Nataga Skyline

Prospect, Probably inactive

Commodities and mineralogy

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale C-4
Latitude 59.61
Longitude -136.29
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is approximately 0.2 miles from the Alaska-British Columbia border and about 2.5 miles, N68E of the sharp bend in the border that occurs at Mount Seltat. It is shown as number 1 on sheet 1 of Still and others (1991).

Geologic setting

Geologic description

Still and others (1991) report that a 40-foot adit and several prospect pits at this site that were driven on sphalerite-rich skarn were probably developed before World War II. An open cut was dug into highly weathered gossan which contains abundant arsenopyrite. The following description is summarized from Still and others (1991) who attribute the information to a personal communication from A. H. Clough (1989).
The mineralization is in a skarn zone of unknown thickness that is at least 300 feet wide and 2,500 feet long. The skarn zone includes gray marble, biotite schist, and garnet-epidote-diopside-actinolite-quartz skarn. Ore minerals include magnetite, sphalerite, galena, chalcopyrite, arsenopyrite, pyrite, pyrrhotite, and scheelite. Granitic rocks of variable composition and texture occur outside of the skarn zone; fine- to medium-grained diorite was the most common. Porphyritic latite dikes and very fine-grained siliceous alaskite were also noted. Southwest of the skarn zone, granular iron-stained granite contained sparse fine-grained molybdenite and ferrimolybdite. The mineralization is scattered throughout the skarn zone; sphalerite is the most common ore mineral. Magnetite and/or pyrrhotite were present in all of the skarn. The actual margins of the skarn zone were not observed.
Still and others (1991) cite the following sample results. A sample of skarn with visible chalcopyrite and galena from a 40-foot adit at the site contained 511 ppm copper and 1,883 ppm zinc. A sample of the gossan with arsenopyrite from the open cut contained 15.7 ppm silver, 4,206 ppm copper, and 17,982 ppm zinc.
The age of the skarn alteration and mineralization is not well established and published detailed geologic mapping is lacking in the vicinity of this prospect. However, Cretaceous to Tertiary intrusive rocks mapped to the east by Gilbert and others (1990) suggest a similar age for this mineralization.
Geologic map unit (-136.291852848639, 59.6096837885864)
Mineral deposit model Polymetallic skarn (Cox and Singer, 1986; model 18b or 18c).
Mineral deposit model number 18b or 18c
Age of mineralization Probably Cretaceous or Tertiary based on the ages of intrusive rocks mapped to the east by Gilbert and others (1990).
Alteration of deposit Skarn.

Production and reserves

Workings or exploration A 40-foot adit, several prospect pits, and an open cut were developed, probably before World War II (Still and others, 1991).
Indication of production Undetermined