Vitrinite suppression

This could suggest either that conversion of the vitrinite is suppressed by other components in the coal, particularly at the lower pressures, or more likely, that other macerals are participating to an increasing extent as the hydrogen pressure increases. 

If sufficiently abundant, this material can cause suppression of vitrinite reflectance and will fluoresce under UV/blue light when immature (Price Barker 1985 Wilkins et al. 1992). With increasing maturity all the components in Fig. 4.3 become increasingly similar in chemical composition and follow evolution paths leading towards the origin. The chemical changes lead to... 

Price L.C., Barker C.E. (1985) Suppression of vitrinite reflectance in amorphous rich kerogen—a major unrecognised problem.J. Pet. Geol. 8, 59—84. 

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