Intermediate Members of the Oceanic Basalt-Trachyte Association

Abstract

The chemical characters of the lava members intermediate between mugearite and trachyte, trachybasalt and trachyte, in the oceanic basalt-trachyte association are reassessed in the light of researches recently reported (Chayes 1963). The several types of assemblages that fall within the limits of minimal frequency are recognized, and two assigned specific rank, the one more sodic — benmorite, the other more potassic — tristanite. Feldspathoidal variants may be associated with these near saturated type assemblages.