South Anyui suture: tectono-stratigraphy, deformations, and principal tectonic events

Abstract

Abstract. Geochronologic and structural data from the terranes of the South Anyui suture zone record a protracted deformational history before, during and after an Early Cretaceous collision of the passive margin of the Chukotka-Arctic Alaska continental block with the active continental margin of the North Asian continent. Preceding this collision, the island arc complexes of the Yarakvaam terrane on the northern margin of the North Asian craton record Early Carboniferous to Neocomian ages in ophiolite, sedimentary, and volcanic rocks. Triassic to Jurassic amphibolites constrain the timing of subduction and intraoceanic deformation along this margin. The protracted (Neocomian to Aptian) collision of the Chukotka passive margin with the North Asian continent is preserved in a range of structural styles including first north verging folding, then south verging folding, and finally late collisional dextral strike slip motions which likely record a change from orthogonal collision to oblique collision. Due to this collision, the southern passive margin of Chukotka was overthrust by tectonic nappes composed of tectono-stratigraphic complexes of the South Anyui terrane. Greenschists with ages of 115-119 Ma are related to the last stages of this collision. The postcollisional orogenic stage (Albian to Cenomanian) is characterized by sinistral strike slip faults and an extensional environment.

Fold belts and sedimentary basins of the Eurasian Arctic

“…5). Many data on SASZ geology were published by Parfenov and Natal'in [110], Sokolov et al [152][153][154], Amato et al [1]. The suture is exposed onshore in Western Chukotka where it is composed of a complexly deformed package of tectonic nappes thrusted southward onto the adjacent margin of the KOCST as revealed by seismic refraction data [1,44] [38,154] ophiolites.…”

“…The suture is exposed onshore in Western Chukotka where it is composed of a complexly deformed package of tectonic nappes thrusted southward onto the adjacent margin of the KOCST as revealed by seismic refraction data [1,44] [38,154] ophiolites. The rocks are intruded by syn-and post-collisional granodiorites and granites with isotopic ages of 116-105 Ma [1,97,152,153]. Magnetic data allow to extend the SASZ offshore from the Kolyma River mouth to Bol'shoi Lyakhov Island, where dismembered ophiolites and island-arc volcanic complexes are again exposed [24,78].…”

“…The SASZ formed in Late Jurassic-Early Cretaceous (prior to Aptian) time as the result of the closure of the South Anyui-Angaucham Ocean and collision between the AACM and an active continental margin of the North Asian continent represented by the Oloi-Svyatoi Nos magmatic arc [110,138,181]; Sokolov et al [152,153]. The deformation timing is bracketed by the youngest compressionally deformed Hauterivian-Barremian sedimentary rocks, and the oldest 116.9 ± 2.5 Ma [97] granite pluton cross-cutting the deformed rocks.…”

“…The deformation timing is bracketed by the youngest compressionally deformed Hauterivian-Barremian sedimentary rocks, and the oldest 116.9 ± 2.5 Ma [97] granite pluton cross-cutting the deformed rocks. The final collision was accommodated by movements along large WNW to ESE dextral strike-slip faults [153].…”

“…It marks cessation of Late Mesozoic orogeny [23,111,153]; and references therein). All sedimentary successions of the southern AACM domain were severely affected by this Chukotka-Early Brookian deformation.…”