Chicago Basin Disseminated Molybdenum Deposit

The Chicago Basin Disseminated Molybdenum Deposit is a molybdenum mine located in La Plata county, Colorado at an elevation of 11,499 feet.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

Satelite View

MRDS mine locations are often very general, and in some cases are incorrect. Some mine remains have been covered or removed by modern industrial activity or by development of things like housing. The satellite view offers a quick glimpse as to whether the MRDS location corresponds to visible mine remains.

Site Name

Primary: Chicago Basin Disseminated Molybdenum Deposit

Commodity

Primary: Molybdenum
Secondary: Copper
Secondary: Lead
Secondary: Zinc
Tertiary: Manganese

Location

State: Colorado
County: La Plata
District: Needle Mountain (Tacoma, Florida, Vallecito) District

Land Status

Land ownership: National Forest
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.
Administrative Organization: San Juan N. F.

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Occurrence
Operation Type: Unknown
Discovery Method: Ore-Mineral In Place
Years of Production:
Organization:
Significant: N
Deposit Size: S

Physiography

General Physiographic Area: Rocky Mountain System
Physiographic Province: Southern Rocky Mountains

Mineral Deposit Model

Model Name: Climax Mo

Orebody

Not available

Structure

Type: R
Description: San Juan Uplift, San Juan Basin, San Juan Volcanic Field

Type: L
Description: Needle Mtns Uplift, Chicago Basin Stock, Eolus Batholith, Trimble Stock

Alterations

Alteration Type: L
Alteration Text: See Comments

Rocks

Name: Granite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 10.100000+-1.100000
Material Analyzed: Zircon
Age Young: Miocene

Name: Granite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 1466.000000+-27.000000
Dating Method: Rb-Sr
Age Young: Precambrian

Name: Granite
Role: Host
Age Type: Host Rock Unit
Age in Years: 1460.000000+-70.000000
Dating Method: K-Ar
Age Young: Precambrian

Name: Granite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 9.000000+-0.900000
Material Analyzed: Zircon
Age Young: Miocene

Name: Granite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 1466.000000+-20.000000
Dating Method: U-Pb (zircon)
Material Analyzed: Zircon
Age Young: Precambrian

Name: Rhyolite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 10.100000+-1.100000
Material Analyzed: Zircon
Age Young: Miocene

Name: Rhyolite
Role: Host
Age Type: Associated Rock Unit
Age in Years: 9.000000+-0.900000
Material Analyzed: Zircon
Age Young: Miocene

Name: Granite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 10.100000+-1.100000
Material Analyzed: Zircon
Age Young: Miocene

Name: Granite
Role: Associated
Age Type: Host Rock Unit
Age in Years: 1460.000000+-70.000000
Dating Method: K-Ar
Age Young: Precambrian

Name: Granite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 9.000000+-0.900000
Material Analyzed: Zircon
Age Young: Miocene

Name: Granite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 1466.000000+-20.000000
Dating Method: U-Pb (zircon)
Material Analyzed: Zircon
Age Young: Precambrian

Name: Granite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 1466.000000+-27.000000
Dating Method: Rb-Sr
Age Young: Precambrian

Name: Rhyolite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 10.100000+-1.100000
Material Analyzed: Zircon
Age Young: Miocene

Name: Rhyolite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 9.000000+-0.900000
Material Analyzed: Zircon
Age Young: Miocene

Name: Quartz Monzonite
Role: Associated
Age Type: Host Rock Unit
Age in Years: 1460.000000+-70.000000
Dating Method: K-Ar
Age Young: Precambrian

Name: Quartz Monzonite
Role: Associated
Age Type: Host Rock Unit
Age in Years: 1466.000000+-20.000000
Dating Method: U-Pb (zircon)
Material Analyzed: Zircon
Age Young: Precambrian

Name: Quartz Monzonite
Role: Associated
Age Type: Host Rock Unit
Age in Years: 1466.000000+-27.000000
Dating Method: Rb-Sr
Age Young: Precambrian

Name: Quartz Monzonite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 10.100000+-1.100000
Material Analyzed: Zircon
Age Young: Miocene

Name: Quartz Monzonite
Role: Associated
Age Type: Associated Rock Unit
Age in Years: 9.000000+-0.900000
Material Analyzed: Zircon
Age Young: Miocene

