Organic and mineral diagenesis in oil source rocks: the Tertiary of Ribesalbes basin

Lacustrine carbonate sediments from the Tertiary Basin of Ribesalbes (Castellón, Spain) were studied with the aim of determining the relationships between organic and mineral diagenesis. Petrological and geochemical data indicated that organic matter was inmature type I. Both mineralogy and textural relations suggest that Mg-rich blue-green algae contributed to the high Mg/Ca rate found in the Ca-MgFe carbonates through diagenetic process.ln the first stage of the diagenesis, in the lacustrine anoxic environment, the bacterial processes was dominant producing the precipitation of the Ca-Mg carbonates and aragonite.Because sulfate reduction was not significant, the Mg-calcite or dolomite and the aragonite were replaced by ankerite when fermentation started, with an important methane production of bacterial origin.The most remarkable characteristics of the porosity data and the poresize distribution curves are the moderate range of porosity values (10-26%) and the porosity parameters -sorting and skewness-, which are more affected by the early organic diagenetic processes than by mechanical compaction