Abstract
The trace-element composition of rutile is commonly used to constrain P–T–t conditions for a wide range of metamorphic systems. However, recent studies have demonstrated the redistribution of trace elements in rutile via high-diffusivity pathways and dislocation-impurity associations related to the formation and evolution of microstructures. Here, we investigate trace-element migration in low-angle boundaries formed by dislocation creep in rutile within an omphacite vein of the Lago di Cignana unit (Western Alps, Italy). Zr-in-rutile thermometry and inclusions of quartz in rutile and of coesite in omphacite constrain the conditions of rutile deformation to around the prograde boundary from high pressure to ultra-high pressure (~2.7 GPa) at temperatures of 500–565°C. Crystal-plastic deformation of a large rutile grain results in low-angle boundaries that generate a total misorientation of ~25°. Dislocations constituting one of these low-angle boundaries are enriched in common and uncommon trace elements, including Fe and Ca, providing evidence for the diffusion and trapping of trace elements along the dislocation cores. The role of dislocation microstructures as fast-diffusion pathways must be evaluated when applying high-resolution analytical procedures as compositional disturbances might lead to erroneous interpretations for Ca and Fe. In contrast, our results indicate a trapping mechanism for Zr.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Journal of Metamorphic Geology |
| Vol/bind | 41 |
| Udgave nummer | 1 |
| Sider (fra-til) | 3-24 |
| Antal sider | 22 |
| ISSN | 0263-4929 |
| DOI | |
| Status | Udgivet - 2023 |
Bibliografisk note
Funding Information:Work was conducted within the Geoscience Atom Probe Facility at Curtin University and part of the Advanced Resource Characterisation Facility (ARCF). The ARCF, under the auspices of the National Resource Sciences Precinct (NRSP)—a collaboration between CSIRO, Curtin University and The University of Western Australia—is supported by the Science and Industry Endowment Fund (SIEF). The authors gratefully acknowledge support of Curtin University's Microscopy and Microanalysis Facility and the John de Laeter Centre, whose instrumentation has been supported by University, State and Commonwealth Government funding. H.W. v.S.L. and M. A. acknowledge funding received from the European Research Council under the European Union's Horizon 2020 research and innovation program grant agreement 714936 to M. Alvaro. S.M. Reddy and D.W. Saxey acknowledge funding through the Australian Research Council (DP210102625). Marco Scambelluri is acknowledged for valuable feedback on this work. We are grateful to Elias Bloch and Sandra Piazolo for thoughtful and in‐depth reviews that greatly improved the manuscript.
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© 2022 John Wiley & Sons Ltd.