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

Eastern Asia-Arctic Metallogenic Belt:
Chaun Zone of Granitic-Magmatism-Related
Deposits (Bek EACN) Northeastern Part of
Russian Northeast
The Chaun zone of felsic-magmatism-related deposits (fig. 79; tables 3,4) occurs in the northeastern part of the Russian
Northeast (Goryachev, 1998,2003; this study). The principal deposit types in the Chaun zone are Sn silicate-sulfide vein, Sn
greisen, Sn skam, porphyry Sn, Sn and Sn-Ag polymetallic vein, and granitoid-related Au deposits. The zone occurs in the rear of
the Okhotsk-Chukotka volcanic-plutonic belt and adjacent areas (Nokleberg and others, 1994c, 1997c), and extends
approximately east-west for about 1,300 km ti-om the mouth of the Kolyma River to Uelen. The Chaun zone is correlated across
the Bering Straits with the Seward Peninsula metallogenic belt in northwestern Alaska which contains similar deposits (fig. 80).
The significant deposits in the zone are (table 4) (Nokleberg and others 1997a, b, 1998): Sn silicate-sulfide vein and Sn
polymetallic vein deposits at Dioritovoe, Elmaun, Erulen, Eruttin, Ichatkin, Kekur, Kukenei, Lunnoe, Mrarnornoe, Mymlerennet,
Telekai, Valkumei, and Vodorazdelnoye; porphyry Sn deposits at Ekug and Pyrkakai; granitoid-related Au deposits at Kanelyvwn
and Kuekvun; porphyry Cu-Mo and porphyry Mo deposits at Granatnoe and Shurykan; Pb-Zn skarn and Fe-Pb-Zn-Sn deposits at
Chechekuyum, Enpylkhkan, Melyul, Reechen, and Serdtse-Kamen; an Au-Ag epithermal vein deposit at Pepenveem; a
disseminated Au-sulfide deposit at Turnannoe; and a clastic sediment-hosted Hg or hot-spring Hg deposit at Yassnoe.
The Sn and associated lode deposits of the Chaun zone are generally hosted in: (1) volcanic rocks and rhyolite
subvolcanic intrusions and extrusions which often have anomalous In and Ag; (2) major plutons of Late Cretaceous leucocratic
biotite granite with K-Ar isotopic ages of 95-70 Ma; and (3) late Early Cretaceous diorite (Kanelyveen deposit). The deposits
generally occur in the apical parts of the granitic intrusions and in the intrusive domes. The typical deposit minerals are quartz,
tourmaline, chlorite, and sulfide minerals. In western Chukotka, the significant deposits are at Vakumei, currently being mined,
and at Pyrkakai, Ekug, Telekai, and Kukenei, and a possible granitoid-related Au deposit at Kanelyveen. In eastern Chukotka,
significant Sn-Ag skarn and polymetallic vein deposits at Chechekuyum, Reechen, a d Enpylhkan are hosted in Paleozoic
carbonate rocks.
Also part of the Chaun zone of felsic-mamatism-related deposits is a group of Sn and complex Sn-W polymetallic vein,
minor associated Sn greisen deposits which occur in middle Paleozoic and early Mesozoic sandstone, argillite, and rare carbonate
rocks of the Chauna subterrane (fig. 79). The polymetallic lode deposits are closely associated with Early and mid-Cretaceous
anatectic, leucocratic, potassic granitoid plutons. The main Sn-W vein deposits occur to the east in the Iultin ore district. The
Iultin, Svetloe, Chaantal, Tenkergin, and associated deposits of this district contain the most of the inferred tungsten reserves for
the region, and the Iultin and Svetloe deposits produce all of the tungsten and by-product tin in the Russian Northeast.
lultin Sn-W Polymetallic Vein and Greisen Deposit
The Iultin Sn-W polymdallic vein and greisen deposit (fig. 97) (Zilbermints, 1966; Lugov, Makeev, and Potapova, 1972;
Lugov, 1986) consists of quartz veins, mineralized stockwork zones, and disseminated veinlets hosted in greisen. The stockwork
zones and veinlets are both steeply-dipping and gently-dipping. Some ore bodies wedge out vertically. The W ore bodies occur
over the top of a leucogranite pluton which is about 300 m below the surface; and the So ore bodies occur in he marginal zone of
the leucogranite. Approximately 65 minerals are known with the most common being quartz (95%), muscovite, fluorite, albite,
cassiterik, wolfiamite, arsenopyrite, and ltiellingite. Less common are topaz, pyrite, pyrrhotite, bismuthinite, stannite.
chalcopyrite, sphalerite, galena, molybdenite, scbeelite, hematite, and native silver and bismuth. Cassiterite is commonly
associated with wolframite, arsenopyrite, and muscovite. Cassiterite occurs as short, columnar crystals up to 10 cm across. Large
(up to 4-9 cm) and gigantic (up to 0.5 m) wolfiamite crystals and crystal intergrowths are present. The vertical extent of the ore
bodies exceeds 900 m. The deposit occurs along the contact of the mid-Cretaceous Iultin granite with a K-Ar age of 90-1 10 Ma
which intrudes and contact metamorphosed and metasomatizes Early and Late Triassic sandstone and shale. The biotite granite has
a Rb-Sr isotopic age of 85.1 Ma with an initial Sr ratio of 0.7088 (Dudkinsky and others, 1986). The late stage of the lultin
intnrsive complex consists of leucocratic granite with a Rb-Sr isotopic age of 76.3 Ma and an initial Sr ratio of 0.7 17. The deposit
is large and has been mined since 1959 with an average grade of 0.43% Sn and 1.29% WO,. The Iutin deposit has produced
significant W and Sn in past years, but is now inoperative.
SveUoe Sn-Qua* Vein Deposit
The Svetloe Sn-quartz vein deposit (Lugov, 1986; Kuleshov, Pristavko, and Plyashkevich, 1988) consists of en-echelon
sets of quartz veins and veinlets which form two zones which diverge to the southeast. Each zone contains several tens of larger
veins which vary from 0.2 to 1.5 m thick and are several hundreds of meters long; and about one hundred smaller veins. The ore is
dominated by Sn minerals with abundant sulfide minerals which occur over a buried stock of greisenized granite. The veins are
hosted in metamorphosed Triassic sandstone and shale and are cut by granite porphyry and aplite dikes of the Cretaceous Iultin
complex. Successive mineral assemblages are: (1) topaz-fluorite-muscovite greisen; (2) cassiterite-wolframite-quartz assemblage
with topaz, IOellingite, and fluorite (the most productive assemblage); (3) arsenopyrite-quartz with cassiterite and native bismuth;
(4) stannite-chalcopyrite with small amounts of bismuhite, sphalerite, galena, pyrrhotite, and bornite; (5) scheelite-fluorite-
albite with ch-lorite, pyrite, marcasite, and cassiterite; and (6) fluorite-calcite with kaolinite. A complex cassiterite-wolfiamite
t q.+
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