Yukon Region Alaska Gold Production
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.