Geology Reference
In-Depth Information
4.8.4.9 Kamafugitic Rocks Near L
'
aquila Abruzzo
of the Umbria
-
Latium-Ultra-Alkaline-District (Ulud) Near
Roman Province, Italy
Hovis et al. (2002) have described rare kamafugitic rocks near L
Aquila, Abruzzo
from. the Umbria Latium District (Ulud) near Roman Province. They tried to
establish possible genetic links between these rocks and those from the Oricola-
Camerata Nuova volcanic
'
field. The new
kamafugitic rocks were found in a cave known as Grotta del Cervo, where these
rocks are associated with epiclastic and pyroclastic materials. In the latter case,
lapilli ash tuff, welded lapilli, ultrama
field, occurring 20 km to the west of this
c xenoliths, cognate lithics and pelletal lapilli
have been identi
ed. The mineralogy of the welded lapilli comprises, in order of
decreasing abundance, the following minerals: diopside, leucite, hauyne, Mg-mica,
andraditic garnet, apatite, magnetite, kalsilite and olivine. The rock is carbonate-
free, and based on bulk-rock chemistry,
ed, as kamafugites. The
chemistry, closely approaches the composition of ULUD kamafugites (Sahama
1974). Separate lapilli and ash tuff (characterized by the same silicate mineralogy as
that of the welded lapilli, plus modal carbonate exceeding 10 wt%), is classi
it
is classi
ed as a
carbonatitic kamafugite. Bulk-rock and trace-element compositions con
rm that the
Grotta del Cervo rocks closely approach the ULUD analogues.
The Grotta del Cervo occurrence partially fills the geographical and composi-
tional gap between ULUD rocks and the rocks from the Vulture Complex, also a
carbonatite and melilitite-bearing locality situated 200 km south of Grotta del
Cervo, and adds considerably to the bulk chemistry of kamafugitic and related
rocks lying along the Italian Apennines.
4.8.4.10 Ischia
The Ischia Island (Fig.
4.25
) is located west-southwest of Naples. Together with
Phlegrean Fields and Somma-Vesuvius complex, it constitutes the Neopolitan
complex (Vezzoli 1988; Di Girolamo et al. 1995). The volcanic activities of Ischia
has been subdivided into four main phases:
(1) The
first phase (older than 150,000 years B.P.) was dominated by pyroclastic
products and associated lava
ows.
(2) The second phase was responsible for the formation of a lava dome formed
150,000
75,000 years B.P. Pyroclastic rocks are also intercalated with the lava
-
dome.
(3) This phase (55,000
20,000 years B.P.) was associated with eruption of
trachytic ignimbrites. The Green tuff of Mount Epomeo also erupted during
this phase. The volcanic activities continued from different centres and lava
-
flows in particular, were erupted towards the end of this phase.
(4) The last phase of volcanic activities started about 10,000 years B.P. The Arso
lava
flow (1302 A.D.) represents the last eruption of this island. The lavas of
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