Contamination by Crustal Rocks

Interaction between magma and wall rocks has been a common process in the Roman Province. However, the core problem is the question of how much this interaction has modified the pristine compositional characteristics of the mafic parent magmas. A particularly important issue is whether the crustal-like geochemical and isotopic signatures of Roman mafic vol-canics can be explained solely by some form of crustal assimilation. These problems have been discussed at length not only for the Roman Province but for all the potassic volcanoes occurring across the Italian peninsula and in the Aeolian arc. 

1 Mg-number = Mg/(Mg+Fe2+) atomic ratio calculated assuming a Fe3+/Fe2+ 0.85. Mg of mantle-equilibrated melts is around 0.7 (Frey et al. 1978). 

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Explain how magma was transported in the subsurface while showing little evidence of contamination by crustal rocks (e.g., they contain few if any crustal xenoliths). 

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