Young Silicic Magmatism of the Greater Caucasus, Russia, with implication for its delamination origin based on zircon petrochronology and thermomechanical modeling

Significant volumes of rhyolites and granites of the Pliocene-Pleistocene age are exposed in the collision zone of the Greater Caucasus, Russia. The volcanic history of the region includes ignimbrites and lavas associated with the Chegem caldera (2.9 Ma) and Elbrus volcano (1.98 and 0.7 Ma) and rhyolitic necks and granites in Tyrnyauz (1.98 Ma). They are characterized by a similar bulk and mineral composition and close ratios of incompatible elements, which indicates their related origin. The 1.98 Ma Elbrus ignimbrites, compared to the 2.9 Ma Chegem ignimbrites, have elevated concentrations of both compatible (Cr, Sr, Ca, Ni) and incompatible elements (Cs, Rb, U). We argue that the Elbrus ignimbrites were produced from magma geochemically similar to Chegem rhyolites through fractionation crystallization coupled with the assimilation of crustal material. The 1.98 Ma Eldjuta granites of Tyrnyauz and early ignimbrites of the Elbrus region (1.98 Ma) are temporally coeval, similar mineralogically, and have comparable major and trace element composition, which indicates that the Elbrus ignimbrites probably erupted from the area of modern Tyrnyauz; the Eldjurta granite could represent a plutonic reservoir that fed this eruption. Late ignimbrites of Elbrus (0.7 Ma) and subsequent lavas demonstrate progressively more mafic mineral assemblage and bulk rock composition in comparison with rhyolites. This indicates their origin in response to the mixing of rhyolites with magmas of a more basic composition at the late stage of magma system development. The composition of these basic magmas may be close to the basaltic trachyandesite, the flows exposed along the periphery of the Elbrus volcano. All studied young volcanic rocks of the Greater Caucasus are characterized by depletion in HSFE and enrichment in LILE, Li, and Pb, which emphasizes the close relationship of young silicic magmatism with magmas of suprasubduction geochemical affinity. An important geochemical feature is the enrichment of U up to 8 ppm and Th up to 35 ppm. The trace element composition of the rocks indicates that the original rhyolitic magma of Chegem ignimbrites caldera was formed at >80%–90% fractionation of calc-alkaline arc basalts with increased alkalinity. This observation, in addition to published data for isotopic composition (O-Hf-Sr) of the same units, shows that the crustal isotopic signatures of silicic volcanics may arise due to the subduction-induced fertilization of peridotites producing parental basaltic magmas before a delamination episode reactivated the melting of the former mantle and the lower crust.

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INVESTIGATION OF EROSION RESISTANCE OF GRAY-BROWN SOILS IN THE SOUTHEASTERN SLOPES OF THE GREATER CAUCASUS

Natural resources of the Earth and environmental protection ◽

10.26787/nydha-2713-203x-2020-1-7-8-9-47-49 ◽

2020 ◽

pp. 47-49

Author(s):

Aliyev Z.H.

Keyword(s):

Erosion Resistance ◽

Preventive Measures ◽

Chemical Properties ◽

Anthropogenic Factors ◽

Erosion Process ◽

Greater Caucasus ◽

Sloping Lands ◽

Set Up ◽

Physical And Chemical ◽

And Chemical Properties

In recent years, sharp changes have occurred in the state of sloping lands of Azerbaijan. There was tension from the influence of the anthropogenic factors on the mountain slopes. The fact that the erosion process is rein-forced in the research site. Due to lack of agrotechnical measures on the slopes erosion process has been strength-ened, soil flooded with soil, physical and chemical properties of the soil have deteriorated, nutritional elements are reduced, vegetation is reduced and destruction limit. For some reason, the purpose of the research was Aqsu, two land cuts were set up to determine the degree of actual erosion in the Qizmeydan village. prevent erosion intensity, take preventive measures to take and implement appropriate measures.

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The Zirconometry and Thermochronology of Migmatized Gneisses of the Gondaray Metamorphic Complex (Greater Caucasus)

Moscow University Geology Bulletin ◽

10.3103/s014587522005004x ◽

2020 ◽

Vol 75 (5) ◽

pp. 481-495

Author(s):

V. Yu. Gerasimov ◽

V. A. Snezhko ◽

J. Mosar ◽

A. N. Pismennyi ◽

N. L. Enna ◽

...

Keyword(s):

Metamorphic Complex ◽

Greater Caucasus

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Sphagnum mosses (Sphagnaceae, Bryophyta) of mires Chefandzar and Masota in North Ossetia (Caucasus)

Novosti sistematiki nizshikh rastenii ◽

10.31111/nsnr/2018.52.2.455 ◽

2018 ◽

Vol 52 (2) ◽

pp. 455-462 ◽

Cited By ~ 2

Author(s):

G. Ya. Doroshina ◽

I. A. Nikolajev

Keyword(s):

Plant Communities ◽

The Other ◽

North Caucasus ◽

Sphagnum Mosses ◽

Greater Caucasus ◽

The North ◽

First Time ◽

North Ossetia

Sphagnum mires on the Greater Caucasus are rare, characterized by the presence of relict plant communities of glacial age and are in a stage of degradation. The study of Sphagnum of Chefandzar and Masota mires is carried out for the first time. Seven species of Sphagnum are recorded. Their distribution and frequency within the North Caucasus are analyzed. Sphagnum contortum, S. platyphyllum, S. russowii, S. squarrosum are recorded for the first time for the study area and for the flora of North Ossetia. The other mosses found in the study area are listed.

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Materials to the lichen flora of Samurskiy Ridge (high mountainous Dagestan)

Novosti sistematiki nizshikh rastenii ◽

10.31111/nsnr/2018.52.2.397 ◽

2018 ◽

Vol 52 (2) ◽

pp. 397-406

Author(s):

A. B. Ismailov ◽

G. P. Urbanavichus

Keyword(s):

North Caucasus ◽

Lichenicolous Fungi ◽

Greater Caucasus ◽

Altitudinal Range ◽

The North ◽

New Findings ◽

Mountainous Landscapes ◽

First Time ◽

Lichen Flora

The lichens and lichenicolous fungi of high mountainous landscapes of Samurskiy Ridge were studied in altitudinal range 2400–3770 m a. s. l. for the first time and 112 species are recorded. Among them 33 species, 10 genera (Arthrorhaphis, Baeomyces, Calvitimela, Epilichen, Lambiella, Psorinia, Rufoplaca, Sagedia, Sporastatia, Tremolecia) and 4 families (Anamylopsoraceae, Arthrorhaphidaceae, Baeomycetaceae, Hymeneliaceae) are new for Dagestan, six species (Buellia uberior, Carbonea atronivea, Lecanora atrosulphurea, Lecidea fuliginosa, L. swartzioidea, Rhizoplaca subdiscrepans) are reported for the first time for the Greater Caucasus and two species (Acarospora subpruinata and Rhizocarpon postumum) — for the North Caucasus. Most of the new findings were collected from 3500–3770 m a. s. l.

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