Method for the identification of the K-Tz tephra based on a detailed comparison of major elements within glass inclusions in tephra quartz

Akira Furusawa, Chisato Nakamura
2009 Chishitsugaku zasshi  
In strongly weathered tephras, it is commonly the case that only quartz and opaque minerals remain unaltered. For example, the K-Tz tephra is distinguished by abundant quartz crystals. The identification of strongly weathered tephras is difficult because majorelement analyses of volcanic glass are affected by weathering. Here, we propose a method of identifying weathered tephras based on major-element analyses of pristine glass inclusions preserved in quartz phenocrysts, and apply the method to
more » ... identifying the K-Tz, Nr-N, and Kt-tephras. We used energy-dispersive X-ray EDX techniques to analyze samples of the K-Tz tephra collected from a proximal location Tanegashima, near Kikai caldera and from three distal locations. The major-element compositions of glass inclusions are similar in all the K-Tz samples, but are distinct from those of the Nr-N and Kttephras. Major-element analysis of quartz-hosted glass inclusions is a promising method in investigations of strongly weathered Quaternary tephras in Japan, such as K-Tz. CThe Geological Society of Japan 2009 544
doi:10.5575/geosoc.115.544 fatcat:wamt4u7tpzcoxny7vfhq7urqdq