Peridotite xenoliths entrained in Plio-Pleistocene alkali basalts from north-central Sardinia represent fragments of the uppermost lithospheric mantle and offer the opportunity to investigate the subcontinental upper mantle beneath the central Mediterranean. These rocks range in bulk composition from fertile spinel-lherzolites to residual spinel-harzburgites. Previous studies illustrated that such peridotite samples suffered variable degrees of partial melting followed by enrichment associated to metasomatism, in turn due to fluids rising through the lithosphere. In this study we explore the chemical and isotopic characteristics of noble gases (He, Ne, Ar) retained into fluid inclusions of olivine and orthopyroxene belonging to this peridotitic suite. This approach allows to evaluate the noble gas characteristics of the mantle source without the potential interferences of crustal component additions. Measurements on samples previously characterised for their major, trace elements and Sr-Nd isotopic data have been performed by single-step crushing in ultra-high vacuum. Aim of the study is the identification of the noble gas isotope characteristics of the lithospheric mantle beneath Sardinia and comparison with trace elements and lithophile isotopes. In particular, by means of noble gases we would like to trace the possible involvement of metasomatic volatiles that were scarcely highlighted by lithophile elements.The first set of obtained data are presented and compared with other peridotite samples of the European/Mediterranean mantle xenoliths.
Noble gases isotope composition of mantle-derived peridotite xenoliths from Sardinia
BIANCHINI, Gianluca
2015
Abstract
Peridotite xenoliths entrained in Plio-Pleistocene alkali basalts from north-central Sardinia represent fragments of the uppermost lithospheric mantle and offer the opportunity to investigate the subcontinental upper mantle beneath the central Mediterranean. These rocks range in bulk composition from fertile spinel-lherzolites to residual spinel-harzburgites. Previous studies illustrated that such peridotite samples suffered variable degrees of partial melting followed by enrichment associated to metasomatism, in turn due to fluids rising through the lithosphere. In this study we explore the chemical and isotopic characteristics of noble gases (He, Ne, Ar) retained into fluid inclusions of olivine and orthopyroxene belonging to this peridotitic suite. This approach allows to evaluate the noble gas characteristics of the mantle source without the potential interferences of crustal component additions. Measurements on samples previously characterised for their major, trace elements and Sr-Nd isotopic data have been performed by single-step crushing in ultra-high vacuum. Aim of the study is the identification of the noble gas isotope characteristics of the lithospheric mantle beneath Sardinia and comparison with trace elements and lithophile isotopes. In particular, by means of noble gases we would like to trace the possible involvement of metasomatic volatiles that were scarcely highlighted by lithophile elements.The first set of obtained data are presented and compared with other peridotite samples of the European/Mediterranean mantle xenoliths.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
