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Abstract

Fluids related to veins and hydrothermal alterations from the Spanish Central System have been studied. Fluid chemistry has been established using microthermometry and Raman spectroscopy. Special attention has been paid to the 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 distinguished by their fluid pressure, temperature and salinity features. Under initial conditions the fluid pressure may be high, at lithostatic values, and show a nearly isobaric evolution. The later aqueous fluids drop to hydrostatic pressure with a transition to low pressures, in part due to uplift and erosion.