Kharazmi Journal of Earth Sciences

Gabbroic bodies with NW-SE trend outcropped in the southwest of Sahneh in the north of Gamassiab River, W. Iran are part of Zagros ophiolite . This complex is separated from the other geological units by deep faults and cut by pyroxenitic dikes. The field evidences, petrographic, geochemical and mineral paragenesis of these rocks are completely different from the fresh and un-altered gabbroic rocks. Furthermore; the high ratios of ¹⁴³Nd/¹⁴⁴Nd (0.512945-0.513021) and low ratios of ⁸⁷Sr/⁸⁶Sr (0.70334-0.70656) indicate the sub-oceanic depleted mantle source for the origin of these rocks. Low variation of ¹⁴³Nd/¹⁴⁴Nd ratios, increasing of ⁸⁷Sr/⁸⁶Sr ratios, decreasing of SiO₂ and increasing of CaO and Al₂O₃ mainly concludes the high reaction of gabbroic rocks with seawater. The pargenetic assemblages of altered gabbros are grossular/hydrogrossular, anderadite, epidote, idocrase (vesuvianite) and diopside. The mineral paragenesis reveals that the rodingitization was occurred by reaction of gabbroic bodies with high alkali water at a shallow depth.