Differentiation index

Mount Belknap and Red Hills calderas and associated rocks, Marysvale volcanic field, west-central Utah

“…The uniform lithology of these members ( (Thornton and Thttle, 1960), low anorthite content, normative composition of the magma forming these alkali rhyolite tuffs, and the evidence for volatile saturation, permit them to be treated as the quaternary system Q-Or-Ab-H 2 0. Thttle and Bowen (1958) have shown that in this system the composition of the ternary minimum varies as a function of water pressure.…”