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Mineral-melt vanadium oxybarometry for primitive arc magmas: effect of hydrous melt composition on fO2 estimates.
- Source :
-
Contributions to Mineralogy & Petrology . Apr2024, Vol. 179 Issue 4, p1-25. 25p. - Publication Year :
- 2024
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Abstract
- If primitive arc magmas are primarily oxidized or if they acquire their oxidizing character during crustal evolution remains debated. Mineral-melt V partitioning is extremely redox sensitive and has the potential to resolve this debate, but critical low-temperature, hydrous experimental partitioning data are limited. We present new experimental V partitioning data for olivine-melt, spinel-melt, and clinopyroxene-melt based on the ≤ 1200 °C, hydrous basalt phase equilibrium experiments of Pichavant et al. (Geochim Cosmochim Acta 66:2193–2209, 2002) and Pichavant and Macdonald (Contrib Mineral Petrol 154:535–558, 2007). Combined with published experimental data, we use our olivine-melt V partitioning coefficients to show that—contrary to previous conclusions—hydrous melt composition, i.e. melt H2O concentration in addition to the concentration of other melt components, affects V partitioning and thus calculated fO2, systematically overestimating fO2 for olivine-melt equilibrated at high melt H2O concentration. False absolute fO2 values and false oxidation or reduction trends may be inferred. Based on these findings, we have calibrated a set of new olivine-melt oxybarometers applicable to hydrous arc magmas partially crystallized at ~ 1025–1350 °C. In a case study on a high-Mg basalt from St. Vincent, Lesser Antilles, we show that olivine-melt V oxybarometry records oxidizing near-liquidus conditions (~ QFM + 1.8) and possibly limited oxidation (~ 0.3 log units) during intermittent crustal magma storage. [ABSTRACT FROM AUTHOR]
- Subjects :
- *HYDROUS
*MAGMAS
*PHASE equilibrium
*MELTING
*ABSOLUTE value
*ELECTRIC arc
*VANADIUM
Subjects
Details
- Language :
- English
- ISSN :
- 00107999
- Volume :
- 179
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Contributions to Mineralogy & Petrology
- Publication Type :
- Academic Journal
- Accession number :
- 176994699
- Full Text :
- https://doi.org/10.1007/s00410-024-02113-4