An allivalitic orbicular inclusion found in the Neogene basalt flow consists of coarse crystals of anorthite (An 95±1) with small amount of iddingsite crystals. It shows a concentric structure, due to alternate zones with different iddingsite contents (Fig. 2, B). In the core (a) small grains of anorthite similar to the core of phenocrystic anorthite of the host rock in composition, twin type, and features of inclusion (Fig. 2, H), are poikilitically enclosed in the iddingsite. The outer zones (b_??_f) are made up of radial aggregates of wedge-shaped anorthite finely twinned after albite-and pericline laws, and contain small iddingsite crystals (Fig. 2, E, F).
抄録全体を表示