Petrology of mafic intrusions in the south of Bardaskan (NW Lut)

The study area is located in the south of Bardaskan (south west of Khorasan Razavi). Mafic intrusions of Robat-e-Zangiche and Lakh Bargheshi areas from Kooh-e-Sarhangi zone have been injected into granitic basement rocks and Soltanieh dolomite. Plagioclase, amphibole and clinopyroxene are rock forming minerals. According to the petrographic evidences, mineral chemistry and thermobarometry data amphiboles have different generations of igneous and alteration types. The results of amphibole thermobarometry indicate temperature and pressure ranges of 545-911 °C and 2.2 to 5.8 kb respectively. Such wide range of calculated temperature and pressure could be interpreted by various solidification conditions and also secondary altration processes. On the basis of whole rock chemistry, the studied samples are mainly gabbro. The spider diagrams display geochemical signatures of subduction zones magma. Based on tectonic discrimination diagrams, genesis of the studied rocks is related to the both subduction and within plate settings. Furthermore, whole rock chemistry of the studied samples is compatible with spinel lherzolite melting. As the formation of Sabzevar back arc basin was probably triggered by the Neotethys subduction beneath Central Iranian microcontinent, so the Jurassic back-arc magmatism of the Bardakcan area may be affected by the same subduction process and concomitant asthenospheric upwelling in an extensional regime.