INSIGHTS INTO THE CHEMICAL, TEMPORAL, AND SPATIAL RELATIONSHIPS OF THE SAN RAFAEL SWELL

Dikes and sills can be challenging to study and observe due to their subterranean origins and the way they weather upon exposure at the surface. To better understand these features, we conducted researched on the near-surface volcanic system in the San Rafael Swell, Utah – an area with well-exposed dike and sill systems. Our study included fieldwork to examine the temporal and spatial relationships of exposed dikes, sills, and volcanic necks, as well as the collection of samples from the interior and edge of an approximately 8-meter-thick sill. Sample locations were chosen to investigate variations in mineralogical and chemical compositions that may occur between the interior and the margins of the sill that would provide insight into potential within-sill magma differentiation. Both samples were analyzed for their chemical and mineral compositions. Specifically, we studied hand samples and thin sections of the samples to identify mineral phases and abundance, prepared the samples for whole-rock major and trace element analysis using X-ray fluorescence (XRF), and prepared samples for analysis of mineral phases present using X-ray diffraction (XRD). Whole-rock chemistry helped classify the sill and offered insight into potential lithospheric contamination, while also enabling comparisons to previous studies of dikes and sills in the San Rafael Swell. Together, the field observations and sample analyses enhanced our understanding of the temporal, spatial, and chemical relationships within near-surface volcanic plumbing systems.