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Reef Ridge Prospect, McGrath District, Yukon-Koyukuk Borough, Alaska, USAi
Regional Level Types
Reef Ridge ProspectProspect
McGrath DistrictMining District
Yukon-Koyukuk BoroughBorough
AlaskaState
USACountry

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Latitude & Longitude (WGS84): 63° 23' 2'' North , 154° 21' 50'' West
Latitude & Longitude (decimal): 63.38389,-154.36389
GeoHash:G#: be60x6etu
Locality type:Prospect
Köppen climate type:Dfc : Subarctic climate


See also Soda Creek (MD056), Asmyrahha (MD080), Saddle (MD054), Atoll (MD053), Midway (MD046), Big Gate (MD050), Beaver (MD048), Hillside (MD049), and Bear Pass (MD044) Mississippi Valley Type prospects and occurrences in Medfra quadrangle. The Reef Ridge deposit is on land selected or conveyed to Doyon Ltd. For further information contact Doyon Ltd. at 210 1st Ave., Fairbanks, Alaska, 99701.
Location: The Reef Ridge prospect is located on a south-facing spur ridge north of the West Fork of Soda Creek, in the Medfra B-3 quadrangle in Section 26, T. 24 S., R. 23 E., of the Kateel River Meridian, at an elevation of 1840 feet (561 m). Location is precisely known; reporter visited property in 1993 and 1997.
Geology: Mineralization at the Reef Ridge deposit covers a surface area of about 700 feet (213 m) by 1,200 feet (366 m), and is hosted in the lower portion of the Whirlwind Creek Formation of Latest Silurian to Middle Devonian age (Dutro and Patton, 1982). As subdivided in the prospect area, the Whirlwind Creek Formation that hosts the metallic mineralization at Reef Ridge consists of vuggy dolomite, interbedded laminated Amphipora rich, algal limestone and lime mudstone, a distinctive carbonate conglomerate with black chert pebbles, and a fossiliferous carbonate reef complex. Clautice and others (1993) reported Pb-Pb analyses which are permissive for classification of the Reef Ridge prospect as a classic Mississippi Valley Type deposit. Two major zones have been identified. The eastern zone trends on surface N 20 E and is approximately 450 feet (137 m) long and 60 feet (18 m) wide. Mineralization consisting of secondary smithsonite, with minor flecks of galena and pyrite that have been introduced into tectonic breccias with a distinctive white dolomite gangue. The breccias are introduced along the high angle 'Prospect Fault' (Andrews and Rishel, 1982; Mosher, 1990). The west zone trends N 20 W and is approximately 700 feet (213 m) long and up to 160 feet (49 m) wide. At depth, the west zone deflects to a strike approximately parallel to the east zone decribed above. Mineralization in the west zone is characterized by hydrozincite hosted in strong solution breccias and accompanied by black hydrocarbon residues. Most of the zinc mineralization in the west zone is controlled by a high angle fracture; however, tectonic breccias are not as well developed in the west zone as they are in the east zone. Host lithology is inferred to be Devonian based on fossils at prospect. Age of mineralization is not known. From 1976 to 1982, WGM Inc., operator for Patino Ltd., completed about 2,000 feet (610 m) of diamond drilling and 1,700 feet (518 m) of trenching on the Reef Ridge property. One drill hole (#8) in the east zone intersected 38 feet (11.5 m) of 7.44 percent zinc, and 19 feet (5.8 m) grading 6.41 percent zinc. One drill hole (#1) in the west zone intersected 56 feet (17 m) grading 10.46 percent zinc. Schmidt (1997) indicates that one hole (not identified) intersected 154 feet (47 m) grading 20 percent zinc at Reef Ridge. Silver and lead values are not given although up to 1,000 ppm cadmium and 1,000 ppm lead were encountered in assay results. No silver values are given. Clautice and others (1993) report assay values of 2.00 percent zinc, and 2,000 ppm cadmium.
Workings: The Reef Ridge deposit was discovered by WGM Inc. and Patino Ltd. during exploration for base metals in the 1970s on lands selected by Doyon Ltd. (Andrews and Rishel, 1982). From 1976 to 1982, the exploration operator, WGM Inc., completed about 2,000 feet (610 m) of diamond drilling and 1,700 feet (518 m) of trenching on the Reef Ridge property. One drill hole (#8) in the east zone intersected 38 feet (11.5 m) of 7.44 percent zinc, and 19 feet (5.8 m) grading 6.41 percent zinc. One drill hole (#1) in the west zone intersected 56 feet (17 m) grading 10.46 percent zinc. Schmidt (1997) indicates that one hole (not identified) intersected 154 feet (47 m) grading 20 percent zinc at Reef Ridge. Silver and lead values are not given although up to 1,000 ppm cadmium and 1,000 ppm lead were encountered in assay results. No silver values are given. Clautice and others (1993) report assay values of 2.00 percent zinc, and 2,000 ppm cadmium.
Age: Host lithology is inferred to be Devonian based on fossils at prospect. Age of mineralization is not known.
Alteration: Groundwater has caused all primary metallic minerals to be nearly completely oxidized to secondary minerals; i.e. pyrite has altered to ferricrete; galena has altered to cerussite, and other secondary minerals.
Reserves: Based on the 1976-1982 subsurface and surface exploration work, an inferred reserve of 1,980,000 tons (1,800,000 tonnes) grading 6.5 percent zinc has been identified at the Reef Ridge deposit (Andrews and Rishel, 1982; Fair and Bright, 1989; Schmidt, 1997).

