Cochetopa District

Site Name

Primary: Cochetopa District
Secondary: Cochetopa Creek District
Secondary: Patented Claims: Lubricator, MS 2197
Secondary: Belle, MS 2341
Secondary: Maple Leaf, MS 4910
Secondary: Alaska, MS 7175
Secondary: Yukon, MS 7175
Secondary: Climax, MS 9547
Secondary: Sterling, MS 11174
Secondary: Standard, MS 11174 Clover Leaf, MS 13884
Secondary: Four Metals, MS 13884
Secondary: Monitor, MS 13884
Secondary: North of Ireland, MS 13884
Secondary: Wonder, MS 13884
Secondary: Great West, MS 13884
Secondary: Homestake, MS 13884
Secondary: Clover Leaf Placer, MS 13884
Secondary: Mayflower, MS 15265
Secondary: Little Boy, MS 15265
Secondary: Eastern Star, MS 16731
Secondary: Maple Leaf No. 2, MS 16738
Secondary: Eastern Star No. 3, MS 16852
Secondary: Eastern Star, MS 16852
Secondary: X-Ray, MS 17604
Secondary: Black Cat, MS 18249
Secondary: Protection, MS 18249
Secondary: Grand Aspen, MS 18249
Secondary: Equator, MS 18378
Secondary: Boston, MS 18378
Secondary: Mayflower, MS 18378

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Commodity

Primary: Gold
Primary: Silver
Primary: Copper
Secondary: Zinc
Secondary: Vanadium
Tertiary: Lead
Tertiary: Mercury
Tertiary: Tantalum
Tertiary: Tungsten
Tertiary: Uranium
Tertiary: Manganese

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Location

State: Colorado
County: Gunnison
District: Cochetopa (Cochetopa Creek) District

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Land Status

Land ownership: Private
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.

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Gunnison Mining Co. (Thornburg Mine)
Years: 1962 -

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Production

Not available

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Deposit

Record Type: District
Operation Category: Producer
Operation Type: Unknown
Year First Production: 1887
Year Last Production: 1962
Discovery Year: 1885
Discovery Method: Ore-Mineral In Place
Years of Production:
Organization:
Significant: N
Deposit Size: S

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Physiography

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

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Mineral Deposit Model

Not available

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Orebody

Not available

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Structure

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

Type: L
Description: Gunnison Gold Belt, Cochetopa Pluton, Gold Basin Stock, Cochetopa Park Caldera, Cochetopa Dome, Razor Creek Dome, Los Ochos Fault

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Alterations

Alteration Type: L
Alteration Text: Fe Oxidation; Chloritization In Quartz-Sulfide Veins; Sericitization; Kaolinitization Of Feldspar In Quartz Monzonite

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Rocks

Name: Quartz Monzonite
Role: Associated
Age Type: Associated Rock
Age Young: Neoproterozoic

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Analytical Data

Not available

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Materials

Ore: Uranophane
Ore: Zippeite
Ore: Pitchblende
Ore: Torbernite
Ore: Gold
Gangue: Barite
Gangue: Hematite
Gangue: Tantalite
Gangue: Fluorite
Gangue: Chlorite
Gangue: Sericite
Gangue: Malachite
Gangue: Marcasite
Gangue: Pyrrhotite
Gangue: Limonite
Gangue: Pyrite
Gangue: Quartz
Gangue: Epidote

