Diffusively disseminated hydrogen-hydrocarbon gases in rocks of nepheline syenite complexes

The composition and concentrations of gases disseminated in rocks (and moving through them mainly via diffusion) and characteristics of their release from these rocks were studied in the Khibina and Lovozero massifs in the Kola Peninsula. Similar to fluid inclusions occluded in vacuoles in minerals and unlike local “jet” gas exhalations, diffusively disseminated gases (DDG) ubiquitously occur in the massifs in variable concentrations. Along with predominant methane and hydrogen, subordinate amounts of methane homologues, and helium, DDG most commonly contain carbon dioxide (in higher concentrations than gases in other modes of their occurrence). One of the most important factors controlling the spontaneous release character of diffusively disseminated gases and their proportions of individual components is the geomechanical state of the rocks. It is proved that the distributions of all modes of gas occurrence in the rocks are generally not interrelated, and hence, it is senseless to utilize the contents of occluded and forcibly extracted gases to predict hazardous gas emissions in mines during the development of mineral deposits related to nepheline syenite complexes.