Paleoproterozoic positive δ13Ccarb excursion in the northeastern Sino-Korean craton: Evidence of the Lomagundi Event

摘要

The 2.33-2.06Ga positive δ~(13)C_(carb) excursion, associated with environmental change and the breakup of the Kenorland or Superia supercontinent, is called the Lomagundi or Jatulian Event or Great Oxidation Event, and has been reported in many Early Precambrian cratons, but not yet in the Sino-Korean craton. The Guanmenshan Formation of the Liaohe Group occurs in the northeastern part of the Sino-Korean craton. δ~(13)C_(carb) and δ~(18)O values in 42 samples from this formation range from 3.5-5.9‰ (V-PDB), and 15.4-24.8‰ (V-SMOW), respectively, showing a clear positive δ~(13)C_(carb) excursion that characterizes the Lomagundi Event. Thirty-five of the 42 samples with less hydrothermal alteration have higher δ~(13)C_(carb) and δ~(18)Ocarb values than the other 7 samples obviously affected by fluid flow, confirming that it was fluid flow that reduced the δ~(13)C_(carb) and δ~(18)Ocarb values. This positive δ~(13)C_(carb) excursion places deposition of the Guanmenshan Formation within the age range of 2.33-2.06Ga.