By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Click here for the Principle Gold Producing Districts of the United States Index
Southeastern Alaska, the panhandle of Alaska, is the narrow coastal strip that extends southeastward from the main peninsula and is bordered on the north, east, and southeast by Canada. Important gold-producing districts in this region are Juneau, Chichagof, Ketchikan-Hyder, and Porcupine. For the purpose of this report, the Yakataga district, which lies just to the northeast of what is usually considered to be the Southeastern Alaska region, is included in this section.
Gold was known in this region in the days of Russian ownership of Alaska, but no mining was done until 1870-71 when about $40,000 was produced from placers at Windham Bay and on nearby Powers Creek at Sumdum Bay in the Juneau district (Buddington and Chapin, 1929, p. 8). The important discoveries in the Juneau district were not made until the period 1880-85. During the 1890's and early 1900's lode gold mines began significant production in the Ketchikan and Chichagof districts, and beach placers were mined in the Yakataga district.
The Alaska Juneau mine in the Juneau district yielded the bulk of the gold produced in the Southeastern Alaska region. When this mine closed in 1944, the production of the entire region dropped accordingly to only a few hundred ounces annually.
Total gold production through 1959 for Southeastern Alaska was 7,788,514 ounces, of which 7,614,791 ounces was from lode deposits, 138,503 ounces was from placers, and 35,220 ounces was a byproduct from copper ores from the Ketchikan-Hyder district.
This is an extremely mountainous region with complex geologic structures and varied bedrock types. Dominant among the geologic features are the intrusive rocks of Late Jurassic or Early Cretaceous age that occupy much of the mainland area of this region. These rocks range in composition from gabbro to granite and are believed to be related to the great composite Coast Range batholith (Buddington and Chapin, 1929, p. 173-253). Adjacent to the intrusive rocks on the west is a belt of low-rank metasedimentary rocks comprising the Wales Group of early Paleozoic age. Other sedimentary rocks in this region represent every period from Ordovician to Cretaceous and have an aggregate thickness of about 50,000 feet. Tertiary clastic rocks and lavas accumulated in a trough between the major mountain ranges. A few sills and dikes of basalt and andesite cut the Tertiary rocks (Buddington and Chapin, 1929, p. 260-275). Quaternary deposits are of minor areal extent and consist mostly of marine gravels, delta deposits, basalt, and tuffs (Buddington and Chapin, 1929, p. 275-281).
CHICHAGOF DISTRICT
The Chichagof district comprises an area of about 4,500 square miles and includes Baranof, Chichagof, Kruzof, and Sitka Islands.
The first attempts at lode mining in Alaska, under American rule, were made near Sitka in 1871 (Knopf, 1912, p. 8). These ventures and others in the succeeding few years failed, and mining in the Sitka area lapsed into a period of dormancy until the lode discoveries were made at Klag Bay on Chichagof Island in 1905. The Chichagof mine soon became the big producer here, with a production from 1906 through 1938 of $13,784,710 in gold (Reed and Coats, 1941, p. 89). The Hirst-Chichagof mine, which went into production in 1922, produced $1,702,624 in gold through 1938 (Reed and Coats, 1941, p. 104). In succeeding years production from these mines dwindled, and the Chichagof district was operating on a very small scale in 1959. The total recorded production for the district through 1959 was 770,000 ounces, all from lode mines.
The general geology of Chichagof and Baranof Islands has been described by Knopf (1912, p. 11-21), and according to him the oldest rocks are chert and quartzite which are overlain by cherty limestone of Silurian age. Devonian limestone and tuff, Mississippian limestone, Permian or Triassic gypsiferous limestone, Mesozoic graywacke, and postglacial lavas and tuffs complete the stratified rock sequence. The central parts of the islands are composed of masses of granitoid rocks, dominantly quartz diorite of late Mesozoic age. In the Klag Bay area of Chichagof Island masses of greenstone and greenstone schist of possible Triassic age (Reed and Coats, 1941, p. 14-22) occur between the diorite and graywacke. The stratified sedimentary rocks lie on the west bank of an anticlinorium, the axial part of which in this district is occupied by the diorite. Many northwest-trending high-angle faults cut the bedded rocks (Reed and Coats, 1941, p. 64).
