Late Pleistocene eruptive recurrence in the post-collisional Mt. Hasan stratovolcanic complex (Central Anatolia) revealed by zircon double-dating

https://doi.org/10.1016/j.jvolgeores.2020.107007Get rights and content

Highlights

  • New population-based disequilibrium corrections improved (U–Th)/He age accuracy.

  • Late Pleistocene recurrence of at least one eruptive phase every 5–15 ka at Mt. Hasan.

  • Eruptive fluxes presented as differential volumes vs. ages to accent recent trends.

  • Long- and short-term fluxes of post-collisional volcanism similar to arc settings.

  • Protracted zircon crystallization supports Mt. Hasan as an active volcanic center.

Abstract

Mt. Hasan (3262 m) is the second highest stratovolcano in Central Anatolia, Turkey, and is considered active based on a ca. 9 ka explosive summit eruption that was arguably depicted in a Neolithic mural at the nearby Çatalhöyük archaeological site. Besides evidence for Holocene activity of Mt. Hasan, its eruptive chronostratigraphy and hazard potential remain poorly constrained. Here, we apply (U–Th)/He thermochronology in combination with U–Th–Pb crystallization ages (zircon double-dating), including a novel population-based approach to disequilibrium correction of (U–Th)/He data, in an attempt to determine the eruption ages of strategically sampled lavas and pyroclastic deposits and to refine the Late Pleistocene chronostratigraphy of Mt. Hasan.

During the Late Pleistocene, Mt. Hasan erupted multiple interfingering andesitic lava flows along with block-and-ash-flows. Seven of these lava flows, typically the stratigraphically youngest in a particular segment around the two central vents of the volcano, yielded Late Pleistocene eruption ages between 91.9 ± 3.9 and 18.1 ± 2.4 ka (uncertainties stated at 1σ). An even younger block-and-ash-flow was deposited on the western flank of the volcano at 13.5 ± 1.5 ka, which together with a ca. 9 ka small-volume explosive summit eruption define the youngest activity at the main edifice of Mt. Hasan. Collectively, these data indicate a Late Pleistocene recurrence of at least one eruptive phase every ca. 5–15 ka. New volume estimates for the Quaternary edifice of ~130–180 km3 translate into an integrated long-term eruptive magma flux of ~0.3 km3/ka, which is just slightly higher than Late Pleistocene flux estimates based on lava flow geochronology and volumes determined by analysis of digital elevation models. This long-term eruptive flux estimate is similar to those of stratovolcanoes in continental arcs, indicating that eruptive productivity in post-collisional settings can match that of active continental margins. All Mt. Hasan eruptions, including the Holocene event, sampled zircon which crystallized coeval with earlier eruptive phases, indicating longevity of the magma plumbing system. Along with ongoing fumarole activity and evidence for mid-crustal low seismic velocity zones, this suggests that a subvolcanic magma reservoir remains active to the present day.

Introduction

Holocene eruption ages recently reported for the Central Anatolian Volcanic Province (CAVP) in Turkey (Sarıkaya et al., 2019; Schmitt et al., 2014) are intriguing evidence that the CAVP's major stratovolcanic complexes – Mt. Erciyes and Mt. Hasan – are active. For Mt. Hasan, the ca. 9 ka age of andesitic pumice fall-out from its summit region along with its twin-peak shape support the notion that the volcano is depicted in a coeval Neolithic mural at Çatalhöyük archaeological site ~130 km to its southwest (Schmitt et al., 2014). More recently, a ca. 2 ka age has been reported for a cinder cone in the west of the main edifice of Mt. Hasan (Dogan-Kulahci et al., 2018). While these data indicate Holocene activity at Mt. Hasan, its Middle to Late Pleistocene chronostratigraphy has remained poorly constrained. This is primarily due to the limited availability of suitable geochronometers applicable to young, intermediate to evolved volcanic rocks when materials preferentially targeted in geochronology such as K-feldspar (for 40Ar/39Ar dating) or charcoal (for 14C dating; <50 ka) are absent, as is the case for Mt. Hasan.

