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TitreParameterizations of calcic clinopyroxene - melt trace element partition coefficients
AuteurBédard, J H
SourceGeochemistry, Geophysics, Geosystems (G3) vol. 15, no. 2, 2014 p. 303-336, https://doi.org/10.1002/2013GC005112
Année2014
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130359
ÉditeurAmerican geophysical Union
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1002/2013GC005112
Mediapapier; en ligne; numérique
Formatspdf
Sujetspyroxene monoclinique; analyses des éléments en trace; géochimie des éléments en trace; éléments en trace; constantes du réseau; géochimie; minéralogie; pétrologie ignée et métamorphique
Illustrationstables; plots
ProgrammeMétaux communs - Île Victoria (T.N-O. et Nunavut), GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Semi-empirical parameterizations of the values and trends of variation of Nernst trace element partition coefficient data for Ca-rich clinopyroxene (cpx/liquidD) are provided, applicable mainly to common terrestrial magmatic suites. cpx/liquidD data for most trace elements show significant variability which cannot be neglected when modeling melting and crystallization. Compilation and interpretation of partitioning data show that the influence of pressure on cpx/liquidD is strong for many elements, particularly Na and Sr, which increase steadily as pressure rises, and most high-field strength elements, which decrease with increasing pressure. Most cpx/liquidD values increase as the temperature decreases, as wt% melt MgO, MgO# (MgO/MgO+FeOtotal), CaO and FeO contents drop, as cpx molar mg# (Mg/Mg+Fetotal) decreases, and as wt% melt SiO2 and Na2O+K2O increase. For some elements a diffuse positive correlation is seen with increasing cpx wollastonite content and melt Al2O3. No clear trends are seen for variations of cpx/liquidD against melt H2O. For mafic melts, many elements show well-defined trends of cpx/liquidD increase as the clinopyroxene tetrahedral Al-content (cpx Aliv) increases. Many cpx/liquidD are well correlated against cpx/liquidDTi, and many ¿near-neighbour¿ elements show good cpx/liquidD intercorrelations (e.g. Zr-Hf, U-Th, Nb-Ta, La-Ce, Yb-Lu). Cpx/liquidD profiles calculated from parameterizations against several input variables can be used to constrain the way D values change during melting or crystallization. Cpx/liquidD for the rare earth elements were fit to the lattice strain model to derive fits that closely reproduce the parabolic cpx/liquidDREE profile shapes (REE=rare earth elements). These fits indicate that cpx/liquidDHREE for melts more evolved than picritic basalts cannot be modeled assuming that all REE are in octahedral coordination in a single M2 site, but also require sixfold partitioning into an M1 site for Lu, Yb, Tm and Er.
Résumé(Résumé en langage clair et simple, non publié)
Les données expérimentales pour les coéfficients de partage entre le clinopyroxène et les magmas sont compilées et paramétrisées. Ces équations faciliteront les modélisations des éléments traces dans les roches ignés.
GEOSCAN ID293399