Skład izotopowy tlenu i siarki w siarczanach rudy siarkowej ze złóż tarnobrzeskich

Stanisław Hałas, Andrzej Kurpiewski

Abstrakt


ISOTOPIC COMPOSITION OF OXIGEN AND SULPHUR IN SULFUR ORE SULFIDES IN THE TARNOBRZEG DEPOSITS

Summary
A suite of 16 samples of native sulfur ores from north Miocene basin in Carpathian Foredeep was treated by concentrated HCl or 10% NaCl solution in order to extraction of dispersed sulfates. This procedure enables separation of SrSO4 from CaSO4, which were found in amounts ranging from 20 ppm to order of one thousand ppm by mass. Both fractions of sulfates were studied isotopically (δ18o, δ34S).
It was found that all sulfates dissolved by HCl and some of extracted by NaCl-solution are strongly enriched in heavy isotopes in comparison to evaporitic gipsum. The points representing their δ18O and δ34S values are spread along the straight line with slope of 2.85. This slope, accordingly to Mizutani and Rafter experimental data, correspond to δ18O ≈ - 7‰ for water in which reduction processes took place.
A part of sulfates evolved by NaCl solution shows quite different isotopic compositions. Their points (8180, δ34S) fall into the area of isotopic compositions of sulfates which originated by sulfur oxydation. This kind of dispersed sulfates is depleted in 34S in comparison to native sulfur. In some cases was found a large difference between their δ34S values up to 8.5 per mil. Using Lloyd's fundamental data on the behaviour of oxygen isotopes, the δ18O value for water in which the oxydation took place was estimated. The range of obtained values (-13.5 to -5.6‰) indicates for the meteoritic origin of this water.

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