Commodities (Major) - Zn; (Minor) - Ag, Cd, Pb
Development Status: No
Deposit Model: Southeast Missouri lead-zinc (Cox and Singer, 1986; model no. 32a; Fisher and J

Regions containing this locality

North America PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


17 valid minerals.

Rock Types Recorded

Note: this is a very new system on mindat.org and data is currently VERY limited. Please bear with us while we work towards adding this information!

Select Rock List Type

Alphabetical List Tree Diagram

Detailed Mineral List:

Baryte
Formula: BaSO4
Calcite
Formula: CaCO3
Cerussite
Formula: PbCO3
Dolomite
Formula: CaMg(CO3)2
Galena
Formula: PbS
Goethite
Formula: α-Fe3+O(OH)
Gypsum
Formula: CaSO4 · 2H2O
Hematite
Formula: Fe2O3
Hydrozincite
Formula: Zn5(CO3)2(OH)6
Kaolinite
Formula: Al2(Si2O5)(OH)4
'Limonite'
Formula: (Fe,O,OH,H2O)
Marcasite
Formula: FeS2
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Muscovite var: Illite
Formula: K0.65Al2.0[Al0.65Si3.35O10](OH)2
Pyrite
Formula: FeS2
Quartz
Formula: SiO2
Sauconite
Formula: Na0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
Smithsonite
Formula: ZnCO3
Sphalerite
Formula: ZnS

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Galena2.CD.10PbS
Marcasite2.EB.10aFeS2
Pyrite2.EB.05aFeS2
Sphalerite2.CB.05aZnS
Group 4 - Oxides and Hydroxides
Goethite4.00.α-Fe3+O(OH)
Hematite4.CB.05Fe2O3
Quartz4.DA.05SiO2
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3
Cerussite5.AB.15PbCO3
Dolomite5.AB.10CaMg(CO3)2
Hydrozincite5.BA.15Zn5(CO3)2(OH)6
Smithsonite5.AB.05ZnCO3
Group 7 - Sulphates, Chromates, Molybdates and Tungstates
Baryte7.AD.35BaSO4
Gypsum7.CD.40CaSO4 · 2H2O
Group 9 - Silicates
Kaolinite9.ED.05Al2(Si2O5)(OH)4
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
var: Illite9.EC.15K0.65Al2.0[Al0.65Si3.35O10](OH)2
Sauconite9.EC.45Na0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
Unclassified Minerals, Rocks, etc.
'Limonite'-(Fe,O,OH,H2O)