The ore deposits are in plunging quartz bodies along the faults. Quartz is the main constituent of these lodes, but calcite may be present. Sulfides, in conspicuously minor amounts, consist of pyrite, arsenopyrite, galena, sphalerite, and chalcopyrite. Gold is present as specks in the quartz and in the sulfides (Reed and Coats, 1941, p. 78-80).
JUNEAU DISTRICT
The Juneau district includes Douglas and Admiralty Islands, lat 57°00' to 59°00' N. and long 133°00' to 135°00' W.
Placer discoveries were made in 1869 at Wind-ham Bay and at Sumdum Bay, about 50 miles south of Juneau, and lode gold, which has been the mainstay of the district, was discovered in 1880 by Joe Juneau and Richard Harris whose locations included the site of the Alaska Juneau mine, the largest lode gold mine in Alaska (Wright, 1906, p. 2). The discovery resulted in a rush to the area and the founding of the town of Juneau, which, by 1883, became the locus of gold mining in Alaska. Numerous lode properties were located near Juneau and on neighboring Douglas Island where the Treadwell group, including the Treadwell, Mexican, Ready Bullion, and 700 Foot mines, was quickly developed into a major producer, yielding $26,556,470 in gold through 1905. Caving, which began in the Treadwell and 700 Foot mines as early as 1913, culminated with the complete flooding of the Treadwell, 700 Foot, and Mexican mines in 1917 (Eakin, 1918a, p. 78-79). These mines were never reopened, but the Ready Bullion remained productive until 1922 (Brooks and Capps, 1924, p. 24). Other important mines in the early days of this camp were the Sumdum and Ebner. Production records for the Alaska Juneau mine began in 1893 and are complete to April 9, 1944, when the mine was closed due to manpower shortages and excessive costs (C. W. Henderson and R. V. Cushman, in U.S. Bureau of Mines, 1945, p. 232). This mine yielded a total of 2,874,361 ounces of gold, almost as much silver, and large quantities of lead. The closing of the Alaska Juneau mine signaled the end of gold mining in Southeastern Alaska. Only a few hundred ounces of gold were produced annually from the entire region from 1944 through 1959.
Total gold production of the Juneau district from 1882 through 1959 was 6,883,556 ounces - 66,279 ounces from placers, the remainder from lodes.
The eastern part of the district is underlain by the dioritic and granitic intrusives composing the Coast Range batholith of Late Jurassic or Early Cretaceous age (Buddington and Chapin, 1929, p. 173-175). This is flanked on the west by several north-trending bands of schist, slate, and greenstone (Spencer, 1906, p. 16-19) which according to Buddington and Chapin (1929, p. 73-74) may include rocks ranging in age from Ordovician to Cretaceous. Still farther west is a band of inter-bedded slate and graywacke with some greenstone which Buddington and Chapin (1929, p. 157) consider Jurassic or Cretaceous. The rocks have been folded into a northwest-trending synclinorium, bounded on the east by the Coast Range batholith and on the west by an anticlinorium (Buddington and Chapin, 1929, p. 289-290).
The gold deposits of the Juneau district, according to Spencer (1906, p. 22-24), are of three types: veins, impregnated deposits, and combinations of these two types, or mixed deposits. Though other rock types may be mineralized, most of the deposits are found in the slate and greenstone. The veins vary considerably in thickness, trend, and continuity. Quartz is the main constituent; however, calcite is common, and albite is abundant in some veins. Pyrite, galena, sphalerite, and arsenopyrite are the common sulfides. Gold is either associated with pyrite or arsenopyrite or is found as small flakes in the quartz (Spencer, 1906, p. 33-36). In the impregnated deposits, the country rock has been replaced by large masses of the sulfides listed above, but these deposits are relatively unimportant as a source of gold. The mixed deposits were the most important of the three types at the famous Treadwell mines (Spencer, 1906, p. 24).
