Rare-Earth distributions in some rocks and associated minerals of the batholith of southern California

The rare-earth and yttrium abundances in four whole-rock samples and eight associated mineral fractions from the batholith of southern California have been determined by means of neutron activation and partition chromatography. It is shown that, on a whole-rock basis, an increase in total rare-earth content in the sequence gabbro-tonalite-grandiorite-quartz monzonite is paralleled by an increase in relative fractionation favoring the lighter rare earths. In the same sequence, there is an apparently systematic, increased relative removal of Eu which is attributed to the existence of Eu(II). Analyses of feldspar, pyroxene, amphibole, mica, and apatite mineral fractions also indicate that divalent Eu was an important constituent during the evolution of the rocks studied. The feldspar mineral fractions were invariably enriched in Eu relative to the adjacent rare earths, whereas the ferromagnesian minerals were relatively depleted.