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Vedere: http://hdl.handle.net/10077/33612

We analysed the crystallography and the chemistry (major and trace elements) of 16 Cr-diopsides belonging to mantle xenoliths from northern (Waw-En-Namus, Libya; Bou-Ibalrhatene and Tafraoute, Morocco) and central Africa (Nyos and Barombi maars, Cameroon). These mantle xenoliths were extracted from mantle domains underlying a metacraton (Libya), a pericraton (Morocco), and a Pan-African mobile belt (Cameroon). The clinopyroxenes from pericratonic and mobile belt occurrences show similar geochemical features. They usually have high R3+ content and low Ca. When normalized to chondrite abundances, their incompatible trace elements show a wide spectrum of patterns, from slightly depleted to slightly enriched and U-shaped patterns. Such features may indicate interaction with carbonatitic and silicic melts. Their Vcell suggest different equilibrature pressures that are compatible with an ascending diapir and/or entrapment by magmas at different depths within the lithospheric mantle. It is important to stress that variable cell and tetrahedron volumes suggest that Libyan clinopyroxenes formed at variable depths. Those arising from shallower depth are less depleted and may display enriched and U-shaped patterns, while clinopyroxenes deriving from deeper zones display depleted and flat incompatible element patterns, possibly suggesting a melt extraction preceding the delamination of the SCLM.

Le lame d’ascia in pietra levigata provenienti da Palù di Livenza sono state rinvenute sia nel corso di recuperi occasionali sia durante le indagini archeologiche effettuate tra il 1992 e il 1994 nel canale di bonifica. In base alla cronologia di occupazione del sito possono pertanto essere prudentemente attribuite ad un intervallo cronologico piuttosto ampio compreso tra la metà del V e la prima metà del IV millennio a.C., benché i materiali ceramici finora studiati siano in gran parte riferibili a una fase recente e tarda del Neolitico.

Riassunto – La cantina vinicola Skerk si trova a Prepotto di San Pelagio (Carso Triestino) ed è stata scavata entro i litotipi carbonatici del Cretacico superiore. In alcune cavernosità, dovute a carsismo, si trovano delle concrezioni gelatinose, de- nominate mucoliti, formate da un’altissima quantità d’acqua (~ 95 %) e da silice amorfa con subordinati carbonati di calcio amorfi. La deposizione del materiale gelatinoso, con successivo essiccamento, provoca la trasformazione graduale delle sostanze dallo stato amorfo a quello cristallino, però è importante il fattore “tempo”. Sperimentalmente, infatti, si è dimostrato che le prime fasi cristalline compaiono dopo circa quattro mesi dalla deposizione e dopo dieci la trasforma- zione non è ancora completa. In questi casi, la silice amorfa, prima assume le caratteristiche di “opal-C/CT” e poi si trasforma in quarzo. Tra i carbonati, invece, è stata riconosciuta una fase iniziale, il carbonato di calcio amorfo (ACC) e una fase intermedia, la monohydro- calcite - CaCO3*H2O. Entrambi sono precursori della calcite. Il materiale siliceo che costituisce le mucoliti potrebbe derivare, almeno in parte, dall’alterazione di qualche straterello, dallo spessore di pochi centimetri, formato da quarzo criptocristallino e calcite. In considerazione del fatto che questi minerali sono stati trovati entro delle cavernosità della roccia, possono essere con- siderati “minerali di grotta”. Abstract – The winery Skerk is located in Prepotto of St. Pelagius (Triest Karst) and was excavated within the upper Cretaceous carbonate lithotypes. In some hollows, due to karstic phenomena, there are gelatinous speleothems called “mucolites”, formed by a high amount of water (~ 95 %) and by amorphous silica with subordinated amorphous calcium carbonates. The deposition of gelatinous material, with subsequent drying, causes the gradual transformation of the sub- stances from the amorphous to the crystalline state, however the “time” factor is important. Experimentally, in fact, it is shown that the first crystalline phases occur after about four months from the deposition and after ten the processing is not yet complete. In these cases the amorphous silica, first assumes the characteristics of “opal-C/CT” and then turns into quartz. Among the carbonates, however, it has been recognized, as an initial step, the amorphous calcium carbonate (ACC) and an inter- mediate phase, the monohydrocalcite - CaCO3*H2O. Both are precursors of calcite. The siliceous material which constitutes the mucolites could results, al least in part, by the alteration of some little layers, with thickness of few centimetres, formed by cryptocrystalline quartz and calcite. In view of the fact that these minerals where found within the hollowness of the rock, they can be considered “cave mi- nerals”.

