Helium accumulation in groundwater, III. Limits on helium transfer across the mantle-crust boundary beneath Australia and the magnitude of mantle degassing

摘要: Abstract The groundwaters of the Great Artesian Basin (Australia) have been previously shown to be accumulating in-situ production helium for ages 100 kyr [1,2]. New isotope measurements show that observed (3He/4He∼ 1.6 × 10−8) is isotopically distinct from crustal degassing flux 6.6 10−8). Furthermore, ratio marginally in excess whole (3He/4He= 3.5 and a variety continental rock types. This suggests upper limit on volatile transport across mantle-crust boundary beneath (relatively) stable “complacent” Australian continent can characterized by “conductive-diffusive” helium/heat ≲ 2.6 1064He atoms mW−1 s−1 which two orders magnitude less than “intrusive-volcanic” 2.9 1084He measured at Galapagos [16]. These results constrain transcrustal mantle fluxes of4He and40Ar much mid-ocean ridge fluxes; are crust. Thus, Earth's interior dominated magmatic processes but dominant atmosphere must come