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pMNDLe.] FORTYMILE, BIRCH CKEEK, AND FAIRBANKS PLACERS. 39
Since the discovery of gold on Fortymile Creek, in 1886, prospectors have devoted much attention to its basin. The most important creeks at present are Wade, Walker Fork, Chicken, and Franklin, while some work is being done on the Fortymile itself, Napoleon Creek, the tributaries of Canyon Creek, and on North Fork of Fortymile. Prospecting is in progress in many places and still results occasionally in discoveries of economic importance.
Wade Creel-.—The basin of Wade Creek, which is reached by trail from the mouth of Steele Creek, lies about 10 miles south of the Fortymile, and embraces about 50 square miles (map, Pl. VII). The creek, which is about 12 miles long, heads in Steele Dome, 3,750 feet high, and flows in a nearly straight southwesterly direction, entering Walker Fork a few miles above its mouth. There is a fall of about 000 feet from the upper limit of placer mining to the mouth—a distance of about 8 miles. The valley is sunk to a depth of about 1.500 feet within the plateau, and is narrow and V -shaped in its upper portion-; lower down it gradually widens, finally merging into the valley of Walker Fork, where the stream follows a meandering course over the surface of a broad flat. The spurs from the northwest descend somewhat more gradually toward the stream than those from the opposite side, and the cross section-of the valley is thus somewhat unsymmetrical. The general characteristics are shown in Pl. VI, B. The tributaries are short and flow in narrow V-shaped valleys. In dry seasons the demand for water far exceeds the supply, and much of the mining is brought to a standstill.
There is considerable timber on the northwest slopes of the valley, and a light growth of spruce on the southeast. The valley floor is generally covered with willows, but in the wider portion, toward Walker Fork, is well timbered with spruce and aspen. Dawson is the main source of supply, and most of the freighting is done during the winter.
The bed rock in which the valley of Wade Creek has been incised includes several varieties of schist and some ferruginous, thinbedded limestone, which is apparently interbedded with the schist. Mica-schist and hornblende-schist are the most common rocks. Their attitude is variable, but the general strike is northeast, about parallel with the creek, and the dip of the schistosity varies from nearly horizontal to 50c or more to the southeast, while a prominent system of joints strikes N. 30° W. The schists are often contorted and the structure is probably complex. A small dike of basalt, with a strike of N. 00° E., was observed about a mile above Robinson Creek. Quartz veins are common in the schist and seem more abundant toward the head of the creek. Both bed rock and quartz veins contain in places considerable pyrite.
The gravels vary from 1 foot to 3 or more feet in thickness and are composed of the rocks that are found outcropping in the valley and along its slopes, no foreign material being observed. The proportion of vein quartz is small. The fragments are more or less angular, owing to the schistose and jointed structure of the bed rock, are little worn, and are generally less than a foot in diameter. They are found across the entire width of the valley and on the low bench-like termination of the spurs, perhaps 10 to 20 feet above the valley floor. The gravels are covered with a layer of muck up to 20 feet in thickness.
It is said that gold was discovered on this creek by Jack Wade about 1895. Rim prospects were found in the fall of 1898. The gold is rarely found more than l| feet above the bed rock in the gravels. Most of it is on bed rock and extends into it in crevices and along joint planes to a depth, in places, of 4 feet. It occurs rather irregularly, and the creek has the reputation of being spotted. Good pay was first struck on the rim at the terminations of the spurs on either side, and these became the favorite localities for work. The pay there is more accessible and found frequently in greater quantities than on the valley floor.
As much of the gold occurs as nuggets, which are irregularly distributed, it is difficult to form an idea of the average value of the ground. It is said to average about $100 to the box length of 12 by 12 feet, but some ground has yielded, by the winter's work, from 50 cents to $3 per cubic yard, including everything from surface to bed rock.
Much of the gold is picked up during the work, and many nuggets have been found. One was found during the winter of 1900 worth $216; and in January, 1903, one was picked up which measured H by lj by 1J inches and was worth $558. A week later another was found worth $437.85 in gold, valued at $17 to the ounce. The nuggets are well smoothed, of a bright yellow color, contain very little quartz, and are often convex on one side and more or less flat and irregular on the other. Some of the prospectors had observed that the nuggets found by them were generally rougher on the side lying next to bed rock. The larger nuggets have been found in the part of the valley which is about midway between the source and the mouth. . The gold occurs generally as small flat pieces, and a large portion of that from the head of the creek is rusty. The little gold found in prospecting the side gulches differs in character from that in the main creek in that it is very rough and somewhat rusty. Very little fine gold is found, and the proportion of black sand is small. Barite is abundant, and its rounded pebbles are a characteristic associate of the gold. Black, shiny, rounded grains of hematite are also found.
The fact that no foreign wash was observed makes it probable that the gold has been derived directly from the drainage area of the creek itself. Many quartz seams and stringers occur in the schists, some of them of considerable thickness, but the quartz is not sufficient in quantity to make the proportion in the gravels a very large one. Pieces of gold with quartz attached are common. Both the schists and the quartz contain pyrite. One quartz vein occurring in the upper portion of the creek was found by assay for the Survey by E. E. Burlingame & Co., Denver, Colo., to carry 0.06 of an ounce of gold to the ton. It would seem from the information available that the gold has probably been derived from quartz veins and stringers in the schists and possibly also from mineralized areas in the schists themselves.
The mining developments are scattered along about 5 miles of the creek, commencing at a point about 4 miles above the mouth and extending toward the source. Claims are generally one-fourth of a mile lengthwise of the creek. There are two Discovery claims, and claims have been staked from each in both directions. The gold is mined by drifting, by hydraulic methods, and by open cuts.
