Fluid evolution and hydrothermal processes of the Spanish Central System

Fluids related to veins and hydrothermal alterations from the Spanish Centr al System have been studied. Fluid chemistry has been established using mic rothermometry and Raman spectroscopy. Special attention has been paid to th e evolution of P-T conditions from early H2O-NaCl-CO2-CH4 to later H2O-NaCl -CaCl2 fluids. The different types of fluid systems investigated can be dis tinguished by their fluid pressure, temperature and salinity features. Unde r initial conditions the fluid pressure may be high, at lithostatic values, and show a nearly isobaric evolution. The later aqueous fluids drop to hyd rostatic pressure with a transition to low pressures, in part due to uplift and erosion. (C) 2000 Elsevier Science B.V. All rights reserved.