The Porcupine district is just north of lat 59Â°15' N. at long 136Â°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.
The Yakataga district, an area of about 1,000 square miles, is between lat 60Â°00' and 60Â°30' N. and long 141 Â°20' and 144Â°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).
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