A petrographical and geochemical study of quartzose nodules, country rocks, and dike rocks from the Upheaval Dome structure, Utah

Upheaval Dome, in Canyonlands National Park, Utah, USA, is a unique structu re on the Colorado Plateau. It has earlier been interpreted as an impact st ructure or as a pinched-off salt diapir. Some subrounded quartzose fragment s were found in a ring depression near the eastern margin of the structure and, based on vesicularity and apparent flow structure, the fragments were interpreted by early researchers as "impactites." Our petrographic studies show no indication of a high-temperature history and are in agreement with a slow, low-temperature formation of the quartz nodules. Compositionally, t he lag deposit samples are almost pure SiO2. They show no chemical similari ty to any of the possible target rocks (e.g., Navajo Sandstone), from which they should have formed by melting if they were impactites. Instead, the s amples have relatively high contents of elements that indicate fluid intera ction (e.g., hydrothermal growth), such as As, Sb, Ba, and U, and show posi tive Ce anomalies. Thus, we interpret the "lag deposit samples" as normal l ow-temperature (hydrothermally-grown?) quartz that show no indication of be ing impact-derived. In addition, a petrographic and geochemical analysis of a series of dike samples yielded no evidence for shock metamorphism or a m eteoritic component.