K- and Na-rich volcanic rocks of Asagi igneous complex, eastern Iran

The Asagi Igneous Complex is located about 160 km northwest of Zahedan in the Sistan Suture Zone, southeast Iran. It is composed of Oligocene, Miocene, and Pliocene extrusive and intrusive igneous rocks. The host rocks of the Asagi Igneous Complex are Cretaceous ophiolite and Eocene sedimentary flysch-type rocks. The Oligo-Miocene extrusive rocks are mainly andesite, trachyandesite, dacite, lithic tuff, ignimbrite, breccia, and the Pliocene extrusive rocks are basalt and andesite basalt. They contain plagioclase, K-feldspar, amphibole, biotite, and pyroxene as the main primary minerals. The plagioclase compositions vary from Ab 45 to Ab 78 and K-feldspars are sanidine and anorthoclase in composition. The clinopyroxene is mainly magnesian augite in composition and plot near to diopside field. The amphiboles are two types of hornblendes and pargasite and the biotite is mainly magnesian in composition and plot in phlogopite field. The Oligo-Miocene extrusive rocks are mainly K-rich (high-K calc-alkaline and shoshonitic), while Pliocene extrusive rocks are Na-rich alkaline. These rocks are characterized by LREE and LILE enrichment on the chondrite- and primitive mantle-normalized spider diagrams. These features attribute to magmatic rocks that crystalize from magmas that originate from modified upper mantle in subduction-related settings. On the discrimination diagrams, the Oligo-Miocene K-rich extrusive rocks fall within continental arc field, while the Pliocene Na-rich extrusive rocks fall within post-collisional field. The geochemical data show that the Na-rich basalts and K-rich volcanic rocks in the SSZ originated from a deep-to-semi-deep metasomatized lithospheric mantle source with garnet, amphibole, phlogopite, and spinel assemblages. It seems that the residual mineralogy of the source mantle is affected by subducted sediments and crustal rocks. The degree of LREE and LILE enrichment and geochemistry of major elements are consistent with magmas that generated from partial melting of the heterogeneous and enriched mantle source which contains peridotites with abundant hydrated phases, such as sodic amphibole (for Pliocene Na-rich extrusive rocks) and phlogopite (for Oligo-Miocene K-rich extrusive rocks).