Geochemistry and Isotopic Composition of Mantle Xenoliths from Mt. Vulture Volcano, S. Italy (original) (raw)

Ofioliti, 1999

Abstract

Mt. Vulture volcano is located at the eastern margin of the Apennines, S. Italy and belongs to the Intra- mountain Ultra-alkaline Magmatic Province (Stoppa & Lavecchia , 1993). It is composed of Recent tephrites, basanites, phonolites and melilitites (De Fino et.al, 1982). Mantle xenoliths are found in the youngest unit of the volcano, a sequence of melilititic and carbonatitic tuffs. They are very fresh, mainly lherzolites and wehrlites. A few harzburgites and orthopyroxene (En89, Wo 2.0), clinopyroxene (Mg# 90-92, Al2O3 = 3-6 wt%, Cr2O3% ~1%) and one composite xenolith have also been found. The main mineral phases are olivine (Fo 90- 92), Cr-spinel ( MgO = 12-20 wt%, Cr2O3 = 30-40 wt%). Glasses are frequently found and are thought to represent in situ partial melting. Mica (phlogopite) is found in a few xenoliths. Carbonate is also present occasionally. The xenoliths have been derived from a depth between 55-75 km, corresponding to the spinel stability field in the upper mantle (J...

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