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volcano into two stages, which corresponds to two distinct magma series: the
leucite-rich high K-series of stage 1, and the leucite-poor to leucite-free K-series of
stage 2 (Appleton 1972). Luhr and Giannetti (1987) thought that stage 1 activity
constitutes bulk of the volcanism associated with Roccamon
na. This is the period
when the main cone was constructed from repeated lava, pyroclastic fall and
pyroclastic eruption associated with mud
ows. During this period the leucite-rich
high K-series (mainly leucite tephrites up to 13 wt% CaO) to leucite phonolites (up
to 2 wt% CaO) were erupted. The pyroclastic activity was associated with pho-
nolitic lavas, which were predominant towards the end of stage 1 activity. Luhr and
Giannetti (1987) considered that a major pyroclastic
flow erupted near the end of
stage 1, about 385 ka years ago. These tuffs are compositionally zoned and have
been reported as Brown Leucitic Tuff. These pyroclastic
flows have a minimum
5km
3
. Luhr and Giannetti divided the Brown Tuff into three facies:
white, brown and orange, on the basis of their colour, lithic content and matrix
concentration. The pumices have crystal content of 9.9
volume of 3
-
0.6 vol%. In terms of vol%
of minerals, they comprise, green salite > plagioclase > sanidine > biotite > titanomag-
netite > analcite (after leucite) > apatite > pyrrhotite. Plagioclase is anorthite-rich
(An
85
-
95
) and sanidine (Or
75
-
90
) has very low albite content. In the Brown Leucitic
Tuff primary leucite has been completely analcitized. The rocks are usually char-
acterized by diopside and forsterite-rich olivine (Fo
83
-
92
). Diopside often grades to
green salite. According to them, complex zonation of pyroxene may suggest their
formation by mixing of two different types of magmas.
Except for Na
2
O and K
2
O the leucite-bearing tuffs have chemistry similar to the
high K-series lavas of Roccamon
-
na. There is a nicely developed summit caldera at
Roccamon
6.5 km across. There is another
smaller semi-circular caldera (gli Stagli), which touches the main caldera. The main
caldera was probably formed before the eruption of Brown Leucitic Tuff. The gli
Stagli caldera was formed after the eruption of the Brown Leucitic Tuff, which in
turn is overlain by rocks of potassic series. There is also a 30 m thick sequence of
leucite-bearing high K-series tephra above.
According to Luhr and Giannetti, the beginning of stage II activity of Rocca-
mon
na. The diameter of the caldera is 5.5
-
na is marked by the eruption of compositionally-zoned white trachytic tuff
about 300,000 years ago. This was followed by a complex sequence of pyroclastic
eruption in the northern part of the volcano resulting in the formation of
“
gli Stagli
”
caldera and a thick section comprising leucite latite,
'
leucite basalt
'
, and trachytic
pyroclastic fall and
flow deposit. Finally eruption of Yellow Trachyte Tuff took
place in the Conca Campania and Vezzara. This was followed by further eruption of
leucite basalt, leucite latite and trachybasalt. This eruption is referred to as Stage (II)
eruption, the rock type of which is dominated by lavas of K-series. Except for
'
'
and leucite latites, the other rock types are free from leucite. Stage
II lavas are depleted in K and related incompatible elements compared to Stage I
lavas, which are basically high K-series rocks. Stage II rocks are characterized by
lower
leucite basalts
87
Sr/
86
Sr and higher
143
Nd/
144
Nd and
206
Pb
207
Pb ratios. The
final volcanic
events at Roccamon
flow units from the Campanian
ignimbrites, a compositionally-zoned pyroclastic deposit, which erupted about
na involved deposition of
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