|Quadrangle map, 1:250,000-scale||LC|
|Quadrangle map, 1:63,360-scale||C-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The location appears to include the whole of Ptarmigan Creek. Individual prospects not delineated. Location plotted as approximate midpoint of Ptarmigan Creek. Location could extend up to 13 km both upstream and downstream.|
Geologic descriptionBrooks (1913) reported encouraging placer gold results from benches along Ptarmingan Creek. Ptarmigan Creek drains a diverse group of rocks: sedimentary rocks (unit KJs), volcanic rocks (unit Tv), plutonic rocks (unit TKi6), and the Chilikadrotna Greenstone. The Chilikadrotna Greenstone is a Late Silurian unit of weakly metamorphosed basalt, andesite, chert, limestone, and tuffaceous sedimentary rocks. Fossils from a limestone lens in the Chilikadrotna Greenstone suggest an early Late Silurian age (Bundtzen and others, 1979). Nelson and others (1983) described the unit KJs as interbedded lithic graywacke, silty sandstone, black shale , and local conglomerate. Irregular quartz segregations and veinlets are locally present. Small diorite bodies (unit TKi6) intrude these sedimentary rocks. One diorite pluton yielded a potassium-argon age on hornblende of 69.4 +/- 2.1 m.y. (Eakins and others, 1978) Adjacent to some of the larger igneous bodies are narrow contact aureoles of pelitic hornfels. Unit Tv includes: rhyolitic breccia, ash-flow tuff, flows, and intrusive rocks and subordinate mafic to intermediate flows. Potassium-argon ages for unit Tv range from 56.2 to 62.7 m.y. indicating a Tertiary age for these rocks (Eakins and others, 1978).
|Geologic map unit||(-154.702249719638, 60.5993238838221)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||The placer gold is Quaternary, the source of gold could come from a variety of rocks with diverse ages.|
|Alteration of deposit||Not applicable|
|Workings or exploration||Unknown|
|Indication of production||Undetermined|
|Reserve estimates||No reserves|
|Production notes||No production|
Additional commentsCobb (1976) indicates that the location of the creek is not given, and because no other mention of the creek occurs, the report is suspect.
Brooks, A.H., 1913, Mineral resources of Alaska, report on progress of investigations in 1912: U.S. Geological Survey Bulletin 542, 308 p.
Bundtzen, T.K., Gilbert, W.G., and Blodgett, R.B., 1979, The Chilikadrotna Greenstone, an Upper Silurian metavolcanic sequence in the central Lake Clark quadrangle, Alaska, in Short notes on Alaskan geology, 1978: Alaska Division of Geological and Geophysical Surveys Geological Report 63, p. 31-35.
Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-485, 101 p.
Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part A, Summaries to January 1, 1981: U.S. Geological Survey Open-File Report 81-1343-A, 25 p.
Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part B, Lists of references to Januray 1, 1981: U.S. Geological Survey Open-File Report 81-1343-B, 20 p.
|Reporters||D.P. Bickerstaff (USGS)|
|Last report date||6/15/1998|