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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.

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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.

Alaska Gold Production 1880-1965
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.

COPPER RIVER REGION

The elliptical-shaped Copper River region, which includes a large part of the drainage basin of the Copper River, is in southern Alaska, bounded by the Alaska Range on the north, the Chugach Mountains on the southwest, and the Wrangell Mountains on the northeast. The region lies roughly between lat 61°00' and 63° 10' N. and long 142°00' and 146°00' W., and it includes the major gold districts of Chistochina and Nizina.

Gold mining began in this region in 1900 in the Chistochina district, but prospectors were active in the Copper River country as early as 1898 (Schrader, 1900, p. 421). The first locations were in auriferous gravels along the Chisna, one of the main tributaries of the Chistochina River. Productive placers were discovered along the upper part of the Nizina River and its tributaries in 1902 (Mendenhall, 1905, p. 118). Minor discoveries were made elsewhere in the Copper River region about this time, and in 1914 the Nelchina placers were discovered (Chapin, 1918, p. 59)—but the bulk of the gold production came from the placers of Chistochina and Nizina. In the Copper River region, especially the Chitina district, copper deposits were worked extensively by the Kennecott Co. during 1900-38 (Moffit, 1946, p. 93), but they yielded little gold.

From 1900 to 1959 the Copper River region produced 2,400 ounces of lode gold, 295,000 ounces of placer gold, and 5,600 ounces of gold undifferentiated as to source - a total of 303,000 ounces. From World War II through 1959 only a few hundred ounces per year were produced.

The geology of the region is summarized here from a more detailed account by Moffit (1938, p. 19-107).

Throughout most of the region the low-lying areas are blanketed by glacial sands and gravels of Quaternary age. In the higher areas, a thick succession of bedded rocks range in age from early Carboniferous to Recent. The oldest rocks consist of schist and slate associated locally with altered limestone, tuff, and basalt flows, and they include the Mississippian Strelna Formation and Dadina Schist and the Carboniferous or older Klutina Series. Overlying these rocks are layers of lava flows, tuff, volcanic breccia, shale, limestone, sandstone, and conglomerate of Permian age; these are overlain by the Nikolai Greenstone, a thick sequence of basaltic lava flows of Permian and Triassic (?) age.

The post-Triassic Mesozoic rocks in the Copper River region are not fully understood because of the correlation problems imposed by variable lithology, exposures in disconnected areas, and lack of diagnostic fossils. Tuffaceous beds of Middle Jurassic age occupy a small area near the mouth of the Chitina River. Upper Jurassic rocks occur in a few places in the central part of the Copper River basin along the north tributaries of the Chitina River. Along the north side of Chitina River valley a thick series of bedded sedimentary rocks of varied lithology is Jurassic or Cretaceous in age. Black shale and sandstone, conglomerate, and sandy shale considered to be of Early Cretaceous age overlie Triassic rocks in the Nizina district. The Chugach Mountains, in the southern part of the region, are underlain by dark slate and graywacke considered to be Cretaceous or older(?). These are equivalent to the Valdez and Orca Groups of earlier reports. The Tertiary rocks are dominantly of volcanic origin and include several thousand feet of lavas and tuffs interbedded with fresh-water conglomerate, clay, sandstone, and shale. These rocks compose the higher parts of the Wrangell Mountains.

CHISTOCHINA DISTRICT

The Chistochina district is in the northwest part of the Copper River basin near the intersection of lat 63°00' N. and long 145°00' W. The drainage area of the Chistochina River, including the southern foothills of the Alaska Range, roughly determines the boundaries of this district.

The initial gold discoveries of the Copper River region were made in this district along the Chisna River in 1898 by Hazelet and Meals (Moffit, 1944, p. 27). Slate Creek and Miller Gulch later became the leading gold-producing areas. Production from this district began in 1900 and continued, though at a diminishing rate in the later years, to 1942. From 1942 to 1959 the district was almost dormant, with only sporadic small-scale activity. Total production from 1900 through 1959 was about 141,000 ounces, all from placers. Production data from 1931 through 1945 are not complete.

Bedrock in the district consists of Carboniferous and Permian clastic and sedimentary rocks - predominantly shale, limestone, conglomerate and some sandstone - and subordinate volcanic tuffs and lava flows. All the foregoing rocks are cut by dikes (Moffit, 1944, p. 28). The gold placers were formed by reworking of glacial debris and occur in bench gravels as well as present stream gravels.

NIZINA DISTRICT

The Nizina district is in the eastern part of the Copper River drainage basin between lat 61°12' and 61°37' N. and long 142°22' and 143°00' W. This is a placer district along the Nizina River, a tributary of the Chitina River.

In 1898-99 prospectors were active in the Chitina River valley and some went up as far as the Nizina area. Although copper deposits were soon found and quickly developed, it was not until 1902 that placers rich enough to precipitate a rush were found on Chititu Creek (Moffit and Capps, 1911, p. 76). The rich deposits were quickly exhausted and the operators who remained developed previously known lower grade gravels on Chititu and Dan Creeks. In 1959 these gravels were still being mined, although on a smaller scale. Total production through 1959 from the Nizina district was 143,500 ounces of gold; all but about 60 ounces was from the placers.

The geology of the Nizina district was described by Moffit and Capps (1911, p. 20-75). Bedrock in the mountain areas consists for the most part of moderately folded Permian and Triassic(?) marine sediments and greenstone intruded by laccoliths, dikes, and sills of quartz diorite porphyry (E. H. Cobb, written commun., 1962). Deposits of morraine and alluvium blanket the lower slopes of the mountains and fill the river basins. The source of the gold in the placers is probably the small quartz veinlets in the black shales that may be related to porphyritic intrusives in the shales. High bench gravels, remnants of a deep alluvial valley fill, contain workable deposits, but the richest placers are in present stream gravels where the gold has been concentrated by reworking of older deposits (Moffit and Capps, 1911, p. 98-100).

SEWARD PENINSULA REGION

The gold placers of the Seward Peninsula, in western Alaska, rank second in production among Alaska's placer regions. The following description of its mining history has been abstracted from an excellent and detailed account by Collier, Hess, Smith, and Brooks (1908, p. 13-39).

