USGS Professional Paper 1697 - Alaska Resources Library

Host Granitoid Rocks and Associated Lode Deposits
Hosting and associated with the lode deposits of the
Yana-Kolyma metallogenic belt are various collisional plutons
composed of diorite-granodiorite, granodiorite-granite, and
granite-leucogranite (Goryachev, Goncharov, 1995, Goryachev,
1998, 2003). The granitoid plutons are interpreted
as forming at various depths. The Late Jurassic and Early
Cretaceous granite-leucogranite plutons form large, homogeneous,
batholith-like intrusions with surface areas as large as
7,000 km 2 . The granitoid rocks occur in an axial portion of the
Yana-Kolyma collision zone and consist of biotite and twomica
granites with accessory sillimanite, andalusite, cordierite
and garnet. High Rb contents are characteristic, the granites
are typical S-type collisional granites that have initial Sr ratios
ranging up 0.7045 to 0.7111 (Goryachev and Goncharov,
1995; Goryachev, 1998, 2003). Small Sn occurrences are associated
with these granites.
Kolyma R.
Quaternary sedimentary rock
Diorite-granodiorite
Granodiorite-granite
Dike
Middle Jurassic
Early Jurassic
Early Jurassic
Au quartz vein deposit
Granitoid-related Au deposit
Contact
Utinka deposit
Late Jurassic and
Early Cretaceous
Sandstone, siltstone,
shale
Early Cretaceous Metallogenic Belts (144 to 120 Ma; figs. 61, 62) 153
Daryal deposit
The Late Jurassic and Early Cretaceous diorite-granodiorite
intrusions form numerous dikes and small stocks that
occur as separate suites in central portions of these zones.
Diorite-porphyries, granodiorite-porphyries, and granite-porphyries
are most prevalent as dikes; stocks are composed of
two and three rock types, from diorite to biotite-amphibole
granodiorite or granite. These igneous rocks are calc-alkaline,
with some predominance of Na over K, locally contain
accessory garnet (as much as 20.5 percent pyrope), and have
initial Sr ratios of 0.7045 to 0.7087 (Goryachev and Goncharov,
1995; Goryachev, 1988, 2003). These granites are typical
I-type granites of the ilmenite-series. Au-quartz vein deposits
are usually associated with these intrusions.
The Early Cretaceous granodiorite-granite intrusions
occur in small plutons (with surface areas as large as 300
km 2 ) in the same area occupied by the diorite-granodiorite
intrusions. The granodiorite-granite plutons are composed of
granodiorite and mostly biotite granite rocks, are characterized
0 10 km
Figure 68. Utinka Au-quartz vein deposit, Yana-
Kolyma metallogenic belt, Russian Northeast. Schematic
geologic map showing geologic setting of the
Utinka lode deposit. Adapted from Goryachev (1998).
See figure 61 and table 4 for location.