Home – Home – Jornals – Russian Geology and Geophysics 2020 number 10

The evolution of the eastern part of the Mongol-Okhotsk Orogenic Belt marks the late Mesozoic accretion-collision processes involving the Siberian and Sino-Korean plates. Tectonic restructuring in the region was accompanied by the formation of igneous complexes, which replaced each other almost without a temporal break. Andesitic magmatism was widely manifested in the southern framing of the eastern part of the belt. Its study is complicated by the isolation of volcanic fields and their confinement to the Amur-Zeya depression. Study of the geochemical and geochronological characteristics of igneous complexes there made it possible to recognize and systematize the temporal stages and substantiate the geodynamic formation of these rocks. However, there are controversial geologic objects, such as the Isikan volcanic field. We present the first data on the isotopic age and chemical and isotope-chemical compositions of the rocks of this field. ⁴⁰Ar/³⁹Ar dating showed that the integrated age of the dacitic matrix is 113.0 ± 2.6 Ma and the plateau age is ??121.0 ± 1.6 Ma. In chemical composition the studied volcanic rocks are similar to rocks of the Poyarkov volcanic complex developed within the Bureya-Jiamusi superterrane, which formed under subduction in the period 120-105 Ma. In geochemical and isotope-geochemical characteristics the volcanics are similar to rocks of igneous belts of Andean-type active continental margins.