Origin and provenance of the Afyon Zone (western Anatolia): Constraints from detrital zircon U–Pb–Hf isotopes and mineral chemistry

The Afyon Zone in western Anatolia represents the northwestern part of the Anatolide–Tauride Block, a Gondwana–derived continental fragment. It comprises a late Neoproterozoic Pan–African basement overlain by Paleozoic to Mesozoic clastic and carbonate successions with minor igneous rocks. The Afyon Zone underwent Late Cretaceous–Paleocene (70–60 Ma) high-pressure/low-temperature metamorphism, indicating that it represents a fragment of subducted continental lithosphere. Despite its tectonic significance, the provenance history of the Afyon Zone remains poorly constrained due to limited geochronological data. In this study, we present new detrital zircon U–Pb–Hf isotopic and mineral chemistry data from metasedimentary sequences to constrain the origin and provenance of the Mount Murat region of the Afyon Zone.

Three metamorphic sequences were distinguished in the Mount Murat region based on depositional age and metamorphic grade: (i) polymetamorphic schists with late Neoproterozoic depositional ages, (ii) greenschist-facies metasandstones with late Permian–Late Triassic depositional ages, and (iii) sub-greenschist-facies metasandstones with Late Cretaceous depositional ages.

Late Neoproterozoic polymetamorphic schists are composed of white mica (phengite and muscovite), quartz, albite, chlorite, and accessory rutile. They contain Ediacaran (615–630 Ma) and subordinate Cryogenian (675–680 Ma) zircon age peaks with variable εHf values, and a minor Tonian–Stenian (987–1008 Ma) peak with predominantly negative εHf values. There are no zircon grains with ages between 1.8 and 1.1 Ga, similar to zircon ages in the Sakarya Zone and the northern margin of the Arabian Platform. Late Permian–Late Triassic metasandstones exhibit Neoproterozoic zircon age spectra that are broadly similar to those of the late Neoproterozoic units. Youngest zircon ages indicate maximum depositional ages of late Permian (259 ± 7 Ma) and Late Triassic (221 ± 7 Ma) for two samples in this sequence. The late Permian metasandstone records a minor Carboniferous (326 Ma) age peak characterized by negative εHf values. The Late Triassic metasandstone displays a prominent Triassic (230 Ma) zircon age peak with negative εHf values, indicating reworked crustal input. In contrast, Late Cretaceous metasandstones are characterized by a dominant Carboniferous (317 Ma) age peak with negative εHf values and a minor Triassic (235–240 Ma) zircon age cluster with predominantly positive εHf values, accompanied by subordinate Devonian (385–410 Ma) and Ordovician (450–470 Ma) ages. The maximum depositional age of the sequence is constrained by a single Late Cretaceous zircon age (77 ± 2 Ma). Zircon age spectra and corresponding εHf values indicate that the late Permian–Late Triassic metasandstones were sourced from the Anatolide–Tauride Block, a Gondwana–derived continental domain; however, the Late Cretaceous metasandstones reflect sediment input from the Sakarya Zone, a Laurasia–derived continental domain.