Petrogenetic modelling --- examples

In this section we illustrate the way in which trace element modelling has been used to idendfy differing petrogenetic processes in igneous rocks. 

Multivariate diagrams are used to compare calculated and measured rock compositions. Provided the composition of a parental melt is known, the composition of derivative liquids can be calculated and compared with the composition of liquids which are thought to have been derived from the parental melt. This is the approach used by Arth (1981), who modelled the REE chemistry of andesites and dadtes in New Britain by fractional crystallization from basaltic and basaltic andesites. Arth estimated the mineralogy of the fractionating assemblage from the proportions of phenocrysts present in the lavas and calculated REE patterns which show excellent agreement with the observed REE patterns in the rodcs. 

Crystal Komatiitic magmas are thought to have had exceptionally high Hquidus contamination temperatures and to have been frequently contaminated with continental crust. 

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