Petrography and Geochemistry of Quaternary travertines in some sections from N and W Iran

Despite the majority of Quaternary deposits consist of alluvial sediments، an important proportion of deposits (in active tectonic zones) are formed as tufa and travertine. The studied travertine in this research (from seven measured sections) are located in three neighboring provinces (Qazvin، Hamedan and Kurdistan)، situated in the Central Iran and Sanandaj-Sirjan structural zones. Petrographic studies show distinct lamination، microscopic and macroscopic porosity (5-10%) in the samples. Most studied samples are biosparite; plant and algae debris present in some sections. SEM analysis shows mosaic and equant calcite crystals، grows in pore spaces. XRD analysis indicates low-magnesium calcite is present in all studied sections; some clay minerals and quartz are present in few sections. Geochemical analysis (XRF method) indicates that the average CaO and SiO2 in samples are 52. 98% and 1. 98% respectively; Si mainly occurs as quartz veins and sandstone clasts. MgO (0. 062%)، Al2O3 (0. 47%، as clay minerals) and Fe2O3 (0. 41%، as iron oxide) are also exists. Based on the cement type، meteoric and vadose diagenetic environments were recognized.