| Main commodities | Mn |
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| Quadrangle map, 1:250,000-scale | CL |
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| Quadrangle map, 1:63,360-scale | C-1 |
| Latitude | 68.5097 |
| Longitude | -150.3917 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | The occurrence is in bluffs and outcrops on the west side of Cobblestone Creek at an elevation of about 2300 feet. It is about 15.7 kilometers south of Arc Mountain near the northwest corner of section 12, T. 11 S., R. 7 E. |
Geologic descriptionShale and silty mudstone of the Lower Cretaceous Torok Formation are exposed along Cobblestone Creek in bluffs and outcrops just west of the creek. Greenish-brown mudstone and shale locally display intense manganese staining (Kurtak and others, 1995). Four samples across a zone 6.5 meters thick contained 2.4 to 11.7 percent manganese. Another sample across a zone 4.5 meters wide contained 5.5 percent manganese. A sample examined by the U.S. Bureau of Mines contained 61.9 percent iron, 15.2 percent silica, 7.4 percent aluminum, 5.8 percent calcium, 4.8 percent manganese, and 4.0 percent phosphorus (Barnwell and others, 1989). The main mineral in the sample is siderite; no specific manganese mineral was identified. Similar manganese-stained rocks occur along a northeast-trending zone about 2.3 kilometers long. | |
| Geologic map unit | (-150.394505583656, 68.5093003923806) |
|---|---|
| Mineral deposit model | Sedimentary manganese. |
| Age of mineralization | Early Cretaceous host rock. |
| Workings or exploration | Only sampling by government agencies. |
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| Indication of production | None |
Additional commentsMAS No. 0020220011. | |
| MRDS Number | A106064 |
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References | |
| Reporters | K.D. Kelley (U.S. Geological Survey); D.J. Grybeck (Contractor, U.S. Geological Survey) |
| Last report date | 4/18/2010 |