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmXp, with m:p = 1:1
Galena2.8.1.1PbS
Sphalerite2.8.2.1ZnS
AmBnXp, with (m+n):p = 1:2
Marcasite2.12.2.1FeS2
Pyrite2.12.1.1FeS2
Group 4 - SIMPLE OXIDES
A2X3
Hematite4.3.1.2Fe2O3
Group 6 - HYDROXIDES AND OXIDES CONTAINING HYDROXYL
XO(OH)
Goethite6.1.1.2α-Fe3+O(OH)
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Cerussite14.1.3.4PbCO3
Smithsonite14.1.1.6ZnCO3
AB(XO3)2
Dolomite14.2.1.1CaMg(CO3)2
Group 16a - ANHYDROUS CARBONATES CONTAINING HYDROXYL OR HALOGEN
Hydrozincite16a.4.1.1Zn5(CO3)2(OH)6
Group 28 - ANHYDROUS ACID AND NORMAL SULFATES
AXO4
Baryte28.3.1.1BaSO4
Group 29 - HYDRATED ACID AND NORMAL SULFATES
AXO4·xH2O
Gypsum29.6.3.1CaSO4 · 2H2O
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Muscovite71.2.2a.1KAl2(AlSi3O10)(OH)2
var: Illite71.2.2d.2K0.65Al2.0[Al0.65Si3.35O10](OH)2
Sheets of 6-membered rings with 2:1 clays
Sauconite71.3.1b.3Na0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Unclassified Minerals, Mixtures, etc.
Kaolinite-Al2(Si2O5)(OH)4
'Limonite'-(Fe,O,OH,H2O)

List of minerals for each chemical element

HHydrogen
H HydrozinciteZn5(CO3)2(OH)6
H Limonite(Fe,O,OH,H2O)
H KaoliniteAl2(Si2O5)(OH)4
H MuscoviteKAl2(AlSi3O10)(OH)2
H Goethiteα-Fe3+O(OH)
H Muscovite (var: Illite)K0.65Al2.0[Al0.65Si3.35O10](OH)2
H SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
H GypsumCaSO4 · 2H2O
CCarbon
C CerussitePbCO3
C HydrozinciteZn5(CO3)2(OH)6
C SmithsoniteZnCO3
C DolomiteCaMg(CO3)2
C CalciteCaCO3
OOxygen
O CerussitePbCO3
O HydrozinciteZn5(CO3)2(OH)6
O SmithsoniteZnCO3
O Limonite(Fe,O,OH,H2O)
O DolomiteCaMg(CO3)2
O KaoliniteAl2(Si2O5)(OH)4
O MuscoviteKAl2(AlSi3O10)(OH)2
O HematiteFe2O3
O Goethiteα-Fe3+O(OH)
O Muscovite (var: Illite)K0.65Al2.0[Al0.65Si3.35O10](OH)2
O CalciteCaCO3
O SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
O BaryteBaSO4
O GypsumCaSO4 · 2H2O
O QuartzSiO2
NaSodium
Na SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
MgMagnesium
Mg DolomiteCaMg(CO3)2
AlAluminium
Al KaoliniteAl2(Si2O5)(OH)4
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al Muscovite (var: Illite)K0.65Al2.0[Al0.65Si3.35O10](OH)2
Al SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
SiSilicon
Si KaoliniteAl2(Si2O5)(OH)4
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si Muscovite (var: Illite)K0.65Al2.0[Al0.65Si3.35O10](OH)2
Si SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
Si QuartzSiO2
SSulfur
S GalenaPbS
S PyriteFeS2
S SphaleriteZnS
S MarcasiteFeS2
S BaryteBaSO4
S GypsumCaSO4 · 2H2O
KPotassium
K MuscoviteKAl2(AlSi3O10)(OH)2
K Muscovite (var: Illite)K0.65Al2.0[Al0.65Si3.35O10](OH)2
CaCalcium
Ca DolomiteCaMg(CO3)2
Ca CalciteCaCO3
Ca GypsumCaSO4 · 2H2O
FeIron
Fe PyriteFeS2
Fe Limonite(Fe,O,OH,H2O)
Fe MarcasiteFeS2
Fe HematiteFe2O3
Fe Goethiteα-Fe3+O(OH)
ZnZinc
Zn HydrozinciteZn5(CO3)2(OH)6
Zn SmithsoniteZnCO3
Zn SphaleriteZnS
Zn SauconiteNa0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O
BaBarium
Ba BaryteBaSO4
PbLead
Pb CerussitePbCO3
Pb GalenaPbS

