Lithologic sequence and geochemical characteristics of Second phase of Paleogene volcanic rocks in Deylaman area, Western Alborz

Abstract

Deylaman area lies on Paleogene volcanic rocks in Western Alborz near the border between Central and Western Alborz structural zones. The succession of Paleogene rocks in the area is comprised of three separate phases each of which representing one stage of volcanic events. The main purpose of this paper is to study the lithologic sequence and geochemical characteristics of phase two volcanic rocks with Oligocene age (?). Rocks from the second phase are made of three separate parts (subunits) which by the order of age from the oldest to the youngest are; subunit one: basalts and basaltic andesite lavas, subunit two: coarse and fine grained tuffs and volcanic breccia, subunit three: andesitic tuffs with andesitic lenses. Geochemical studies on major and trace elements of lavas show that these rocks have calc-alkaline characteristic of volcanic arcs. Meanwhile, there are some similarities between REE patterns, for example LREE are more enriched, HREE have flat patterns as well as Eu negative anomalies. Therefore, the magmas of these rocks formed from a garnet-free but feldspar-bearing source. Immobile trace element data such as Cr and Th confirm their volcanic arc origin.

Keywords


[1] آقانباتی ع.، "زمینشناسی ایران"، وزارت صنایع و معادن، سازمان زمینشناسی و اکتشافات معدنی کشور (1385) 619 صفحه.

[2] درویش‌زاده ع.، "زمینشناسی ایران"، مؤسسه انتشارات امیرکبیر (1380) 901 صفحه.

[3] Annells R.N., Arthurton R.S., Bazley R.A., Davies R.G., “Explanatory text of the Qazvin and Rasht Quadrangle Map”, Geol. Surv. Iran, (1975), 94 p.

[4] Stalder P., “Magmatismes tertiaire et subrecent entre Taleghan et Alamout”, Elbourz Central (Iran), Schweiz Min. Petr. Mitt., (1971), v. 51, No. 1, p. 2-138.

[5] Henry C.D., Wolf J.A., “Distinguishing strongly rheomorphic tuffs from extensive silicic lavas”, Bull. Volcanol. (1992), v. 54, p. 171-186.

[6] Wolf J.A., Wright J.V., “Rheomorphism of welded tuffs”, J. Volcanol. Geotherm Res., (1981), v. 10, p. 13-34.

[7] Deer W.A., Howie R.A., Zussmann J., “An introduction to rock-forming minerals”, (1991) Longman, 528 p.

[8] LeBas M.J., Le Maitre R.W., Strekeisen A., Zanettin B., “A chemical classification of volcanic rocks based on the total alkali – silica diagram” , J. Petrol., (1986), v. 27 , p. 745-750.

[9] Kuno H., “Differentiation of basalt magmas”,

In : Hess H.H. and Poldervaart A .(eds.), Basalts : The Poldervaart treatise on rocks of basaltic compositions, vol. 2 , Interscience, New York, (1968), p.623-688.

[10] Irvine T.N., Baragar W. R. A., “A guide to the chemical classification of the common volcanic rocks”, Can , J. Earth Sci., (1971), v.8, p. 523-548.

[11] MacDonald G.A. and Katsura T., “Chemical composition of Hawaiian lavas”, J. Petrol., (1964), v.5.p.83-133.

[12] Barrett T.J., MacLean W.H., “Chemostratigraphy and hydrothermal alteration in exploration for VHMS deposits in greenstones and younger volcanic rocks, in: Alteration and alteration processes”, Lentz D.R. (ed.): Geological Association of Canada, Short Course Note 11, (1999), p. 433-467.

[13] Sun S.S., McDonough W.F., “Chemical and isotopic systematic of oceanic basalts: implication for mantle composition and processes”, In: Sunders A.D. and Norry M.J. (eds) magmatic in oceanic basins. Geol. Soc. London. Spec. Publication 42, (1989), p. 313-345.

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

[15] Taylor S.R., McLennan S.M., “The continental crust: its composition and evolution”, Blackwell, Oxford (1985).

[16] Rollinson H.R., “Using geochemical data: evaluation, presentation, interpretation”, Longman Scientific & Technical, (1993), 322 p.

[17] Wilson M., “Igneous petrogenesis”, Unwin Hyman, (1989), 421 p.

[18] Kaur P., Chaudhri N., Okrusch M., Koepke J., “Paleoproterozoic A – type felsic magmatism in the Khetri copper belt, Rajasthan, northwestern India, petrologic and tectonic implication”, Contr. Mineral. Petrol., (2006), v. 87, p. 81-122.

[19] Wood D.A., “The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary volcanic province”, Earth Planet. Sci. Lett., (1980), v. 50, p. 11-30.

[20] Pearce J.A., “Trace element characteristics of lavas from destructive plate boundaries”, In:





Thorpe R.S. (ed.), Andesites, Wiley Chichester, (1982), p. 525-548.

[21] آسیابانها ع. ، "زمینشناسی و پتروژنز رخسارههای آتشفشانی منطقه یوزباشیچای (غرب قزوین)". رساله دکتری، دانشگاه تربیت مدرس، دانشکده علوم پایه، (1380)321 صفحه.