This investigation compares weathering crust composition in kimberlite rocks, revealing mineral differences between regions, suggesting new criteria for diamond searches.
A complex investigation of the weathering crust composition of kimberlite rocks has been carried out on the East-European Platform and in Yakutia. Comparison of the results obtained shows that there are some essential differences in the composition of relict minerals. For instance, pyrope and picroilmenite play an insignificant role in kimberlite rocks of the East-European Platform, whereas for the weathering crusts of kimberlite rocks in the majority of the Siberian Platform pipes these minerals are major mineral phases of the heavy fraction. A characteristic typomorphic formation in the weathering crust of the East-European kimberlite rocks is saponite associated with disordered vermiculite-montmorillonite layer-mixed formations which are recommended to be used as additional mineralogical criteria when searching for diamonds. For the Siberian Platform this kind of criteria could involve a complex of secondary and hypergenic kimberlite minerals, including Mg-Fe3+-montmorillonite, trioctahedral Mg-chlorite (with packages σ and (σ1), serpentine (structural types A and B) and phlogopite altered to a different degree and related hydromica 1M.
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N.N. Zinchuk (1992) studied this question.
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