Investigations for tin around Wheal Reeth, Godolphin, Cornwall

Recognition of greisenisation closely associated with worked tin lodes near Wheal Reeth suggested the possibility of unrecorded or undiscovered mineralisation of stockwork or vein-sheet type. Geophysical methods were unable to define either greisenised or mineralised ground and a line of shallow percussive boreholes was drilled to examine the distribution of tin, associated base metals and fluorine in solid rock below surface soils which were potentially highly contaminated by former mining. No economic mineralisation was revealed by the investigation nor was any broadly disseminated metallisationindicated. Not allofthe worked tinbearing structures could be identified from vertical percussion holes but one new vein was located by a combination of vertical and inclined drilling followed by shallow trenching. Results from inclined drillholes outline at least four more stanniferous veins or vein zones to the south of the Lady Gwendolen workings. The depth persistence of mineralisation in nearby Great Work Mine (c.365 m) suggests that some of the Wheal Reeth/Lady Gwendolen veins might repay deeper investigation. Hand-panned heavy mineral concentrates from the drilling samples confirm the presence of only trace quantities of wolframite. They also reveal the ubiquitous enrichment of cassiterite at the base of the regolith cover, a feature which may explain in part the disappointing results obtained by commercial exploration groups when drilling below geochemical tin anomalies located by soil sampling. The distribution of fluorine shows little correlation with that of tin and it is obvious that the Wheal Reeth area does not bear any swarms of greisen veins similar to those seen at Cligga Head. Indeed, it would appear that greisenisation may be only patchily developed along the vein walls.