Colorado Mineral Belt Revisited— 

An Analysis of New Data 

By Anna Burack Wilson1 and P.K. Sims1 

Open-File Report 03-046 

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial 

standards. Any use of trade names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government. Although these data have been used by the USGS and have been successfully imported 

into a number of database and spreadsheet programs, no warranty, expressed or implied, is made by the 

USGS as to how successfully or accurately the data can be imported into any specific application software 

running on any specific hardware platform. The fact of distribution shall not constitute any such warranty, 

and no responsibility is assumed by the USGS in connection therewith. 

1

 U.S. Geological Survey, Denver, Colorado 

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 
Colorado Mineral Belt Revisited—An Analysis of New Data 

by 

Anna Burack Wilson and P.K. Sims 

The three accompanying plates were presented as a poster session at the 

Geological Society of America’s National meeting, October 29, 2002, in 

Denver, Colorado. The maps are based on digital data sets of geology, 

mining districts, and mineral deposits (extensively revised, edited, and 

corrected, unpublished data compiled by Wilson, 2002) overlain on the 

Proterozoic basement map of Colorado interpreted from aeromagnetic data 

by Sims and others (2001). All the maps were created in MapInfo, a GIS 

software program, and images of the maps were exported to Adobe 

Illustrator v.10. Adobe Acrobat Reader (downloadable free from 

www.adobe.com) is the only requirement for viewing the plates. Open 

GSA_poster_all.pdf and select the plates using the bookmarks, thumbnails, 

or page selection. To plot the maps at full-scale (3 ft X 4 ft) requires a large 

format plotter, but the plates may be resized to print on smaller paper. 

Although much discussed in the literature, maps showing the detailed outline 

of the Colorado Mineral Belt are lacking. Lovering and Goddard (1950) 

show the geology and mines associated with the “Front Range mineral belt”, 

and Sims and Tweto (1963) published the outline of the Colorado mineral 

belt as page-size illustrations. Based on detailed information on the location 

of the Tertiary intrusions and mineral deposits, and on the control provided 

by the Proterozoic structures, all superimposed using GIS data, a new outline 

of the Colorado Mineral Belt is proposed herein. 
Plate 1 includes an index map showing the location of the Colorado Mineral 
 
 

Belt, the abstract text, and the map showing the Colorado Mineral Belt, 
 
 

Cretaceous-Tertiary intrusions and inferred batholiths, mineral districts, and 
 
 

metallic deposits that may be related to the Cretaceous-Tertiary intrusions. 
 
 

Plate 2 includes a simplifed geologic map, explanation for the map shown 
 
 

on plate 1, conclusions, and references. 
 
 

Plate 3 shows two maps, each with the Proterozoic rock units stripped away 
 
 

to better display the relationships of the Proterozoic structures to the 
 
 

Cretaceous-Tertiary intrusions and mineralization. 
 
 

Acknowledgements: 
 
 

We are grateful to the following people, among many others, for their 
 
 

assistance in numerous ways. Eric Anderson for converting the Proterozoic 
 
 

basement map from an unregistered image to a GIS-compatible file. Bill 
 
 

Ferguson for retrieving a useable digital dataset from the mines and 
 
 

prospects databases. Luke Kinch for checking and rechecking references, 
 
 

metadata, converting MapInfo files to ArcView and vice versa, cleaning up 
 
 

the bibliography in the MRDS data, and for suggesting that the poster might 
 
 

fit vertical panels, instead of horizontal ones, and still stay within the 36 in 
 
 

maximum paper width. Terry Klein and Doug Stoeser each reviewed the 
 
 

final digital files. 
 
 
REFERENCES and Selected Data Sources 

Green, G.N., 1992, The digital geologic map of Colorado in ARC/INFO format: U.S. 

Geological Survey Open-File Report 92-507. 

http://pubs.usgs.gov/of/1992/ofr-92-0507/ 

Lovering, T.S., and Goddard, E.N., 1950, Geology and ore deposits of the Front Range, 

Colorado: U.S. Geological Survey Professional Paper 223, 319 p. 

