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Alaska Gold Rush History and
Genealogy
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The Copper River region
(p1. 1, fig. 7) includes the area drained by the Copper River and
its tributaries, the area east of the divide between Prince William
Sound and Cook Inlet, the area drained by streams flowing into the
Gulf of Alaska between the Copper River and long 1410 W., and offshore
islands, including Middleton Island. It is divided into five . The
region includes parts of the Alaska Range, Wrangell, St. Elias, and
Kenai-Chugach Mountains and extensive lowlands along the Copper and
Chitina Rivers. The mountains, which rise to summits more than
16,000 feet in the Wrangells, and to mor than 18,000 feet at Mount
St. Elias, support and nourish the largest icefields and piedmont
ice lobes and some of the longest valley glaciers in North America,
all remnants of even more extensive Pleistocene ice that covered
most
of the region. The lowlands along the Copper River are floored by
thick accumulations of
Pleistocene and Holocene glacial, lacustrine, and fluvial deposits
that are frozen to depths of several hundred feet. The islands and
most of the shores of Prince William Sound, the extensive Copper
River Delta, and the lowlands and low mountains bordering the Gulf
of Alaska in the Yakataga district are generally free of permafrost.
The following summary of the geology of the Copper River region
is based mainly on reports and maps by Brabb and Miller (1962), Jones
and MacKevett (1969), MacKevett and Smith (1968), Moffit (1938a,
1954a,
1954b), Plafker (1967), Plafker and MacNeil (1966), and Smith and
MacKevett (1970).
Bedrock in the Copper River region ranges in age from late Paleozoic
to Quaternary. The bulk of the rocks are of Mesozoic age and include
large masses of graywacke, slate, and greenstone and lesser amounts
of carbonate rocks. Recent work has shown that some of the rocks
near
Prince William Sound previously considered to be Mesozoic are Tertiary
in age. In late Mesozoic and early Tertiary time, plutons, some of
batholithic dimensions, were emplaced in many parts of the region.
They range in composition from granite to dunite but most are
granodiorite, quartz diorite, and related rock types.
In the Yakataga district, complexly deformed Cenozoic marine and
continental rocks underlie the area between the crest of the Chugach
Mountains
and the Gulf of Alaska and may be continuous with similar coeval
rocks in Cook Inlet and on Kodiak Island. Middleton Island is composed
of slightly indurated marine clastic sediments that were deposited
in part by floating ice and are correlative with generally similar
rocks exposed on the main-land. The most extensive formation in the
Wrangell Mountains is a thick pile of Tertiary and Quaternary basaltic
flows and associated rocks. The crater of Mount Wrangell (14,005
ft)
still emits steam and ash.
Lodes in many parts of the Copper River region contain copper, gold,
silver, molybdenum, antimony, nickel, chromite, lead, and zinc, but
only copper, gold, and byproduct silver were mined commercially (Berg
and Cobb, 1967, P. 37—73, figs. 10—13).. The famous Kennecott
mines near McCarthy in the Nizina district and mines in the southwestern
and northeastern parts of Prince William Sound accounted for most
of the copper produced in Alaska. Gold worth $2 or $3 million and
smaller amounts of silver were produced from mineralized quartz and
calcite veins and byproducts of copper mining in the Prince William
Sound district. Similar veins near Golconda Creek (27, fig. 7)
and in the southeastern part of the Nelchina district were mined
on a small scale, but the entire region was not a statistically significant
contributor to the total lode-gold production of Alaska.
Placer deposits have been worked in all districts of the Copper River
region, but the total production probably was no more than 350,000
fine ounces of gold and a few ounces of platinum. Placers near the
head of the Chistochina River and near Slana in the northern and northeastern
parts of the Chistochina district acccounted for an estimated 150,000—160,000
ounces of gold and all the platinum; deposits in the north-central
part of the Nizina district accounted for about the same amount of
gold; and beach and stream placers in the Yakataga and Nelchina districts,
practically all the remainder. Placer-gold production from the Prince
William Sound district probably did not exceed 500 ounces. |
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Districts:
Chistochina, Nelchina, Nizina, Prince William Sound, and Yakataga |
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