Stable isotope geochemistry of travertines from northern Urumieh-Dokhtar volcano-plutonic belt, Iran

Abstract

In Iran, almost all major travertine deposits with NW–SE trend are exposed in Urumieh-Dokhtar volcano-plutonic belt. In this study, morphology of travertine, source of CO2, and classification of travertine were investigated using geochemistry of carbon dioxide, stable carbon and oxygen isotopic analysis, SEM images and thin sections. Morphology of travertine in the study area includes mound and cascade. Stable carbon and oxygen isotope values of the north Urumieh-Dokhtar volcano-plutonic belt travertines range between 1.46 and 11.71‰ (VPDB) and − 6.08 and − 10.21‰ (VPDB), respectively. The high δ13C values suggest a contribution of CO2 liberated by thermometamorphic decarbonation besides its magmatic origin. Consequently, these travertines are classified as belonging to the thermogene category. A probable reason for the observed high carbon isotope composition in these deposits may be CO2 consumption as suggested by the presence of bacteria and diatom activities, verified by SEM images. Pisoid, crystalline crust and pebbly lithofacies were observed. The stable isotope compositions were compared to travertines around the world. Similarities in lithofacies and morphology exist between northern Urumieh-Dokhtar volcano-plutonic belt and travertines of Turkey and Spain. The Iranian travertines are located in areas with volcanic activity. Obviously, the geothermal system remained active throughout the late Quaternary to present.