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Anhydrites from gypsum cap-rock of Zechstein salt diapirs

Jaworska J., Nowak M.

Geology, Geophysics and Environment

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2013

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Vol. 39, no. 3

233--250

EN

Petrographic studies of gypsum cap-rock formations of the Wapno, Dębina, Mogilno (Poland) and Gorleben (Germany) salt domes indicate that the occurrence of anhydrite in the domes, in the form of both single grains which sometimes create an anhydritic sandstone bed in the bottom section of the cap-rocks, and massive fragments or anhydrite rocks (detached blocks), most often represent the Main Anhydrite formations. Both types of anhydrites: - can be distinguished owing to their different structures and textures, - are subjected to the gypsification process, although anhydrite sand and sandstone are transformed quickly, while detached blocks of anhydrite very slowly. Residuum anhydrites are concentrated in the cap-rock bottom and/or dispersed in coarse-crystal gypsums, while detached blocks occur irregularly.

PL

Badania petrograficzne utworów czap gipsowych wysadów solnych Wapna, Dębiny, Mogilna i Gorleben (Niemcy) wskazują, że występujące w ich obrębie anhydryty to zarówno pojedyncze ziarna, które niekiedy tworzą w spągowej części czapy poziom piaskowca anhydrytowego, jak i masywne fragmenty, bloki skał anhydrytowych (porwaki) reprezentujące najczęściej utwory anhydrytu głównego. Oba typy anhydrytów: - można rozróżnić, mają odmienne struktury i tekstury, - ulegają procesowi gipsyfikacji, przy czym piasek i piaskowiec anhydrytowy szybko, natomiast porwaki anhydrytowe dużo wolniej. Anhydryty rezydualne są skupione w spągu czapy i/lub rozproszone w gipsach grubokrystalicznych, a porwaki występują nieregularnie.

2

Oxygen and sulphur isotopes of gypsum from the Mogilno Salt Dome cap-rock (Central Poland)

Jaworska J. K, Wilkosz P.

Geological Quarterly

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2012

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Vol. 56, No 2

249-260

EN

The stable-isotope compositions of oxygen and sulphur from 30 gypsum samples obtained from three drill cores of the Mogilno Salt Dome cap-rock have been analysed; the Mogilno Salt Dome itself is composed of Zechstein evaporites. d344 184242418344182418181818218218218218182

3

An oxygen and sulfur isotopic study of gypsumfrom the Wapno Salt Dome cap-rock (Poland)

Jaworska J.

Geological Quarterly

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2010

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Vol. 54, No 1

25-32

EN

The stable isotope compositions of oxygen and sulfur from gypsum samples derived from borehole cores of the Wapno Salt Domecap-rock have been determined. The d18O values were measured (for both the SO4 and the H2O) in bulk samples of gypsum(CaSO4 2H2O) and in its dehydrated equivalents (CaSO4). The SO4 is enriched in the heavy oxygen isotope, which unequivocally indicates the Zechstein sea as the place of origin of the sulfate. The variable δ18O values of the H2O (water of crystallization) indicate different conditions (and stages) of diagenetic processes of these samples, primarily recrystallization (hydration) episodes. Two groups ofgypsum were distinguished: (1) a group in which the δ18O values of H2O range between -9.0 and -10.2‰ (interpreted as gypsum in equilibrium with recent or subrecent meteoric water), (2) a group in which the d18O values of the H2O were less than -10.2‰ (this gypsum hasrecrystallized in the presence of water enriched in the light isotopes of oxygen). In addition, in one single analysis the δ18O value of the H>sub>2O amounts to -5.6‰ (gypsum with mixed isotopic composition).