Hydrogeochemistry and diagenesis of Miocene sandstones at Montjuic, Barcelona (Spain)

Massive silicification of Miocene sandstones cropping out at the Montjuic m ountain in Barcelona has been analyzed in order to constrain paleoflow syst ems, which may have contributed to the diagenetic reactions. The section co nsists of five units with alternating sandstone-mart units. The principal d iagenetic features are observed in strongly silicified sandstone units. Alu nite mineral precipitation indicates presence of saline fluids and low pH. Salinity is most probably derived from marine seawater and low pH may be du e to oxidation of pyrite. A quantitative thermodynamic modeling is applied to characterize the percolating fluids and to constrain the hydrodynamic sy stem. (C) 2000 Elsevier Science B.V. All rights reserved.