The origin and tectonomagmatic setting of dykes at the North of Mashhad-Ardehal

A suite of dykes at the north of Mashad –Ardehal which intruded into the Eocene volcanic and sedimentary rocks represents part of Tertiary volcanism in middle part of the Urumieh-Dokhtar magmatic belt. The rocks are cogenetic and are mainly basaltic andesite, andesite and trachy andesite in composition and belong to tholeiitic and medium-K calc alkaline series. Chondrite-normalized REE patterns exhibit moderate enrichment in LREE relative to MREE. Enrichment in LILE and depletion in HFSE relative to REE on multi-element diagrams is similar to subduction related magmatic rocks. From the geochemical point of view, these rocks demonstrate intermediate characteristics of active continental margins and island arcs settings. Geochemical evidences and also association of the magmatic rocks with green tuffite and other shallow marine sedimentary rocks suggest that the rocks generated in an extensional continental (ensialic) back-arc basin.