Age of volcanic-sedimentary complex from Сape Svyatoi Nos (Eastern Arctic)

Abstract

Geological structure and age of the volcanogenic-sedimentary complex of the Cape Svyatoi Nos (Svyatonosskaya formation) are presented. The rocks of Cape Svyatoi Nos are located on the border of the Novosibirsk-Chukotka and Verkhoyansk–Kolyma fold belts, on the coast of the Laptev and East- Siberian Seas. Field studies indicate that the rocks belong to a single volcanogenic-sedimentary complex. The maximum thickness of individual sections reaches up 700 m. Coarse-grained pyroclastic rocks with rare lava flows prevail on the north (on the coast of Laptev Sea). The proportion and dimension of volcanics and pyroclastic rocks decrease in the south, terrigenous rocks appear. In the modern structure, the rocks are deformed.Zircons of several populations were separated from the flow of basalts. Two, the most representative zircon populations are characterized by close subconcordant ages. The structure and U-Pb ages of zircons from the first population suggest their formation during magmatic crystallization with a superimposed postmagmatic thermal event. Zircons of the second population have a xenomorphic appearance, which is typical of zircons formed at the late or postmagmatic phases. The weighted average age (MSWD = 3) of the first two populations is 149.3 ± 1.2 Ma (Tithonian age). It corresponds to the age of crystallization of basalts and the superimposed (close in time) postmagmatic thermal event.The third population of zircons is represented by two rounded grains with Archean U-Pb ages. It is assumed that these grains were trapped by magmatic melt from pre-Jurassic clastic rocks.Late Jurassic-Early Cretaceous radiolarians were identified from different horizons of tuff-terrigenous and terrigenous rocks. This is confirm the obtained U-Pb ages and the coeval of all the studied sections. The Titonian age of volcanic-sedimentary rocks allows us to classify them as suprasubduction complexes of the Late Jurassic - Early Cretaceous, widespread in the Verkhoyansk-Chukotka Mesozoids.