Sovite and alvikite: two chemically distinct calciocarbonatites C1 and C2

This contribution (i) chemically distinguishes the two carbonatites: sovite and alvikite, and (ii) presents new 'average' (median) compositions for th em. The best and most used average chemical composition for calciocarbonati te is that calculated by Woolley and Kempe in 1989, and it is shown here th at this composition comprises two distinctively different compositions corr esponding to those of sovite and alvikite. Sovite and alvikite are the coar se-grained and the medium- to fine-grained varieties, respectively, of calc ite-carbonatite. It is proposed that the corresponding calciocarbonatites s hould be termed C1 calciocarbonatites and C2 calciocarbonatites, based on t heir chemical compositions. The distinction of the two lies, not in the maj or elements, but in the minor, trace- and rare-earth-element contents. Usin g a comprehensive database of post-1970 analytical data, the 'average' comp ositions for C1 and C2 calciocarbonatites have been calculated. Instead of the arithmetical average, the arithmetical median has been calculated for e ach, since this gives truer estimates of the two compositions. It is believ ed that the two median compositions will enable C1 End C2 calciocarbonatite s to be recognized.