Geology and Regional Implications of Carbonatites in the Lemitar Mountains, Central New Mexico

More than 100 carbonatite dikes and veins intrude a complex Precambrian terrain in the Lemitar Mountains, New Mexico. These Ordovician carbonatites are not associated with any alkalic rocks or kimberlites, but they exhibit textures, mineralogy, chemistry, and alteration characteristic of carbonatites. Despite variations in texture, the Lemitar carbonatites can be grouped on the basis of mineralogy, chemistry, and texture as primary-magmatic and replacement silicocarbonatites and rodbergs. The Lemitar silicocarbonatites consist of more than 50% carbonate minerals and varying amounts of accessory minerals, and they are enriched in LREE. The rodbergs consist of more than 50% carbonate minerals, are stained red by hematite, and exhibit flat REE patterns. Carbonate and barite-fluorite-galena veins of uncertain origin are found in the carbonatites and country rocks. Periodic episodes of alkalic magmatism occurred in New Mexico and southern Colorado during the Proterozoic, late Paleozoic, and Tertiary. The Lemit...