Uwagi o minerałach ciężkich utworów górne i kredy i triasu w niecce północnosudeckiei

Abstract

COMMENT ON HEAVY MINERALS OF UPOOR CRETACEOUS AND TRIASSIC SEDIMENTS FOUND IN THE NORTH-SUDETIC TROUGHThe author presents preliminary data on heavy minerals in the Triassic and Upper Cretaceous sedimentsurring in the region of Lwówek, situated in the southeastern part of the North-Sudetic trough.The heavy minerals were identified in the Bunter sandstone (horizons of Lwówek and of Radłówka), the Cenomanian and Turonian (zones Actinocamax plenus, Inoceramus labiatus and Inoceramus lamarcki). The author collected samples along profile lines at "Radłówka", "Mojesz-Plakowice" and "Lwówek", some 2 to 4 km. apart from each other. She made analyses using samples of the heavy minerals of 0.25 to 0.13 mm. grain size.The author identified the following heavy minerals: andalusite, apatite, biotite, brookite, kyanite, zircon, epidote, glauconite, garnet, corundum, rutile, staurolite, sillimanite, tourmaline, as well as magnetite, ilmenite and hematite.In Table 2 and Fig. 1 she presents, both numerically and graphically, the composition of the heavy minerals found in the samples taken fl,"omthe, individual stratigraphical horizons.In the sandstones of the Radłówka and the Lwówek horizons mainly tourmaline, zircon and rutile appear, with insignificant quantities of staurolite, epidote, kyanite, brookite, corundum and biotite. The tourmaline, zircon and rutile grains are markedly rounded. In the Cenomanian sandstones - alongside of tourmaline, zircon and rutile-kyanite and stauroIite appear amply; occasionally sillimanite is also found and, in trace quantities, epidote, brookite, corundum and garnet. Usually, the heavy minerals in these sandstones show habits of their primary forms. In the sandstones of zone Actinocamax plenus, the quantity of garnet is increased with a simultaneous decrease in percentage of kyanite and stauroIite to less than 1%. In the deposits of zones lnoceramus labiatus and lnoceramus lamarcki, alongside of tourmaline, rutile and zircon, garnet is found in quantities approaching the per cent content of kyanite and staurolite.The Lwówek sandstone can be distinguished from Cenomanian sandstones by differences observed in the composition and the·state of preservation of the heavy minerals; these differences also show that the clastic material of the Cenomanian was derived but sparingly from erosian of the Bunter sandstone deposits.The occurrence of garnet in the glauconitic sands tones overlying the Cenomanian sandstones seems fully to justify assigning these sands tones to zone Actinocamax plenus.