Placer gold was discovered on Seward Peninsula in 1855-56 by Baron Otto von Bendeleben, an engineer leading a party exploring a possible route for a telegraph line. Nothing, apparently, came of this discovery, for as late as 1897 the Seward Peninsula was regarded as a wasteland. But about this time the rushes to the Klondike and the upper Yukon brought in many gold seekers who eventually prospected the lowly regarded gravels along the streams of Seward Peninsula. Discoveries were made at Council in 1897, and in 1898 the Nome district was organized. News spread slowly because of the isolation of this new district, but by 1899 the rush had begun and, swelled by new discoveries of beach placers and auriferous bench gravels, it continued through 1900.

In 1900, mining of placers began in the Fairhaven district in the northeastern part of the peninsula, and small production was made from discoveries in the Kougarok, Port Clarence, and Council districts. The Solomon-Bluff district, along the southern coast just east of Nome, also began producing placer gold in 1900, and from 1903 to 1907 lode gold was mined from the Big Hurrah mine in this district. During 1908-59 only very minor amounts of lode gold were produced from scattered localities on the peninsula.

The Koyuk district was not productive until 1918 even though for some years gold had been known in the gravels of the Koyuk River and Alameda Creek, one of its tributaries.

Through the 1950's placer mining continued to flourish on the Seward Peninsula, although at a somewhat lower rate than before World War II. The Nome district has been by far the largest producer; Council, Fairhaven, Solomon-Bluff, Kougarok, Koyuk, and Port Clarence have produced progressively lesser amounts. Total gold production of the Seward Peninsula from 1897 through 1959 was 6,060,000 ounces; all but about 10,000 ounces was from placers.

The geology of the Seward Peninsula was described by Collier (in Collier and others, 1908, p. 60-110). The peninsula is underlain chiefly by metasedimentary rocks comprising the Kigluaik and Nome Groups of early Paleozoic or older age and by unnamed slates, phyllites, and limestones some of which may be as young as Mississippian. Collectively these rocks can be considered a sequence of limestone, biotite gneiss, slate, quartzite, dark phyllite, and schist, cut locally by small bodies of greenstone and granite. Basalt of Pleistocene age covers a sizable area in the northeast part of the peninsula. Quaternary gravels blanket the low-lying coastal areas and occur in all the major stream valleys.

COUNCIL DISTRICT

The Council district, in the southern part of the Seward Peninsula, includes all the drainage area of Golovnin Bay extending eastward almost to the Tubutulik River.

Although gold had been reported in the Council area as early as 1865, there was very little excitement and no mining until after the discoveries of the rich Ophir Creek gravels in 1896-97 (Smith and Eakin, 1910, p. 343). Production began in 1900, and the district was still active in 1959. Total production through 1959 was about 588,000 ounces, all from placers. Data for 1931-46 are incomplete.

Nearly all production came from creek gravels and bench deposits in the drainage basin of the Niukluk River—including Ophir, Melsing, Goldbot-tom, Mystery, and Elkhorn Creeks (Collier and others, 1908, p. 238). The following summary of the geology is from Collier, Hess, Smith, and Brooks (1908, p. 234-235).

The district is underlain by rocks of the Kigluaik Group and the Nome Group, except in the southeast where part of a large granite mass forms the bedrock. Schists of the Nome Group contain numerous small veins and stringers of quartz and calcite, many of which contain gold along with sulfides. The gold of the placers is believed to have come from these veins.

FAIRHAVEN DISTRICT

The Fairhaven district, about 40 miles long and 20 miles wide immediately south of Kotzebue Sound in the northeast part of Seward Peninsula, is bounded roughly by lat 65°40' and 66°10' N. and long 161°40' and 163°20' W.

Gold was discovered in this district in 1900 on Old Glory and Hannum Creeks, and although there was no production that year, the news of the discovery spread through crowded Nome that winter and prompted a rush to the new district in the spring of 1901 (Moffit, 1905, p. 49). Rich placers, the most productive in the district, were found along Candle Creek in 1901 (Moffit, 1905, p. 49). The district produced steadily and was still active in 1957. Total recorded production through 1959 (data are incomplete for 1931-36) was 379,200 ounces, all from placers.

The predominant bedrock in the district is a series of micaceous, chloritic, and graphitic schists with intercalated thin limestones believed by Collier (in Collier and others, 1908, p. 65) to be Devonian or Silurian in age. Unaltered conglomerate, sandstone, and shale unconformably overlie the schists in a few areas. Locally coal beds are present. Small bodies of granite and quartz diorite intrude the schists, but their age relations with the unaltered sedimentary rocks are not clear (Collier and others, 1908, p. 83, 108). Large areas of the district are covered by sheets of basaltic lava, remnants of a more extensive cover. The youngest of these flows is Pleistocene; the age of the older lavas has not been satisfactorily determined (Moffit, 1905, p. 34). Low-lying coastal areas and river valleys are blanketed by unconsolidated gravels. The gold of the placers was concentrated from small amounts disseminated in quartz veinlets and stringers in the schistose country rock. These low-grade lodes have never been productive.

KOUGAROK DISTRICT

The Kougarok district is in the central part of the Seward Peninsula between lat 65°10' and 65° 45' N. and long 164°20' and 165°20' W.

The district began producing gold in 1900, after the initial discoveries the previous year sparked a rush from Nome (Brooks, in Collier and others, 1908, p. 306-307). Because of its remoteness and its paucity of bonanza-type deposits, the district developed slowly. Water shortage necessitated the construction of ditches. By 1906 several ditches were completed and sufficient water for larger scale operations was assured. Afterward, the Kougarok placers were moderately productive and were active in 1957. A total of about 150,400 ounces of gold has been produced from the district, all from placers. This is a minimum total as data for 1931-46 are incomplete.

The geology of the district was discussed by Brooks (in Collier and others, 1908, p. 297-298) and is summarized as follows. The bedrock consists of the Kigluaik and Nome Groups - the former is predominantly schist and granite; the latter is made up of a sequence of phyllite, schist, greenstone, and a consistent unit, the Port Clarence Limestone. The schistose rocks of the Nome Group contain small auriferous quartz veinlets and stringers which appear to be the source of the placer gold that has been concentrated into minable quantities in present stream gravels, bench gravels, and flood-plain gravels. The lodes themselves are not of economic value.

PORT CLARENCE DISTRICT

The Port Clarence district, an area of about 2,000 square miles on the west end of the Seward Peninsula, has produced small amounts of placer gold from the Bluestone and Agiapuk River basins and from a few streams that drain into Grantley Harbor. The district was prospected as early as 1898, and by 1903 an estimated $200,000 in gold had been produced (Collier and others, 1908, p. 269). Total recorded production through 1959 is about 28,000 ounces, all from placers, but 1931-46 production is not recorded. Since World War II there has been only small-scale activity.

