Fractional crystallization of magma

Albarede, F. (1976). Some trace element relationships amongst liquid and solid phases in the course of the fractional crystallization of magmas. Geochim. Cosmochim. Acta, 40,667-73. 

Crystal field theory was first applied to a geochemical problem in 1959 when R. J. P. Williams interpreted the relative enrichments of transition metal ions during fractional crystallization of magma in the Skaergaard intrusion (see 8.5). Williams (1959) was able to explain why Cr and Ni were removed from the magma during early crystallization of chromite and olivine,... 

Nockolds, S. R. (1966) The behaviour of some elements during fractional crystallization of magma. Geochim. Cosmochim. Acta, 30, 267-78. 

The chemical analyses of the Wyatt Formation in Appendix 7.8.1 demonstrate that the rocks have high silica concentrations ranging from 67.46% to 70.3%. Although the Wyatt Formation appears to be a deposit of volcanic ash that was extruded on the surface of the Earth, the pattern of decreasing concentrations of CaO + MgO, total Fe, and increasing Na O + K O with increasing silica concentration in Fig. 7.5 resembles the effects of fractional crystallization of magma. In addition, the pattern of variation of the chemical compositions of the Wyatt Formation in Fig. 7.5... 

Fig. 16.32 The Sr/ Sr ratios of the volcanic rocks of the Melbourne volcanic field are strongly correlated with the concentrations of SiO, MgO, and Na20 + K2O. Such correlations cannot form by fractional crystallization of magma in a closed system and, instead, indicate that the magma was contaminated either by assimilating rocks from the continental crust or by forming from mixed source rocks in the mantle. The colinearity of data points in Fig. 16.30 with mantle component EM2 favors contamination at the magma source in the mantle (Data from Worner et al. (1989))...

O Hara, M. J. (1977). Geochemical evolution during fractional crystallization of a periodically refilled magma chamber. Nature, 266, 503-7. 

In addition, the rocks of both formations are peraluminous because their molar ratios of AI2O3/ (K O + Na O + CaO) are greater than 1.0 in all samples analyzed by Stump et al. (1986). The silica-variation diagrams in Fig. 6.14 suggest that the concentrations of the major rock-forming elements were affected by fractional crystallization of the respective parent magmas. 

The concentrations of alkali metals, CaO, and MgO of the volcanic rocks that contain less than 48% SiO vary irregularly in Fig. 16.29 but the concentrations of these elements vary smoothly in rocks that contain more than 48% of SiO. The smooth patterns of variation in silica-rich rocks are consistent with fractional crystallization of the magma, whereas the irregular variations of silica-undersaturated rocks may reflect variations in the extent of partial melting of the magma sources. 

The chemical analyses of five dredge samples (Johnson et al. 1982) indicate that four of the analyzed samples are phonolites and one is mugearite (Campsie et al. 1983). The high concentrations of alkali metals (Na O + K O 8.83-13.11%) and of silica (SiO 50.93-58.76%) suggest that these rocks evolved by fractional crystallization of basanite magma (Wright and Kyle 1990b). 

The data for a plot like Fig. 18-60 are easily obtained from a screen analysis of the total crystal content of a known volume (e.g., a liter) of magma. The analysis is made with a closely spaced set of testing sieves, as discussed in Sec. 19, Table 19-6, the cumulative number of particles smaller than each sieve in the nest being plotted against the aperture dimension of that sieve. The fraction retained on each sieve is weighed, and the mass is converted to the equivalent number of particles by dividing by the calculated mass of a particle whose dimension is the arithmetic mean of the mesh sizes of the sieve on which it is retained and the sieve immediately above it. 

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