Petrographical and geochemical investigation of the yunak (Konya) lamproitic rocks

In this study, petrographical and geochemical (major-trace element and Nd-Hf isotopes) properties of lamproitic rocks from the Yunak area (Konya) were investigated. Jurassic-Cretaceous limestone, dolomite and ophiolitic rocks constitue basement of the study area. Mio-Pliocene fluvio-lacustrine deposits and Yunak Lamproitic Rocks (YLK) which outcrops as small volume lava flows, unconformably overlie this basement. The YLK units are characterized by porphyritic textures in which variable amounts of olivine, clinopyroxene, phlogopite, and rare amphibole phenocrysts are set in microlitic or microcrystalline groundmass rich in sanidine, clinopyroxene and opaque minerals. The YLK units are classified as olivine lamproite, phlogopite lamproite, and olivine phlogopite lamproite representing the transition between them. The SiO2 contents of the YLK units vary from 53% to 57% and they geochemically exhibit ultrapotassic (K2O: 5-11%; MgO: 6-11% and K2O/Na2O: 3-11%) character. Additionally, YLK has high Ba (~1000-4000 ppm), Zr (~500-1000 ppm), Sr (~950-1100 ppm) contents. YLK units exhibit two different types of incompatible trace element patterns: orogenic (olivine lamproite; relatively high LILE/HFSE ratios) and anorogenic (phlogopite lamproite; relatively low LILE/HFSE ratios). Additionally, there exists a significant difference in Nd-Hf isotope compositions between olivine lamproites (ɛNd: -5.93 to -6.03; ɛHf: -8.01 to -8.41) and phlogopite lamproites (ɛNd: -2.32; ɛHf: 5.92). These two geochemically different rock groups cannot be related to each other by fractional crystallization. Moreover, the effect of crustal contamination in the evolution of the studied lamproitic rocks is insignificant. Thus, the prominent geochemical difference indicates that they were derived from different mantle sources. The obtained geochemical findings show that the orogenic YLK units were derived from a lithospheric mantle source metasomatized by recent subduction-related processes, while the anorogenic YLK units were derived from a lithospheric mantle source that has been additionally enriched with asthenospheric melts.