gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/002646198547927 Petrogenetic Implications of Ba-Sanidine in the Lionato Tuff (Colli Albani Volcanic District, Central Italy) Gaeta Mario Dipartimento di Scienze della Terra, Università degli Studi di Roma, ‘La Sapienza’, Piazzale A. Moro 5, 1-00185 Rome, Italy 10 1998 62 5 697 701 18 7 1997 5 2 1998 Copyright © 1998, The Mineralogical Society 1998 Abstract

A vitric fiamme containing BaO-bearing sanidine (BaO = 11 wt.%) was sampled (via di Fioranello, Rome) in the pyroclastic products of the Lower Flow Unit (LFU) belonging to the Villa Senni Eruption Unit in the Colli Albani Volcanic District (Roman Comagmatic Province, Central Italy). The fiamme of the LFU is essentially made up of glass, in which scarce phenocrysts of BaO-bearing sanidine, leucite and Al2O3-bearing Ca-clinopyroxene occur. In this paper the various parameters controlling barium partitioning between alkali feldspar and LFU liquid, are discussed.

 Keywords Ba-sanidine K-foidites Alban Hills Central Italy