Heat Flux, Crustal Heat Production, and Concentration in Heat Producing Elements Near the Sudbury Neutrino Observatory.

Abstract:

The Sudbury neutrino observatory (SNO) is located in the Creighton mine on the southern rim of the Sudbury impact structure which straddles the boundary between the Archean Superior Province and its PaleoProterozoic margin, the Southern Province. In order to constrain the crustal radioactivity near SNO, we have measured the surface heat flux and heat production within and around the Sudbury structure. We report on heat flux determinations at 6 new sites, which bring the total number of heat flux data around Sudbury to 18. The structure is completely encircled by heat flow sites that are located on its rims or immediately outside. The heat flux values, varying between 42 and 61 mW m^-2, are all higher than the average Superior Province. Their mean is 50.1 mW m^-2 compared to 39.5 mW m^-2 for the entire Superior Province. Such a difference implies that the bulk crustal heat production near the Sudbury structure is ~ 40% higher than the average Superior Province. The mean heat production of rock samples from 12 of the heat flow sites is 1.35 μWm^-3, which is ~ 50% higher than the average surface heat production of the Superior Province (0.8μWm^-3).
The highest heat flux values are found southwest of the structure at sites that are located in the Southern Province, where some sedimentary rock core samples have heat production >3μWm^-3. The variations in heat flux occur over relatively short distances (<20km) implying that they are due to local enrichment in heat producing elements in the upper crust near SNO.