SM

Occurrence, Inactive

Commodities and mineralogy

Main commodities Zn
Other commodities Ag; Au; Cu; Pb
Ore minerals chalcopyrite; galena; sphalerite
Gangue minerals graphite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.1823
Longitude -144.4684
Nearby scientific data Find additional scientific data near this location
Location and accuracy The SM occurrence is on a nunatak and is accessible only by helicopter (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1978). The occurrence is at an elevation of about 6,600 feet; it is one-half mile east of peak 7140 in the NE1/4 section 9, T. 16 N., R. 5 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The SM occurrence is in the Hayes Glacier unit of Devonian to Mississippian age (Nokleberg and others, 1992) and consists of a folded exposure of 7 feet of massive sulfides exposed on a nunatak. At least four distinct types of massive sulfide mineralization are found in glacial debris below the nunatak. These include: (1) banded pyrite-sphalerite-galena(-chalcopyrite), (2) massive pyrite, (3) massive pyrrhotite with minor chalcopyrite and pyrite, and (4) banded pyrite and sphalerite in a matrix of black graphitic siltstone. The abundance of each of these types of mineralization suggests that a substantial deposit may be present under the glacial ice. Isoclinal folding is prominent in outcrop. The massive sulfides occur at the contact between a pyritic and sericitic, felsic metavolcanic layer and a black graphitic siltstone. This contact appears to be repeated in several locations on the nunatak (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1978). Average metal values of the massive sulfide were 0.26 percent copper, 0.27 percent lead, 2.97 percent zinc, 0.62 ounce of silver per ton, and 0.05 ounce of gold per ton (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1978).
The Hayes Glacier rocks that host the SM occurrence consists of fine-grained phyllitic schists and mylonite derived from sedimentary and volcanic protoliths. The rocks locally display intense structural deformation due to their proximity to the Denali Fault. The rocks are metamorphosed to lower greenschist facies and are less metamorphosed than Jarvis Belt rocks to the northeast (Nokleberg and others, 1992). The basal part of the unit consists of mafic to intermediate composition metavolcanic rocks overlain by interbedded felsic metavolcanic units and extensive pelitic and graphitic metasedimentary rocks (Dashevsky and others, 2003).
Geologic map unit (-144.470638113475, 63.1819145071605)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Devonian to Mississippian, on the basis of the age of the host rocks.

Production and reserves

Workings or exploration This prospect was staked in 1976 by Resource Associates of Alaska, and limited exploration followed. Some sampling and a few lines of magnetic and VLF geophysical surveys were run. Strong anomalies from both techniques were found to correlate with known mineralization. A hand-held drill was used to sample banded, pyritic massive sulfide outcrops at the northeastern corner of the SM nunatak to a maximum depth of 4 feet.
Indication of production None

Additional comments

The unpublished data that is cited can be seen by contacting Grayd Resources Inc. in Vancouver, B.C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.

References