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Devonian - Silurian
358.9 - 443.8 Ma



ID: 653785
Sedimentary; Carbonate

Age: Paleozoic (358.9 - 443.8 Ma)

Description: Interior western Alaska, Medfra-Kantishna region

Comments: Orogen, magmatic arc/suite; Wilson & Hults, unpublished compilation, 2007-08

Lithology: Limestone, dolostone, shale, evaporites, chalk; carbonate reefs or metamorphosed equivalent

Reference: J.C. Harrison, M.R. St-Onge, O.V. Petrov, S.I. Strelnikov, B.G. Lopatin, F.H. Wilson, S. Tella, D. Paul, T. Lynds, S.P. Shokalsky, C.K. Hults, S. Bergman, H.F. Jepsen, and A. Solli. Geological map of the Arctic. doi:10.4095/287868. Geological Survey of Canada Map 2159A. [2]

Ludlow - Late Devonian
423 - 382.7 Ma



ID: 1697944
Whirlwind Creek Formation and correlative units

Age: Pridoli (423 - 382.7 Ma)

Stratigraphic Name: Whirlwind Creek Formation

Description: Unit composed of a lower sequence of dolomite containing ostracodes of probable Late Silurian age, a middle sequence of mixed limestone and dolomite having favostid reefs and shelly fossils of probable Early Devonian age and an upper sequence of Amphipora-bearing dolomite and rugose coral bearing limestone

Lithology: Sedimentary

Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196. [21]

Early Paleozoic
443.8 - 541 Ma



ID: 3186448
Paleozoic sedimentary rocks

Age: Paleozoic (443.8 - 541 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Andrews, Tom, and Rishel, John, 1982, Annual Report for 1981, Reef Ridge I-to-XIII Project Areas, Kuskokwim Block, Alaska: Anchorage, Alaska, WGM Inc., Project Report 4, 45 p., 2 sheets, scales 1:63,360 and 1:20,000. (Report held by Doyon, Limited, Fairbanks, Alaska.) Clautice, K.H., Bowman, N.D., Clough, J.G., Gilbert, W.G., Kline, J.T., Smith, T.E., and Blodgett, R.B., 1993, Land selection Unit 8 (Kantishna River, Ruby, and Medfra quadrangles); References, lead isotope, geochemical and major oxide data: Alaska Division of Geological and Geophysical Surveys, 42 p., 1 sheet, scale 1:250,000. Dutro, J.T. Jr., and Patton,W.W. Jr., 1982, New Paleozoic formations in the northern Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, p. H13-H22. Fair, E.E., and Bright, T.D., 1989, Reef Ridge Project: Pasminco exploration report, Doyon, Limited Report 89-23, 32 p. (Report held by Doyon, Limited, Fairbanks, Alaska.) Fisher, D.G., and Juilliand, J.D., 1986, Mineral deposit types and their characteristics: U.S. Bureau of Land Management Technical Reference 3031-1, 153 p. Mosher, Greg, 1990, Reef Ridge Project: Pasminco Exploration Ltd., Doyon, Limited Report 92-72, 19 p. (Report held by Doyon, Limited, Fairbanks, Alaska) Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale. Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.
Santoro, L. (2015). The Jabali, Hakkari and Reef Ridge nonsulfide Zn (Pb) deposits: an evaluation by QEMSCAN® technology, and comparison to other analytical methods. PhD thesis, Università Degli Studi Di Napoli “Federico II”


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