Late Cretaceous igneous activities around southern Shiga Prefecture, southwest Japan: Insights from felsic ring dykes

Abstract

Distributions, modes of occurrence and geochronological data are summarized for the LateCretaceous ring-forming felsic and/or pyroclastic dykes, and their host granites around Lake Biwa, southwest Japan. The granitic plutons and ring dykes can be regarded to be genetically related from their petrological and geochemical characteristics. They are produced from a great felsic magma chamber, which is the source of igneous activities related to the formation of the assumed Biwako Cauldron. Recent geochronological studies, however, require the large revision of this cauldron model concerning the timescale of the pyroclastic activity and supposed huge magma chamber as its source.