Argon-36 from Neutron Capture on Chlorine in Nature

Argon analysis on samples of sodalite from Dungannon, Ontario reveals an excess of 36Ar from neutron capture on 35Cl and excess 40Ar from the decay of 40K. These results indicate an average production rate of 5.6 X 102 atoms of 30Cl per year per gram of chlorine over the age of the mineral. 3.9 X 108 yrs. The surface residence time of chlorine-rich rocks may be determined from the amounts of 36Ar which accumulate during the time period of exposure to cosmic rays