Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

1993). This compression is relieved by extrusion of the Okhotsk block to the southeast (Riegel and others, 1993) and by uplift and
thrusting in the CSB area (Koz'min, 1984; Imaev and others, 1990; Koz'min and others, 1996). Sedimentation continues in the
Amerasia basin (ab).
. + t *
+ * + + *
+ + * + + + +
4 + + + + * * + + +
+ * + + +
+ ......
COLLAGE OF
RIFTED TERRANES
AP -Alaska Pen~nsula and
Aleut~an Islands
OC - Owl Creek
SH - Sakhal~n Island
Figure 128. Late Tertiary and Quaternary (Pliocene through present - 4 to 0 Ma) stage of metallogenic-tectonic model. Refer to text
for explanation of metallogenic-tectonic events, to tables 3 and 4 for descriptions metallogenic belts and significant deposits, and to
figure 18 for explanation of abbreviations, symbols, and patterns. Adapted from Nokleberg and others (1997b, 1998, 2000).
(3) Seismicity defines several new tectonic blocks, including the b ur, Okhotsk, and Bering blocks (Riegel and others,
1993; Fujita and others, 1997; Mackey and others, 1997). Boundaries between blocks are defined by epicenters located by
teleseismic and regional networks (Fujita and others, 1997).
(4) Marine and continental eruption of sparse, generally small, highly dispersed flows of Bering Strait alkaline basalt (bs)
occurred in the Quaternary and Recent. This volcanism may possibly be related to dextral-wrench faulting and tectonic escape in
this region. Rotation of the Bering block created extension on the Seward Peninsula and on Chukotka (Mackey and others, 1997),
or the Bering block may have formed as the back-arc with respect to the Aleutian-Wrangell arc.
(5) Tectonic escape (crustal extrusion) of terranes continues along major dextral-slip faults, including the Denali (DE),
Nixon Fork (NF), Kaltag (KA), and companion faults (Scholl and others, 1992, 1994) which may extend into the Bering Sea.
Dextral-wrench basins continue to form in association with the dextral-slip faults and are still filling with continental sediments. A
thick sedimentary prism continues to form in the Aleutian-Bowers basin (atb; Plafker and Berg, 1994). In Interior and Southern
Alaska, displacement continues along major dextral-slip faults, such as the Denali (DE) fault.
(6) The Pacific Ocean plate (PAC) continues to move northwestward relative to the North American plate. Along the
Aleutian megathrust (AL), plate convergence continues to vary from orthogonal in the east to oblique to transform in the west.
(7) lntense tectonic disruption continues in the western part of Aleutian-Wrangell arc along the western Aleutian
megathrust (AL), as a result of the transform coupling between the Pacific Ocean plate (PAC) and the North American plate (Geist
and others, 1988; Scholl and others, 1992, 1994). A thick sedimentary prism continues to form in the Aleutian-Bowers basin (atb)
which overlies a fragment of accreted Kula Ocean plate (Plafker and Berg, 1994).
(8) Along the margin of Southern Alaska, the eastern part of the Aleutian-Wrangell arc continues activity. Associated
with the arc is mainly oblique subduction of the northern edge of Pacific Ocean plate (PAC) along the Aleutian megathrust (AL),
continuing the formation of the younger part of the Prince William terrane (PW). Continuing in the Aleutian-Wrangell arc is the
Alaska Peninsula and Aleutian lslands (AP) metallogenic belt which contains granitic-magmatism-related deposits and is hosted in