Water and moganite participation in agates from Bou Hamza (Morocco).

Autor: Powolny T; Faculty of Natural Sciences - Institute of Earth Sciences, University of Silesia in Katowice, 60 Będzińska St, Sosnowiec, 41-200, Poland. tomasz.powolny@us.edu.pl., Dumańska-Słowik M; Faculty of Geology, Geophysics, and Environmental Protection, AGH University of Krakow, 30 Mickiewicza Ave, Krakow, 30-059, Poland., Szczerbowska-Boruchowska M; Faculty of Physics and Applied Computer Science, AGH University of Krakow, 19 Reymonta St, Krakow, 30-059, Poland., Woszczyna M; Faculty of Geology, Geophysics, and Environmental Protection, AGH University of Krakow, 30 Mickiewicza Ave, Krakow, 30-059, Poland.
Jazyk: angličtina
Zdroj: Scientific reports [Sci Rep] 2024 Sep 28; Vol. 14 (1), pp. 22473. Date of Electronic Publication: 2024 Sep 28.
DOI: 10.1038/s41598-024-73136-x
Abstrakt: Basalt-hosted monocentric agates from Bou Hamza (Morocco) were examined to unravel a discrete relationship between moganite content, water content, and the abundance of various types of chalcedony/quartz microtextures, so that the agate-forming process is refined. Herein, moganite content is noticeably low in length-slow chalcedony (quartzine, up to 18 wt.%), as compared with the co-occurring length-fast (LF) chalcedony (up to 31 wt.%). Such a type of disparity reflects a stabilization of the crystallization front during the formation of chalcedonic bands. Recrystallization-related quartz types (i.e. feathery and mosaic/jigsaw puzzle) show low and high moganite content (0 and up to 34 wt.%, respectively) since they have likely originated from different silica precursors (i.e. opaline and chalcedonic, respectively). Meanwhile, the initial formation of mosaic quartz can be exclusively witnessed in the so-called zebraic variety of length-fast chalcedony (i.e. with twisted fibres) that should be hence regarded as a ,,metastable" variety of silica though. The range of total water content remains quite stable across chalcedonic bands (0.5-0.6 wt%) and reaches the highest values (0.7 wt%) in feathery quartz. However, there is rather a general negative relationship between the content of molecular water and silanol-group water. This can stem from the recycling of water species following the condensation reaction of silanols within the agate geodes. The agates originated from Fe-Ti-bearing solutions that co-precipitated goethite, hematite, and rutile, but also contain minor low-grade carbonaceous material.
(© 2024. The Author(s).)
Databáze: MEDLINE
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