Nella grotta “Ma che Liberazione” sono stati raccolti 9 campioni di sedimenti pelitici sciolti. Tramite i “limiti di Atterberg” sono stati classificati come limi argillosi (MH) e argille limose (CL – CH). Le analisi, tramite la diffrattometria a raggi X, hanno permesso di constatare che sono costituiti da abbondanti fillosilicati seguiti da quarzo, scarsi feldspati e quantità variabili di calcite, che può essere anche assente. Tra i fillosilicati, il più abbondante è l’illite, seguita dalla clorite. Scarsa è la caolinite e ancora più scarsa o assente la smectite. Sono stati analizzati anche due campioni di argille e argilliti, che formavano straterelli spessi qualche centimetro entro gli strati calcarei. Si è visto che la loro composizione è diversa dai campioni esaminati precedentemente, infatti il minerale nettamente prevalente è l’illite (> 90%). Seguono scarse quantità di quarzo, feldspati, clorite e calcite. La sua origine, pertanto, è diversa dai campioni precedenti. In the cave “Ma che Liberazione” (“What a Liberation” cave) we collected 9 samples of pelitic loose sediments. Through the “Atterberg Limits” we classified them as clayey silts (MH) and silty clays (CL – CH). The analyzes, by means of the X-ray diffraction, have revealed that they consist of abundant phyllosilicates followed by quartz, scarce feldspar and variable amounts of calcite, which may be also absent. Among the phyllosilicates, illite is the most abundant, followed by chlorite. Kaolinite is scarce and smectite is even more scarce or absent. We, also, have analyzed two samples of clays and shales, which formed little layers of few centimetres thick within the limestone layers. We have seen that their composition is different from the samples previously examined, indeed the clearly prevalent mineral is illite (> 90%). Follow small quantities of quartz, feldspars, chlorite and calcite. Their origin, therefore, is different from the previous samples.

The lithospheric architecture of Africa consists of several Archean cratons and smaller cratonic fragments, stitched together and flanked by younger fold belts. The three larger cratons (West Africa, Congo and Kalahari Cratons) are underlain by Sub Continental Lithospheric Mantle (SCLM) extending to ≥300 km depth and having a prevailing depleted composition. Three series of spinel peridotite xenoliths from Waw-En-Namus (Libya; LB hereafter), Tafraoute and Bou-Ibalrhatene (Morocco; MOR), Barombi Mbo and Lake Nyos (Cameroon; CA) have been investigated to provide a new knowledge of the mantle beneath North-Western Africa continent. In particular MOR and LB should reflect peri- and meta-cratonic conditions, respectively while CA are from the Cameroon volcanic line whose products outcrop within a polycyclic mobile belt. According to their chemistry, the spinels from CAM and MOR xenoliths are magmatic cumulates while LB are representatives of ambient lithospheric peridotites. From a structural point of view, the CAM and MOR spinels are rather similar having comparable cell edges and oxygen positional parameters. The cation distribution allows the determination of an intracrystalline temperature in the range 560-750 °C. Spinels from LB can be divided in two groups with very different oxygen positional parameter and cell edges. The intracrystalline temperature is 680 °C for the second. There is a similarity of Vcell between the CAM, MOR and LBI cpx (< 434 Å3) while those from LBII show Vcell >435 Å3. According to their REE contents, CAM cpx can be divided in 2 groups (depleted and enriched in LREE compared to CPX-DMM), in MOR there are two, both enriched, but with different behavior of the LREE suggesting evolutions starting from a DMM like composition. LB cpx show 4 groups, all of them being more or less depleted. The OH contents are lowest for the LB cpx (100-300 ppm H2O), while the CAM samples are intermediate (200-400 ppm H2O) and the MOR samples show the highest contents (380-610 ppm H2O). Boron is nearly absent apart from two samples (one olivine and one cpx) from CAM. The xenoliths sampled from a probably juvenile lithosphere at the edge of the Cameroon and Morocco lithospheric roots apparently have cumulus-like spinels probably crystallized in situ from percolating melts and thus do not represent a real spinel-peridotites facies; on the contrary peridotite mantle xenoliths from Libya exhibit spinels with features compatible with a slow ascent of a mantle plume. The juvenile behaviors shown by CAM and MOR spinels seem also to be reflected by the cpx-HREE patterns showing typical DMM features. As opposed, for LB ones, where very depleted HREE patterns appear, recent chemical changes seem to have been superimposed to ancient (and/or deeper?) depletion. Funding was provided by the FRA 2013 project of the Trieste University.

