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Lambart S., Laporte D., Provost A., Schiano Pierre. Fate of pyroxenite-derived melts in the peridotitic mantle : thermodynamic and experimental constraints. Journal of Petrology, 2012, 53 (3), p. 451-476. ISSN 0022-3530
doi:10.1093/petrology/egr068| Titre | Fate of pyroxenite-derived melts in the peridotitic mantle : thermodynamic and experimental constraints |
| Année de publication | 2012 |
| Type de document | Article référencé dans le Web of Science WOS:000300716800001 |
| Auteurs | Lambart S., Laporte D., Provost A., Schiano Pierre. |
| Source | Journal of Petrology, 2012, 53 (3), p. 451-476. ISSN 0022-3530 |
| Résumé | We performed a thermodynamic and experimental study to investigate the fate of pyroxenite-derived melts during their migration through the peridotitic mantle. We used a simplified model of interaction in which peridotite is impregnated by and then equilibrated with a finite amount of pyroxenite-derived liquid. We considered two pyroxenite compositions and three contexts of pyroxenitic melt impregnation: (1) in a subsolidus lithospheric mantle; (2) beneath a mid-ocean ridge (MOR) in a subsolidus asthenospheric mantle at high pressure; (3) beneath a MOR in a partially molten asthenospheric mantle. Calculations were performed with pMELTS at constant pressure and temperature with a melt-rock ratio varying in the range 0-1. Concurrently, a series of impregnation experiments was performed at 1 and 1 center dot 5 GPa to reproduce the final stages of the calculations where the melt-rock ratio is 1. Incoming melt and host-rocks react differently according to the melt composition and the physical state of the surrounding mantle. Whereas clinopyroxene (Cpx) is systematically a reaction product, the role of olivine (Ol) and orthopyroxene (Opx) depends on the incoming melt silica activity a(SiO2): if it is lower than the silica activity Such contrasted reactions between pyroxenitic melts and peridotitic mantle may generate a large range of new lithological heterogeneities (wehrlite, websterite, clinopyroxenite) in the upper mantle. Also, our study shows that the ability of pyroxenite-derived melts to migrate through the mantle depends on the melting degree of the surrounding peridotite. The reaction of these melts with a subsolidus mantle results in strong melt consumption (40-100%) and substantial Cpx production (with some spinel or garnet, depending on P). This is expected to drastically decrease the system permeability and the capacity of pyroxenite-derived melts to infiltrate neighbouring rocks. In contrast, melt migration to the surface should be possible if the surrounding mantle is partially melted; although liquid reactivity varies with composition, melt consumption is restricted to less than 20%. Hence, magma-rock interactions can have a significant impact on the dynamics of melting and magma migration and should not be neglected when modelling the partial melting of heterogeneous mantle. |
| Plan de classement | 066 |
| Localisation | Fonds IRD |
| Identifiant IRD | PAR00008575 |
| Lien permanent | http://www.documentation.ird.fr/hor/PAR00008575 |
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