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minor amounts of apatite and graphite. These veins are ultrapotassic with high
concentration of large ion lithophile elements, light rare earth elements (LREE) and
such mantle compatible elements as Cr and Ni. There is enough evidence to suggest
reaction of metasomatic agents with peridotites. Further more, glimmerites show
strongly fractionated REE patterns, negative anomalies of Nb, Ta and Ti and with
except for one example, very low Zr and Hf abundances. The absence of feldspars
and their low Na
2
O and CaO abundance rule out the possibility of crystallization of
phlogopites from a melt. The felsic granulites have low Th, U and Cs abundance
and high Rb/Cs ratio plementary to the glimmerites. Both rock types overlap in
initial Sr
Nd isotopic composition and show negative Eu anomalies. According to
Becker et al. (1999) the chemical evidence and high F abundance in prograde
biotite inclusion in granulite garnets indicate that the glimmerites may have crys-
tallized from a
-
fluid, liberated during the high temperature-pressure breakdown of
F-rich phlogopite in the felsic granulites. The
fluid must have contained HF, H
2
O
and carbon species as major volatile components. The minor occurrence of mica-
poor dolomite veins with glimmerites suggests that liquid immiscibility might have
played a signi
cant role in the formation of these rocks. Glimmerites probably
represent potential precursors to potassic magmas in collision zones.
4.8.4 Potassic Volcanism in Italy
The potassic volcanism in Italy was widespread during Quaternary along the
Tyrrhenian margin from the Vulsini to Vulture volcanic complex (Beccaluva et al.
1991, Fig.
4.20
a and b). The existence of calc-alkaline shoshonite and associated
ultrapotassic Oligocene volcanic rocks have been extended further in the north-
western Alps by Venturelli et al. (1984). According to these petrologists, volcanism
in this region was related to extensive block-faulting and rifting during the period
between Upper Miocene and Present on the western side of the Apennine chain.
The continent-continent collision in the Mediterranean region took place during
Eocene (Patacca and Scandone 1987) and Lower Miocene, and the volcanic activity
of the Roman Province took place after the continent-continent collision. According
to Beccaluva et al. (1991) the entire volcanic complex is located between the
Neogene compressional front of the Apennine-Maghrebian nappes and the
Tyrrhenian back-arc basin followed by Pliocene oceanic-type crust. They thought
that on a regional scale the volcanism of the Roman Province can be treated as the
northernly expression of the Quaternary orogenic activities between the Aeolian
and Southern Tuscania. They further considered that although there was block
faulting and rifting, the present day extensional tectonic setting is different from
major continental rift such as the East African and Rhine graben systems.
The Campanion volcanism took place in the southern most part of a complex
graben system extending for about 700 km along the Tyrrhenian margin of Italy
from Tuscany to Campania. According to Beccaluva et al. (1991), in contrast to the
Latium and Roccamon
na complexes in the Roman Province, Italy, there was
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