Strontium isotope composition of Badenian (Middle Miocene) Ca-sulphate deposits in West Ukraine: a preliminary study

Authors

  • Tadeusz M. Peryt Polish Geological Institute - National Research Institute, Rakowiecka 4, PL-00-975 Warszaw
  • Sofiya Hryniv Instytute of Geology and Geochemistry of Combustible Minerals, National Academy of Sciences of Ukraine, Naukova 3A, 79060 Ukraine
  • Robert Anczkiewicz Institute of Geological Sciences, Polish Academy of Sciences, Senacka 1, PL-31-002 Kraków, Poland

Keywords:

Middle Miocene, evaporites, strontium isotopes, gypsum, Paratethys

Abstract

Strontium isotope compositions have been measured in six primary gypsum samples from the most marginal part of the Badenian evaporite succession in the Ukrainian Carpathian Foredeep Basin (Mamalyha quarry section) and in two anhydrite samples from the basin-centre halite zone of the Ukrainian Carpathian Foredeep, aimed determining the origin of brines from which these sulphates were precipitated. The strontium isotope ratios (87 Sr/86 Sr) of halite facies-associated anhydrite samples are very similar (0.708902 and 0.708917, respectively) and higher than the ratio infferred for Badenian seawater. The strontium isotope ratios (87 Sr/86 Sr) of six samples of primary gypsum from Mamalyha range from 0.709154 to 0.709838; thus they are strongly divergent from coeval oceanic values. The gypsum from the lower part of the Mamalyha section shows much higher 87 Sr/86 Sr ratios than the gypsum from the upper part and a clear decreasing-upwards trend is observed. The higher strontium isotope ratios are related to the portion of the gypsum section showing both d18 O and d34 S divergent from coeval oceanic values. The 87 Sr/86 Sr ratios of minerals in marine, bedded evaporite deposits are commonly higher than that of contemporaneous seawater which is often explained in terms of secondary origin or recrystallization of these minerals in the presence of radiogenic 87 Sr-bearing fluids, mostly from a detrital source, but the Mamalyha primary gypsum is very pure and clay intercalations are very thin and rare. High radiogenic 87 Sr/86 Sr ratios in primary gypsum of the Mamalyha quarry indicate an important radiogenic strontium non-marine contribution to the Badenian basin.

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Published

2011-02-16

Issue

Vol. 54 No. 4 (2010)

Section

Articles

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