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Decatur South District

Past Producer in Conejos county in Colorado, United States with commodity Gold
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Controls for ore emplacement
  14. Economic information about the deposit and operations
  15. Mining district
  16. Land status
  17. Links to other databases
  18. Bibliographic references
  19. General comments
  20. Reporter information

Geologic information

Identification information

Deposit ID 10014025
MRDS ID D010634
Record type District
Current site name Decatur South District
Alternate or previous names Gilmore District
Related records 10287982

Geographic coordinates

Geographic coordinates: -106.58949, 37.35835 (WGS84)
Elevation 3414
Relative position 3.1 MILES N 63 TO 83 W FROM PLATORO

Site location context

Political divisions (FIPS codes)

Conejos(county)

Colorado(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Platoro(quadrangle 1:24,000 scale)

Antonito(quadrangle 1:100,000 scale)

Durango(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Alamosa-Trinchera(hydrologic unit)

Rio Grande Headwaters(hydrologic accounting unit)

Rio Grande Headwaters(hydrologic subregion)

Rio Grande(hydrologic region)

Federal lands

Rio Grande National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State County
United States Colorado Conejos

Public Land Survey System information

Meridian Township Range Section Fraction State
New Mexico 036N 004E 07,08,17,18 Colorado

Comments on the location information

  • CLAIMS EXTEND DISCONTINUOUSLY FROM ALAMOSA RIVER UP NORTH SLOPE OF KLONDIKE MOUNTAIN AND INTO SADDLE BETWEEN KLONDIKE MOUNTAIN AND UNNAMED HILL 0.7 MILE TO WEST AND DUE NORTH OF HILMAN LAKE. DISTRICT ACCESSIBLE BY STOCK DRIVEWAY SW FROM STUNNER PASS NW OF PLATORO OR BY TRAILS UP ALAMOSA RIVER FROM STUNNER. ELEV AND LAT-LONG GIVEN ARE FOR PROSPECT ON BRYAN, SIXTEEN TO ONE, AND OPHIR CLAIMS IN APPROX NE SEC. 18 (UNSURVEYED SECTION). ; INFO FROM LAND.ST :1975

Commodities

Commodity Importance
Gold Primary

Comments on the commodity information

  • OCCURRENCE OF PETZITE UNCERTAIN BUT BASED ON POSSIBLE SIMILARITY WITH UTE (PLATORO) DISTRICT

Materials information

Materials Type of material
Gold Ore
Petzite Ore
Pyrite Ore
Quartz Gangue

Alteration

  • (Local) See Comments

Mineral occurrence model information

Model code 154
USGS model code 25e
Deposit model name Epithermal quartz-alunite Au
Mark3 model number 38

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Monzonite
    Rock unit name Intrusive Rocks--Monzonite (Alamosa River Stock);Summitville Andesite
    Rock description Intrusive Rocks--Monzonite (Alamosa River Stock);Summitville Andesite
    Stratigraphic age (youngest) Oligocene
    Stratigraphic age (youngest) Oligocene
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite
  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Monzonite
    Rock unit name Intrusive Rocks--Monzonite (Alamosa River Stock);Summitville Andesite
    Rock description Intrusive Rocks--Monzonite (Alamosa River Stock);Summitville Andesite
  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite

Nearby scientific data

(1) -106.58949, 37.35835
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure description San Juan Volcanic Field
Type of structure Local
Structure description Platoro Caldera, Summitville Caldera, Alamosa River Stock, Platoro Fault Zone

