(PH) Powderhorn (Iron Hill) Carbonatite Suite -- Gunnison County, SW Colorado

Title

(PH) Powderhorn (Iron Hill) Carbonatite Suite -- Gunnison County, SW Colorado

Description

The Powderhorn (Iron Hill) Carbonatite is located in Gunnison County in about the center of the southwestern quadrant of Colorado. It is a pear-shaped body which is essentially conical at depth, and is exposed over an area of about 12 square miles. The carbonatite body covers about 2 and a half square miles; About 70 percent of the in pyroxenite which was subsequently intruded by or replaced by nepheline and melilite-bearing rocks; magnetite-perovskite, and carbonatite.

Contributor

Western Minerals Inc.

References

Start Here:

Mitchell, R.H., 2014, Primary and secondary niobium mineral deposits associated with carbonatites: Ore Geology Reviews, v. 64, p. 626-641, doi:10.1016/j.oregeorev.2014.03.010. Full Article.

  • Focuses specifically on the formation of niobium in carbonatites but includes an excellent baseline description of carbonatites.
Additional Resources:

Nash, W.P., 1972, Mineralogy and Petrology of the Iron Hill Carbonatite Complex, Colorado: Geological Society of America Bulletin, v. 83, p. 1361-1382, doi: 10.1130/0016-7606(1972)83[1361:MAPOTI]2.0.CO;2. Full Article.

  • Bulk rock chemistry description & maps/diagrams showing the location of rocks in the Powderhorn Carbonatite.
Temple, R.K., Grogran, R.M., 1965, Carbonatite and related alkalic rocks at powder horn, Colorado: Economic geology and the bulletin of the Society of Economic Geologists, v. 60, p. 672-692, doi: 10.2113/gsecongeo.60.4.672. Full Article.
  • Basic information regarding the structure, geochemistry, and petrogenesis of the Powderhorn Carbonatite.

Van Gosen, B. S., Lowers, H. A., 2007, Iron Hill (Powderhorn) carbonatite complex, Gunnison County, CO; a potential source of several uncommon mineral resources: Mining Engineering, v. 59, p. 56-62, doi: N/A Abstract.

  • Mineral resource potential: titanium, iron, vermiculite, vanadium, and nephaline. 

Olson, J.C., Hedland, D.C., 1981, Alkalic rocks and resources of thorium and associated elements in the Powderhorn District, Gunnison County, Colorado: USGS Numbered Series, Professional Paper , v. 1049, p. C1-C34  doi: N/A. Full Article.

  • Extensive report by the USGS regarding rock type and history of formation (geologic ages).

Collection Items

Powderhorn Carbonatite Western Minerals Supplementary Materials
OCR PDF of supplemental information for the Powderhorn Carbonatite collection.

Pyroxenite
Coarse pyroxenite, with traces of nepheline. This is the freshest pyroxenite that was found. It occurs near the nepheline syenite body in the eastern part of the complex.

Gneiss (Fenitized)
Fenitized Gneiss. Gneiss discovered in direct contact with pyroxenite in prospect trench on ridge, about 500 ft. west of PH-1.. .

Nepheline syenite
Nepheline syenite that outcrops on west side of trail at about 9200 ft. on east side line of section.

Nepheline syenite
Nepheline Syenite. Thin, dark vein runs through the center body of the rock.

Carbonatite
White Carbonatite. Found on Southwest side of the main rock unit body on North side of Beaver Creek about 1/4 mi.

Ijolite
Recently exhumed ijolite from shallow bulldozer cut.

Hand Sample: Shows traces of iron oxidation in isolated areas. Small (> 0.5 mm in diameter) nodules, with the appearance of small sand grains appear in clusters on one face of the rock (not…

Ilmenite.
Hand Sample:

Composed entirely of Ilmenite.

Pyroxenite
Hand Sample:

Rock is comprised predominately of a dark fine grained matrix. Some specimens have minor amounts of pink K-feldspar. Clusters of biotite (~1 cm in diameter) appear on one face of the rock.

Gabbro
Coarse gabbro, extracted from the southern dike of two east-west dikes N of Deldardo Creek.

Hand Sample:

Evenly distributed dark, light, and white colored coarse-grained (1 mm) crystals. Obvious traces of oxidation from some metallic mineral…

Porphyroblasic gneiss (Fenitized)
Fenitized porphyroblastic Gneiss.

Hand Sample:

Entirely coarse-grained rock except for 2 cm wide dark fine grained band. Obvious traces of oxidation appear on all sides, dominating the most weathered sides of the rock.

Carbonatite
Light brown to almost off-white fine grained Carbonatite. Delicated Barite appears in very thin layers on one side of the rock.

Chert
Chert sample found in a Carbonatite.

Hand Sample:

Pink to light brown chert sample that contains small (< 1 mm diameter) vesicles. Very thin quartz veins propagate through the sample in no preferred orientation.

Pyroxenite
Hand Sample:

Coarse grained pyroxenite showing heavy traces of oxidation on every weathered face of the rock. Large clusters (5-8 mm) of biotite appear throughout the rock.

Melilite-bearing rock
Hand Sample:

Large (1 cm-2 cm) dark grey to translucent quartz crystals comprise the matrix of the rock. Melilite minerals propagate consistently paralell to one another throughout the rock.

Uncompahgrite
Hand Sample:

Three hand samples from different facies were collected to represent this sample. Out of two of the largest samples one is a dark fine grained rock while the other is coarse grained. Both contain large (5-8 mm) clusters of biotite.

Melilite-bearing rock
Hand Sample:

The rock is largely comprised of a very fine grained light green matrix with large (1 x 3 cm) black equant galena crystals. It's pretty magnificent.

Ijolite
Hand Sample:

Rock is comprised almost entirely K-Feldspar.

Gabbro
Dark gabbro dike separating ijolite and uncompahgrite

Pyroxenite
Hand Sample:

All weathered faces of the rock show heavy traces of oxidation.
View all 21 items

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    • (PH) Powderhorn (Iron Hill) Carbonatite Suite -- Gunnison County, SW Colorado