Monte la Queglia (Mt. Queglia), Pescosansonesco, Pescara Province, Abruzzo, Italyi

Regional Level Types
Monte la Queglia (Mt. Queglia)	Mountain
Pescosansonesco	Municipality
Pescara Province	Province
Abruzzo	Region
Italy	- not defined -

Subvolcanic dyke swarm with primary paragenesis and alkali-mafic petrochemistry intruding Upper Cretaceous–Eocene limestone (Santo Spirito Formation) on the west slope of Monte la Queglia, 1 km west of Pescosansonesco.

The Monte la Queglia dykes are intruded into Upper Cretaceous–Eocene limestones and therefore their age must be Eocene or younger. They have sharp contacts with the host rock and no evidence of thermal metamorphism. They range from 1.5 to 6.5 m in thickness and form a dyke swarm about 15 m wide. here The lamprophyre is brecciated and the entire body pervaded by veins of calcite. Ocellar structures, up to 0.5 cm across, are widespread.

The dyke rock is ultramafic and porphyritic, with an intergranular/intersertal groundmass. The phenocrysts are chlorite and carbonate pseudomorphs after olivine (up to 4 mm across), TiO2- and Cr2O3-rich-diopside, with TiO2 and Cr2O3 up to 8 and 0.5 wt.%, respectively, rectangular carbonated pseudomorphs interpreted as altered melilite (Durazzo et al., 1984) and apatite crystals up to 6 mm long. Chromite inclusions occur in olivine and Cr-rich diopside. Microphenocrysts are titaniferous pyroxenes, ranging in composition from diopsidic cores to aegirinic rims, titaniferous micas with eastonitic cores and tetraferriannitic rims, pseudomorphed melilite and apatite. Perovskite is a frequent inclusion in melilite and pyroxene. Aegirines, Ti-rich phlogopite with biotitic rims, apatite, spherulitic K-feldspar, carbonates, zeolites, a minor amount of nepheline, Ti-magnetite and altered glass make up the groundmass. Pyrite, chalcopyrite and brookite–rutile also occur as small crystals (up to 10 μm) in the groundmass.

Calcite is found in several different occurrences: pseudomorphs after olivine and melilite; small veins of secondary calcite; intergranular space infilling; and segregation patches that are coarser grained than the rest of the rock and lined by branching and curved crystals of pyroxene and rare mica. K-feldspar is abundant in the segregation patches and usually associated with aegirine, apatite, and mica, which have co-precipitated with carbonate. The ocelli can make up 25 vol.% of the rock in places and are spherical or drop-like shaped, often coalescent. They are composed of calcite with rims outlined by tangentially arranged small crystals of pyroxene, mica and opaques. Part of the structure can be filled by branching and curved pyroxene, growing perpendicular from the rim towards the centre of the ocellus, set in a groundmass of carbonate, with subordinate K-feldspar and zeolites.

Although the rock has been previously classified as "ultramafic lamprophyre with alnöitic affinity" (Durazzo et al., 1984), the modal abundance of melilite (together with the lack of abundant hydrous minerals) leads to the classification of this rock as olivine-melilitite. The Cr+Ni content is the highest of all the Italian carbonatitic lamprophyres, at up to 1012 ppm (Vinchi et al., 2005).

Geochronology

Mineralization age: Phanerozoic : ~145.0 Ma to 33.9 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Phanerozoic
	Cenozoic
		Paleogene
			Eocene	ⓘ Limestone (youngest age) Eocene
	Mesozoic
		Cretaceous

Other Regions, Features and Areas containing this locality

References