Abstract
Mineralogical and geochemical studies carried out on intrafault materials collected at two outcrops of the Atotsugawa fault of Central Japan, which had been described in detail in the previous paper. A sample of the intrafault materials was divided into four fractions of 2μ>, 2-74μ 74-250μ and 250μ< by their grain size. Mineralogy and geochemical compositions were examined in each fraction of the sample. The three fractions of 2μ< have almost similar mineralogy and geochemical compositions. Mineralogically, the 2μ>fraction is including more amount of montmorillonite, illite and chlorite and on the contrary less amount of quartz, feldspar and calcite than the other three fractions. The geochemical compositions of the 2μ< fraction is rich in Al2O3, MgO, K2O and total H2O and poor in SiO2, CaO, Na2O and CO2, comparing with those of the other three fractions. It is disclosed that the mineralogy, geochemical compositions and grain size of the intrafault materials have close relationship one another and should be related to the formation process of the materials and the degree of their weathering or alteration.