Il Museo di Mineralogia e Petrografia del Dipartimento di Matematica e Geoscienze, oltre a costituire un importante strumento di apprendimento per gli studenti universitari dei Corsi di Studio in Scienze Geologiche, Scienze e Tecnologie per l’Ambiente e la Natura e Ingegneria, è un valido supporto per la diffusione della cultura scientifica in ambito delle Scienze della Terra. Per quest’ultima funzione il Museo predispone mostre temporanee e partecipa alle manifestazioni organizzate nel Campus di S. Giovanni in collaborazione con altre realtà museali del Comprensorio. Inoltre, presso il Museo vengono svolte visite guidate per le scolaresche di ogni ordine e grado, in modo da stimolare la curiosità e possibilmente fornire un orientamento per i futuri studi universitari. The Museum of Mineralogy and Petrology of the Department of Mathematics and Geosciences, is not only an important instrument for the students of Geological Sciences, Sciences and Technologies for the Environment and Nature, and Engineering, but also a valid support for the diffusion of scientific knowledge in Earth Sciences. For this purpose, the Museum organizes temporary exhibitions and contributes to the organization of events in the St. Giovanni campus, in collaboration with other museums existing in the same campus. Moreover, the Museum hosts guided visit to scholarships (primary to high school) in order to stimulate their curiosity and interest and possibly to introduce them to Earth Sciences as a future university career.

A layer of coarse cryogenic cave carbonate (CCCcoarse) is documented within a subsurface ice outcrop (in-situ) in a cave of the Julian Alps (southeastern Alps). This original finding, representing the first alpine evidence of in-situ CCCcoarse and the first occurrence from the southern side of the Alps, provides a unique opportunity to betterunderstand the processes associated with the formation of CCCcoarse with respect to the cave ice mass balance. Here, we discuss first considerations on the shape and characteristics of CCCcoarse samples and their potential for palaeoclimate reconstructions in the southern Alps. In the light of accelerated climate change, we emphasize the need for scientific actions to exploit the available physical, chemical, isotopic and biological records from still untapped and fragile cryospheric archives such as ice caves.

Cretaceous to Eocene sandstones from the Southeastern Alps and Outer Dinarides (Italy, Slovenia and Croatia) have been geochemically determined to detect their provenance. The first arenaceous strata of the Julian Basin are strongly chemically influenced by the disgregation of metamorphic and not-metamorphic rock types related to the ancient Vardar sea closure where Island Arc and MORB-like related rock types were generated. At about 56 Ma, one level testifies the strong involvement of continental upper crustal source rocks as a consequence of the rapid arising of the Dinarides. Such contribution is well evidenced also in the Claut basin strata. After this first stage, a new moment of upwelling involved the Julian sediments which contributed, with recycled materials, to the creation of Brkini (and Vipava) basins. Moreover, other protolith rock types, which will represent the main source of the Istrian Basin, begin to be significant

Several samples of Cr-bearing spinel from Indian ophiolites have been studied by X-ray single crystal diffraction and structure refinement, electron probe microanalyses and Mössbauer spectroscopy. Differences between samples coming from massive chromitite bands and those coming from podiform chromitite deposits have been evidenced: the former have (Mg,Fe)-chromite component ≥ 75%, the latter from 69 to 74%. In both cases the complementary components are aluminate (mainly spinel sensu stricto MgAl2O4). As magnesiochromite (MgCr2O4) is always dominant with respect to chromite (FeCr2O4), the studied samples are classified as magnesiochromite. The multi-analytical approach has revealed that some of the studied spinels are non-stoichiometric (due to Fe2+ oxidation and vacancy formation), with those coming from massive chromitite being more oxidised than those from the pods. Comparison between our results and recent literature suggested that spinel oxidation is more common than usually believed: it is not restricted to ophiolites but may occur in different geological settings and may help reconstructing the complex thermo-oxidative history of the host rock. Consequently, the proposed multi-analytical approach is crucial for an accurate crystal chemical characterisation of spinels and other Fe-bearing mineral phases, especially when geothermobarometric calculations have to be performed.

