Enhanced crustal geo-neutrino production near the Sudbury Neutrino Observatory, Ontario, Canada

The geo-neutrino flux at the Sudbury Neutrino Observatory depends on the local level of crustal radio-activity, which is best estimated from surface heat flux data. The surface heat flux records average crustal radio-activity over the whole crustal column and is unaffected by small-scale heterogeneities. We show how the contribution of crustal heat sources to the geo-neutrino flux can be calculated from knowledge of the surface heat flux. We present new heat flux data from two very deep holes (> 2000 m) in the Sudbury structure as well as measurements of U, Th, and K concentrations in the main geological units of the area. With all available data, the average heat flux in the Sudbury basin is ≈ 53 mW m− 2, higher than the mean value of 42 m W m− 2 for the entire Canadian Shield. The elevated heat flux is due to high heat production in the shallow crust and implies an at least 50% increase of the local crustal component of the geo-neutrino flux relative to that expected for the average crustal composition of the shield.