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Extreme reduction: Mantle-derived oxide xenoliths from a hydrogen-rich environment
- Source :
- Lithos, Lithos, Elsevier, 2020, 358-359, pp.105404. ⟨10.1016/j.lithos.2020.105404⟩
- Publication Year :
- 2020
- Publisher :
- HAL CCSD, 2020.
-
Abstract
- International audience; Coarse-grained xenoliths of hibonite + grossite + Mg-Al-V spinel from Cretaceous pyroclastic rocks on Mt. Carmel, N. Israel, and from Sierra de Comechingones, Argentina, include spherules, rods and dense branching structures of native vanadium and VAl alloys. Microstructures suggest that vanadium melts became immiscible with the host Ca-Al-Mg-Si-O melt, and nucleated as droplets on the surfaces of the oxide phases, principally hibonite. Many extended outward as rods or branching structures as the host oxide crystal grew. The stability of V0 implies oxygen fugacities ≥9 log units below the Iron-Wustite buffer, suggesting a hydrogen-dominated atmosphere. This is supported by wt%-levels of hydrogen in gasses released by crushing, by Raman spectroscopy, and by the presence of VH2 among the vanadium balls. The oxide assemblage formed at 1400–1200 °C; the solution of hydrogen in the metal could lower the melting point of vanadium to these temperatures. These assemblages probably resulted from reaction between differentiated mafic melts and mantle-derived CH4 + H2 fluids near the crust-mantle boundary, and they record the most reducing magmatic conditions yet documented on Earth.
- Subjects :
- 010504 meteorology & atmospheric sciences
Hydrogen
Geochemistry
Oxide
[SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography
chemistry.chemical_element
Vanadium
Immiscible melts
engineering.material
010502 geochemistry & geophysics
01 natural sciences
Mantle (geology)
chemistry.chemical_compound
Geochemistry and Petrology
Mantle xenoliths
Native vanadium
Mantle-derived hydrogen
0105 earth and related environmental sciences
Mantle-derived methane
Spinel
Geology
Grossite
chemistry
Chemical engineering
13. Climate action
Super-reducing conditions
engineering
Hibonite
Mafic
Subjects
Details
- Language :
- English
- ISSN :
- 00244937
- Database :
- OpenAIRE
- Journal :
- Lithos, Lithos, Elsevier, 2020, 358-359, pp.105404. ⟨10.1016/j.lithos.2020.105404⟩
- Accession number :
- edsair.doi.dedup.....42966efcf7987f53d40b0fdd94882c3f