Caballo Mountains

Anomalously radioactive potassic dykes occur in quartz monzonites of the southern Caballo Mountains. More than 45 of these bodies have been mapped within an area of 5x2 km (Staatz et al., 1965, Fig. 1). They consist chiefly of brick-red microcline. Thorite and locally uranophane are responsible for the radioactivity and fluorocarbonate and bastnaesite were found in one occurrence. It has been postulated that these rocks are fenites produced by solutions migrating from an alkaline body at depth.