Geology of mineralization and associated alteration in the Capitan Mountains, Lincoln County, New Mexico
— Virginia T. McLemore and Randall S. Phillips

The Capitan pluton is one of the largest Tertiary intrusives in New Mexico. It is a single-phase but texturally and compositionally zoned pluton that ranges from a roof zone of graphic granite to an intermediate zone of aplite to a core of porphyritic granite. Four types of mineral deposits occur in the Capitan Mountains: (1) iron skarn and vein deposits, (2) manganese veins, (3) vein and breccia deposits of quartz and fluorite, locally with anomalously high concentrations of thorium, uranium, rare-earth elements, gold and silver, and (4) feldspar. Minor alteration is associated with most iron deposits; however, extensive zoned calcsilicate alteration occurs at the Capitan iron deposit. Clay and sericitic alteration is locally associated with the manganese veins and vein and breccia deposits of quartz and fluorite. Field relationships, as well as petrologic, fluid inclusion microthermometry and chemistry, and isotopic data support a magmatic-hydrothermal source for the vein and breccia deposits and the iron skarn deposits. The most important resource in the area is the Capitan iron deposit (Smokey mine). The resource potential for thorium, uranium, rare-earth elements, and locally gold and silver in the vein and breccia deposits of quartz and fluorite veins is uncertain due to lack of subsurface data.