Investigations of the UK heat flow field (1984-1987)

Between 1984 and 1987, twenty-two new heat flow measurements have been added to the previously reported coverage of around 200 observations. These include observations in two deep boreholes drilled as part of the BGS geothermal exploration programme. Eleven of the sites were specially drilled heat flow boreholes between 100 m and 300 m deep. The remaining observation were made in exploration boreholes at locations where additional refinement of the heat flow field was warranted. Much of the effort in the present programme has been towards a better definition of the heat flow field associated wit~ the high heat producing granites of the Lake District and Weardale, particularly where the granite extends in the subsurface to the edge of the Tyneside urban conurbation. The apparent high heat flow in the Bowland Forest can no longer be sustained, and the previously reported high heat flows are judged to be enhanced through convective circulation. Some refinements of the heat flow field in the Midland Valley of Scotland and in South Wales have resulted from new observations in these areas. Elsewhere the new observations have been in substantial agreement with the results of earlier work. The results from two shallow boreholes to test basement heat flow were inconclusive in the complex geological settings selected.