Volcanic activity at Mt. Vulture lasted about 750 ka and produced SiO 2 -undersaturated volcanic rocks that can be classified as old (~700 ka), intermediate (~600-550 ka), and young (~130 ka). The intermediate deposits consist of pyroclastic falls and flows and lavas with compositions ranging from phonolite to foidite. A recent revision of the stratigraphic setting allowed these deposits to be classified into one synthem (the Barile Synthem) and further subdivided into four subsynthems (Toppo S. Paolo, Rionero, Vulture-S. Michele, and Ventaruolo). In the present investigation, trioctahedral micas from sample VUT191 in the Vulture-S. Michele Subsynthem are considered. The host rock has modal diopside (20.2%), analcime (22.8%), plagioclase (27.8%), haüyne (5%), phlogopite (8.9%), and magnetite (6.3%). The micas were studied using chemical (EPMA, C-H-N, SIMS), structural (SCXRD), and spectroscopic (Mössbauer) methods.EPMA of 36 crystals from thin sections and 6 discrete crystals selected for the structural analysis showed remarkable compositional variability, as follows (in wt%): SiO 2 = 33.14-38.01, Al 2 O 3 = 15.56-20.45, MgO = 13.02-20.81, FeO tot = 6.34-14.08, TiO 2 = 2.34-6.02, K 2 O = 6.03-9.48, Na 2 O = 0.50-0.78, and BaO = 0.89-4.06; all crystals proved to be phlogopite. Elemental C-H-N analyses yielded H 2 O = 2.86 � 0.36 wt%. The water content was also determined by SIMS on two single crys-� 0.36 wt%. The water content was also determined by SIMS on two single crystals, labeled VUT191_2 and VUT191_19, which yielded values of 3.81 � 0.12 and 1.72 � 0.08 wt% H 2 O, respectively. Mössbauer investigation showed that all the iron in VUT191 mica is octahedral with Fe 2+ = 25.5% and Fe 3+ = 74.5%, confirming that Vulture micas are particularly Fe 3+ -rich, as also found from previous investigations. Structure refinements using anisotropic displacement parameters were performed in space group C2/m and converged at 1.89 ≤ R ≤ 3.17, 2.09 ≤ R w ≤ 3.43%. All of the analyzed micas belong to the 1M polytype but exhibit remarkable variations in the c parameter from 10.1569(4) to 10.2458(4) Å. The chemical and structural parameters indicate that the studied micas can be divided into two groups: the first encompassing strongly dehydrogenated micas affected mainly by Ti-oxy [ VI M 2+ + 2(OH) -↔ VI Ti 4+ + 2O 2-+ H 2 ] and M 3+ -oxy [ VI M 2+ + (OH) -↔ VI M 3+ + O 2-+ ½H 2 , with M 3+ = Fe 3+ , Al 3+ ] substitutions. The second group consist of samples in which vacancy-bearing mechanisms, 2 VI M 2+ ↔ VI Ti 4+ + VI n and 3 VI M 2+ ↔ 2 VI M 3+ + VI n occur.

Volcanic activity at Mt Vulture lasted throughout the Middle Pleistocene and produced SiO 2 -undersaturated volcanics. Deposits from the Monte Vulture stratovolcano have been classified into four subsynthems and clustered into the Barile Synthem. In the present investigation, trioctahedral micas from the uppermost units (the Ventaruolo Subsynthem) of the Barile Synthem are considered. The samples are labelled VUT187. The phlogopitic micas were separated from the host rock (an olivinefoidite) and underwent chemical (electron microprobe analysis -EMPA and C-H-N), structural (singlecrystal X-ray diffraction) and spectroscopic (Mössbauer) investigations. The EMPA yielded: MgO (17.62À21.89 wt.%), FeO tot (5.98À9.78 wt.%), TiO 2 (1.81À3.92 wt.%) and Al 2 O 3 (14.47À17.98 wt.%), with H 2 O contents = 2.86 (Ô0.42) wt.% determined by C-H-N analyses. Mössbauer investigation provided [VI] Fe 2+ = 12.6%, [VI] Fe 3+ = 87.4%. The chemical and structural data are consistent with the occurrence of Ti-oxy, [VI] M 2+ + 2(OH) À > [VI] Ti 4+ + 2O 2À + H 2 , and M 3+ -oxy substitutions, [VI] M 2+ + (OH) À > [VI] M 3+ + O 2À + ÝH 2 , with M 3+ = Fe 3+ , Al 3+ . In particular, Fe 3+ -oxy substitution has affected the Fe 2+ /Fe 3+ ratio in the studied sample. This is probably due to the fact that interaction with underground water or a hydrothermal system may have altered the oxygen fugacity and raised the Fe 3+ content of VUT187 phlogopite with respect to magmatic values.