Abstract

The results of U–Th–Pb geochronological (LA-ICP-MS) and Hf isotope (LA-MC-ICP-MS) studies of detrital zircons from sandstones and also the results of Nd isotope studies of whole rocks from the tillite-bearing Maikhan-Uul Formation of the Tsagaan-Olom Group of the shelf cover of the southeastern part of the Dzabkhan terrane of the Central Asian Orogenic Belt are considered. The obtained data made it possible to establish that the sources of sandstones of the Maikhan-Uul Formation of the Tsagaan-Olom Group were rocks of the Neoproterozoic and the Early Precambrian complexes with Archean and Paleoproterozoic Hf and Nd model ages, as well as Neoproterozoic igneous rocks formed from both juvenile and crustal sources. The age of the sandstones of the Maikhan-Uul Formation is in the range of ca. 720–660 Ma. It is shown that a large-scale manifestation of convergence processes with the formation of the juvenile crust and the reworking of the ancient continental crust is established in the structures of the central segment of the Central Asian Orogenic Belt in the Early Neoproterozoic (ca. 960–780 Ma). Most likely, these processes reflect the development of the global subduction system in the paleooceanic region of the Rodinia supercontinent margins.

中文翻译：

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Dzabkhan地层Tsagaan-Olom组基底形成的陆相岩石的年龄和来源：U–Th–Pb年代学，Lu–Hf和Sm–Nd同位素研究的结果

摘要

砂岩碎屑锆石的U–Th–Pb年代学（LA-ICP-MS）和Hf同位素（LA-MC-ICP-MS）研究结果，以及含黑土的全岩石Nd同位素研究结果考虑了中亚造山带Dzabkhan地层东南部陆架的Tsagaan-Olom组的Maikhan-Uul组。所获得的数据可以确定，Tsagaan-Olom群的Maikhan-Uul组的砂岩来源是新元古代和早前寒武纪复合体，它们具有太古宙和古元古代Hf和Nd模型年龄，以及新元古代火成岩由幼年和地壳来源形成的岩石。Maikhan-Uul组的砂岩年龄在约200范围内。720–660马。研究表明，在新元古代早期（大约960年）中亚造山带中段的结构中建立了伴随着幼年壳形成和古代大陆壳重造的辐合过程的大规模体现。 –780 Ma）。这些过程很可能反映了罗迪尼亚超大陆边缘古生代区域全球俯冲系统的发展。