The rodingitization of gabbroic bodies in the southeast of Sahneh (west of Iran) with emphasis on mineral reaction and isotope geochemistry

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.