Unnamed Occurrence (ARDF - NM027; Grand Central River), Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - NM027; Grand Central River)	- not defined -
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: This tactite occurrence is at an elevation of about 1,500 feet on a steep southwest-facing slope on the east side of the Grand Central River valley. It is close to the section line between sections 16 and 17, T. 6 S., R. 32 W., Kateel River Meridian. This is locality 35 of Hummel (1962, MF 248) and locality 15 of Cobb (1972 [MF 463]; 1978 [OFR 78-93]). The occurrence is probably located to within about 1,000 feet of the coordinates.
Geology: This is one of four tactite occurrences (this occurrence, NM035, 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). These occurrences are in amphibolite and upper amphibolite facies metasedimentary rocks adjacent or nearby the Thompson Creek orthogneiss (Hummel, 1962 [MF 248]; Till, 1980). The Thompson Creek orthogneiss has been determined to have a latest Proterozoic protolith (Amato and Wright, 1998). The upper amphibolite facies rocks, primarily north of the Thompson Creek orthogneiss, 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 or exploration activities are known at this locality.
Age: Late Proterozoic (?); may be the same age as the Thompson Creek orthogneiss.
Alteration: Recrystallized calc-silicate assemblages are expected.

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

Other Databases

Link to USGS - Alaska:	NM027

Other Regions, Features and Areas containing this locality

References