ИСТИНА

The crystallization of water-saturated andesite melt (andesite from Shiveluch volcano, Kamchatka) was studied at PH2O = 3Kbar and temperature oscillating (3 cycles) in the ranges 980-960°C and 995-985°C with period about 30 min. The growth of clinopyroxene proceeded continuously in the whole runs time. Rhythmically zoned crystals of clinopyroxenewith size 40-100 μm were produced. The number of zones is comparable with the number of cycles. We calculated the growth rate based on the zones width and the half-period of the oscillations. The growth rate for the different zones was in the range 0.8-1.8*10-6 cm/sec. Temperature dependence of the growth rate corresponds to the Tl of Cpx of 1025-1030°C. The initial undercooling for CPx crystallization was in the range 25-60°C and was gradually approaching zero in the hot half-periods