On the basis of microprobe, chemical and X-ray diffractometric analyses, the petrogenetic features of the formation of picrites depending on еруcompositional variability of clinopyroxenes in the Lesser Caucasus and Talysh zone were studied. The Upper Jurassic picrites of the Murovdag anticlinorium were formed under similar geological and geodynamic conditions, while being controlled by the rift-type crack structure. Therefore, the petrographic type of rocks involved in the anticlinorium is homogeneous. Clinopyroxene megacrysts in subalkaline picrites in the Khojavend bend correspond to chromium diopside partially depleted in titanium oxide. Clinopyroxenes are included as phenocrysts, normal prismatic and megacrysts in the Santonian trachybasalt-trachydolerite, tephrite-teschenite complexes of the Khojavend synclinorium. The contact zone is noticeable in its parent rock. In the Talysh zone, the picrites belong to the subalkaline series and have a characteristic clay structure, and their main masses are dolerite and subdolerite. Along with olivine, clinopyroxene phenocrysts are present in the contents. Those phenocrysts in most cases form large elongated, sometimes plate-like crystals. In most cases, they are colorless. However, olivine and chromspinel inclusions of different sizes are observed in them. Rather large prismatic phenocrysts of clinopyroxenes are included in phlogopite and olivine picrites. These phenocrysts are xenomorphic to olivine. The composition of clinopyroxenes in the picrites of Talysh zone corresponds to diopside-salite. Thus, the change in the composition of picroxenes in picrites of the Lesser Caucasus and Talysh zone is regulated by crystallization differentiation.

Keywords: The Lesser Caucasus, Taliysh zone, picrite, zoned pyroxene, crystallization differentiation

REFERENCES

Azizbekov Sh.A., Bagirov A.E., Veliyev M.M., Ismail-Zade A.D., Nizheradzhe N.S., Emelyanova E.N., Mamedov M.N. et al. Geology and volcanism of Talysh. Nauka. Moscow, 1979, 241 p. (in Russian).

Dobretsov N.L., Kochkin Yu.N., Krivenko A.P., Kutolin V.A. Rock-forming pyroxenes. Nauka. Moscow, 1971, 455 p. (in Russian).

Mamedov M.N. Evolution of alkaline basic magmatism in the structures of the Talysh block (southeastern Azerbaijan). In: Evolution of magmatism of the main structures of the Earth, Moscow, 1983, p. 41 (in Russian).

Mamedov M.N., Babayeva G.J., Sadygov N.M. Clinopyroxenes of trachybasalt-trahydoleryte and tephrite-teschenite complexes of the Khojavend trough. Otechestvennaya geologiya, No. 6, 2012, pp. 48-55 (in Russian).

Mammedov M.N., Babayeva G.J., Kerimov V.M. Clinopyroxenes in formation process of sub-alkalic olivine-basalt magma of the Talysh zone of Caucasus. Uralian Geological Journal, No. 5, 2017, pp. 39-53 (in Russian).

Rustamov M.I. Geodinamics and magmatism of the Caspian-Сaucasus segment of the Mediterranean belt of the Phanerozoic. Nafta-Press. Baku, 2019, 543 p. (in Russian).

Shikhalibeyli E.Sh. Geology and minerals of Nagorno-Karabakh of Azerbaijan. Baku, 1994, 284 p. (in Russian).

Kushiro I. Clinopyroxene solid solutions. Part I. The CaAl₂SiO₂ component. Jap. J. Geol. Geogr., No. 33, 1962, pp. 213-220.

Le Bas M.J., Le Mitre R.W., Streckeisen A., Zanettin B. A chemical classification of volcanic rocks based on the total alkali-silica (TAS) diagram. J. Petrol., Vol. 27, 1986, pp. 745-750, http://doi.org/10.1093/petrology/27.3.745/.

Lindsley D.H. Pyroxene thermometry. American Mineralogist, Vol. 68(5-6), 1983, pp. 477-493.

Morimoto N. Nomenclature of pyroxenes. Mineralogy and Petrology, Vol. 39, 1988, pp. 55-76, http://dx.doi.org/10.1007/BF01226262.

Rohrbach A., Schuth S., Ballhaus C., Miinker C., Matveev S., Qopoto C. Petrological constraints on the origin of arc picrites, New Georgia Group, Solomon Islands. Contrib Mineral Petrol, No. 149, No. 6, 2005, pp. 685-698, http://doi.org/10.1007/S00410-0675-6.