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| Titel |
Stable isotope composition of fluid inclusions preserved in halite derived from Wieliczka and Bochnia Salt Beds (Southern Poland) |
| VerfasserIn |
Marek Dulinski, Kazimierz Różański, Krzysztof Bukowski |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034743
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| Zusammenfassung |
| Halite deposits located in the southern Poland, near Krakow, are famous mostly due to the
medieval salt mine located in Wieliczka. Contrary to most salt deposits in Europe forming
large domes, the halite deposits near Krakow form distinct beds, extending from west to east
on the area of ca. 10 km2, with several types of salt identified. The deposits were formed in
shallow environment, ca. 15 mln years ago and represent initial stages of Miocene sea water
evaporation.
Stable isotope composition of fluid inclusions trapped in the halite crystals originating
from Wieliczka and Bochnia salt mines was investigated. Three distinct groups of samples
were analysed: (i) samples derived from so-called “green salt” beds forming extensive
horizontal structures, (ii) samples derived from so-called zuber-type salt, and (iii) large
monocrystals of halite collected in two crystal caves existing in the mine. The samples
belonging to the first and second group were heated under vacuum to extract the fluid
inclusions, according to the procedure used previously to extract inclusions from speleothem
samples. The macro-inclusions present in some monocrystals of halite collected in crystal
caves were removed for analysis without any thermal treatment. The concentration of
bivalent cations (Ca2+, Mg2+) was measured in the bulk material (green salt).
K+, Mg2+ and SO4-2 content was measured in the fluid inclusions derived from
macro-crystals.
The stable isotope data points form two clusters in the δ2H-δ18O space, representing
crystal caves and green- and zuber-type salts, respectively. The cluster representing green-
and zuber-type salt deposit is shifted to the right–hand side of the Local Meteoric Water Line
(LMWL), towards more positive δ2H and δ18O values, pointing to evaporative conditions
during formation of these deposits. Although the evaporation trajectories for the sea water in
the δ2H - δ18O space suggest that fluid inclusions might represent remnants of the original
solution, this notion has to be excluded due to the fact that only halite is present in the
deposits. Other salts are present locally only in trace amounts. The isotopic composition of
fluid inclusions formed during precipitation of halite phase from pure sea water would be
characterised by positive δ2H and δ18O values. The results of isotope analyses
suggest that the green- and zuber-type salt deposits might have been formed in
a lagoon-type environment, from mixture of sea water and water of continental
origin.
The data points representing monocrystals of halite collected in the crystal caves lie close
to the LMWL and cover the range of δ2H and δ18O values typical for glacial/interglacial
infiltration waters. This provide the proof that large monocrystals of halite in the crystal caves
are of secondary origin and were formed with participation of infiltration water, most
probably during the Quaternary. |
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