Brom w skałach ilasto-solnych cechsztynu Polski
Abstract
Bromine in Zechstein mixed clay-salt rocks of Poland.
S u m m a r y. Bromine content was determined in 50 samples taken from the Zechstein (Upper Permian) mixed clay-salt rocks both in a sample bulk and in pure halite crystals, manualy separated. This study attempted to define bromine contents directly related to pure halite and connected with clay minerals in analysed samples. The examined samples were collected in galleries of theK³odawa salt mine from the Brownish Zuber Unit (Na3t), representing PZ3 cycle and from the Red Zuber Unit (Na4t) of PZ4 cycle. Mineral composition of clay fraction in the Zechstein mixed clay-salt rocks, represented both by zubers sensu stricto (clay content 15–85%) and clayey halite (clay <15%), is monotonous and rather constant. Bromine concentration depends on salinity of mother solutions as well as on content of minerals incorporating bromine (halite, clay minerals). In samples of the Red Zuber Unit the bromine contents attributed to clay minerals were so low that they do not influence the bromine concentrations determined in total samples and they could be neglected in genetic considerations. Deposits of the Brownish Zuber Unit were precipitated from brines much more concentrated than the mother solutions of the Red Zuber rocks. Increasing content of water-insoluble residue (mainly clay minerals) in samples of the Brownish Zuber unit is accompanied with higher bromine concentrations. Difference between bromine content in total samples and in pure halite crystals also increases. So the reliable interpretation of genesis and depositional environment of halites, being a constituent of the Brownish Zuber rocks, requires detecting bromine in separated pure halite crystals
S u m m a r y. Bromine content was determined in 50 samples taken from the Zechstein (Upper Permian) mixed clay-salt rocks both in a sample bulk and in pure halite crystals, manualy separated. This study attempted to define bromine contents directly related to pure halite and connected with clay minerals in analysed samples. The examined samples were collected in galleries of theK³odawa salt mine from the Brownish Zuber Unit (Na3t), representing PZ3 cycle and from the Red Zuber Unit (Na4t) of PZ4 cycle. Mineral composition of clay fraction in the Zechstein mixed clay-salt rocks, represented both by zubers sensu stricto (clay content 15–85%) and clayey halite (clay <15%), is monotonous and rather constant. Bromine concentration depends on salinity of mother solutions as well as on content of minerals incorporating bromine (halite, clay minerals). In samples of the Red Zuber Unit the bromine contents attributed to clay minerals were so low that they do not influence the bromine concentrations determined in total samples and they could be neglected in genetic considerations. Deposits of the Brownish Zuber Unit were precipitated from brines much more concentrated than the mother solutions of the Red Zuber rocks. Increasing content of water-insoluble residue (mainly clay minerals) in samples of the Brownish Zuber unit is accompanied with higher bromine concentrations. Difference between bromine content in total samples and in pure halite crystals also increases. So the reliable interpretation of genesis and depositional environment of halites, being a constituent of the Brownish Zuber rocks, requires detecting bromine in separated pure halite crystals