The following is excerpted from the USGS publication PRINCIPAL GOLD-PRODUCING DISTRICTS OF THE UNITED STATES By A. H. Koschmann and M. H. Bergendahl. This publication is invaluable for those wishing an overview of gold production in the United sates, and in particular it is useful in determining areas that may be worth prospecting in the future. The Alaska portion of the publication is being reproduced here as time allows. Those wishing information on other states, or who wish to own the original publication may find it online at http://www.akmining.com/cart/bookgoldmining.htm#bo704098

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PRINCIPAL GOLD-PRODUCING DISTRICTS OF THE UNITED STATES
By A. H. Koschmann and M. H. Bergendahl
United States Geological Survey Professional Paper 610 : 1968

ALASKA

Gold, the lure that drew settlers across the wide prairies and into the most remote mountain gullies in our Western States, proved also to be the dominant factor in the settlement of Alaska. This most important mineral commodity of the State was known in Alaska as early as 1848, long before the territory was acquired from Russia by the United States in 1867. P. P. Doroshin, a Russian mining engineer, made the discovery in the gravels of the Kenai River on the Kenai Peninsula, but there was no great excitement and apparently no gold was mined (Martin and others, 1915, p. 181-182). A second discovery of placer gold in 1865-66 on the Seward Peninsula by a party exploring for a telegraph route similarly failed to arouse much interest (Collier and others, 1908, p. 13-14).

Alaskan gold mining began in southeast Alaska. In 1869 miners who had been disappointed in the Cassiar gold district in British Columbia discovered gold placers at Windham Bay and Sumdum Bay southeast of Juneau. In 1870-71 the first gold produced in Alaska, reported to be worth $40,000, was extracted from these placers (Wright, 1906, p. 2). At about this time the first attempts to mine lode gold were made near Sitka (Knopf, 1912, p. 8). In the early 1870’s extensive copper deposits were found on Prince of Wales Island, but because of the remoteness of the area from transportation facilities, these were not developed for many years. The major lode gold deposits of Alaska were found in 1880 at Juneau, and by 1883 Juneau was the mining center of the territory (Wright, 1906, p. 3). Encouraged by the successes at Juneau, the prospectors spread through southern Alaska and made important gold discoveries at Berners Bay and Eagle River on the mainland near Juneau, at Klag Bay on Chichagof Island, at Willow Creek near Anchorage, and even on far-off Unga Island, 1,000 miles to the west.

Numerous gold districts, the most important of which are Nome, Council, and Fairhaven, are on the Seward Peninsula. This region was prospected first by gold seekers drawn north by the great Klondike (Yukon Territory, Canada) rush of 1897-98. By 1898 the discovery of the rich Nome placers triggered a stampede to the new area and led to the rapid development of the entire peninsula. Nome, the second largest gold-producing district in Alaska, was active until 1962.

The vast Yukon drainage basin has produced more gold than any other region in Alaska, even though it was the most recent of the gold-producing regions to be exploited. With transportation virtually limited to river travel, the great distances from gold deposits to supply and population centers inhibited any large-scale mining in the early days. The first gold discoveries were made in 1878 (Mertie, 1937, p. 4); however, tales of gold had been circulated years earlier by traders and trappers who set up posts at various points along the Yukon River. Smith (1933, table facing p. 96) listed the earliest production for this region in 1883 from the Fortymile district. The important placers at Fairbanks were discovered in 1902, and by 1910 lode mines were active in this district. The Fairbanks placers proved amenable to large-scale dredging operations, which soon made this district the largest gold producer in Alaska.

As transportation facilities improved after 1900, new gold discoveries were made in the more remote areas, and previously known deposits were developed and mined. This activity extended into the 1930’s, and several lode and placer districts in the Yukon basin were activated in this interval.

Gold mining in Alaska was seriously affected in 1943 by the imposition of War Production Board Order L-208 which closed nearly all of the gold mines during World War 1I (fig. 4). After the war the placer mines of the Fairbanks district resumed large-scale operations, and this single district accounted for more than half the total annual gold production for Alaska during 1950-65. The lode mines in Alaska were virtually inactive during 1942-65.

