The Nayband strike-slip fault forms the western margin of the micro-continental Lut block in Eastern Iran. Neogene and Quaternary mafic volcanic rocks collected near Tabas, along the northern part of the fault (NNF), and further to the south, along the middle part of the fault (MNF), are within-plate sodic-series alkali olivine basalts with high TiO2 and up to >16% normative nepheline. Their high MgO, Ni and Cr contents indicate that they crystallized from relatively primitive magmas, and La/Nb (0.5-0.65) and Nb/U (44-120) ratios, suggest that crustal contamination was not significant for these basalts. Their low La/Nb and Ba/Nb ratios are similar to oceanic island basalts (OIB) and unlike convergent plate boundary arc basalts (IAB). Normalized trace element patterns for these samples show enrichment in LREE relative to HREE. These alkali olivine basalts show limited variation in Sr, Nd and Pb isotopic values which all plot in the range of OIB, and overlap the EM-2 field. The data may be interpreted as indicating the participation of upwelling mantle asthenosphere and the deeper continental mantle lithosphere in the generation of these basalts, which formed by generally low, but variable degrees of partial melting. The small volume of melts that formed these basalts rose to the surface along the very deep Nayband strike-slip fault without significant interaction with the continental crust.

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