Trace elements and rare earth elements in ground ice in kimberlites and sedimentary rocks of Western Yakutia: Fid-Bau Portal

Trace elements and rare earth elements in ground ice in kimberlites and sedimentary rocks of Western Yakutia

Alexeev, S.V. / Alexeeva, L.P. / Kononov, A.M.

Abstract The paper presents unique results of studying the composition of the ground ice (major components, trace elements, and rare earth elements — REEs) encountered at a depth of 200–250m in sedimentary and magmatic rocks in the Western Yakutia diamond-bearing regions. In addition to those established earlier, three new geochemical types of ground ice have been defined: (i) sulfate-hydrocarbonate, (ii) chloride-hydrocarbonate, and (iii) sulfate-chloride types with mixed cation composition. The ground ice geochemical features are caused by evolutionary processes of interaction in the water–rock system during permafrost formation. The enclosed rocks were the source for the addition of sulfate and chlorine ions, as well as trace elements, to the ground waters of the active water exchange zone that had existed before freezing. The distribution pattern of REEs in ground ice has a special form distinct from that of sedimentary rocks, kimberlites, and ocean waters, but similar to the REE pattern in local river waters. This REE pattern features the positive europium (Eu) anomaly and approximate equality of light and heavy REEs. The obtained results essentially expand the insight into ice-formation processes in sedimentary and magmatic rocks.

Highlights • Cement and intrusive ground ice is best developed in sedimentary and intrusive rocks. • Five geochemical types of texture-forming ground ice are distinguished. • We report unique signatures of ground ice, including trace elements and REEs. • The REE profile for ground ice features a Ʌ-shaped pattern with positive Eu anomaly.