Original paper
Evidence of growth and sector zoning in hydrothermal quartz from Alpine veins
Jourdan, Anne-Lise Vennemann; Mullis, Josef; Ramseyer, Karl; Spiers, Christopher J.
European Journal of Mineralogy Volume 21 Number 1 (2009), p. 219 - 231
published: Feb 6, 2009
Abstract
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 °C or less and that also display patterns of cyclic growth when examined with cathodoluminescence. In contrast, crystals formed at temperatures closer to 400 °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 z 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.
Keywords
quartz • alpine veins • trace element analyses • sector • growth zoning