Redox Melting of Garnet Lherzolite: Generation of Carbonated Silicate and Sulfide Melts and Implications for OIB Formation From Chalcophile and Redox‐Sensitive Elements
Abstract Upwellings in the Earth's mantle become sufficiently oxidizing for CO2‐induced redox melting at depths equivalent to ∼8–5 GPa, generating deep incipient mantle melts. This study simulates the geochemistry of the redox melting process by conducting multi‐anvil experiments at 5 GPa and s...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2025-03-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2024GC012025 |
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| Summary: | Abstract Upwellings in the Earth's mantle become sufficiently oxidizing for CO2‐induced redox melting at depths equivalent to ∼8–5 GPa, generating deep incipient mantle melts. This study simulates the geochemistry of the redox melting process by conducting multi‐anvil experiments at 5 GPa and slightly superadiabatic 1,450°C. By stepwise increasing the oxygen content in a graphite‐ and sulfide‐saturated bulk silicate Earth (BSE)‐like composition, sulfide and carbonated silicate melts were produced and coexist with garnet ± olivine ± orthopyroxene ± clinopyroxene. Carbonated silicate melts contain 31–38 wt.% SiO2, 9–17 wt.% CO2, 270–475 ppm S and have an XMg of 0.75–0.77; the sulfide melts have molar metal/(S + O) and Ni/(Fe + Ni) ratios of 1.08–1.23 and 0.59–0.69, respectively. The experiments were doped with chalcophile and/or redox‐sensitive trace elements to derive mineral/carbonated silicate melt/sulfide melt partition coefficients. Sulfide melt/carbonated silicate melt partition coefficients are lithophile for Ga, P, V, Mn, Ge, Cr, Zn and In increasing in this sequence from 0.005 to 0.9, and chalcophile for Cd, Mo, Sn, Tl, Pb, Co, Sb, As, Ni, Bi, Se and Te, increasing from 3 to ∼6000. We use our data to model trace element concentrations in incipient redox melts and apply our results to ocean island basalt (OIB) genesis. Our redox melting model suggests that average concentrations of most trace elements in primitive and Si‐undersaturated OIBs can be well explained by 1%–2% melting of sulfide‐saturated depleted mantle mixed with 10–20 wt.% of recycled oceanic crust that includes minor sediment when retaining some sulfide melt in the source. |
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| ISSN: | 1525-2027 |