Okhotsk-Chukotka Volcanogenic Belt Research Articles

Late Early–Late Cretaceous floras of the North Pacific Region: florogenesis and early angiosperm invasion

During the early–middle Albian, a single uniform flora existed in the North Pacific Region. In the middle Albian, structural and landscape modification of the region resulted in its subdividing into several floristic-palaeogeographic subregions. Latest Albian and Late Cretaceous floras of coastal plains of North-eastern Asia and Alaska were dominated by angiosperms, whereas within the Asiatic continental interior depressions and the highlands of the Okhotsk–Chukotka volcanogenic belt angiosperm-dominated floras coexisted with floras dominated by ferns and gymnosperms. The observed phenomenon can be explained by the early angiosperm ability to colonise disturbed coastal plain environments due to their abbreviated reproductive cycle and generalised methods of pollination and seed dispersal. In North-eastern Asia and Alaska the first angiosperm remains were found in deposits of an alluvial–deltaic origin. During the early–middle Albian these plants probably occupied disturbed near-channel environments. Within the coastal plains and lowlands of the North Pacific Region, repeating transgressions and regressions and lateral river channel migration constantly disturbed environments and provided fresh sedimentary surfaces that were colonised by angiosperms more readily than by other plants. Climatic fluctuations and proximal volcanic eruptions probably contributed to the formation of habitats favourable for early angiosperms. Angiosperm-rich plant communities gradually invaded the Asiatic continental interiors along river valleys and other disturbed habitats and replaced previous fern–conifer-dominated mature climax vegetation. The data presented here do not support the hypothesis of the initial dispersal of early Cretaceous angiosperms along mountain ranges but support the hypothesis of angiosperm dispersal around coastal margins and into continental interiors along disturbed river habitats.

Metallogeny of the junction zone between the Siberian Platform and the Okhotsk-Chukotka volcanogenic belt

Metallogeny of the junction zone between the Siberian Platform and the Okhotsk-Chukotka volcanogenic belt

Petrographic features of conditions of formation of tin-bearing granites of the Okhotsk-Chukotka volcanogenic belt

Petrographic features of conditions of formation of tin-bearing granites of the Okhotsk-Chukotka volcanogenic belt

Magmatic formations in the Okhotsk-Chukotka volcanogenic belt

The relationship between the Okhotsk-Chukotka volcanogenic belt of Northeast USSR and the stage of evolution of magnetism and tectonic development of the region are examined. Recognizing the associations of effusive and intrusive rocks that are typical of the southern part of the volcanogenic belt and that are joined together by some characteristic features, a basic plan is presented for examination of the problem of magnetic formations. On the basis of the distinctive characteristics of epigeosynclinal tectonic development of the territory and the sequence of formation of the magmatic rocks within it, three main groups: volcanic, coleanoplutonic, and plutonic, can be distinguished; and a general scheme of development of these types in space and time within the volcanogenic belt can be developed. According to this scheme, four main stages can be recognized in the Mesozoic and Cenozoic magmatic evolution of the Okhotsk-Chukotka belt. This scheme of classification takes into consideration the factor of the structural development of this tectonomagmatic element.

The volcanogenic-plutonogenic series of gold-ore formations in the Okhotsk-Chukotka volcanogenic belt

The volcanogenic-plutonogenic series of gold-ore formations in the Okhotsk-Chukotka volcanogenic belt