Structural-dynamic relationships between the East Sikhote Alin volcano-plutonic belt and its folded basement

Abstract

The East Sikhote Alin volcanoplutonic belt (ESAVB) extending along the coasts of the Sea of Japan and Tatar Strait is over 1000 km long and 35‐40 km wide on average. Similar to other elements of the East Asian volcanic belt, the latter represents a structure with the continuous development mode being superimposed or crossing protostructures of the eastern margin of the Asian continent regardless of their types and ages. The study of structural‐dynamic relationships between the basement that existed during synchronous dislocations and superimposed volcanic complexes reveals the geodynamic formation conditions of volcanic belts. The East Sikhote Alin volcano-plutonic belt was formed in the Late Cretaceous‐Paleogene. It is composed of sedimentary‐volcanogenic and volcano-plutonic rocks resting unconformably upon the folded basement represented largely by Lower Cretaceous terrigenous strata deformed into a system of open and isoclinal folds with a dominant northeastern strike (azimuth 40 ° ‐60 ° ) and complicated by imbricate updip‐ thrusts. In contrast to the basement, no dominant regional folded and dislocated systems were defined in volcanics during mapping. They demonstrate only fragments of folded‐bedded structures with variable strikes and dip angles as well as numerous fractures also oriented differently (largely, normal faults), the formation of which is thought to be related to local stresses during volcanoplutonic magmatism. Most researchers share the opinion that volcanics represents a superposed complex with its own dislocation type independent from tectonics of the Early Cretaceous folded basement. The discovery of a system of NNE-trending sinistral strikeslip faults with displacements amplitudes in the Late Cretaceous amounting to a few tens of kilometers made it possible to infer that the East Sikhote Alin volcanoplutonic belt was formed in response to Late Cretaceous activation of strike-slip faults [2‐4]. Such geodynamic conditions should result in the formation of ensembles of regularly oriented both folded structures and fractures characteristic of rocks overlying active strike-slip faults. This makes it crucial to study structures that developed in Late Cretaceous volcanics presumably in response to displacements along strike-slip faults.