Stable isotopes of carbon from basaltic rocks and their possible relation to atmospheric isotope excursions

摘要: Abstract Repeated short-time negative excursions from the general trend of organic carbon isotopes occur at, and shortly after, Permo-Triassic Cretaceous–Tertiary mass extinctions. The cause these is unexplained since an extinction event can only explain one excursion at each boundary. At P/T boundary occurs before proper followed by boundary, several that be correlated in both marine terrestrial environments over larger geographical distances. Also K/T carbon, which correlated, after settings. As extinctions occurred contemporaneously with major continental flood basalts, present study focuses on possible effect eruption basalts atmospheric isotopic budget. compositions forty different time span Albian to Recent, predominantly flood, were measured. composition CO2 gas released generally accepted as being rather heavy (− 5‰ PDB) based observations Hawaii. This strong contrast observed values this study, showed had average value around − 23‰ PDB. Acid digestion HF left a residue elemental range − 24 almost − 28‰ corresponds during stepped heating experiments temperature 200 600 °C. Since basalt molten state has > 600 °C most (i.e. carbon) below temperature, it suggests isotopically component not above temperatures In view recorded − 24‰ for collected between 700 800 °C Mauna Loa, seems assumed − 5‰ unrepresentative basalts. It therefore high intensity volcanic episodes have caused repeated excursions. further suggested non-secular variation pattern through may record activity. episodic nature volcanism precludes causally related secular variations. Elemental four kimberlites yielded similar those Boudouard reaction (2CO = C + CO2) responsible formation carbon.