Sepiolite occurrence in ultramafics of the North Nain

This is the first report on sepiolite occurrences from ultramafics of Nain ophiolitic sequence. Sepiolite is a hydrous clay mineral with fibrous structure that is very important for industrial applications due to properties. Formation of sepiolite is related to several reactions in ultramafics of Nain ophiolite. This process is carried out in three main stages. At first, the hydrothermal fluids have been affected on ultramafic rocks so they altered to serpentinite. The influx of CO2-H2O bearing fluids along shear zones in serpentinized and brecciated ultrabasics caused dissolution and carbonatization of serpentinites. During the carbonation of serpentinite, reaction between ultrabasics with hydrothermal fluids have led to formation of Mg and/or SiO2 bearing solutions at low temperatures, and finally, sepiolite resulted from interaction of CO2, H2O rich hydrothermal fluids.