| Description |
Gypsum vein geometry and chemistry are evaluated in the Triassic Moenkopi Formation in order to determine the source of mineral fill and conditions and timing of vein emplacement. Moenkopi veins are similar to veins at Endeavour and Gale craters on Mars. Mapping, geochemical, geometric, and basin analysis techniques are employed to better understand the Moenkopi vein network, assess them as an analog to Mars veins, and update a geologic map of the study area at the 1:24,000 scale.A three-part classification scheme organizes observations by vein geometry, vein distribution, and vein mineralogical characteristics to hypothesize vein network generation and evolution processes. The Moenkopi vein network is geometrically complex, stratigraphically distributed, and exhibits multiple varieties of gypsum. Moenkopi veins have similar Sr and S isotope ratios as primary Moenkopi gypsum beds and are interpreted to be sourced from with the unit. Moenkopi veins are dominantly horizontally oriented and cross-cut other diagenetic features and are interpreted to have been emplaced via hydraulic fracturing at <1 km depth during Colorado Plateau uplift <8 Ma.Mars veins share many geometric, textural, and mineralogical features with Moenkopi veins. Endeavour Crater veins appear to be lithologically distributed and are oriented to the crater rim and are interpreted to be sourced from early diagenetic sulfate and to have been emplaced during topographic collapse of the crater rim. Gale Crater veins appear to be stratigraphically distributed and to be subtly dominantly horizontally oriented and are interpreted to be sourced from an as-yet unobserved stratigraphic unit and to have been emplaced during exhumation. Mars and Moenkopi veins were emplaced via hydraulic fracturing at low confining pressures and low temperatures and have been minimally altered since emplacement.An updated map of the Torrey 7.5' quadrangle, Wayne County, Utah includes mapping and descriptions of extensive Triassic through mid-Jurassic sedimentary, Noegene igneous, and covering Quaternary units. The Torrey map provides context for understanding Moenkopi veins and provides a more nuanced picture of geomorphic evolution in the Pleistocene, including alluvial surfaces that were were emplaced ~100- 550 ka and represent episodes of mass wasting and fluvial activity. |