KETCHIKAN-HYDER DISTRICT
The Ketchikan-Hyder district includes the southern end of the Alaska panhandle, roughly the area between lat 54°20' and 57°00' N. and long 130°00' and 134°00' W.
Most of the early mining interest in Alaska was centered in Sitka and Juneau, and Ketchikan was neglected for many years. But in the late 1890's discoveries of gold and copper were made at Ketchikan, and this together with the news of the Klondike successes encouraged many people to prospect the new area (Brooks, 1902, p. 39). By 1900 there was feverish activity in the district with several mines open and many claims located. Gold was produced from auriferous veins and from copper ores.
At Hyder, near the Canadian border, lode deposits of gold were discovered in about 1901 but were neglected until 1909, when a short-lived boom occurred (Buddington, 1929, p. 2-3). In the 1920's there were several small discoveries near Hyder that caused some mild excitement.
Production of gold from the Ketchikan-Hyder district amounts to about 62,000 ounces, of which 35,000 ounces is byproduct gold from copper ores and 27,000 ounces is from lode mines. Data for 1938-46 are incomplete. The district was still active in 1959, though only small quantities of byproduct gold were produced.
The oldest rocks in the district are limestone and phyllite of Silurian or pre-Silurian age. These are overlain by limestone, slate, and schist of probable Middle Devonian age. In the central part of the district the Devonian rocks are overlain by argillite, limestone, and sandstone of the Ketchikan Series, partly of Paleozoic and Mesozoic age. Locally, Mesozoic conglomerates overlie the Devonian rocks. A broad belt of granite (or diorite), part of the Coast Range batholith, underlies the eastern part of the district (Brooks, 1902, p. 40-41), but the most widely distributed igneous rock is the Kasaan Greenstone, which is the oldest of the intrusive rocks. Warner, Goddard, and others (1961, p. 13) imply that the greenstone is of Mesozoic age, but older than Cretaceous. In general the metasedimen-tary rocks throughout the district occur in northwest-trending bands (Brooks, 1902, p. 51).
The geology of the Hyder area is summarized as follows from Buddington (1929, p. 13-42). The Hazelton Group, of probable Jurassic age, is composed of greenstone, tuff, breccia, graywacke, slate, argillite, quartzite, and some limestone, and it occurs as large disconnected patches in the east and west parts of the area. The beds are tightly folded and strike predominantly to the east. A granodiorite batholith, called the Texas Creek batholith, intruded the Hazelton Group, and the Hyder Quartz Monzonite and the Boundary Granodiorite intruded both the Hazelton Group and Texas Creek batholith. The intrusive rocks are of Jurassic or Cretaceous age and are genetically related to the Coast Range batholith.
The ore deposits are somewhat varied in this district; commercial amounts of silver, copper, iron, lead, and zinc are present in addition to gold. The ore deposits are of four general types—vein deposits, breccia veins, mineralized shear zones, and contact metasomatic deposits. The veins occur in the oldest rocks of the district. They range in width from a few inches to 10 feet or more and are made up of quartz, calcite, pyrite, chalcopyrite, galena, sphalerite, and gold (Wright and Wright, 1908, p. 80-81). Breccia veins, most abundant in the limestone and schist, consist for the most part of quartz-cemented country rock. Auriferous sulfides may be in limestone fragments or in the quartz (Wright and Wright, 1908, p. 81-82). The shear zone deposits range in width from 5 to 50 feet and follow the structure of the enclosing rock—most commonly slate or greenstone. The dominant minerals are quartz and calcite in veinlets and chalcopyrite and pyrite disseminated throughout the rock. Gold occurs in the quartz-calcite veinlets (Wright and Wright, 1908, p. 82-83). The contact meta-morphic deposits are in limestones near their contacts with intrusives. These deposits consist of masses of chalcopyrite, pyrrhotite, pyrite, and magnetite in a gangue of garnet, epidote, calcite, quartz, amphibole, and wollastonite. Both copper and gold are produced from these deposits (Wright and Wright, 1908, p. 83-84). On the Kasaan Peninsula, contact metasomatic deposits of magnetite, pyrite, and chalcopyrite are found in association with tac-tite bodies in layers and lenses of metamorphosed sedimentary rocks in the Kasaan Greenstone (Warner and others, 1961, p. 30-52).