The district is underlain by schist, limestone, and small intrusive bodies comprising the Kigluaik and Nome Groups of early Paleozoic or older age, and by Devonian (?) slate and Carboniferous (?) limestone. Stocks and dikes of granite and greenstone intrude the metasedimentary rocks. Quaternary gravels contain gold placers which are restricted in general to areas underlain by rocks of the Nome Group. These rocks seem to contain more auriferous veinlets and stringers than the other bedrock types. The foregoing account is from Collier, Hess, Smith, and Brooks (1908, p. 268-281).

SOLOMON-BLUFF DISTRICT

The camps of Bluff and Solomon, an area enclosed by lat 64°30' to 65°00' N. and long 163°30' to 164°30' W., are combined here.

Gold was first discovered in this district in 1898 in gravels along the Casadepaga River, a tributary of the Solomon River. The following year other placers were found along the Solomon and on the beach of the mouth of Daniels Creek in the Bluff camp (Brooks, in Collier and others, 1908, p. 288). The beach placers were exhausted in about a year, but more extensive placers were found along Daniels Creek and along Hurrah and Shovel Creeks in the Solomon camp. These were worked by dredges and hydraulic methods (Smith, 1910, p. 139). The only important gold-quartz mine on the Seward Peninsula was the Big Hurrah in the Solomon camp, which was active from 1900 to 1937.

A total of 251,000 ounces of placer gold has come from the Solomon-Bluff district not including production from 1931 to 1946 for which records have not been found. Lode production was 9,375 ounces; all was presumably from the Big Hurrah mine. Total production recorded for the district is 260,375 ounces. No production was recorded from 1937 through 1959.

The district is underlain by rocks belonging to the lower part of the Nome Group of early Paleozoic or older age. These are a series of schist, slate, and limestone. The metasedimentary rocks were intruded by basic igneous rocks, were later altered to schist and greenstone, and were finally intruded by basalt (Smith, 1910, p. 49-137). Unconsolidated deposits consist of coastal plain deposits, stream gravels, and high-level gravels.

The lode deposit at the Big Hurrah mine consists of several quartz veins in a dense, hard, quartzitic, graphitic schist. There is a noticeable absence of sulfides; the minerals consist almost exclusively of native gold in quartz (Smith, 1910, p. 144).

The gold in the placers, which consist of stream and beach gravels in the Bluff area and stream and bench gravels in the Solomon area, was derived from disseminations and veinlets in rocks of the Nome Group, particularly in the schist and in the vicinity of schist-limestone contacts (Smith, 1910, p. 214-216).

YUKON REGION

The vast Yukon region encompasses the entire drainage basin of the Yukon River in Alaska. It has the shape of a truncated wedge extending across central Alaska. The region is narrower (80 to 100 miles wide) along the west coast of Alaska at the mouth of the river and wider (200 to 300 miles) along Alaska's eastern border, where it includes the basins of the Yukon and one of its main tributaries, the Tanana. This has been by far the most productive of all the gold-producing regions, with a recorded total through 1959 of 12,282,250 ounces, most of it from placers.

Goodrich's detailed account (in Spurr and Goodrich, 1898, p. 103-131) of the early explorations, the discovery of gold, and the development of the first mining districts is the source of much of the material presented here.

The Yukon region had been traversed rather thoroughly after the 1840's by explorers and traders intent on establishing new posts and opening new country for the fur trade. A lively competition which developed among the Russians, the Hudson Bay Co., and the Americans was terminated by the purchase of Alaska by the United States.

In the 1860's small quantities of gold had been found at several localities in the Yukon basin, but credit for the discovery that led to intensive prospecting goes to George Holt, who made several trips to the Yukon in the 1870's and returned with glowing, if not entirely veracious, tales of gold in the interior. In 1881 a few prospectors panned some gold along the Big Salmon River, one of the tributaries of the Yukon River in the Yukon Territory, Canada. A year later, prospectors working up the Yukon from its mouth found gold in considerable quantities near what is now Rampart, in central Alaska. Discoveries in the 1880's along the boundary between Alaska and Canada in the Fortymile River area were developed rapidly, and by 1893 more than 300 men were working the gravels. Birch Creek in the Circle district next attracted attention and it soon rivaled the Fortymile district. Between 1890 and 1895 gold-bearing gravels were found along the Koyukuk River and additional discoveries were made in the Rampart area and in the adjacent Hot Springs district.

In 1902 gold was discovered in the Fairbanks district (Prindle, 1904, p. 64) which in the succeeding years developed into the leading producer in Alaska. The Fairbanks discoveries stimulated prospecting to the south in the foothills of the Alaska Range, and placers were found in the Bonnifield country in 1903 and the Kantishna district in 1906 (Prindle, 1907, p. 205).

At about the same time, commercial quantities of gold were found several hundred miles to the west in the gravels of the upper valley of the Innoko River and this led to discoveries on the adjacent Iditarod River. In about 1910 placers were found along Long Creek in the Ruby district, about 70 miles east of Koyukuk (Mertie and Harrington, 1924, p. 88, 89, 101). One of the most recently discovered placer districts in the Yukon region is the Tolovana district situated along the Tolovana River, a tributary which joins the Tanana River about 100 miles west of Fairbanks. Mining of these placers began in 1915 (Brooks, 1916, p. 201).

Most of the placer districts of the Yukon, basin remained active after World War II,, through 1959, though production decreased because of the constantly rising mining costs especially since 1950.

Only two districts - Fairbanks and Nabesna - have had any significant lode production, but this is dwarfed by the placer output. The Yukon basin has yielded a total of 12,282,250 ounces of gold, of which 10,776,460 ounces is from placers, 305,560 ounces is from lode deposits, and 1,200,230 ounces is undifferentiated but presumably from placers. It may seem strange that from such a large region so few commercial vein deposits have been exploited; however, several factors must be considered in an analysis of this imbalance. First, the placers are amenable to large-scale dredging methods which means that low-grade material can be mined even at present high costs. Secondly, the remoteness of the areas containing the lode deposits demands large tonnages of high-grade ores for profitable mining.

It is difficult to summarize the geology of a region as large as the Yukon drainage basin, especially in view of the fact that the region has not been completely mapped and the areas that are mapped were done at different scales at different times and by numerous individuals. The upper part of the basin, the Yukon-Tanana area, was mapped first by Spurr (in Spurr and Goodrich, 1898) and then by Mertie (1937), but that part of the basin from the junction of the Yukon and Tanana to the mouth of the Yukon has been mapped in small parcels by individuals investigating only certain districts.

