Smectitization as a trigger of bacterially mediated mn-fe micronodule generation in felsic glass (Livno-Tomislavgrad Paleolake, Bosnia and Herzegovina)

Abstract

Miocene tuffs preserved in argillaceous sediment interbedded with lacustrine successions are commonly encountered throughout the Dinarides Lake System (DLS) in south-eastern Europe. In this contribution the volcanic glass degradation and co-genetic Mn-Fe precipitation were studied in a 14.68 Ma felsic tuff from DLS Livno-Tomislavgrad Basin. Microbial activity has been involved in both reactions thus adding the interest of revealing effects of biotic and abiotic processes taking place during tuff eogenesis. X-ray diffraction and electron microbeam analysis with energy-dispersive X-ray spectroscopy revealed the pitting or granular structures developed at glass rims along with smectite flakes protruding from a degrading glass. Mn-Fe mineralization emerges in the form of Mn-Fe coatings, an initial step to micronodule formation, where traces of biogenetic influence included a high content of phases rich in structural Mn (IV) (i.e., ranciéite and jacobsite) and presence of microbial microfossils. Co-genetic ties between glass degradation and Mn-Fe precipitation were established through the report of dioctahedral smectite formed out of altered glass; which then served as nuclei of the ongoing biotic and abiotic Mn-Fe mineralization. These processes manifest on a continuous involvement of microbial life in the course of eogenesis of pyroclastic material in lacustrine environments.

Description

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. cc-by

Keywords

Biomineralization, Felsic glass alteration, Mn-Fe micronodules, Smectitization

Citation

Badurina, L., Segvic, B., Mandic, O., & Zanoni, G.. 2020. Smectitization as a trigger of bacterially mediated mn-fe micronodule generation in felsic glass (Livno-Tomislavgrad Paleolake, Bosnia and Herzegovina). Minerals, 10(10). https://doi.org/10.3390/min10100899

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