Mineralogy and Petrology of kamafugite, leucitolite, syenite and carbonatite xenoliths, from the Egirdir lake area, West-Anatolia, Turkey: new insights of the ultrapotassic magmatism.

Résumé éditeur

Plutonic xenoliths have been found within a pipe and a related phreatomagmatic leucitite deposit in the Egirdir lake area, belonging to the Potassic-Ultrapotassic Afyon volcanic Province, West Anatolia. They consist of kamafugite-types, feldspar-bearing syenites, pyroxenites, leucitolites, some small size melilitolite and garnet-rich xenoliths, and a carbonatite. A new occurrence of kalsilite is described either as homogeneous acicular crystals, or tabular two phases-exsolved crystals in the kamafugite-types and melilitolite xenoliths. Rock textures and compositions point out cumulates and rocks closer to liquid composition corresponding to relatively evolved magmas. All the rocks are strongly silica-undersaturated, Ca-, Mg-, K-rich, Al-poor. Fractional crystallization model includes clinopyroxene, apatite, phlogopite, melilite and leucite. Fe-Ti oxides and garnet may be also concerned. The PH2O during crystallization and differentiation is not more than 0.8GPa. Major elements, trace elements and REE patterns for xenoliths which are near liquid compositions, are typical of ultrapotassic series in a post-collision geodynamic context, as it is for the Roman and Central ultrapotassic Italian Provinces. The stable isotope 13C and 18O values of the calciocarbonatite plot close to the primary carbonatite field, whereas carbonates of the feldspar-bearing syenite and the peperite matrix suggest a low-T extensive contamination process. The origin of carbonatite from kamafugite-type magmas by immiscibility or by fractional crystallization remains questionable, the origin by fractionation-melting of a metasomatized mantle source, would be tested in the future.