Different Localities of Potassium-Rich Silica-Undersaturated Igneous Rocks and Their Silica-Rich Variants - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 180

phenocrysts of alkali feldspar, ha yne, deep green clinopyroxene, magnetite,

melanite garnet (oscillatory zoning present), sphene and analcitized leucite set in a
groundmass of the same phases together with nepheline.
Melluso et al., studied a melilitite dyke of Prete Della Scimmia and ha

ü

ü yno-

phyres of Melfi. . The melilitite is constituted of phenocrysts of melilite, clinopy-

roxene and opaque minerals in a holocrystalline groundmass comprising apatite,
perovskite, garnet, nepheline, leucite and ha yne. These rocks also present ocellar

structure composed of calcite, magnetite, clinopyroxene and nepheline (Melluso
et al. 1996).
The Mel

ü

yne, zoned clino-
pyroxene, subordinate amount of leucite and apatite in a groundmass containing the
same phases with additional nepheline, melilite and magnetite.
A melafoidite (melilite ankaratrite) is also noted in south Caterina. These rocks
comprise phenocrysts of clinopyroxene in a

ha ü ynophyre is composed of phenocrysts of ha ü

fine-grained groundmass with clino-

pyroxene, nepheline, ha ü yne, leucite, apatite and opaque minerals along with pale

yellow laths of melilite.
Solovova et al. (2005) studied the chemistry of melt and fluid inclusions in

minerals of an olivine-leucite phonotitic nephelinite bomb from the Monticchio
Lake Formation in Vulture. The rock contains 50 % clinopyroxene, 12 % leucite,
10 % alkali feldspars, 8 % hauyne/sodalite, 7.5 % nepheline, 4.5 % apatite, 3.2 %
olivine, 2 % opaques, 2.6 % plagioclase, and <1 % amphibole (all in vol%). They
distinguished three generations of clinopyroxene differing in composition and
morphology. All

uid
inclusions, which recorded successive stages of melt evolution. They observed that
the most primitive melts contained the most magnesian olivine and the earliest
clinopyroxene phenocrysts. The melts are near primary mantle liquids and are rich
in Ca, Mg and incompatible and volatile elements. Thermometric experiments with
the melt inclusions suggested that melt crystallization began at a temperature of
about 1,200

the phenocrysts bear primary and secondary melt and

fluid inclusions, the
pressure of crystallization is constrained only to minimum of 0.35 GPa. Combined
silicate-carbonate melt inclusions were found in apatite phenocrysts. According to
them they are indicative of carbonate-silicate liquid immiscibility, which occurred
during magma evolution. Large hydrous secondary melt inclusions were found in
olivine and clinopyroxene. The inclusions in the phenocrysts recorded an open-
system magma evolution during its rise towards the surface including crystalliza-
tion, degassing, oxidation, and liquid immiscibility processes.

° C. Because of the partial leakage of all primary

4.8.4.12 Latera Caldera

Turbeville (1993) studied petrology and genesis of the rocks of Latera Caldera.
According to him the Latera Plateau is constituted of 8 km 3 of tuffs, which are
exposed outside the caldera, and another 7 km 3 of intracaldera tuffs, established by
drilling. 40 Ar and 36 Ar content of sanidine crystals indicate that the explosive
eruption in the Latera Caldera took place in four episodes between 232 and 155 ka