Petrogenesis of mafic lavas from the northernmost sector of the Iblean district (Sicily)

XRF results are given for a wide variety of mafic volcanic rocks, ranging from quartz tholeiites to strongly undersaturated alkaline lavas (ankaratrites), erupted during the Upper Miocene and Plio-Pleistocene in this area of E Sicily. Modelling of the data for both major and trace elements indicates that these near-primary melts cannot have been produced by different degrees of melting from the same source; this would suggest that their differences reflect, at least in part, significant variations in source composition. Calculations suggest that suitable mantle sources are represented by variously 'enriched' spinel lherzolites, containing accessory phases such as amphibole for tholeiitic and transitional basalts, amphibole + phlogopite for alkaline lavas, and amphibole + phogopite + or - apatite + or - carbonate for highly alkaline rocks. The rocks of the Iblean area may thus have been produced by different degrees of partial melting of a lithospheric mantle, ranging from 2-3 % for highly alkaline rocks to 22 % for quartz tholeiites.