Вестник МГТУ, 2021, Т. 24, № 1.

Вестник МГТУ. 2021. Т. 24, № 1. С. 80-87. DOI: https://doi.org/10.21443/1560-9278-2021-24-1-80-87 arsenopyrite, sphalerite and barite. The admixture o f these minerals among the analyzed sulfides contributed to the isotopic contamination of sulfur and changes in 534S. Almost invariably, there is a decrease in 534S between early and later formed sulfides within a given system ( Hutchison et al., 2019). For example, the sulfur isotopic composition (534S) of galena (PbS) from the carbonatites (Khibina, Sallanlatvi, Seblyavr, Vuoriyarvi and Kovdor), as well as from hydrothermal veins of the Khibina massif is significantly lighter than the mantle value of 0 %oVCDT (Bell et al., 2015; Hutchison et al., 2019). Conversely, the nepheline syenites which belong to the early magmatic rocks of Khibina and Lovozero massifs contain sulphides with positive 534S values (Table, Fig. 4). Geochemical sulfur isotope 534S investigations emphasize that parental magmas of the Khibina and Lovozero alkaline massifs were derived from a metasomatized sub-continental lithospheric mantle (Fig. 4). These results correlate with the previous studies, which have shown that the isotopic composition of the carbonatites, alkaline rocks, and rare-metal ores estimated indicates that many of them have mantle sources. It was recently confirmed by the work on the Pb-isotopic composition of the alkaline rocks from the KAP (Kogarko et al., 2019). Earlier, the noble gas isotopic data of carbonatites also confirm that the KAP was likely related to a lower mantle plume ( Tolstikhin et al., 2002; Marty et al., 1998), and radiogenic isotopes also support ancient (potentially Archaean) sources (Bell et al., 2015). The published isotopic data indicate multistage evolution of the Khibina - Lovozero volcanic and plutonic system. First of all, at the premagmatic stage 427±6 Ma ago the plume triggered mantle metasomatism that preceeded the vigorous Paleozoic magmatism (Arzamastsev et al., 2011). The impact of the plume on the upper mantle metasomatically altered under subduction conditions entailed the interaction of the plume and subduction sulfur-enriched component (534S of + 1 to +6 % VCDT) in the magma source. Since subduction exerts an important control on SCLM composition, this would suggest that high-534S Archaean crust were subducted and imprinted a high-534S signature on the SCLM. There is hypothesis argues that a missing Archaean sulphur pool, injected into the mantle at ancient subduction zones and stored in the deep mantle, occasionally recycled back to the near surface in mantle plumes (Farquhar et al., 2016). Thus, our favored hypothesis is that parental magmas of the Khibina and Lovozero alkaline massifs are associated with subcontinental lithospheric mantle that has been metasomatised by fluids and melts derived from previously subducted slabs. Fig. 4. Compilation of stable sulfur isotopes 5 S data for sulfides from the Khibina nepheline syenite (red outlined bars) and Lovozero nepheline syenite (green filled bars) with 534S data for galena (PbS) from the carbonatites (red and blue filled bars) from the Khibina, Sallanlatvi, Seblyavr, Vuoriyarvi, Salmagora, and Kovdor massifs. Normalized histograms show early- (red) and late-stage (blue) 534S for galena from the carbonatites (Bell et al., 2015; Hutchison et al., 2019). The 534S values of potential sulfur sources are shown by the bars at the base of the plot and include marine sulfates (Farquhar et al., 2010); MORB - mid-ocean ridge basalt (Labidi et al., 2012); OIB - ocean island basalt (Labidi et al., 2015; Cabral et al., 2013; Delavault et al., 2016); SCLM - sub-continental lithospheric mantle (Giuliani et al., 2016) Рис. 4. Обобщение данных по стабильным изотопам серы 534S для сульфидов из нефелиновых сиенитов Хибинского (красные, не залитые блоки) и Ловозерского (зеленые блоки) массивов и для галенита (PbS) из карбонатитов (красные и синие блоки) Хибинского, Салланлатви, Себлъявр, Вуориярви, Салмагора и Ковдорского массивов. Нормализованные гистограммы показывают раннюю (красный) и позднюю стадии (синий) 534S для галенита из карбонатитов (Bell et al., 2015; Hutchison et al., 2019). Значения 534S потенциальных источников серы показаны интервалами в основании графика и включают: морские сульфаты (Farquhar et al., 2010); MORB - базальты срединно-океанического хребта (Labidi et al., 2012); OIB - базальты океанических островов (Labidi et al., 2015; Cabral et al., 2013; Delavault et al., 2016); SCLM - субконтинентальная литосферная мантия (Giuliani et al., 2016) 85