Abstract - Vol LXXVIII, April 2009 n. 1

- Garnet crystal growth in sheared metapelites (southern Calabria - Italy): relationships between isolated porphyroblasts and coalescing euhedral crystals.

- Three different generations of garnet (Type 1a, Type 1b and Type 2) occur in sheared metapelite of the Cardeto Metamorphic Complex (CMC), cropping out in the southern sector of the Aspromonte Massif (southern Calabria, Italy). Main differences are their size, chemical trends, inclusion trails geometry, and crosscutting relationships with different foliations. All of these aspects were used to discriminate between garnet typologies. The CMC was metamorphosed under greenschist to low-amphibolite facies conditions. The peculiar feature of the whole complex is the presence of a pervasive mylonitic foliation. Alternation of quartz and mica domains, the latter essentially consisting of chlorite, muscovite and subordinately of biotite, gives the main schistosity. Besides these minerals garnet, plagioclase, epidote and amphibole complete the typical rock assemblage. Microstructural evidences associated with mineral-chemical data suggest multistage garnet growth. The first garnet generation (Type 1a) is represented by pre-mylonitic porphyroblasts (up to 8 mm in diameter), usually characterized by plane-parallel inclusion trails. The second generation consists of syn-mylonitic garnets (Type 1b), characterized by spiral-shaped inclusion trails, which give to them the classical snowball appearance. Internal foliations are commonly defined by aligned grains of quartz and ilmenite. A multistage growth was recognized for these garnets by means of both compositional traverses and X-ray maps revealing concentric zonation patterns. The second garnet generation (Type 2) consists of smaller euhedral garnets, usually 100 µm in diameter (occasionally up to 400 µm). They typically occur as several adjacent crystals coalescing around Type 1a and 1b garnets. In samples the outer edge of garnet porphyroblasts (Type 1a and 1b) is the indentation of the adjoining borders of many small idioblastic coalescing grains (Type 2). Layers of small euhedral garnets, concentrically chemically zoned, parallel to the mylonitic foliation were also observed. They could have been developed through different processes: (1) mechanical alignment of already existing Type 2 garnet grains due to the shear deformation or (2) they represent a further stage of crystallization prevalently localized into small domains parallel to the main foliation, favoured by a high mobility elements flux along these surfaces. The process of coalesced euhedral garnets over pre-existing garnet porphyroblasts, here described, could be a widespread crystallization mechanism inside shear zones. The elevated fluid concentration typically present within shear zones could promote the sustenance of chemical elements which support either overgrowth or multistage crystal growth processes.

- Growth of Hydroxyapatite crystals from solutions with pH controlled by novel vapor diffusion techniques. Effects of temperature and of the acidic phosphoprotein osteopontin on crystals growth.

-Crystals of hydroxyapatite were reproducibly grown utilizing 24-wells culture plates from aqueous metastable supersaturated calcium phosphate reacting solutions, under highly controlled conditions of pH and concentration of calcium and phosphate. Two novel growth techniques, based on diffusion of ammonia vapor produced by hydrolysis of ammonium phosphate, useful to buffer pH in the reacting solutions, were developed. Hydroxyapatite was grown from solutions, either at pH 7.4 without any acidic precursor in the temperature range 4 - 38 °C, or by the hydrolysis of brushite at 21, 38, 50 and 70 °C. The latter technique depends on raising the pH from 4.55 to 7.65, which causes the formation of octacalcium phosphate (pH ~ 5.5) as intermediate phase. Subsequently the effects of the acidic phosphoprotein osteopontin on crystals growth were studied carrying out additional sets of experiments, under identical conditions at 21 °C. When initially dispersed into the calcium phosphate mother solutions, osteopontin assumed a pivotal role to control nucleation and growth of brushite, octacalcium phosphate and hydroxyapatite. Moreover osteopontin slowed down kinetics of the phase transformations: brushite —>octacalcium phosphate and octacalcium phosphate —> hydroxyapatite.

- Characterization of metallic artefacts from the Iron Age culture in Campania (Italy): a multi-analytical study.

-Sixteen archaeological findings of Iron age from three sites in the Campania region have been examined for their mineral components, chemical and Pb-isotope composition by a multi-technique approach (XRD, SEM-EDS, ICP-MS, AAS and LIRMS). Mineralogical analyses have emphasized the occurrence of three types of objects, Pb- and Cu-based artefacts and finds made of Fe-bearing phases. Qualitative and quantitative chemical analyses have allowed the characterisation of different elements from the metal and slag objects. Pb-isotope signatures suggest a wide range of possible provenances of the source ores throughout the Mediterranean realm. The results are discussed in relation to mineral characterization, to some aspects of local metallurgical techniques and metal source areas.

- Quantitative chemistry and compositional variability of fluorine fibrous amphiboles from Biancavilla (Sicily, Italy).

- Compositional variability of the new fluorine fibrous amphiboles (fluoro-edenite) from the volcanic area of Biancavilla (Sicily, Italy) is reported here for the first time. Quantitative chemical analysis of a suite of four samples was performed by a standardized SEM-EDS microanalysis method, previously developed and tested on different typologies of fibrous amphiboles. The results highlighted compositional differences, especially concerning Si, Ca, Fe, and Na contents, both within the same and among the different samples. Compared to the previously investigated fluoro-edenite prismatic variety, the fluorine fibrous amphiboles showed average values of Si and Fe contents always higher, whereas Ca was significantly lower, which we consider a distinctive character for the fluorine fibrous variety. The Fe³⁺/Fe_tot ratios, evaluated by Mössbauer spectroscopy, reflected different iron oxidation states: Fe3+ was always more prevalent than Fe²⁺, which was very low for two of the four samples analyzed. Employing the Leake classification, all the analyzed fluorine amphibole fibers showed an edenite-winchite trend, with a non negligible content of tremolite component. Both the fluorine amphibole fibers and the prismatic fluoro-edenite from Biancavilla may be correlated with the same genetic process, but the compositional variability reflect different growth conditions. The large variation observed for Fe³⁺/Fe_tot ratios in the amphibole fibers is probably due to local variations of oxygen fugacity during crystallization. A workable hypothesis is that a hot metasomatizing fluid, enriched in fluorine and other incompatible elements, altered the volcanic rocks and caused the crystallization of either the fibrous fluorine amphiboles, by a very fast cooling, or the prismatic fluoro-edenite, by slow cooling.