عنوان مقاله [English]
The Plio-Quaternary calc-alkaline magmatism in Azerbaijan, northwest Iran, occurs as stratovolcanoes, lava flows and domes consisting of andesitic basalts, andesites, dacites, rhyodacites, and pyroclastic materials. The volcanic rocks unconformably cover the Miocene sedimentary formations. The chemistry of the felsic-intermediate volcanic rocks indicates that the parent magmas are medium-K calc-alkaline and metaluminous in nature, and are distinguished by Na2O/K2O> 1. The volcanic rocks are enriched in LILE and LREE, and depleted in Y, Nb, and HREE, and display highly fractionated REE patterns, with no Eu anomaly. They display post-collision and continental margin arcs affinities. The post collision convergence between Arabia and Eurasia continental plates, starting in Miocene, resulted in significant shortening, thickening, and uplift of the crust in northwestern Iran and eastern Turkey, and shaped the present Iran-Turkey Plateau.
The thermal perturbation processes in the underlying asthenospheric mantle led to partial melting at a low degree, producing alkali- basalt magmas, with garnet remaining stable in the source region. The ascent of the basaltic magma and its emplacement in the lower crust resulted in the partial melting of the crustal materials and development of acidic magma. These processes led to the ascent and eruption of the felsic magmas prior to the mafic magmas. Mixing of mantle-derived mafic magmas with felsic magmas of crustal origin, produced hybrid magmas of intermediate composition. The occurrence of inverted volcanic sequences, where olivine-alkaline basalts are underlain by calc-alkaline felsic-intermediate rocks, are typical features of bimodal volcanic activities in the Plio-Quaternary times in Azerbaijan.
There are mineralogical as well as geochemical evidences that AFC-type processes were involved in the evolution of the Plio-Quaternary volcanic rocks in Azerbaijan. A comparison of geological and geochemical characteristics of the Plio-Quaternary volcanic rocks from northwest Iran with those from eastern Turkey indicates that the two areas share similar evolution paths in the petrogenesis of magmatic rocks.
Aramaki , S. , Ui , T. ,1982-Japan , pp. 259-92 in Thorpe (1982).
Ewart, A. , Stipp , J.J., 1968- Petrogenesis of the volcanic rocks of the central North Island , New Zealand as indicated by a study of Sr87/ Sr86 ratio, and Sr,Rb,K,U and Th abundances. G.C.A. 32,699-736.
Gill, j., 1981- Orogenic Andesites and Plate tectonics. Springer, 390 pp.
Green , H., 1982- Anatexis of mafic crust and high pressure crystallization of andesite , pp. 465-87 in Thorpe (1982).
Harmon , R. S. & 8 co- authers,1984- Regional Q., Sr., and Pb- isotope relationships in late Cenozoic calk-alkaline lavas of the Andean Cordillera. J. Geol. Soc. Lond. 141, 803-22.
Ishizaka , K., Carlson , R. W., 1983- Nd – Sr systematics of the Setouchi volcanic rocks , south – west Japan : a clue to the origion of orogenic andesites, E.P.S.L. 64, 327-40.
Karapetian, S.G., Jrbashian, R.T., Mnatsakanian, A.K. H., 2001- Late collision rhyolitic volcanism in the north-eastern part of the Armenia highland. Journal of Volnanogy and geothermal Research 12, 189-220-
Keskine, M. , Pearce, J. A. , Mitchell , J.g. , 1998- Volcano – Stratigraphy and geochemistry of Collision – relatd Volcanism on the Erzrum – kars Plateau, northeastern Turkey. J. of Volcanology
Le Bas, M. j., Le maitre, R. W., Streckeisen, A., Zanettin, B., 1986- A chemical classification of Volcanic rocks based on the total alkal – silica diagram. J Petrol 27,745-750
Le Maitre, R.W., Bateman, P., Dudek, A., Keller, J., Le Bas, M.J., Sabine, P.A., Schmid , R., Sorenson, H., Streckeisen, A., Wooly, A.R., Zanettin, B., 1989- A classification of Igneous Rocks and Glossary of Terms. Blackwell, Oxford, 193 pp.
Mccurt, W.J., Atherton, M. P., Sanderson, L. M., Warden, V., 1985- The volcanic cover chemical composition and the origion of the magma of the calipuy. ( In magmatism at a plate edge ) .273-284-
McDonough, W.F. , Sun, S. , Ringwood, A.F. , Jagoutz, E. & Hofmann, A.W., 1991 - K , Rb, and Cs in the earth and moon and the evolution of the earth,s majtle. Geochim. Cosmochim. Acta, Ross Taylor Symposium Volume.
Middlemost, E. , A. K., 1975 - The Basalt Clan. Earth-Science Reviews, 11, 337-364.
Muller, D., Groves, D.I.,1997-Pottasic rocks and associated gpld-copper mineralization,Sec. Updated. Springer-Verlag.242 pp.
Pearce, J.A., Bender, J.F., De Long, S.E., Kidd, W.S.F., Low, P.J., Guner, Y., Saroglu, F., Yilmaz, Y., Morbath, S., Mitchell, J.J., 1990- Genesis of collision volcanism in eastern Anatolia Turkey. J. Volcano. Geothem. Res. 189-229.
Pearce, J. A., 1983- Role of the sub – continental lithosphere in magma genesis at active Continental margines, In: Hawkes worth, C. J., Norry, M. J. (Eds). Continental Basalts and Mantle Xeno- lites – Shira, Nontwich, PP. 230-249-
Peccerillo, A., Taylor, S. R., 1976a- Geochemistry of Eocana Calc – alkaline volcanic rocks from the Kastomonon area northern turkey. Contrib. Mineral . Petrol . , No . 58 , 63-81.5
Pichler, H. , Zeil , W., 1972-The Cenozoic rhyolite- andesite association of the Chilean Andes , Bull. Vol. 35-424-52-
Rollinson, H. , 1993- Using geochemical data: evaluation. Presentation , interpretation. Singapore. Ongman, 352 p.
Ryabchikov, I.D., Babansky, A. D. & Dmitriev, Y. L., 1982- Genesis of calk – alkaline magmas : experiments with partial melting of mixed sediments and basalts from the Middle America trench , Southern Mexico transect , Init. Rep. Deep Sea Drilling Proj. 66, 669-702.
Shand , S.J., 1979- Eruptive rocks, their genesis, composition, classification and their relation to ore deposite. John Wiley and Sons, 448p.
Stern, R. J. & ITO, E., 1983- Trace element and isotopic constraints on the source of magmas in the active Volcano and Mariana island arcs. Western Pacific , J. Vol. Geotherm. Res. 18. 461-82.