Fluid inclusion petrography

A procedure of fluid inclusion studies is proposed with emphasis on the criteria of selecting fluid inclusions for detailed (microthermometry and spectroscopic) analysis. An overview of descriptive and genetic classifications of fluid inclusions in single crystals and in massive rocks is given with the intention of further differentiating the commonly used terms ‘primary’ and ‘secondary’ fluid inclusions. Some principles of fluid inclusion modification are explained. Cathodoluminescence (CL) studies of quartz with the optical high-power CL-microscope and the electron microprobe provided with a CL detector are an important help in ‘fluid petrography’. CL textures are subdivided in primary, growth textures and a wide variety of secondary microtextures, which are in part induced by fluid inclusions. The latter is grouped in textures indicative of local lower crystal order (increasing defect structures) and microtextures indicative of local quartz healing (reduction of the defect structures). Microtextures showing the genetic relationship between fluid inclusions and the host mineral provide information about the possible post-entrapment changes of fluid inclusions and therewith testify their geological relevance.