caa a22 4500 606149015 CHVBK 20210128100532.0 cr unu---uuuuu 210128e20150101xx s 000 0 eng 10.1007/s00531-014-1063-0 doi (NATIONALLICENCE)springer-10.1007/s00531-014-1063-0 Molecular and isotopic compositions and origin of natural gases from Cambrian and Carboniferous-Lower Permian reservoirs of the onshore Polish Baltic region [Elektronische Daten] [Maciej Kotarba, Keisuke Nagao] Natural gases from Middle Cambrian and Carboniferous-Lower Permian reservoirs of the onshore Polish Baltic region were studied for their molecular and stable isotope compositions. The following gas species were analysed: 12,13C in CH4, C2H6, C3H8, n-C4H10, i-C4H10 and CO2, 1,2H in CH4, 14,15N in N2, and stable isotopes of all noble gases. Due to significantly different geological settings and genetic types of source rocks of Eastern and Western Pomerania, the molecular and isotopic compositions of natural gases of these two regions exhibit distinct differences. Hydrocarbon gases associated with oil accumulated in the Middle Cambrian reservoir of Eastern Pomerania were generated during low-temperature thermogenic processes from a single source rock containing Type-II kerogen at one phase of petroleum generation. Non-associated hydrocarbon gases accumulated in the Carboniferous (Mississippian and Pennsylvanian)-Lower Permian (Rotliegend) reservoirs of Western Pomerania originated during at least two phases of gas generation by thermogenic processes from mainly Type-III kerogen and a small component of mixed Type-III/II kerogen. Noble gases are in general heavily enriched in radiogenic and nucleogenic isotopes such as 4He, 40Ar and 21Ne accumulated in the reservoirs. Weak contributions of mantle-derived He and Ne are observed. Radiogenic 4He/40Ar ratios are higher than the average production rate ratio of about 5 for radiogenic 4He/40Ar in crustal materials, which might have been caused by a selective supply of 4He that is lighter than 40Ar from crustal rocks, or (U+Th)/K ratio might be higher than the average in crustal block. Carbon dioxide from gases of both the Western and Eastern Pomerania were mainly generated during thermogenic processes of transformation of organic matter, although gases of Western Pomerania can contain an endogenic component. Molecular nitrogen from the Eastern Pomeranian natural gases was mainly generated during low-temperature thermal transformation of organic matter and derived from NH3 and NH4 of crustal fluid, whereas molecular nitrogen from Western Pomeranian natural gases contains a significant component from the destruction of organic matter at a higher maturity level which may have been caused by a high heat flux from the volcanic activity during late Pennsylvanian-early Rotliegend ages, and has a bigger component release from NH4-rich illites. The Author(s), 2014 Origin of natural gases nationallicence Hydrocarbon gases nationallicence Noble gases nationallicence Carbon dioxide nationallicence Molecular nitrogen nationallicence Stable isotopes nationallicence Kotarba Maciej Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland aut Nagao Keisuke Geochemical Research Center, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, 113-0033, Tokyo, Japan aut International Journal of Earth Sciences Springer Berlin Heidelberg 104/1(2015-01-01), 241-261 1437-3254 104:1<241 2015 104 531 https://doi.org/10.1007/s00531-014-1063-0 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00531-014-1063-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kotarba Maciej Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland aut NATIONALLICENCE 700 1- Nagao Keisuke Geochemical Research Center, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, 113-0033, Tokyo, Japan aut NATIONALLICENCE 773 0- International Journal of Earth Sciences Springer Berlin Heidelberg 104/1(2015-01-01), 241-261 1437-3254 104:1<241 2015 104 531