Powderhorn District

Location: Colorado, United States (38.321, -107.118 approx.)

Commodities: niobium; tantalum; titanium; rare earth elements; iron; vanadium

Geology

Thorium deposits shown on the geologic quadrangle maps of the Powderhorn district number at least 261. Most are small or low in grade, hence only a minority contribute significantly to total resources. Indicated and inferred reserves of ThO2 total about 10,000 short tons in rock greater than 0.1 percent ThO2 in grade. This estimated tonnage is in 15 deposits including 13 veins and two carbonatite dikes. Larger amounts of thorium are present in lower grade materials. Additional quantities are probably present in deposits as yet undiscovered, which could add significantly to the total resources. (Olson and Hedlund (1981)) Abnormal amounts of thorium are found in the following types of deposits in the Powderhorn district: (1) veins, (2) disseminations in several small granite plutons, (3) a large massive carbonatite body, (4) scattered carbonatite dikes, (5) magnetite-perovskite-apatite bodies, and (6) trachyte dikes. Only resources of the first type, veins, are described in this section of the report. The second and third types are described in other sections of this report. The last three types have been discussed briefly by Hedlund and Olson (1961). (Staatz and others (1979)) The area is underlain largely by metasedimentary and metavolcanic rocks intruded by Precambrian granitic and other igneous rocks. In late Precambrian or Cambrian time, about 570 million years ago, the Precambrian rocks were intruded by alkalic igneous rocks and carbonatite of the complex at Iron Hill and by slightly younger diabase dikes (Olson and others, 1977). Mesozoic sedimentary rocks and Tertiary volcanic rocks originally covered much of the area, but now are exposed only on scattered mesas and ridges where they cover the older rocks. Thorium deposits in the Powderhorn district have been described by Olson and Wallace (1956) and by Hedlund and Olson (1961). The geology of the district and location of thorium deposits are shown on maps by Olson (1975), Hedlund and Olson (1973, 1975), and Olson and Hedlund (1973). The geology of the alkalic igneous complex at Iron Hill has been described by Larsen (1942), Temple and Grogan (1965), Rose and Shannon (1960), and Nash (1972). (Staatz and others (1979))

Published resource estimates

As compiled by USGS USMIN from the cited studies. Resource classes follow the source; "approximate" flags values USMIN reports as approximations. These are not current company reserve statements.

Recorded production

• Powderhorn District: produced 3,630 metric tons of iron (Fe), containing about 3,630 metric tons Fe, 1880–1981 (Olson and Hedlund (1981), Page 30)

Exploration and site history

• Active — Production, 1880–1981 (Olson and Hedlund (1981))
• Exploration — About 250 veins were prospected for thorium, 1950–1956 (Staatz and others (1979))

Record imported from USGS USMIN ver. 4.0 (June 2019). Developments after that date appear on facility records, not here; see the methodology.