General Information
Primary Commodities: iron, manganese, phosphorus
Deposit Type(s): Iron Formation
Location(s): 68.559720 N, -136.7825 W
NTS Mapsheet(s): 117A09
Location Comments: .5 Kilometres
Hand Samples Available at YGS: No
Capsule
Work History
Phosphate minerals were first identified in this area in 1962 by F.A. Campbell, who identified lazulite from specimens collected by B. Cameron from creek gravels at the junction of Blow River and Rapid Creek. Iron Formation was first noted on Rapid Creek, southwest of this point, by the Geological Survey of Canada in 1971, and was staked as Dawn and Mark cl (Y82551) in May/74 by Welcome North Mines Ltd and Bethlehem Copper, which performed sampling and evaluation later in the year.
The phosphate, iron and manganese-rich strata lie within a large area withdrawn from staking in Jul/78 pending creation of a National Wilderness Park, settlement of native land claims and development of a management plan for the Porcupine caribou herd.
Capsule Geology
Thick deposits of siderite and phosphatic ironstone in shale occur in the Rapid Creek Formation, which overlies a thick sequence of turbidite sandstones deposited during the late Early Cretaceous. The sequence consists of three units of cyclically interbedded siderite, mudstone and shale separated by two grey montmorillonite shale units. The phosphate minerals are thought to have been deposited by cold, northeast-flowing currents upwelling on the flank of a structural high which formed the eastern margin of the Blow Trough. In the Rapid Creek and Lower Big Fish River drainages, the Rapid Creek Formation forms an immense low-grade deposit that roughly contains reserves of 27,000,000,000 tonnes of ironstone with an average composition of 33% Fe2O3, 14% P2O5 and 5% MnO. The Rapid Creek iron-manganese horizon is ranked by Laznicka as the world's fourth largest manganese deposit, with 6.5% of the world's total manganese reserves.
The Rapid Creek Formation is the most northerly known phosphorite with a paleolatitude of 75° N. It varies from about 1000 m thick west of Rapid Creek to 60 m at Big Fish River. The phosphatic iron formation is composed of phosphate-siderite pellets and granules, detrital quartz and skeletal fragments in a matrix of sideritic mudstone. The phosphate-siderite pellets appear to have been redeposited and have an unusual chemistry which is more calcium deficient and more iron and magnesium rich than other marine phosphorites. Sampling in 1974 gave a grade of 16.7% total Fe across a thickness of 442 m. A direct reduction test gave 66.7% total Fe concentrate grade and a recovery of 72.5%.
The Blow River Formation is best known for the secondary minerals, chiefly phosphates, which are found as veins and breccia fillings in the Rapid Creek area. Thirty-two phosphate minerals have been identified, including ten new species. The best known is lazulite, Yukon's official gemstone. Robertson (1982) identified four phosphate mineral assemblages, each associated with a particular host rock type. Veins are most common in the more competent phosphorite beds, and are controlled by extensional cross fractures which accompanied Early Tertiary folding (Yeo, 1992). Primary fluid inclusions within the crystalline phosphate minerals give homogenization temperatures of 180-200°C.
Phosphate minerals were first identified in this area in 1962 by F.A. Campbell, who identified lazulite from specimens collected by B. Cameron from creek gravels at the junction of Blow River and Rapid Creek. Iron Formation was first noted on Rapid Creek, southwest of this point, by the Geological Survey of Canada in 1971, and was staked as Dawn and Mark cl (Y82551) in May/74 by Welcome North Mines Ltd and Bethlehem Copper, which performed sampling and evaluation later in the year.
The phosphate, iron and manganese-rich strata lie within a large area withdrawn from staking in Jul/78 pending creation of a National Wilderness Park, settlement of native land claims and development of a management plan for the Porcupine caribou herd.
Capsule Geology
Thick deposits of siderite and phosphatic ironstone in shale occur in the Rapid Creek Formation, which overlies a thick sequence of turbidite sandstones deposited during the late Early Cretaceous. The sequence consists of three units of cyclically interbedded siderite, mudstone and shale separated by two grey montmorillonite shale units. The phosphate minerals are thought to have been deposited by cold, northeast-flowing currents upwelling on the flank of a structural high which formed the eastern margin of the Blow Trough. In the Rapid Creek and Lower Big Fish River drainages, the Rapid Creek Formation forms an immense low-grade deposit that roughly contains reserves of 27,000,000,000 tonnes of ironstone with an average composition of 33% Fe2O3, 14% P2O5 and 5% MnO. The Rapid Creek iron-manganese horizon is ranked by Laznicka as the world's fourth largest manganese deposit, with 6.5% of the world's total manganese reserves.
