Unnamed Occurrence (ARDF - NM006; near upper Martha Creek), Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - NM006; near upper Martha Creek)	- not defined -
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: 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.
Geology: 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 tourmalinized 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 tourmalinized. 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 toumalinized. 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).
Workings: The occurrence is a surface exposure of sulfide-bearing rock.
Age: Cretaceous; post mid-Cretaceous amphibolite facies metamorphism and possibly the same age as mineralized Cretaceous granitic rocks in the area.
Alteration: Tourmalinization?

Commodities (Major) - Ag, Bi, Pb, Sb, Sn, W ; (Minor) - B, Be, Mo
Development Status: None
Deposit Model: Polymetallic, sulfide-bearing vein in amphibolite facies metasedimentary rocks.

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Link to USGS - Alaska:	NM006

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References