Bromide distribution characteristics of different Zechstein 2 rock salt sequences of the Southern Permian Basin: a comparison between bedded and domal salts

Abstract

The bromide profile of the bedded Zechstein 2 rock salts in the Southern Permian Basin is characterized by a continuous increase in the bromide contents from base to top, indicating progressive evaporation of sea water. Former studies have suggested that the bromide distribution in domal salts is more irregular, raising such questions as whether there is a causal relationship between bromide distribution and deformation‐related processes or whether various halite types with different primary bromide contents account for such irregularities. In this study, the bromide distribution of a defined stratigraphic section (Hauptsalz) of the Zechstein 2 was investigated in three salt deposits, with bedded salt (Teutschenthal) compared with domal salts (Morsleben and Gorleben). Furthermore, two different halite types (Kristallbrocken, matrix) were distinguished during sampling. Comparison between the locations reveals that: (i) the characteristic trend of the bromide profile was generally preserved in both the bedded and the more intensely deformed domal salts; (ii) the dispersion of bromide contents along the running average curve is lower in domal salt, especially in the lower half of the Hauptsalz; and (iii) the Kristallbrocken are absent in the lower half of the Hauptsalz of Morsleben and Gorleben. The absence of the Kristallbrocken and the lower dispersion of the bromide contents in the domal salts are clear indications for the influence of salt migration‐related processes on the bromide distribution characteristics. It shows that these processes are associated with a redistribution of bromide, which eventually results in a homogenization of the originally varying bromide contents. On the other hand, preservation of the characteristic trend in the bromide profiles indicates that large‐scale brecciation, folding processes or circulating bromide‐rich fluids played only a minor role during the formation of the salt domes. Selective sampling of the Kristallbrocken and matrix halite displays a disparity in bromide content that is not consistent between the studied locations. These specific phenomena might be related to different depositional locations in the Zechstein Basin or to post‐depositional processes.

Structural evolution of continental and marine Permian rock salt of the North German Basin: constraints from microfabrics, geochemistry and U–Pb ages

“…Zechstein halite formed as part of the marine Permian Zechstein group as is indicated by higher bromide concentrations in halite and minor concentrations of anhydrite and polyhalite. The interval of bromide concentration and the observed main mineral phases fit well with previous investigations of diapiric Staßfurt Main Salt (z2HS) from the North German Basin (Bornemann et al 2008;Küster et al 2009). The dominance of polyhalite over anhydrite in some samples is related to higher bromide concentrations.…”

“…Zechstein strata preserve clear to cloudy halite crystals of a white to grey color. The lithology represents the upper two stratigraphic units of the Staßfurt Main Salt (z2HS), the "Streifensalz" (z2HS2) and "Kristallbrockensalz" (z2HS3), which are common in salt structures of the central NGB (Bornemann et al 2008;Küster et al 2009). Rock salt includes halite with impurities of anhydrite and minor content of polyhalite and microcrystalline carbonate.…”

“…1 Geological maps and cross sections of the study area. a Zechstein salt distribution in the North and South Permian Basin after Best (1989) and Küster et al (2009). b Lithostratigraphic section showing investigated rock salt units (after SKPT (2011); Baldschuhn et al (2001); Bornemann et al (2008)).…”

The Formation and Structure Evolution of Zechstein (Upper Permian) Salt in Northeast German Basin: A Review

“…Except the sedimentology and stratigraphy approaches, the geochemistry (including major/trace elements, isotope elements (Sr, S, O, H, C), fluid/solid inclusion analysis) and geophysics (including seismic interpretation, 3D structure modeling, backstripping modeling and restoration section modeling) have been well developed. More recently, bromide (Br) content in salts has been used to identify the processes or result of salt movement [108,109]. Besides, X-ray texture goniometer has been used to analyze the microstructure of salt, which gives us a new view for the salt movement.…”

Bromide characteristics and deformation mechanisms of naturally deformed rock salt of the German Zechstein Basin

“…In a previous study, the bromide distribution of the Hauptsalz was investigated in three salt deposits (Küster et al 2009). In both the bedded (Teutschenthal) and the more intensely deformed domal salts (Morsleben, Gorleben), the characteristic trend of the bromide profile was generally preserved.…”