Growth related zonations in authigenic and hydrothermal quartz characterized by SIMS-, EPMA-, SEM-CL- and SEM-CC-imaging

Authigenic quartz overgrowths and hydrothermal quartz crystals from locations in Oman and Switzerland have been investigated with SIMS, EPMA, SEM-CL and SEM-CC. All techniques reveal similar zonation patterns with SEM-CL having the best resolution followed by SEM-CC, EPMA and finally SIMS. The observed zonations reflect chemical and/or physical changes during growth in the precipitation environment or disequilibrium precipitation at the crystal surface (i.e. sectoral and intrasectoral zonation). Based on the total Al content, two types of authigenic quartz are distinguishable. When the Al concentration is <500 mu g g (super -1) , the predominant CL emission is at approximately 630 nm; in such quartzes, SEM-CL and SEM-CC are directly correlated, and signal intensities drop as a function of increasing Al concentration. In contrast, authigenic quartz with Al concentrations between 500 mu g g (super -1) and 1000 mu g g (super -1) has CL emission maxima at both approximately 630 nm and approximately 380-400 nm, at which point the panchromatic SEM-CL and SEM-CC intensities become decoupled.