Bulletin Volcanologique

, Volume 33, Issue 3, pp 942–959

Origin of rhyolites by anatectic melting of granitic crustal rocks

The example of rhyolitic pumice from the island of kos (agean sea)
  • J. Keller

DOI: 10.1007/BF02596758

Cite this article as:
Keller, J. Bull Volcanol (1969) 33: 942. doi:10.1007/BF02596758


Rhyolitic pumice deposits on some East Aegean Islands are the remnants of a tuff sheet which covered formerly more than 2500 km2. The rhyolites originated by melting of granitic crustal rocks.

The petrological properties leading to this conclusion are as follows:
  • -mineralogical composition of the pumice being 60 wt % of glass and 40 % of relictic granitic minerals (quartz, plagioclase, potash feldspar, biotite) in «phenocrysts» up to 1 cm Ø.

  • -phenomena of strong corrosion, resorption and melting of all light colored «phenocrysts» in the rhyolitic pumice.

  • -mineralogical and chemical identity between pumice and granitic xenolites found in great quantity in the pumice tuff.

  • -structurally transitional types between pumice and the granites in different state of melting.

  • -eutectic composition of the pumice glass for a pressure of 2 kb.

Copyright information

© Stabilimento Tipografico Francesco Giannini & Figli 1969

Authors and Affiliations

  • J. Keller
    • 1
  1. 1.Mineralogisches Institut der UniversitätFreiburgW-Germany