CHROMIUM-RICH ILLITE/SMECTITE IN THE BASAL BALINKA CONGLOMERATE OF THE UPPER CARBONIFEROUS-PERMIAN BOSKOVICE BASIN (BOHEMIAN MASSIF)

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Authors	HRŠELOVÁ Pavla HOUZAR Stanislav BURIÁNEK David VŠIANSKÝ Dalibor SZCZERBA Marek CIESIELSKA Zuzanna ŠTELCL Jindřich NEHYBA Slavomír
Year of publication	2023
Type	Article in Periodical
Magazine / Source	Annales Societatis Geologorum Poloniae
MU Faculty or unit	Faculty of Science
Citation
Web	https://doi.org/10.14241/asgp.2023.05
Doi	http://dx.doi.org/10.14241/asgp.2023.05
Keywords	Chromium illite-smectite; Cr-rich spinelides; Balinka Conglomerate; diagenetic alteration; Upper Carboniferous; Boskovice Basin; Bohemian Massif
Description	The Upper Carboniferous polymictic Balinka Conglomerate was deposited along the western margin of the Boskovice Basin (eastern part of the Bohemian Massif). Angular aggregates of deep-green chromium-rich interstratified clay mineral R1-illite(0.8)/smectite (I/S) are present exclusively in the basal part of this unit. The textural position of chromium-bearing I/S (0.77–2.88 wt.% Cr2O3; 0.040–0.153 apfu Cr) in the conglomerate matrix indicates a genetic link with the highly altered chromium spinel, which is preserved in the relics. The source of Cr-rich spinelides was serpentinized peridotites in the adjacent Moldanubicum (Gföhl Unit). The formation of I/S is related to diagenetic processes in the conglomerate matrix. The fluids would have relatively high fugacity of CO2 and activity of K+. K/Ar ages of 284.1 ± 7.7 and 276.3 ± 7.4 Ma (lower Permian – Kungurian/Artinskian age) confirmed the diagenetic origin of this I/S.