Of the total value of $722,122,186 of gold (28,859,718 ounces) produced in Alaska from 1880 to 1957, $504,076,577 came from placer mines (U.S. Bureau of Mines, 1957, p. 83, 85). During 1958-59 the gold production amounted to 365,353 ounces, most of which came from placers (U.S. Bureau of Mines, 1959, p. 84). Most of the lode gold has come from the Juneau district in southeast Alaska, and an unknown but probably small amount has been produced as a byproduct of copper ores in the Prince William Sound region. The gold production of Alaska before 1880 is unknown, but probably was not great.

Emmons (1937, p. 203) discussed the general relationships of gold deposits to geology. He pointed out that the chief lode deposits are associated with Mesozoic granite that have intruded rocks of Precambrian, Paleozoic, and Mesozoic ages. This belt of intrusives extends from the Seward Peninsula to the Yukon Territory. The lode deposit on Unga Island in the Aleutian Islands is in Tertiary andesite. The placer deposits are widespread, occurring along nearly all the major rivers and their tributaries, and even in beach sands in the Nome area, on Kodiak Island, Yakataga, Lituya Bay, and Cook Inlet.

As in earlier reports of the Geological Survey (for instance, Smith, 1939), the State is subdivided into nine geographical regions: Cook Inlet-Susitna, Copper River, Kuskokwim, Northwestern, Seward Peninsula, Southeastern, Southwestern, Yukon, and Prince William Sound. The regions and the individual districts within the regions are discussed in this report.

Fig. 4 Alaska Gold Production 1880-1965

COOK INLET-SUSITNA REGION

Bounded roughly by the Aleutian or Alaska Peninsula on the southwest, the Alaska Range on the west and north, and by the Talkeetna Mountains on the east, the Cook Inlet-Susitna region includes the Kenai Peninsula, Valdez Creek, Willow Creek, and Yentna-Cache Creek mining districts.

Gold was first discovered in Alaska in 1848 in the gravels of the Kenai River. Apparently this gold was not present in minable quantities, and it was not until the 1890's that minable placers were found in the Turnagain Arm area (Martin and others, 1915, p. 181-183). The first lode deposits in the Cook Inlet-Susitna region were found in 1896 also in the Turnagain Arm area, more precisely, the Moose Pass-Hope area; however, the deposits, although rich, were of small tonnage, and there was very little lode production before 1911 (Martin and others, 1915, p. 129-131).

Placers in the Valdez Creek district, in the southern foothills of the Alaska Range, were worked from 1904 to 1924 (Ross, 1933b, p. 427-428) and desultory operations were carried on as recently as 1947 (E. H. Cobb, written communication, 1962).

In the western part of the Cook Inlet-Susitna region, placers were discovered in the Yentna-Cache Creek district in 1905 (Capps, 1913, p. 10). These deposits were moderately productive through 1957. The most productive district in the entire region is the Willow Creek district, about 20 miles north of the towns of Palmer and Wasilla, where placers were discovered in 1897. The first lode claims were located in 1906 (Capps, 1913, p. 50) and were worked fairly steadily until the early 1950's.

From 1880 through 1959, a recorded total of 919,532 ounces of gold was produced from the Cook Inlet-Susitna region. Of this, 598,361 ounces was from lode mines, 324,370 ounces from placers, and 6,801 ounces from undifferentiated sources. After the end of World War II production from both lode mines and placers declined markedly.

KENAI PENINSULA DISTRICT

The Kenai Peninsula is near the center of the southern coastline of Alaska, immediately northeast of the Alaska Peninsula.

The districts of Moose Pass-Hope, Girdwood, and Turnagain Arm - all in the central and northern part of the peninsula - have been combined in this discussion because most of their production data have been combined under "Kenai Peninsula."

Numerous small placers were discovered in the Turnagain Arm area in the early 1890's, but no significant production occurred until news of the auriferous gravels on Mills and Canyon Creeks brought several thousand prospectors to the area in 1896 (Martin and others, 1915, p. 182-183). Two years later another influx occurred. In a short time the small richer deposits were exhausted and the hand-operated rockers and sluices were supplanted by hydraulic plants that successfully mined the large reserves of low-grade gravels.

Lode mining, overshadowed by the placer operations, has been conducted chiefly in the Moose Pass-Hope camp and to a lesser degree in the Girdwood camp. The first indications of economic lode deposits were noted in 1896, but interest was diverted for a number of years to the more accessible placers. The lode deposit at the Hirshey mine, discovered in 1911, became the most consistently productive in the district (Tuck, 1933, p. 489-494). Lode mining continued sporadically until the end of World War II, when it dwindled to almost nothing.

