Abstract
Spinel-lherzolite xenoliths trapped within the alkali basalts flow in the Liri region (Kapsiki Plateau) have a protogranular texture and consist of olivine, orthopyroxene, clinopyroxene and spinel crystals. These xenoliths are residues of partial melting of the primitive mantle, with the low titanium content in clinopyroxene crystals (TiO2 < 0.5 wt.%). The clinopyroxene of the spinel-lherzolite xenoliths from Liri, are divided into two distinct groups according to their trace element characteristics. The variations in the rare earths elements make it possible to classify the different clynopyroxenes in two groups: the first group consisting of the samples of Liri (Liri 1, Liri 02, Liri 3, Liri 05 and Liri 5) rich in light rare earths elements (LREEs), with ratios (Ce/Yb)N normalized which vary between 3.00 and 7.78. It is probably a cryptic metasomatism due to the absence of hydrated minerals (such as amphibole) which caused these enrichments. The second group comprises samples of Liri (Liri 01, Liri 2, Liri 04, Liri 4) depleted in light rare earths elements, with the ratio in (Ce/Yb) N < 1.2. This depletion in rare earths elements results from the extraction of the melting liquid.   Â
Highlights
Peridotite nodules broken to the surface by alkaline basalts provide us direct information on the processes and composition of the upper mantle
Clinopyroxene is a major host for many incompatible trace elements in peridotite xenoliths and as such its trace-element composition is a useful indicator of chemical modification in the mantle
The slight depletion of rare earths elements in the analyzed clinopyroxenes (Liri 01, Liri 2, Liri 04, Liri 4) compared with the other REE observed in the others clinopyroxenes from Liri is indicative of a partial melting episode, whereas light rare earth elements enrichments observed for other samples (Liri 1, Liri 02, Liri 3, Liri 05 and Liri 5) are significant for cryptic metasomatism [12]
Summary
Peridotite nodules broken to the surface by alkaline basalts provide us direct information on the processes and composition of the upper mantle. In the formerly petrological study on the Liri sector, major and trace elements of the host-basalt and the mineral chemistry of the spinel-lherzolite xenoliths are presented. According to these data, [1] proposed that the spinel-lherzolite xenoliths from Liri are the residues of partial melting of an initial mantle with a small degree of partial melting. This study is focused on the behavior of the clinopyroxenes trace elements, analyzed in spinel lherzolte xenoliths from Liri, in order to establish their petrological origin and thermobarometric stability conditions in the mantle, according to the mineral chemistry and crystal structure
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