SOURCING GRANITIC GROUND STONE TOOLS FROM BELIZE USING PORTABLE X-RAY FLUORESCENCE

Recent developments in the area of nondestructive geochemical fingerprinting of geologic materials have allowed geoarchaeologists to investigate archaeological aspects of the exchange of rock and ceramic artifacts. A major issue with geochemical sourcing in the past has been that the most commonly available techniques, such as thin sections and laboratory x-ray fluorescence, require the destruction of a significant portion of an artifact. Destructive analyses of archaeological artifacts risks compromising the integrity of the object as well as its potential for future analysis. Portable x-ray fluorescence (PXRF) is a method of nondestructive chemical characterization. Chert, obsidian, and clays used in ceramics have been sourced to outcrop locations with high levels of certainty using PXRF. However at present there are few case studies of PXRF applications for sourcing heterogeneous coarse-grained materials such as granite. Ground stone tools are a burgeoning area of geoarchaeological investigation. As many of these artifacts are composed of heterogeneous materials, they provide an excellent case study for the efficacy of PXRF for sourcing phaneritic rocks. This study utilized several petrographically distinct granite samples from Belize that were collected during May and June of 2013. Whole rock samples were analyzed using PXRF in order to approximate how it would be utilized on archaeological artifacts. In order to assess the ability of PXRF to provide accurate results on coarse-grained materials we prepared and analyze petrographic thin sections of the same rock samples. Results from this study show that it is possible to use the nondestructive PXRF technique in order to separate granite source locations. By conducting a side-by-side comparison of the results of PXRF data and petrographic thin sections this study shows that PXRF provides a quick and nondestructive method of differentiating granitic intrusions in Belize.