COFFINITE FROM THE PERMIAN COPPER-BEARING ORES, SW POLAND

摘要

In the Permian copper-bearing strata of Fore-Sudetic Monocline (Poland) coffinite has been found for the first time. Previously in Poland it was identified in the hydrothermal polymetallic Kowary deposit (Ramdohr 1961; Mochnacka 1966) and in the Triassic terrigenous sediments of the Peribaltic Syneclise (Bareja 1980). In the rocks studied coffinite occurs locally in the near-top part of the Weissliegendes sandstones and was described in a variegated, grey-pink rock with black and brownish stains, representing a transitional redox environment. The coffinite is associated with diversified Ni-Co mineralization and accumulations of thucholite and pitchblende as a secondary mineral replacing the pitchblende as well as the framework components and cement of the sandstones. Its genesis should be linked with uranium-bearing hydrocarbons affecting the sandstones, particularly detrital quartz. Such chemically aggressive solutions, saturated with UO_2 ions and CO_2 from the broken down carbonate uranium-bearing complexes, corroded and metasomatically replaced the sandstone minerals. As a result, thucholite and uranium silicate -coffinite - formed, the latter due to the silica from the decomposed quartz. The coffinite is developed as spheroidal and botryoidal accumulations, the latter growing as replacement rims inwards quartz grains. The most important mineralogical features as well as the composition of coffinite have been determined.