|Quadrangle map, 1:250,000-scale||MH|
|Quadrangle map, 1:63,360-scale||A-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Limestone Creek, formerly named Lake Creek and also called Lime Creek, is a tributary of the Middle Fork Chistochina River. The Limestone Creek placer mine is about 0.1 mile northeast of the present course of Limestone Creek. The deposit was mined over a distance of about 0.8 mile. The mine is near the southeast corner of section 34, T. 20 S., R. 16 E., Fairbanks Meridian. Limestone Creek is locality 28 on figure 6 of Cobb (1979 [OFR 79-238]) and is included with nearby deposits as locality 68 of MacKevett and Holloway (1977). The mine corresponds generally to locality 13 in table 3 of Nokleberg and others (1991).|
Limestone Creek is the main placer deposit in the drainage of the Middle Fork Chistochina River; minor gold-bearing creeks such as Bedrock Creek (MH310) and Kramer or Kraemer Creek (MH311), also tributaries of the Middle Fork, are sometimes lumped with the Limestone Creek deposit.
Mining on Limestone Creek mainly took place on a bench on the north side of and subparallel to modern Limestone Creek. The gravels generally consist of about 35 to 45 feet of boulder-gravel wash underlain by a blue-gray glacial clay. The best 'pay' is in an iron-stained gravel zone on clay false bedrock (Moffit, 1912). Locally the gravel section is as much as 70 feet thick (Moffit, 1944).
This placer deposit is not an alluvial deposit of Limestone Creek but is a bench deposit on the west side of the Middle Fork Chistochina River.
The deposit is in post-glacial and outwash gravels deposited on a slightly irregular bedrock floor that was scoured by ice moving from the north and west. Gravel, cobble, and boulder deposits contain transported granite and schist that are intermixed with bedrock materials of local origin. A source of some exotic materials and possibly gold was recognized in a gravel exposed about a mile north of the Limestone Creek mine site. As described by Moffit (1944), the gravel resembles the 'round wash' conglomerate of Tertiary age.
Drilling disclosed that the gold was scattered through the bench gravels but was enriched near bedrock; gold-bearing gravel was fairly well stratified and, at one place, formed two gold-bearing gravel layers separated by a compacted gravel false bedrock (Moffit, 1944).The placer gold is fairly fine grained. Placer concentrates also contain shot size and large (2 to 3 pounds) fragments of native copper and galena and lesser amounts of chromite, platinum group elements (PGE), pyrite, scheelite, and some native silver. The occurrence of platinum metals was also noted by Chapin (1919) and Rose (1967). Olivine and magnetite occur in the concentrates (Moffit, 1944). Moffit (1912) proposed a local bedrock source for copper but a distal source for gold.
|Geologic map unit||(-144.645030874305, 63.1319074210324)|
|Mineral deposit model||Placer Au-PGE (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||Pleistocene.|
|Workings or exploration||Mining began on Limestone Creek in 1908 (Moffit, 1909). The mine was active intermittently until 1942, but during many years the main activity was prospecting and drilling. A ten-man operation was reported in 1922 (Brooks and Capps, 1924). A major exploration program began in about 1934 (Moffit, 1937). Holes were drilled on 100-foot centers on five northwest-trending lines spaced 450 feet apart (Moffit, 1944); the deposit was also explored with pits and shafts. The deposit was prepared for mining in the late 1930s and 1940; the work included 5,900 feet of new ditches and an 800-foot-long dead cut to allow placement of sluice boxes for the hydraulic operation. An extensive operation began in 1941 to mine the demonstrated resource. Some gold was recovered, but the operation was terminated by World War II (Moffit, 1954). Some of the resource may have been mined in the late 1970s and early 1980s during a period of high gold price.|
|Indication of production||Yes|
|Reserve estimates||There probably is a low-grade but possibly large gold resource in bench gravel on the west side of the Middle Fork Chistochina River.|
|Production notes||Limestone Creek produced at least 580 ounces of placer gold in and before 1934 (Moffit, 1944). It probably has a total production of more than 1,000 ounces.|
Brooks, A.H., and Capps, S.R., 1924, The Alaska mining industry in 1922: U.S. Geological Survey Bulletin 755-A, p. 1-56.
Chapin, Theodore, 1919, Platinum-bearing auriferous gravels of Chistochina River: U.S. Geological Survey Bulletin 692-C, p. 137-144.
Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p.
MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000.
Moffit, F.H., 1909, Mining in the Kotsina-Chitina, Chistochina, and Valdez Creek regions: U.S. Geological Survey Bulletin 379-D, p. 153-160.
Moffit, F.H., 1912, Headwater regions of Gulkana and Susitna Rivers, Alaska, with accounts of the Valdez Creek and Chistochina placer districts: U.S. Geological Survey Bulletin 498, 82 p.
Moffit, F.H., 1937, Recent mineral developments in the Copper River region: U.S. Geological Survey Bulletin 880-B, p. 97-109.
Moffit, F.H., 1944, Mining in the northern Copper River region, Alaska: U.S. Geological Survey Bulletin 943-B, p. 25-47.
Moffit, F.H., 1954, Geology of the eastern part of the Alaska Range and adjacent area: U.S. Geological Survey Bulletin 989-D, p. 65-218.
Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000.
|Reporters||W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)|
|Last report date||12/28/2001|