Journal article

Mineral activity-composition relations and petrological calculations involving cation equipartition in multisite minerals: a logical inconsistency

TJB Holland, R Powell

JOURNAL OF METAMORPHIC GEOLOGY | WILEY | Published : 2006

Abstract

Equipartition is an assumption that preserves the same relative fraction of the cations on each site, originally used just to distribute cations such as Fe and Mg over two or more sites during mineral recalculation. This approximation has been used in almost all thermometry and barometry applications in petrology involving pyroxene, amphibole, chlorite and biotite mica. It has also become the default approach used in deriving activity-composition relations in multisite minerals where details of element partitioning among the sites is unknown and therefore assumed to be random. It is shown that, where a third element, such as Al, resides on just one of the sites, equipartition introduces a se..

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