Document Type : Original Research Paper
Authors
1 Assistan Professor, Faculty of Earth Science, Kharazmi University, Tehran, Iran
2 Professor, Faculty of Earth Science, Kharazmi University, Tehran, Iran
3 Professor, Faculty of Earth Science, University of Ferrara, Ferrara, Italy
Abstract
Tertiary volcanism in east and northeast of Nehbandan, eastern Iran, includes mostly basic-intermediate associations. They are characterized by sodic (1<Na2O/K2O) compositions and contain both low-k tholeiitic and calk-alkaline series. Based on petrographic, mineral chemistry and whole-rock geochemical evidences basalts can be classified into two groups; arc-related calc-alkaline basalts (CAB) and low-K tholeiites (LKT). The evolutionary trends of some major and trace elements vs. SiO2 and also chondrite-normalized rare earth element (REE) patterns represent gentic relation between low-K tholeiitic intermediates and LKT but reject calkalkaline intermediate generation by magmatic evolution from CAB. In MORB-normalized multi-element patterns, negative anomally of high field strength elements (HFSE) and enrichment of large-ion lithophile elements (LILE) suggest subduction zone-related tectonomagmatic setting for basic-intermediate associations in which compositional change from LKT to CAB is accompanied by the evolution of arc system. This scenario in Sistan suture zone is interpreted as subduction continuation of Sistan oceanic lithosphere in Tertiary.
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