M. N. Goloburdina, S. A. Grakhanov, А. I. Dak, T. N. Zubova, V. G. Malkovets, V. F. Proskurnin, A. V. Tarasov

New data on the age and preservation of the Archean basement block under the Nakyn kimberlite field, Republic of Sakha (Yakutia)

Abstract. Abstract. The paper establishes the Archean (2643 ± 43 Ma) and Proterozoic (1804 ± 15 Ma) ages of zircon megacrystals from the Nyurba kimberlite pipe, as well as analyzes their typomorphic features. The Archean zircons are characterized by the lacking Late Karelian overgrowth zones, elevated concentrations of yttrium (Y > 100 ppm), rare earth elements (ΣREE > 100 ppm), and heavy rare earth elements (Lu/Gd > 1) compared to the Late Proterozoic zircons (Y < 100 ppm; ΣREE < 50 ppm; Lu/Gd < 1). The obtained data suggest that these zircons originate from metamorphic rock units located in separate blocks or metamorphic zones, which indicates preservation of the Archean formations. The study evidences deformation in zircon crystals, which may serve as key morphological markers of deep-seated melt emplacement. Novel findings confirm preservation of the Archean block of the Tyung terrane basement, which support the Clifford-Janse rule: commercial diamondiferous kimberlite bodies of the Nakyn field are confined within the Archean block. The presence of the Late Karelian overgrowths on the Archean zircons from the xenolith basement of diamondiferous kimberlites in the Central Siberian diamond-bearing province demonstrates a large-scale uneven tectono-thermal transformation of the Tyung terrane for 1.8–2.1 Ga, which should influence the productivity of kimberlite fields or individual deposits.

Keywords: Tyung terrane, East Siberian diamond-bearing province, zircon megacrystals, U-Pb age, SIMS SHRIMP-II, trace elements, diamond potential