Geochemical, stable (O, C, and B) and radiogenic (Sr, Nd, Pb) isotopic data from the Eskişehir-Kızılcaören (NW-Anatolia) and the Malatya-Kuluncak (E-central Anatolia) F-REE-Th deposits, Turkey: implications for nature of carbonate-hosted mineralization

Abstract

In Turkey, the largest fluorine (F)-rare earth element (REE)-thorium (Th) deposits are located within the Eskişehir-Kızılcaören(north-western Anatolia) and the Malatya-Kuluncak (east-central Anatolia) regions, and these are associated with Oligocene extensionalalkaline volcanic and Late Cretecaous-Early Paleocene postcollisional intrusive rocks, respectively. In the Kızılcaören region, the basementunits include the Triassic Karakaya Complex and the Late Cretaceous oceanic units (Neotethyan suture) that are cut and overlainby phonolite and carbonatite intrusions and lava flows. In the Kuluncak region, the plutonic rocks are mainly composed of syenite,quartz syenite, and rare monzonite, and these cut the late-Cretaceous Karapınar limestone, which hosts the F-REE-Th mineralizationin contact zones. A carbonatite sample from the Kızılcaören region displays both a total rare earth element (TREE) concentration (4795ppm) and $delta^{11}$ (–6.83‰) isotope composition consistent with mantle-derived carbonatite; whereas it is characterized by heavier δ13C(+1.43‰) and $delta^{18}$O (+20.23‰) isotope signatures compared to those for carbonatites worldwide. In contrast, the carbonates whichhost the F-REE-Th mineralization in the Kuluncak region are characterized by lower TREE concentrations (5.13 to 55.88 ppm), andheavier $delta^{13}$ C (–0.14 to –0.75‰), $delta^{18}$ O (+27.36 to +30.61‰), and $delta^{11}$ B (+5.38 to +6.89‰) isotope ratios compared to mantle-derivedcarbonatites. Moreover, the combined initial ${}^{87}Sr/{}^{86}Sr$ (0.70584 to 0.70759) and ${}^{143}Nd/{}^{144}Nd$ (0.512238 to 0.512571) isotope ratios forsamples investigated here are distinct and much more radiogenic compared to those for carbonatites worldwide, and therefore indicatesignificant crustal input and/or hydrothermal metasomatic-related alteration. Overall, stable and radiogenic isotope data suggest thatthe host carbonate rocks for the F-REE-Th mineralization in both the Kızılcaören and the Kuluncak regions consist of hydrothermallymetasomatized carbonatite and limestone, respectively. The mineralization in the Kızılcaören region may potentially be related tocarbonatite magmatism, whereas the mineralization in the Kuluncak region, which most likely formed through interactions betweenthe plutonic rocks and surrounding limestone at contact metamorphism zone, involved hydrothermal/magmatic fluids associated withextensive postcollisional magmatism.