Unnamed Occurrence (ARDF - NM010; near 'Fluorite Creek'), Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - NM010; near 'Fluorite Creek')	- not defined -
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: Fluorite Creek was a local name assigned by Sainsbury, Kachadoorian, and Smith (1970) to an upper tributary to Tisuk River in the NW1/4 section 4, T. 7 S., R. 36 W., Kateel River Meridian. The occurrence is at an elevation of about 1,800 feet and located within about 1,000 feet of the coordinates.
Geology: Fluorite was found in two breccia pipes at this locality (Sainsbury, Kachadoorian, and Smith, 1970). The easternmost pipe is 40 to 60 percent fluorite and 20 feet wide; it consists of a central core of crystalline fluorite surrounded by a margin of banded silica and fluorite with pyrite. Locally this breccia is silicified, pyritized, and cemented by fluorite. The central fluorite-rich core is cut by iron-stained veinlets 0.25 to 0.5 inch thick. The second pipe, located 350 feet west of the first, is smaller and more pyritized and contains a higher percentage of silicified breccia. A large fault, spatially associated with the pipes, is marked by a 30- to 40-foot-wide jasperoid containing a few percent fluorite. A sample of the pyrite-bearing jasperoid breccia contained 3 ppm silver and 70 ppm molybdenum; no gold was detected. The wall rock along normal faults in the general area are mineralized with pyrrhotite, pyrite, and traces of other sulfides. Mid-Cretaceous granite stocks and felsic dikes are common in the western Kigluaik Mountains where they intrude amphibolite facies metasedimentary schist and gniess (Sainsbury, Smith, and Kachadoorian, 1972). The metasedimentary rocks are derived from 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). 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: Only natural surface exposures are present.
Age: Cretaceous; breccias crosscut mid-Cretaceous amphibolite facies metamorphic rocks and may be related to Cretaceous granitic rocks in the area.
Alteration: Fluorite and silica replacement.

Commodities (Major) - F; (Minor) - Ag, Mo
Development Status: None
Deposit Model: Fluorite breccia pipe in amphibolite facies metasedimentary rocks.

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Link to USGS - Alaska:	NM010

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References