Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Creek, and Nikolai; the major Kennecott Cu deposits are in the Kennecott district at Kennecott and Westover; and a basaltic Cu
deposit is at Erickson (table 4) (Nokleberg and others 1997a, b, 1998).
Kathleen-Margaret CU-Ag Quartz Vein Deposit
The Kathleen-Margaret Cu-Ag quartz vein deposit (MacKevett, 1965) consists of quartz veins which are up to 140 m
long and 3 m wide and contain disseminated to massive chalcopyrite, bornite, and malachite. The gangue is mainly q u a and
minor calcite. The veins cut the Late Triassic Nikolai Greenstone, strike east-west, and are intruded along shear zones. Grab
sampIes from the deposit contain up to 13% Cu, 3.2 g/t Au, 300 g/t Ag. About 1.8 tonnes of ore was produced in the 1950's. At
the nearby Nugget Creek deposit slablike copper nuggets of several tonnes weight occur.
Kennecott Cu Deposits
The large Kennecott Cu deposits (fig. 101) (Bateman and McLaughlin, 1920; MacKevett, 1976; Armstrong and
MacKevett, 1982; MacKevett and others, 1997) consist mainly of chalcocite and covellite, and also have m kr enargite, bomite,
chalcopyrite, luzonite, and pyrite. Tennantite, sphalerite, and galena are extremely rare. Local surface oxidation occurs with
alteration of sulfides to malachite and azurite. Sulfide minerals occur mainly as large, irregular, massive, wedge-shaped bodies,
mainly in dolomitic parts of the Late Triassic Chitistone or Nizina Limestone. The bodies are generally less than 100 m above a
disconformity over the subjacent Middle and(or) Late Triassic Nikolai Greenstone. The largest ore body (Jumbo) consists of an
almost pure chalcocite and covellite mass, which is about 1 10 m high, up to 18.5 m wide, and which extends 460 m dong plunge.
The Kennecott Cu mines were among the largest group of mines in Alaska from 191 1 until 1938, when the ore was mostly
exhausted. The district contains more than 96 km of underground workings. The major mines in district are the Jumbo, Bonanza,
Erie, Mother Lode, and Green Butte. The district produced about 544 million kg Cu and 280 million g Ag from 4.3 million tonnts
of ore.
fl Copw we zone
_ ,
- - - OuUine of brecciated
dolomite at surface
Contours on Nikdai-
.....---- Chitistone contact
in feet abve sea level
Kv Fault surface
/ Vertical fault
/ Contact
Figure 101A. Kennecott district of Kennecott Cu deposits, Wrangell Mountains metallogenic belt, Southern Alaska. Schematic
geologic map showing the Bonanza-Mother Lode and Jumbo ore zones, major faults, and contours on contact between the Nikobi
Greenstone and the Chitistone Limestone. Modified from MacKevett and others (1 997).