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

(5) A major orthogonal junction formed between the western end of Aleutian-Wrangell arc (al) a d Central Kamchah
arc (kc). The western terminus of the Aleutian-Wrangell arc is interpreted as having been obducted onto fhc Karnchatka Peninsula,
thereby forming the Kamchatskiy Mys octanic terrane (too small to depict on fig. 127), which is interpreted as the oceanic base of
the ancestral Aleutian-Wrangell arc, and the Stolbovskoy island-arc terrane (also too s md to depict on fig. 127). which is
interpreted as the older, western part of the arc (Geist and others, 1988, 1994).
Figure 126. Generalized map of mejar middle Terllary through Present metallogenic belts, ovetlap assemblages, and tectonically-
linked subduction-zone or accretionary-wedge terranes for Alaska, Canadian Cordillera, and adjacent offshore areas. Refer to text
for description of metallogenic bdts. Adapted from Nofdeberg and others (1997b, 1998). Refer to figure 60 for explanation.
(6) In the early to middle Miocene, a short apiscde (approximately 22 to 10 Ma) of sea-floor spreading along the
Komandorsky Ridge (KOM) formed a small pair of octaroic phtes which exhibit magnetic anomalies 5 and 6. The spreading
occurred after the marine-arc volcanism in his area which formed the Bowers (bw) and Shirshov (sh) Ridgas in the middle
Eocene and early Miocene.
(7) Intense tectonic disruption occrrrred in the western part of Aleutian-Wrangell arc, along the western Aleutian
megathrust (AL), as a result of he transform coupling between the Pacific and North American plates (Geist and otbers, 1988). A
complex array of strike-slip, extension, and rotation structures formed in this area (Scholl and others, 1992, 1994; Vallier and
others, 1994). In the area of the Bering Sea, a thick sedimentary prism continued to form in the Aleutian-Bowers basin (atb) which
overlies a fragment of accreted Kula Ocean plate (Plafker and Berg, 1994; Scholl and others, 1992, 1994).
(8) Tectonic escape (crustal extrusion) of terranes continued to occur along major dextral-slip faults, including the Denali
(DE), Iditarod-Nixon Fork (NF'), Kaltag (KA), and companion hulk3 (SchoLl and others, 1992,1994). Dextral-wrench basins
continued to form in association with the dextral-slip faults and were rapidly filled with continental sediments. Dextral
displacement continued farther east along major dextral-slip faults such as the Denali (DF), Iditarod-Nixon Fork (NF), and Kaltag
(KA) faults. Estimates of total Cenozoic displacements along tbe Denali and Tintina faults are between 400 and 500 km each
(Nokleberg and others, 1985; Platker and Berg, 1994; Monger and Nokleberg, 1996). These and companion dextral-slip faults
probably extended into the area of the Bering Sea.
(9) The Pacific Ocean plate (PAC) continued to move ~orthwestward. Along the Aleutian megathrust (AL) plate
convergence continued to vary from oblique-orthogonal in &he east to obtique to transform in the west.