McFaul, E.J., Mason, G.T., Jr., Ferguson, W.B., and Lipin, B.R., 2000, U.S. Geological 

Survey Mineral Databases—MRDS and MAS/MILS: U.S. Geological Survey 

Digital Data Series DDS-52. 

Plumlee, G.S., Streufert, R.K., Smith, K.S., Smith, S.M., Wallace, A.R., Toth, M.I., 

Nash, J.T., Roginson, R., Ficklin, W.H., and Lee, G.K., 1995, Map showing 

potential metal-mine drainage hazards in Colorado, based on mineral deposit 

geology: U.S. Geological Survey Open-File Report 95-0026. 

Sims, P.K., Bankey, Viki, and Finn, C.A., 2001, Preliminary Precambrian basement map 

of Colorado–A geologic interpretation of an aeromagnetic anomaly map: U.S. 

Geological Survey Open-File Report 01-0364. 

http://pubs.usgs.gov/of/2001/ofr-01-0364/ 

Steven, T.A., 1975, Middle Tertiary volcanic field in the southern Rocky Mountains, in 

Curtis, B.F., ed., Cenozoic history of the southern Rocky Mountains: Geological 

Society of America Memoir 144, p. 75-94. 

Tweto, Ogden, and Sims, P.K., 1963, Precambrian ancestry of the Colorado mineral belt: 

Geological Society of America Bulletin, v. 74, no. 8, p. 991-1014. 

Tweto, Ogden, 1979, Geologic map of Colorado: U.S. Geological Survey Special Map, 

scale 1:500,000. 

Wilson, A.B., Spanski, G.T., Crane, M.J., and Woodard, M.D., 2000, Databases and 

spatial data model for mineralized areas, mines, and prospects in the Grand Mesa, 

Uncompahgre, and Gunnison (GMUG) National Forests, Colorado: U.S. 

Geological Survey Open-File Report 00-0298. 

http://pubs.usgs.gov/of/2000/ofr-00-0298/ 
The Colorado Mineral Belt Revisited--An Analysis of New Data 
 
 

ABSTRACT 

New geologic and geophysical data extend our knowledge of the complementary role of inherited zones of weakness in Precambrian basement and Late Cretaceous-Tertiary magmatism in development of the Colorado Mineral Belt (COMB).

the northeast-trending ductile shear zones that localized ore-related igneous activity in

COMB are more abundant than known previously, extend outward laterally to the northwest and southeast, and can account for localizing valuable ore deposits in outlying regions such

as Cripple Creek, Rosita Hills-Silver Cliff, and Summitville.

Mesoproterozoic (ca. 1.4 Ga) as a result of transpressional tectonics. , they followed pre-existing Paleoproterozoic structures.

northwest orientation, which has been poorly understood, had a secondary control on

emplacement of intrusions in the central part of COMB.

Colorado where the mineral belt abruptly widens from a width of about 15 to 60 km to about

140 km. 

Recent geochronologic data indicate that a minor late Tertiary ore-forming event was locally superposed on the two major periods of mineralization:

Tertiary and mid-Tertiary. , episodic magmatism in the region spanned an interval of about 70 m.y. 

interpreted as long-lived magma chambers that spawned both Late Cretaceous-early Tertiary and mid-Tertiary magmas. northwest-trending basement shear zone, exposed in the Gunnison River area. 

by Anna Burack Wilson and P.K. Sims 

U.S. Geological Survey 

U.S. Department of the Interior 

The new data indicate that 

The shear zones formed in the 

Locally A second set of Mesoproterozoic shears of 

This control is most evident in central 

Late Cretaceous-early Accordingly Gravity data indicate that COMB overlies two distinct gravity lows (-300 mg) 

The gravity lows are en-echelon and separated by a prominent 
SCALE 1:750,000 

MAP EXPLANATION 

GENERAL OBSERVATIONS AND CONCLUSIONS: 

· All mineral belts from New Mexico to Idaho and Montana trend northeast 

· Colorado Mineral Belt (COMB) follows inherited zones of weakness in Precambrian rocks 

· Intrusions and ore deposits tend to be at intersections of the NE-trending belt with NW-structures 

· Mesoproterozoic (1.4 Ga) shear zones followed pre-existing Paleoproterozoic structures and localized ore-related hydrothermal 

activity and emplacement of intrusions: 

along NE-trending ductile shear zones 

control on NW shear zones evident where COMB widens. 

