Geology and mineral resources in the Hopewell and Bromide No. 2 districts, northern Tusas Mountains, Rio Arriba County, New Mexico
Virginia T. McLemore
Vein and replacement bodies (Au, Ag, Cu, Pb, Zn), volcanogenic massive-sulfide (VMS) deposits, iron formations, U-Th-REE veins, and placer gold deposits are found in the Hopewell and Bromide No. 2 mining districts in the northern Tusas Mountains in Rio Arriba County, New Mexico. The mineral deposits are found in Proterozoic rocks that can be divided into four assemblages, 1) Moppin Metavolcanic Complex, 2) Vadito Group, 3) Hondo Group (includes the Ortega Quartzite and an aluminous schist), and 4) granitic intrusive rocks, including the Tres Piedras Granite, Maquinita Granodiorite, granite of Hopewell Lake, trondhjemite of Rio Brazos, and Tusas Mountain Granite. Most of the granites are peraluminous, calc-alkalic and alkali-calcic (i.e., subalkaline) and form trends typical of calc-alkaline igneous rocks. Gold, silver, copper, lead, uranium, and vanadium have been produced from the Hopewell and Bromide No. 2 districts. The known veins, replacements, VMS, placer gold, and iron formations in the Hopewell and Bromide No. 2 districts are too small to be economic today, except perhaps for gold. More exploratory work and chemical analyses are needed to determine the undiscovered potential for gold, U, and REE in the Bromide No. 2 district. Past production from mineral deposits in the Hopewell and Bromide No. 2 districts has not been significant and limited exploration did not encourage additional investigation at the time. There is no potential for silica or kyanite in the Hopewell and Bromide No. 2 districts. The Hondo Group in these districts could have potential for scrap mica in today’s economic market. The increased demand for new raw materials, especially gold, U, and REE, needed for energy technologies, such as solar panels, wind turbines, batteries, and electric motors, in the last few years has led to an increase in exploration and production worldwide, including in New Mexico. Therefore, additional investigation in the Hopewell and Bromide No. 2 districts is recommended to determine the resource potential for these commodities.
- McLemore, Virginia T., 2011, Geology and mineral resources in the Hopewell and Bromide No. 2 districts, northern Tusas Mountains, 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. 379-388.