|Quadrangle map, 1:250,000-scale||NM|
|Quadrangle map, 1:63,360-scale||D-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The occurrence is in the headwaters of Martha Creek, a south tributary to Tisuk River. It is on the west side of a divide between Martha Creek and Tisuk River at an elevation of 1,650 feet. It is about 0.4 mile north of saddle 1570 and located to within about 1,000 feet.|
Sulfide-bearing rocks occur on a northwest-striking fault ,which cuts quartz-graphite-biotite gneiss, at the contact of the gneiss with a gneissic marble layer. The occurrence is about 2.4 miles upstream from weakly mineralized quartz-breccia zones exposed along lower Martha Creek (NM005) and 2 miles northwest of the fluorite pipe in 'Fluorite Creek' (a local name assigned by Sainsbury, Smith, and Kachadoorian, 1970; NM010). The occurrences are generally in an area of small tourmalinated granite plugs of Cretaceous age.
At this locality, Smith (in Sainsbury, Smith, and Kachadoorian, 1972) collected a sulfide-bearing rock sample (67Ats118) that contained 30 ppm silver, 15,000 ppm boron, 5,000 ppm bismuth, 7 ppm beryllium, 70 ppm molybdenum, 10,000 ppm lead, 1,500 ppm antimony, 300 ppm tin and 500 ppm tungsten. The presence of elevated boron values suggests that the rocks are tourmalinated.The area is underlain by amphibolite facies graphitic metasedimentary rocks that are locally gneissic. Sainsbury, Smith and Kachadoorian (1972) mapped granite stocks and felsic dikes in the Martha Creek drainage including several that are tourmalinated. The amphibolite facies metasedimentary rocks are now considered to have a late Proterozoic or early Paleozoic protolith (Till and Dumoulin, 1994; Hannula and others, 1995), perhaps correlative with parts of the Nome Group. Like the Nome Group, these rocks probably underwent regional blueschist facies metamorphism in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Armstrong and others, 1986; Hannula and McWilliams, 1995). The blueschist facies rocks were recrystallized to greenschist facies or higher metamorphic grades in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Miller and Hudson, 1991; Miller and others, 1992; Dumitru and others, 1995; Hannula and others, 1995; Hudson and Arth, 1983; Hudson, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998).
|Geologic map unit||(-166.041741726088, 64.9245307071487)|
|Mineral deposit model||Polymetallic, sulfide-bearing vein in amphibolite facies metasedimentary rocks.|
|Age of mineralization||Cretaceous; post mid-Cretaceous amphibolite facies metamorphism and possibly the same age as mineralized Cretaceous granitic rocks in the area.|
|Alteration of deposit||Tourmalinization?|
|Workings or exploration||The occurrence is a surface exposure of sulfide-bearing rock.|
|Indication of production||None|
Amato, J.M., and Wright, J.E., 1997, Potassic mafic magmatism in the Kigluaik gneiss dome, northern Alaska--A geochemical study of arc magmatism in an extensional tectonic setting: Journal of Geophysical Research, v. B102, no. 4, p. 8065-8084.
Amato, J.M., and Wright, J.E., 1998, Geochronologic investigations of magmatism and metamorphism within the Kigluaik Mountains gneiss dome, Seward Peninsula, Alaska, in Clough, J.G., and Larson, Frank, eds., Short Notes on Alaskan Geology 1997: Alaska Division of Geological and Geophysical Surveys Professional Report 118a, p. 1-21.
Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and southern Brooks Range, Alaska, in Evans, B.W., and Brown, E.H., eds., Blueschists and eclogites: Geological Society of America Memoir 164, p. 184-203.
Dumitru, T.A., Miller, E.L., O'Sullivan, P.B., Amato, J.M., Hannula, K.A., Calvert, A.T., and Gans, P.B., 1995, Cretaceous to Recent extension in the Bering Strait region, Alaska: Tectonics, v. 14, p. 549-563.
Forbes, R.B., Evans, B.W., and Thurston, S.P., 1984, Regional progressive high-pressure metamorphism, Seward Peninsula, Alaska: Journal of Metamorphic Geology, v. 2, p. 43-54.
Hannula, K.A., and McWilliams, M.O., 1995, Reconsideration of the age of blueschist facies metamorphism on the Seward Peninusla, Alaska, based on phengite 40Ar/39Ar results: Journal of Metamorphic Geology, v. 13, p. 125-139.
Hannula, K.A., Miller, E.L., Dumitru, T.A., Lee, Jeffrey, and Rubin, C.M., 1995, Structural and metamorphic relations in the southwest Seward Peninsula, Alaska; Crustal extension and the unroofing of blueschists: Geological Society of America Bulletin, v. 107, p. 536-553.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
Miller, E.L., and Hudson, T.L., 1991, Mid-Cretaceous extensional fragmentation of a Jurassic-Early Cretaceous compressional orogen, Alaska: Tectonics, v. 10, p. 781-796.
Miller, E.L., Calvert, A.T., and Little, T.A., 1992, Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.
Sainsbury, C.L., Coleman, R.G., and Kachadoorian, Reuben, 1970, Blueschist and related greenschist faces rocks of the Seward Peninsula, Alaska, in Geological Survey research 1970: U.S. Geological Survey Professional Paper 700-B, p. B33-B42.
Sainsbury, C.L., Smith, T.E., and Kachadoorian, Reuben, 1972, Reconnaissance geologic map of the Nome D-3 quadrangle, Alaska: U.S. Geological Survey Open-File Report 72-327, 14 p., 1 sheet, scale 1:63,360.
Thurston, S.P., 1985, Structure, petrology, and metamorphic history of the Nome Group blueschist terrane, Salmon Lake area, Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 96, p. 600-617.
Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
|Reporters||C.C. Hawley and Travis L. Hudson|
|Last report date||10/22/1999|