A fission xenon component with isotopic composition resembling that of the Renazzo-type fission xenon (CCF) was released at 800 and 1,200°C from a 17.971-gram sample of norite from Sudbury, Ontario, Canada. The presence of CCF was also noted in Wausau, Wisconsin, granite. The siderophilit superheavy elements (possibly Z = 114, 115, 116) may have decayed in the earth's iron core and the xenon isotopes became trapped in the crustal rocks. The results can also be explained, however, as due to the fact that the xenon isotopes produced by spontaneous fission of 238U were mass-fractionated and heavier xenon isotopes were preferentially released from the rocks at temperatures 800 to 1,200°C.