Investigation of the fate of nitrogen in Palaeozoic shales of the Central European Basin |
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| Authors: | Bernhard M Krooss Anke Jurisch Birgit Plessen |
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| Institution: | aRWTH Aachen University, Institute of Geology and Geochemistry of Petroleum and Coal, Lochnerstrasse 4-20, Haus B, D-52056 Aachen, Germany;bGeoForschungsZentrum Potsdam, Section 3.3, Telegrafenberg B221, D-14473 Potsdam, Germany |
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| Abstract: | Nitrogen geochemistry of Upper Carboniferous shales from the Central European Basin (CEB) was investigated by elemental analysis, stable isotope mass spectrometry and non-isothermal pyrolysis. Total N-contents of Namurian shales from four deep wells (4400–7000 m) in NE Germany ranged between 520 and 2680 ppm. Up to 90% of this nitrogen occurs as ammonium in minerals with δ15N values between + 1‰ and + 3.5‰. Low nitrogen contents (down to 460 ppm) and high δ15N values (up to + 5.6‰) in one well in the basin centre suggest a large-scale release of nitrogen associated with isotopic fractionation. Pyrolytic liberation of N2 from pelagic Namurian A shales of NW and NE Germany occurred at significantly lower temperatures than from paralic Namurian B shales and terrestrial Westphalian samples. On-line isotope analysis of N2 liberated between 400 and 1200 °C indicates the presence of precursor pools with different thermal stability and nitrogen isotopic composition. |
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| Keywords: | Nitrogen Palaeozoic shales Pyrolysis Isotopic composition |
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