Petrogenesis of Quaternary Shoshonitic Volcanism in NE Iran (Ardabil): Implication for Postcollisional Magmatism

Habib Shahbazi Shiran

doi:10.1155/2013/735498

Abstract

Trachyandesites, trachytes, andesites, and pyrocalstic rocks, with shoshonitic signature, are the main Quaternary volcanic rocks in the Sabalan region (Ardabil). Plagiocalse, K-feldspar, biotite associated with clinopyroxene, and glass are the main constituents of these lavas. Plagioclases are andesine to labradorite while clinopyroxenes have augitic composition. The Sabalan volcanic rocks show enrichment in LREEs (relative to HREEs) and are characterized by enrichment in LILEs and depletion in HFSEs. Petrological observations, along with rare earth and trace elements geochemistry, suggest shoshonitic signature for Sabalan lavas. This signature highlights derivation from a subduction-related source. The Sabalan volcanic rocks are isotopically characterized by derivation from an enriched mantle source with a tendency to plot in the fields defined by island-arc basalts (IAB) and OIBs (in εNd versus 87Sr/86Sr diagram). The geochemical and isotopic characteristics of the Sabalan lavas suggest that their magma has been issued via low degree partial melting of a subduction-metasomatized continental lithospheric mantle. The formation of these lavas is related to slab steepening and breakoff in a postcollisional regime.

Highlights

Cenozoic magmatism is well known from the peri-Arabic region, north of the Bitlis-Zagros Suture Zone (Figure 1), and ranges in age from Eocene to Plio-Quaternary
The Eocene magmatism in the peri-Arabic region is calc-alkalic to shoshonitic, which resulted from subduction of the Neotethyan Ocean beneath the central Iranian and Anatolian blocks
The Sabalan Quaternary volcanism includes a sequence of trachyandesites, latites, trachytes with huge bodies of ignimbrites, and pyroclastic rocks

Summary

Introduction

Cenozoic magmatism is well known from the peri-Arabic region, north of the Bitlis-Zagros Suture Zone (Figure 1), and ranges in age from Eocene to Plio-Quaternary. The Plio-Quaternary (and Quaternary) alkaline-ultrapotassic magmatism occupies most of the Turkish-Iranian high plateau (NW Iran and NE Turkey) and is mostly characterized by within-plate and/or subductionrelated geochemical characteristics [3,4,5]. The Turkish-Iranian high plateau is bounded on the north by the Eastern Pontide arc and Lesser Caucasus magmatic belt and to the south by continental blocks including Bitlis, Puturg, Sanandaj, and Sirjan blocks. The Sabalan volcano (Ardabil) is among the youngest volcanic calderas, in eastern border of the Turkish-Iranian Plateau, consisting of Miocene trachyandesites and Plio-Quaternary trachy-andesite, pumiceous andesites, and dacites with ultrapotassic-shoshonitic signatures. The aim of this study is to recognize the major, trace, REE and Sr-Nd isotopes characteristics of the Sabalan Quaternary lavas and to present a consistent tectonomagmatic model for the formation and evolution of the Sabalan volcano

Objectives

Methods

Discussion

Conclusion