Osteoclasts, as well as preosteoclasts, show different adhesion features in relationship to the substrate on which cells are grown, i.e. the formation of either podosomes belt or sealing zones. Podosomes belt forms on non bone substrates, i.e. when cells interact with glass coverslips or culture plates, whereas sealing zones form when cells grow on bone-like substrates. Podosomes belt corresponds to numerous F-actin columns arranged at the cell periphery, whereas the sealing zone could be defined as a unique large band of actin [1]. In the study of bone resorption mechanisms, the employ of bone slices is not perfectly suitable to investigate actin rearrangement due to cell-extracellular matrix (ECM) interaction, since it doesn’t allow to obtain high quality preparations to be examined both by light and electronmicroscopy (TEM and SEM). In particular, TEM preparation requires demineralization which could influence the chemical properties of either bone slices or bone-like composites. Moreover, the use of bone slices as scaffold, although extensive, doesn’t allow ultrastructural details that are necessary in the study of mineral resorption by monocytes or preosteoclasts [2,3]. The aim of the present study was to set up an experimental model for the study of cell-ECM interaction between either monocytes or early differentiating osteoclasts and a mineralized ECM. RAW 264.7 cells (a monocyte-macrophage cell line that can differentiate in osteoclasts) were cultured on a composite constituted by calcium phosphate and type I collagen to investigate actin polymerization and podosome formation. This bone-like composite doesn’t present the mechanical bone properties, but it is constituted by the main bone components and exhibits the advantage that collagen glues the mineral phase in clusters that can be either added to cell cultures or applied on coverslips, as well as to the culture medium. Light and fluorescence microscopy, as well as TEM and SEM techniques were employed. Results showed that the use of this bone-like composite allowed to obtain useful morphological information about the resorption activity of RAW 264.7 cell line differentiating towards the osteoclastic phenotype., Italian Journal of Anatomy and Embryology, Vol 117, No 2 (Supplement) 2012

Spinels are not only a very important mineral phase present in a great variety of environment from the mantle to the crust but also they are strategic material for the industry. For these reasons their crystal chemistry has been widely studied using both synthetic and natural spinels and different experimental techniques. Due to the composition complexity of natural spinels and in order to better understand the cation distribution between the non-equivalent T and M sites the researchers focused their attention to synthetic binary join. In the past decade several synthetic series have been created by flux-grown technique, among the others MgAl2O4-FeAl2O4, MgAl2O4-MgFe2O4, MgCr2O4-MgFe2O4 and MgCr2O4-FeCr2O4. All these studies demonstrate not only how cell edge, oxygen positional parameter and thermal displacement parameters increase or decrease according to chemistry, but also their relations with the increase of pressure and temperature. These studies are of great relevance to explain the behavior of natural spinels and to better characterize the conditions in which they formed or equilibrated. Among natural spinels, Cr-bearing spinel is one of the most studied. Usually, it formula (Mg, Fe2+)(Cr, Al, Fe3+)2O4. Cr-spinels are ubiquitous accessory phase in ultramafic and mafic intrusive, cumulate and volcanic suites as well as in metamorphic rocks being extremely sensitive to bulk composition, mineralogy and petrogenesis of the host rocks. Spinel main constituents behave very differently during fractional crystallization or partial melting, with Cr and Mg strongly partitioned in the solid and Al in the melt. In addition, partitioning of Mg and Fe2+ between spinel and silicate melts and minerals is strongly temperature dependent and the ratio of Fe2+ and Fe3+ is sensitive to variations in fO2. In this review we discuss a spinel database, comprehending structural parameters and chemistry of all the Cr-bearing spinels studied by means of single crystal X-ray diffraction present in literature as well as other spinels which study is currently in progress. These spinels, coming from different occurrences are discussed in term of MgAl2O4-FeAl2O4-FeCr2O4-MgCr2O4 synthetic end-members considering structural parameters instead of their only chemistry.

The crystal chemistry of three ulvöspinels from the websteritic dykes within the Balmuccia peridotites has been investigated by means of X-ray single crystal diffraction and electron microprobe. They are very similar each other with cell edge about 8.43 Å and oxygen positional parameter between 0.2565 and 0.2570. Ti content is about 0.32 a.p.f.u..As they are embedded in a glass with syenite composition it is supposed they quenched during the rapid cooling of a melt pervading the websteritic dykes. This is the first finding of similar spinels in the studied area.

Processi di biomineralizzazione di alcune Corallinales del Mediterraneo.