Burial metamorphic rocks from Fiji

Abstract

Abstract Burial metamorphism has produced many secondary minerals in Tertiary volcanic and sedimentary rocks from western Viti Levu, Fiji. Secondary assemblages include: albite-epidote—chlorite—sphene, albite—sericite—chlorite—prehnite—pumpdlyite—quartz, mordenite(?)—quartz—celadonite, and chabazite with a phyllosilicate and any two of thomsonite, phillipsite, and analcime. The primary fabrics of the host rocks are usually unchanged. Mineralogical modification may have resulted from burial alone, or from a combination of burial and a regional elevation of temperature connected with Tertiary volcanism. Some samples of chabazite give an X-ray powder pattern with additional lines in the position of the strongest reflections of phillipsite. Only a single phase is optically identifiable in each case.