As temperatures drop and differentiation proceeds, Na substitutes for Ca with coupled substitution of Si for Al to maintain charge balance.
Variations in composition within each series reflect differentiation in magma chambers under volcanoes.
total) atomic) which decreases during differentiation reflecting the preferential incorporation of Mg over Fe in ferromagnesian minerals.
1988), apatite comes on the liquidus by intermediate to late stages of differentiation in many suites as indicated by declining P concentrations (e.
Classic experiments by Yoder and Tilley in the 1960's showed that Ne-normative alkali basalts are probably not related to tholeiitic basalts by differentiation because of a low-pressure thermal divide approximately coinciding with the Ol--Ab join in the basalt tetrahedron (Fig.