Analytical Data

Analytical Data: SCHMITT AND RAYMONDS RAPID ROCK ANALYSES OF 4 SAMPLES OF LEAST ALTERED OLDER PORPHYRY: 76.4 TO 78.2% SIO2, 11.5 TO 12.5% AL203, 0.06 TO 0.39% FE203, 0.12 TO 0.28% FEO, 0.06 TO 0.15% MGO, 0.02 TO 0.18% CAO, 1.0 TO 2.8% NA2O, 6.3 TO 7.3% K20, 0 TO 0.17% H2O-, 0.63 TO 1.8% H2O+, 0.12 TO 0.15% TIO2, 0 P2O5, 0 TO 0.02% MNO, LT 0.05 TO 0.06% CO2.
Analytical Data: ONE SAMPLE OF ALTERED YOUNGER PORPHYRY: 77.8% SIO2, 14.0% AL2O3, 0% FE2O3, 0.45% FEO, 0.21% MGO, 0.10% CAO, 0.04% NA2O, 2.6% K2O, 0.19% H2O-, 3.5% H2O+, 0.30% TIO2, 0.02% P2O5, 0% MNO, 0.05% CO2.
Analytical Data: TWO SAMPLE S OF LEAST ALTERED YOUNGER PORPHYRY: 73.5 TO 74.3% SIO2, 13.6 TO 14.2% AL2O3, 1 TO 1.1% FE2O3, 0.32 TO 0.40% FEO, 0.18 TO 0.31% MGO, 0.30 TO 0.40% CAO, 2.3 TO 2.4% NA2O, 5.1 TO 5.2% K2O, 0.29 TO 0.51% H2O-, 1.3 TO 1.5% H20+, 0.24 TO 0.27% TIO2, 0.03 TO 0.06% P2O5, 0.02 TO 0.05% MNO, LT 0.05 TO 0.08% CO2.
Analytical Data: FOUR SAMPLES OF ALTERED OLDER BRECCIATED ROCK:76.2 TO 80.3% SIO2, 12.0 TO 14.4% AL2O3, 0.47 TO 2.4% FE2O3, 0.12 TO 0..36% FEO, 0.06 TO 0.55% MGO, 0.09 TO 0.43% CAO, 0.05 TO 0.16% NA2O, 0.61 TO 4.0% K2O, 0.05 TO 0.25% H2O-, 1.6 TO 2.7% H2O+, 0.27 TO 0.41% TIO2, 0.06 TO 0.15% P2O5, 0 TO 0.04% MNO, LT 0.05 TO 0.05% CO2.
Analytical Data: SIX SAMPLES OF ALTERED OLDER PORPHYRITIC ROCK: 78.4 TO 79.9% SIO2, 11.9 TO 13.6% AL2O3, 0.14 TO 0.94% FE2O3, 0.12 TO 0.40% FEO, 0.12 TO 0.55% MGO, 0.07 TO 0.61% CAO, 0.03 TO 0.37% NA2O, 3.2 TO 4.0% K2O, 0.02 TO 0.12% H2O-, 1.7 TO 2.6% H2O+, 0.13 TO 0.22% TIO2, 0 TO 0.05% P2O5, 0 TO 0.04% MNO, LT 0.05 TO 0.05% CO2.

Materials

Ore: Galena
Ore: Molybdenite
Ore: Pyrite
Ore: Chalcopyrite
Ore: Tetrahedrite
Ore: Sphalerite
Gangue: Sericite
Gangue: Pyrophyllite
Gangue: Dickite
Gangue: Kaolinite
Gangue: Quartz
Gangue: Rhodochrosite

