Thetis Prospects, Chichagof District, Sitka Borough, Alaska, USA
This page is currently not sponsored. Click here to sponsor this page.
Geology: The Thesis prospect was located in 1888 (DeArmond 1997). By 1898, the prospect had been developed by two adits, a sawmill, and 2 prospecting mills (Becker, 1898). He described the deposit as a reticulated quartz vein 2 1/2 feet thick with calcite, pyrrhotite, and galena. A mill test of the ore indicated that it contained about $7 in gold (about 0.35 ounce of gold per ton) and $1 in silver. Becker described the host rock as schistose diorite. But modern mapping by Loney and others (1975) assign the rocks to the Jurassic and Triassic, Khaz Formation which consists of graywacke, greenschist, metachert, phyllite, and minor limestone--all cataclastically deformed. Bittenbender and others (1999) located and sampled a 30-foot adit here that cut a quartz vein less than a foot thick, and several thin quartz veinlets The gold values in 4 samples were below the detection limit.
Workings: In 1898, the workings consists of two adits, a sawmill, and two prospecting mills. One 30-foot adit was located by Bittenbender and others (1999).
Age: Triassic or younger based on the age of the host rock.
Production: Apparently none.
Commodities (Major) - Au, Pb
Development Status: None
Deposit Model: Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
5 entries listed. 5 valid minerals.
The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.
Becker, G.F., 1898, Reconnaissance of some gold fields of southern Alaska, with some notes on general geology: U.S. Geological Survey 18th annual report, Part 3, p. 7-86. Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p. Cobb, E.H., 1972, Metallic mineral resources map of the Sitka quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-467, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Sitka quadrangle: U.S. Geological Survey Open-File Report 78-450, 124 p. DeArmond, R.N., 1997, Haleys and Silver Bay, in Around and About Alaska: Sitka Sentinel, series of 29 Articles, April to October, 1997. Loney, R.A., Brew, D.A., Muffler, L.J.P., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p. U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]