A subvolcanic body in Colle Fabbri (Umbria, Central Italy) intrudes sedimentary rocks and the overlaying extrusive breccia. The intrusive rock is melilitolite with essential leucite, kalsilite, and wollastonite plus accessory Ti-garnet, Ti-Al-Fe(3+)-clinopyroxene, magnetite, perovskite, rankinite, Si-bearing apatite, Fe-Ni sulphides, and carbonate/zeolite. Bulk chemistry of melilitolite indicates a strong SiO(2)-undersaturation, extremely high CaO composition, and strong initial potassic character. Sr and Nd isotopic ratios support a link with the source of kamafugites and carbonatites found in the same region. The igneous contact rock contains variable amounts of quenched clinopyroxene, anorthite, sanidine +/- wollastonite, plus spinel and glass. Extremely high temperature melilitolite magma digested pelite country-rock, thus leading to a unique mineral composition. The homogenisation temperatures of mineral inclusions in contact rock demonstrate that crystallisation occurred well above 1230 degrees C. A large thermal aureole formed in a local clinker-like breccia, characterised by the association of felsic glass + indialite + tridymite +/- Ti-magnetite, confirms high-temperature emplacement. Metasomatic/thermometamorphic phenomena favoured zone-specific mineralisation of hydrated Ca-silicates, hydrated complex sulphates and zeolites in breccias and encasing rocks.

Melilitolite intrusion and pelite digestion by high temperature kamafugitic magma at Colle Fabbri, Spoleto, Italy

STOPPA, Francesco;
2009-01-01

Abstract

A subvolcanic body in Colle Fabbri (Umbria, Central Italy) intrudes sedimentary rocks and the overlaying extrusive breccia. The intrusive rock is melilitolite with essential leucite, kalsilite, and wollastonite plus accessory Ti-garnet, Ti-Al-Fe(3+)-clinopyroxene, magnetite, perovskite, rankinite, Si-bearing apatite, Fe-Ni sulphides, and carbonate/zeolite. Bulk chemistry of melilitolite indicates a strong SiO(2)-undersaturation, extremely high CaO composition, and strong initial potassic character. Sr and Nd isotopic ratios support a link with the source of kamafugites and carbonatites found in the same region. The igneous contact rock contains variable amounts of quenched clinopyroxene, anorthite, sanidine +/- wollastonite, plus spinel and glass. Extremely high temperature melilitolite magma digested pelite country-rock, thus leading to a unique mineral composition. The homogenisation temperatures of mineral inclusions in contact rock demonstrate that crystallisation occurred well above 1230 degrees C. A large thermal aureole formed in a local clinker-like breccia, characterised by the association of felsic glass + indialite + tridymite +/- Ti-magnetite, confirms high-temperature emplacement. Metasomatic/thermometamorphic phenomena favoured zone-specific mineralisation of hydrated Ca-silicates, hydrated complex sulphates and zeolites in breccias and encasing rocks.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11564/135787
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