Total recorded gold production from the Kenai Peninsula from 1895 through 1959 was 23,700 ounces from lodes, 96,500 ounces from placers, and 175 ounces from undifferentiated sources. Data from 1931 through 1945 are incomplete, so that the figures given here are minima.

The geology of the Kenai Peninsula was described by Martin and others (1915), Tuck (1933), and Park (1933). The oldest rocks on the peninsula are schists and crystalline limestones of uncertain age; however, the most widely distributed rocks are slates and graywackes that range in age from Paleozoic or Early Triassic to possible Late Cretaceous (Martin and others, 1915, p. 33-35). Granitic intrusive masses are abundant in the slaty rocks along the southern and eastern coasts. The Kenai Formation, of Eocene or younger Tertiary age, is exposed in the low country in the southwest part of the peninsula, north of Kachemak Bay, and consists of coal-bearing sand and clay. This formation is 15,000-20,000 feet thick and contains economically important oil and gas accumulations (Lian and Simonson, 1962, p. 271). Quaternary gravels - mostly till, outwash, and terrace sands and gravels - cover vast areas of lowlands in the west and northwest parts of the peninsula. The pre-Tertiary rocks that comprise most of the mountainous part of the peninsula are intricately folded whereas the Tertiary rocks, which occupy the low areas of the peninsula, are either horizontal or only gently warped into folds in which dips are generally less than 10° (Barnes and Cobb, 1959, p. 227).

The lode deposits of the Moose Pass-Hope camp consist of fissure veins. Mineralized acidic dikes are also in the district, but the gold production has been from the fissure veins that cut across the slaty cleavage of the slate and graywacke country rocks. The veins strike in all directions and have an average dip of 45° north or west (Tuck, 1933, p. 490). The ore minerals are arsenopyrite and small amounts of galena, sphalerite, pyrite, and chalcopyrite in a gangue of quartz, calcite, and ankerite (Tuck, 1933, p. 491). Free gold occurs in the quartz, commonly near accumulations of galena and sphalerite.

The placer deposits of the Kenai Peninsula, described by Martin, Johnson, and Grant (1915, p. 181-208), are most productive in the northern part of the peninsula along the various streams - Crow, Resurrection, Palmer, Bear, and Sixmile Creeks - that debouch into Turnagain Arm. Farther south, the gravels of Canyon, Mills, Falls, and Cooper Creeks, and of the Kenai River have yielded some placer gold. The deposits were formed in Quaternary time by postglacial streams reworking and resorting the debris that choked the valleys after the retreat of the glaciers. Present streams that have incised their courses in the unconsolidated material have left terraces and have further reworked the gravels. The productive placers are along these streams and in channel deposits in the terraces.

VALDEZ CREEK DISTRICT

The Valdez Creek district is on the southern flank of the Alaska Range at approximately lat 63°12' N. and long 147°20' W. The drainage area of Clearwater Creek in addition to that of Valdez Creek is usually included in the district.

Gold was first discovered in this district in 1903, in the gravels of Valdez Creek, but no production was recorded until 1908. The "Tammany Channel," a buried channel representing the course of an ancestral Valdez Creek, yielded most of the placer gold from the district. This channel, discovered in 1904, has been worked by hydraulic and underground methods (Tuck, 1938, p. 113). The chief production has been from placers. Several gold lodes were located, but none were productive to 1936 (Tuck, 1938, p. 121), and no record of any later lode production was found in 1959.

Total estimated gold production through 1936 was about 34,900 ounces, worth about $720,000 (Tuck, 1938, p. 113). The district was virtually dormant during 1937-59.

The geology of the district was described in detail by Ross (1933b, p. 428-444). Triassic(?) metasedimentary rocks - argillite, slate, and sericite and chlorite schist with limestone lenses - were intruded by a small batholith of quartz diorite in the northern part of the district and by small stocks and plugs of diorite elsewhere in the district. Structurally, the district is on the northwest flank of a large northeast-trending anticlinal fold; large normal faults trending N. 65° E. cut the metasedimentary rocks.

