Литосфера (Jun 2018)
Geological and isotope-geochemical criteria of evident presence of ancient continental crust in Primorye basement
Abstract
The totality of structural-tectonic, lithologic-mineralogical, isotope-geochemical data on the geology of Primorye and adjacent territories of Northeast China and the Amur Region allows us to justify the criterions for the existence of an ancient sialic crust in its foundation. The main of them are the following. 1. Mesozoic terrigenous rocks of the Sikhote-Alin folded formations are characterized by the Proterozoic model age, with more ancient for arkoses - to 2460 Ma (TNdDM2). They are composed mainly of granite-metamorphic mineral association and have zircons reaching the age of up to 2500 Ma. The terrigenous flysch is arkose-dominant. 2. Тhe territory of South-Western Primorye, is covered by Cenozoic basalts with Proterozoic model ages and anomalously low isotope ratios of lead [Pb206/Pb204], analogous to basalts developed on the ancient AR-PR1 lithospheric blocks. 3. Structural deformation tectonic plan reflects presence of a single ancient rigid foundation of the territory with conformly react to a change of the compression-tension regimes in long time cycles. 4. The abundance of potassium- and barium-rich magmatism with geochemical characteristics of kimberlites-lamproites very spread within Primorye and Amur Region. A similar type of magmatism is not typical for areas with juvenile crust and reflects the presence of the mature continental lithosphere. Since the late Proterozoic, the sialic crust of Primorye has been consistently degraded as a result of delamination and basification processes.
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