Madeleine Stow madeleine.a.stow@durham.ac.uk
Academic Visitor
Integrated Petrological and Fe-Zn Isotopic Modelling of Plutonic Differentiation
Stow, Madeleine A.; Prytulak, Julie; Humphreys, Madeleine C.S.; Nowell, Geoffrey M.
Authors
Professor Julie Prytulak julie.prytulak@durham.ac.uk
Professor
Professor Madeleine Humphreys madeleine.humphreys@durham.ac.uk
Professor
Dr Geoffrey Nowell g.m.nowell@durham.ac.uk
Associate Professor
Abstract
The upper continental crust is formed from chemically diverse granitic plutons. Active debate surrounds the range of physical conditions (P-T-X-fO2) and differentiation processes which occur in mush bodies that solidify to form plutons. Transition metal stable isotopes are increasingly employed to trace magmatic processes in both extrusive lavas and intrusive plutonic suites, with a focus on analysis of whole rock powders. However, studies of plutonic suites often overlook the complex textures represented within coarse grained samples, and how these will influence whole rock isotopic compositions. Here we examine the calc-alkaline Boggy Plain Zoned Pluton, SE Australia, which closely approximates closed system behaviour during magmatic differentiation. We combine petrological examination with Fe and Zn isotopic analysis of biotite, hornblende and magnetite mineral separates and whole rock powders. Whole rock Fe isotopic composition (as δ56Fe) increases from 0.038‰ to 0.171‰ with decreasing MgO content, while mineral separates display heavy Fe isotope enrichment in the order magnetite > biotite = hornblende > pyroxene. A lack of correlation between whole rock Fe and Zn isotopic compositions suggests that the Fe isotopic variation is predominantly driven by closed system fractional crystallisation: specifically by the balance between crystallisation of isotopically heavy magnetite, and isotopically light silicates. To demonstrate this quantitatively, temperature dependent mineral-melt fractionation factors were derived from the mineral separate data (Δ56Femag-melt = 0.17x106/T2 and Δ56Febt/hbd-melt = -0.12x106/T2) and used to construct models that successfully reproduce the observed Fe isotopic variation during fractional crystallisation. These fractionation factors are compared to theoretical and empirical estimates from previous studies. We highlight that accurate determinations of temperature and modal mineralogy are critical when modelling Fe isotopic variations in plutonic suites. Successful interpretation of equilibrium Fe isotopic fractionation in a relatively simple calc-alkaline suite like the Boggy Plain Zoned Pluton paves the way for Fe isotopes to be used to investigate more complex mush bodies.
Citation
Stow, M. A., Prytulak, J., Humphreys, M. C., & Nowell, G. M. (2022). Integrated Petrological and Fe-Zn Isotopic Modelling of Plutonic Differentiation. Geochimica et Cosmochimica Acta, 320, 366-391. https://doi.org/10.1016/j.gca.2021.12.018
Journal Article Type | Article |
---|---|
Acceptance Date | Dec 17, 2021 |
Online Publication Date | Dec 23, 2021 |
Publication Date | Mar 1, 2022 |
Deposit Date | Jan 10, 2022 |
Publicly Available Date | Jan 10, 2022 |
Journal | Geochimica et Cosmochimica Acta |
Print ISSN | 0016-7037 |
Electronic ISSN | 1872-9533 |
Publisher | Meteoritical Society |
Peer Reviewed | Peer Reviewed |
Volume | 320 |
Pages | 366-391 |
DOI | https://doi.org/10.1016/j.gca.2021.12.018 |
Public URL | https://durham-repository.worktribe.com/output/1217699 |
Files
Published Journal Article
(4.9 Mb)
PDF
Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/
Journal Article ((In Press, Journal Pre-Proof))
(3.6 Mb)
PDF
Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/
Copyright Statement
(In Press, Journal Pre-Proof) © 2021 The Author(s). Published by Elsevier Ltd.
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
You might also like
No V-Fe-Zn isotopic variation in basalts from the 2021 Fagradalsfjall eruption
(2023)
Journal Article
Rhenium Isotopes Record Oxidative Weathering Intensity in Sedimentary Rocks
(2024)
Journal Article
Downloadable Citations
About Durham Research Online (DRO)
Administrator e-mail: dro.admin@durham.ac.uk
This application uses the following open-source libraries:
SheetJS Community Edition
Apache License Version 2.0 (http://www.apache.org/licenses/)
PDF.js
Apache License Version 2.0 (http://www.apache.org/licenses/)
Font Awesome
SIL OFL 1.1 (http://scripts.sil.org/OFL)
MIT License (http://opensource.org/licenses/mit-license.html)
CC BY 3.0 ( http://creativecommons.org/licenses/by/3.0/)
Powered by Worktribe © 2024
Advanced Search