Gualtieri A. F. The aid of X-Ray powder diffraction to the characterisation and treatment of asbestos containing materials 1-11

ABSTRACT - Fibrous asbestos minerals have been identified as priority substances for risk reduction and pollution prevention. Because of the well known hazardous effects associated with past occupational exposures to asbestos and because of its widespread use in commerce, exposures to asbestos present a general health hazard. Therefore, the identification and quantification of asbestos in bulk materials which are still sited in a number of plants and public buildings is fundamental for a proper plan of social prevention and general intervention. X-ray powder diffraction is considered an effective tool of investigation of bulk materials with high statistical significance. The combined Rietveld-RIR method, has been successfully applied for the quantitative determination in the past of asbestos in bulk materials such as insulating cements, mixed asbestos-slag wools, contaminated soils, and others.
The University of Jussieu in Paris has been partly evacuated because the framework of the building is composed of an asbestos rich material. This paper reports the description of the characterisation of that material and a possible plan of intervention for the treatment of the hazardous material in situ.
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ABSTRACT - Spinel-bearing lherzolite and harzburgite mantle xenoliths from central Sardinia (Italy) contain glassy patches with clinopyroxene and spinel relicts together with euhedral crystallites of olivine, clinopyroxene and spinel. Although texturally uniform, the glass may be chemically distinguished into two groups: the first type with low K₂O (mean 0.07 ± 0.05 wt%) and TiO₂ (mean 0.68 ± 0.12 wt%; LKT-type), and the second type with high K₂O (mean 2.52 ± 0.82 wt%) and TiO₂ (mean 3.14 ± 0.35 wt%; HKT-type). All glass compositions are quartz-normative. Rare phlogopite laths are enclosed in olivine or orthopyroxene crystals. The following mass balance equations have been obtained both for HKT- and LKT-type glasses:

6.9 Cpx₍₁₎ + 0.6Sp₍₁₎ => 3.5Cpx₍₂₎ + 0.6Sp₍₂₎ + 0.1Ol₍₂₎ + 1.0Glass (LKT)
and
7.9 Cpx₍₁₎ + 0.5Sp₍₁₎ + 0.7Phl₍₁₎ => 3.8Cpx₍₂₎ + 0.6Sp₍₂₎ + 0.1Ol₍₂₎ + 1.0Glass (HKT)

where the subscript (1) and (2) represent primary (reactant) and secondary (product) phases, respectively. Clinopyroxene + spinel ± phlogopite are expected to have melted incongruently to yield olivine, clinopyroxene and spinel. This suggests that the glasses are not the product of metasomatic processes, but derive by decompression melting of mantle xenoliths, probably after the incorporation in the host lava. Other evidences of early stages of partial melting come from the relatively abundant spongy-textured clinopyroxene. Recent experimental studies (Raterron et al., 1997) evidence the incongruent partial melting of clinopyroxene at mantle depth several hundreds degrees below its conventional solidus temperature. Metasomatic processes in the Sardinia lithospheric mantle account for the origin of phlogopite in the xenoliths.
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ABSTRACT - The flux growth methods, with Na₂B₄O₇ as flux, was successfully used to produce high-quality single crystals of spinel with compositions corresponding to solid solutions of spinel s.s. (MgAl₂O₄) – magnesioferrite (MgFe³⁺₂O₄) and spinel s.s. – hercynite (Fe²⁺Al₂O₄). Some intermediate terms of spinel s.s. – franklinite (ZnFe³⁺₂O₄) solid solution were also producted. Low cooling rates (1-4°C/h) and linear temperature profiles were applied in the thermal interval 1200-800°C. Thermal runs were performed in air or in an H₂/CO₂ reducing atmosphere. The resulting crystal underwent microchemical, structural and spectroscopic characterisation for later thermodynamic and kinetic studies of spinel order-disorder with temperature. Both the miscibility gap between spinel s.s. and magnesioferrite and the complete solid solution between spinel s.s. and hercyte were experimentally confirmed. The constant presence of minor ferric iron was found in hercyte, in spite of the highly reducing conditions imposed during crystal growth.
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Tommasini S., Polli G. and Ghezzo C. Trace element inferences on the evolution and genesis of the Monte Pulchiana leucogranites, northern Sardinia, Italy 53-67

ABSTRACT - The Monte Pulchiana leucogranites belong to the Sardinia-Corsica batholith and were emplaced during the post-collisional phase of the Hercynian orogeny. They consist of multiple coalescent intrusions cut by numerous aplitic dikes and outcrop along a surface of about 40 Km². At least two different parental magmas have been distinguished on the basis of their geochemical characteristics. The evolution of main group of the Monte <pulchiana leucogranites (MGL) can be accounted for by crystal fractionation process of two extreme mineral assemblages. The discrimination between evolutive and genetic processes allows to set constraints on the geochemistry of the source(s) of the Monte Pulchiana leucogranites. Geochemical andphysical arguments provide evidence for a heterogeneous, andesitic-like composition source for the Monte Pulchiana leucogranites. The origin of this andesitic crust be found in the magmatic activity which took place in the Sardinia and Corsica islands in the Ordovician, prior to the onset of the Hercynian orogeny. The source heterogeities could have developed because of either intrinsic or extrinsic processes. The former concern differentiation of the andesitic magmas, whereas the latter concern the percolation of the huge amount of the late-tectonic monzogranitic melts en route to the sourface, throughout the upper portion of the andesitic crust. This resulted in the formation of a mixed, net-veined crustal source which subsequently experienced a partial melting process during the adiabatic upwelling of the Sardinia-Corsica basement occurred in the post-collisional phase of the Hercynian orogeny.
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ABSTRACT - Melt inclusion analysed were carried out on quaternary rhyolitic rocks from Roccastrada volcano (Tuscany, central Italy). The data confirm the anatectic origin for the magma that gave rise to the Roccastrada volcanism and evidenced no involvement of basic component in the petrogenesis of these melts. Similar compositions of melt inclusions trapped in phenocrysts and of residual glass matrix of Roccastrada rhyolites, suggest that these melts did not undergo to important differentiation processes after their generation. Quartz, sanidine, plagioclase and cordierite crystallized from peralominous melts, at temperatures in the range of 755-820°C, and at pressure of about 150-180 MPa.
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Sucha V., Kraus I., Samajová E. and Puškeloá L. Crystallite size distribution of kaolin minerals 81-92

ABSTRACT - The new BWA (Bertaut-Warren-Averbach) technique for measurement of mean crystallite thickness and thickness distributions of phyllosilicates was applied to a set of kaolin minerals. We analyzed 39 kaolins from the western Carpathians and from other main world deposits, which are of residual, sedimentary, or hydrothermal origin. We show that the BWA technique can be successfully applied to both kaolinites and halloysites. Three different shape types of thickness distribution were found – longnormal, asymptotic and polymodal – among the studies set of samples. Mean thickness data were compared with kaolinite crystallinity indices (Stoch index and Hughes and Brown index) and good correlations were found only for unimodal distributions. These crystallinity indices are not suitable for characterisation of kaolin mixtures.
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