Unnamed (on Martha Creek)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Bi; Cu; Pb
Ore minerals limonite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-3
Latitude 64.9574
Longitude -166.0706
Nearby scientific data Find additional scientific data near this location
Location and accuracy Occurrences of sulfidized rock were reported by Sainsbury, Smith, and Kachadoorian (1972) about 1.5 miles south of the confluence of Martha Creek with Tisuk River. The best occurrences were reported to be on the west side of Martha Creek. The occurrences are approximately located but probably within about a quarter of a mile of the coordinates.

Geologic setting

Geologic description

Several oxidized (limonitic?) quartz-breccia zones, as much as 100 feet across, occur in this area, especially on the west side of Martha Creek (Sainsbury, Smith, and Kachadoorian, 1972). Anomalous amounts of bismuth, copper, and lead were reported.
The area is underlain by amphibolite facies graphitic metasedimentary rocks that are locally gneissic in character. Sainsbury, Smith, and Kachadoorian (1972) mapped granite stocks and felsic dikes in the Martha Creek drainage and a small tourmalinized granite about three-quarters of a mile west of these occurrences. The tourmalinized granite is at the head of a creek that parallels Martha Creek and also flows north to Tisuk River. 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 (-166.073243927609, 64.9566306291224)
Mineral deposit model Quartz breccia in amphibolite facies metasedimentary rocks.
Age of mineralization Cretaceous, probably related to nearby or buried tourmalinized granites.
Alteration of deposit Oxidation and silicification.

Production and reserves

Workings or exploration No workings were reported; occurrences were found by Sainsbury and his coauthors Smith, and Kachadoorian (1972) during reconnaissance in 1970.
Indication of production None


MRDS Number 10307904


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