Compositional heterogeneity of the cratonic lithospheric mantle is known from the Nature’s sampling, such as by kimberlite-type magmatism in Precambrian cratons. Joint analysis of geophysical data demonstrates that magmatism-related thermo-chemical processes contribute to significant lateral and vertical heterogeneity of the cratonic lithospheric mantle worldwide (the North China, East European, Siberian, and Kaapvaal cratons, Greenland and the Canadian Shield), which is reflected in its thermal, density, and seismic velocity structure (Artemieva, 2007, 2009, 2011; Artemieva & Vinnik, 2016ab; Cherepanova & Artemieva, 2015; Artemieva et al., 2019; Shulgin & Artemieva, 2019; Xia et al., 2020). This heterogeneity reflects the extent of lithosphere reworking by regional-scale kimberlite-type magmatism and large-scale tectono-magmatic processes associated with LIPs and subduction systems. The results show a strong correlation between the calculated density of the lithospheric mantle, the crustal structure, the spatial pattern of kimberlites, and their emplacement ages. In all studied cratons, blocks with the lowest values of mantle density (ca. 3.30 g/cm3) are not sampled by kimberlites and may represent the “pristine” Archean mantle. Diamondiferous kimberlites are typical of a low-density cratonic mantle, while non-diamondiferous kimberlites sample mantle with a broad range of density values. Kimberlite magmatism is restricted to anomalous lithosphere, so that the isopycnicity (equal density condition, when compositional anomalies are compensated by temperature anomalies) is satisfied only in kimberlite provinces. An important conclusion is that the Nature’s sampling by kimberlite-hosted xenoliths is biased and therefore is non-representative of pristine cratonic mantle.

Reference(s)

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