Petrology and Geochemistry of Cretaceous Sedimentary Rocks of the Monte Soro Unit (Sicily, Italy): Constraints on Weathering, Diagenesis, and Provenance

The mineralogy and chemical compositions of shale and sandstone alternations of Cretaceous age of the Monte SoroUnit, Sicily, have been determined. The clay minerals in the shales are mostly illite and I-rich mixed-layer I/S reflectedby enrichment in Al2O3, K2O, and chemically similar elements. The sandstones are subarkose to quartz arenite. Theshales and sandstones have upper-crustal rare earth element patterns, and except for K2O, they are depleted in alkalineand alkaline-earth elements as a result of intense weathering. The sandstone and shale mineralogy suggests a diagenetichistory in which the sediments were subjected to temperatures in excess of 100C, during which interaction betweensome minerals in the shales and sandstones took place. Thus, diagenetic quartz cementation and feldspar alterationin the sandstones and smectite illitization in the shales occurred together with the shales being a sink for potassiumand the sandstones a sink for silicon. Negative europium anomalies ( between 0.45 and 0.87), (Gd/Yb)ch ratios ∗ Eu/Eu(!2, except for sample C1), and Sc/Cr versus La/Y and La-Th Sc diagrams suggest that the sedimentary rocks werederived from post-Archean granitoid-like rocks in a tectonically stable area. In addition, the foliated fabrics of polycrystallinequartz grains and the abundant phyllite rock fragments indicate a provenance from metamorphic rocks.The study of several trace element ratios (Ti/Zr, Cr/Zr, Y/Ni, Cr/V, Zr/Th, La/Th, La/Th, Cr/Th, Zr/Hf, Zr/Yb, Yb/Hf, V/La, La/Yb) strongly supports a local derivation from the European paleomargin.