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Comments

Comment (Deposit): DISTRICT UNDERLAIN BY PRECAMBRIAN COMPLEX OF METASEDIMENTARY ROCKS AND METABASALT, FELSITE, AND AMPHIBOLITE OF DUBOIS GREENSTONE AT EAST END OF GUNNISON GOLD BELT. STEEPLY DIPPING TO VERTICAL FOLIATIONS TREND GENERALLY NE AND ENE-WSW. METASEDIMENTS ARE CUT BY PRECAMBRIAN QUARTZ VEINS AND METARHYOLITE/APLITE DIKES, AND TO WEST (GREEN MOUNTAIN DISTRICT) BY PRECAMBRIAN GOLD BASIN QUARTZ DIORITE STOCK. FARTHER SOUTH ALONG COCHETOPA CREEK, METASEDIMENTARY SEQUENCE WAS INTRUDED BY COCHETOPA PLUTON (GRANITE OR QUARTZ MONZONITE) GENERALLY CONCORDANTLY WITH STRUCTURES IN METASEDIMENTS. ERODED PRECAMBRIAN SURFACE OF GUNNISON UPLIFT IS OVERLAIN BY JURASSIC AND CRETACEOUS SEDIMENTARY ROCKS. CAPPING SEQUENCE ARE THICK, OLIGOCENE, EARLY RHYODACITIC TO QUARTZ LATITIC FLOWS AND BRECCIAS, FOLLOWED BY COCHETOPA PARK TUFF AND CALDERA-FILL SEDIMENTS AND TUFFS. AFTER MAJOR ERUPTIONS, CALDERA COLLAPSED ALONG RING-FRACTURE ZONE IN INCOMPLETE CIRCULAR PATTERN. EAST-WEST-AND ENE-WSW-TRENDING FAULTS (INCLUDING

Comment (Deposit): LOS OCHOS) EXTEND NORTH OF NORTH PERIPHERY OF CALDERA. POST-COLLAPSE ERUPTIONS THROUGH CALDERA FILL FORMED COCHETOPA DOME. METALLIC MINERALIZATION VARIES GREATLY IN TYPE AND AGE. OLDER STYLE IS PRECAMBRIAN SYNGENETIC VOLCANOGENIC/FUMAROLIC MASSIVE SULFIDES IN METASEDIMENTS (SERICITE SCHIST) AND DUBOIS GREENSTONE AMPHIBOLITE. LATER PRECAMBRIAN AU-BEARING QUARTZ-CHLORITE VEINS CUT AMPHIBOLITE AND METASEDIMENTS AND MAY REPRESENT REMOBILIZED SULFIDES. QUARTZ VEINS AND METARHYOLITE/APLITE DIKES ARE SPATIALLY AND PROBABLY GENETICALLY RELATED TO GOLD BASIN STOCK THAT CONTROLLED SIMILAR MINERALIZATION IN GREEN MOUNTAIN DISTRICT JUST TO WEST. OTHER MINOR PRECAMBRIAN MINERALIZATION STYLE IS TA-BEARING PEGMATITE IN GRANODIORITE INTRUSION. HYPOGENE URANIUM MINERALIZATION IS ASSOCIATED WITH LOS OCHOS AND OTHER FRACTURES AND FAULTS ALONG AND NORTH OF NORTHERN RING-FRACTURE ZONE OF COLLAPSED COCHETOPA PARK CALDERA. HYDROTHERMAL SOLUTIONS CIRCULATING THROUGH THESE STRUCTURES CREATED DIFFERENT

Comment (Workings): BASE-AND PRECIOUS-METAL MINES DEVELOPED BY SHAFTS UP TO 300 FT DEEP AND ON AS MANY AS FOUR LEVELS. URANIUM DEPOSITS DEVELOPED BY SURFACE PROSPECT PITS AND TRENCHES. PRODUCTIVE U MINES DEVELOPED MAINLY BY TUNNEL, DECLINE, RAISES AND DRIFTS; LESS DEVELOPMENT BY SHAFTS UP TO 190 FT DEEP WITH DRIFTS, RAISES, AND WINZES.

