Criteria,
d¹³C >-8%            PDB: Mantle Source
R(He²/He⁴) > R_A(He²/He⁴ in Atmosphere)
When R < R_A: Metamorphic Origin From Carbonate Rock

with many calcareous tufa
with very few precipitation
re-accumulated as CO₂ reservoir
active faults(the number is the annual displacement)
Fig.1     Three different forms of deep source CO₂ emission in mainland China

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