Unnamed (near upper Martha Creek)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Ag; Bi; Pb; Sb; Sn; W
Other commodities B; Be; Mo
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-3
Latitude 64.9253
Longitude -166.0391
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.

Geologic setting

Geologic description

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?

Production and reserves

Workings or exploration The occurrence is a surface exposure of sulfide-bearing rock.
Indication of production None

References

MRDS Number 10307905

References

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.
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., 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.
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