Comment (Deposit): PROSPECTIVE PROPERTIES (OF GUNNISON CO.): COLORADO STATE PLANNING COMM. UNPUB. REPT., P. 6; (20) NELSON-MOORE, J.L., AND OTHERS, 1978, RADIOACTIVE MINERAL OCCURRENCES OF COLORADO AND BIBLIOGRAPHY: CGS BULL. 40, P. 388-396; (21) STEVEN, T.A., AND LIPMAN, P.W., 1976, CALDERAS OF THE SAN JUAN VOLCANIC FIRLD, SOUTHWESTERN COLORADO: USGS PROF. PAPER 958, P. 22-27; (22) TWETO, OGDEN, AND YATES, R.C., 1945, THE COCHETOPA QUICKSILVER DEPOSITS, SAGUACHE COUNTY, COLORADO: USGS LIMITED REPT., 3 P.; (23) VANDERWILT, J.W., 1947, MERCURY, IN MINERAL RESOURCES OF COLORADO: COLORADO STATE MINERAL RESOURCES BD,, P. 222. ; INFO.SRC : 1 PUB LIT; 2 UNPUB REPT

Comment (Deposit): Discovery Year: 1880S

Comment (Development): TO BE OF LOW GRADE. URANIUM BOOM OF LATE 1940S AND 1950S LED TO RENEWED EXPLORATION IN DISTRICT, WITH DISCOVERY OF URANIUM ON LOS OCHOS FAULT IN 1954 BY GUNNISON MINING CO. MAJOR MINE WAS THORNBURG (LOS OCHOS), WHICH PRODUCED ORE FROM 1954-1962. MINOR PRODUCERS INCLUDED LA RUE, SAGE HEN, AND KATHY JO. IN 1970S, INTEREST RENEWED IN GUNNISON GOLD BELT PRECIOUS-AND BASE-METAL DEPOSITS WITH REINTERPRETATION AS SYNGENETIC VOLCANOGENIC MASSIVE SULFIDES. MOST INTEREST DIRECTED IN DISTRICTS TO WEST; ANY ACTIVITY IN COCHETOPA DISTRICT IS UNKNOWN.

Comment (Commodity): URANOPILITE, ZIPPEITE, AND JOHANNITE ARE BELIEVED TO BE SECONDARY URANIUM MINERALS FORMED AFTER MINES WERE OPENED.

Comment (Location): DISTRICT IS EASTERNMOST IN GUNNISON GOLD BELT, ADJOINING GREEN MOUNTAIN DISTRICT ON EAST. DISTRICT COVERS SECTIONS CLOSELY BORDERING COCHETOPA CREEK FROM SITE OF SILLSVILLE IN GUNNISON COUNTY SOUTH (UPSTREAM) TO CONFLUENCE OF ALKALI CREEK IN SAGUACHE COUNTY, AND INCLUDING LOWER PORTIONS OF FOLLOWING NAMED DRAINAGES (NORTH TO SOUTH): COTTONWOOD GULCH, CAMP KETTLE GULCH, BEAD CREEK, MUDDY CREEK, POISON GULCH, ROCK CREEK,, AND ALKALI CREEK. PROMINENT LANDMARKS INCLUDE COCHETOPA CANYON, FLAT TOP, GREEN MOUNTAIN, RAZOR CREEK DOME, COCHETOPA DOME. MANY OTHER ADJACENT SECTIONS NOT LISTED ABOVE HAVE NUMEROUS URANIUM PROSPECTS. DISTRICT ACCESSIBLE VIA COLORADO RTE 114 UP COCHETOPA CREEK SOUTH FROM U.S. RTE 50 (CONFLUENCE OF COCHETOPA CREEK AND TOMICHI CREEK 8 MILES EAST OF GUNNISON); VIA COLORADO RTE 114 WNW FROM SAGUACHE OVER NORTH PASS; VIA ROAD UP RAZOR CREEK AND DOWN CAMP KETTLE GULCH SW FROM U.S. 50 AND DOYLEVILLE; VIA TRAILS EAST FROM COLORADO RTE 149 AND GOLD BASIN CREEK. DISTRICT

