|Quadrangle map, 1:250,000-scale||TN|
|Quadrangle map, 1:63,360-scale||B-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Bonanza Creek placer prospect is in the south half of section 19, T. 6 N., R. 18 W, of the Fairbanks Meridian. The site also includes a portion of Bonanza Creek valley about 900 feet upstream from its mouth, which was drilled in 1943 by the U.S. Bureau of Mines (Thomas and Wright, 1948 [RI 4322]). The drill sites are on the border between sections 19 and 30, in T. 6 N., R. 18 W. The site corresponds to location 18 of Cobb (1972), and roughly to the location of Bonanza Creek, U.S. Bureau of Land Management MAS number 0020480012.|
Bedrock in the area of the Bonanza Creek gold-cassiterite (tin) placer deposit consists of greenstone, metachert, dolomite, marble, calcareous schist, and siliceous mica schist (Chapman and others, 1982). Although granitic rocks were reported by Eakin (1916), none were found in later mapping by Chapman and others (1963, 1982). Thomas and Wright (1948 [RI 4322]) reported that the bedrock was complexly folded and faulted, resulting in irregularities on the bedrock surface, called 'reefs.' Although this bedrock apparently is not the source of the gold or cassiterite, the reefs proved to be excellent for concentrating these heavy minerals.
The gravels in Bonanza Creek are about 6 feet thick, with only 2.5 feet of overburden. Pebbles of cassiterite commonly contain quartz, indicating that they are derived from quartz-cassiterite veins. Both cassiterite and gold are concentrated in the bottom two feet of gravel, although in places they penetrate fractures in the upper few feet of bedrock. Chapman and others (1963) did not find other metallic minerals, although they describe limonite-stained pits (presumably after pyrite) in quartz veins along the ridges bordering Bonanza Creek.Thomas and Wright (1948 [RI 4322]) described many prospect shafts in the Bonanza Creek area that were sunk prior to a 1943 U.S. Bureau of Mines exploration project. This project included drilling on Morelock Creek (TN033) and five holes at 50-foot intervals across the Bonanza Creek valley approximately 900 feet above its mouth. The average grades were 0.1492 pound of cassiterite and 0.0328 ounce of gold per square yard of bedrock on Bonanza Creek.
|Geologic map unit||(-151.338928620721, 65.3275864579046)|
|Mineral deposit model||Placer Au(-Sn) (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary.|
|Workings or exploration||
Thomas and Wright (1948 [RI 4322]) described many prospect shafts in the Bonanza Creek area that were sunk prior to a 1943 U.S. Bureau of Mines exploration project. This project included drilling on Morelock Creek (TN033) and five holes at 50-foot intervals across the Bonanza Creek valley approximately 900 feet above its mouth. The average grades were 0.1492 pound of cassiterite and 0.0328 ounce of gold per square yard of bedrock on Bonanza Creek.Doyon, Ltd., contracted exploration in the Tanana Village Block in 1977, 1979, and 1982, and performed their own exploration in 1985. Soil(?) sampling yielded mainly copper, lead, zinc, tin, and gold anomalies (Placer Dome, 1989).
|Indication of production||Undetermined|
Additional commentsBonanza Creek feeds into Morelock Creek (TN033), which flows on lands selected by or conveyed to Doyon, Ltd. For further information, contact Doyon, Ltd., at 1 Doyon Place, Suite 300, Fairbanks, Alaska, 99701-2941.
Chapman, R.M., Coats, R.R., and Payne, T.G., 1963, Placer tin deposits in central Alaska: U.S. Geological Survey Open-File Report 239, 53 p.
Chapman, R.M., Yeend, W.E., Brosge, W.P., and Reiser, H.N., 1982, Reconnaissance geologic map of the Tanana quadrangle: U.S. Geological Survey Open-File Report 82-734, 20 p., scale 1:250,000.
Cobb, E.H., 1972, Metallic mineral resources map of the Tanana quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-371, 1 sheet, scale 1:250,000.
Cobb, E.H., 1977, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Tanana quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-432, 98 p.
Eakin, H.M., 1916, Mineral resources of the Yukon-Koyukuk region: U.S. Geological Survey Bulletin 631, 88 p.
North Star Exploration, Inc., 1999, Doyon, Ltd., Report 99-48: Unpublished report held by Doyon, Ltd., Fairbanks, Alaska.
Placer Dome, 1989, Doyon, Ltd., Report 89-11: Unpublished report held by Doyon, Ltd., Fairbanks, Alaska.
|Reporters||G.E. Graham (ADGGS)|
|Last report date||12/10/2000|