Fluid flow in the Cantabrian Zone (NW-Spain) - contributions to the diagenetic evolution

摘要

The Devonian carbonate formations of the Somiedo-Correcillas Unit (NW-Spain) are the main topic of this diagenetic study. The objective is to reconstruct the different fluid flow events to investigate the basin evolution before, during and possibly after the Variscan orogeny. The starting point of our research is a cement stratigraphy to distinguish different fluid events affecting the Devonian to Lower Carboniferous sedimentary series. During the basin stage, rock buffered fluids circulated, precipitating cements characterized by decreasing δ~(18)O-values. The formation of non-ferroan calcites marks the onset of deep burial diagenesis and is followed by the precipitation of ferroan saddle dolomite. Finally, ferroan blocky calcites crystallized, showing the most negative 5~(18)O-values which indicate deepest burial conditions. Non-ferroan saddle dolomite precipitated in post-Variscan time or later. Two generations of blocky calcites formed subsequently from solutions with low fluid-rock interaction.