In the upper part of the basin, stratified rocks ranging in age from Precambrian to Recent are exposed. Representatives of every period except Jurassic are present (Mertie, 1937, p. 44-46). Mesozoic and Tertiary granitic intrusive rocks are the most important members of the igneous family in this area, and it is believed that the metalliferous ore deposits are related to them (Mertie, 1937, p. 46).

Farther downstream, in the Ruby area, greenstones and undifferentiated metamorphic rocks of Paleozoic age and older are the predominant country rocks (Mertie and Harrington, 1924, p. 12). In the Innoko and Iditarod districts, which may be considered the lower reaches of the Yukon, Mesozoic sedimentary rocks, chiefly Cretaceous in age, compose most of the country rock. These are inter-layered locally with basic igneous rocks. Granitic intrusions make up the mountain areas, and rhyo-lite dikes are scattered throughout the areas (Eakin, 1913, p. 295).

Throughout the Yukon basing large areas are covered with fluvial deposits that form flats tens of miles wide. The entire region has a complex geomorphic and structural history, much of which is fairly recent in age, but not enough work has been done in the region to interpret the many anomalous features of the present drainage (Mertie, 1937, p. 237).

BONNIFIELD DISTRICT

The Bonnifield district is between lat 63°30' and 64°50' N. and long 145°40' and 149°20' W. It extends from the Tanana flats on the north to the north slope of the Alaska Range on the south, and it is bounded on the west and east by the Nenana and Delta Rivers, respectively.

The first gold was mined from the gravels of Gold King Creek in 1903. During the early years there were high hopes that the Bonnifield would become a major district, but only small amounts of gold were produced annually, and after 1949 the district was idle. Total production through 1959 was about 36,600 ounces, all from placers.

The geology, as outlined by Capps (1912, p. 17-19), is as follows. The oldest rocks in the district are metasedimentary rocks of Precambrian or early Paleozoic age - the Birch Creek Schist, consisting of quartz and mica schist, phyllite, and quartzite. Mertie (1937, p. 46) considered the Birch Creek to be Precambrian in age. The Birch Creek Schist is overlain by quartz-feldspar schists forming the Totatlanika Schist of Silurian or Devonian age. A sequence of Tertiary sediments beginning with Eocene fresh-water deposits unconformably overlies the schists. The freshwater deposits are followed by the Nenana Gravel of middle Miocene to early Pliocene age (MacNeil and others, 1961, p. 1806) and Pleistocene and Recent glaciofluvial deposits. The schists are highly contorted, and as the Alaska Range rose in Tertiary time the Tertiary beds were subjected to considerable folding and faulting immediately after their deposition. Intrusive rocks of granitic to dioritic composition cut the schists at various localities. These bodies are older than Eocene and younger than Silurian or Devonian (Capps, 1912, p. 41-42).

The placer deposits are in the foothills between the Tanana Flats to the north and the high slopes of the Alaska Range to the south. Present streams have cut through valleys previously filled with alluvium and have reconcentrated and redeposited the detrital gold of the older alluvium.

CHANDALAR DISTRICT

The Chandalar district, between lat 67°00' and 68°10' N. and long 147°00' and 150°00' W., includes the upper drainage of the Chandalar River.

The Chandalar district, which began producing placer gold in 1906, is one of the small producers of the Yukon basin. Total placer production through 1959 was 30,708 ounces. Cobb (1962) indicated small but undisclosed lode production from the district. Lode deposits, which have been known in the district for many years, have recently received renewed attention. In 1961 the Little Squaw Mining Co. reported blocking out an ore body worth $1,013,000 in gold (Mining World, 1961).

The geology given here is generalized from a more detailed account by Mertie (1925, p. 223-252). Schists, resembling the Birch Creek Schist, of Precambrian or early Paleozoic age are the oldest rocks in the district and are found in the southern part. Other schists and phyllites of early Paleozoic age compose the bedrock in the central part of the district, north of the area underlain by Birch Creek (?) Schist. Silurian limestone and dolomite and Devonian slate occur still farther north. In the southwest corner, Devonian or Mississippian rocks unconformably overlie the schists, and a small patch of Upper Cretaceous sandstone caps the sequence. Igneous rocks in the district consist of granite, granodiorite, and basic lavas, that range in age from Late Silurian or Early Devonian to Tertiary.

The schists contain numerous small auriferous quartz veins and stringers that no doubt were the source of the gold in the placers. Both preglacial and postglacial gravels have been productive.

CHISANA DISTRICT

The Chisana district is between lat 61° 55' and 62°20' N. and long 141°40' and 142°35' W., in the drainage area of the Chisana River, a tributary of the Tanana River.

Gold lodes were known in this area before 1910, but were never developed; then in 1913 placer discoveries along Bonanza Creek started a stampede to the district (Capps, 1916, p. 89-92). The placers, however, were relatively small, and efforts to find and develop lode deposits were unsuccessful. Small amounts of placer gold were produced up to World War II, but since then the output has been insignificant. Total production from 1913 through 1959 was 44,760 ounces, all from placers.

The rocks of the district range in age from Devonian to Recent (Capps, 1916, p. 29-31). The oldest rocks are black shale, basic lava, and pyroclastic of Devonian age which are overlain by a great thickness of Carboniferous lava, tuff, breccia, agglomerate, and some limestone and shale. Shale and graywacke of Mesozoic age are faulted against the older rocks along an east-west line. Several small patches of Tertiary sediments unconformably overlie the Paleozoic rocks, and in the stream valleys considerable areas are covered with glacial debris and stream deposits interbedded with lava flows. Granitic intrusions cut the Devonian and Carboniferous rocks but the exact age of the igneous rocks is not known (Capps, 1916, p. 84-85).

Most of the placers occur in the area of Carboniferous pyroclastic rocks and the granitic intrusions. Capps (1916, p. 96-98) believed that the gold of the placers was eroded from veins in these Paleozoic rocks near their contact with the intrusives and that the present placers are a product of several previous reworkings of Tertiary auriferous gravels, first by streams, then by glaciers, then by the present streams reworking the glacial deposits.

CIRCLE DISTRICT

The Circle district is between lat 65° 15' and 66°00/ N. and long 144°00' and 146°00' W.