Controls for ore emplacement

  • Quartz Veins In Post-Intrusion Extensional Faulting Near Platoro Fault Zone

Comments on the geologic information

  • ANDESITE; (7) PROLONGED INTERMEDIATE-SILICIC POSTCOLLAPSE VOLCANISM (OLIGOCENE-MIOCENE) AROUND CALDERA MARGINS--(A) ALAMOSA RIVER MONZONITE STOCK (29.1 MY), (B) RHYODACITE OF PARK CREEK (27.8-26.7 MY), (C) GREEN RIDGE VOLCANICS (27.8-27.4 MY), (D) UPPER RHYODACITE OF PARK CREEK (LT 26.5 MY), (E) QUARTZ LATITE PORPHYRY DIKES (25.8 MY), (F) QUARTZ LATITE OF SOUTH MTN (22.8 MY), (G) RHYOLITE OF CROPSY MTN (20.2 MY); (8) ALAMOSA RIVER STOCK AND JASPER STOCK INTRUDED ALONG SOUTH AND EAST SUMMITVILLE CALDERA RING FRACTURES, CRATER CREEK STOCK PERIPHERAL ON WEST, CAT CREEK STOCK REMOTE TO EAST; (9) NW-TRENDING CALDERA-RELATED STRUCTURES RENEWED BY INFERRED GENERAL RESURGENCE OF COMPOSITE BATHOLITH BENEATH ENTIRE SE SAN JUAN CALDERA CLUSTER, MANIFESTED BY RIO GRANDE FAULT ZONE (GRABEN), PASS CREEK-ELWOOD CREEK FAULT ZONE, PLATORO FAULT ZONE, SUMMITVILLE FAULT; (10) N-TRENDING LATE CENOZOIC EXTENSIONAL BLOCK FAULTING RELATED TO GENERAL EASTWARD TILTING OF VOLCANIC FIELD TOWARD DEVELOPING RIO
  • GRANDE DEPRESSION IN SAN LUIS VALLEY.
  • GENERAL EVOLUTION OF PLATOOR-SUMMITVILLE CALDRERA (LIPMAN, 1975); () WIDESPREAD ANDESITIC-RHYODACITIC VOLCANISM AND VOLCANICLASTIC DEPOSITION FROM CLUSTER OF 6 TO 7 OLIGOCENE STRATOVOLCANOES; (2) ERUPTION OF LA JARA CANYON MBR OF TREASURE MTN TUFF QUARTZ LATITE (30-29 MY), INITIAL COLLAPSE OF PLATORO CALDERA, PONDING OF LATE LA JARA CANYON ASH FLOWS; (3) INITIAL ASYMMETRICAL RESURGENCE BOUNDED ON SE BY CALIFORNIA GULCH ARCUATE FAULT AND ON SW BY PLATORO FAULT ZONE HINGE LINE; (4) MOAT FILLING BY FISHER GULCH RHYODACITE AND LOWER SUMMITVILLE ANDESITE (29.8-29.1 MY) AND ASSOCIATED LAKE-DELTAIC SEDIMENTS; (5) ERUPTION OF OJITO CREEK MBR OF TREASURE MTN TUFF BEFORE MOAT FILLING COMPLETE, FOLLOWED BY INFERRED INITIAL COLLAPSE OF SUMMITVILLE CALDERA, BOUNDED ON SE BY CORNWALL FAULT RING FRACTURE TRUNCATING PLATORO RESURGENT BLOCK; (6) ERUPTION OF RA JADERO MBR OF TREASURE MTN TUFF FOLLOWED BY SECOND COLLAPSE OF SUMMITVILLE CALDERA, WITH RENEWED MOVEMENT AFTER ERUPTION OF UPPER SUMMITVILLE

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic
Deposit size Small
Significant No
Discovery year 1912
Discoverer George Gilmore

Mining district

District name Decatur South (Gilmore) District

Land status

Ownership category Private

Comments on the workings information

  • MINES PROSPECTS DEVELOPED BY OPEN CUTS AND TUNNELS. BELOW OPEN CUT WHERE ORE FIRST WORKED, UPPER TUNNEL DRIVEN 15 FT BELOW CUT, WITH TWO SMALL WINZES. SECOND TUNNEL DRIVEN 70 FT BELOW CUT.

Comments on development

  • GEORGE GILMORE DISCOVERED AU TELLURIDE ON OLD CLAIMS ON KLONDIKE MTN LATE IN 1912. PUBLICITY ABOUT DISCOVERY DURING FOLLOWING WINTER CAUSED RUCH OF PROSPECTORS TO AREA NEXT YEAR WITH HOPES OF DEVELOPING SECOND CRIPPLE CREEK. TOWNSITE OF GILMORE LAID OUT NEAR SITE OF LITTLE GEORGE PLACER IN MEADOW AREA ALONG ALAMOSA RIVER AT NORTH BASE OF KLONDIKE MTN. EARLY IN 1913, TOWN CONSISTED OF TENT AND TWO SHACKS FUNCTIONING AS HOTEL, STORE, AND PHOTOGRAPHER'S STUDIO. LACK OF EXTENSIVE DEVELOPMENT MAY HAVE BEEN DUE TO DISCONTINUITY OF ORE VEIN WHERE FIRST WORKED AND OBSCURING EFFECT OF LANDSLIDES AND SURFICIAL MATERIALS.

Reference information

Bibliographic references

  • Deposit

    PATTON, H.B., 1917, GEOLOGY AND ORE DEPOSITS OF THE PLATORO-SUMMITVILLE MINING DISTRICT, COLORADO: CGS BULL. 13.

  • Deposit

    LIPMAN, P.W., 1974, GEOLOGIC MAP OF THE PLATORO CALDERA AREA, SOUTHEASTERN SAN JUAN MOUNTAINS, SOUTHWESTERN COLORADO: USGS MAP I-828.

