Structural assemblies and age of deformation in the western sector of the Anyui-Chukotka Fold System,Northeastern Asia |
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Authors: | S M Katkov E L Miller J Toro |
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Institution: | 1.Geological Institute,Russian Academy of Sciences,Moscow,Russia;2.Stanford University,Stanford,USA;3.West Virginia University,Morgantown,USA |
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Abstract: | Indications of intense deformation in the Anyui-Chukotka Fold System and the South Anyui Suture Zone have been noted for a
long time 3, 5, 19, 36]. The character and age of the deformation, however, remain a matter of debate. Using structural paragenetic
and deformational kinematic analyses, we establish three deformation stages in the Anyui-Chukotka Fold System. The structural
assembly comprising open folds and NW-trending axial-plane cleavage was formed during the stage of regional compression (D1) related to the collision of the Chukotka-Arctic Alaska microcontinent with Eurasia. The assembly of the second stage in
the Alyarmaut Rise is distinguished by isoclinal folds F2, gently dipping metamorphic schistosity, and pervasive cleavage in combination with folded quartz veins and lenses. Planar
structural elements of the second stage are disturbed by low-amplitude normal and reverse faults and kink folds of stage D3. The U-Pb (SHRIMP-RG) and 40/39Ar methods were used for determination of the isotopic age of the deformations. The Aptian-Albian zircon age (117–108 Ma)
has been established for six postcollision granitic plutons of the Anyui-Chukotka Fold System and the South Anyui Suture.
Syncollision deformation completed 125–117 Ma ago. The extensional tectonic stage D2 accompanied by emplacement of the Lyupveem pluton occurred 120–105 Ma ago. The 40/39Ar age of the biotite from the metamorphic rocks marks the age of syndeformation metamorphism (109–103 Ma). The lower limit
of brittle failure and deformation D3 is estimated at 105 Ma. |
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