The Rapid Creek Formation is the most northerly known phosphorite with a paleolatitude of 75° N. It varies from about 1000 m thick west of Rapid Creek to 60 m at Big Fish River. The phosphatic iron formation is composed of phosphate-siderite pellets and granules, detrital quartz and skeletal fragments in a matrix of sideritic mudstone. The phosphate-siderite pellets appear to have been redeposited and have an unusual chemistry which is more calcium deficient and more iron and magnesium rich than other marine phosphorites. Sampling in 1974 gave a grade of 16.7% total Fe across a thickness of 442 m. A direct reduction test gave 66.7% total Fe concentrate grade and a recovery of 72.5%.
The Blow River Formation is best known for the secondary minerals, chiefly phosphates, which are found as veins and breccia fillings in the Rapid Creek area. Thirty-two phosphate minerals have been identified, including ten new species. The best known is lazulite, Yukon's official gemstone. Robertson (1982) identified four phosphate mineral assemblages, each associated with a particular host rock type. Veins are most common in the more competent phosphorite beds, and are controlled by extensional cross fractures which accompanied Early Tertiary folding (Yeo, 1992). Primary fluid inclusions within the crystalline phosphate minerals give homogenization temperatures of 180-200°C.
Location Map
Last Updated: Nov 4, 2019
Work History
| Year | Work Type | Comment |
|---|---|---|
| 1974 | Geochemistry: Rock | |
| 1974 | Geology: Bedrock Mapping |
Regional Geology - Terrane
Group: Ancestral North America
Affinity: W Laurentia
Name: North America - basinal strata
Realm: Laurentia
Regional Geology - Bedrock
Supergroup:
Group/Suite:
Formation:
Member:
Terrane:
Period Max: Cretaceous
Age Max: 125 MA
Period Min: Cretaceous
Age Min: 100 MA
Rock Major: shale/sandstone/conglo
Rock Minor:
Reference: Norris (1981) - GSC Map 1516A
Geological Unit (1M): KS
Geological Unit (250K): KS4
Related References
| Number | Title | Page(s) | Document Type |
|---|---|---|---|
| YEG2012_10 | Preliminary observations on the geology and mineralogy of the Rapid Creek Formation, Blow River and Davidson Mountains map area (NTS 117A/8 and NTS 117A/9), Yukon | Annual Report Paper | |
| 1992GeolVol3_02 | Phosphorites, ironstones, and secondary phosphates in Mid-Cretaceous flysch of the blow trough, northern Yukon | Annual Report Paper | |
| YEG1979_80-pg115 | The geology of the Rapid Creek-Big Fish River phosphatic iron formation Northern Richardson Mountains, Yukon | Annual Report Paper |
| Citations |
|---|
| Coleman, L.C. and Robertson, B.T., 1981. Nahpoite Na2HPO4, a new mineral from the Big Fish River area, Yukon Territory. Canadian Mineralogist, vol. 19, p. 373-376. |
| Gordey, S.P., 1981. Assessment of mineral and fuel resource potential of the proposed northern Yukon national park and adjacent areas (Phase 1). Geological Survey of Canada, Open File 760. |
| Mandarino, J.A. and Sturman, B.D., 1976. Kulanite, a new barium iron aluminum phosphate from the Yukon Territory. Canadian Mineralogist, vol. 14, p. 127-131. |
| Mandarino, J.A., Sturman, B.D. and Corlett, M.I., 1977. Penikisite, the magnesium analogue of kulanite, from Yukon. Canadian Mineralogist, vol. 15, p. 393-395. |
| Mandarino, J.A., Sturman, B.D. and Corlett, M.I., 1978. Satterlyite, a new hydroxyl-bearing ferrous phosphate from the Big Fish River area, Yukon. Canadian Mineralogist, vol. 16, p. 411-413. |
| Norris, D.K. (ed), 1997. The geology, mineral and hydrocarbon potential of northern Yukon Territory and northwestern District of Mackenzie. Geological Survey of Canada, Bulletin 422. |
| Norris, D.K., 1980. Geology, northern Yukon Territory and northwestern District of Mackenzie. Geological Survey of Canada, Open File 715. |
| Robertson, B.T., 1980. Stratigraphic setting of some new and rare phosphatic minerals in the Yukon Territory. Unpublished MSc thesis, University of Saskatchewan. |
| Robertson, B.T., 1982. Occurrence of epigenetic phosphate minerals in a phosphatic iron-formation, Yukon Territory. Canadian Mineralogist, vol. 20, p. 177-187. |
| YOUNG, F.G. and ROBERTSON, B.T., 1984. The Rapid Creek Formation: An Albian Flysch-Related Phosphatic Iron Formation in Northern Yukon Territory. In: The Mesozoic of Middle North America, D.F. Stott and D.J. Glass, eds. Canadian Society of Petroleum Geologists Memoir 9, 1984, p. 361-372. |
| Young, F.G., 1972. Cretaceous stratigraphy between Blow and Fish rivers, Yukon Territory, In: Report of activities, part A: April to October, 1971. Geological Survey of Canada, Paper no. 72-1A, p. 229-235. |
