High-Mg ultrapotassic volcanic rock occurrences of lamproitic affinity are exposed in southwestern Anatolia, mostly within the Menderes Massif. From north to south the lamproitic volcanism shows increasingly younger ages ranging from 20 to 4 Ma. Volcanism is contemporaneous with more voluminous shoshonitic, high-K calc-alkaline, and ultrapotassic magmatic activity in the Simav–Selendi, Uşak, Kırka, Köroğlu, Afyon and Isparta–Gölcük areas. The southward decrease in the age of the volcanism correlates with changes in geochemical composition, particularly a decrease in ⁸⁷Sr/⁸⁶Sr, ²⁰⁷Pb/²⁰⁴Pb, Zr/Nb and Th/Nb, and an increase in ¹⁴³Nd/¹⁴⁴Nd, ¹⁷⁶Hf/¹⁷⁷Hf, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb and Ce/Pb, thus delineating a systematic change from orogenic (crust-like) to anorogenic (convecting mantle-like) signatures. Rare earth element compositions of clinopyroxene phenocrysts demonstrate an increasing role for residual garnet for locations in the central parts of the Menderes Massif, indicating a lithosphere thickness greater than 80 km. In contrast, K₂O abundances remain nearly constant at around 7%, indicating buffering by phlogopite in the mantle source. Magma genesis in southwestern Anatolia is controlled by post-collisional extensional events initiated after major lithospheric thickening. Geochemical constraints suggest that the mantle source experienced two main geodynamic stages. The first stage caused ultradepletion of the mantle and subsequent metasomatic enrichment, which allowed coupling of the geochemical signatures of ultradepleted harzburgite with those of crust-derived sediments. This happened during the final closure stages of the southern Neotethys Ocean and the accretion of forearc oceanic lithosphere (island-arc type), as shallowly subducted material to the Anatolian lithosphere. The second stage is post-collisional, and is related to the collapse of the orogenic belt and the development of extension-related horst and graben structures. This stage is concurrent with the initiation of a thermal anomaly originating from a gap, identified by seismic tomography, in the subducted slab under western Anatolia. We propose that the lithospheric mantle underwent intense ‘asthenospherization’ owing to lithosphere–asthenosphere interaction, caused by the southward expansion of this gap during slab roll-back. The geochemical resemblance of the lamproites to more voluminous, contemporaneous shoshonitic magmas implies their derivation from a heterogeneous mantle source that had been affected by similar processes. These mantle processes may be closely associated with the major episode of uplift in the Menderes Massif.

The Serbian province of Tertiary ultrapotassic volcanism is related to a post-collisional tectonic regime that followed the closure of the Tethyan Vardar Ocean by Late Cretaceous subduction beneath the southern European continental margin. Rocks of this province form two ultrapotassic groups; one with affinities to lamproites, which is concentrated mostly in the central parts of the Vardar ophiolitic suture zone, and the other with affinities to kamafugites, which crops out in volcanoes restricted to the western part of Serbia. The lamproitic group is characterized by a wide range of ⁸⁷Sr/⁸⁶Sr_i (0·70735–0·71299) and ¹⁴³Nd/¹⁴⁴Nd_i (0·51251–0·51216), whereas the kamafugitic group is isotopically more homogeneous with a limited range of ⁸⁷Sr/⁸⁶Sr_i (0·70599–0·70674) and ¹⁴³Nd/¹⁴⁴Nd_i (0·51263–0·51256). The Pb isotope compositions of both groups are very similar (²⁰⁶Pb/²⁰⁴Pb 18·58–18·83, ²⁰⁷Pb/²⁰⁴Pb 15·62–15·70 and ²⁰⁸Pb/²⁰⁴Pb 38·74–38·99), falling within the pelagic sediment field and resembling Mesozoic flysch sediments from the Vardar suture zone. The Sr and Nd isotopic signatures of the primitive lamproitic rocks correlate with rare earth element fractionation and enrichment of most high field strength elements (HFSE), and can be explained by melting of a heterogeneous mantle source consisting of metasomatic veins with phlogopite, clinopyroxene and F-apatite that are out of isotopic equilibrium with the peridotite wall-rock. Decompression melting, with varying contributions from depleted peridotite and ultramafic veins to the final melt, accounts for consistent HFSE enrichment and isotopic variations in the lamproitic group. Conversely, the most primitive kamafugitic rocks show relatively uniform Sr and Nd isotopic compositions and trace element patterns, and small but regular variations of HFSE, indicating variable degrees of partial melting of a relatively homogeneously metasomatized mantle source. Geochemical modelling supports a role for phlogopite, apatite and Ti-oxide in the source of the kamafugitic rocks. The presence of two contrasting ultrapotassic suites in a restricted geographical area is attributable to the complex geodynamic situation involving recent collision of a number of microcontinents with contrasting histories and metasomatic imprints in their mantle lithosphere. The geochemistry of the Serbian ultrapotassic rocks suggests that the enrichment events that modified the source of both lamproitic and kamafugitic groups were related to Mesozoic subduction events. The postcollisional environment of the northern Balkan region with many extensional episodes is consistent at regional and local levels with the occurrence of ultrapotassic rocks, providing a straightforward relationship between geodynamics and volcanism.