The Thickness of the Mantle Lithosphere and Collision-Related Volcanism in the Lesser Caucasus

Sugden, Patrick; Savov, Ivan P.; Wilson, Marjorie; Meliksetian, Khachatur; Navasardyan, Gevorg; Halama, Ralf

doi:10.1093/petrology/egy111

Cited by 26 publications

(52 citation statements)

References 91 publications

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“…The conspicuous positive Zr-Hf anomaly that has been noted elsewhere in Armenia (Neill et al, 2013) was not picked out here, possibly due to the very incompatible element-enriched nature of the samples. Absolute Zr ranges from 180-207 ppm, with high Zr/Hf ratios of 44-46, matching most other samples with similar SiO2 across Armenia (Sugden et al, 2019 Figure 7. a) Total alkali-silica plot after Le Bas et al (1986) showing Syunik (southern Armenia) and Shirak/Lori (northern Armenia) fields after Sugden et al (2019).…”

Section: Whole Rock Geochemistrysupporting

confidence: 65%

“…Absolute Zr ranges from 180-207 ppm, with high Zr/Hf ratios of 44-46, matching most other samples with similar SiO2 across Armenia (Sugden et al, 2019 Figure 7. a) Total alkali-silica plot after Le Bas et al (1986) showing Syunik (southern Armenia) and Shirak/Lori (northern Armenia) fields after Sugden et al (2019). b) K2O vs. silica classification plot after Peccerillo and Taylor (1976).…”

Section: Whole Rock Geochemistrysupporting

confidence: 65%

“…In this model, low-Ca plagioclase crystals would have to be antecrysts from an earlier but more evolved magma batch. In conclusion, a longer time-span of magmatic activity should be analysed in greater detail in this region, including with radiogenic isotope analyses, to determine if there are genuine systematic changes in partial melting conditions and crustal processing beneath Syunik, in addition to the Armenia-wide work of Sugden et al (2019). Pearce (1983) with fields and vectors from Sugden et al (2019).…”

Section: Whole Rock Geochemistrymentioning

confidence: 99%

“…In conclusion, a longer time-span of magmatic activity should be analysed in greater detail in this region, including with radiogenic isotope analyses, to determine if there are genuine systematic changes in partial melting conditions and crustal processing beneath Syunik, in addition to the Armenia-wide work of Sugden et al (2019). Pearce (1983) with fields and vectors from Sugden et al (2019). The youngest Karkar lavas fall clearly within the Syunik field, whereas the older lavas lie just above this field, similar to Vardenis, the location of the Holocene Porak volcano.…”

Section: Whole Rock Geochemistrymentioning

confidence: 99%

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Pleistocene - Holocene volcanism at the Karkar geothermal prospect, Armenia

Meliksetian¹,

Neill²,

Barfod³

et al. 2020

Preprint

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Pleistocene to Holocene volcanic centres north of the Bitlis-Zagros suture in Turkey, Iran, Armenia and Georgia represent both volcanic hazards and potential or actual geothermal energy resources. Such challenges and opportunities cannot be fully quantified without understanding these volcanoes’ petrogenesis, geochronology and magmatic, tectonic or other eruption triggers. We discuss the age and igneous geology of the Karkar monogenetic volcanic field in Syunik, SE Armenia. The ~30 km^2 field is beside the location of Armenia’s only geothermal energy test drilling site. Eruptions of fissure-fed trachybasaltic andesite to trachyandesite occurred on a trans-tensional pull-apart segment of the Pambak-Sevan-Syunik Fault and have previously been interpreted to be of Holocene age. We conducted high-resolution duplicate Ar/Ar dating of 7 groundmass separates, providing composite plateau or inverse isochron ages ranging from 6 ± 3 ka to 332 ± 9 ka (2σ). Each lava flow displays petrographic and geochemical patterns consistent with melting of subduction-modified lithospheric mantle and crystal fractionation involving ol, sp, opx and cpx, amp and plg. Some crystal-scale zoning was observed, implying recharge prior to eruption, and a preliminary estimate of cpx crystallisation pressures indicates storage in the mid- to upper crust, which may be of relevance for geothermal developments. These data indicate that volcanic activity in Syunik and elsewhere in Armenia overlapped with human occupation and that the presence of a substantive heat source for geothermal energy and a lava inundation hazard for local infrastructure should be further considered. Additional geophysical monitoring of the Pambak-Sevan-Syunik Fault is merited, along with detailed determination of the depths of magma storage both here and also at Porak volcano 40 km north of Karkar.

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Section: Whole Rock Geochemistrysupporting

confidence: 65%

Section: Whole Rock Geochemistrysupporting

confidence: 65%

Section: Whole Rock Geochemistrymentioning

confidence: 99%

Section: Whole Rock Geochemistrymentioning

confidence: 99%

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Pleistocene - Holocene volcanism at the Karkar geothermal prospect, Armenia

Meliksetian¹,

Neill²,

Barfod³

et al. 2020

Preprint

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“…For instance, larger volumes of volcanic rocks around Lake Van-Muş area (Süphan, Nemrut, Tendürek, and Etrüsk) are less than 6 Myr old. In relation to this, our models predict that when the lithosphere peels off from the overlying crust, there is convective mantle circulation; therefore, heating and melting occurs at shallower depths beneath both the foreland (East Anatolia) and hinterland plates (Pontides, Lesser Caucasus in Armenia) (Sugden et al, 2019). Although the depth/distribution of the mantle flow varies (e.g., shallower/near crust under the foreland and deeper lithosphere under the hinterland), such processes can induce decompression related magmas (alkaline magmatism) under both the northern (e.g., Geghema highland Armenia) and southern part of the plateau.…”

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 86%

Long Wavelength Progressive Plateau Uplift in Eastern Anatolia Since 20 Ma: Implications for the Role of Slab Peel‐Back and Break‐Off

Memiş

Gogus

Uluocak

et al. 2020

Geochem Geophys Geosyst

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Stratigraphic evidence is used to interpret that the East Anatolian Plateau with 2 km average elevation today was below sea level ~20 Ma and uplift began in the northern part. The presence of voluminous volcanic rocks/melt production across the plateau—younging to the south—corroborates geophysical interpretations (e.g., high heat flow and lower seismic velocities) that suggest progressive removal of the slab subducting under the Pontides. Here, we conduct numerical experiments that investigate the change in the surface uplift as a response to slab peel‐back and potential break‐off processes under subduction‐accretionary complexes as well as continental lithosphere. Model results show similar types of tectonic behavior and magnitudes of uplift‐subsidence in both oceanic and continental removal processes, and they satisfactorily explain 1.5 km of plateau rise and a ~280 km wide asthenospheric upwelling zone beneath Eastern Anatolia over 18 Myr timescale. Parametric investigation for varying plate strength and convergence velocities show that such model parameters control the amount of surface uplift (1 to 3 km), the width of the asthenospheric upwelling zone, and the potential timing/depth of break‐off of the steepening/peeling slab. Experiments show that slab break‐off develops during the terminal phase, which may correspond to only a few million years ago. Therefore, the long wavelength plateau uplift and magmatism over the Eastern Anatolian‐Lesser Caucasus region since 20 Ma is controlled by progressive slab peel‐back and resulting mantle dynamics. The slab break‐off process (if it happened) has yet an indiscernible role.

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