Reconnaissance geochemical maps of parts of south Devon and Cornwall

A geochemical drainage survey of South Devon and Cornwall was conducted between 1970 and 1976. Efforts were made to maintain a consistent sampling method, but because of improvements in analytical techniques, and changes in instrumentation, there is an unavoidable variation in absolute values from area to area. For this reason the raw data are presented using an expanding polygon display which emphasises local variations in element concentration. The results contain many anomalous concentrations of elements of potential economic value but few of these are likely to be of significance, considering the high level of contamination, from past mine workings and from refuse, which exists in the region. Efforts were made to avoid collecting samples badly contaminated by agricultural or domestic refuse, or at locations immediately downstream of roads. It was considered that, where the drainage was contaminated by mine waste, benefit could be gained from the sample analysis as a check on the records of ore components from that mine. It will be noticed that, in several cases, the presence of ore elements not mentioned in the records is thus brought to light. As one purpose of this survey was to determine if there was any significant mineralisation outside the established mining areas of South Devon and Cornwall, samples were not collected from the most intensively mined areas such as the southern edge of the St Austell Granite.