Greisen Prospect (on Tin Creek), Lost River Valley, Port Clarence Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Greisen Prospect (on Tin Creek)	Prospect
Lost River Valley	Basin
Port Clarence Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: Tin Creek is an east tributary to Lost River whose confluence is located 4.5 miles upstream from the mouth of Lost River on the Bering Sea. The Gresien prospect is in the eastern part of the Tin Creek granite stock, a rounded hill in the headwaters of Tin Creek (Sainsbury, 1969). This rounded hill, between Tin Creek and its small north tributary, reaches elevations of just over 1,150 feet. This locality 10 of Cobb and Sainsbury (1972). Cobb (1975) summarized relevant references under the name 'Tin Cr., trib. Lost R.'.
Geology: The headwaters of Tin Creek are in an area where a small stock of biotite granite, the Tin Creek stock (Sainsbury, 1969; Hudson and Arth, 1983) intrudes Orovician limestone and dolomite. The Tin Creek stock covers a 1,000 by 2,000 foot area on the crest of the rounded hill between Tin Creek and its northern tributary. The south contact of the stock is irregular and includes granite offshoots, dikes, and apophyses in the bordering carbonate rocks. An eastern part of the Tin Creek granite stock is cut by parallel greisen sheets with peripheral alteration selvages. Seven samples of this greisen (Hudson, 1983) contained 525 to 3,020 ppm tin, 1,040 ppm to 1.7% lead, 8,400 to greater than 20,000 ppm fluorine, 550 to greater than 1,000 ppm arsenic, and 5 to 24 ppm silver. Copper (to 280 ppm) and zinc (to 3,630 ppm) are elevated in some of these samples and gold (5 ppb) was detected in four. The style of mineralization here is interpreted to be similar to that at depth in the Lost River Mine endogreisen prospect (TE050).
Workings: Little exploration has taken place here but some surface trenches or pits may be present.
Age: The age of the mineralization is assumed to be related to the development of tin systems in the Lost River area and therefore Late Cretaceous, the age of the tin-mineralizing granites there (Hudson and Arth, 1983).
Alteration: Typical greisen alteration with feldspar destruction and extensive replacement by quartz, topaz, and white mica in the host granite. Some quartz veining may be present in the cores of greisen zones. Tourmaline and fluorite are also present in altered rocks. Alteration selvages are less completely greisenized granite.
Reserves: Not defined

Commodities (Major) - Sn; (Minor) - Ag, Cu, Pb, Zn,
Development Status: None
Deposit Model: Tin greisen (Cox and Singer, 1986, model 15c)

Other Databases

Link to USGS - Alaska:	TE043

Other Regions, Features and Areas containing this locality

References