Multiple episodes of fluid flow in base-metal deposits from southwest Scotland and Northern Ireland

Abstract

Cathodoluminesence zones allow correlation of mineralizing and brecciation events in sulphide-bearing quartz veins from strata-bound base-metal deposits in the Southern Uplands of southwest Scotland and Northern Ireland. Ore-bearing veins are typically associated with NNW–SSE to NW–SE and E–W to NE–SW trending fractures and brittle fault zones. Two main ages of stratabound base-metal mineralization have occurred in this region; a late Caledonian, high temperature phase and a younger low temperature, lower Carboniferous phase. Between three and six cathodoluminescence zones were identified in a number of deposits. The similarity in cathodoluminescence zones developed at different deposits reflects similar broad fluctuations in the chemistry of ore-bearing fluids, correlated over a region of 120km. Multiple episodes of brecciation during quartz and sulphide deposition suggests that faulting was an active process during hydrothermal activity. Quartz from Caledonian mineralization contains cathodoluminescence zones, which are texturally distinct in comparison with the quartz from subsequent lower Carboniferous mineralization.