Shear destruction of the East Asian margin and its role in the formation of volcano-plutonic belts, epicontinental sedimentary basins, and marginal seas

Abstract

The spatial‐temporal and genetic relations between the formation of volcano-plutonic belts and the development of the East Asian global shear zone in the Cretaceous‐Cenozoic was first demonstrated in [5, 7‐9]. Subsequently, many researchers paid attention to strike-slip faults as a factor of tectonic evolution of the Asian margin. In the context of plate tectonics, the East Asian global shear zone was defined as reflecting the transform regime of the margin [11]. This gave birth to ambiguously solved problems, two of which are principally important: (1) Injection of magmas that formed the East Asian volcanic-plutonic belt was determined by the replacement of the transform (shear) geodynamic regime by the subductional one in the Late Cretaceous or perhaps this resulted from shear destruction of the Asian margin? (2) The formation of epicontienntal sedimentary basins and deep marginal seas was determined by the mantle diapirs or perhaps these processes, the local rise of the mantle included, were also a consequence of shear extension of the crust? The East Asian global shear zone initiated in the Early Mesozoic and developed in a discrete‐continuous manner until the Cenozoic with the dominant leftlateral displacement (Fig. 1) [7‐9, 14]. According to plate tectonics, the transform (shear) geodynamic regime of the Asian margin was replaced in the Late Cretaceous by the subductional regime. It is believed that subduction of the oceanic plate under the continent resulted in opening of extended NE-trending faults oriented orthogonally relative to the subduction direction, which was responsible for the formation of the East Asian volcanic-plutonic belt. These views are inconsistent with some geological facts, primarily the continuing activity of left-lateral strike-slip faults in the Late Cretaceous. In the Sikhote Alin mountainous system, Lower Cretaceous sequences, its uppermost layers with the middle‐late Albian trigonid fauna included [9], were displaced for a few tens of kilometers along a system of NE-trending left-lateral strike-slip faults extending parallel to the Central Sikhote Alin strike-slip fault. The activation of the left-lateral strike-slip faults in the Cenomanian‐Paleocene stimulated formation of WNW-oriented volcano-plutonic structures (Fig. 2), which crossed the pre‐Late Cretaceous folded complex. The latter served as conduits for magma, and their magma formed the volcanic cover dislocated conformably with formations overlying active left-lateral strike