USGS Professional Paper 1697 - Alaska Resources Library

y partly coeval plutons that range in age from 130 to 94 Ma
(Nokleberg and others, 1994c, 1997c; Monger and Nokleberg,
1966). The arc-related, calc-alkaline volcanic and sedimentary
rocks of the Gambier Group overlie Jurassic and older plutonic,
volcanic, and sedimentary rocks of the Coast Plutonic Complex
and Harrison terrane on the east and Middle to Late Jurassic
plutons of Wrangellia Superterrane on the west. The Gambier
Group and coeval plutonic rocks are part of the extensive
South Arm Molra Sound
0 2 km
Biotite aplite, aplite, and pegmatite
Fine-grained aegirine granite
Riebeckite-aegirine grantite
Aegirine granite
Border-zone pegmatite
Quartz monzonite
Quartz diorite
Bokan Mountain
Normal facies
Heterogeneous zones
Undifferentiated sedimentary rock
Undifferentiated sedimentary and
volcanic rock
Radioactive dike
Contact
Fault
Bokan
Mountain
Granite
(Jurassic)
Country
Rock
West Arm Kendrick Bay
Figure 71. Bokan Mountain felsic plutonic uranium and rareearth
element (U-REE) deposit, western-southeastern Alaska
metallogenic belt, southeastern Alaska. Schematic geologic map.
Adapted from Warner and Barker (1989) and Foley and others
(1997). See figure 62 and table 4 for location.
Late Early Cretaceous Metallogenic Belts (120 to 100 Ma; figs. 61, 62) 159
Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary belt,
which forms a major middle Mesozoic sequence of volcanic,
sedimentary, and plutonic rocks deposited on and intruded into
the Wrangellia superterrane. The belt is interpreted as an elongate
island arc that extended for several thousand km along the inner
margin of the Wrangellia superterrane (sheet 3; Nokleberg and others,
1994c, 1997c). This Middle Jurassic to Early Cretaceous island
arc, which was built on the Wrangellia superterrane, is interpreted
as forming immediately before accretion of a of the superterrane
to the accretionary margin of the North American Cordillera
in the mid-Cretaceous (Monger and others, 1994; Monger and
Nokleberg, 1996; Nokleberg and others, 2000). The volcanic
exhalative activity deposited Kuroko-type massive sulfides in
several centers in the Gambier Group. Mineral deposits and
their host rocks were sheared and attenuated along faults active
during and after the accretion of the Wrangellia superterrane.
Late Early Cretaceous Metallogenic
Belts (120 to 100 Ma; figs. 61, 62)
Overview
The major Late Early Cretaceous metallogenic belts in
the Russian Far East, Alaska, and the Canadian Cordillera are
summarized in table 3 and portrayed on figures 61 and 62.
Six major belts are identified: (1) In the Russian Southeast,
the Badzhal-Ezop-Khingan (BZ-KH) belt of granitic-magmatism-related
deposits, which is hosted in the Khingan-Okhotsk
volcanic-plutonic belt, is interpreted as forming in the Khingan
continental-margin arc. (2) In the Russian Southeast, continuing
on frm the Early Creteacoues was the Samarka (SA) belt of granitic-magmatism-related
deposits. (3) In the Russian Northeast,
continuing on from the Early Cretaceous, was the Kular (KU)
metallogenic belt, which contains Au quartz vein and graniticmagmatism-related
deposits. (4) Also in the Russian northeast
was the Anadyr River (AD) metallogenic belt of Au quartz
vein deposits, which is hosted in the Mainitskiy, West Pekulney,
and (or) Penzhina-Anadyr terranes. The belt is interpreted
as forming during regional metamorphism and generation of
hydrothermal fluids associated with accretion and collision of
Mainitskiy island arc onto North Asian Craton margin. (5) In
Northern Alaska, the Nome (NO) and Southern Brooks Range
(SBR) belts, which contain Au quartz vein deposits, are hosted
in metamorphosed continental-margin terranes and are interpreted
as forming during regional metamorphism associated
with extension that occurred after overthrusting of Angayucham
subduction-zone terrane. (6) In the northern Canadian Cordillera,
the Fish River (FR) metallogenic belt, which contains
stratabound sedimentary P and Fe deposits and is hosted in the
North American Craton Margin, is interpreted as forming during
Late Mesozoic, dextral movement along the Kaltag-Porcupine
fault system. (7) In the Canadian Cordillera, continuing on
from the Early Cretaceous was the western-southeastern Alaska
(WSE) belt, which contains granitic-magmatism-related depos-