Provenance analysis by single-quartz-grain SEM-CL/optical microscopy

The integration of panchromatic scanning electron microscopy-cathodoluminescence (SEM-CL) with optical microscopy analysis on single quartz grains is a new technique to interpret provenance of quartz-rich sediments. The combination of information gained from SEM-CL on textural features and CL response with information from optical microscopy allows distinction of different quartz types much more easily then with conventional microscopy or color CL analysis. Features visible by SEM-CL include zoning, microcracks, deformation fractures and lamellae, diagenetic crushing, recrystallization, and strength and texture of CL response. Features visible by optical microscopy include embayments, open fractures, extinction behavior, and mono-, poly-, and microcrystallinity. The key is to integrate CL and optical properties of the same quartz grains in order to reduce ambiguities inherent in both techniques used on their own. Our technique is well suited for distinguishing between plutonic, volcanic, and metamorphic quartz in coarse- to medium-grained sand or sandstone. This simple and inexpensive approach can easily be combined with other provenance techniques. In this paper we outline the combined SEM-CL/optical microscopy technique and demonstrate its application with examples from the South Island of New Zealand.