USGS Professional Paper 1697 - Alaska Resources Library

dolomite. Wall rock alteration includes weak silicification,
kaolinization, and carbonatization. The deposit is large and
contains an estimated 700 tonnes Hg averaging 1.4 percent
Hg, and as much as 0.4 percent Sb and 4 g/t Au.
Lalankytap Porphyry Mo-Cu Deposit
The Lalankytap porphyry Mo-Cu deposit (Brazhnik and
Kolyasnikov, 1989; Brazhnik and Morozov, 1989) consists of
an oval stockwork about 1.2 by 0.6 km in area that contains
randomly oriented quartz veinlets with irregularly disseminated
pyrite, molybdenite, and chalcopyrite and minor pyrrhotite,
sphalerite, galena, magnetite, martite, rutile, anatase,
and sphene. The ore minerals occur both in the veinlets and in
disseminations. Cu- and Mo-minerals are related to a zone of
quartz-biotite-sericite-pyrite alteration that occurs in a Paleogene
quartz diorite and monzodiorite pluton and in adjacent,
intruded Late Cretaceous flysch. The pluton is bounded by
a nearly east-west zone of pyritized altered rocks more than
11 km long and from 1 to 4 km wide. The deposit is of small
to medium size. Small amounts of gold occur in goethitecemented,
Quaternary alluvial conglomerate near the deposit.
Maletoivayam Sulfur-Sulfide Deposit
The Maletoivayam sulfur-sulfide deposit (Vlasov, 1971,
1976, 1977) occurs at the southern end of the Olyutorka volcanic
belt, in the Miocene Korfovsky Formation. Two occurrences,
lower and upper, are separated by a 10 to 50 m thick
bed of kaolinite-montmorillonite and quartz-kaolinite rocks.
Both occurrences are dip at 5 to 10° with respect to bedding
orientation in the host rocks. The upper ore body can be traced
for 1,800 m along strike, is 80 to 700 m wide, and 3 to 115 m
thick. The ore is disseminated in sulfide-sulfur-alunite silicified
rock and in sulfuric silicified rock, which contains most of
major native sulfur tonnage. The sulfide-sulfur-alunite silicified
rock contains 18 percent S, 30-40 percent alunite, and 10
percent Fe sulfides. The ore contains as much as 30 percent
native sulfur. Native sulfur of 96 to 99 percent purity is separated
using thermal reduction. About 60 percent potassium
sulfate is also separated. The deposit is large and contains as
much as 30 percent S.
Origin of and Tectonic Controls for Olyutor Metallogenic Belt
The East Kamchatka volcanic belt, which hosts the northern
part of the Olyutor metallogenic belt, consists chiefly of a
major chain of modern volcanoes of Pliocene and younger age
(Nokleberg and others, 1994c, 1997c). The main lithologies
are basalt, andesite-basalt, rare dacite, and tuff. The belt is the
northward continuation of modern Kuril volcanic arc, which
started to form in the Neogene.
The Central Kamchatka volcanic belt, which hosts the
central and southern parts of the Olyutor metallogenic belt,
extends for 1,500 km longitudinally the Kamchatka Peninsula
(Sredinny Range). The volcanic belt contains the modern-day
Kamchatka volcanic arc. The belt consists chiefly of thick,
Early to Middle Tertiary Metallogenic Belts (52 to 23 Ma; figs. 102, 103) 269
gently dipping andesite, dacite, and rhyolite strata interlayered
with sandstone, siltstone, and conglomerate, and widespread
large ignimbrite fields (Nokleberg and others, 1994c). The
belt ranges from Oligocene to Holocene age. Shallow-marine
deposits predominate in the lower part and nonmarine deposits
predominate in the upper part. Formation of the belt culminated
with eruptions of Pliocene to Quaternary plateau basalts that
are associated with stratovolcanoes (Filatova, 1988). A minimal
crustal thickness of 27 to 33 km occurs in the region. The
Central Kamchatka volcanic belt is tectonically linked to the
Kuril-Kamchatka accretionary-wedge and subduction-zone terrane
and to the Cenozoic subduction of the Pacific Plate along
the Kuril-Kamchatka megathrust (Nokleberg and others, 2000).
Pinchi Lake Metallogenic Belt of Hg Epithermal
Vein, Sb-Au Vein, and Silica-Carbonate Hg
Deposits (Belt PC), Central British Columbia
The Pinchi metallogenic belt of Hg epithermal vein,
Sb-Au vein, and silica-carbonate Hg deposits occurs in central
British Columbia (fig. 103; tables 3, 4) (Nokleberg and others,
1997b, 1998). The belt is 100 km long, contains 12 or more
Hg mines and prospects, and occurs along the faulted eastern
boundary of Cache Creek terrane with the Stikinia terrane.
Although no known Eocene or Oligocene intrusions exist, the
mercury mineralization is interpreted as early Tertiary in age.
The significant deposits are at Pinchi Lake.
Pinchi Lake Silica-Carbonate Hg Deposits
The Pinchi Lake and smaller Bralorne Takla silica-carbonate
Hg deposits (Armstrong, 1949; Dawson and others,
1991) consist of cinnabar that occurs in a stockwork of thin
quartz veins, replacements, lodes and breccia fillings. The
deposit is hosted in marine limestone and carbonatized ultramafic
rocks that occur in shears along the Pinchi Fault, which
separates the Mississippian to Triassic Cache Creek terrane
from the Late Triassic and Early Jurassic Quesnellia island-arc
terrane. The host ultramafic rocks, chert, argillite, and greenstone
of the Cache Creek ophiolite are intensely altered along
the fault zones to an assemblage of Fe-Mg carbonates, quartz,
mariposite and talc. Mineralization postdated both the Late
Triassic blueschists and Late Cretaceous-early Tertiary conglomerates.
Between 1942 to 1975, estimated production was
6,000 tonnes of Hg. Estimated reserves are 1.1 million tonnes
grading 0.32 percent Hg.
Pinchi Lake District of Sb-Au Vein Deposits
The Sb-Au vein deposits in the Pinchi Lake district occur
in the same geological settings as that of the silica-carbonate
Hg deposits. Both types of deposits exhibit the same, distinctive,
green, silica-carbonate-mariposite or listwanite alteration
assemblage. The Snowbird Au-Sb prospect at Stuart Lake consists
of quartz-stibnite veins in a shear zone of silica-carbonate
minerals. The shear zone occurs in sedimentary rocks of the