Abstract
The formation of continental crust in the Mongolia-Transbaikalia region is researched to identify the mechanisms of interactions between the crust and the mantle in the development of the Neoarchean, Proterozoic and Paleozoic magmatic and sedimentary complexes in the study area. Using the results of his own studies conducted for many years and other published data on this vast region of Central Asia, the author have analysed compositions, ages and conditions for the formation of Karelian, Baikalian, Caledonian and Hercynian structure-formational complexes in a variety of geodynamic settings. Based on the geostructural, petrological, geochemical, geochronological and Sm-Nd isotope data, he determines the crustal and mantle sources of magmatism, conducts the identification and mapping of isotopic provinces, and reveals the role of island-arc oceanic, accretion-collision and intraplate magmatism in the formation of continental crust. Considering the formation of the bulk continental crust, three main stages are distinguished: (1) Neoarchean and Paleoproterozoic (Karelian) (almost 30% of the crust volume), (2) Meso-Neoproterozoic (Baikalian) (50%), and (3) Paleozoic (Caledonian and Hercynian) (over 20%). This sequence of the evolution stages shows the predominance of the ancient crustal material in igneous rocks sources at the early stage. During the subsequent stages, tectonic structures created earlier were repeatedly reworked, and mixed crustal-mantle and juvenile sources were widely involved in the formation of the bulk continental crust in the study area.
Highlights
The formation of continental crust in the Mongolia-Transbaikalia region is researched to identify the mechanisms of interactions between the crust and the mantle in the development of the Neoarchean, Proterozoic and Paleozoic magmatic and sedimentary complexes in the study area
Using the results of his own studies conducted for many years and other published data on this vast region of Central Asia, the author have analysed compositions, ages and conditions for the formation of Karelian, Baikalian, Caledonian and Hercynian structure-formational complexes in a variety of geodynamic settings
Considering the formation of the bulk continental crust, three main stages are distinguished: (1) Neoarchean and Paleoproterozoic (Karelian), (2) Meso-Neoproterozoic (Baikalian) (50%), and (3) Paleozoic (Caledonian and Hercynian). This sequence of the evolution stages shows the predominance of the ancient crustal material in igneous rocks sources at the early stage
Summary
В этот же период активно проводилось изучение Nd изотопных систем более древних (архей-палеопро терозойских) этапов развития континентальной коры южной части Сибирского кратона в пределах Присаян ского и Прибайкальского выступов, а также Акиткан ского вулканического пояса и Чуйского краевого под нятия. Были опубликованы работы по обобщению ранее выполненных Sm-Nd, в том числе Hf, изотопных исследований по формиро ванию континентальной коры ЦАСП [Condie, Kröner, 2013; Kröner et al, 2014, 2017]. Вместе с тем многие вопросы геодинамического раз вития региона остаются слабоизученными и дискусси онными, особенно при определении роли, объемов и условий образования конкретных океанических, остро водужных, аккреционно-коллизионных и внутриплит ных структурно-формационных комплексов в форми ровании континентальной коры региона, так как они в основном решались без детальной геологической характеристики объектов исследований (фрагментов структур островных дуг и связанных с ними аккреци онных призм, преддуговых и задуговых океанических бассейнов, ареалов коллизионного и плюмового маг матизма). Он образует ядро Дзабханского микроконтинента, пред ставленного архей-палеопротерозойским байдарик ским комплексом ортогнейсов, кристаллических слан цев и амфиболитов с возрастом 2848–2646 млн лет и Nd модельным возрастом протолита TNd(DM)=3.3–2.9 млрд лет [Kozakov et al, 2003, 2014]
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