Natural CF4 and SF6 on Earth

Abstract

The occcurrence of CF4 and SF6 in natural fluorites (CaF2) is reported. Contents are found to be typically 200-2000 ppt-mass for CF4 and 50-100 ppt-mass for SF6. CF4 and SF6 were also detected in granites where fluorite is an accessory mineral. CF4 and SF6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt-mole and up to 0.01 ppt-mole, respectively. The article also discusses how natural SF6 may cause interference in hydrological tracer studies.