The role of pyroxenite in basalt genesis: Melt-PX, a melting parameterization for mantle pyroxenites between 0.9 and 5 GPa

• Published in: Journal of Geophysical Research: Solid Earth
• Main Authors: Lambart, Sarah, Baker, Michael B., Stolper, Edward M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2016
• Subjects: pyroxenite; heterogeneous mantle; parameterization; adiabatic decompression; Iceland
• Online Access: https://doi.org/10.1002/2015JB012762

Geochemical and isotopic data suggest that the source regions of oceanic basalts may contain pyroxenite in addition to peridotite. In order to incorporate the wide range of compositions and melting behaviors of pyroxenites into mantle melting models, we have developed a new parameterization, Melt-PX, which predicts near-solidus temperatures and extents of melting as a function of temperature and pressure for mantle pyroxenites. We used 183 high-pressure experiments (25 compositions; 0.9–5 GPa; 1150–1675°C) to constrain a model of melt fraction versus temperature from 5% melting up to the disappearance of clinopyroxene for pyroxenites as a function of pressure, temperature, and bulk composition. When applied to the global set of experimental data, our model reproduces the experimental F values with a standard error of estimate of 13% absolute; temperatures at which the pyroxenite is 5% molten are reproduced with a standard error of estimate of 30°C over a temperature range of ~500°C and a pressure range of ~4 GPa. In conjunction with parameterizations of peridotite melting, Melt-PX can be used to model the partial melting of multilithologic mantle sources—including the effects of varying the composition and the modal proportion of pyroxenite in such source regions. Examples of such applications include calculations of isentropic decompression melting of a mixed peridotite + pyroxenite mantle; these show that although the potential temperature of the upwelling mantle plays an important role in defining the extent of magma production, the composition and mass fraction of the pyroxenite also exert strong controls. © 2016 The Authors. Issue online: 15 September 2016; Version of record online: 18 August 2016; Accepted manuscript online: 16 July 2016; Manuscript Accepted: 14 July 2016; Manuscript Revised: 29 June 2016; Manuscript Received: 19 December 2015. This study has benefited from discussions with Paula Antoshechkin, Eric Brown, and Oliver Shorttle (who also read and commented on portions of ...