Mineralogy and Geochemistry of the Numidian Formation (Central-Northern Sicily): intra-formation variability and provenance evaluation

Mudrocks and sandstones of Numidian Formation in Sicily have been analysed for mineralogical, petrographic, major element and selected trace element compositions to constrain the intraformational variability and the sediment provenance. The mudrocks are characterized by a kaolinite-rich signature while the sandstones have a quartz-arenitic composition. The high Chemical Index of Alteration and Plagioclase Index of Alteration strongly suggest that recycling processes have been responsible for the present compositions. The mudrocks geochemical data suggested a compositional variability function of the paleogeographic depositional environments. In particular, the Numidian Formation of the more external Serra Del Bosco Unit is affected by the terrigenous contribution of epicontinental-type sediments. With regard to provenance, the geochemical data indicate a derivation from post-Archean sedimentary siliciclastic rocks. The contribution of African cratonic sediments was confirmed by the trace elements ratios and by the end-member modelling processed on mudrocks compositional data. In particular the suitability of the Nubian sediments as one of the sources of sediment supply is also attested.