Exploration and Interpretation of the SW England Geothermal Anomaly

Abstract

The high magnitudes of. the first reported heat flows in SW England led to serious speculation that deep convective circulation was a possible contributing factor to the measured surface heat flow. Were eonvective circulation to exist, the consequential heat flow enhancement would be localised. The strategy of this research was therefore to extend the coverage of heat flow over the entire Cornubian batholith, and its, environs. This has been achieved through two phases of contract support from the Commission and the UK Department of Energy, In the first phase eleven new heat flow sites were occupied, and in the. seeonx L. phaae twenty-five new sites have been completed, bringing the total coverage for SW England, including six earlier published values, up to a total of forty-two. The uniformly high values associated with the granite (around 120 mWm⁻²) contrast with normal heat flow (around 60 mWm⁻²) at sites remote from the granite. The uniformity of the granite values suggests that conveetive transfer is not a significant mechanism. Furthermore using modal studies it is shown that the observed significant contrasts in thermal conductivity and heat production, combined with the likely space-form of the granite, reasonably account for the observed heat flow distribution. This study therefore reaffirms the Cornubian batholith as the most. favourable UK site for HDR development.