Several quartz crystals from three different Alpine vein localities and
of known petrologic setting and evolution have been examined for
possible elemental sector zoning in order to help to constrain the
mechanisms of such trace element incorporation.
Using different in situ techniques (EMPA, LA-ICPMS, SIMS,
FTIR-spectroscopy), it was established that Al and Li concentrations can
exceed several hundreds of ppma for distinct growth zones within
crystals formed at temperatures of about 300 degrees C or less and that
also display patterns of cyclic growth when examined with
cathodoluminescence. In contrast, crystals formed at temperatures closer
to 400 degrees C and without visible cyclic growth have low
concentrations of Al and Li as well as other trace elements. Al and Li
contents are correlated along profiles measured within the crystals and
in general their proportion does not change along the profiles. No
relationships were found between Al, Na, and K, and germanium has a
qualitative relationship with Al. FTIR spectra also show OH(-)
absorption bands within the quartz, with higher amplitudes in zones rich
in Al and Li.
Sector zoning is present. It is most pronounced between prismatic and
rhombohedral faces of the same growth zone, but also between the
rhombohedral faces of r and z, which contain different amounts of trace
elements. The sector zoning is also expressed by changes in the Li/Al
ratio, with higher ratios in 17 compared to r faces. It is concluded
that the incorporation of trace elements into hydrothermal quartz from
Alpine veins is influenced by growth mechanisms and surface-structures
of the growing quartz crystals, the influence of which may change as a
function of temperature, pH, as well as the chemical composition of the
fluid.