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Characterisation and possible hazard of an atypical asbestiform sepiolite associated with aliphatic hydrocarbons from Sassello, Ligurian Apennines, Italy

Roberto Giustetto, Loredana Macaluso, Gloria Berlier, Yadolah Ganjkhanlou and Luca Barale
Characterisation and possible hazard of an atypical asbestiform sepiolite associated with aliphatic hydrocarbons from Sassello, Ligurian Apennines, Italy
Mineralogical Magazine (April 2019) 83 (2): 209-222

Abstract

An unusual occurrence of asbestiform sepiolite, filling veins in the antigorite serpentinites of the Voltri Unit exposed in a borrow pit (now reclaimed) in the Deiva forest, near Sassello, NW Italy, was investigated with an in-depth analytical approach aimed at studying its crystal-chemistry and structure and evaluating its possible hazards for human health. Optical microscopy and scanning electron microscopy (energy-dispersive spectroscopy mode) proved that these sepiolite fibres, apparently up to several cm long, are made up of bundles of thinner fibrils (or laths: average length > 100 mu m; thickness nearly equal 80 nm), with a composition consistent to that reported in the literature. The dehydration process was monitored through thermo-gravimetric analyses and Fourier-transform infrared spectroscopy, performed at increasing T; the latter, in particular, showed the presence of moderate amounts of aliphatic hydrocarbons - not yet identified thoroughly - associated with the sample. The crystal structure refinement with the Rietveld method showed no relevant difference from the literature models, although a peculiar distribution of zeolitic H (sub 2) O molecules was observed. The geological context suggests that the Sassello sepiolite precipitated from hydrothermal fluids, which were saturated in Mg and silica by the interaction of the host serpentinites. The same setting favoured formation of abiotic hydrocarbons, by means of the Fischer-Tropsch reaction. The extremely long and flexible fibrils (length/width aspect ratio >> 3) of this sepiolite specimen could represent a serious hazard for human health if air dispersed and inhaled; also, its atypical association with hydrocarbons (only reported once previously) might even favour further fragmentation in thinner units.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 83
Serial Issue: 2
Title: Characterisation and possible hazard of an atypical asbestiform sepiolite associated with aliphatic hydrocarbons from Sassello, Ligurian Apennines, Italy
Affiliation: University of Turin, Department of Earth Sciences, Turin, Italy
Pages: 209-222
Published: 201904
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 122
Accession Number: 2019-065533
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, sketch maps
N44°15'00" - N44°45'00", E08°15'00" - E09°00'00"
Secondary Affiliation: Nanostructured Interfaces and Surfaces Center, ITA, ItalyCNR, Istituto di Geoscienze e Georisorse, ITA, Italy
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201934
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