Petrological characteristics of gabbroic intrusions in southeastern Urmia-Dokhtar magmatic belt, Kerman province, Iran: Evidence for post-Eocene mafic magmatism

Abstract

: At the south of the Bardsir, Kerman province, Iran, the southeastern part of the Urmia-Dokhtar magmatic arc (UDMA), a large number of gabbroic intrusions are intruded into the Eocene lava flows and pyroclastic rocks with the form of small stocks and dykes. In this paper, geochemical variations, magmatic evolutions, and the origin of these intrusions are investigated. The studied intrusions are characterized by fine-grained margins resulting from rapid cooling and flow differentiation. They display porphyritic texture and include coarse-grained clinopyroxene with diopside compositions (Wo = 46.89, En = 40.78, Fs = 12.32), plagioclase with labradorite composition (An = 54.14), and olivine in an intergranular crystalline groundmass. Their whole-rock chemistry proves that the rocks belong to the calc-alkaline series. The abundances of trace elements and REE, depletion of Nb, Ta, Zr, Ti, and Hf, and enrichment of LILE relative to HFSE indicate that these rocks belong to a subduction zone setting. Geochemical characteristics (Sm/Yb and La/Sm ratios) show that the source rock of these intrusions was the lithospheric mantle with spinel lherzolite composition, which initially underwent partial melting (10% to 20%) events and then was metasomatized by fluids derived from the subducting Neo-Tethys lithosphere.