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Ascent Dynamics of Low Degree Mantle Partial Melts, Constrained from CO2 Solubility Experiments.

Abstract : Low degree partial melting of carbonated mantle peridotite generates strongly silica-undersaturated melts containing substantial amount of carbon dioxide (several tens of wt%). Kimberlite melts are one of these volatile-rich mantle product and are believed to ascent through the upper mantle and crust at great speed (~5 to 50 ms-1). The role of volatiles in propelling this ascent has remained poorly quantified due to experimental difficulties in quenching such compositions to a glass. In this study, we used a range of melt compositions in the Si-C-Al-Ca-Mg-Fe-Na-K-O system addressing the chemical complexity needed to closely mimic kimberlitic to carbonatitic characteristics. These melts can, furthermore, be quenched fast enough to produce a glass and be used to determine the CO2 solubility as a function of composition and pressure. Our results suggest that the solubility of CO2 decreases steadily with increasing amount of network forming cations from ~30 wt% CO2 at 12 wt% SiO2 down to ~3 wt% CO2 at 40 wt% SiO2 and that pressure has limited effect on the solubility of CO2 up until very shallow depth (~ last 3 km). This peculiar pressure-solubility relation in kimberlite melt can explain the highly explosive nature of kimberlite magma and characteristic geo-morphological features of their root zone. We present a general CO2 solubility model based on thermodynamic formalism covering a large range of melt composition from 11 to 53 wt% SiO2 spanning the transition from carbonatitic to basaltic melts at pressures up to 1500 MPa.
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https://hal-insu.archives-ouvertes.fr/insu-01163378
Contributor : Nathalie Pothier <>
Submitted on : Friday, June 12, 2015 - 4:42:46 PM
Last modification on : Tuesday, October 6, 2020 - 11:40:05 AM

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Yves Moussallam, Yann Morizet, Malcolm Massuyeau, Fabrice Gaillard. Ascent Dynamics of Low Degree Mantle Partial Melts, Constrained from CO2 Solubility Experiments.. AGU Fall Meeting, AGU, Dec 2014, San Francisco, United States. pp.V12A-01. ⟨insu-01163378⟩

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