Geochemical Features, Sources, and Geodynamic Settings of Accumulation of the Cambrian Sedimentary Rocks of the Mel’gin Trough (Bureya Continental Massif)

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Abstract—The paper reports first geochemical data on the Cambrian sedimentary rocks of the Mel’gin trough of the Bureya continental massif, as well as geochronological data on detrital zircons from these rocks. It is established, that sandstones of the Chergilen and Allin formations of the Mel’gin trough are dominated by detrital zircons with Late Riphean (peaks on relative probability plots at 0.78, 0.82, 0.94, and 1.04 Ga) and Early Riphean (peaks on relative probability plots at 1.38, 1.45, 1.64 Ga) ages. Single grains have Middle Riphean, Early Proterozoic and Late Archean ages. We can suppose that the sources of Late Riphean detrital zircons in sandstones of the Chergilen and Allin formations are rocks of gabbro‒granitoids (940‒933 Ma) and granite‒leucogranite (804‒789 Ma) associations identified in the Bureya continental massif. It is impossible to determine which rocks were sources for Middle Riphean and older detrital zircons in the Cambrian sedimentary rocks of the Bureya continental massif, because the pre-Late Riphean complexes have not been identified yet in its structure. The most probable geodynamic setting for the accumulation of the Cambrian deposits of the Mel’gin trough is an active continental margin, which is consistent with manifestation of the Early Cambrian granitoids magmatism.