Cache Mountain

Occurrence, Inactive

Commodities and mineralogy

Main commodities Sn
Other commodities W
Ore minerals cassiterite
Gangue minerals chlorite; clay; epidote; hematite; magnetite; plagioclase; pyrrhotite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale LG
Quadrangle map, 1:63,360-scale B-1
Latitude 65.4853
Longitude -147.3166
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The Cache Mountain tin occurrence consists of greisen rubble located on a south-trending ridge leading from the summit of Cache Mountain at an elevation of 3,840 feet. Elevations in the prospect area range from 3,500 to 4,700 feet. The occurrence is in the SW1/4 SE1/4 sec. 27, T. 8 N., R. 2 E of the Fairbanks Meridian. Accuracy of the location is within about 1,500 feet.
Cache Mountain is a prominent 4,772-foot high mountain in the White Mountains area about 40 miles due north of Fairbanks and about two miles north of this occurrence.

Geologic setting

Geologic description

Cache Mountain is underlain by a biotite granite pluton of similar composition to the Lime Peak pluton to the east. Both the intrusions are composed of four apparent phases: a fine-grained to porphyritic biotite granite, a coarser grained biotite granite, lesser phases of smoky, finely crystalline quartz biotite-muscovite tourmaline granite locally quartz-rich, and a younger cross-cutting porphyritic rhyolite. Based on A-F-M and K2O-Na2O-CaO ternary plots these phases compare closely to Lime Peak (Warner, 1984).
An occurrence of tin greisen was located along the ridge south of the mountain where a chip sample of scattered mineralized rubble over an area 50 feet across assayed 0.105 percent tin (Warner, 1984). Berryhill, 1964, also reported a similar occurrence from the general area that assayed 0.22 percent tin although the exact location has been lost over the years. Petrographic examination of Berryhill’s samples by the U.S. Bureau of Mines described the samples as tourmaline-bearing greisen rather than lithium enriched (Berryhill, 1964).
Analyses of heavy mineral concentrates were weakly to moderately anomalous for tin were reported by Warner (1984) in drainages on either side of the ridge.
Geologic map unit (, )
Mineral deposit model Granite-hosted greisen tin veins.
Age of mineralization Quartz monzonite of the Cache Mountain pluton was dated at 59.8±1.8 Ma, Paleocene (Holm, 1973; Rinehart and others, 1997).
Alteration of deposit Greisen, locally argillic, limonite, goethite, hematite staining and corroded quartz, wider zones of sericite, argillic and chloritic alteration. Tourmaline is found in the greisen (Warner, 1984).

Production and reserves

Workings or exploration The Cache Mountain area was selected for study by the U.S. Bureau of Mines in 1979 because of on-going Strategic and Critical minerals assessments in Alaska by the Bureau of Mines. Warner (1984) reports only one sample of finely crystalline granite float yielded evidence of potential mineralization; 1,050 parts per million (ppm) tin was found. Pan Concentrate samples from creeks radiating from Cache Mountain yielded between 370 to 2,390 ppm tin and 200 to 400 ppm tungsten (Warner, 1984). In comparison to tin values in pan concentrates collected elsewhere in the White Mountain upland area, none of the Cache Mountain values are highly anomalous (Warner, 1984).
Indication of production None

Additional comments

Claims (BEE block) staked in area by Mapco Minerals in 1976; no further work was performed.

References

Reporters J.C. Barker
Last report date 4/6/2017