Unnamed (upper Ishtalitna Creek)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Other commodities Bi; U
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale TN
Quadrangle map, 1:63,360-scale D-4
Latitude 65.78323
Longitude -151.80065
Nearby scientific data Find additional scientific data near this location
Location and accuracy This record represents occurrences of anomalous rock samples in a two-square-mile mile area of the central Ray Mountains on the divide between Ishtalitna and Banddana creeks. For this record, the site is Alaska Division of Geological and Geophysical Surveys (ADGGS) sample station 92Ha248 (Solie and others, 1993), 0.3 mile north-northeast of the center of section 18, T. 11 N., R. 20 W. of the Fairbanks Meridian. The location is accurate within 1,000 feet.

Geologic setting

Geologic description

The country rocks if the area of this site are granitic rocks of the Cretaceous, Ray Mountains batholith, which trends east-west across the northeast-trending Ruby-Hodzana upland (Dover, 1994). The batholith constitutes the core of the Ray Mountains and includes at least four phases: K-feldspar-rich, porphyritic granite; biotite granite; two-mica granite; and granodiorite. Several K-Ar, Rb-Sr whole rock, and U-Pb age dates on various phases of the batholith range from 104 to 111.6 Ma (Dover, 1994). The isotope chemistry of plutonic rocks from the Ray Mountains indicates that they are S-type plutons derived from or contaminated by continental crust. A brittle-fracture fabric and high-angle fault pattern are superimposed on more ductile older fabrics (Dover, 1994). Brittle structures are expressed mainly as northeast-trending topographic lineaments having generally small, down-to-the-northwest, dip-slip offsets.
In 1992, the Alaska Division of Geological and Geophysical Surveys (ADGGS) investigated the upper Ishtalitna Creek area as part of a mineral resource evaluation of State-selected lands (Solie and others, 1993). The area is in center of the western (main) lobe of the Ray Mountains batholith (Chapman and others, 1982). Rocks in the area are coarse-grained granite, porphyritic granite, pegmatitic granite, fine-grained, two-mica granite, and aplite. The granite is cut by quartz, quartz-tourmaline, and tourmaline veins (Solie and others, 1993). Drill core at one locality is of unknown vintage. Five of seven ADGGS samples of quartz and quartz-tourmaline veins in granite (stations 92Ha248, 92Ha249, 92MW447) contained the following maximum values of one or more of the following elements: 20.1 parts per million (ppm) silver, 219 ppm bismuth, 6,745 ppm lead, and 609 ppm zinc. (Solie and others, 1993). A sample of black, fracture filling in muscovite granite (station 92MW445) contained 52.3 ppm U.
Geologic map unit (-151.803245572284, 65.782726354878)
Mineral deposit model Sn-polymetallic veins, polymetallic veins (Cox and Singer, 1986; models 20b and 22c).
Mineral deposit model number 20b, 22c
Age of mineralization Cretaceous, the age of the granite host rock.

Production and reserves

Workings or exploration In 1992, the Alaska Division of Geological and Geophysical Surveys (ADGGS) investigated the upper Ishtalitna Creek area as part of a mineral resource evaluation of State-selected lands (Solie and others, 1993). The area is in center of the western (main) lobe of the Ray Mountains batholith (Chapman and others, 1982). Rocks in the area are coarse-grained granite, porphyritic granite, pegmatitic granite, fine-grained, two-mica granite, and aplite. The granite is cut by quartz, quartz-tourmaline, and tourmaline veins (Solie and others, 1993). Drill core at one locality is of unknown vintage. Five of seven ADGGS samples of quartz and quartz-tourmaline veins in granite (stations 92Ha248, 92Ha249, 92MW447) contained the following maximum values of one or more of the following elements: 20.1 parts per million (ppm) silver, 219 ppm bismuth, 6,745 ppm lead, and 609 ppm zinc. (Solie and others, 1993). A sample of black, fracture filling in muscovite granite (station 92MW445) contained 52.3 ppm U.
Indication of production None

References