DETRITUS FROM VARISCAN LOWER CRUST IN ROTLIEGEND SANDSTONES OF THE INTRA-SUDETIC BASIN, SW POLAND, REVEALED BY DETRITAL HIGH-PYROPE GARNET

摘要

It is well established that pebbles in the Sudetic Permian conglomerates were derived from the nearby Variscan massifs of upper-crustal composition. However, the provenance of the sand-size grains remains enigmatic. Electron microprobe analyses (EMPAs) of detrital garnet from upper Rotliegend conglomerates and sandstones exposed at Golińsk, the Intra-Sudetic Basin, showed a distinct assemblage dominated by high-pyrope (high-grossular) almandine, typical of high-grade metamorphic rocks, such as high-pressure granulites. These results, coupled with a previously reported population of similar detrital garnet in the stratigraphically equivalent conglomerates and sandstones of the Karkonosze Piedmont Basin, suggest regional input of detrital lower-crustal material. This detritus was derived ultimately either from the Moldanubian Zone of the Bohemian Massif, or from high-grade rocks of the Orlica-?nie?nik Massif that were exposed in the Carboniferous–Permian. Permian siliciclastic rocks might have covered a large part of the Sudetes. During the Mesozoic and Palaeogene, these rocks might have been recycled further, contributing high-pyrope garnet, as an accessory mineral, into siliciclastic rocks of the Sudetes and their foreland.