SYN-EXTENSIONAL MECHANISMS OF THE LITTLE GRAND WASH FAULT SYSTEM, GRAND COUNTY UTAH

The study of natural analogs to carbon dioxide sequestration and storage systems has become increasingly important as implementation of these systems is underway to help reduce anthropogenic CO₂ from entering the atmosphere. The Little Grand Wash Fault (LGWF) and Crystal Geyser system is a natural analog for subsurface CO₂ fluid systems, and is used in this study to understand the distribution of faults associated with this system. This research focuses on understanding the mm-m scale structural complexities associated with the calcite/aragonite mineralization events. Previous works have linked the travertine and tufa mounds in the LGWF system to CO₂ circulation and mineralization within the fault system, the mounds are characterized by altered host rock, tufa, travertine deposits, and large calcite/aragonite veins.

Detailed outcrop description and 3D photogrammetry, using Agisoft PhotoScan are used to characterize the cross-cutting relationships and morphology of the mounds. This data will be combined with age dates obtained in a separate study. In outcrop, the veins range in thickness from mm to m in size, and record evidence of multiple stress regimes. The veins cut Mesozoic host rock as complicated mesh structures and Quaternary travertine mound deposits adjacent to slip surfaces and as horizontal and near vertical open mode fractures. The data from scan lines transecting three mounds within the LGWF are used to quantify orientations of complicated mesh structures to understand the regional and localized stress orientations associated with the LGWF. Cross-cutting relationships of veins indicate several episodes of fluid migration and precipitation. A combination of normal faulting and fluid over pressure is proposed as mechanisms for the complicated structures present at LGWF system.