Fluid inclusion petrography of SW England granites and its potential in mineral exploration

Abstract

Fluid inclusions in granite quartz from SW England provide a record of the complex and protracted hydrothermal history of this important metallogenic province. Regional variations in terms of the different types of inclusions can be correlated on an inter-pluton scale with both the texture of the host granite and the extent to which it is mineralized. On an intra-granite scale those areas where mineralization is particularly pronounced show a higher overall inclusion abundance than areas where little or no mineralization is known to occur. The types of fluid inclusion most commonly related to Sn-W-Cu mineralization are halite-free, moderate temperature inclusions. Inclusions containing visible CO2 at room temperature are restricted to two localities in SW England. Both of these contain stockwork/vein-swarm tungsten mineralization. These regional ‘fluid inclusion anomalies’ show that fluid inclusion petrography using a simple petrographic microscope has potential application in the field of mineral exploration.