Silicide spherules from Permian sediments of the Fore-Sudetic Monocline (SW Poland)

The presence of Fe-silicides, extremely rare mineral phases were documented in the Permian Cu-bearing ore formation in the Fore-Sudetic Monocline (Polkowice-Sieroszowice and Rudna mines, SW Poland). It is a first report of their occurrence within rocks of Late Palaeozoic age. The Fe-Si alloys forme spherules of various structure and chemical composition. The silicide spherules were found in the flotation concentrates prepared from the copper ore. Their composition varies from FeSi (fersilicite) to Fe2Si3 or Fe4Si9. A dominant constituent is Fe5Si3 (xifengite) with admixtures of P, Ti, Cr and Mn. Native Si and Ti were detected in the marginal part of spherules. The current knowledge do not permit to determine unequivocally whether the Fe-silicide spherules formed as a result of Permian cosmic dust or constitute terrestrial magmatic material of ultramafic character transported into a sedimentary basin from the adjacent terrain.