Where the ground is deep and frozen some method of thawing is necessary. The most primitive way is by the wood fire. Hot water and hot rocks are sometimes used, either alone or in combination, but the most effective method is that of the steam thawer. The apparatus consists generally of a small boiler for the generation of steam, pipes for its transmission, and points. The latter are pipes, 4 feet or more in length, for driving into the frozen ground. They are connected near the one end with the steam pipe and provided at the pointed end with one or more small apertures, through which the steam rushes with greatly increased penetrative force, like water from the nozzle of an ordinary hose. They are placed against the frozen ground and driven in as fast as the ground becomes thawed. The quantity of steam can be easily regulated, and successful results on sinking and drifting depend largely on experience and good judgment in the use of the steam. Too much steam is liable to thaw the walls or roof of a drift to an undesirable extent and cause " sloughing," or falling in of the walls, with the consequent necessity of handling much more dirt than is necessary.
The drifting method is employed on Wade Creek mostly during the winter, the dump being washed out in the spring. On several of the claims the hydraulic method was in use in a small way. Pl. VIII, A, shows a claim being stripped of muck by this method. Ditches have been built up to about a mile in length, and when used in connection with canvas hose give sufficient head to strip the muck from the surface of the gravel, so that it can be reached and shoveled directly into the sluice boxes. The open-cut method is being introduced. For this the grade of the creek necessitates a bed-rock drain 700 feet or more in length. The muck, perhaps 7 feet thick, is stripped by ground sluicing and the gravel shoveled in.
As much of the best ground has been worked out, development is being carried laterally to the benches, which may furnish considerable gold. The difficulty, however, is to get sufficient water, the season of 1903 being a particularly bad one in this respect. The output for the year 1902-3 was generally supposed to be about $50,000, and the expense of working probably absorbed from 40 to 50 per cent of this amount. About 50 men were at work on the creek, and wages were $5 and board.
Walker Fork and neighboring localities.—The area of economic interest on Walker Fork is in the far southeast corner of the Fortymile quadrangle (Pl. VII) and extends from the boundary nearly to Cherry Creek, a distance of about 4 miles. It is reached from Wade Creek by a good trail of about 14 miles along the ridge, and also from points on the Canadian side, whence the supplies are generally obtained.
The headwaters of Walker Fork are small streams having their sources in the divide about a mile within Canadian territory. Poker and Davis creeks, which are the most important of these small streams, have narrow V-shaped valleys. Poker Creek flows directly west, about 1 mile of its short valley being on the American side. Davis Creek flows southwest in a similar valley and joins Walker Fork about one-fourth of a mile below Poker; it heads just beyond the boundary, about \\ miles of its valley being on the American side. Both were described by Goodrich in Spurr's report."
The course of Walker Fork below7 Davis is westerly, with a fall of about 100 feet to the mile. The valley is bounded on the north by a dome 3,380 feet high and to the south by a spur which descends gradually from an altitude of over 4,000 feet and terminates just south of the creek in a benched surface 400 feet high. The valley is about 2,000 feet above sea level and is unsymmetrical in cross section. Across the valley to the north the rise to the plateau level of about 3,000 feet is gradual and there is a bench corresponding to the one on the south. The slopes are covered with a light growth of small spruce, and the valley floor in places has produced timber of sufficient size for mining purposes.
The bed rock, similar to that of Wade Creek, includes quartziteschists, graphitic schists, and garnet-hornblende-schists. Strikes
• Spurr, J. E., Geology of the Yukon gold district: Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 3, pp. 326-331.
were observed varying from 50° to 80° to the northeast, and the rocks have been closely folded. Quartz seams are common.
The material on Lkml rock varies from 4 to 12 feet in thickness and includes muck, sand, gravel, and sometimes clay. In places there is no muck on the gravels, and rarely no gravels are found under the muck. The average thickness of the gravels is about 0 feet, generally exceeds 4 feet, and the maximum is 10 feet. A small amount of clay is sometimes found between the gravels and bed rock. Occasionally rounded quartz bowlders a foot or more in diameter are found, but the greatest proportion is composed of angular schist fragments of small size.
The thickness of the gravels increases gradually downstream, and from year to year it has' been found profitable to work those of greater depth. Unlike Wade Creek, the gold is found not only on the bed rock, but in the gravels above bed rock through a distance oftentimes of 2 feet or more. In the bed rock it is found to a depth of li feet. The pay streak has been worked in places over a width of 50 feet, but on the outer limits it contains small values. Ground has been worked, ranging in values to over $2 per cubic yard, and is said to run from $50 to $100 to the box length. The gold is found in pieces worth as high as $20, but the general run consists of small, flat pieces. Toward the head of the creek it is frequently black. Its origin is supposed to be in the small quartz stringers in the schist, which have sometimes been found to carry gold.
As the drainage area is small a dry season quickly affects the water supply, thus making the output of the creek, especially that of the upper portion, largely dependent on climatic conditions. The richest gravels on these creeks have apparently been worked out, but there is some ground left which could probably be made to pay if water were available. On AValker Fork several outfits have been doing fairly well during the past few years on ground that was not worked in the early days, and the present annual production is probably about $20,000 to $25,000.
Most mining has been carried on by the open-cut method. For this it has been found necessary, on account of the low grade of the stream, to construct bed-rock drains 400 to 1,000 feet in length. A horse scraper was in use on one claim to clear away the tailings, and on another a steam engine was in operation, running a scraper and a bucket conveyor to elevate the dirt to the sluice boxes, handling effectively 400 to 500 scrapers of dirt a day (Pl. VIII. B).
In July, 1903, about 40 men were working on AValker Fork and its tributaries, and wages were $4 a day with board.
The country south from Walker Fork on the headwaters of Cherry Creek is being prospected. The bed rock and gravels of this area are similar in character to those found on Walker Fork. At the