Comment (Location): EXTENDS ONTO HOUSTON GULCH (1962), RAZOR CREEK DOME (1962), AND SAWTOOTH MOUNTAIN (1962) QUADS. ELEV AND LAT-LONG GIVEN ARE FOR APPROX CENTER OF DISTRICT ON COCHETOPA CREEK AND COLORADO RTE 114 AT CONFLUENCE WITH UNNAMED GULCH BELOW (NORTH OF) LOS OCHOS MINE, IN C E2 NE SE SEC. 32, T48N, R2E. ; INFO FROM LAND.ST :1976

Comment (Development): EARLY HISTORY OF DISTRICT LARGELY UNKNOWN. DISCOVERIES AND EARLY MINING IN GUNNISON GOLD BELT LED TO ESTABLISHMENT OF SMALL MINING TOWNS OF DUBOIS, SPENCER, VULCAN, MIDWAY, CHANCE, AND PROBABLY SILLSVILLE IN LATE 1880S. POST-1900 RECORDS SHOW MAINLY INTERMITTENT PRODUCTION FROM SEVERAL LARGER MINES, SUCH AS HEADLIGHT, OLD LOT, ANACONDA (GOOSE CREEK DISTRICT), CONTINENTAL (BEAVER CREEK DISTRICT), LUCKY STRIKE AND LULA (GREEN MOUNTAIN DISTRICT), AND MAMOTH-GOOD HOPE (DOMINGO DISTRICT). ALASKA, YUKON, AND MAPLE LEAF MINES WERE PRINCIPAL PRODUCERS IN COCHETOPA DISTRICT. FIRST PATENTED CLAIMS (MAPLE LEAF AND LUBRICATOR) SURVEYED IN 1889-1890. REMAINING CLAIMS SURVEYED IN 1890 TO 1897 AND 1901 TO 1908. LAST REPORTED ACTIVITY WAS AT MAPLE LEAF MINE (1906-1913, 1931-1933) AND AT ALASKA-YUKON (INTERMITTENT THROUGH 1917, LATEST IN 1952). MERCURY OCCURRENCES PROSPECTED IN 1937; OCCURRENCES AT SMITH MINE AND ELISHA CLAIMS EXAMINED BY USBM IN 1942 UNDER STRATEGIC MINERALS ACT, BUT DEPOSITS PROVED

Comment (Deposit): ALTERATION SUITES DEPENDING ON ROCK TYPE, CHARACTERIZED BY (1) SERICITIZATION, CHLORITIZATION, AND KAOLINITIZATION IN PRECAMBRIAN BASEMENT ROCKS, AND (2) SILICIFICATION IN JURASSIC-CRETACEOUS SANDSTONES AND MUDSTONES. SILICIFIED SEDIMENTS WERE MORE FAVORABLE MINERALIZING ENVIRONMENT FOR URANIUM VEIN DEPOSITS, ESPECIALLY AFTER RENEWED FAULT MOVEMENT AND INTENSE BRECCIATION.

Comment (Geology): STEVEN AND LIPMAN'S (1976) GENERALIZED EVOLUTION OF COCHETOPA PARK CALDERA: (1) WIDESPREAD, EARLY INTERMEDIATE-COMPOSITION (RHYODACITIC TO QUARTZ LATITIC) FLOWS AND BRECCIAS; (2) ERUPTION OF COCHETOPA PARK ASH-FLOW TUFF, EXTENDING SW AND INTERFINGERING WITH VOLCANICS IN SAN LUIS CALDERA AND FOLLOWING THE NEARLY FILLED MOAT AROUND NORTH SIDE OF LA GARITA CALDERA; (3) (UNLIKE OTHER LARGE SAN JUAN CALDERAS, MAJOR ERUPTIONS CEASED BEFORE ONSET OF COLLAPSE); (4) INCOMPLETE COLLAPSE OF CALDERA, SUBSIDING BY DOWNWARD BENDING AND EEASTWARD TILTING ALONG HINGELINE ON SW MARGIN AND BY 2300 TO 2600 FT OF DOWNWARD DISPLACEMENT ALONG POSTULATED RING-FRACTURE ZONE; (5) AFTER OR CONCURRENT WITH SUBSIDENCE, CALDERA WALLS SLUMPED INWARD ALONG ARCUATE FAULTS, WITH SPLINTERING IN BREAKAWAY ZONE ON WEST SIDE NEAR HINGELINE; (6) MINOR POST-SUBSIDENCE PYROCLASTIC ERIPTIONS FILLED CALDERA (A) EAST OF MEDIAL RIDGE WITH WELDED ASH-FLOW TUFF AND THICK NONWELDED PUMICEOUS ASH-FLOW TUFF AND (B) NW OF MEDIAL

