Unnamed Mine (ARDF - NB021; southeast flank of White Mountain), Chisana Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
Unnamed Mine (ARDF - NB021; southeast flank of White Mountain)	- not defined -
Chisana Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

The mine is in the Wrangell-St. Elias National Preserve.
Location: This mine is low on southeast flank of White Mountain. It is at an elevation of about 3,750 feet, about 2,000 feet west-northwest of Nabesna. The map site is about 0.4 mile west of the center of section 21, T. 7 N., R. 13 E. of the Copper River Meridian. This is locality M4 of Lowe and others (1982), locality 14 of Richter and others (1975 ), and it is included in National Park Service locality WRST-14 (unpublished data). Cobb and Richter (1980) include this mine under the name 'Nabesna (Mining Corp.)'. It is located to within about 100 feet.
Geology: In the early 1900s, the Royal Development Co. found and briefly exploited a gossan zone developed over a gold-bearing sulfide deposit. The sulfide deposit is in a sheared intrusive rock and adjacent contact-metamorphosed limestone (Moffit and Knopf, 1909). Mining was in a surface cut where a 1- to 4-foot-wide mineralized zone was exposed. Pyrite is the dominant mineral in the deposit but if it is similar to others in the area (NB022), it probably also contains chalcopyrite, galena, and sphalerite A 16-inch-wide sample taken across the deposit assayed 0.06 ounce of gold per ton and 0.20 ounce silver per ton (Pilgrim, 1931, p. 60-61). A 3-stamp mill was erected in 1906; it processed about 60 tons of ore and reportedly recovered 0.6 ounce of gold per ton. Two adits totaling 130 feet in length were subsequently driven 200 feet below the gossan outcrop without encouraging results and the original claims were allowed to lapse in 1914. This mine is now included in the patented claim group surrounding the Nabesna mine (NB022). Richter and others (1975) describe this deposit as a quartz diorite stock with disseminated pyrite and quartz-pyrite veins. They consider it to be a disseminated gold deposit. The deposit is in the contact zone of a mid-Cretaceous granodiorite and quartz diorite stock that intrudes Triassic limestone and dolomite (Lowe and others, 1982). Skarn assemblages are well developed in the general area (see NB022) and include calcic skarn with abundant garnet and pyroxene, and magnesian skarn with magnetite and serpentine (Weglarz, 1991; Newberry and others, 1997). Sulfide minerals are common in the calcic skarn and magnetite is common in the magnesian skarn. Chalcopyrite and other sulfide minerals are common in the calcic skarn and Newberry and others (1997) consider the deposits in the area to be gold-rich copper skarns. The gold-bearing sulfide-rich pods, lenses, and veins are commonly small bodies localized in marble-front replacements and crosscutting shears (Newberry and others, 1997, figure 9). A concordant biotite/hornblende K/Ar date for the intrusive rocks in the area is 114 +/- 3.4 Ma (Richter, Lanphere, and Matson, 1975).
Workings: Mining was in a surface cut where a 1- to 4-foot-wide mineralized zone was exposed. A 3-stamp mill was erected in 1906; it processed about 60 tons that contained about 0.6 ounce of gold per ton. Two adits totaling 130 feet in length were subsequently driven 200 feet below the gossan outcrop without encouraging results and the original claims were allowed to lapse in 1914. This mine is now included in the patented claim group surrounding the Nabesna mine (NB022). Exploration including diamond drilling occurred during the 1980s in the area.
Age: Mid-Cretaceous. A concordant biotite/hornblende K/Ar date for the intrusive rocks in the area is 114 +/- 3.4 Ma (Richter, Lanphere, and Matson, 1975).
Alteration: Oxidation. Calc-silicate and sulfide replacement.

Commodities (Major) - Ag, Au
Development Status: Yes; small
Deposit Model: Cu skarn (Cox and Singer, 1986; model 18b)

Other Databases

Link to USGS - Alaska:	NB021

Other Regions, Features and Areas containing this locality

References