Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia

Mt. Erciyes and Mt. Hasan are the two largest stratovolcanic complexes of the Central Anatolian Volcanic Province (Turkey). Despite geochronological evidence for early Holocene eruptions classifying both volcanic systems as active (Sarıkaya et al., 2019; Schmitt et al., 2014), their Late Pleistocene–Holocene chronostratigraphies remained poorly constrained. Combining zircon U–Th–Pb crystallization ages with trace element concentrations (zircon petrochronology) and (U–Th)/He cooling ages (zircon double-dating; ZDD), we identified contrasting magma recharge and eruptive recurrence patterns. Mt. Hasan, magmatically and volcanically active since ca. 550 ka, predominantly erupted andesitic lava domes and flows as well as block-and-ash-flows. Zircon double-dating indicates a Late Pleistocene recurrence of at least one eruptive episode every ca. 5–15 ka. Combined with volume estimates, zircon geochronology suggests Middle–Late Pleistocene eruptive magma fluxes of ~0.3–0.1 km3/ka, similar to continental arc volcanoes (Friedrichs et al., 2020a). Mt. Erciyes formed after the deposition of the Valibaba Tepe Ignimbrite with a U–Pb zircon age of 2.73 ± 0.02 Ma (all uncertainties 1σ). Its magmatic system is characterized by protracted zircon crystallization since at least ca. 800 ka. Episodes of scoria cone and lava dome as well as pyroclastic fall-out emplacement at ca. 105 and ca. 88–85 ka were followed by an extended eruptive lull. In an early Holocene resurgence, four peripheral rhyolitic–dacitic lava domes erupted, three of them with significant initial explosive phases. Yılanlı Dağ was emplaced at 9.4 ± 1.3 ka, Dikkartın at 8.9 ± 0.5 ka, and Karagüllü as well as Perikartın with their stratigraphically directly overlying pyroclastic deposits at 8.8 ± 0.8 ka (Friedrichs et al., 2021a). Tephra glass major and trace element geochemistry identifies Karagüllü as the source of a cryptotephra found in a Black Sea gravity core, calling for a re-evaluation of its age model. The chemically indistinguishable Dikkartın and/or Perikartın eruptions are potential sources of the Eastern Mediterranean S1 tephra, an important marker horizon for archaeological and paleoclimatological research. Proximal fall-out from the Dikkartın eruption indicates eastward dispersal from a 20 ± 5 km high eruption plume, in agreement with probabilistic tephra dispersal modeling results. Distal S1 tephra, however, is distributed up to ~1300 km south of Mt. Erciyes, suggesting tephra transport by low altitude rather than stratospheric winds. This may either be due to eolian reworking of proximal deposits or due to co-ignimbrite ash cloud dispersal (Friedrichs et al., 2020b). Contrasting thermochemical evolutions of the magma plumbing systems control the distinct eruptive styles and recurrence patterns. For Mt. Hasan, zircon crystallization temperatures and melt differentiation indices span comparably narrow, time-invariant ranges, whereas for Mt. Erciyes, these parameters fluctuate over broader ranges. Thermochemical modeling indicates moderate near-steady recharge into an upper crustal magma chamber beneath Mt. Hasan (“warm” storage, eruptible), but low and modulated magma recharge for Mt. Erciyes (“cold” storage, rheologically locked). Nonetheless, both systems may be reactivated by magmatic rejuvenation. Violent explosive eruptions would pose major threats for the local population, particularly for Kayseri metropolis at the base of Mt. Erciyes (Friedrichs et al., 2021b).