Worthy of special mention is the Salt Chuck mine on the Kasaan Peninsula. Originally located as a copper prospect in 1905, this deposit was later found to contain platinum minerals and gold and silver in recoverable amounts (Holt and others, 1948, p. 3). The ore bodies are masses of bornite and chalcopyrite that have replaced and filled fractures in a pyroxenite country rock (Mertie, 1921, p. 124-125). According to Holt, Shepard, Thorne, Tolonen, and Fosse (1948, p. 4), a total of 326,000 tons of ore with an average gold content of 0.036 ounces per ton was produced from the beginning of mining to the spring of 1941. This amounts to 11,736 ounces of gold.
PORCUPINE DISTRICT
The Porcupine district is just north of lat 59°15' N. at long 136°20' W. along Porcupine Creek, a tributary of the Klehini River.
Productive gravels were discovered in 1898 along Porcupine Creek and its tributaries (Wright, 1904, p. 12). The era of greatest activity was from 1900 to 1906 when about $100,000 in gold per year was produced. Between 1915 and 1917, hydraulic equipment was installed which accounted for a brief rejuvenation of the district (Eakin, 1918b, p. 99), but from 1917 through 1959 there was only occasional small-scale production by individuals. Total production for the district through 1959 is 53,250 ounces, all from placers.
The northeast part of the district is underlain by dioritic rocks of the Coast Range batholith. Bordering this on the south is a northwest-trending belt of phyllite, slate, and limestone of Late Pennsylvanian or Early Permian age. An elongate mass of diorite cuts the metasedimentary rocks in the west and southwest part of the district. The metasedimentary rocks are also cut by numerous stringers of quartz and calcite carrying variable amounts of sulfides, and locally the rocks are impregnated with lenticular masses of sulfides.
Placers consist of creek gravels, side benches, and high benches. The gold probably was derived locally by erosion of the auriferous sulfides in the country rock.
YAKATAGA DISTRICT
The Yakataga district, an area of about 1,000 square miles, is between lat 60°00' and 60°30' N. and long 141 °20' and 144°40' W., just west of the northern end of the panhandle that forms southeast Alaska.
The date of discovery of ore in the Yakataga district is unknown. According to Maddren (1913b, p. 133), gold was first found in the beach sands at Yakataga about 1897 or 1898, but Smith (1933, p. 96) listed the first production for the area in 1891. During the first years the beach sands were worked with simple rockers. Later, several attempts at larger scale mining, by using sluice boxes, were made (Maddren, 1913b, p. 133-134). Bench gravels along the White River were found to be gold bearing and these have been worked intermittently by hydraulic methods. Total recorded production for the district from 1891 through 1959 was only 15,709 ounces, all from placers. In 1959 the district was virtually inactive; less than 75 ounces was reported from 1950 through 1959.
In the northern part of the district the high St. Elias Range, which dominates the landscape, is composed of intensely contorted metamorphic and intrusive rocks. The Robinson Mountains, in the central part of the district, are composed of Tertiary and Pleistocene sedimentary rocks in northwest-trending folds. In the south, the district is covered with outwash gravel and fluvial deposits (Maddren, 1913b, p. 126-132). The gold in the beach placers was concentrated by wave action from the glaciofluvial deposits of the White River. The ultimate source of the gold was the crystalline rocks of the St. Elias Range from which the gold was removed either by glaciers or by Pleistocene streams and was redeposited at lower levels. The present stream system of the White River reworked the auriferous outwash gravel and Pleistocene fluvial deposits and concentrated the gold in channel sands which now form low benches that are being eroded (Maddren, 1913b, p. 142-143).
