A Simple Thermodynamic Model for Melting of Peridotite in the System NCFMASOCr
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Authors
Jennings, Eleanor S
Holland, Tim
Publication Date
2015-05-25Journal Title
Journal of Petrology
ISSN
0022-3530
Publisher
Oxford Journals
Volume
56
Number
5
Pages
869-892
Language
English
Type
Article
Metadata
Show full item recordCitation
Jennings, E. S., & Holland, T. (2015). A Simple Thermodynamic Model for Melting of Peridotite in the System NCFMASOCr. Journal of Petrology, 56 (5), 869-892. https://doi.org/10.1093/petrology/egv020
Abstract
A new thermodynamic model is presented for calculating phase relations in peridotite, from 0 001
to 60 kbar and from 800 C to liquidus temperatures, in the system NCFMASOCr. This model system
is large enough to simulate phase relations and melting of natural peridotite and basaltic liquids.
Calculations in the program THERMOCALC illustrate mantle phase relationships and melting conditions,
specifically for the peridotite composition KLB-1. The garnet–spinel transition zone intersects
the solidus at 21 4–21 7 kbar, where both Fe3þ and Cr increase spinel stability, expanding the width
of the transition. Orthopyroxene is lost at the solidus at 42 kbar in KLB-1, although this pressure is
very sensitive to bulk composition. Calculated oxidation states are in excellent agreement with
measured log fO2 for xenolith suites with mantle Fe2O3 contents in the range 0 1–0 3wt %. It
appears that mantle oxidation state is not just a simple function of P and T, but depends on phase
assemblage, and may vary in a complex way within a single assemblage. The liquid model
performs well, such that calculated solidus, melt productivity and liquid compositions compare
favourably with those of experimental studies, permitting its use in interpolating between, and
extrapolating from, experimental P–T conditions. Experimentally challenging but geologically
useful regimes can be explored, such as subsolidus samples and very low melt fractions, with
application to both mantle xenoliths and the origin of basalt.
Keywords
basalt, mantle, partial melting, peridotite, thermodynamics
Sponsorship
This work was supported by a Natural Environment
Research Council studentship [NE/J500070/1] to E.S.J.
and Natural Environment Research Council grant [NE/
J021539/1] to T.J.B.H.
Funder references
NERC (NE/J021539/1)
Identifiers
External DOI: https://doi.org/10.1093/petrology/egv020
This record's URL: https://www.repository.cam.ac.uk/handle/1810/248084
Rights
Attribution 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by/2.0/uk/
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