The Pleistocene volcanic activities in the Taradake volcanic area are divided into four stages older basalts (OB), older andesites (OA), younger basalts (YB) and younger andesites (YA). Basalts and calc-alkaline andesites as well as tholeiitic and alkaline basalts are erupted in close spatial and temporal proximity. The basalts (OB and YB) and the andesites (OA and YA) show distinct trends on the variation diagrams and ⁸⁷Sr/⁸⁶Sr ratios, suggesting that both have derived from different parental magmas. The relationship between the tholeiitic and the alkaline basalts in the YB stage can be explained by different degree of melting of the same source mantle.
     Incompatible element compositions of these basalts show within-plate type signature. The andesites appear to have derived from a high-magnesian andesite (HMA) magma that was generated in the upper mantle, because they have magnesian olivine phenocrysts coexisting in equilibrium with mantle peridotite and high-Cr spinels similar to those in the Setouchi HMAs.
      The HMA magma in the studied area may be produced by reaction between peridotite and ascending within-plate basalt magmas or by partial melting of hydrous peridotite induced during asthenospheric upwelling.

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Monte Calro simulations on the basis of the Potts model have been carried out to study normal grain growth in two dimensions. A microstructure of a polycrystalline aggregate can be represented by means of mapping onto a discrete lattice of which site is assigned an orientation number from 1 to Q. The following three lattice models were used in this simulation: triangular lattice (with first nearest neighbor site interactions), square lattice I (with first nearest neighbor site interactions) and square lattice II (with first and second nearest neighbor site interactions). The simulations were performed under constant temperature conditions (0≤T<T_c) quenched from an initial high temperature (T»T_c) state. Obtained microstructures are evolved keeping asimilar form of a grain boundary network. The microstructures produced especially on the triangular lattice model are in good correspondence with those in cross-sections of annealed metals and ceramics and with those of nearly monomineralic metamorphic rocks. These simulations show that the representing grain area linearly increases with time after an initial transient, which is independent of lattice model, temperature and total number of allowed grain orientation (Q). This means that the grain growth exponent value m is universally 2 and agrees with the various theories of normal grain growth. The grain size distribution function scaled by a representative size approaches a limiting form for Q≥256 region, in which grains of like orientation rarely impinge. Both the grain size distribution function and the grain growth rate are found to be inconsistent among the three lattice models for lower temperature simulations but the differences are reduced with increasing temperature.

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