Trace element partitioning and oxygen isotope fractionation between minerals in eclogites of the Münchberg Massif (Germany)
Pohlner JE, El Korh A, Rubatto D, Pettke T, Klemd R, Grobéty B (2026)
Publication Type: Journal article
Publication year: 2026
Journal
Book Volume: 534-535
Article Number: 108545
DOI: 10.1016/j.lithos.2026.108545
Abstract
Oxygen isotopes and trace elements are important geochemical proxies in subduction zone research. However, their interpretation is challenging, also due to their dependence on the extent of inter-mineral equilibration and retrogression. We measured the mineral chemical and oxygen isotopic composition of eclogites of the Münchberg Massif and assessed the degree of equilibrium. Evaluation of literature P - T data and new oxygen isotope and Zr-in-rutile temperatures suggest that the rock matrix equilibrated at 2.5 ± 0.5 GPa and 700 ± 50 °C, though peak pressures may have been higher. Textural relationships, homogeneity of all minerals except for garnet in major and most trace elements, and a good agreement between measured and predicted mineral oxygen isotope compositions (except for rutile) provide evidence that a high degree of equilibrium was attained and preserved. Still, kinetic barriers largely preserved prograde equilibrium (continuous zoning of many major and trace elements in garnet) and disequilibrium features (major phases with heterogeneously distributed Y, heavy rare-earth elements, and Cr). Small δ18O variations within individual garnet crystals (0.6 ± 0.3 to 1.8 ± 0.4‰) argue against significant influx of externally-derived fluids during garnet growth. Careful evaluation of equilibrium permits to constrain partition coefficients for a range of selected trace elements between garnet, omphacite, amphibole, zoisite, kyanite, and phengite, for most of which experimental and natural data are scarce. Many partition coefficients vary systematically by up to one order of magnitude as a function of garnet, omphacite and/or amphibole major element composition, whereas most Ge partition coefficients are remarkably insensitive to major element systematics. These partitioning data offer new perspectives on element (re-)distribution in subducted eclogite-facies rocks.
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APA:
Pohlner, J.E., El Korh, A., Rubatto, D., Pettke, T., Klemd, R., & Grobéty, B. (2026). Trace element partitioning and oxygen isotope fractionation between minerals in eclogites of the Münchberg Massif (Germany). Lithos, 534-535. https://doi.org/10.1016/j.lithos.2026.108545
MLA:
Pohlner, Johannes E., et al. "Trace element partitioning and oxygen isotope fractionation between minerals in eclogites of the Münchberg Massif (Germany)." Lithos 534-535 (2026).
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