Geochemistry and petrogenesis of mafic volcanic rocks from Kahak area (Urumieh-Dokhtar magmatic arc)

Abstract

The Kahak mafic volcanic rocks in the central part of the Urumieh-Dokhtar Magmatic Arc are composed of ‎basalts‏ ‏and‏ ‏basaltic ‎andesite and show sub alkaline to transitional affinity. They are calc-alkaline based on the tholeiitic index (THL). U-‎Pb zircon dating ‎yields almost 60‎‏ ‏‎(Middle Paleocene) and 24 to 19 Ma (Late Oligocene–Early Miocene) for andesitic basalt and basaltic ‎rocks ‎respectively. These rocks ‎are identified by LREE and LILE enrichment and HFSE depletion with relatively negative or without ‎Eu ‎anomalies and E-MORB like ‎pattern in multiple spider diagrams that.attributed to the subduction of the Neotethyan oceanic ‎slab ‎beneath the central Iranian microcontinent. Based on petrography, trace and rare earth elements, and isotopic features, ‎fractional ‎crystallization played a significant role ‎during magma evolution in these rocks. Trace element modeling suggests that the ‎studied mafic ‎rocks were derived by partial melting ‎within the spinel‏ ‏lherzolite mantle. Isotopic ratios also show that they resulted from ‎lithospheric ‎mantle metasomatized by ‎released fluids from subducted slab sediments. The studied samples might have formed in the ‎extensional regime ‎followed ‎by slab rollback and undergone a continental arc to back-arc basin transition during the Paleocene to ‎Miocene. This basin might ‎have ‎been closed in the‏ ‏middle Miocene.