechanism for recycling fractionated material back into the underlying mantle.