Geological, petrological, and geodynamical characteristics of the Karacaali Magmatic Complex (Kırıkkale) in the Central Anatolian Crystalline Complex, Turkey

Mafic and felsic igneous rocks in the Karacaali Magmatic Complex (KMC) in the northwestern margin of the Central Anatolian Crystalline Complex (CACC) are classified into 4 groups: i) granitoid pluton including granite, granodiorite, and monzonite; ii) a few meter-scale porphyritic microgranite enclaves within the hybrid rocks; iii) hybrid rocks formed by mixing/mingling of mafic lavas (basaltic/diabasic/lamprophyric), anorthositic, and/or rhyolitic lavas; iv) diabasic dykes/veins within the granitoid pluton. Major element composition of the granitoid pluton and porphyritic microgranite enclaves within the hybrid rocks indicate subalkaline, calc-alkaline, and mostly I-type characteristics. These rocks are mainly peraluminous with aluminum saturation index >1, but mainly between 1 and 1.1, indicating transitional peraluminous. On the tectonomagmatic discrimination diagrams (Y vs. Nb and (Y+Nb) vs. Rb diagrams), all the granitic and monzonitic rock suites from the complex fall mostly in the VAG+Syn-COLG and VAG fields respectively, suggesting arc-related origin. On the R1 vs. R2 tectonic diagram, the granitic rocks display distribution from preplate collision to syncollision field, but quartz-monzonitic samples plot within the postcollision uplift field. Based on limited geological, petrographic, and geochemical results, the tectonomagmatic evolution of the KMC can be summarized as follow: i) initiation of subduction of the Inner Tauride oceanic lithosphere beneath the CACC during the Late Cretaceous time; ii) underplating of partial melts derived from subducted slab and/or mantle wedge, which provided enough heat for partial melting of the mafic lower crust and generation of granitic magma; iii) slab detachment following the continent–continent collision that resulted in tensional forces within the overlying continental crust, which allowed the intrusion of the granitic magma to the upper crust, also cutting the central Anatolian ophiolites, from the Late Cretaceous to most likely the Paleocene time. The hybrid rocks formed by mixing/mingling of the mafic, anorthositic, and/or rhyolitic magmas most likely indicate their injection into a partly crystalline granitic magmatic system just after crystallization of granitic magma in the upper crust. However, this model is open to discussion and needs to be investigated using isotope data in future studies.