This is one of the older districts of the region, gold having been discovered along Birch Creek in 1893 (Prindle, 1906, p. 20). Production began the following year and was continuous through 1957. Hydraulic methods were used on nearly all productive streams, particularly along Mastodon Creek. Total production through 1959 was 705,660 ounces, all from placers.

The rocks, as summarized from Mertie (1932, p. 158-161), consist of schist, clastic sedimentary rock, limestone, and granitic rocks ranging in age from Precambrian to Mesozoic. Pleistocene and Recent unconsolidated deposits complete the sequence.

The Birch Creek Schist, the oldest rock, is of Precambrian or early Paleozoic age. Next youngest are lower Paleozoic metamorphic rocks—quartzite, phyllite, and slate—together with graywacke, arkose, limestone, and chert. The Crazy Mountains in the central part of the district are underlain in succession by Silurian or Devonian limestones, basic flows and sedimentary rocks of the Rampart Group of Early Mississippian age, and by a later Missis-sippian chert formation. Several small bodies of granite are intrusive into all the foregoing rocks, and the placer deposits are in the vicinity of the intrusive bodies. Alluvial deposits in the Circle district represent several erosional periods during Pleistocene and Recent time.

EAGLE DISTRICT

The Eagle district is between lat 64° 35' and 65° 15' N. and long 141°00' and 142°40' W., along Seventymile, American, and Fourth of July Creeks, all tributaries that enter the Yukon River near Alaska's eastern boundary.

Placer gold was first found in 1895 along American Creek, and production began the following year (Mertie, 1938, p. 190). Although it attracted few miners, the Eagle district maintained a small annual production even through the difficult post-World War II years. Production data before 1906 cannot be found and was probably reported under some other district. Total recorded production for the Eagle district from 1906 through 1959 is 40,220 ounces, all from placers.

The district is underlain in the southwest by a large mass of granite of Late Jurassic age that has intruded and thrust upward a series of Precambrian and Paleozoic sedimentary rocks that are now exposed in northwestward-trending bands in the central and northern parts of the district. Lower Cretaceous marine rocks are exposed in the northern part of the district and these are succeeded by a thick series of freshwater deposits of Late Cretaceous and Eocene age (Mertie, 1930, pi. 12). Post-Eocene uplift caused much of this covering to be removed. Unconsolidated deposits of sand and gravel of Pleistocene and Recent age are in the stream valleys. These sediments reflect a complex geomorphic cycle involving local glaciation, climatic changes, and changes in base level (Mertie, 1930, p. 147-148).

The gold placers are in present stream gravels. The gold in these deposits came originally from small veins related to the granitic mass in the southwest part of the area, but much gold also came from ancient placers in the Upper Cretaceous and Eocene elastics (Mertie, 1930, p. 161-162).

FAIRBANKS DISTRICT

The Fairbanks district, about 300 square miles between lat 64°40' and 65°20' N. and long 147°00' and 148° 10' W., has produced more gold than any other district in Alaska. It is predominantly a placer district, although it also ranks high among the lode districts.

Fairbanks was slow to develop. Placer gold was known in the area as early as 1878 (Mertie, 1937, p. 4), but the active districts of Fortymile, Rampart, and Circle kept all but the most restless away from the Fairbanks area. In 1901 the town of Fairbanks was founded as a trading post, not as a consequence of gold mining (Prindle and Katz, 1913, p. 86). The following year some workable placers were found along Pedro Creek. This discovery brought a rush of miners and prospectors to the district, most of whom became discouraged and left after learning that the rich, easily accessible placers were few and that the large, lower grade deposits were buried and required processing large volumes of material with special machinery. Large investments were needed to purchase and construct hoisting machinery, large dredges, and machinery for thawing the frozen overburden. But gradually, as the obstacles were overcome, it was found that the buried gravels could be mined profitably, and the district prospered as the dredges chewed through huge reserves of auriferous gravels on Dome, Ester, Vault, Cleary, and Chatanika Creeks. Production continued at a high level even after World War II, but in 1959, activity began to diminish. The Fairbanks Daily News-Miner reported (Sept. 15, 1959) that gold dredging was gradually ceasing in this area. Two dredges were closed in 1959 and a third was transferred to the Fortymile district.

Interest in lode mining began after the placers were developed. Small-scale operations were under way in 1910 in Skoogy Gulch and upper Cleary and Fairbanks Creeks (Hill, 1933, p. 51). The peak of lode mining was reached just before World War II. The Pedro Dome and Ester Dome areas contain the most productive lode deposits.

The total gold production of the Fairbanks district through 1959 was 7,464,167 ounces - 7,239,696 ounces from placers, 224,471 ounces from lodes.

The Birch Creek Schist, of Precambrian or early Paleozoic age, underlies most of the district (Hill, 1933, p. 41). This includes a variety of rock types, among which quartz schist and quartzite are dominant. Masses of crystalline limestone are present locally. Small bodies of biotite granite and quartz diorite believed to be of Mesozoic age (Hill, 1933, p. 43) intrude the Birch Creek. In the northeast corner of the district is a small patch of Tertiary sandstone and conglomerate, and in the same general area are a few small isolated areas of Tertiary basalt (Hill, 1933, p. 42-43).

The lode deposits of the Fairbanks district are fissure veins in the Birch Creek Schist in the vicinity of bodies of intrusive rock. The trends of both the veins and intrusives seem to be controlled structurally, but the trends are not consistent throughout the district (Hill, 1933, p. 63-64). All the major intrusives trend eastward; the veins in the Pedro Dome area also trend eastward, but the veins in the Ester Dome area trend more northward. The veins consist of quartz with small amounts of the sulfides arsenopyrite, pyrite, sphalerite, jamesonite, and stibnite, and free gold which is associated either with quartz or with the sulfides. Cervantite is widespread as an oxidation product of stibnite, and its yellow-green stain is a guide to high-grade gold ore in this district (Hill, 1933, p. 64-73).

The gold placers occur along stream valleys in unconsolidated gravels. The most productive layer is normally a few inches to 8 feet above the bedrock ; the bedrock from 1 foot to several feet below the gravel is usually gold bearing. A thick mantle of barren material consisting of sands, clays, and muck covers the deposits (Prindle and Katz, 1913, p. 92-98).

FORTYMILE DISTRICT

The Fortymile district, between lat 64°00' and 64°30' N. and long 141°00' and 142°20' W., along the international boundary, includes the upper drainage of Fortymile River, one of the Yukon tributaries that joins the main stream in Canada. It is one of the oldest placer areas in the Yukon region and had uninterrupted output through 1959.

