The dolomitization affecting the basal facies of the «Landete Dolostone» Formation in Sierra de Espadán (Castellón Province, Iberian Ranges) has been studied using fluid inclusions, stable (C and O) and radiogenic (Sr) isotopes. Two different processes have been found: (1) a pervasive epigenetic dolomitization originated by mixing of two different fluids of contrasted composition, and (2) the generation of «zebra»-llke rhythmic textures formed from hot (215 °C), high salinity (20-24 wt% eq NaCI) connate fluids equilibrated with the enclosing dolostone ( 8 18O H2O= + 13.0%o). A link between this high temperature event and the presence of a Hg deposit in the area is proposed