|Quadrangle map, 1:250,000-scale||IL|
|Quadrangle map, 1:63,360-scale||D-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The approximate location of these two small occurrences is in upper Marsh Creek at an elevation of about 1,000 feet. It is about 0.5 mile south of the boundary of Lake Clark National Park and about 1.25 miles west of Chinitna Bay. The site is in the approximate center of E1/2 NE1/4 sec. 7, T. 4 S., R. 23 W., Seward Meridian. The location is accurate within about 0.5 mile, and is taken from Detterman and Hartsock (1966). The Marsh Creek occurrences are included in location 10 of Detterman and Cobb (1972), but the site apparently is mislocated on their map.|
There are two closely-spaced mineral deposits in upper Marsh Creek: a copper occurrence and an iron occurrence (Detterman and Hartsock, 1966). The copper occurrence is a 6- to 12- inch-[long?] vein of chalcopyrite and oxidized copper minerals in Triassic(?) marble. Weak azurite-malachite stain extends outward 20 to 30 feet to either side of the vein. The iron occurrence consists of a small concentration of magnetite in possibly Lower Jurassic Talkeetna Formation metasedimentary and volcanic rocks in a fault block that also contains Jurassic granitic rocks (Detterman and Hartsock, 1966). The copper vein apparently is high grade but Detterman and Hartsock did not sample it because of its small size.The marble host of the copper deposit may correlate with the Bruin Limestone Member of the Upper Triassic Kamishak Formation (Detterman and Reed, 1980). The Bruin Limestone is massive to thin-bedded, light- to dark-gray limestone, interbedded with banded green and white chert. The Talkeetna Formation(?) host of the magnetite deposit generally consists of andesite flows, agglomerate, tuff, volcanic breccia, and minor sedimentary rocks.
|Geologic map unit||(-153.292380972684, 59.8436622627499)|
|Mineral deposit model||The copper deposit is possibly a polymetallic vein; the magnetite deposit is probably Fe skarn (Cox and Singer, 1986, models 22c and 18d).|
|Mineral deposit model number||22c, 18d|
|Age of mineralization||The copper deposit is Triassic or younger; the magnetite deposit is probably Jurassic.|
|Workings or exploration||The occurrences were found during regional geologic mapping; the copper vein apparently is high grade, but it was not sampled because of its small size (Detterman and Hartsock, 1966).|
|Indication of production||None|
Detterman, R.L., and Cobb, E.H., 1972, Metallic mineral resources map of the Iliamna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-364, 1 sheet, scale 1:250,000.
Detterman, R.L., and Hartsock, J.K., 1966, Geology of the Iniskin-Tuxedni region, Alaska: U.S. Geological Survey Professional Paper 512, 78 p.
Detterman, R. L., and Reed, B. L., 1964, Preliminary map of the geology of the Iliamna quadrangle, Alaska: U. S. Geological Survey Miscellaneous Geological Investigations Map I-407, 1 sheet, scale 1:250,000.
|Reporters||C.C. Hawley, Hawley Resource Group, Anchorage, Alaska|
|Last report date||6/3/2003|