Integrating Cathodoluminescence into an Undergraduate Geology Curriculum

Article excerpt

ABSTRACT

Cathodoluminescence (CL) is fast becoming a very common research tool in the geosciences. The introduction to and use of the technique in undergraduate courses is a reasonable beginning. Students will have the opportunity to become familiar with the multiple applications of CL before the start of research projects and/or careers. Mineralogy is a logical course for the first exposure to the instrumentation. Once a foundation is developed, the possibilities for further use in courses and independent studies are numerous. With incremental exposure to the theory, basic applications, instrumentation, software, and finally image acquisition, the potential fear of such instrumentation can be minimized. CL has been successfully included in Mineralogy and Geochemistry courses so far at Illinois State University but this is only the beginning. In addition to the knowledge of CL and its applications, confidence in the use of seemingly difficult instrumentation will serve all students well during and after their undergraduate careers.

INTRODUCTION

Cathodoluminescence (CL) has traditionally been used in carbonate petrology studies (e.g. Amthor, 1993; Pollock et al., 2006) but this technique is rapidly expanding into clastic sediment provenance studies (e.g. Schieber and Wintsch, 2005). CL can also be applied to high temperature geologic materials such as igneous and metamorphic rocks (e.g. Okumura et al., 2005; Wark and Spear, 2005), ore deposits (e.g. Wilkinson, 2003), gems (e.g. Bulanova et al., 1986; Harlow et al, 2005), and geochronology (e.g. lizuka et al., 2006; Zhang et al., 2006). On the more applied side of science, the Federal Bureau of Investigation relies significantly on CL image analysis not only for provenance of traditional samples such as soils, concrete, and sand but also nontraditional samples such as paint, explosives, and duct tape (Palenik and Buscaglia, 2005). The wide range of CL applications in the geosciences create the opportunity to incorporate the technique in a variety of courses within the undergraduate Geology curriculum.

Across scientific disciplines, colleges and universities are increasing the integration of instrumentation in undergraduate education. The use of instrumentation in undergraduate education increases awareness to the real-world impacts of science (Miller et al., 2004). Instrumentation also provides a visual approach to comprehending data that can increase understanding beyond traditional methods of data presentation (Steeruer, 1998). The use of instrumentation early in an education allows students to become familiar with techniques that will be valuable not only throughout their undergraduate career but also in graduate school or industry positions (Cancilla, 2004; Miller et al., 2004). Knowledge of modern analytical techniques and proficiency in their uses are important goals for undergraduate programs.

CL has been only nominally mentioned in the Geoscience education literature despite its widespread use in research. Kopp (1981) presented an introduction to the applications or CL in geological research, but not a geology curriculum. Amthor (1993) provided examples of how CL imagery is used for carbonate petrography, in conjunction with backscattered images, but included no discussion on how to incorporate this technique beyond a single application. The purpose of this paper is to provide details on how CL has been incorporated into two courses at Illinois State University and now this can serve as a springboard for use in otner courses in our Geology program. All the exercises and assignments described here are for the Luminoscope ELM-4 with a Diagnostic Instruments SPOT Insight Firewire digital camera at Illinois State University (Figure 1). The benefits of the ELM-4 are that students can see true color CL emissions and the equipment is nearly an order of magnitude less expensive to acquire than a scanning electron microscope (SEM) (approximately $25,000 for the ELM-4 and camera if an appropriate microscope is already in place). …