USGS Professional Paper 1697 - Alaska Resources Library

Peschanka Porphyry Cu-Mo Deposit
The Peschanka porphyry Cu-Mo deposit (fig. 53)
(Gorodinsky and others, 1978; Volchkov and others, 1982;
Kaminskiy and Baranov, written commun., 1982; Migachev
and others, 1984; V.V. Gulevich and others, written commun.,
1993) occurs in the eastern portion of the Late Jurassic to Early
Cretaceous Egdegkych multiphase pluton that is composed
of monzodiorite and quartz monzodiorite that are intruded by
planar bodies of quartz monzonite and granodiorite porphyry.
The deposits consists of sulfide veinlets and disseminations
with pervasive Cu and Mo minerals that occur throughout the
entire elongated quartz monzonite and granodiorite porphyry
body and that extend into the wall rock. The main ore minerals
are pyrite, chalcopyrite, bornite, tetrahedrite-tennantite, and
molybdenite. Minor or rare minerals are magnetite, hematite,
sphalerite, galena, chalcocite, native gold Au-tellurides,
enargite, arsenopyrite, pyrrhotite, and marcasite. The gangue
minerals are quartz, carbonate, and anhydrite. Four mineral
associations occur—(1) molybdenite, which is associated with
the quartz-sericite subzone of phyllic alteration, (2) pyrite and
chalcopyrite that are associated with quartz-sericite-chlorite
Figure 52—Continued.
Late Jurassic Metallogenic Belts (163 to 144 Ma; figs. 48, 49) 119
alteration, (3) chalcopyrite, bornite, and tetrahedrite, which
are associated with quartz-sericite and biotite alteration, and
(4) polysulfide minerals, which occur with all alteration types.
Mineralization was preceded by wide-spread pyritization in the
peripheral propylitic zone. The deposit contains an estimated
resource of 940 million tonnes with an average grade 0.51 percent
Cu, 0.019 percent Mo, 0.42 g/t Au, and 1.4 g/t Ag.
Vesennee Au-Ag Epithermal Vein Deposit
The Vesennee Au-Ag epithermal vein deposit (Gorodinsky
and others, 1974; Shilo and others, 1975; Shapovalov,
1976; Sidorov, 1978; V.V. Gulevich and others, written
commun., 1993) consists of carbonate-quartz veins, altered
veinlets, and mineralized breccias that occur in structurally
complex forms. The veins are controlled by northeast- and
approximately east-west-trending fractures that cut northwesttrending
zones of associated granitoid rocks. Individual ore
bodies range from 150 to 500 m long. The ore minerals are
sphalerite, galena, pyrite, chalcopyrite, tetrahedrite, tennantite,
bournonite, and electrum, with minor Ag-sulfides and sulfosalts,
stannite, and matildite. The main gangue minerals are