Ediacaran‐Ordovician Magmatism and REE Mineralization in the Wet Mountains, Colorado, USA: Implications for Failed Continental Rifting

Abstract

The Wet Mountains in south-central Colorado (Figure 1), represent a northwest-trending exposure of Proterozoic rocks. The northern half is well known for thorium and rare earth element (REE) mineralization associated with Ediacaran to Ordovician alkaline intrusions. Three exposed Ediacaran-Cambrian alkaline complexes are recognized: McClure Mountain, Gem Park, and Democrat Creek (Figure 1). These complexes are sequentially cross-cut by Cambrian-Ordovician lamprophyre, syenite, and carbonatite dikes, and mineralized quartz-baritethorite veins (Armbrustmacher, 1988). Syenite dikes were hydrothermally altered and this is hypothesized to be temporally associated with the mineralized veins (Armbrustmacher, 1988). REE mineralization occurs mainly