Mineral chemistry and petrology of gabbroic bodies from ophiolitic complex of SE Soltan Abad (Sabzevar)

Gabbroic complex of Soltan Abad is Located about 35 Km east of Sabzevar. According to tectonic classification, the study area is part of Sabzevar ophiolitic zone. The composition of these intrusion bodies are vary from gabbro to gabbro-diorite. The main minerals of gabbroic rocks are plagioclase (bytonite), clino-pyroxene and ortho-pyroxene (enstatit – hyperestene) and accessory minerals are apatite, sphene, biotite, and opaque minerals (different iron oxides). Secondary minerals are sericite, chlorite, carbonate and tremolite- actinolite. According to the geochemical diagrams, these bodies are tholeiitic and metaluminous - peraluminous. Amphiboles belong to the calcic group. Geothermobarometry of pyroxene, amphibole and plagioclase indicate that the temperature of plutonic rocks formation was between 1000 and 1350 °C. On the basis of geochemical studies and tectonic setting, the gabbroic bodies of SE Soltan Abad are comparable to the volcanic arc basalts and created in the regime of volcanic arc tectonic setting. On the basis of geochemical data and field relation, magmatic source of plutonic complex should have been derived from mantle. This magma is depleted from Ti, Nb and Ba and enriched in K and Rb which indicate the charactristics of subduction setting.