USGS Professional Paper 1697 - Alaska Resources Library

188 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
consist of disseminations and veinlets in and near the intrusive
rocks and coeval volcanic rocks, which often contain notable
amounts of Pb, Zn, W, Au, and Ag in addition to Cu and Mo.
The deposits occur in Late Cretaceous to Paleogene granitic
and diorite intrusions. A porphyry Cu deposit occurs in the
southern part of the belt at Nesterovskoe. In the western part
of the belt, in the eastern part of the adjacent Luzhkinsky terrane,
are porphyry Sn deposits, as at Mopau.
Glinyanoe Ag Epithermal Vein Deposit
The rich Glinyanoe Ag epithermal vein deposit (A.N.
Rodionov, written commun., 1986) consists of adularia-quartz,
sericite-chlorite-quartz, and carbonate-chlorite-quartz mineralized
veins and zones that contain pyrite, arsenopyrite, galena,
sphalerite, chalcopyrite, argentite, acanthite, Ag-tellurides,
and native gold and silver. The veins and zones occur in
altered, silicified volcanic rocks that overlie Late Cretaceous
(Santonian) felsic volcanic rocks. The deposit is interpreted
to have occurred in four stage—(1) gold-pyrite-quartz, (2)
quartz-hydromica and quartz-carbonate, (3) gold-silver, and
(4) quartz-chlorite-adularia with Ag-sulfosalts. The age of the
deposit is interpreted as Late Cretaceous to Paleogene. The
deposit is judged to be small. Average grades are 8.3 g/t Au
and 122 g/t Ag.
Sukhoi Creek Porphyry Cu-Mo Deposit
The Sukhoi Creek porphyry Cu-Mo deposit (Petrachenko
and others, 1988) consists of stockworks that reach several
hundred m across, and in altered zones. Polymetallic ore dominates
in some stocks. The ore minerals are chalcopyrite, molybdenite,
sphalerite, galena, cassiterite, scheelite, and pyrite; with
significant Au and Ag contents. The deposit occurs in Early
Cretaceous sedimentary rocks that are overlain by Late Cretaceous
volcanic rocks and are crosscut by ore-bearing granitic
intrusions with a K-Ar isotopic age of 73 Ma. The Porphyry
Mo mineralization is related to several granodiorite and granite
stocks that are intensely hydrothermally altered. Quartz-sericite
alteration and medium-temperature epidote-prehnite-chlorite
propylitic alteration occur at the core and grade into micaceous-chlorite-carbonate
propylite at the periphery. The granite
is locally altered to quartz-muscovite greisen with tourmaline
and sphene, and in a few places into a peculiar garnet-phlogopite
rock with apatite. The host siltstone and sandstone are
altered to orthoclase-actinolite-chlorite hornfels and the felsic
extrusive rocks are altered to quartz and phyllite. Average Cu
and Mo contents are low, as much as 0.2 and 0.01 percent
respectively. The deposit is not explored at depth.
Tayozhnoe Ag Epithermal Vein Deposit
The Tayozhnoe Ag epithermal vein deposit (A.N. Rodionov
and others, written commun., 1976; Pakhomova and
others, 1997) consists of steeply dipping quartz veins that
occur along northwest to north-south fractures that cut coarsegrained,
Early Cretaceous sandstone. The veins are 100 to 500
m long and 0.5 to 2 m thick, and also occur laterally under the
contact between sandstone and overlying 50-m-thick section
of Late Cretaceous felsic volcanic rocks. The ore minerals
occur within the veins, and in metasomatic zones along the
sub-horizontal contact between veins and overlying volcanic
rocks. The major Ag-bearing minerals are Ag sulfosalts and
sulfides. Pyrite and arsenopyrite are rare and formed before
Ag-bearing minerals. In the upper part of veins, Ag occurs in
tetrahedrite, freibergite, stephanite, pyrargyrite, and polybasite.
At middle depths, Ag occurs in acanthite and stephanite,
along with lesser arsenopyrite and allargentum also occur;
and acanthite dominates at depth. The deposit is medium size
with an average grade of 50 to 2,000 g/t Ag and 1 g/t Au. The
deposit has been mined since the 1980’s and is assumed to be
related to a Paleocene rhyolite volcano-plutonic assemblage.
Verkhnezolotoe Porphyry Cu Deposit
The Verkhnezolotoe porphyry Cu deposit (Orlovsky and
others, 1988) occurs at the northwest margin of a caldera that
contains dike-like bodies of calc-alkaline andesite porphyry
that is interpreted as tongues of a dome-like subvolcanic
intrusion. A stockwork occurs in a circular aureole of hydrothermally
altered rocks, with dimensions of 200 m2 , occurs
over the intrusive dome. Successive alterations consist of (1)
quartz-biotite-actinolite with pyroxene and epidote, (2) quartzbiotite-actinolite,
(3) quartz-biotite-sericite and local chlorite,
and (4) quartz-hydromica with carbonate. The stockwork
includes the first three alterations and consists of a thick network
of quartz-epidote-actinolite veinlets and lenses as much
as 2 to 3 cm thick with chalcopyrite, bornite, and pyrite. The
stockwork is related to a diorite stock. The stockwork boundary
coincides with the aureole of the biotite alteration. An
intensely fractured breccia of mineralized siliceous siltstone
was encountered by drill holes that extend to 100 m depth.
The ore minerals in breccia zones are chalcopyrite, bornite,
molybdenite, pyrite, rarely pyrrhotite, cubanite, arsenopyrite,
galena, and sphalerite. Carbonate-chalcopyrite veinlets also
occur. A zone of oxidized ore as much as 20 to 30 m deep caps
the deposit. The deposit is small with average grades of 3 g/t
Au, 86 g/t Ag, 0.35 to 2.27 percent Cu, 0.69 percent Pb, and
0.26 percent Sn.
Origin of and Tectonic Controls for Kema Metallogenic Belt
The Cretaceous granitoid rocks hosting the Kema metallogenic
belt are part of the East Sikhote-Alin volcanic-plutonic
belt of Late Cretaceous and early Tertiary age (fig. 79) that is
described in the above section the origin of the Taukha metallogenic
belt. Other related, coeval metallogenic belts hosted
in the East-Sikhote-Aline volcanic belt are the Luzhkinsky,
Lower Amur, Sergeevka (SG), and Taukha (TK) belts (fig.
79; tables 3, 4). In the Kema metallogenic belt, the Cretaceous
granitoid rocks of the East Sikhote-Alin belt intrude the
Kema island-arc terrane that consists chiefly of distal turbidite
deposits, andesite and basalt flows, breccia, tuff, and interbedded
shallow-marine volcaniclastic rocks that contain Aptian