Classificazione modale delle vulcaniti del Monte Vulture.

The Vulture rocks pose numerous classification problems when using conventional chemical diagram, which are often inconsistent with the modal mineral content of the rocks. Notably, the Total alkali Silica adopted by USGS diagram does not allow any distinction among Vulture rocks, which spread on it. R1-R2 De La Roche's diagram better discriminantes three main groups which are significant in term of volcanic cycles but, again, it is not suitable for classification. A method of classification, based on modal quantitative SEM analyses of lavas and macro-crystalline structure has been applied to the Monte Vulture volcanic suite of lavas and pyroclastics. Contrary to what defined into the previous literature, most of the Vulture rocks do not contain essential plagioclase and thus, term such as basalt or K-basalt or even, basanite and tephrite, should be avoided. Most of these rocks are foiditic phonolites with xenocrystics olivine. Melilitites plot, according to the silica and CO2 content, in the foiditic to ultramafic field.