Reworking subducted sediments in arc magmas and the isotopic diversity of the continental crust: The case of the Ordovician Famatinian crustal section, Argentina

CORNET, J.; ANTONELLI, M.A.; BACHMANN, O.; WOTZLAW, J.-F.; BERGANTZ, G.W.; LAURENT, O.; OTAMENDI, J.

EARTH AND PLANETARY SCIENCE LETTERS

ELSEVIER SCIENCE BV

Año: 2022 vol. 595 p. 1 - 13

0012-821X

Since the onset of plate tectonics,continents have evolved through a balance between crustal growth, reworking,and recycling at convergent plate margins. The term “reworking” involvesre-insertion of crustal material into pre-existing crustal volumes, whilecrustal growth and recycling respectively represent gains from and losses tothe mantle. Reworking that occurs in the mantle wedge (“source” contaminationfrom slab material) or within the upper plate (“path” contamination), will havecontrasting effects on crustal evolution. However, due to limited access todeep crustal and mantle rocks, quantifying source vs. path contaminationremains challenging. Based on the 4-dimensional record of the fossil(Ordovician) Famatinian continental arc (Argentina), we demonstrate thatsource contamination plays a dominant role in imprinting mafic to graniticrocks with crustal oxygen-hafnium (O-Hf) isotopic compositions. We argue thatsource contamination at convergent plate margins significantly increased thediversity of O-Hf isotopic signatures of continents over geologic time. Ourinterpretation implies that crustal evolution models attributing this isotopicdiversity dominantly to intra-crustal reworking may be over-simplistic andmayunderestimate continental growth in the last 2.5 billion years.