Magma mixing

When magmas having different Sr/ Sr ratios and different strontium concentrations mix in differing proportions, the resulting mixtures define a hyperbola in 

Magma mixing also causes the isotope composition of strontium of the resulting mixtures to be correlated with the concentrations of other components such as SiO, MgO, and others depending on the chemical composition of the contaminant. Such correlations of isotopic and chemical parameters were first reported by Faure et al. (1972, 1974, 1982) for flows of the Kirkpatrick Basalt in the Transantarctic Mountains and of the Kirwan Volcanic s in Queen Maud Land (Chapter 14). 

The data of Bowman (1971) and Pace (1977) in Fig. 12.36 demonstrate that the initial Sr/ Sr ratios at 170 Ma of the Kirkpartick Basalt on Storm Peak and on Mt. Falla both rise with increasing concentrations of SiO.  

The correlation of these parameters is consistent with mixing of basalt magma with a silica-rich partial melt of crustal rocks with elevated Sr/ Sr ratios depending on their Rb/Sr ratio and age. A second example of this phenomenon in Fig. 12.37 demonstrates that the increase of the initial Sr/ Sr ratios at 170 Ma on Storm Peak with decreasing concentrations of MgO. The pattern of variation supports the hypothesis that the basalt magma mixed with a crustal melt that had a low concentration of MgO and a high Sr/ Sr ratio. Additional correlations of initial Sr/ Sr ratios and other major elements were reported by Faure et al. (1974) for the flows on Storm Peak analyzed by Bowman (1971). The positive correlation of initial Sr/ Sr ratios of the basalt flows on Solo Nunatak (Section 12.4.1.3) was described by Mensing et al. (1983). 

All of the evidence concerning the chemical and isotopic composition of the Tasmanian Dolerite and of the Kirkpatrick Basalt in the Transantarctic Mountains 

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The evolntionary history of the magma including processes of isotope exchange, assimilation of conntry rocks, magma mixing, etc... 

Decoupling of chemical and isotopic exchange during magma mixing. 

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