Neodymium isotope disequilibria in subducted sediments, and potential consequences for subduction-zone recycling

Spandler, Carl, Hammerli, Johannes, and Pirard, Cassian (2018) Neodymium isotope disequilibria in subducted sediments, and potential consequences for subduction-zone recycling. Geology, 46 (9). pp. 815-818.

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Abstract

Neodymium isotope geochemistry is pivotal to understanding magma genesis and crustal recycling processes at convergent plate margins. Here, we present Nd isotope compositions of rare earth element (REE)–rich minerals from blueschist- to eclogite-facies rocks that represent previously subducted continental sediments. We find Nd isotope heterogeneity in all of our samples. Apatite preserves diverse detrital isotopic compositions despite metamorphism up to at least 600 °C and 3.0 GPa, whereas lawsonite appears to be isotopically homogenous. Epidote and monazite are major REE hosts under eclogite-facies conditions; in our samples these phases also retain Nd isotope heterogeneity, even up to ultrahigh-pressure conditions of 700 °C and 4.0 GPa. These findings contest the assumption of Nd isotope equilibration during subduction-zone metamorphism, so caution is needed when using Nd isotopes to calculate subducted sediment contributions to arc magmas or for determining rates of crustal recycling through subduction zones.

Item ID: 55568
Item Type: Article (Research - C1)
ISSN: 1943-2682
Copyright Information: © 2018 Geological Society of America
Funders: Australian Research Council (ARC)
Projects and Grants: ARC grant DP1095280, ARC grant FT120100198
Date Deposited: 12 Sep 2018 08:52
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
04 EARTH SCIENCES > 0403 Geology > 040313 Tectonics @ 50%
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