Here, we reconstruct the eruptive evolution of Mt. Hasan's main edifice prior to the Holocene summit eruption (Schmitt et al., 2014) using zircon double-dating (ZDD; Danišík et al., 2017b). ZDD combines U–Th disequilibrium and/or U–Pb zircon crystallization ages with (U–Th)/He cooling ages, where the latter require corrections for initial 238U–230Th disequilibrium and pre-eruptive crystal residence in order to determine ZDD eruption ages accurately (e.g., Danišík et al., 2012; Schmitt et al., 2010). Our new population-based approach to disequilibrium corrections accounts for both rim crystallization ages of individual zircon crystals selected for (U–Th)/He dating and crystallization age differences between zircon rims and interiors of a large set of Mt. Hasan zircon crystals (Friedrichs et al., 2020). The ZDD method has great potential, beyond just the current study, in precisely and accurately dating young intermediate to evolved volcanic rocks, in which zircon is commonly present as an easily recoverable accessory mineral that is, moreover, physically and chemically outstandingly robust. Based on the newly determined ZDD eruption ages and lava flow volumes, Late Pleistocene eruptive fluxes are estimated for Mt. Hasan and compared with its long-term flux integrated over the late Quaternary and with fluxes of other volcanic systems in continental subduction and post-collisional settings.

Section snippets

Regional setting

The CAVP (Fig. 1) is a major focus of post-collisional volcanism in Turkey (e.g., Kuşcu and Geneli, 2010). Its most prominent eruptive products are the Cappadocian ignimbrites formed between ca. 10 and ca. 2.5 Ma (Aydar et al., 2012) covering an area of 20000 km2 (Le Pennec et al., 1994) mostly to the northeast of the study area. In the late Quaternary, eruptive activity became concentrated in basaltic or compositionally bimodal volcanic fields (e.g., Di Giuseppe et al., 2018; Schmitt et al.,

Samples

Eight out of 17 Mt. Hasan samples with zircon crystallization dated by secondary ion mass spectrometry (SIMS) in Friedrichs et al. (2020) were selected for (U–Th)/He dating (Table 1). Samples comprise seven andesite lava flows and one prismatically jointed block from a block-and-ash-flow deposit. They were collected over the entire edifice of Mt. Hasan, strategically targeting the stratigraphically youngest units in different sectors around BMH and SMH (Fig. 2).

Zircon U–Th–Pb and (U–Th)/He double-dating

All samples were excavated from

Zircon eruption and crystallization ages

Replicate analyses (n between 8 and 12 for all samples) yielded mostly uniform (U–Th)/He age populations, with only two obvious outliers (Table A.1, Fig. 4A, G). For these outlier crystals, a xenocrystic origin is likely where He remained trapped in gas inclusions (Danišík et al., 2017a; Stockli et al., 2000), or in the zircon crystal lattice when heating during eruption was insufficient to completely degas previously accumulated He (Blondes et al., 2007; Schmitt et al., 2011). For Late

Chronostratigraphy of Mt. Hasan

A refined Late Pleistocene chronostratigraphy is proposed for Mt. Hasan (Table 1) based on internally consistent ZDD results presented in Section 4.1 and Schmitt et al. (2014). The ZDD eruption ages for the southern SMH lava flow previously assigned to the Mesovolcano stage (17-BF-01; Fig. 2; Aydar and Gourgaud, 1998) and one of the morphologically youthful northern SMH lava flows (17-BF-08) define eruptive activity around SMH from >90 to ca. 40 ka (Table 1). Based on these data, at least some

Conclusions

A refined Late Pleistocene chronostratigraphy of the Mt. Hasan stratovolcanic complex is presented based on ZDD eruption ages for a strategically sampled set of Mt. Hasan lavas and pyroclastic deposits. A novel population-based estimate of crystallization age differences between zircon interiors and rims was applied to improve disequilibrium corrections of (U–Th)/He ages. The results confirm that the most recently active eruptive center was located in the BMH summit region, which experienced an

Data availability

SIMS zircon U–Th disequilibrium and U–Pb data related to this article can be found at https://doi.org/10.1016/j.dib.2020.105113, a Data Article in Data in Brief (Friedrichs et al., 2020).

CRediT authorship contribution statement

Bjarne Friedrichs: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Data curation, Writing – original draft, Visualization, Funding acquisition. Gokhan Atıcı: Conceptualization, Resources, Writing – review & editing, Supervision, Project administration, Funding acquisition. Martin Danišík: Methodology, Validation, Formal analysis, Investigation, Writing – review & editing, Funding acquisition. Evren Atakay: Resources. Mehmet Çobankaya: Resources. Janet C. Harvey:

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

We thank Anne Sturm, Adam Frew, Chris May, and Cameron Scadding for help with zircon separation and dissolution as well as ICP-MS measurements, and Elife Akgül for assistance during field work. Comments by Holli Frey and Erik Klemetti are appreciated. This work was supported by DFG (German Research Foundation) grant SCHM2521/3-1, MTA (General Directorate of Mineral Research and Exploration of Turkey), and a DAAD (German Academic Exchange Service) doctoral scholarship to BF. MD was supported by

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