Petrogenesis of Pyroclastic Deposits of the Vulsini VolcanicCenter, Italy

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In the Vulsini Volcanic complex in central Italy, mafic and felsic magmas have erupted with varying degrees of mixing. Despite the predominance of tephra in the Vulsini area, models of magmatic evolution at this center have been based almost entirely upon compositional variations among lava flows, and such sampling cannot avoid bias. Pumice clasts in tephra provide more representative samples of move voluminous magmas at the instant of eruptive fragmentation, and more adequately reflect the petrogenetically significant crustal components that are likely to be greatly undersampled if felsic tephra are ignored. This is an ongoing effort whose aim is to provide a petrogenetic model based on microprobe, major and trace element and isotopic analyses of crystals and glasses in an extensive suite of fresh pumice clasts from carefully studied pyroclastic units. This award is specifically to provide 60 neutron activation analyses. The results should advance understanding of the genesis of subsequent evolution of the mafic silica-undersaturated potassic magmas and the silica-oversaturated magmas, the processes by which the two magma types mixed, and the mechanisms of eruption of the resulting broad compositional range of magmas.