Au deposition and remobilization in the Muruntau “Central” quartz veins: Evidence from SEM, cathodoluminescence and fluid inclusion data

Native Au from two mining levels of a “Central” quartz vein from the Muruntau deposit has been investigated using scanning electron microscopy and cathodoluminescence microscopy. Fluid inclusions in the surrounding quartz have been studied using microthermometry and laser Raman spectroscopy. Two types of native Au inclusions can be distinguished in the investigated samples. Primary Au (Au I) is characterized by euhedral crystals which occur isolated inside of moderately deformed quartz grains. Probable remobilized Au (Au II) mostly occurs as groups of irregularly formed aggregates that are located at grain boundaries between partly recrystallized quartz grains. The probably remobilized Au is lower in Ag contents than the primary Au. Fluid inclusion investigations suggest the presence of a probable heterogeneous CO₂-bearing fluid during recrystallization of quartz and precipitation of Au II.