Dedolomitization-driven karstification and speleogenesis in central Slovenia: Mineralogical and geochemical insights

This study examines the petrography and geochemistry of dolomite wall rock and associated dedolomite in the Mravljetovo brezno v Gošarjevih rupah cave system of central Slovenia and evaluates the influence of dedolomitization on speleogenesis and karstification. Three distinct dedolomitization-related facies were identified: (i) Type 1, featuring dolomite replaced and cemented by calcite; (ii) Type 2, characterized by bladed and cone-shaped calcite associated with clay minerals and iron oxides; and (iii) Type 3, a detrital, stratified deposit resulting from host rock weathering and allogenic sedimentation and diagenesis in phreatic conditions. Geochemical analyses reveal a progressive loss of Mg and Sr, enrichment in Ca, starting from the unaltered dolomite of the wall rocks up to all facies associated with dedolomitization. In addition, enrichment of Si, Al, Fe and other silicate-associated elements were observed in all dedolomite types. Stable isotope (δ 13 C, δ 18 O) data suggest organic carbon input and meteoric diagenesis as primary controlling factors. ΣREE+Y patterns, negative Ce anomalies (Ce/Ce* < 1) and the enrichment in some trace elements (e.g. Zr, Zn, Cu, Pb, Ba) indicate an oxidative environment with a strong detrital influence. Structural discontinuities played a crucial role in directing fluids and detrital material along fault zones and bedding planes which facilitated dedolomitization and subsequently cave formation. The findings show that dedolomitization not only altered the original dolostone fabric but also facilitated speleogenesis by enhancing rock heterogeneity and increasing its susceptibility to dissolution, while at the same time playing an important role in karstification and the further development of dolostone landscape. • Dedolomitization enhanced dolostone porosity, promoting speleogenesis • Multi-proxy analysis reveals three dedolomitization-related facies • Three dedolomite facies reflect progressive diagenetic and detrital stages • REE + Y, trace elements, and Ce anomalies indicate oxic diagenetic fluids • δ 13 C–δ 18 O isotopes confirm meteoric water and organic carbon influence