Fluids ¡n barren quartz veins from Sierra de Guadarrama. Spariish Central System

Fluids together with alteration were studied in representative hydrothermal barren quartz veins from central part o f Sierra de Guadarrama (Spain). Three types o f fluids have been distinguished: (i) an early fluid stage characterized by primary H20 - C a C I2 two phase inclusions at room temperature ( L w l ) ; Te: -50/-40°C; Tm: -0.4/0°C and Th: 170/295°C. (ii) a secons stage characterized by H2Q-CaCI2-NaCI (MgCIJ inclusions two phase inclusions at room temperature (Lw2), they are primary in the borders of quartz crystals and secondary in the center; Te: is in the range of -65/-60°C; Tm:-24.2/-25,7°C and Th: 60-165°C. (Hi) later fluid inputs in the veins are shown by secondary high salinity H20-NaCI (CaCIJ inclusions (Lw-s); they are three phase inclusions including one or more solid phase (dominant halite and/or sylvine) with glogal homogenization ranges from 120- 260°C and salinity of 29-35 wt.%eq. NaCI. Barren quartz veins represents one of the latest event in the hydrothermal evolution of the Sierra de Guadarrama. Evolution of Ca contents is discussed in this paper. Quartz deposition is controlled by the decrease o f fl-T condition