Fluidos asociados a filones de cuarzo en la Sierra de Guadarrama. Sistema Central Español.

Resumen

Fluids together with alteration were studied in representative hydrothermal barren quartz veins from central part of Sierra de Guadarrama (Spain). Three types of fluids have been distinguished: (i) an early fluid stage characterized by primary H2O-CaCl2 two phase inclusions at room temperature (Lw1); Te: -50/-40°C; Tm: -0.4/0ºC and Th: 170/295°C. (ii) a secons stage characterized by H2O-CaCI2-NaCI (MgCI) 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/-60ºC; Tm:-24.2/-25,7ºC and Th: 60-165ºC. (iii) later fluid inputs in the veins are shown by secondary high salinity H2O-NaCI (CaCI2) 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- 260ºC 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 of P-T conditions.