Fig. 6. Diagrams showing δ13CC2 versus δ13DCH4 (a) and δ13CCH4 (b) of coalbed gases in AA-1 core samples. The coalbed gases of AA-1 core samples (red solid circles) were plotted to non-marine coal-type gas or a mixture of microbial and coal-type gases in the genetic fields (Liu et al., 2019). Coal-type gases in the Bohai Basin samples (blue solid circles) were distinguished from microbial gases in the Qaidam Basin (green solid circles), China (Liu et al., 2019).
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