Mineralization and paragenesis at the Mount Wellington Mine, Cornwall

Abstract

The Mount Wellington mine is the most recent to recommence production in the United Kingdom. It lies on the southwestern extension of the Wheal Jane lodes. About half the production comes from the number 1 lode which lies in the footwall of a shallow-dipping elvan sheet. The numbers 2 and 3 lodes have a similar trend but dip more steeply; they join the main lode without intersecting it. These lodes are generally smaller than the number 1 lode but carry higher grades of tin. The remaining mine production comes from the number 2 lode, but the number 3 is at present unpayable. All these lodes have a similar mineralogy and paragenesis. The mineralization took place in four stages. In each lode the minerals of the two earlier phases replace brecciated fault zones and those of the two later phases fill dilatant fractures in the earlier material. These lodes were cut by the mineralized (but uneconomic) Hot lode which may have formed during the later stages of mineralization of the main lodes. All these lodes are cut by two groups of variously mineralized faults called caunterlodes and crosscourses, respectively. Both the main mineralizations and the elvan were controlled by two sets of faults developed around the cooling Carnmenellis granite cupola, probably in response to fluid overpressures.