Lateral Zonality of the East Sikhote-Alin Volcanic Belt: Geodynamic Regime in the Late Cretaceous

Resumo

The East Sikhote Alin volcanic belt (~1500 km long) is commonly regarded as a tectonomagmatic structure formed in the Late Cretaceous in a subduction environment, which was followed by the destruction of the oceanic slab and active asthenospheric diapirism in the Cenozoic. However, the nature of the lateral zonality of the Late Cretaceous volcanic complexes, which is distinctly expressed in a number of geological and metallogenic parameters, remains poorly studied. In this paper, this issue is considered on the example of the poorly studied Late Cretaceous Bolbinsk Formation of northern Sikhote Alin. Analysis of the published geological information in combination with geochronological, trace-element, and isotopic data indicates that the structure was developed in a non-subduction geodynamic setting. The predominance of magnesian (Mg# = 26–40) adakites (La/Yb = 19–34) and high-niobium basalts and low lead (Δ8/4Pb = 30–46) and high neodymium (¹⁴³Nd/¹⁴⁴Nd 0.51279–0.51281) isotopic ratios suggest an elevated permeability of the subducted slab and injection of a “hot” oceanic asthenosphere into the mantle wedge. Consequently, the lateral geological, geochemical, and metallogenic zonality of the East Sikhote Alin volcanogenic belt was formed at the early stages of its evolution as a result of the specific configuration of the Late Cretaceous continental margin.