According to Mertie (1938, p. 157), gold was discovered in the district in 1886, but Smith (1933, p. 96) listed small production beginning in 1883. Discoveries of rich stream placers in 1893 in the Sixtymile River area, across the international boundary, drew many prospectors to the Fortymile district as well, and in a relatively short interval all the major gold-producing grounds in the Forty-mile district were found. The placers of Dome, Wade, and Chicken Creeks were all discovered during the 1890's (Mertie, 1938, p. 157). Large-scale mining methods—dredge and hydraulic—have been used with success, which is probably why the district was still active in 1959.

Total recorded gold production of the Fortymile district through 1959 was about 400,000 ounces, all from placers.

The most abundant country rock of the district, according to Mertie (1938, p. 148), is the Birch Creek Schist, but locally other rocks are present. In the Chicken Creek and Franklin Creek areas granite is exposed (Mertie, 1938, p. 171, 182). Small patches of Tertiary conglomerate, shale, and sandstone are known in the Chicken Creek and Napoleon Creek areas, and some lower Paleozoic greenstone and limestone is exposed along Napoleon Creek (Mertie, 1938, p. 184). Basalt, gabbro, and diabase, younger than the granite, are found in the central part of the Chicken Creek basin.

The productive deposits are in gravels of Pleistocene to Recent age. There are also ancient placers in the Tertiary deposits, but none of these contain gold in commercial quantities. On the other hand, these Tertiary deposits, where eroded, contributed their gold to the younger deposits. Quartz veins related to the granite intrusives are the ultimate source of the gold, according to Mertie (1938, p.154).

HOT SPRINGS DISTRICT

The Hot Springs district is between lat 65°00' and 65°20' N. and long 149°40' and 151°20' W. The drainages of Baker, Sullivan, and American Creeks are its major placer areas.

Gold-bearing gravels were discovered in 1898 on Baker and Eureka Creeks by a group of New Englanders known throughout the area as the "Boston Boys" (Mertie, 1934, p. 165-166). When the party returned in 1899 to the new settlement of Rampart, news of their discoveries leaked out and caused a rush to the Hot Springs area. The first production reported was in 1904 (Smith, 1933, table facing p. 96) ; a town was built a few years later (Mertie, 1934, p. 166).

The district maintained a steady output since mining began and was still active in 1959. Opencut, drifting, and hydraulic methods have been used in the mining. Total production through 1959 was 447,850 ounces, all from placers.

As the Hot Springs and Rampart districts are separated by only a narrow drainage divide, their geology can be summarized together.

Consolidated sedimentary rocks that range in age from pre-Ordovician to Tertiary and include sandstone, shale, conglomerate, chert, limestone, and coal-bearing rocks compose the bulk of the bedrock in these two districts (Mertie, 1934, p. 172-173). These are intruded locally by granite of Tertiary age.

Eakin (1915, p. 239) noted that the placers of the Hot Springs district were of several types - bench deposits, reworked bench deposits, irregular discontinuous bodies of auriferous gravel called "spots," and normal stream gravels containing pay streaks.

The gold of the placers was deposited during early and late Tertiary from lodes in and adjacent to granitic intrusives (Mertie, 1934, p. 223).

IDITAROD DISTRICT

The Iditarod district, between lat 62° 10' and 63°00' N. and long 157°30' and 158°30' W., along the upper drainage of the Iditarod River and its tributaries, ranks second among the gold-producing districts in the Yukon basin.

Gold was discovered in 1908 along Otter Creek, a tributary of the Iditarod River (Maddren, 1911, p. 238). Despite its remoteness, the district developed, and in 1910 production was reported at $500,000 (Smith, 1933, table facing p. 96). Productive gravels also were found on Flat and Willow Creeks. The placers have been mined by dredges, mechanical scrapers, and hydraulic equipment (Mertie and Harrington, 1924, p. 110). Total gold production through 1959 was 1,297,500 ounces; nearly all production was from placers.

The underlying bedrock of the district, as described by Mertie and Harrington (1924, p. 12-82), consists dominantly of sandstone, shale, and conglomerate of late Cretaceous and Eocene age. In the western part of the district, west of the Iditarod River, undifferentiated metamorphic rocks of Paleozoic and Precambrian age are exposed; in the central part there are a few small stocks of quartz monzonite and basic intrusives. Unconsolidated deposits of sand, gravel, and silt of Pleistocene and Recent age are in the stream valleys.

Placers are of two types - residual and stream (Mertie and Harrington, 1924, p. 111-115). The stocks of monzonite, which are sheared and mineralized, are the source of the gold for each type.

INNOKO DISTRICT

The Innoko district, in the upper drainage area of the Innoko River between lat 62°50' and 63°15' N. and long 156°10' and 156°50/ W., lies immediately northeast of the Iditarod River. The Beaver Mountains form the drainage divide between the Innoko and Iditarod Rivers.

Gold was discovered in the gravels of Ganes Creek in 1906, and despite its remoteness the new camp attracted permanent settlers (Maddren, 1911, p. 236) who began gold production in 1907 that continued uninterrupted through 1957. Most of the mining was in the Ophir, Spruce, Little, Ganes, and Yankee Creek areas (Maddren, 1911, p. 246). The Innoko is a placer district and through 1959 produced a total of 518,565 ounces of gold. Most of the placers are in the gravels of the present streams or in bench deposits.

Argillaceous beds of Late Cretaceous and Eocene age underlie most of the Innoko district, except for a small area in the northeastern part where several small bodies of quartz monzonite and basic intrusives cut the sedimentary rocks (Mertie and Harrington, 1924, p. 30, 62, 69, pi. 4).

KANTISHNA DISTRICT

The Kantishna district is an area of about 4,500 square miles, between lat 63°25' and 65°00' N. and long 149°00' and 151°10' W., that includes part of the Alaska Range foothills on the south and part of the Tanana lowlands on the north. It is bounded on the east by the Nenana River and on the west by the western tributaries of the Kantishna River.

The Tanana River valley became well populated by miners and prospectors during the early part of the Fairbanks rush, and soon the rich gravels in the Kantishna district were found. In 1904 gold was found along Toklat River and the following year a flood of hopeful gold seekers left Fairbanks for the new district (Capps, 1919, p. 75). Soon several thousand people swarmed into the area, nearly all streams were staked, and several towns were built. It soon became apparent that the deposits, though rich, were shallow and of small area, so that a dismal exodus began and the population of the district quickly dwindled to about 50 (Capps, 1919, p. 76). Those who remained were able to maintain small production from the placers, and the district was still active on that scale in 1957. In 1904-5 lode deposits of lead-silver and antimony were found, and in 1921 gold, copper, and mercury lode deposits were discovered. The antimony deposits were worked sporadically during 1936-55, but the other lode deposits never achieved any significance (Reed, 1961, p. 27-28).' Total gold production from the district from 1905 through 1957 was 45,925 ounces, all from placers. No activity was reported in 1958-59.

