|Quadrangle map, 1:250,000-scale||SK|
|Quadrangle map, 1:63,360-scale||A-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is in Glacier Bay National Monument on the south side of the Margerie Glacier between elevations of 1,100 feet and 3,200 feet. It is about 2 miles from tidewater on the west side of Tarr Inlet in the NW1/4, section 16, T. 33 S., R. 50 E. of the Copper River Meridian. It is shown as location 7 in figure C-2 and in figure C-39 of Brew and others (1978); as location 1 by Cobb (1972; MF-424); and as location SE24 by Nokleberg and others (1987).|
Geologic descriptionThe following description is summarized from Brew and others (1978). The Margerie prospect is a porphyry copper deposit. Disseminated chalcopyrite, pyrite, pyrrhotite, and powellite-scheelite occur in a massive porphyritic, Tertiary quartz monzodiorite stock and associated dikes. The stock contains a porphyritic quartz monzonite core. A prominent joint set that trends N50E and dips steeply to the northwest cuts across the stock and extends into the surrounding Permian section of hornfelsed marine volcanic and sedimentary rocks. Porphyritic monzodiorite dikes up to 50 feet thick and quartz-sulfide veins up to 1.7 feet thick occupy the joint set. The dikes extend into the country rock but the veins do not. The veins, which are less important than disseminated mineralization, contain quartz, chalcopyrite, arsenopyrite, sphalerite, pyrite, pyrrhotite, powellite-scheelite, and molybdenite. Disseminated sulfide mineralization, primarily chalcopyrite, pyrite, pyrrhotite, and some powellite-scheelite, is largely confined to the stock and dikes. Where dikes extend into the surrounding marine sedimentary rocks, they contain much less disseminated sulfides. The joint system may have acted as the conduit for sulfide mineralization that replaced mafic minerals in the intrusive rocks. Plagioclase has been subjected to slight to moderate sericitization and K-spar alteration and biotite has been moderately chloritized. Limited investigation of the marine sedimentary rock section northeast of the stock did not reveal significant mineralization. However, the Permian marine volcanic and sedimentary rocks to the southwest of the stock contained various iron-stained zones, fault and fracture fillings of quartz and sulfides, and lenses of massive pyrite, pyrrhotite, and chalcopyrite. The Margerie prospect is within the Tarr Inlet suture zone, which forms the western boundary of the Geike province of Brew and others (1978). Based on the age of the host stock and dikes, the mineralization is Tertiary.
|Geologic map unit||(-137.09188636452, 59.0095922742434)|
|Mineral deposit model||Copper porphyry with associated veins, pods, and disseminations (Cox and Singer, 1986; model 17).|
|Mineral deposit model number||17|
|Age of mineralization||Tertiary (Brew and others, 1978).|
|Alteration of deposit||Plagioclase has been subjected to moderate sericitization and K-spar alteration, and biotite has been moderately chloritized (Brew and others, 1978).|
|Workings or exploration||Brew and others (1978) cite the following sequence of activity at the Margerie prospect. The prospect was discovered by Leo Mark Anthony in 1960 and 6 claims were staked that year. Investigations were made by E. M. MacKevett of the USGS in 1966, George Moerlein in 1968 and the U.S. Bureau of Mines in 1975 and 1976. A Masters thesis by M. A. Parke was in preparation in 1978.|
|Indication of production||None|
|Reserve estimates||As part of the mineral resources study of the Glacier Bay National Monument by Brew and others (1978), the U.S. Bureau of Mines estimated the deposit to contain 160 million tons of inferred resource that contain 0.2% copper, 0.008 ounces of gold per ton, 0.13 ounces of silver per ton, and 0.01% tungsten.|
Additional commentsThe deposit is within Glacier Bay National Park and Preserve where exploration and development is restricted.
|MRDS Number||A013114; D002752|
Anthony, L.M., 1977, unpublished maps and notes on investigations in Glacier Bay, 1958-1960: (Unpublished material available at the Juneau Mineral Information Center, U.S. Bureau of Land Management, Juneau, Alaska).
Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale 1:600,000.
Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p., 7 sheets.
Cobb, E.H., 1972, Metallic mineral resources map of the Skagway quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-424, 1 sheet, scale 1:250,000.
Cobb, E.H., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Skagway quadrangle, Alaska; Supplement to Open-File Report 78-316; Part A, Summaries of data to January 1, 1980: U.S. Geological Survey Open-File Report 81-82-A, 11 p.
MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1967, Mineral resources of Glacier Bay National Monument, Alaska: U. S. Geological Survey Open-File Report 67-151, 176 p.
MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.
Moerlein, G.A., 1968, Geology and drilling results, Nunatak molybdenum prospect, Walper property, southeastern Alaska: Unpublished report available at U.S. Bureau of Land Management Library at Juneau, Alaska.
Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.
|Reporters||T.C. Crafford (T. Crafford & Associates, Anchorage)|
|Last report date||2/4/2001|