Mineralogical Transformation of Bioweathered Granitic Biotite, Studied by HRTEM: Evidence for a New Pathway in Lichen Activity

Abstract

The question of whether clay minerals can be biogenically transformed as a result of lichen activity at the lichen-rock interface remains unresolved. We applied several microscopical and analytical techniques--scanning electron microscopy-back-scattered electron (SEM-BSE), energy dispersive spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM)--in an attempt to address this issue. Unaffected granitic biotite and bioweathered material from the granitic biotite and Parmelia conspersa lichen thalli interface were examined using HRTEM after ultrathin sectioning. The n-alkylammonium treatment of ultrathin sections was carried out in order to study the biogenous mineralogical transformation of the biotite. Microsamples proceeding from unaffected biotite zones demonstrated homogenous 10-A d(OO1)-value biotite phase. HRTEM images of lattice fringes of samples taken from the lichen-biotite contact zone reveal laorge areas of both unexpanded (10-A) and randomly and R = 3 distributed expanded (from 14-to 30-A) layers of phyllosilicates identified as interstratified biotite-vermiculite. Results of artificial biotite weathering (replacement of K by Ca ion) also revealed the biotitevermiculite phase formation, indicating that K release in biotite is one of the mechanisms responsible for interstratified mineral phase formation. Two parallel processes, physical exfoliation of biotite and interlayer ionic exchange of K and subsequent vermiculite formation, are the mechanisms for biotite bioweathering induced by lichens.

Lichen deterioration of asbestos and asbestiform minerals of serpentinite rocks in Western Alps

“…Pioneer work by Wilson et al (1981) reported the complete Mg depletion of chrysotile colonized by Lecanora atra, yielding amorphous silica as deterioration product. Incongruent ion depletion was also previously reported for other phyllosilicates, as biotite and muscovite, contacted by lichen thalli ( Ascaso and Wierzchos, 1996;Prieto et al, 1997;Wierzchos and Ascaso, 1998).…”

Investigating the role of microbes in mineral weathering: Nanometre-scale characterisation of the cell–mineral interface using FIB and TEM

“…In addition, no chemical alteration of the biotite underneath the cyanobacterial filament was detected via EDX ( Figure 5) or EELS (Figure 6) within the resolution limitations described above. In other studies, weathering of biotite by lichen has been shown to result in a depletion of potassium (Wierzchos and Ascaso, 1998), and the study by Bonneville et al (2009) showed depletion of potassium, iron, aluminium and magnesium. The potential detection of iron depletion in the surface 5 nm of the biotite studied here ( Figure 5) is below the resolution limits measured here (~15 nm for EDX linescan and ~6-7 nm for EF-TEM) and could also, arguably, be described as relatively insignificant in terms of the bioweathering of biotite observed in incubation experiments with other microorganisms (Bonneville et al, 2009 and2011).…”

The effect of air pollution on stone decay: the decay of the Drachenfels trachyte in industrial, urban, and rural environments—a case study of the Cologne, Altenberg and Xanten cathedrals

“…In general, the presence of microorganisms-such as algae, lichen and fungi-indicates higher humidity, which may enhance deterioration processes (Wihr 1986). Biological deterioration of microorganisms can be divided into biophysical and biochemical deterioration processes (Adamo and Violante 2000;Dornieden and Gorbushina 2000;Pinna and Salvadori 2000;Wierzchos and Ascaso 1998). The extent of biological weathering is dependent on qualitative and quantitative distribution of microorganisms and their metabolic products.…”