Unnamed Occurrence (ARDF - NM035; Thompson Creek), Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - NM035; Thompson Creek)	- not defined -
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: This tactite is on the west side of Grand Central River and north of Thompson Creek. A very general location was shown by Hummel (1961). This is locality 14 of Cobb (1972 [MF 463]; 1978 [OFR 78-93]); Cobb (1975 [MR-66]) also included this occurrence in his summary of Alaska tungsten deposits. The location is approximate but probably within about one half mile of the coordinates.
Geology: This tactite occurrence is in upper amphibolite facies metasedimentary rocks near the north contact of the Thompson Creek orthogneiss (Hummel, 1962 [MF 248]; Till, 1980). This is one of four similar occurrences (this occurrence, NM027, NM041, and NM044) identifed by Hummel (1961) in the central and southern Kigluaik Mountains. The calc-silicate (tactite) assemblages are interpreted to have been metamorphosed along with their country rocks. Scheelite is present in all four occurrences and galena and sphalerite accompany scheelite in one (NM044). Stream sediments in Thompson Creek contained as much as 150 ppm copper, 600 ppm zinc, 12 ppm molybdenum, and 50 ppm bismuth (Hummel and Chapman, 1960). Heavy mineral concentrates from Thompson Creek (NM036) contained scheelite (Hummel, 1962). The Thompson Creek orthogneiss has been determined to have a latest Proterozoic protolith (555 Ma, Amato and Wright, 1998). The upper amphibolite facies rocks, primarily north of the Thompson Creek orthogniess, are probably derived from Precambrian protoliths (Sainsbury, 1972; Bunker and others, 1979; Till and Dumoulin, 1994). They are thought to have undergone regional high-pressure metamorphism along with many other rocks of Seward Peninsula in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman, and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Patrick, 1988; Patrick and Evans, 1989; Armstrong and others, 1986; Hannula and McWilliams, 1995). Higher temperature metamorphism overprinted these rocks in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Throckmorton and Hummel, 1979; Till, 1983; Evans and Patrick, 1987; Leiberman, 1988; Patrick and Leiberman, 1988; 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). Uplift of the higher temperature metamorphic rocks took place in the mid- to Late Cretaceous and in the Eocene (Calvert, 1992; Dumitru and others, 1995).
Workings: No workings are known at this locality.
Age: Late Proterozoic (?); may be the same age as the Thompson Creek orthogneiss.
Alteration: Recrystallized calc-silicate rocks.

Commodities (Major) - W
Deposit Model: W skarn deposit (Cox and Singer, 1986; model 14a).

Other Databases

Link to USGS - Alaska:	NM035

Other Regions, Features and Areas containing this locality

References