Vaterite after ikaite in carbonate sediment.

Abstract

At the calcareous sinter dome Shiowakka, Hokkaido, spherulitic vaterite was found in the carbonate sediments in early spring. The aggregates of ikaite formed in winter have changed to sandy carbonate sediments composed of calcite, vaterite, and monohydrocalcite with an increase of temperature. The foamy aggregates and zonal structure in the spherules of vaterite indicate that the crystallization has been derived from the rapid decomposition of ikaite and subsequent growth int the spring water.