Влияние кристаллизационной дифференциации на состав остаточного расплава для плагиоклаза при различных p-t условиях

Abstract

Crystallization differentiation processes in the melt volume for albite-anorthite solid solution series have been studied. For the albite-anorthite system, the change in the melt composition due to crystallization differentiation is calculated for pressure values P = 6,3 kbar and 1 bar and temperature T = 1410 °C, 1350 and 1300 °C. A calculation technique is presented for composition of the melt remaining after settling of plagioclase particles. The residual melt compositions have been calculated for different initial melt compositions and different P-T parameters. The change in composition due to crystallization differentiation of the melt is the difference in the percentage composition for each oxide on the liquidus line and the initial melt composition. The dimensionless ratios (similarity criteria) for the initial melt composition and the change of the oxide content , , , have been obtained. The change of each oxide percentage is calculated in weight percents and in the dimensionless form (as values of above-mentioned similarity criteria). The initial melt is depleted in different components. The depletion is due to settling of plagioclase particles and melt volume reduction. The latter is the sum of the solid particles and the melt volumes in the intercrystalline spaces of the settled particles’ layer. It is shown that the processes of crystallization differentiation are the sum total of hydrodynamic (geodynamic) and petrological processes. These processes can be studied using the methods of similarity theory. The compositional change in the melt due to crystallization differentiation can be represented in the form of an analytical relationship between the petrological similarity criteria