We have found that carbon can be incorporated into apatite by substituting (with silicon) for phosphorus. We also carefully document different approaches to measurement of carbon in apatite. However, this type of substitution may complicate our efforts to use apatite to infer magmatic CO2 contents!
Anenburg et al. (in press), Silica-substituted carbonate apatite: synthesis and analytical challenges. Journal of Materials Chemistry B, https://durham-repository.worktribe.com/output/4123623