S. A. Grakhanov, M. N. Goloburdina, T. N. Zubova, V. F. Proskurnin, A. V. Tarasov

New data on the age of ancient conglomerates in the Ebelyakh, Billyakh, and Mayat River basins and their implications for commercial diamond potential, Republic of Sakha (Yakutia)

Abstract. In the Anabar diamondiferous region, within the unique placer deposits of the Ebelyakh, Billyakh, and Mayat rivers, blocks of conglomerates containing diamonds and high concentrations of kimberlite indicator minerals are widespread in the deluvial sediments. These conglomerates have not been identified in situ. Single fossil findings proposed the Carboniferous age for these formations, which implies the Paleozoic age for the primary source of the Ebelyakh placers. This paradigm encourages exploration for the primary sources of the unique placers but without success. The paper presents U-Pb (SIMS SHRIMP-II) detrital zircon dating data from these conglomerates; they demonstrate a wide age range, with the youngest values corresponding to the Early Cretaceous, which correspond to the timing of erosional-karst depressions developed extensively in the study area. These findings require a substantial revision of strategies for primary diamond deposits exploration in the Anabar region, accounting for the Mesozoic age of the target kimberlites, which could significantly reduce exploration costs.

Keywords: zircon, U-Pb age, SIMS SHRIMP-II, diamond, kimberlite indicator minerals, Cretaceous, North-East Siberian Platform