Decatur South District

Site Name

Primary: Decatur South District
Secondary: Gilmore District
Secondary: Patented Claims: Little George Placer, MS 12307
Secondary: Bryan, MS 12308
Secondary: Sixteen To One, MS 12308
Secondary: Ophir, MS 12308
Secondary: Roe, MS 16470
Secondary: Boyd, MS 16470
Secondary: Helen, MS 16470
Secondary: Nellie Nelson, MS 16470
Secondary: Unpatented Claims: Gilmore
Secondary: Peterson

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Commodity

Primary: Gold

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Location

State: Colorado
County: Conejos
District: Decatur South (Gilmore) 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

Not available

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Production

Not available

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Deposit

Record Type: District
Operation Category: Past Producer
Operation Type: Unknown
Discovery Year: 1912
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

Model Name: Epithermal quartz-alunite Au

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Orebody

Not available

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Structure

Type: R
Description: San Juan Volcanic Field

Type: L
Description: Platoro Caldera, Summitville Caldera, Alamosa River Stock, Platoro Fault Zone

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Alterations

Alteration Type: L
Alteration Text: See Comments

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Rocks

Name: Monzonite
Role: Associated
Age Type: Associated Rock
Age Young: Oligocene

Name: Monzonite
Role: Associated
Age Type: Host Rock
Age Young: Oligocene

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Petzite
Ore: Pyrite
Gangue: Quartz

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Comments

Comment (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.

Comment (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.

Comment (Geology): 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

Comment (Location): 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

Comment (Commodity): OCCURRENCE OF PETZITE UNCERTAIN BUT BASED ON POSSIBLE SIMILARITY WITH UTE (PLATORO) DISTRICT

Comment (Geology): GRANDE DEPRESSION IN SAN LUIS VALLEY.

Comment (Workings): 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.

Comment (Geology): 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

Comment (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

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References

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

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

Reference (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.

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

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

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

Reference (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.

Reference (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.

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