Conventional and high-resolution heavy mineral analyses applied to flysch deposits : comparative provenance studies of the Ropianka (Upper Cretaceous–Paleocene) and Menilite (Oligocene) formations (Skole Nappe, Polish Carpathians)

摘要

Conventional and high-resolution analyses of heavy minerals from the gravity flow-deposited sandstones of the Campanian–Maastrichtian interval of the Ropianka (Upper Cretaceous–Paleocene) and Menilite (Oligocene) formations of the Polish Carpathians display similar compositions in terms of mineral species. Zircon, tourmaline, rutile, garnet, staurolite and kyanite belong to the main constituents in both formations. Apatite is common in the Ropianka Fm., while the Menilite Fm. almost lacks this mineral. Furthermore, individual hornblende grains were found in the Ropianka Fm., while andalusite is present only in the Menilite Fm. The Ropianka Fm. is relatively richer in zircon, tourmaline, garnet and apatite, while the Menilite Fm. contains more staurolite and kyanite. Zircon and tourmaline colour and morphological varieties are similar in both formations. The similarities of the heavy mineral assemblages studied suggest origin of these minerals from lithologically similar rocks. Negative correlations between the zircon + tourmaline + rutile (ZTR) values and the content of garnet and staurolite in the Ropianka Fm. may indicate, to a large extent, first-cycle delivery of garnet and staurolite to the formation. Negative, but low, correlation valid only for ZTR and garnet and positive correlations for ZTR and staurolite and kyanite in the Menilite Fm. suggest delivery of these minerals from sedimentary rocks or/and palimpsest sediments. The data obtained on mineral relationships and their morphology suggest mixed first-cycle and recycled provenance of the heavy minerals studied. Additionally, the first-cycle material input seems to be larger during the Ropianka Fm. sedimentation, while during the deposition of Menilite Fm. the contribution of material delivered from erosion of recycled sediments appears more prominent. The heavy mineral evidence suggests a change at the northern margin of the Skole Basin from an immature passive margin with a high relief during sedimentation of the Campanian–Maastrichtian part of the Ropianka Fm. to a mature passive margin with a low relief during sedimentation of the Menilite Fm.