INTEGRATING AUTOMATED MINERALOGIC AND PETROGRAPHIC ANALYSIS OF MODERN SAND

Methods for determining and categorizing the modal composition of sand and sandstone have long been a subject of debate in the field of sedimentary geology. The traditional approach of point counting is effective at quantifying modal composition but has several drawbacks, including the loss of textural data, such as grain size, sorting, and shape, all of which play an important role in diagenesis and in influencing reservoir quality. Additionally, the categorical nature of point counting results in a lack of specificity and potential loss of valuable data regarding intra-grain mineral relationships, which could be useful in provenance analysis.

The TESCAN Integrated Mineral Analyzer (TIMA) can address some of the deficiencies associated with traditional point counting by providing discrete mineral maps of any petrographic slide. Unlike traditional approaches, however, TIMA cannot distinguish between chemically similar minerals or identify lithic fragment types. This study explores the potential of integrating TIMA data with traditional point counting methods to preserve and incorporate as much information as possible when determining the modal composition of sand and sandstone.

Twelve samples of modern sands featuring a diverse suite of compositions and textures have been prepared. Preliminary results indicate that by using ImageJ, ArcMap, and Python scripts, individual grain TIMA scans can be extracted from a sample and viewed in context with plane- and cross-polarized grain images. The mineralogic composition and morphology (size, shape) of each grain can be calculated and compared to other grains from the same sample. Early work has demonstrated that multidimensional analysis is an effective approach in evaluating inter-grain mineral relationships in a sample. A more quantitative and unambiguous method of determining the modal composition of sand and sandstone, one that preserves textural data and inter-grain relationships, will allow us to better reconstruct the provenance of ancient and modern sediments.