The oldest rock in the district is the Birch Creek Schist of Precambrian age (Wells, 1933a, p. 343). This schist is succeeded by younger schists, phyllites, and gneisses, composing the Totatlanika Schist of pre-Devonian age and the Tonzona Group of Devonian or Silurian age. Pre-Tertiary greenstone, Mesozoic limestone, a sequence of Tertiary fresh water sediments, tuffs, and flows, and Quaternary glacial, glaciofluvial, and fluvial deposits complete the sedimentary column in the district (Capps, 1919, p. 22-23). The pre-Tertiary and lower Tertiary rocks have been deformed into east-trending folds parallel to the axis of the Alaska Range to the south of the district (Capps, 1919, p. 22).

The productive placers of the district are along the streams that radiate outward from the higher parts of the Kantishna Hills. The gold was believed by Capps (1919, p. 79) to be derived from erosion of small quartz veins that cut the Birch Creek Schist.

KOYUKUK DISTRICT

The Koyukuk district, between lat 67°00' and 68°00' N. and long 149°00' and 150°50' W., drained by the north, middle, and south forks of Koyukuk River, is often considered to be one of the most northerly in the world.

Some time between 1885 and 1890 placer gold was first found in this district on the sand bars along the Koyukuk River. Maddren (1913a, p. 76) reported that by 1898 at least $4,000 in gold had been mined from them; however, Smith (1933, p. 96) did not report production from the Koyukuk district until 1900. Nearly all the upper reaches of the Koyukuk tributaries have been prospected, and the results have been rewarding. The district was still active in 1959, though only on a small scale. Total production from the district through 1959 was about 278,000 ounces, all from placers. Promising lode deposits of gold have not been found in this district.

The most abundant bedrock in the district is the ubiquitous Birch Creek Schist of Precambrian or early Paleozoic age. The schist is exposed in two belts - one in the southern part of the Endicott Mountains and the other in the Hodzana highland area, between the Yukon River and the Koyukuk valley. Numerous dikes and small intrusives of granitic composition, probably Mesozoic in age, cut the schist (Maddren, 1913a, p. 34-36). Exposed in the central and northern parts of the district are two sequences of Paleozoic rocks: one is of Devonian (?) age and consists of greenstone, slate, chert, and limestone; the other is a section of crystalline limestone and mica schist of Carboniferous (?) age. Underlying the western part of the district are Mesozoic sedimentary rocks represented by Cretaceous limestone and calcareous sandstone inter-bedded with basic flows and pyroclastics (Maddren, 1913a, p. 50-55).

Pleistocene gravel covers large areas in the district, including all the major stream valleys. Recent deposits include gravels along present stream courses.

The placer deposits are in present stream gravels and bench gravels; some of them are buried. Maddren (1913a, p. 83) considered that the gold in the placers was derived from the Birch Creek Schist. Auriferous pyrite occurs in carbonaceous phyllite facies and free gold is found in quartz veinlets and stringers that cut the micaceous quartz schist facies. The gold was transported by streams and glaciers and later concentrated by further stream action into the placer deposits.

MARSHALL DISTRICT

The Marshall district is between lat 61°40' and 62°00' N. and long 161°30' and 162°10' W., along the lower Yukon River.

During the early days, just after the discoveries at Nome, the port of St. Michael was the terminus and supply center for prospectors embarking on trips up the Yukon River or along the coastline of the Seward Peninsula. A portage to the upper Anvik River, one of the Yukon tributaries, greatly shortened the trip to the goldfields at Dawson and elsewhere on the upper Yukon by eliminating travel along several hundred miles of meanders on the lower Yukon River. Thus, except for a few itinerant prospectors and traders, the Marshall district was rather thinly settled and sparsely prospected.

In 1913, however, gold was discovered on Wilson Creek in the Marshall district (Harrington, 1918, p. 56). The usual rush followed. Additional placers were found on Willow Creek, and the first production was in 1914. Lode deposits were found in 1914, and a small shipment was made that same year (Harrington, 1918, p. 57). The quartz veins did not warrant extensive development; at any rate, lode production for the district is unrecorded.

After the first few years of near-bonanza placer production, activity slackened, was rejuvenated briefly in the late 1930's, then declined after World War II. In 1957 there was only small-scale activity in the Marshall district. Total recorded gold production through 1957 was 113,200 ounces, all from placers. The district was idle in 1958 and 1959.

Much of the bedrock in the Marshall district is greenstone and intercalated sedimentary rocks of Carboniferous age (Harrington, 1918, p. 22-26). These rocks are cut by several stocks and dikes of granite, quartz diorite, and dacite of possible Jurassic or Tertiary age (Harrington, 1918, p. 45-46). Cretaceous sandstone and argillite, somewhat metamorphosed, occur adjacent to the greenstone throughout much of the district. The most abundant rock type exposed in the district is the unconsolidated material deposited during Quaternary time by the debris-laden streams issuing from the huge glaciers of the interior of the Yukon River basin (Harrington, 1918, p. 36-44).

NABESNA DISTRICT

The Nabesna district is between lat 62° 10' and 62°30' N. and long 142°40' and 143°10' W.

Gold had been known in this district since 1899, but there was no significant production until 1931 when the first shipments were made from the Nabesna mine, the lone producer of the district. Credit for the discovery is given to a bear who exposed the moss-covered outcrop of the principal vein while digging out a gopher. The property was developed by C. F. Whithan, who formed the Nabesna Mining Co. in 1929 and began shipping ore in 1931 (Wayland, 1943, p. 176-177). By 1939, much of the vein was worked out and in 1940 production halted. Additional exploration and development work in the district apparently was unsuccessful for there has been no further production reported. In its brief history the Nabesna district produced about 63,300 ounces of gold, all from lodes.

The rocks in the vicinity of the mine consist of the Nabesna Limestone of Late Triassic age and basaltic lavas and shale of possible Permian age (Wayland, 1943, p. 177). A few small bodies of quartz diorite cut the limestone. The thick Wrangell Lava of Tertiary and Quaternary ages unconformably overlies these rocks. Moraine and fluvial sediments of Quaternary age are found in all the stream valleys.

