Sulfur isotopic compositions of the lithospheric mantle sulfides from the Udachnaya pipe (Yakutia)

<p>Sulfide inclusions in Neoproterozoic West African diamonds have revealed mass-independently fractionated sulfur isotopes in them [Smit et.al., 2019]. This feature is a sign of Archean surface changes traced in the mantle. Here we present an S isotope study of the unique fresh mantle deep-seated peridotites, eclogites and pyroxenites with rare or without any secondary alterations from the Udachnaya-East pipe. This research will give better understanding the role of subduction in the formation of the lithospheric mantle under the Siberian craton. Sulfur isotopes (<sup>34</sup>S/<sup>32</sup>S which is denoted as δ<sup>34</sup>S) were measured in the sulfides from eclogites, peridotites and pyroxenites using an Isoprime isotope ratio mass spectrometer (IRMS) with classic configuration with 4 collectors. The sulfides from eclogites are pyrrotite, pentlandites and chalcopyrites. They have δ<sup>34</sup>S values from +0,67 to +3,08 per mil (‰). Sulfides in peridotites are pyrrotite-pentlandite-chalcopyrites assemblages and they have δ<sup>34</sup>S values from +0,22 to +3,55 ‰. These δ<sup>34</sup>S values from eclogites and peridotites are broadly overlap with the field for depleted mantle and chondrites (-1,9 to +0,35‰) [Labidi et.al., 2013; 2014]. Sulfides from pyroxenites are pyrrotite and they have δ<sup>34</sup>S values from -3,62 to +1,49 ‰. These δ<sup>34</sup>S values have a wider range than the estimates for depleted mantle. The δ<sup>34</sup>S values in our samples are close to those in the depleted mantle, but still have deviation from it and do not fractionated. Our data did not detect mass-independently fractionated sulfur isotopes in the mantle samples from the Udachnaya pipe. Thus subduction of the earth’s crust did not play role in the values of sulfur isotopes of the lithospheric mantle sampled by Udachnaya kimberlite pipe. The source of sulfur in these rocks probably was the astenospheric mantle.</p><p>References</p><ol><li>Smit et. al., 2019</li> <li>Labidi et. al., 2013; 2014</li> </ol><p>This study was supported by the Russian Foundation for Basic Research № 18-05-70064</p>