The early Paleogene strike-slip tectonic setting along the northeastern Asian margin: structural control on magmatism

Various types of early Palaeogene calderas indicating transtensional (strike-slip fault-related extensional structure and extensional strike-slip duplex) and transpressional (contractional) structures have been identified in southern Sikhote-Alin (northeastern Asia). These volcanic structures formed due to the NNW-oriented (345–355°) stress during left-lateral displacements within a zone of dynamic interaction between the main tectonic units of the territory: the Central Sikhote-Alin and Vostochny Faults. These faults form a large-scale fault zone, where strike-slip displacements and magmatic activity propagated from boundary faults to the central area of the fault zone. The analysis of regional faulting morphology and kinematics within this fault zone and its vicinity shows that the NNE-trending strike-slip faults bend into NE-trending thrust zones on its southern and northern flanks. These changes reveal a regional S-shaped structure that we named the ‘sinistral kink band of southern Sikhote-Alin’. The activation of the subparallel NNE-trending sinistral faults in the central part of the kink band accounts for the increased permeability of the basement and terrigenous strata. The early Palaeogene magmatic activity should be regarded as a marker of left-lateral displacements from at least ~61–55 Ma due to oblique interactions between continental and oceanic plates along the northeastern Asian margin.