  • Deposit

    LIPMAN, P.W., 1975, EVOLUTION OF THE PLATORO CALDERA COMPLEX AND RELATED VOLCANIC ROCKS, SOUTHEASTERN SAN JUAN MOUNTAINS, COLORADO: USGS PROF. PAPER 852.

  • Deposit

    STEVEN, T.A., AND LIPMAN, P.W., 1976, CALDERAS OF THE SAN JUAN VOLCANIC FIELD, SOUTHWESTERN COLORADO: USGS PROF. PAPER 958.

  • Deposit

    BIRD, W.H., 1972, MINERAL DEPOSITS OF THE SOUTHERN PORTION OF THE PLATORO CALDERA COMPLEX, SOUTHEAST SAN JUAN MOUNTAINS, COLORADO: MTN. GEOLOGIST, V. 9, NO. 4, P. 379-387.

  • Deposit

    LIPMAN, P.W., AND STEVEN, T.A., 1970, RECONNAISSANCE GEOLOGY AND ECONOMIC SIGNIFICANCE OF THE PLATORO CALDERA, SOUTHEASTERN SAN JUAN MOUNTAINS, COLORADO: USGS PROF. PAPER 700-C, P. C19-C29.

  • Deposit

    GOW, T.T., AND YANG, W.T., 1914, SURVEY NORTHWEST OF GILMORE, CONEJOS COUNTY, COLORADO: COLORADO SCHOOL OF MINES THESIS T-465.

  • Deposit

    CALKIN, W.S., 1967, GEOLOGY, ALTERATION, AND MINERALIZATION OF THE ALUM CREEK AREA, SAN JUAN VOLCANIC FIELD, COLORADO: COLORADO SCHOOL OF MINES THESIS T-1113.

General comments

Subject category Comment text
Deposit GILMORE IS SOUTHERNMOST OF THREE DISTRICTS KNOWN BY POPULAR NAMES OF JASPER, STUNNER, AND GILMORE; HOWEVER, BLM CLAIM RECORDS ASSIGN DISTRICT NAME OF "DECATUR" TO ALL THREE AREAS. DUE TO DIFFERENCES IN GEOLOGY AND MINERALIZATION, DISTRICT REPORTS ARE SEPARATED AND ASSIGNED NAMES OF DECATUR NE (JASPER), DECATUR SOUTH (GILMORE), AND DECATUR WEST (STUNNER). NO INDIVIDUAL RECORDS PREPARED FOR GILMORE DISTRICT BECAUSE ONLY KNOWN PRODUCING PROPERTY NOT PRECISELY LOCATED AND MINE'S GEOLOGY AND MINERALIZATION COINCIDENT WITH THOSE OF DISTRICT. FOR OTHER DISTRICTS WITHIN PLATORO-SUMMITVILLE CALDERA COMPLEX, SEE RECORDS FOR SUMMIT (SUMMITVILLE), UTE (PLATORO), DECATUR WEST (STUNNER), DECATUR NE (JASPER), AND CRATER DISTRICTS. ; INFO.SRC : 1 PUB LIT; 2 UNPUB REPT
Deposit AU MINERALIZATION (NATIVE AU AND POSSIBLY IN DISSEMINATED PYRITE) LOCALIZED IN DISCONTINUOUS QUARTZ VEINS FILLING FRACTURES OR FISSURES IN (1) LOWER SUMMITVILLE ANDESITE MOAT FILL ON SW MARGIN OF PLATORO CALDERA AND IN (2) POST-SUMMITVILLE CALDERA COLLAPSE ALAMOSA RIVER MONZONITE STOCK INTRUDED ALONG SUMMITVILLE CALDERA RING FRACTURE. CLUSTER OF SUBPARALLEL VEINS IN MONZONITE TREND GENERALLY N 30 TO 35 E; PRINCIPAL VEIN IN ANDESITE TRENDS N 3 TO 5 E (LIPMAN, 1974). FROM CLUSTER OF VEINS IN MONZONITE, INFERRED FAULT ZONE DIVERGES SOUTHWARD INTO SMALL HORST. ILL-DEFINED PERIPHERAL STRUCTURAL ZONE WEST OF AND SUBPARALLEL TO PLATORO FAULT ZONE IS PROBABLY RELATED TO POST-STOCK EXTENSIONAL FAULTING.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUN-83 Schwochow, Stephen D. Colorado Geological Survey
Editor 16-NOV-11 Wilson, Anna B U.S. Geological Survey Changed record type from site to district.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Colorado resources

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