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

several tens of meters to 1,300 m long. The veins and stockworkr are hosted in Middle to Late Devonian or Early Carboniferous
volcanic rocks of the Kedon series. The veins occur along fractures, malndy In extrusive andesite breccia of a volcanic vent, and
more rarely, in hypabyssal dacite-porphyry bodies and felsic extrusive rocks. The ore minerals include gold, chalcopyrite,
argentite, polybasite, galena, sphderite, pyrite, hematite, Mn-oxides, slrameyeriie. letrahedrite, native silver, and tellurides. The
gangue minerals are quartz and adularia. with lesser calcite, dolomite, rbodochrosire, and barite. Au md Ag Is asstleiattd with Hg,
Cu, Mo, Pb, Zn, Mn, and As. The deposit exhibits propytitic and quartz-suicilc Illterntion The Au-Ag ore bodies are controM by
arcuate faults which occur around a volcano-tectonic depression over a basement composed of Archean metamorphic rock end
early Paleozoic(?) carbonate and clastic sedimentmy rocks. Adularia hbm qu& velns has been dated by K-Ar isotopic shldie~
268 Ma and by Rb-Sr isotopic studies as 25 1 Ma. More recent K-Ar dating of adularia from Au-bearing veins yield an age of 3 18
Ma. The deposit is medium size, and gade ranges from 0.5 to 273 glt Au and 26.3 to 4,978 g/t Ag.
Origin of and Tectonic Controls for
Kedon Metallogenic Belt
The Omolon cratonal termne, which hasts the Kedon rnetallogenic belt, consists of a long-lived succession of Archean to
Early Proterozoic crystalline basement, Middle Proterozoic thf~ugh middle Paleozoic miogeoclinal sedimentary rocks (Nokleberg
and others, 1994c, 1997~). Tba younger part of the stratigraphy consists of unconformably overlying, widespread, gently-drpping
Middle and Late Devonian calc-alkaiic lava, and rhyolite tuff, and Early Carbonikous trachyte, trachyandesite, and basalt which
are interlayered with nonrnarine sandstone, conglomerate, and siltstone. These rocks constitute the Kedon arc of Shpikennan
(1998). The felsic-magmatism-related lode deposits and host rocks of the Kedon metallogenic beit are interpreted as farming in
the Kedon continental-margin magmatic arc which formed in the Late Devonian. Subsequent to the Kedm are, the hlon terrane is interpreted having been rifted frm the North Asian Craton (Nokleberg and others, 2000; Shpikennan, 1998).
Eastern Seward Peninsula (Klwaltk Mmain)
Metallogenic Belt of Kurokd Massive S U M Deposits
(Belt ES) Northwestern Alaska
The Eastern Seward Peninsula metallogenic belt of kuroko massive sulfide deposiu occurs in the Kiwalik Mountah
region of the Seward Peninsula in northwestern Akka (fig. 17; labb 3.4) (Nokleberg and others, 1997b. 1998, Ske: 4). The
metallogenic belt is hosted in a thin, tectonicdy-transposed unit of middie Paleozoic(?) felsic schism and meavolcenic i d s of
the Seward metamorphosed cootinenlal margin terrane (Nokleberg and orhers, 1994c, 1997~). Two stnall occurreaces on tbe west
flank of Kiwalik Mountaln consist of chalcopyrita, galena, tetrahedrik, and sphdmik in layers and as dissanhtiom. The layers
range from 0.2 to 2 m thlckand occur parallel to compositional layering in a 200 mekr-lhi&sechn of mchfehlte, "button schist'.
and metatuff. The Klwalik Mountain belt are interpreted as the extension of the Arctic metallogenic belt ofkuroke mive sulfide
deposits described below (T.K. Bundtzen and Thomas Craffvrd, witten cornmun., 1991).
Arctic Metallogenic Belt of
Kuroko and Kipushi Massive Sulfide Depodts
(Belt AT) Northern Alaska
The extensive Arctic metallogenic belt of major kuroko massive sulfide deposits (tables 3,4), which contains the Ambler
district, and one Kipushi Cu-PBZn deposit, occurs along an east-west trend for about 260 km along the southern flank of the
Brooks Range in northern Alaska (fig. 17). The metallogenic belt is hosted in a sequence of metavolcanic and sedimrn~ rocks
which occur in both the Coldfoot metamorphosed continental-margin teme of the southern Brooks Range, and in the Nonie
Group in the southern Seward Peninsula in the Seward metamorphosed continental-margin ttme (Nokleberg and oxhers, 1994~,
1997c; Schmidt, 1997b). The Arctic kwoko massive sulfide and the Ruby Creek Kipushi Cu-Pb-Zn (fig. 22)deposits occur in the
Ambler district (Hitzman and others, 1986); other lruroko massive sulfide deposits of the district are at Smucker, Michigan Creek.
BT, Jerri Creek, Sun, and Roosevelt Creek prospects (table 4) (Nokleberg and others 1997a, b, 1998).
Arctic Kuroko Massive Sulfide Deposit
The Arctic kuroko massive sulfide deposit (Wiltse, 1975; Sichem and others, 1936; HitPnan md OW, 19Q
Schmidt, 1983; Schmidt, 1986, 1988; HitPnan and others, 1986) consists of suatifonn, semi-massive to mas;sive chalegpyril md
sphalerite accompanied by lesser pyrite, minor pyrrhotite, gelena, ktdaedrite, amnopyrite, and mes of bornite, magnetite, and
hematite. The deposit occurs in a thick horizon which has an areal exfent of about 900 by 1.050 m, and in two thinnt~ hciri~011s
above the main horizon. The sulfides form multiple lenses up to 15 m thick over stratigraphic interval of 6 to 80 m. The gangue
minerals are mainly calcite, dolomite, barite, quartz, and mica. Locally abundant chlorite, phlogopi~t8lc-barite, aad pyritecalcite-white
mica occur in hydrothermally-altered wall rocks overlying, underlying, and interlayered with sulfide mjnet~liizstion,
The alteration is interpreted as occuning during rapid influx of cold seawater into a hot hydrothermal vent system. The deposit
contains an estimated 37 million tomes grading 4.0% Cu, 5.5% Zn, 0.8% Pb, 47 glt A&, 0.62 g/t Au. The deposit is h~sred in part
of the