Detrital garnets from the Upper Cretaceous-Palaeocene sandstones of the Polish part of the Magura Nappe and the Pieniny Klippen Belt : chemical constraints

Heavy mineral assemblages of the Upper Cretaceous-Palaeocene sandstones of the Polish part of the Magura Nappe and the Pieniny Klippen Belt (PKB) were studied. They consist mainly of stable minerals, such as zircon, tourmaline and rutile, but in many assemblages significant amounts of garnets are also present. To describe the provenance of the main heavy mineral groups their chemical composition was analysed. This article deals with the garnets group. Heavy minerals, including garnets, were derived to the Magura Basin from two opposite source areas: the north-west (northern) and the south-east. In the chemical composition of the analysed garnets, FeO and the almandine molecule are definitely dominant, but garnets with a raised MgO and pyrope molecule content were also found. Proportions among the main elements occurring in garnets indicate that they were formed under low- to medium grade metamorphic conditions in the southeastern source area, and medium- to high-grade conditions in the northern one.