Comment (Geology): RIDGE WITH SANDY TUFFACEOUS STREAM SEDIMENTS, PARTIALLY COVERING ARCUATE FAULTS OF OUTER SLUMPED ZONE; (7) ERUPTION OF THICK RHYOLITE FLOW WITH BASAL VITROPHURE THROUGH CALDERA FILL ON TREND WITH MEDIAL RIDGE (ERODED FEATURES OF WHICH FORM COCHETOPA DOME); (8) LATE TERTIARY AND QUATERNARY DISSECTION OF CALDERA AND HOT-SPRING TRAVERTINE DEPOSITION AT SPRINGS ON CALDERA FAULTS.

Comment (Deposit): BLM CLAIM RECORDS ASSIGN DISTRICT NAME OF "COCHETOPA" BUT AREA HAS ALSO BEEN KNOWN BY ALTERNATE DISTRICT NAME OF "COCHETOPA CREEK." UNDIVIDUAL RECORDS PREPARED FOR (1) PRINCIPAL PRECIOUS-AND BASE-METAL MINES (MASSIVE SULFIDE AND VEIN DEPOSITS): ALASKA, BLACK CAT, HATHAWAY, LUBRICATOR, MAPLE LEAF, AND YUKON; '2) PRINCIPAL URANIUM MINES AND CLAIMS; ANNA, D EPENDABLE GROUP AND SNOWSHOE CLAIM, ELISHA, KATHY JO AND IRISHMAN'S DREAM, LA RUE, M AND W, MERCURY (SMITH), RIDGWAY NO. 3. SAGE HEN, (TUNGSTEN), AND THORNBURG (LOS OCHOS); (3) MISCELLANEOUS PROPERTIES (PEGMATITE): TANTALITE PROSPECT, COCHETOPA PROSPECT (TUNGSTEN). ADDITIONAL REFERENCES: (11) AEC PRELIMINARY EWCON. REPTS. PRR-C-1535, PRR-C-1536, PRR-C-1616, P-3-1712, P-3-1714, P-3-1715; (12) BEATY, D., AND ZAHONEY, S., 1977, GEOLOGY OF THE YUKON-ALASKA MINE AREA, COCHETOPA MINING DISTRICT, SAGUACHE COUNTY, COLORADO: UNPUB. REPT.; (13) BECKMAN, R.T., AND KERNS, W.H., 1965, MERCURY POTENTIAL OF THE UNITED STATES: USBM IC-8252, P.

