Ground-based Hyperspectral Imaging for Fluid-related Diagenetic Heterogeneities and Fluid-flow Pathways in the Wingate Sandstone

Abstract:

The Jurassic Wingate Sandstone show prominent color variations throughout southeastern Utah due to diagenetic changes. The characteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic heterogeneities and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability at outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnostic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparisons of reflectance spectroscopy with ground-based imaging spectroscopy data provided a method for mapping fluid-related diagenetic heterogeneities and fluid-flow pathways in near vertical rock faces of steep outcrops. Additionally, ASTER satellite and HyMap airborne data helped evaluating spatial variations of diagenetic mineral at a broader scale in plan-view. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near-vertical rock faces. The bleached and unbleached areas are alternating throughout the vertical face of the outcrop. The relative hematite abundance observed in the unbleached areas in the vertical section are somewhat symmetrical. This indicates fairly similar reaction intensities along the upper and lower reaction fronts observed in the vertical section. The distribution geometry and relative abundances of diagenetic minerals not only suggest multiple paths of fluid-flow in Wingate Sandstone but also provides some insight about relative direction of past fluid-flow.