Geothermobarometry and tectonic Setting of basic igneous rocks from the Horjand, NE Kerman

The Horjand area is located in northeast of Kerman in the Central Iran zone and the Kashmar-Kerman tectonic belt. In this area, gabbroic rocks and doleritic dykes are intruded into the sedimentary rocks of Desu Series with Infra-Cambrian age. The gabbros and doleritic dykes have relatively same composition. The main minerals are plagioclase and clinopyroxene. Their texture is medium to fine granular and ophitic to sub-ophitic. The plagioclase minerals of the rocks have labradorite composition (An53-67), but as a result of saussuritization in gabbros and doleritic dykes, the plagioclase changed to oligoclase and albite composition, respectively. The mineral chemistry of clinopyroxenes display Mg-Ca-Fe type which are diopside and augite. The distribution of aluminum in clinopyroxenes structure show that the minerals were crystallized from a magma with water vapor pressure less than 10 percent. On the basis of the chemical charaterstions of the clinopyroxenes, the magma source has predominantly had tholeiitic to minor alkaline affinities with a tectonic setting related to within plate environments. Geothermobarometry evaluations of the clinopyroxenes reveal that the mafic rocks were formed at temperatures of 1127-1200 ˚C and pressure less than 6 Kbar.