Publication Date:
2022-05-25
Description:
Author Posting. © Springer, 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Contributions to Mineralogy and Petrology 156 (2008): 87-102, doi:10.1007/s00410-007-0275-8.
Description:
The grain-scale processes of peridotite melting were examined at 1340°C and 1.5
GPa using reaction couples formed by juxtaposing pre-synthesized clinopyroxenite against
pre-synthesized orthopyroxenite or harzburgite in graphite and platinum-lined molybdenum
capsules. Reaction between the clinopyroxene and orthopyroxene-rich aggregates produces a
melt-enriched, orthopyroxene-free, olivine + clinopyroxene reactive boundary layer. Major
and trace element abundance in clinopyroxene vary systematically across the reactive
boundary layer with compositional trends similar to the published clinopyroxene core-to-rim
compositional variations in the bulk lherzolite partial melting studies conducted at similar P–
T conditions. The growth of the reactive boundary layer takes place at the expense of the
orthopyroxenite or harzburgite and is consistent with grain-scale processes that involve
dissolution, precipitation, reprecipitation, and diffusive exchange between the interstitial melt
and surrounding crystals. An important consequence of dissolution–reprecipitation during
crystal melt interaction is the dramatic decrease in diffusive reequilibration time between
coexisting minerals and melt. This effect is especially important for high charged, slow
diffusing cations during peridotite melting and melt-rock reaction. Apparent clinopyroxenemelt
partition coefficients for REE, Sr, Y, Ti, and Zr, measured from reprecipitated
clinopyroxene and coexisting melt in the reactive boundary layer, approach their equilibrium
values reported in the literature. Disequilibrium melting models based on volume diffusion
in solid limited mechanism are likely to significantly underestimate the rates at which major
and trace elements in residual minerals reequilibrate with their surrounding melt.
Description:
This work was supported by NSF grants EAR-0208141
and EAR-0510606 to Yan Liang.
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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