Economic and Environmental Geology

Fig. 5.

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Fig. 5. Diagram showing combined δ13CCH4 and hydrocarbon index (CHC=C1/C2+C3, Kotarba and Rice, 2001) of coalbed gases in AA-1 core samples. The coalbed gases of AA-1 core samples (red solid circles) are plotted to early mature thermogenic gas or mixing of microbial and thermogenic origins in the genetic fields (Milkov and Etiope, 2018). CR: CO2 reduction, EMT: early mature thermogenic gas, LMT: late mature thermogenic gas, MF: methyl-type fermentation, OA: oil-associated thermogenic gas, SM: secondary microbial. Bohai Bay Basin, China (blue solid circles, Liu et al., 2019), Qaidam Basin, China (green solid circles, Liu et al., 2019).
Econ. Environ. Geol. 2022;55:261-71 https://doi.org/10.9719/EEG.2022.55.3.261
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