Document Type : Original Research Paper

Authors

1 Departmant of Geology, Islamic Azad University, Shabestar Branch,Shabestar,Iran.

2 Departmant of Geology, Tabriz University, Tabriz, Iran.

3 Institute of Earth Sciences, Academia Sinica, Taiwan

4 Departmant of Geology, Istanbul University, Istanbul,Turkey

Abstract

In southeast Tabriz, as a part of Western Albourz-Azarbaijan magmatic belt the vocanic and pyroclastic rocks of Sahand cover vast areas. The volcanic rocks include andesite, dacite, rhyodacite and rhyolite and pyroclastic rocks largely occur as vast ignimbritic outcrops. Based on high LILE/HFSE and LREE/HREE ratios and their similar composition to subduction volcanic rock suites; it seems that they have formed in a subduction zone. The subduction process had low effect on the concentration of Zr, Ta, Hf, Sm, Tb, Nd, Eu and Y, while it had strong influence on concentration of Th , U and La. Concentration of elements such as Ba , K , Rb , Cs , Sr , Pb shows that these rocks belong to calc-alkaline series. The studied rocks show considerable similarity with calc-alkaline rocks from Turkey and from this point of view; these rocks belong to post-collisional arcs. In this tectonic setting, magma ascent is controlled by strik-slip faulting and associated pull-apart extensional tectonics. This post-collisional magmatism may have occurred due to Arabian-Iranian plates collision.

Keywords

بهروزی، امینی فضل و امینی آذر، 1376- نقشه زمین‌شناسی 1:100000 بستان آباد، سازمان زمین‌شناسی و اکتشافات معدنی کشور.
 
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