Raman and micro-thermometric investigation of the fluid inclusions in quartz in a gold-rich formation from Lepaguare mining district (Honduras, Central America)

Fluid inclusions in the quartz crystals present in gold-rich veins from central Honduras have been studied by means of micro-thermometry and micro-Raman spectroscopy in order to provide information on the physico-chemical conditions and chemical omposition of the mineralizing fluids. The use of a confocal micro-Raman apparatus allowed to obtain information on the fluid composition, in particular on the gas phase, minimizing the contributions of the host matrix to the Raman signal. The samples studied were collected from an area (Lepaguare mining district, Northern–Central Honduras) rich in ore deposits due to the Cenozoic magmatic activity, where the gold and sulphide mineralization is connected with a system of quartz veins (few decimetres thick) occurring in low-grade metamorphic rocks and produced by hydrothermal fluids. The quartz crystals present in the gold-rich veins often contain fluid inclusions. Four types of fluid inclusions have been observed, but their assemblage in the same clusters and fracture systems, as well as their comparable salinity and homogenization data, suggest that they have the same origin. Micro-thermometry and Raman spectroscopy provide a composition of the mineralizing fluids attributable to the system H2O–NaCl–KCl–CO2–CH4, with temperature and pressure intervals of 210–413 ◦C and 1050–3850 bar, respectively. These data agree with an epigenetic origin of the gold deposit (depth < 6 km) related to granitoid or granodiorite intrusions associated to orogenic environments.