Iowaite from the Udachnaya Kimberlite Pipe, Yakutia: Crystal Chemistry and Postcrystallization Transformations

• Published in: Doklady earth sciences Vol. 517; no. 1; pp. 1190 - 1198
• Main Authors: Zhitova, E. S., Mikhailenko, D. S., Pekov, I. V., Korsakov, A. V., Zolotarev, A. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2024; Springer Nature B.V
• Subjects: Anion exchange; Anion exchanging; Anions; Biotite; Calcium ions; Cations; Crystal structure; Crystals; Divalent cations; Earth and Environmental Science; Earth Sciences; Hydrothermal activity; Interlayers; Ion exchange; Mineral assemblages; Mineralogy; Minerals; Peridotite; Pipes; Single crystals; Zonation; iowaite; crystal structure; hydrotalcite group; layered double hydroxide; Udachnaya kimberlite pipe
• ISSN: 1028-334X; 1531-8354
• DOI: 10.1134/S1028334X24601858

An atypical variety of iowaite with an extremely low content of divalent cations (Mg + Fe 2+ )/Fe 3+ of ~2.75 : 1 is identified in a late hydrothermal mineral assemblage of the Udachnaya kimberlite pipe, Yakutia. Its crystal structure is studied using a single crystal: polytype 3 R , space group , a = 3.1213(3) Å, с = 23.621(4) Å, V = 199.30(5) Å 3 ; R 1 = 0.027. Some crystals are characterized by zonation indicating a natural ion exchange, the leading schemes of which are 2Cl – → SO and 2Cl – → 2SO + Ca 2+ . This is the first reliable case of natural anion exchange in minerals of the hydrotalcite supergroup. The anion exchange reaction occurs with an increase of interlayer distance from 8.0 to 11.2 Å. The composition of the mineral and the character of its zonation bear information on the evolution of late hydrothermal processes.