|Quadrangle map, 1:250,000-scale||TN|
|Quadrangle map, 1:63,360-scale||B-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Avnet prospect is at an elevation of about 2,850 feet on a ridge separating the Rock and Granite creeks drainages, 4 miles southwest of Baldry Mountain. It is in the northeast quarter of section 14, T. 5 N., R. 14 W., of the Fairbanks Meridian. The location is accurate within several hundred feet. The site corresponds to location 7 of Cobb (1972), and roughly to the site for Avnet, U.S. Bureau of Land Management MAS number 0020480009.|
The country rocks at the Avnet manganese prospect include Paleozoic limestone, slate, chert, and greenstone that grade into calcareous schist, quartz-mica schist, and quartzite (Thomas, 1965). The prospect is at or near a northeast-trending thrust fault in the chert unit (Reifenstuhl and others, 1997 [RI 97-15a]).
This poorly exposed deposit reportedly was discovered in 1952 by Paul Bittner (Thomas, 1965). Frost-heaved rock chips at the surface presumably represent rock directly beneath. The rubble reportedly is light colored, weakly calcareous quartzite, schist, and phyllite. Development work consists of a trench 40 feet long, 3-feet wide, and 2 feet deep, two caved pits, and some surface scrapings (Thomas, 1965).
The ore mineral at the Avnet prospect is psilomelane (manganese oxide), which occurs as small, frost-heaved fragments in a zone 3,000 feet long and 600 feet wide at the crest and on the northwest side of a ridge. The psilomelane is in the quartzite, where it forms small, irregular masses up to 3 inches in largest dimension, and in vein quartz, where it forms lattices of thin seams. It also coats some of the rubble. Thomas (1965) speculated that the psilomelane is hydrothermal in origin. Minor pyrolusite occurs with the psilomelane (Foley, 1992).Thomas (1965) collected 32 samples of frost-heaved material in 1964. They assayed 0.64 to 34.4 percent manganese, with an an average value of 15.78 percent. Silver values ranged from below the limit of detection to 0.28 ounce per ton. The samples were assayed for gold but all were below the detection limit. Liss and others (1997) collected a sample (96KC096) of manganese-rich quartz veins in tan, sugary quartzite rubble near a prospect pit. It contained more than 20,000 parts per million (ppm) manganese, and 499 ppm gallium, 195 ppm copper, 220 ppm zinc, and 10.2 ppm cadmium Values of other elements were not anomalous.
|Geologic map unit||(-150.372557925493, 65.2605405379352)|
|Mineral deposit model||Epithermal Mn (Cox and Singer, 1986; model 25g) or Volcanogenic Mn (Cox and Singer, 1986; model 24c).|
|Mineral deposit model number||24c or 25g|
|Age of mineralization||The mineralization presumably is younger than the Ordovician age assigned to many of the local rocks in the area (Chapman and others, 1982).|
|Workings or exploration||Workings consisted of one trench and two pits, since caved (Thomas, 1965).|
|Indication of production||None|
Chapman, R.M., Yeend, W.E., Brosge, W.P., and Reiser, H.N., 1982, Reconnaissance geologic map of the Tanana quadrangle: U.S. Geological Survey Open-File Report 82-734, 20 p., scale 1:250,000.
Cobb, E.H., 1972, Metallic mineral resources map of the Tanana quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-371, 1 sheet, scale 1:250,000.
Cobb, E.H., 1977, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Tanana quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-432, 98 p.
Foley, J.Y., 1992, Ophiolite and other ultramafic metallogenic provinces in Alaska (west of the 141th meridian): U.S. Geological Survey Open-File Report 92-20-B, 55 p.
Liss, S.A., Reifenstuhl, R.R., Clautice, K.H., Bundtzen, T.K., Newberry, R.J., Dover, J.H., and Blodgett, R.B., 1997, Rock geochemistry from the Rampart mining district: Alaska Division of Geological & Geophysical Surveys Public Data File 97-29G, 19 p., 1 DVD.
Reifenstuhl, R.R., Dover, J.H., Pinney, D.S., Newberry, R.J., Clautice, K.H., Liss, S.A., Blodgett, R.B., Bundtzen, T.K., and Weber, F.R., 1997, Geologic map of the Tanana B-1 Quadrangle, central Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 97-15A, 17 p., 1 sheet, scale 1:63,360.
|Reporters||G.E. Graham (ADGGS), D.J. Szumigala (ADGGS)|
|Last report date||7/21/2003|