Resumen de Etapas de formación de dolomías masivas del entorno de la Florida- el soplao, Cantabria
Idoia Rosales, María Najarro de la Parra, Javier Martín Chivelet, Francisco Velasco Roldán
Dolomitization played a very important role in producing porosity within the Late Aptian shallow marine carbonates hosting the El Soplao Cave and La Forida mine deposit. A detailed petrographic study of samples from a stratigraphic section across these limestones and dolostones has revealed three diagenetic stages from shallow to late burial and finally uplift. During these stages, at least four phases of calcite cementation (C1 to C4) and five phases of dolomite formation and recrystallization (D1 to D5) took place. The timing of dolomitization is still uncertain, but the first phase (D1) occurred shortly after limestone deposition (shallow burial diagenesis) as cement filling primary and early secondary (mouldic) porosity. Calcite cements C1 and C2 occurred also in this diagenetic stage. Later, pervasive replacement dolomitization (D2, idiotopic) and dolomite recrystallization (D3, xenotopic) took place in the burial realm. Saddle dolomite (D4) occurred in continuity with xenotopic dolomite D3 as pore-lining cement in vuggy porosity. Late-stage coarse saddle dolomites (D5) were precipitated as cement in fractures, hydrofractures and hydrothermal breccias cross-cutting the previous dolomite stages. Coarse blocky calcite cement (C3) fills the remaining pore space during latest burial diagenesis. Finally, dedolomitization, iron oxides and calcite C4, are observed in discrete zones within dolomite crystals, and are related to uplift meteoric diagenesis and karst-related dissolution.
