|Quadrangle map, 1:250,000-scale||MG|
|Quadrangle map, 1:63,360-scale||A-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Mary Margaret prospect is located along a steep, southeast bank of Cheeneetnuk River, about 1.5 miles (2.4 km) southwest of the airstrip at White Mountain Mercury mine at an elevation of 1,450 feet (442 m) in the SE1/4 sec. 13, T. 24 N., R. 30 W., of the Seward Meridian. Some of the mineralized zone crops out on a ridge about 150 meters south of a conspicuous cold water spring entering the Cheeneetnuk River. The prospect is location 16, of Cobb (1972); the reporter visited the site in 1989 (Alaska Division of Geological and Geophysical Surveys station # 89BT118).|
The Mary Margaret prospect consists of cinnabar, quartz, carbonate and minor stibnite in brecciated limestone of the Early Devonian Cheeneetnuk limestone (Blodgett and Gilbert, 1983). The unit overlies the Dillinger subterrane, a lower Paleozoic continental margin assemblage (Bundtzen and others, 1997).
On the bluff south of the Cheeneetnuk River, two mineralized fracture orientations were measured: (1) a strike of N50E, with a dip of 70SE; and (2) a strike of N65E with a dip of 30SE. The fracture system can be traced for a strike length of about 20 meters before disappearing under vegetation. The cinnabar veinlets average about 5 cm thick and exhibit an exceptional bright red color similar to cinnabar at the Mountain Top Mine described by Miller and others (1989) in the Sleetmute quadrangle.At the creek level, a cold water sulfur spring that flows from fractured limestone in the area is depositing black, foul-smelling mud that contains Hg. Selected samples of ore contain from 2 to 13 percent mercury and up to 0.5 percent antimony, but with no precious metal values. The cinnabar to stibnite ratio averages about 10 to 1 (T.K. Bundtzen, written communication, 1989).
|Geologic map unit||(-154.87528417811, 62.1633537086889)|
|Mineral deposit model||Hot Springs mercury? (Cox and Singer, 1986; model 27a?).|
|Mineral deposit model number||27a?|
|Alteration of deposit||Oxidation of stibnite mineralization to stibiconite.|
|Workings or exploration||Only surface sampling has been conducted at the prospect. Selected samples contain from 2 to 13 percent mercury and up to 0.5 percent antimony, but no precious metals.|
|Indication of production||None|
Additional commentsThe Mary Margaret prospect formed near or in an unnamed strand of the Farewell-Denali fault system (Gilbert, 1981).
Blodgett, R.B., and Gilbert, W.G., 1983, The Cheeneetnuk Limestone, a new Early(?) to Middle Devonian formation in the McGrath A-4 and A-5 quadrangles, west-central Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 85, 6 p., 1 sheet, scale 1:63,360.
Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 p., 1 sheet, scale 1:125,000.
Cobb, E.H., 1972, Metallic mineral resources map of the McGrath quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-379, 1 sheet, 1:250,000 scale.
Gilbert, W.G., 1981, Preliminary geologic map and geochemical data, Cheeneetnuk River area, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File Report 153, 12 p., 2 sheets, 1:63,360 scale.
Maloney, R.P., 1967, Investigations of the White Mountain mercury deposit, Kuskokwim River basin, Alaska: U.S. Bureau of Mines Report of Investigations 6892, 94 p.
|Reporters||T.K. Bundtzen (Pacific Rim Geological Consulting)|
|Last report date||10/30/1998|