A petrochronological study of Fe Ti oxides in rodingites of the Western Carpathians, Slovakia

Rodingitization is the metasomatic transformation of mafic lithologies into rodingite, a Ca-rich and Si-poor rock associated with serpentinized ultramafic bodies. Serpentinization and rodingitization occur simultaneously but it remains challenging to obtain absolute ages on these events in order to identify the geodynamic setting of their formation. In this study, we investigate rodingites from an occurrence in the Western Carpathians with the aim to define the timing of rodingite formation during the tectono-metamorphic evolution of the Carpathian Orogen. The rodingites consist mainly of vesuvianite, diopside, garnet and chlorite. They are noticeably characterized by the presence of Fe Ti rich aggregates composed of ilmenite, rutile, titanite and calcite. Textural relationships and chemical compositions of the investigated Fe Ti minerals document their hydrothermal-metamorphic origin. These minerals are characterized by considerable rare earth element (REE) concentrations with prevailing positive Eu anomaly, which presumably derives from the plagioclase-rich protolith of the investigated rodingites. Moreover, the similarity of REE patterns between the analysed phases suggests that the REE concentrations in Fe Ti minerals are controlled by the immobility and availability of these elements in the system. A particular lamellae texture composed of rutile and calcite originated from titanite destabilization. The titanite destabilization was triggered by cooling, silica leaching and influx of CO 2 -rich fluids. In situ U Pb dating of rutile, which have formed by retrograde breakdown of titanite during rodingitization, yields a crystallization age of 102.6 ± 19.9 Ma. This age is in good agreement with Cretaceous ages of the regional alpine metamorphic evolution reported in the literature and suggests that the rodingitization and serpentinization processes took place during the exhumation and cooling of the accretionary wedge resulting from the closure of the Meliata Ocean.