Just a minor point. The reaction CH4=C + H2O requires another substance to react with the CH4.

You are right, Dr. Stevens. The "cooling" reaction should be CH4 = C(s) + H2 (g). On the other hand, the "oxidation" reaction may be written as: CH4 + O2 = C(s) + 2H2O.

Chalcopyrite + pyrrhotite? Any pyrite or arsenopyrite? These minerals with pyrrhotite would indicate the fO2 (Kretschmar and Scott, about 1976). Overall the assemblage appears to be low sulfidation state. Not sure if you are below FMQ; more likely at this temperature, you are close to Ni-NiOx, near the Fe rock buffer. See Einaudi et al., 2003 (attached), although not completely applicable to your situation.

We will cover numerical simulation of redox conditions in ore-forming systems during our upcoming Goldschmidt workshop on fluid-rock interaction. It will be on zoom and is relatively cheap to attend. Maybe that is of intrest to you.

Dear Mr. Baidya,

I have been studying hydrothermal uranium mineral assemblages located in fault- and shearzones at different temperatures and metamorphic conditions and associated with a wide variety of sulfides and arsenides from molybdenite to arsenopyrite and pyrite different in composition with regard to its trace element content.

First and foremost it is important to determine precisely the C-bearing compound which could be in this case kata-impsonite (metamorphic bitumen), semi-graphite and to a lesser extent graphite by crystallographic definition. You must use spectrometric methods in combination with coal petrography to determine the true nature of the C-bearing matter which runs the gamut from epi-impsonite and meta-anthracite to “full-blown” graphite.

For your information I attach Table 1 from

DILL, H.G., KUS J., GOLDMANN S., SUÁREZ-RUIZ I., NEUMANN T., and KAUFHOLD S. (2019) The physical-chemical regime of a sulfide-bearing semi-graphite mineral assemblage in metabasic rocks (SE Germany) – A multidisciplinary study of the missing link between impsonite and graphite. International Journal of Coal Geology 214:

available on the RG server

H.G.D.