Characterization and possible hazard of an atypical sepiolite associated with aliphatic hydrocarbons from Sassello

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Marco E. Ciriotti
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Characterization and possible hazard of an atypical sepiolite associated with aliphatic hydrocarbons from Sassello

Messaggio da Marco E. Ciriotti » mar 09 ott, 2018 9:51

Prossima pubblicazione.

▪ Giustetto, R., Macaluso, L., Berlier, G., Ganjkhanlou, Y., Barale, L. (2018): Characterization and possible hazard of an atypical asbestiform sepiolite associated with aliphatic hydrocarbons from Sassello (Ligurian Apennines, Italy). Mineralogical Magazine, 82, (in press).

An unusual occurrence of asbestiform sepiolite, filling veins in the antigorite serpentinites of the Voltri Unit exposed in a borrow pit (nowadays reclaimed) in the Deiva forest, near Sassello (NW Italy), was probed 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 SEM-EDS proved that these sepiolite fibres, apparently up to several cm long, are made up of bundles of thinner fibrils (or laths: average length > 100 m; thickness ≈ 80 nm), with a composition consistent to that reported in the literature. The dehydration process was monitored through TGA and FT-IR, performed at increasing T; the latter, in particular, evidenced the presence of moderate amounts of aliphatic hydrocarbons – not yet thoroughly identified – somehow associated to the sample. The crystal structure refinement with the Rietveld method showed no relevant difference from the literature models, although a peculiar distribution of zeolitic H2O 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 breathed; also, its atypical association with hydrocarbons (only reported once previously) might even favour further fragmentation in thinner units.

NdR: Se volete saperne di più, Roberto Giustetto presenterà l'argomento al GMT2018 del 20 ottobre 2018 (Quincinetto): viewtopic.php?f=5&t=14271.

sepiolite group (sepiolite supergroup)

Falcondoite Ni4[Si6O15](OH)2·6H2O
Ferrisepiolite (Fe3+,Fe2+,Mg)4[(Si,Fe3+)6O15](O,OH)2·(4+2)H2O
Loughlinite Na2Mg3[Si6O15]O·8H2O
Sepiolite Mg4[Si6O15](O,OH)2·4H2O
Marco E. Ciriotti

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