There are several types of veins in the district, and those showing the most promise, according to Ross (1933b, p. 456), are quartz veins associated with sheared and metamorphosed wallrocks. In their unoxidized state these veins contain pyrite, arsenopyrite, pyrrhotite, and a little chalcopyrite. Native gold occurs in the quartz. Some quartz veins contain abundant calcite (Ross, 1933b, p. 457). Ross (1933b, p. 458) believed the veins were related to hydrothermal activity that followed the intrusion of the dioritic bodies.

The placers are buried channels in which gold was concentrated next to the bedrock floor. The old gorges, eroded into bedrock, are V-shaped and probably were cut into a mature erosion surface (Ross, 1933b, p. 444-445).

WILLOW CREEK DISTRICT

The Willow Creek district, an area of about 50 square miles, is 23 miles by road northeast of Wasilla and 21 miles northwest of Palmer.

Gold-bearing veins were discovered in this district in 1906, but lack of transportation facilities hindered their development and no production was recorded until 1909 (Ray, 1954, p. 35-36). After 1909 the district developed steadily and maintained substantial annual production until 1951, after which there was only sporadic small-scale activity. Total gold production through 1959 was 652,080 ounces; nearly all production was from lode mines.

The geology and ore deposits of this district were described by Ray (1954, p. 10-54). The oldest rock is muscovite-quartz-plagioclase schist. Intruded into this is a mass of quartz diorite, the Talkeetna batholith, which underlies the major part of the district. Dikes of lamprophyre, diabase, aplite, and pegmatite cut the intrusive. The batholith is believed to be of late Mesozoic age. Sedimentary rocks, including conglomerate, arkose, shale, and sandstone of Tertiary(?) age, dip to the south, away from the quartz diorite body. Numerous faults cut the quartz diorite. Those with the larger displacements are postore in age, trend northwest, and dip northeast.

Two types of veins are in the quartz diorite (1) an older nonproductive group, containing assemblages of chalcopyrite-molybdenite, pyrite-stibnite, or low-grade gold-quartz, and (2) minable gold-bearing quartz bodies in shear zones that occur along the southern margin of the quartz diorite. Vein minerals, in addition to quartz and gold, are pyrite, arsenopyrite, sphalerite, chalcopyrite, tetrahedrite, nagyagite, altaite, coloradoite(?), galena, stibnite(?), and sparse scheelite. Gold commonly occurs as irregular grains in and around nagyagite and as fracture fillings in pyrite, and locally occurs as blebs and stringers in quartz.

YENTNA-CACHE CREEK DISTRICT

The Yentna-Cache Creek district includes about 2,000 square miles on the southeast slope of the Alaska Range and is located roughly between lat 61°55' and 62°45' N. and long 150°25' and 151°5' W. It includes the upper drainage of the Yentna River and its tributaries, the best known of which, from the standpoint of gold mining, are Cache, Mills, Peters, and Long Creeks.

Gold was discovered in this district in 1905 in gravels in the basins of Peters and Cache Creeks. During the first few years most of the production was from these placers. In 1911 additional placers were discovered on Dollar Creek and a few years later on Thunder Creek and Upper Willow Creek (Capps, 1925, p. 54-55). The district, although not a tremendous producer, had a steady output, entirely from placers, and was active through 1957. From 1905 through 1959, about 115,200 ounces was recorded; data for 1931-46 are not available.

The geology and placer deposits were described by Capps (1913; 1925, p. 53-61). Intensely folded slates and graywackes of Mesozoic age compose most of the bedrock. Masses of granitic and dioritic rocks were intruded into the metasedimentary rocks, and Capps believed that the numerous gold-bearing quartz veins in the slates and graywackes were derived from solutions emanating from the cooling intrusives. Poorly consolidated lignitic sand and clay of Oligocene age (MacNeil and others, 1961, p. 1904) unconformably overlie the folded older rocks. The sand and clay are overlain by younger Tertiary gravels.

The placers were derived by weathering and erosion of the auriferous veins in the metasedimentary rocks, first by Tertiary streams which deposited the gold in channels in the Tertiary gravels, then by postglacial streams which reworked the glacial debris and Tertiary deposits and concentrated gold from these earlier deposits into placers in the present stream channels. Minable placers occur in the Tertiary deposits as well as in the Recent gravels.