“…(Schmincke et al 1995). The secondary mineral assemblage consisting of analcite, apophyllite, gmelinite, natrolite, phillipsite, prehnite, smectite (Lindblom and Gérard 1998), gobbinsite, heulandite, paulingite, mordenite, saponite, and montmorillonite (this study) are all characteristic for a low-grade zeolite facies metamorphism (Sevigny et al 1992;Neuhoff et al 1997). The precipitation of zeolites in inter-particle pore spaces represents a late stage in the alteration history because the prior formation of clay minerals causes a depletion of Mg and an increase of pH, which favors the growth of zeolites (Alt et al 1986).…”