Bimodal Volcano-Plutonic Complexes in the Frame of Eastern Member of Mongol-Okhotsk Orogenic Belt, as a Proof of the Time of Final Closure of Mongol-Okhotsk Basin

Abstract

We can ascertain at the example of the modern functioning volcanoes, that their activity accompanies the tectonical rebuilding, that occurred in the Earth’s crust. Material and isotope characteristics of volcanological (volcano-plutonic) formations reflect also the processes that occur at such a depth of Earth, which are not reachable for research for today. The decoding of the interdependence assists to better understanding of the evolution of our planet in different temporal intervals. It also helps to imagine the processes of formation or destruction of the continents. One of them is Euro-Asian continent. It’s name indicates the binominal structure of Europe and Asia. Once two separated continents united in a single whole, forming by that a superstructure – Central Asian folded belt. And the axis of the structure is the Mongol-Okhotsk orogenic belt (Parfenov et al., 1999). During almost all of the Phanerocoic the formation of the belt was accompanied with the formation of a whole series of the volcanic and volcano-plutonic complexes and by the closure of MongolOkhotsk basin. The final stage of the closure of Mongol-Okhotsk basin that occurred at the end of early Cretaceous and was conducted by the formation of the bimodal volcanoplutonic complexes is examined in the article. The bimodal volcano-plutonic complexes of the basalt-trachybasalt – rhyolitic content of the end of the early Cretaceous (119 – 97 Ma) are separated in the Southern and Northern frame of Eastern member of Mongol-Okhotsk orogenik belt. The rocks of the complexes disappear in the Western direction in the region of wedging of the Eastern member of the belt in the same direction. In eastern direction in the South, their development is limited by the structures of Bureya-Jiamusi terrane, and in the North it is limited by Okhotsk-Koriaksky terrane. The features of the geological structure of bimodal complexes are examined in the very article. The results of geochemical, isotope -geochemical and geo-chronological precision research are also shown in the article (by authors and the literature data). A proposal has been made that the rocks of the examined bimodal complexes correlate with some of the Late Mesozoic – Early Cretaceous intra plate bimodal associations of NorthAsian continent by the row of geochemical and isotope geochemical characteristics. And their formation was caused by collision processes that stipulated the closure of the Eastern flank of Mongol-Okhotsk basin by the possible contribution of plume source.