The ore bodies are in contact-metamorphosed limestone near the largest of the quartz diorite intrusives (Wayland, 1943, p. 183-191). Ore deposits are of three types: bodies of magnetite with pyrite, calcite, and some gold; veins and bodies of pyrrhotite with minor pyrite and gold; and gold-bearing pyrite veins in tactite or along intrusive contacts. The third type is the most important and has accounted for most of the production of the Nabesna mine.

RAMPART DISTRICT

The Rampart district, between lat 65°15' and 65°40' N. and long 149°40' and 150°40' W., joins the Hot Springs district on the north.

Gold was discovered in the gravels of Minook Creek and Hess River and their tributaries in 1882, but for the succeeding 10 years nothing was done to develop the placers. In the early 1890's more discoveries were made and finally in 1896 the first mining was done on Little Minook Creek (Hess, in Prindle and Hess, 1906, p. 26). Smith (1933, table facing p. 96), however, does not report any production until 1904. The district reached its peak of activity before 1910; after that time, production decreased, and in the 1950's only a few hundred ounces per year were mined. Total gold production through 1959 was 86,800 ounces from placers. There are no workable lode deposits in the district.

The geology of the district, as summarized by Mertie (1934, p. 172-173), is chiefly the same as that of the Hot Springs district. Consolidated sedimentary rocks - which range in age from pre-Ordovician to Tertiary and include sandstone, shale, conglomerate, chert, limestone, and coal-bearing rocks —compose the bulk of the bedrock. These are intruded locally by granite of Tertiary age. The major placers are along Minook Creek and its tributaries and along Quail Creek, one of the tributaries of Troublesome Creek.

Several prominent stream terraces containing low-grade gold deposits occur along the Minook Creek valley, but most production has come from gravels at present stream levels along Little Minook Creek (Mertie, 1934, p. 181).

RUBY DISTRICT

The Ruby district is between lat 63°40' and 64° 45' N. and long 154°40' and 156°20' W.

The first discoveries of gold in this district were made in 1907 along Ruby Creek (Mertie, 1936, p. 144). These placers were soon exhausted, but other discoveries in 1910 along Long Creek and in 1912 along Poorman Creek kept the district flourishing (Mertie, 1936, p. 145, 159). Underground drifting, sluicing, and hydraulic methods have been used to mine the gravels. Although production decreased somewhat in recent years, the district was still producing substantially through 1959. Total gold production through 1959 was 389,100 ounces, all from placers.

Undifferentiated metamorphic rocks, including schist, phyllite, slate, quartzite, chert, and limestone, are mainly of Paleozoic age and are the predominant bedrock types in the Ruby district (Mertie and Harrington, 1924, p. 12). A complex of greenstone derived from basic igneous rocks, be¬lieved to be Mississippian in age (Mertie and Harrington, 1924, p. 59), is exposed throughout the district. A few granite stocks of Mesozoic(?) age intrude both the Paleozoic rock units. The generalized structure is an anticline trending northeast and plunging to the southwest.

Numerous quartz veins are in the country rocks; some undoubtedly contain gold and could be regarded as the source of the gold in the placers. The distribution of the placers, however, does not directly coincide with areas of abundant veins, so that no clear relationship is apparent (Mertie and Harrington, 1924, p. 121). Nearly all the placer deposits are buried discontinuous bodies that occur mostly in fairly wide valleys. They were formed by streams older than those now occupying the valleys (Mertie, 1936, p. 144).

RICHARDSON DISTRICT

The Richardson (or Tenderfoot) district is between lat 64° 15' and 64°25' N. and long 146°00' and 146°40' W., about 60 miles southeast of Fairbanks, along the Tanana River.

This is a little-known district, about which only a few brief accounts have been written. According to Prindle (in Prindle and Katz, 1913, p. 141) gold was discovered in the gravels of Tenderfoot Creek in 1905 and for the following 4 years the gold production was probably "$300,000 or $400,000 annually." Smith (1933, table facing p. 96), however, reported a much more conservative figure. Productive deposits also were found along Buckeye and Democrat Creeks. Activity declined after the initial boom period and in recent years the production, which is low, has been combined with that of the Fairbanks district. Total recorded production for the district through 1959 was 64,300 ounces, all from placers.

Prindle (in Prindle and Katz, 1913, p. 140-141) noted that the bedrock in the district is Birch Creek Schist of Precambrian age (Mertie, 1937, p. 46). Numerous small quartz veins, some of which carry gold and sulfides, occur in the schist. Just west of the district are some large granitic masses (Prindle, in Prindle and Katz, 1913, p. 140-141). The placers are along present streams in the area.

TOLOVANA DISTRICT

The Tolovana district is between lat 65° 20' and 65°45' N. and long 147°50' and 149°00' W. in the upper drainage of the Tolovana River, a tributary of the Tanana.

Brooks (1916, p. 201) reported that placer gold had been found in this area as early as 1892 but that no interest was aroused until 1914, when placers along Livengood Creek were discovered. Mining began in 1915 and was substantially increased the following year with the development of the deposits on Livengood Creek and others on Gertrude, Ruth, Lillian, and Olive Creeks (Mertie, 1918, p. 256). The district continued to prosper and it was still productive on a small scale in 1959. Total gold production through 1959 was 375,000 ounces, all from placers.

The bedrock in the Tolovana district is distributed in several bands or belts that cross the area in a northeasterly direction. The oldest rocks in the district crop out in the southeast; the rocks become successively younger in a northwesterly direction. Briefly, the bedrock units consist of the Tatalina Group, of Cambrian or Precambrian age, Devonian and Silurian (?) sedimentary and igneous rocks, a chert unit of Devonian or Carboniferous age, and Carboniferous arenaceous and argillaceous units (Mertie, 1918, p. 230-256).

Igneous rocks, chiefly basic, occupy a considerable area in the northwestern part of the district. Small bodies of granitic intrusives are scattered throughout most of the district. In the stream valleys, unconsolidated deposits of sand and gravel were deposited during several stages in the Quaternary geomorphic cycle. The earlier of these are only remnants and are seen as benches along the valley walls (Mertie, 1918, p. 230-231).

Gold placers in the district are in bench and stream deposits (Mertie, 1918, p. 259). The bench deposits have been the more productive. The gold in the placers of Tolovana was derived from low-grade lode deposits at the heads of many of the tributary streams (Mertie, 1918, p. 274-275).


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