Iron Mask Prospect, Seward District, Kenai Peninsula Borough, Alaska, USA
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Location: The prospect is on the east shore of Resurrection Bay, opposite Renard Island (Fox Island) in the NW1/4 of section 21, T. 3 S., R. 1 E., of the Seward Meridian. A small adit has been driven above the high tide level in a brecciated metamorphosed basalt. The breccia as exposed is 12 feet thick and has been traced 100 feet or more along the shore. This is prospect number 78 of Martin and others (1915, p. 235) and location 108 of Tysdal (1978). This location is accurate to within a quarter of a mile.
Geology: The host rock is a Lower Cretaceous diabase (Tysdal and Case, 1979) that has been brecciated and recemented by quartz and sulfide mineralization. The breccia is composed of fine-grained, diabase fragments which range in size from less than a fourth of an inch to several inches in size. The matrix material is a greenish cement. The original breccia is probably a flow breccia mixed with tuffaceous material that has been slightly broken and rehealed with quartz, and pyrite with a little calcite and chalcopyrite (Martin and others, 1915). The breccia is about 12 feet wide at this location and an sample across this zone showed 1.1% copper (Grant and Higgins, 1909, p. 104-105).
Workings: A small adit above the high tide line assayed 1.1% copper (Grant and Higgins, 1909, p. 104-105).
Age: Probably Upper Cretaceous; massive sulfide.
Alteration: Silicification.
Reserves: None report.
Commodities (Major) - Cu, Zn
Development Status: No
Deposit Model: Cyprus massive sulfide (Cox and Singer, 1986; model 24a).
Mineral List
5 entries listed. 5 valid minerals.
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References
Cobb, E.H., 1972, Metalic mineral resources map of the Blying Sound quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-440, 1 sheet, scale 1:150,000. Cobb, E.H., and Tysdal, R.G., 1980, Summaries of data on and list of references to metallic and selected nonmetallic mineral deposits in the Blying Sound and Seward quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-621, 276 p. Grant, U.S., and Higgins, D.F., Jr., 1909, Notes on geology and mineral prospects in the vicinity of Seward, Kenai Peninsula: U.S. Geological Survey Bulletin 379-C, p. 98-107. MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000. Martin G.C., Johnson, B.L., and Grant, U.S., 1915, Geology and mineral resources of Kenai Peninsula, Alaska: U.S. Geological Survey Bulletin 587, 243 p. Tysdal, R.G., 1978, Mines, prospects, and occurrences map of the Seward and Blying Sound quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-880-A, 2 sheets, scale 1:250,000. Tysdal, R.G., and Case, J.E., 1979, Geologic map of the Seward and Blying Sound quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-1150, 12 p, 1 sheet, scale 1:250,000.