Portage Creek Mine, Circle Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Portage Creek Mine	Mine
Circle Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

There are two different Portage Creeks in the Circle mining district, both of which flow away from the same divide. One creek flows south-southwest and has not yielded gold. The Portage Creek discussed for this site flows north-northeast into Medicine Lake.
Location: The placered area extends about 3/4 mile up and downstream from the intersection of the coordinates. Portage Creek flows in a northeasterly direction and can be accessed by gravel road just a few miles east of Circle Hot Springs.
Geology: Portage Creek near its source is underlain by Cretaceous granite, then flows over chorite-muscovite schist and Tertiary granite before crossing into the Tintina fault zone. Almost all of the mining has been conducted south (upstream) of the Tintina fault zone. Gold is restricted to the upper 0.5 meters of the orange, schist-rich gravel. A high percentage of the detritus in Portage Creek is colluvium, so the mined gravel is poorly sorted (Yeend, 1991). One meter of muck typically overlies 2 meters of colluvial-alluvial gravel. A defined 'paystreak' is not often present due to the colluvial mixing and lack of alluvial water to wash and sort. Because of the thick colluvial gravel cover on the side slopes, the mined gravel channel is quite narrow, only 20 to 30 meters (Yeend, 1991). Placer concentrates contain allanite, arsenopyrite, bismuthinite, cassiterite, garnet, gold, hematite, ilmenite, magnetite, monazite, pyrite, scheelite, sphalerite, sphene, spinel, topaz, tourmaline, uranothorianite, wolframite and zircon (Nelson and others, 1954). Gold was not discovered on the creek until the early 1900's (Brooks, 1907). Full-scale mining did not begin on the creek until 1933. Two miners worked the upper valley in 1936. One operation consisted of drift mining and one was a prospecting shaft (Mertie, 1938). Gravel valued at 0.025 to 0.0625 ounces per cubic yard was being mined in 1937 by several miners shoveling in an opencut (Lampright, 1996, p. 74). There were two operations on the creek in 1975 and anywhere from two to five operations per year during the 1980's (Yeend, 1991). Points North operation on Portage Creek was the biggest producer of gold in the Circle district in 1994 (Swainbank and others, 1994, p. 28). Ten ounces of gold were reportedly recovered from one claim on the creek in 1906 (Brooks, 1907, p. 198) and various mines have been operating on and off to the present. Points North operation on Portage Creek was the biggest producer of gold in the Circle district in 1994 (Swainbank and others, 1994, p. 28).
Workings: Gold was not discovered on the creek until the early 1900's (Brooks, 1907). Full-scale mining did not begin on the creek until 1933. Two miners worked the upper valley in 1936. One operation consisted of drift mining and one was a prospecting shaft (Mertie, 1938). Gravel valued at 0.025 to 0.0625 ounces per cubic yard was being mined in 1937 by several miners shoveling in an opencut (Lampright, 1996, p. 74). There were two operations on the creek in 1975 and anywhere from two to five operations per year during the 1980's (Yeend, 1991). Points North operation on Portage Creek was the biggest producer of gold in the Circle district in 1994 (Swainbank and others, 1994, p. 28).
Production: Ten ounces of gold were reportedly recovered from one claim on the creek in 1906 (Brooks, 1907, p. 198) and various mines have been operating on and off to the present. Points North operation on Portage Creek was the biggest producer of gold in the Circle district in 1994 (Swainbank and others, 1994, p. 28).

Commodities (Major) - Au; (Minor) - Bi, Cu, Sn, U, W, Zn
Development Status: Yes; medium
Deposit Model: Placer gold deposit (Cox and Singer, 1986; model 39a)

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Link to USGS - Alaska:	CI047

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References