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

Origin of and Tectonic Controls for
Maclaren Metallogenic Belt
The Maclaren Glacier metamorphic belt, which hosts the Maclaren metallogenic belt of Au quartz vein deposits, and part
of the Mac laren terrane, displays classic prograde, Barrovian-type metamorphism of which the lower, greenschist facies portions
are judged as highly favorable for Au-quartz vein deposits. 40Ar-39~r ages sf metamorphic minerals in auriferous quslrtz veins
which occur in the lower greenschist facies and have isotopic ages rangeing horn about 58 to 62 Ma (early Tertiary) (Adams and
others, 1992). These ages are interpreled to indicate that Au caineralizahon occurred in the early Tertiary during oblique
subduction of Kula-Farallon ocearlic ridge under margin of southern Alaska (Bradley and others, 1993; Hamsla and Nelson,
1993; Haeussler and others, 1995; Goldfarb and others, 1995; 1997; Goldfarb, 1997)..
The Maclaren terrane is interpreted as a displaced continental-margin arc fi-agment which was tectonicatly separated &om
the Kluane schist and the Ruby Range batholith that both occur on the northeast side of the Deslali fault some400 km to the
southeast in the Yukon Territory (Nokleberg and othcrs, 1985,1994d, 2000; PlanCer and others, 1989). Similar major Au quartz
vein deposits occur in the Juneau metdogenic belt of southeastcro Alaska (described herein) (Noklrberg arid othm, 1985, 1993,
1994d).
Talkeetna Mountains Metallogenic Bdt of
Au Quark Vein Deposits (Belt TM)
Northern Part of Southern Alaska
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The Talkeetna Mountains metallogenic belt of Au qu& vein deposits occurs in the Talkeehna Mountains in the northern
part of southern Alaska (fig. 1 03; tables 3,4) (Nokleberg and o@m, 1997b. 1 998). The metallogenic belt is hosted in the Late
Triassic(?) and Early Jurassic Talkeetna Fmation where intruded Jurassic and Cretaceous granitoid rocks that w ~ deformed e
and metamorphosed to lower greenschist hcies during the early Tertiary Wokleberg aod others, 1994c, 1997~). Tbe significant
deposit is the Independence mine in the Willow Creek District. Other deposits in the district inchde those at Gold Bullion, Gold
Cord, Lucky Shot, and Thope
Independence Au Quartz Vein Deposit E"l
The lndepeodeoce Au qurtz vein deposit, which occurs in the Willow Creek district in the Talktetna Mounmim (Ray,
1954; Madden-McGuire and others, 1989), consists of quartz veins containing a few percent or less pyrite, chalcopyrite,
magnetite, and gold, and minor arsenopyrite, sphlerite, tetrab&t.e, Au-tehiidcs, and galena. The veins amgt 0.3 to I m thick,
but some range up to 2 m thick The veins occupy east-northeast and nor&-south-striking shear zones up to 7 m wide.
Considerable alteration of wall rocks occm marked by formation of sericite, pyrite, carbonate, aad chlorite in pasallel baa&. The
veins occur in zones in and along the southern margin of Jwic quartz diorite, and younger Cretaceous aml early Tertiary
granitoid rocks of the Talkeetna Mounlahs balholith, and also locally in mica schist. The Willow Creek district consists ofseveral
mines and many prospects, most In an area about 12.8 km long and 6.2 karr wide along southern portion of the Talkeetna
Mountains batholith. The mine at the deposit contains several thousand meters of underground w~rkmgs and prodwed about
18,400 kg Au from 1909 to 1950. Ore grade ranged fiom about 17 to 69 g/t Au.
Origin of and Tectonic Controls for
Talkeetna Mountains Metallogenk Belt
Hydrothermal micas from the Gold Bullion and Lucky Shot mines in the WiHow Creek district exhibit K-Ar isotopic ages
of 66 and 57 Ma, respectively (Madden-McGuire and others, 1989). These ages are interpreted to indicate that gold mineralization
in the Talkeetna Mountains mefaUogenic belt occurred m the Late Cretaceous or early Tertiary. Tbree different tectonic events
might be the cause of mineralization: (1) Late Cretaceous and early Tertiary u ndeting of the Chugwh and Prince William
accretionary-wedge terranes along the Contact fault in southern Alash, (2)as favored herein, early Tertiary ult-ing of the
spreading Kula Ridge under the southern margia of coastal Alaska (Plafker and others, 1989); and (or; 3) early Tertiary dextral-
slip faulting along on the Castle Mountain fault system.
Chugach Mountains MetalloOenic Belt of
Au Quartz Vein Deposits (Belt CM)
Southern Alaska
The Chugach Mountains metallogenic belt of Au quartz vein deposits (fig. 103; tables 3,4) occurs on Kodiak Island, the
southeastern Kenai Peninsula, and in the cmtral and eastern Cbugach Mountains in southern Alaska. The Au qua& vein deposits
occur mainly in the Late Cretaceous flyscb of the Valdez Group and Kodiak Formation where these units were metamarphosed to
greenschist facies (Goldfarb and others, 1986, 1997, 1998; Nokleberg and others, 1994c, 1997c, 1989b). To a lesser extent, the
belt also occurs: (1) in the northern margin of the early Tertiary Orca Group of the Prince William terrane where locally
metamorphosed to lower greenschist facies; (2) in metasedimentiuy rock of the Orca Group within a few kibmeters of granitoid
plutons; (3) along the southern margin of the Late Triassic through mid-Cretaceous McHugb Complex on the Kenai Peninsula;
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