Rare earth bearing-minerals of the Petaca district, Rio Arriba County, New Mexico
— Michael N. Spilde, Steve Dubyk, Brian Salem, and William P. Moats


 Ten pegmatites were sampled across the Petaca District of northern New Mexico. Samples were analyzed by electron microprobe to identify composition and mineral type and to determine the presence of rare earth elements (REE). Monazite-(Ce) is present throughout the district and contains significant enrichment of Th, in addition to Ce and other light REE. Thorite and xenotime were found to be enriched in moderately heavy REE. Zircon, while not high in REE, contained significant Hf. Samples of Y-REE-Ta-Nb-Ti oxides were analyzed and then classified using statistical analysis into polycrase­(Y), euxenite-(Y), and samarskite-(Y). Polycrase is a new mineral for the state. Samples of columbite-tantalite group minerals were analyzed and found to be columbite-(Mn). Based on the mineralogy of these pegmatites, they can be classified as NYF pegmatites and are likely derived from shallow A- or I-type granite bodies not yet exposed in the region.

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Recommended Citation:

  1. Spilde, Michael N.; Dubyk, Steve; Salem, Brian; Moats, William P., 2011, Rare earth bearing-minerals of the Petaca district, Rio Arriba County, New Mexico, in: Geology of the Tusas Mountains and Ojo Caliente Area, Koning, Daniel J.; Karlstrom, Karl E.; Kelley, Shari A.; Lueth, Virgil W.; Aby, Scott B., New Mexico Geological Society, Guidebook, 62nd Field Conference, pp. 389-398.

[see guidebook]