Comment (Deposit): 370-372; (14) DROBECK, P.A., 1979, GEOLOGY AND TRACE ELEMENT GEOCHEMISTRY OF A PART OF THE GUNNISON GOLD BELT, COLORADO: COLORADO SCHOOL OF MINES M.SC. THESIS T-2251, P. 48-63; (15) DROBECK, P.A., 1981, PROTEROZOIC SYNGENETIC MASSIVE SULFIDE DEPOSITS IN THE GUNNISON GOLD BELT, COLORADO, IN EPIS, R.C., AND CALLENDER, J.F., EDS., WESTERN SLOPE COLORADO: NEW MEXICO GEOL. SOC. 32D FIELD CONF. GUIDEBOOK, P. 279-286; (16) HANLEY, J.B., AND OTHERS, 1950, PEGMATITE INVESTIGATIONS IN COLORADO, WYOMING, AND UTAH 1942-1944: USGS PROF. PAPER 227, PL. 1; (17) HILL, J.M., 1909 NOTES ON THE ECONOMIC GEOLOGY OF SOUTHEASTERN GUNNISON COUNTY, COLORADO: USGS BULL. 380, P. 37-38; (18) HUTCHINSON, R.M., 1981, STRUCTURE AND PETROLOGY OF COCHETOPA PLUTON AND ITS METAMORPHIC WALLROCKS, SAGUACHE COUNTY, COLORADO, IN EPIS, R.C., AND CALLENDER, J.F., ED., WESTERN SLOPE COLORADO: NEW MEXICO GEOL. SOC. 32D FIELD CONF. GUIDEBOOK, P. 297-304; (19) NELSON, A.P., (NO DATE), MINING DISTRICTS, PRODUCING MINES AND

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References

Reference (Deposit): WRIGJT. R.J., AND EVERHART, D.L., 1960, URANIUM--COCHETOPA DISTRICT, IN DEL RIO, S.M., MINERAL RESOURCES OF COLORADO, FIRST SEQUEL: COLORADO STATE MINERAL RESOYRCES BD., P. 353-357.

Reference (Deposit): COLORADO DIV. MINES ONF. REPTS. AND ANNUAL OPERATOR REPTS.

Reference (Deposit): BLM MINERAL SURVEYS

Reference (Deposit): OLSON, J.C., AND STEVEN, T.A., 1976, GEOLOGIC MAP OF THE SAWTOOTH MOUNTAIN QUADRANGLE, SAGUACHE COUNTY, COLORADO: USGS MAP MF-733.

Reference (Deposit): OLSON, J.C., 1976, GEOLOGIC MAP OF THE IRIS QUADRANGLE, GUNNISON AND SAGUACHE COUNTIES, COLORADO: USGS MAP GQ-1286.

Reference (Deposit): OLSON, J.C., 1976, GEOLOGIC MAP OF THE HOUSTON GULCH QUADRANGLE, GUNNISON AND SAGUACHE COUNTIES, COLORADO: USGS MAP GQ-1287.

Reference (Deposit): OLSON, J.C., AND STEVEN, T.S., 1976, GEOLOGIC MAP OF THE RAZOR CREEK DOME QUADRANGLE, SAGUACHE COUNTY, COLORADO: USGS MAP MF-748.

Reference (Deposit): SHERIDAN, D.M., AND OTHERS, 1981, PRECAMBRIAN SULFIDE DEPOSITS IN THE GUNNISON REGION, COLORADO, IN EPIS, R.C., AND CALLENDER, J.F., EDS., WESTERN SLOPE COLORADO: NEW MEXICO GEOL. SOC. 32D FIELD CONF. GUIDEBOOK, P. 273-277.

Reference (Deposit): HEDLUND, D.., AND OLSON, J.C., 1981, PRECAMBRIAN GEOLOGY ALONG PARTS OF THE GUNNISON UPLIFT OF SOUTHWESTERN COLORADO, IN EPIS, R.C., AND CALLENDER, J.F., EDS., WESTERN SLOPE COLORADO: NEW MEXICO GEOL. SOC. 32D FIELD CONF. GUIDEBOOK, P. 267-272.

Reference (Deposit): MALAN, R.C., AND RANSPOT, H.W., 1959, GEOLOGY OF THE URANIUM DEPOSITS IN THE COCHETOPA MINING DISTRICT, SAGUACHE AND GUNNISON COUBTIES, COLORADO: ECON. GEOLOGY, A. 54, NO. 1, P. 1-19.

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