The role of fractional crystallization in the evolution of magma of the Upper Cretaceous volcanic and subvolcanic rocks from the Nageleh Sar Syncline, south Mahmood Abad, North Iran

Author

Abstract

The Upper Cretaceous volcanic and subvolcanic rocks from the Nageleh Sar, south of Mahmood Abad town in north Iran are dolerite, olivine basalt, trachyandesite and alkali trachyte. These units in an ordered stratification are set in a way that creates a syncline with WNW-ESE axial trend. The chemical data and discrimination diagrams represent medium alkaline bimodal series for the studied samples. REE and incompatible trace elements patterns indicate that they mostly originated from a mantle source similar to OIB with orthopyroxene, clinopyroxene, and olivine in terms of mineralogical content. Variation diagrams and patterns on spider diagrams imply that the parental magma evolved by dominant process of fractional crystallization. The diagrams of major and trace elements ratios clearly show that fractionated phases are often clinopyroxene, amphibole, iron, and titanium oxides. The generating magma of these rocks has been contaminated by crustal materials to some extent and emplaced in an intercontinental rift setting.

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[1] آقا‌نباتی ع.، "زمین‌شناسی ایران"، سازمان زمین‌شناسی و اکتشافات معدنی کشور، (1385) 619 ص.

[2] Alavi M., “Tectonic map of the Middle East”, Geological Survey of Iran, Tehran, (1991).

[3] وحدتی دانشمند ف.، "تلفیق و به طور بخشی بازنگری و تکمیل نقشه و گزارش ورقه 100000/1 آمل"، سازمان زمین‌شناسی و اکتشافات معدنی کشور، (1378).

[4] Miyashiro A.I., “Volcanic rock series in island arcs and active continental margins”, American Journal of Science. 244 (1974) 324-335.

[5] Winchester J.A., Floyd P.A., “Geochemical discrimination of different magma series and their differentiation products using immobile elements”, Chemical Geology 20 (1977) 325–343.

[6] Rollinson H.R., “Using geochemical data: evaluation, Presentation, interpretation”, Longman Scientific & Technical (1993) 322 pp.

[7] Wilson M., “Igneous petrogenesis”, Unwin Hyman, (1989) 466 pp.

[8] Cocherie A., “Systematic use of trace element distribution pattern in log-log diagrams for plutonic suite”, Geochimica et Cosmochimica Acta 50 (1986) 2517–2522.

[9] Mc Donough W.F., Sun S.S., “Composition of the Earth”, Chemical Geology 120 (1995) 223-253.

[10] McDonough W.F., Sun S., Ringwood A.E., Jagoutz E., Hoffman A.W., “K, Rb, and Cs in the earth and moon and the evolution of the earth’s mantle”, Geochimica et Cosmochimica Acta, Ross Taylor Symposium volume (1991).

[11] Pearce J.A., Norry M.J., “Petrogenetic implications of Ti, Zr, Y and Nb variations in volcanic rocks”, Contribution to Mineralogy and Petrology, 69 (1979) 33-47.

[12] Thirlwall M.F., Smith T.E., Graham A.M., Theodorou N., Hollings P., Davidson J.P., Arculus R.J., “High field strength element anomalies in arc lavas; source or process?”, Journal of Petrology 35 (3) (1994) 819–838.

[13] Tribuzio R., Tiepolo M., Vannucci R., Bottazzi P., “Trace element distribution within olivine-bearing gabbros from the Northern Apennine ophiolites (Italy): evidence for post-cumulus crystallization in MOR-type gabbroic rocks”, Contributions to Mineralogy and Petrology 134 (1999) 123–133.

[14] Nielsen R.L., Forsythe L.M., Gallahan W.E., Fisk M.R., “Major- and trace element magnetite-melt equilibria”, Chemical Geology 117 (1994) 167–191.

[15] Boztug˘ D., Harlavan Y., Jonckheere R., Can I, Sari R., “Geochemistry and K-Ar cooling ages of the Ilıca, C¸ ataldag˘ (Balıkesir) and Kozak (I˙zmir) granitoids, west Anatolia, Turkey”, Geological Journal 44 (2009) 79–103.

[16] Aldanmaz E., Pearce J.A., Thirlwall, M.F., Mitchell J.G., “Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey”, Journal of Volcanology and Geothermal Research 102 (2000) 67-97.

[17] Pearce J.A., Bender J.F., De Long S.E., Kidd W.S.F., Low P.J., Güner Y., Şaroğlu F., Yılmaz Y., Moorbath S., Mitchell J.J., “Genesis of collision volcanism in eastern Anatolia Turkey”, Journal of Volcanology and Geothermal Research 44 (1990) 189–229.

[18] Sun S.S., “Lead isotopic study of young volcanic rocks from mid-ocean ridges, ocean islands and island arcs”, Philosophical Transactions of the Royal Society of Scotland A297 (1980) 409-445.

[19] Jahn B.M., Wu F.Y., Lo C.H., “Crust–mantle interaction induced by deep subduction of the continental crust: geochemical and Sr–Nd isotopic evidence from post collisional mafic–ultramafic intrusions of the northern Dabie Complex, Central China”, Chemical Geology 157 (1999) 119–146.

[20] Cabanis B., Lecolle M., “Le diagramme La/10-Y/15-Nb/8: un outil pour la discrimination des series volcaniques et la mise en evidence des processus de melange et/ou de contamination crustale”, C.R.Acad. Sci. Ser. II. 309 (1989) 2023-2029.

[21] Wang Y., Zhang C., Xiashuzhi B., “Th/Hf -Ta/Hf discrimination diagram of geotectonic settings of formation of basalts”, Acta petrologica sinica.17 (2001) 413-421(in Chinese with English abstract).