· Refined outline of COMB based on intrusions, mining districts, basement structures 

· Three periods of mineralization: 

Late-Cretaceous-early Tertiary (major) 

Mid-Tertiary (major) 

Late-Tertiary superimposed (minor) 

· Batholiths 

interpreted from gravity lows (-300 mg), were source of Late Cretaceous-early Tertiary and mid-Tertiary magmas. 

underlie different basement blocks separated by a NW-trending shear zone 

· Possible left-lateral offset of the COMB along NW structures 

REFERENCES and Selected Data Sources 

Green, G.N., 1992, The digital geologic map of Colorado in ARC/INFO format: 

http://pubs.usgs.gov/of/1992/ofr-92-0507/ 

McFaul, E.J., Mason, G.T., Jr., Ferguson, W.B., and Lipin, B.R., 2000, U.S. Geological Survey Mineral Databases—MRDS and MAS/MILS: 

Geological Survey Digital Data Series DDS-52. 

Plumlee, G.S., Streufert, R.K., Smith, K.S., Smith, S.M., Wallace, A.R., Toth, M.I., Nash, J.T., Robinson, R., Ficklin, W.H., and Lee, G.K., 1995, Map 

showing potential metal-mine drainage hazards in Colorado, based on mineral deposit geology: Report 

95-0026. 

Sims, P.K., Bankey, Viki, and Finn, C.A., 2001, Preliminary Precambrian basement map of Colorado–A geologic interpretation of an aeromagnetic 

anomaly map: -01-0364/of-plate1.pdf 

Steven, T.A., 1975, Middle Tertiary volcanic field in the southern Rocky Mountains, in Curtis, B.F., Cenozoic history of the southern Rocky Mountains: 

Geological Society of America Memoir 144, p. 75-94. 

Tweto, Ogden, and Sims, P.K., 1963, Precambrian ancestry of the Colorado mineral belt: v. 74, no. 8, 

p. 991-1014. 

Tweto, Ogden, 1979, Geologic map of Colorado: 

Wilson, A.B., Spanski, G.T., Crane, M.J., and Woodard, M.D., 2000, Databases and spatial data model for mineralized areas, mines, and prospects in 

the Grand Mesa, Uncompahgre, and Gunnison (GMUG) National Forests, Colorado: 

http://pubs.usgs.gov/of/2000/ofr-00-0298/ 

BASEMENT MAP 

MESOPROTEROZOIC (1,600 – 900 Ma) 

Ygp rocks of Pikes Peak batholith (~1,010 Ma) 

Yl Las Animas Formation 

Yu Unita Mountain Group 

Yun Formation 

Yv Vallecito Conglomerate 

Yg Granitic rocks (~1,400 Ma age group) 

Ygf Foliated granodiorite (~1,400 Ma age group) 

PALEOPROTEROZOIC (2,500 – 1,600 Ma) 

Xg Granitic rocks (~1,700 Ma age group) 

Xm Mafic rocks (~1,700 Ma age group) 

PALEOPROTEROZOIC GNEISS COMPLEX 

Xb Biotite gneiss and migmatite 

Xqs Quartzite and mica schist facies of Xb unit 

Xfh Felsic and hornblendic gneisses 

ARCHEAN (2,500 Ma and older) 

Ag Late Archean rocks 

Agn Late Archean gneiss 

U.S. Geological Survey Open-File Report 92-507. 

U.S. 

U.S. Geological Survey Open-File 

U.S. Geological Survey Open-File Report 01-0364. http://pubs.usgs.gov/of/2001/ofr

Geological Society of America Bulletin, 

U.S. Geological Survey Special Map, scale 1:500,000. 

U.S. Geological Survey Open-File Report 00-0298. 

Uncompahgre