Abstract

We present new U–Pb age data for granitoids in the Central Sikhote–Alin orogenic belt in SE Russia, which refute the established opinion about the absence of the Late Cretaceous magmatism at the eastern margin of the Palaeo-Asian continent. It was previously thought that a period of magmatic quiescence occurred from 88 to 50 Ma, related to subduction of the Palaeo-Pacific plate under the eastern margin of the Palaeo-Asian continent, although this is inconsistent with evidence from the Sikhote–Alin, Sakhalin and Japan regions. Three suites of plutonic rocks with different ages were identified in this study. The first suite has ages of 105–92 Ma and formed in a syn-orogenic setting. The second (86–83 Ma) and third (c. 73 Ma) suites formed during the post-orogenic stage of the Sikhote–Alin orogenic belt. The second and third suites were coeval with Late Cretaceous granitoids that formed in a supra-subduction continental arc known as the Eastern Sikhote–Alin volcanic–plutonic belt. However, the studied rocks are located far inland from the Eastern Sikhote–Alin volcanic–plutonic belt. The ages of the studied granitoids coincide with the timing of a change in the angle of convergence between the Palaeo-Pacific plate and eastern margin of the Palaeo-Asian continent. This change in motion of the oceanic plate with respect to the continental plate was probably caused by a rupture in the subducted slab (i.e. a slab tear), followed by asthenospheric upwelling and partial melting of the overlying crust, which ultimately generated post-orogenic intrusive magmatism.

Supplementary material: Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb data of the Bikin–Bol. Ussurka granitoid suites are available at https://doi.org/10.6084/m9.figshare.c.5738616