|Quadrangle map, 1:250,000-scale||SO|
|Quadrangle map, 1:63,360-scale||D-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is on the Pilgrim River just below the mouth of Iron Creek. It is cut into two parts, one north of the river and the other south. The coordinates are at the north part about 0.7 mile southeast of the center of section 12, T. 6 S., R. 30 W. The location is accurate.|
This locality has two parts, one on each side of the Pilgrim (Kruzgamepa) River, just downstream from the mouth of Iron Creek (SO127). They are separated by 1,000 feet of the Pilgrim River floodplain. The mineralization on the north side of the river consists of lenses of massive galena in marble near a contact with schist (Smith, 1908). One lens exposed over a distance of 3 feet in a prospect trench contain pyrite, finely crystalline galena, and minor sphalerite. A 2-foot sample across the highest-grade part contained 0.30 ounce of gold per ton, 2.3 ounces of silver per ton and 2.95 percent lead (Asher, 1969). Two samples reported by the owner contained 22.87 percent lead and 20.0 ounces of silver per ton and 14.2 percent lead and 14.5 ounces of silver per ton. The deposits on the south side of the river also include discontinuous lenses of massive galena. An 8- to 10-foot long, 6-foot wide,and 1.5-foot- thick lens of pyrite, fine galena, and limonite with siliceous marble, calcite, and quartz gangue was mined from a 25-foot-long adit and a few tons of ore were apparently shipped. Some boulangerite may also be present (Sainsbury and others, 1972). Pb-isotope analysis of one galena sample gave results identical to samples from the Red Dog (DL001) and Drenchwater Creek (DL002-004) deposits of the western Brooks Range (Church and others, 1985). The mineralization is preferentially developed in the marble but nearby quartz mica schist contains pyrite. The schist/marble contacts appear sheared (Cathcart, 1922). The massive galena is described as a replacement of the host marble (Smith, 1908).Till and others (2011) map the host rocks as part of the Devonian Nome Complex that consists of pelitic, calcareous, and graphitic schist. Slack and others (2011) reject a volcanogenic massive sulfide origin for the deposit. Their work on this and similar deposits in the Nome Complex indicates that the protolith of the metamorphic rocks that host the deposits are sedimentary and they see no evidence of volcanic rocks associated with them. They base their conclusion: 1) sulfur isotope analysis of the sulfides that indicate a marine origin for the sulfur, 2) isotopic analysis of the barite in some of the deposits that indicate the probable source of the sulfur is Devonian or Mississippi(?) sea water, and 3) whole-rock analyses of the host rocks of the mineralization that indicate that they were originally clastic sedimentary rocks. They propose a sedimentary-exhalative (SEDEX) origin for the deposit during Devonian rifting of the continental margin. Subsequently, the rocks in the area were subjected to blueschist facies metamorphism, then retrograded to greenschist-grade metamorphic rocks in the Jurassic and early Cretaceous.
|Geologic map unit||(-164.647031456811, 64.9767565290106)|
|Mineral deposit model||Sedimentary exhalative (SEDEX) lead-zinc-silver-fluorite deposit (Cox and Singer, 1986, model 31a).|
|Mineral deposit model number||31a|
|Age of mineralization||Deposited syngenetically in a marine environment during the Devonian; metamorphosed in the Jurassic or early Cretaceous.|
|Alteration of deposit||Oxidation to gossan with abundant limonite, and possible silicification.|
|Workings or exploration||An adit, prospect trenches, and a 2- foot-deep pit are present on the northwest side of the Pilgrim River. On the southeast side of the river, a 25-foot-long adit and numerous prospect pits explored the deposit. Some diamond drilling appears to have occurred in 1971 or 1972 (Sainsbury and others, 1972).|
|Indication of production||Yes; small|
|Production notes||A few tons of ore apparently were mined and shipped.|
Asher, R.R., 1969, Geology and geochemistry of part of the Iron Creek area, Solomon D-6 quadrangle, Seward Peninsula, Alaska: Alaska Division of Mines and Geology Geochemical Report 18, 19 p.
Cathcart, S.H., 1922, Metalliferous lodes in southern Seward Peninsula: U.S. Geological Survey Bulletin 722-F, p. 163-261.
Church, S.E., Briskey, J.A., Delevaux, M.H., and LeHuray, A.P., 1985, Preliminary results of Pb-isotope analyses of deposits from the Seward Peninsula, in Susan Barsch Winkler, ed., The United States Geological Survey in Alaska--Accomplishments during 1984: U.S. Geological Survey Circular 967, p. 24-27.
Cobb, E.H., 1972, Metallic mineral resources map of the Solomon quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-445, 1 sheet, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Solomon quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-181, 185 p.
Sainsbury, C.L., Hudson, T.L., Ewing, R., and Richards, T., 1972, Reconnaissance geologic map of the Solomon D-6 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-325, 17 p.
Slack, John, Till, A.B., Shanks, Wayne C., III, Ayuso, R.A., and Belkin, H.E., 2011, Stratabound Zn-Pb-Ag-Ba-F deposits and occurrences in the Nome Comples, Seward Peninsula: Characterisitics, origin, and exploration application: Alaks Miners Assocation, 2011 Annual Convention, Abstracts, p. 24-25 (and at http://www.alaskaminers.org/abstracts2011.pdf).
Smith, P.S., 1908, Investigations of mineral deposits of Seward Peninsula: U.S. Geological Survey Bulletin 345-E, p. 206-250.
Till, A.B., Dumoulin, J.A., Gamble, B. ., Kaufman, D.S., and Carroll, P.I., 1986, Preliminary geologic map and fossil data, Soloman, Bendeleben, and southern Kotzebue quadrangles, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 86-276, 10 p., 3 plates, scale 1:250,000.
Till, A.B., Dumoulin, J.A.,, Werdon, M.B., and Bleick, H.A., 2011, Bedrock geologic map of the Seward Peninsula, Alaska, and accompanying conodont data: U.S. Geological Scientific Investigations Map 3131, 31 p. pamphlet, 2 sheets, scale 1:500,000.
|Reporters||Travis L. Hudson (Applied Geology); D.J. Grybeck (Contractor, USGS)|
|Last report date||4/1/2012|