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Quartz overgrowths from Keuper sandstones of the Paris basin were examined using cathodoluminescence (CL) microscopy and spectroscopy coupled with a scanning electron microscope (SEM). With the use of standard cold CL equipment, it was observed that the emission of authigenic quartz is much less intense than that of detrital quartz grains, but a reversal of intensity was observed with scanned CL in the 200-800 nm range. The main CL emission band of diagenetic quartz is at 330-340 nm in the UV range, with other bands in the visible range. The determination of trace element distributions in authigenic quartz by in situ analyses and by SIMS imagery reveals the correlation of the 330-340 nm emission band with the highest Al and Li contents. The cathodoluminescence emission of diagenetic quartz in the UV range appears to be influenced by the coupled substitution of Al and Li into the crystal. Two explanations are suggested: (1) Al, Li, or both serve as activators, and (2) the incorporation of Al and Li causes lattice defects that lead to an enhancement of the intrinsic luminescence. Trace element analyses and fluid-inclusion studies revealed that quartz overgrowths precipitated from a fluid that partially originated from an Li-enriched primary brine derived from eastern Triassic evaporites of the Paris basin. The specific CL emission band in the UV range can be linked to the diagenetic environment. The chemistry of the fluids appears to be the essential parameter, whereas precipitation temperatures do not influence the occurrence of such emissions.

american mineralogist

Cathodoluminescence of quartz from sandstones: Interpretation of the UV range by determination of trace element distributions and fluid-inclusion P-T-X properties in authigenic quartz