Geochemical investigations of Miocene-initiated volcanism of the Erciyes Corridor, Central Anatolia, Turkey

Smith, Alyssa Kathryn (2022) Geochemical investigations of Miocene-initiated volcanism of the Erciyes Corridor, Central Anatolia, Turkey. Masters thesis, Northern Arizona University.

Text Smith_2022_geochemical_investigations_miocene-initiated_volcanism_erci.pdf - Published Version Download (2MB)

Abstract

The Erciyes Corridor lavas erupted from a suite of Miocene stratovolcanoes at the northeastern extent of the Central Anatolian Volcanic Province in central Turkey. Previous workers have hypothesized that volcanism in the Central Anatolian Volcanic Province was initiated by rollback of the Cyprus slab following flat-slab subduction. Recent geochemical investigations have focused predominantly on Quaternary CAVP volcanism, whereas Erciyes Corridor lavas may have accompanied the beginning of slab rollback. New geochemical data are presented here for the Erciyes Corridor lavas, including major and trace elements, Pb and Hf isotopes, and petrographic thin section observations. These data have been used to characterize the Erciyes Corridor volcanoes, to determine potential mantle source components for these centers, and to evaluate how mantle source contributions may have evolved with slab rollback. Erciyes Corridor lavas range from basalt to dacite (~48 to 67 wt. % SiO2), with most lavas being evolved (≥ 52 wt. % SiO2). These lavas are predominantly calc-alkaline, enriched in LREE with respect to HREE, and depleted in HFSE with respect to mantle values. REE patterns of basalts and evolved lavas cross, as represented by lower La/Yb values in basalts as compared to evolved lavas (La/YbN ~ 3 to 5 in basalts, ~ 5 to 14 in evolved lavas) at comparable values of Dy/Yb (Dy/YbN ~ 1.2 to 1.3 in basalts, ~ 1.0 to 1.3 in the evolved lavas). This, combined with isotopic differences e.g., higher 206Pb/204Pb, lower Δ7/4, Δ8/4 in some basalts), suggest the Erciyes Corridor basalts were sourced differently from the evolved lavas. The Erciyes Corridor basalts are similar overall to other basalts from the Central Anatolian Volcanic Province with respect to alkalinity and mantle-normalized trace element patterns. Subtle trace element differences, such lower Th/Yb, Nb/Yb, Ce/Y, and higher Zr/Nb, distinguish the Erciyes Corridor basalts from other Central Anatolian Volcanic Province basalts. Values for these ratios show that the Erciyes Corridor basalts likely were sourced predominantly from a depleted, MORB-like upper mantle under Central Anatolia with lesser contribution from a sediment-modified mantle component. Evolved Erciyes Corridor lavas can be subdivided into two groups based on their isotopic characteristics. Group 1 lavas have lower Δ7/4 and Δ8/4 values and a narrow range in ?Hf values, which could reflect differentiation via closed type-system crystal fractionation with negligible crustal contamination. Modeling shows that Group 1 dacitic compositions could potentially be derived from Group 1 basaltic andesites via crystal fractionation of a mineral assemblage containing plagioclase, orthopyroxene, clinopyroxene, and hornblende ± small amounts of apatite or titanite. Alternatively, Group 1 evolved lavas may have been derived from basaltic melts similar to those in other Central Anatolian eruptive centers. Group 2 lavas may have been generated by fractionation of the same mineral assemblage, accompanied by crustal assimilation. If, as proposed, the evolved Group 1 lavas differentiated in a nearly closed system, these same trace element ratios show that their mantle source was dominated by a sediment-modified upper mantle component. Significantly, the Erciyes Corridor basalts do not require incorporation of a deeper, OIB-like intraplate-like mantle component, in contrast to some Quaternary basalts from the Central Anatolian Volcanic Province. The predominance of the ambient upper mantle component and lack of the deeper component in the Miocene-aged Erciyes Corridor lavas could reflect early stages of flat slab rollback in Central Anatolia; incorporation of the deeper component in younger lavas could then represent the progression of rollback-driven convection over time.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Geochemistry; Igneous Petrology; Volcanism; Erciyes Corridor
Subjects:	Q Science > QE Geology
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > School of Earth Sciences and Environmental Sustainability
Date Deposited:	01 Jun 2023 16:21
Last Modified:	25 May 2024 08:30
URI:	https://openknowledge.nau.edu/id/eprint/5933

Actions (login required)

IR Staff Record View

Downloads