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Acicular and fibrous orthopyroxenes in the volcanics from Santa Maria di Licodia (Sicily, Italy)
No full textThe volcanic dome of Santa Maria di Licodia is located on the SW side of Mt. Etna volcano, close to the Mount Calvario dome (Biancavilla). Some significant differences show the two domes, such as the composition (benmoreite and mugearite, respectively) and the presence of a fibrous orthopyroxene (in the first dome) instead of fibrous fluoro-edenite [1] (in the second one). Fibrous orthopyroxene is rare in nature, and it is prevalently found in metamorphic rocks [2,3] and in ultramafic xenoliths as an autometasomatic product of hydrous magmas [4]. Until today no evidence of volcanic orthopyroxene was highlighted in literature. Preliminary studies [5,6] did not highlight metasomatic processes on both central (massive) and external portion (autobreciated) of the Santa Maria di Licodia dome. Orthopyroxene, associated to alkali-feldspars (Na), augitic clinopyroxene, apatite and Fe-Ti oxides, shows different morphology, such as prismatic, acicular and fibrous. The prismatic morphology occurs in the massive portion, whereas the acicular and fibrous morphology in the brecciated portion. The mineralogical characterization of the orthopyroxene was performed by different analytical techniques (EMPA, SEM-EDS, XRPD). By SEM-EDS investigation a large composition variability within the fibrous orthopyroxene was evidenced. Different morphology correspond to differences in composition, in particular in the iron contents. The prismatic and acicular morphologies show a composition whit high Fe content (up to 18-20 wt% FeO), whereas the fibers present higher Mg content and FeO <11%. Moreover, the highest Fe contents are generally associated to moderate Ca enrichments (about 1-2 wt% CaO). X-ray investigation allowed to identify and define the orthopyroxene as enstatite and ferroan-enstatite, also confirmed by the chemical micro-analyses. The various orthopyroxene morphologies lead to hypothesize different conditions of the dome emplacement (i.e. temperature and cooling rate). However, the fibrous morphology could depend by very fast cooling from high temperatures. Finally, the presence of fibrous orthopyroxene in this locality could represent a potential risk for the human health in comparison to the morphology and composition to the fluoro-edenite fibers occurred in the Biancavilla area and responsible of the pleural mesothelioma in the local inhabitants
Fibrous mineral detection in natural soil and risk mitigation (1(st) paper)
Full text linkThe paper describes a fibrous mineral detection methodology, which is based on the use of alternating rotary motion sieving equipment. The equipment was redesigned to meet additional requirements with respect to initial ones. Under this methodology, the fine fraction passing through the sieves was recovered and analysed to determine the sedimentology, mineralogy and morphology of the potentially particulating fraction. Reliance was made on the following analytical techniques: laser granulometry, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) and polarised and phase contrast light microscopy (PLM, PCLM) for fibrous mineral identification and Walton-Beckett / whole field fibre counting. The samples for the analyses came from known areas with fibrous minerals, e.g. Lauria (Basilicata), and less known areas, e.g. the Natural Reserve of Mt. Rufeno (Latium) and Biancavilla (Sicily). With this methodology, fibres may be directly detected in both farmed and unfarmed soil with fibrous minerals and the process may be repeated in the various stages of farming or during works for creation of fire barriers or lanes, hydrogeological restoration etc. The goal is to identify risks arising from the natural occurrence of asbestos upon atypical activities, such as farming and forestry. With regard to exposure, consideration was given to fibrous minerals not currently classified in the relevant legislation, thus going beyond the search for asbestiform minerals in quarry sites located in ophiolite outcrop areas
FLUOROPHLOGOPITE FROM MT. ETNA VOLCANO: CRYSTAL CHEMISTRY AND IMPLICATIONS FOR THE PHYSICO-CHEMICAL CRYSTALLIZATION CONDITIONS
No full textQuantitative Energy Dispersive X-ray analysis of sub-micrometric particles using a Scanning Electron Microscope (SEM)
No full textThe quantitative scanning electron microscope–energy dispersive X-ray ~SEM-EDX! analysis of a horneblende and two augite prismatic samples reduced to submicrometric particles was performed, and error due to the particle effects ~“absent mass” and the “reduced absorption” effect! was minimized. Correction factors as a function of fragment size were obtained for O, Na, Mg, Si, Ca, and Fe. In addition, the influence of chemical composition of the samples used as standards ~the matrix effect! on correction factors was evaluated. The results indicate that the absent mass effect is dominant for all elements except for the light elements O and Na, for which the reduced absorption effect is dominant. No significant matrix effect has been observed. By using corrected SEM-EDX data, the error on quantification of the element concentration has been estimated to be 3% relative for light elements and below 2% relative for heavy elements ~notably, about 1% relative for Fe!
Arsenic and fluorine in the Etnean volcanics from Biancavilla, Sicily, Italy: environmental implications
No full textMineralogical and geochemical studies were undertaken in the volcanic area of Biancavilla (Catania, Italy) with the aim of explaining the nature of the high As and F contents of the area's rocks. As and F contents in soils and groundwater were also investigated. The metasomatised benmoreite lavas show fluorine and arsenic concentrations up to about 3,000 and 1,000 mg/kg, respectively. Mineralogical analyses show that fluorine occurs mostly in fluoro-edenite and apatite-(CaF) crystals, both abundantly present in the altered rocks, while As is exclusively attributed to the apatite-(CaF) crystals. Specifically, arsenic was observed only at the borders of these apatite crystals. Leaching tests and sequential extraction procedures were carried out to evaluate the potential remobilisation of As and F by the mineral phases and the eventual risks induced by their spreading. The results of the leaching tests suggest that As is almost totally associated with the 'easily reducible' fraction and that it is released by the preferential dissolution of the arsenic enriched rims of apatite-(CaF) crystals. In soils, As concentration is relatively low (about 15 mg/kg, on average), while F ranges from 236 to 683 mg/kg. The underground waters supplying the town of Biancavilla show As and F contents lower than the allowed limits for drinking water, (As:10 mu g/L, F:1-1.5 mg/L). The limited distribution of these rocks and the relatively limited mobilisation by the minerals both contribute to maintain low As and F values, in soils and groundwaters, despite the high values in metasomatised lava samples
In vitro toxicity of new fluoro-edenite amphibolic fibres from Biancavilla (Mt Etna, Sicily, Italy).
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