Abstract: The easthern Guilan province ophiolite complex is a dismembered ophiolite complex that is located in northern Iran and belongs to the Alborz orogenic system. It consist of layered ultramafic cumulates, layered gabbro, isotropic gabbro, diabase and a volcanic sequence that exhibits a wide range in composition from subalkaline basalts to alkaline basalts. The associated limestones including of Globotruncana fossils show an upper Cretaceous age for that. The geochemical data clearly identifies some of the volcanic rocks to have formed from two distinct types of basaltic melts: (i) those of the subalkaline suite which formed from an initial melt that are characterized by selective enrichments in fluid-soluble Large Ion Lithophile Elements (LILE) and LREE relative to the High Field Strength Elements (HFSE) and incompatible trace element patterns that suggest an island arc affinity and (ii) those of the alkaline suite with significant enrichment in LILE, HFSE and LMREE and a slight depletion in HREE and incompatible trace element patterns that are virtually identical to typical Oceanic Island Basalt (OIB) pattern. It is suggested that more than one-stage melting process is required to explain geochemical characteristics of back-arc basin and OIB basalts of this area. The overall chemical characteristics indicate that the studied volcanic rocks represent a volcanic units that were formed in an arc-basin system that is characterized by an oceanic lithosphere generation most probably associated with melting of mantle material along a supra-subduction-type spreading centre and alkali rocks were generated from a plume in a local extension regime in an island arc environments in an oceanic basin.