Zeolite minerals in the Tuluanshan Formation of the Coast Range, eastern Taiwan

Two zeolite assemblages, natrolite-analcime and clinoptilolite-stellerite, occurring in the Tuluanshan Formation of the Coastal Range were identified with the techniques of X-ray diffraction, atomic absorption spectroscopy and electron probe analyses. The natrolite-analcime assemblage was found in association with basaltic rocks in the Wu-shi-pi area near Changping; while the clinoptilolite-stellerite assemblage was discovered in the andesite near the Fu=Li area. The establishment of the identity for clinoptilolite is primarily based on the crystal structure characteristics rather than the chemical composition criterion.
The two zeolite assemblages examined in this study are believed to be the products of the post-volcanic activity connected to the Tulanshan Formation in the Coastal Range. The low value of Si/Al ratio (2.0) in the analcime zeolite indicates that the analcime crystals were probably formed through the interaction of the post-volcanic hydrothermal solution with the host basaltic rocks. The presence of the clinoptilolite-stellerite assemblage and the absence of phillipsite in the Fu-Li zeolite zone suggest that the temperature of formation of the zeolites in this area was extremely low, probably lower than 150°C.