PRELIMINARY INVESTIGATIONS ON THE MINERALOGIC, STRUCTURAL, AND GEOPHYSICAL PROPERTIES OF A FLUORITE-GALENA-BARITE DEPOSIT IN WESTERN COLORADO/ EASTERN UTAH

Preliminary research along the northwestern edge of the Uncompahgre Plateau in the Piñon Mesa, Colorado and Ryan Park, Utah areas along the Colorado-Utah border indicates that an epithermal system temporally related to the Uncompahgre Uplift and La Sal Mountains potentially exists in the subsurface. This area hosts intensely silicified zones in the overlying Jurassic sandstones and metalliferous sulfide and oxide minerals present in veins and as a fault-breccia matrix along with fluorite and calcite, but no geologic investigations have been undertaken in the area since small-scale mining prospectives stopped in the early-mid 20^th century. By conducting magnetic surveys of the research area, a REE analysis of fluorite-rich vein deposits, and a structural analysis of the faults that host the mineralization, we hoped to tease out further information regarding the tectonic development of the area, and the potential for base metal mineralization at depth. Analysis of the REE found in the fluorite indicates two phases of hydrothermal mineralization at depth, with phase 1 being deposited under higher temperatures and reducing conditions, and phase 2 being deposited at lower temperatures and oxidizing conditions. The application of ground-based, high-resolution magnetic surveying has identified two separate magnetic anomalies that could potentially be magmatic intrusions related to the nearby La Sal Mountains laccolith, or unoxidized ore bodies present at depth. The structural data collected in the Ryan Park area indicates initial left-lateral movement that has transitioned to a normal-oblique left-lateral movement as the Uncompahgre Plateau formed during Late Laramide to early Post-Laramide events, which could have created additional open space at depth for the emplacement of an intrusive body or further mineralization. These three avenues of investigation lead us to believe that there is potentially an igneous intrusion or mineralized body at depth that could be related to adjacent Cenozoic porphyries that have known base metal mineralization, like the San Juan mountains to the East, and the La Sal and Henry Mountains to the West.