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- Title
Multi-stage metasomatism in the lithosphere beneath the Veneto Volcanic Province (VVP, Northern Italy).
- Authors
Cannatelli, Claudia
- Abstract
Mantle peridotites from the Veneto Volcanic Province (VPP) have been investigated in order to constrain P-T conditions of mantle events, determine the style of the metasomatic reactions, and the compositions of the metasomatic agents. Studied rocks show dominant protogranular and transitional textures; only one sample shows effect of pyrometamorphism. Clinopyroxenes in protogranular lherzolites show depleted LREE patterns, while those of transitional rocks are characterised by spoon-shaped REE patterns (La up to 60 times chondrite), and variable enrichments in LILE. Two generations of fluid inclusions are recognised: 1) Type I (CO ± CO ± C fluid) found only in orthopyroxene of transitional xenoliths which may contain very small amphibole; 2) Type II (CO-rich fluid) found in all minerals of all xenoliths. Most of inclusions homogenize to liquid, with Th ranging between −44 and 31°C. The densest CO fluid inclusions ( d = 1.13 g/cm), indicates a trapping pressure of ~10 kbar at 800°C. We propose that the mantle beneath the VVP equilibrated at pressures of 10 kbar, at about 800°C. Traces of an aqueous fluid preserved as fluid inclusions in orthopyroxene suggest the existence of an older subduction related metasomatic event and the occurrence of two stages metasomatism in the lithosphere beneath the SE Alps.
- Subjects
NORTHERN Italy; METASOMATISM; LITHOSPHERE; VOLCANIC fields; PERIDOTITE; FLUID mechanics; INCLUSIONS in igneous rocks
- Publication
Mineralogy & Petrology, 2012, Vol 104, Issue 3/4, p177
- ISSN
0930-0708
- Publication type
Academic Journal
- DOI
10.1007/s00710-011-0185-3