Determinations of Si, Fe3+, Fe 2+, Na, and Kare reported for olivines and orthopyroxenes from Norwegian, Swiss, and South African gamet peridotites and related rocks, supplementing the results of O'HARA and MERCY (1963). A real departure from the ideal formulae is suspected in most of the orthopyroxenes, equivalent to the presence of from 0.5% to 4% olivine molecule in solid solution. These results are consistent with the deduction that the gamet peridotites have attained equilibrium at relatively low temperatures. The distribution of cations between coexisting clinopyroxene, orthopyroxene, and olivine is briefly discussed.
Olivines and orthopyroxenes from garnetiferous peridotites and related rocks