Journal of Petrology, Volume 39, Issue 02: February 1 1998.
Bulk-rock concentrations of included elements, such as Ni, Cr, and V, decline in a normal fashion from the lowest levels of the Skaergaard Layered Series to the Sandwich Horizon, but their distributions are highly irregular. Only a small part of the scattered bulk-rock abundances of these elements can be attributed to varied proportions of the minerals in which these elements tend to be concentrated; by far the greatest part results from the different concentrations in the individual minerals, even at the same stratigraphic horizon. An inventory of included trace elements in rocks at a given level shows little correlation between bulk-rock concentrations and modal proportions of mafic minerals. For example, rocks with little olivine but abundant pyroxene or oxides have about the same Ni contents as those with much more olivine. As a result, the Ni contents of individual minerals differ from one sample to the next and have no apparent relationship to the crystal-liquid partition coefficients for conventional magmatic compositions and conditions. The bulk-rock concentrations and internal partitioning between minerals appear to be a function of the mobilities of the individual elements and the degree to which they have been altered by subsequent metasomatic changes of the mineral assemblage and major-element compositions. The results show that one cannot safely use magmatic partition coefficients and trace-element compositions of minerals to deduce the compositions of liquids from which coarse-grained mafic rocks crystallized.
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