Comments

Comment (Deposit): THAN CENTER: RELATIVE ENRICHMENT OF SIO2 AND H2O AND RELATIVE DEPLETION OF FE2O3, CAO, NA2O, AND K2O. LEAST ALTERED SAMPLES OF YOUNGER PORPHYRY PLOT BETWEEN LEAST ALTERED OLDER PORPHYRY AND SERICITIZED OLDER PORPHYRY. SCHMITT AND RAYMOND MAP ANOMALOUS AREAS ON BASIS OF GEOCHEMICAL SAMPLING. BEYOND STOCK IS GENERAL TRIANGULAR AREA OF ALTERATIONEXTENDING FROM STOCK EAST TO JUPITER PEAK AND SW TO AZTEC MTN. PRINCIPAAL BI-SN ANOMALY LIES IN VALLECITO BASIN, ALONG WITH ANOMALOUS AG, CU, AS, AND SB. MO ANOMALY EXTENDS NORTH FROM MT EOLUS MINE AREA IN UPPER CHICAGO BASIN, SE THROUGH STOCK AND ALTERED AREA, THROUGH VALLECITO BASIN, AZTEC, BULLION, AND FLORIDA MTNS, LILLIE LAKE, AND ACROSS NORTH HALF OF EAST SILVER MESA. EAST-WEST BOUNDARIES ARE ZONE OF PRINCIPAL MINERALIZED RADIAL FRACTURES AND CONCENTRATION OF REGIONAL RECTANGULAR FRACTURES IN VALLECITO BASIN AND AT NORTH END OF EAST SILVER MESA, AND ESPECIALLY AT INTERSECTIONS OF TWO SYSTEMS. SECOND MO ANOMALY NOTED AROUND NORTH-TRENDING

Comment (Deposit): VEINS NORTH OF LOGTOWN AND EAST OF CRYSTAL VALLEY.

Comment (Workings): SURFACE SAMPLING SITES; 1000-FT-DEEP CORE HOLE

Comment (Deposit): CHICAGO BASIN STOCK IS COMPOSITE, HYPABYSSAL INTRUSIVE OF SILICIC TO INETERMEDIATE COMPOSITION INTRUDING WESTERN LOBE OF EOLUS GRANITE BATHOLITH. SUBCIRCULAR, OLDER OUTER PORTION IS GRANITE (OR QUARTZ) PORPHYRY INTENSELY ALTERED TO QUARTZ-SERICITE-KAOLINITE AND KAOLINITE-DICKITE-PYROPHYLLITE AND IS CHARACTERIZED BY DISSEMINATED PYRITE, WITH MO IN VEINLETS AND DISSEMINATED IN POCKETS OF ALTERATION MINERALS AND THROUGH GROUNDMASS OF PORPHYRITIC ROCKS. ELLIPTICAL, INNER YOUNGER INTRUSIVE PHASE (RHYOLITE PORPHYRY) IS LESS INTENSELY ALTERED. BOTH PORPHYRIES ARE CUT BY LATER MAFIC DIKES. GEOCHEMICAL SAMPLING SHOWED WESTERN SIDE OF OLDER BODY ANOMALOUS IN AS, SB, CU, BI, AU, PB, MO, AND SN. K2O AND NA2O DEPLETED DURING FELDSPAR REPLACEMENT BY SERICITE AND NEARLY ELIMINATED DURING SERICITE REPLACEMENT BY PYROPHYLLITE. GEOCHEMICAL SAMPLING OF YOUNGER BODY SHOWS WEAK SCATTERED ANOMALIES IN MO, AG, PB, AND ZN, WITH TWO SAMPLES DETECTING BI AND SN. OUTER MARGIN HAS SOMEWHAT HIGHER METAL CONTENT

Comment (Development): ANOMALOUS METALLIC AREA DRILLED IN 1960 BY AMAX. SURFACE GEOCHEMICAL SAMPLING BY USGS AND USBM IN MID 1960S FOR PRIMITIVE AREA RESOURCE APPRAISAL

Comment (Location): (LAND STATUS AND ADMINISTRATIVE AREA LOCATIONS CALCULATED USING GIS OVERLAY ANALYSIS FOR SAN JUAN N. F.). IN CHICAGO BASIN SE OF NEEDLE CREEK AND WNW OF COLUBMINE PASS. ELEV AND LAT-LONG GIVEN ARE FOR APPROX CENTER OF STOCK IN NW SW SEC. 35. ; INFO FROM LAND.ST :1974

References

Reference (Deposit): SCHMITT, L.J., AND RAYMOND, W.H., 1977, GEOLOGY AND MINERAL DEPOSITSOF THE NEEDLE MOUNTAINS DISTRICT, SOUTHWESTERN COLORADO: USGS BULL. 1434, 40 P.

Reference (Deposit): STEVEN, T.A., AND OTHERS, 1969, MINERAL RESOURCES OF THE SAN JUAN PRIMITIVE AREA. COLORADO: USGS BULL. 1261-F9

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