T. Graupner et al., CL for characterizing quartz and trapped fluid inclusions in mesothermal quartz veins: Muruntau Au ore deposit, Uzbekistan, MINERAL MAG, 64(6), 2000, pp. 1007-1016
Combined cathodoluminescence (CL) and transmitted light microscopy were use
d to characterize quartz from flat and steeply dipping quartz veins and fro
m veinlets in banded host rocks from the giant Muruntau Au quartz Vein depo
sit, Kyzyl Kum Desert, western Uzbekistan. The CL examinations were carried
out using a 'hot-cathode' CL microscope linked to a highly sensitive digit
al video camera. The multi-stage deformed flat quartz veins and the steeply
dipping hydrothermal formations at Muruntau are characterized by quartz wi
th different CL colours, internal structures and degree of secondary altera
tion. Primary growth zoning of quartz, indiscernible in conventional polari
zed light was found to occur only in steeply dipping veins. The bulk of the
high-grade Au mineralized 'central' quartz veins is dominated by one gener
ation of hydrothermal quartz; intense brecciation of these veins is indicat
ed by the occurrence of fragments of zoned quartz crystals. Primary growth
zoning in quartz may be revealed not only by variations in the intensity of
blue CL and/or by primary fluid inclusions arranged within the zones, but
also by secondary inclusions and recrystallization phenomena developed alon
g boundary surfaces between the zones. Using the results from CL imaging an
d microstructural analysis of the quartz, fluid inclusions investigated ear
lier were assigned to genetic types; the evidence of probably primary inclu
sions is of considerable importance for further studies of the geochemical
conditions during vein formation. Considering geological and mineralogical
data, CL studies of vein quartz may help to reveal the history of precipita
tion, deformation and recrystallization processes in the Muruntau Au ore fi
eld.