Petrography, Geochemistry, Tectonic-Magmatic Setting, and Petrogenesis of Gabbroic Rocks in the Robat-Shahr Babak Area, Kerman, Iran

Abstract: The study area is located in the southeastern part of the Sanandaj-Sirjan Zone (SSZ). The rock unit outcrops include olivine gabbro, troctolite, dunite, and granodiorite. In this area, the gabbro bodies are arranged separately but close to each other in two rows along the northern margin of the Shahr Babak granodiorite batholith, which dates back to the Jurassic. This granodiorite body consists of multiple phases, with the oldest phase being Jurassic in age. The final magmatic phase is represented by a granodiorite body of Eocene age, which outcrops among the gabbros. On a microscopic scale, the plagioclase and pyroxenes in the samples from this region exhibit sieve texture and zoning, indicating disequilibrium conditions during magma solidification. These textures are attributed to the presence of hydrous minerals and changes in water fugacity. The chemical composition of the samples collected from the study area exhibits a sub-alkaline (tholeiitic to calc-alkaline) signature, ranging from gabbro to peridotite-gabbro. These rocks are related to subduction and occur in a continental arc. Additionally, they have been contaminated by material from the upper continental crust. The parent magma of the samples in this area originated from an enriched spinel-lherzolite mantle.