Geochemical exploration in Cornwall and Devon: a review

ABSTRACT Cornwall and Devon host some of the most significant metallic mineralization in the UK and were an obvious location for geochemical research. Professor John Stuart Webb (1920–2007) and his Applied Geochemistry Research Group at Imperial College, London, provided a framework for much exploration through the ‘Wolfson Geochemical Atlas of England and Wales’, as well as a number of related projects. The regional geochemistry was followed-up by a number of commercial and government surveys, mainly using residual soils. These have validated many of the techniques developed at Imperial College although no new mines have resulted. Surveys around the Wheal Jane mine and north of the St. Austell granite have located new areas of mineralization associated with the main phase of vein formation, as well as tourmaline-rich breccias and calc-silicates. The distribution of pathfinder elements for Sn and W deposits is erratic and As enrichment appears to be related to distinct host sediments and granite phases. Base metal exploration has defined areas of enrichment within lower Carboniferous sediments, which were detected in the early Imperial College surveys. Deep overburden sampling defined drill targets which intersected sub-economic mineralization. Gold exploration defined a number of targets which appeared largely to be the result of a number of phases of heavy mineral concentration. An exception was low-grade mineralization in Permian volcanic rocks. Very little work has been done on the subsurface signature of the deposits and their relation to the differing granites. This, which was partly the focus of Webb's early work, is a priority for further study.