Kürşad Asan

First Evidence of Lamprophyric Magmatism from the Konya Region, Turkey: a Genetic Link to High-K Volcanism

In the vicinity of Konya (Turkey), mafic, micro-porphyritic sub-volcanic rocks intrude into the Mesozoic units, which represents the only example of such a rock type in the region. 40Ar/39Ar dating of two whole rock samples from the sub-volcanics gave ages of 13.72±0.13 and 12.40±0.11 Ma, suggesting temporal association to the Late Miocene-Pliocene high-K calc-alkaline volcanism in the region. The mineral chemistry and geochemical data permit us to classify the rocks as “minette” lamprophyres. They include diopside and phlogopite phenocrysts in a microcrystalline groundmass composed of sanidine, phlogopite, diopside and titano-magnetite. Segregation and ocelli-like globular structures occur commonly in the samples. In terms of major elements, the lamprophyres are calcalkaline, and potassic to ultrapotassic rocks. All the lamprophyres display strong enrichments in LILE (Rb, Ba, K, Sr), radiogenic elements (Th, U) and LREE (La, Ce) and prominent negative Nb, Ta, and Ti anomalies on primordial mantle-normalized trace element diagrams. Geochemical data suggest that the lamprophyres and high-K calc-alkaline rocks in the region derived from a subduction-modified lithospheric mantle source affected by different metasomatic events. Lamprophyric magmatism sourced phlogopite-bearing veins generated by sediment-related metasomatism via subduction, but high-K calc-alkaline magmas are possibly derived from a mantle source affected by fluid-rich metasomatism.

Petrogenesis of the Üçkapılı Granitoid and its Mafic Enclaves in Elmalı Area (Niğde, Central Anatolia, Turkey)

The Late Cretaceous Uckapili Granitoid including mafic microgranular enclaves intruded into metapelitic and metabasic rocks, and overlain unconformably by Neogene ignimbrites in the Nigde area of Turkey. It is mostly granite and minor granodiorite in composition, whereas its enclaves are dominantly gabbro with a few diorites in composition. The Uckapili Granitoid is composed mainly of quartz, K-feldspar, plagioclase, biotite, muscovite and minor amphibole while its enclaves contain mostly plagioclase, amphibole, minor pyroxene and biotite. The Uckapili Granitoid has calcalkaline and peraluminous (A/CNK= 1.0-1.3) geochemical characteristics. It is characterized by high LILE/HFSE and LREE/HREE ratios ((La/Lu)N= 3-33), and has negative Ba, Ta, Nb and Eu anomalies, resembling those of collision granitoids. The Uckapili Granitoid has relatively high 87 Sr/ 86 Sr(i) ratios (0.711189-0.716061) and low eNd(t) values (-5.13 to -7.13), confirming crustal melting. In contrast, the enclaves are tholeiitic and metaluminous, and slightly enriched in LILEs (K, Rb) and Th, and have negative Ta, Nb and Ti anomalies; propose that they were derived from a subduction-modified mantle source. Based on mineral and whole rock chemistry data, the Uckapili granitoid is H-(hybrid) type, post-collision granitoid developed by mixing/mingling processes between crustal melts and mantle-derived mafic magmas.