Piermaria Luigi Rossi

The Strait of Sicily continental rift systems: Physiography and petrochemistry of the submarine volcanic centres

Abstract New morphological, geophysical, mineralogical and petrochemical data on the submarine volcanic centres of the Strait of Sicily continental rift systems lead to the following conclusions: Magma types both in the rift valleys (Pantelleria and Linosa) and plateau areas (Adventure Bank) suggest mantle sources and fractionation processes comparable to those of the Ethiopian Afar section of the East African Rift, despite their different tectonic regimes. However, the volume of the erupted magmas (less than 2000–3000 km 3 ) indicates the similarity with low-volcanicity (dry) rifts. This is probably related to the peculiar tectonic setting of the Pelagian Block (African Foreland) dominated by extensional transcurrent motions connected with a strong Neogene compressive dextral E W megashear along the Sicilian collisional front. In the plateau regions, the most evolved rocks are hawaiites (Graham Bank) which formed by fractionation in the uppermost mantle, probably at the base of the crust. Magma types vary from quartz tholeiites to basanites. In the rift valleys, the range of magma types is more restricted (transitional to alkali basalts) and a considerable volume of highly evolved magmas, particularly in the axial volcanic complex of the Pantelleria Rift, was produced in crustal magma chambers. Isotopic trace-element evidence suggests the involvement of transitional to enriched MORB- and OIB-type mantle sources in the genesis of the quartz tholeiites, alkali basalts and basanites throughout the Strait of Sicily continental rift system, including the Iblean Plateau.

Biomimetic calcium-silicate cements aged in simulated body solutions. Osteoblast response and analyses of apatite coating

PURPOSE Calcium-silicate cements have been recently proposed for application in dentistry as root-end filling and root-perforation repair materials. The aim of this study was to investigate the effect of ageing of experimental calcium-silicate cements on the chemistry, morphology and in vitro bioactivity of the surface, as well as on osteoblast viability and proliferation. METHODS Two experimental cements (wTC-Bi, containing bismuth oxide and wTC), mainly based on dicalcium-silicate and tricalcium-silicate, were prepared and tested for their bioactivity after soaking in Dulbeccos phosphate buffered saline (DPBS), used as simulated body fluid. Human marrow stromal cells (HMSC) were seeded on the cements maintained in DPBS for 5 hr (non-aged group), 14 and 28 days (aged group). Cell viability was assessed by the Alamar blueTM test and morphology by scanning electron microscopy (SEM) at different time endpoints. The surface of the soaked cements was analyzed by environmental scanning electron microscopy or SEM coupled with energy dispersive X-ray microanalysis (ESEM/EDX or SEM/EDX respectively) and the micro-Raman technique. RESULTS The ESEM/EDX results showed a uniform surface composed of CSH hydrogel (mainly derived from the hydration of belite and alite) on both non-aged cements. Micro-Raman spectroscopy revealed the presence of calcium carbonate, anhydrite, ettringite, alite and belite. The SEM/EDX data showed an irregular calcium-phosphate multi-layered biocoating with many sharp and protruding crystals on both the aged cements. Micro-Raman spectroscopy revealed crystalline apatite and calcite. The osteoblast response results showed that both the experimental cements exerted no acute toxicity in the cell assay systems. The non-aged samples promoted greater cell growth. SEM showed cells well spread and adherent to the non-aged materials. A reduced number of attached cells was noticed on the aged cements. Bismuth oxide-containing cement allowed a reduced cell viability suggesting some cytotoxic effects. However, the thick biocoating formed on the 28-day aged samples lowered the deleterious effect of bismuth oxide on cell growth. Actually, micro-Raman spectroscopy revealed progressive bismuth oxide depletion on the wTC-Bi surface, due to the increased thickness of the apatite deposit. CONCLUSIONS The study demonstrated that (1) these materials support osteogenic cells growth and may induce early bone formation, (2) the ageing in DPBS reduced the growth of HMSC, but eliminated the deleterious effect of the bismuth oxide on cell growth. In conclusion, the experimental cements have adequate biological properties to be used as root-end/root repair filling materials or pulp capping materials.

Lateral facies variations in hydromagmatic pyroclastic deposits at Linosa, Italy

Abstract The Linosa volcano, less than a million years old, located in the Sicilian Channel, is formed by a series of coalescing tuff cones, tuff rings, spatter cones, and lava flows among which the Fossa Cappellano produced a succession of surges (the “Fossa Cappellano 2” deposits). Which travelled up to 1225 m. The lapilli and coarse ashes in the deposits are generally mud-coated, accretionary lapilli are common, and the tuffs are frequently vesiculated suggesting that the surges responsible for the deposits were wet. The continuous lateral exposures, from the interior of the Fossa to the extreme edge of the island, show facies evolving in the direction of transport from a massive, in the most proximal section to one dominated by cross-laminated beds in the most distal section, passing by a parallel-laminated (plane bed) facies. In each facies, mean bed thickness, and grain size decrease regularly down current. In the cross-laminated facies, mega-ripple wavelength and amplitude decrease in the direction of transport. In the coarser sizes there is a significant increase in the direction of transport of the lower-density scoriae coupled with a decrease of the non-vesiculated lithics. In the finer sizes, there is a significant increase in relative abundance, of the lower-density feldspar crystals relative to the Fe-Mg crystals. The composition, texture, and primary structure variations of the Fossa deposits are identical to those observed in turbidite sequences, and are similar to the characteristics observed in dry surge deposits recently described from Korea. They are interpreted similarly in terms of decreasing flow power in the direction of transport.

Chapter 7 Volcanism, calderas and magmas of the Alicudi composite volcano (western Aeolian archipelago)

Abstract The Alicudi composite volcano (western Aeolian archipelago) was constructed between c. 106 and 28 ka by lava flows, domes and strombolian scoriae erupted during six Eruptive Epochs, interrupted by periods of dormancy and three caldera-type collapses in the summit area. Marine Isotope Stage (MIS) 5a (81 ka) terrace deposits and widespread Brown Tuffs of external origin are recognized and provide important marker beds for regional stratigraphic correlations. Volcanism was of central type, under control of the summit caldera collapses with negligible influence of regional tectonic trends. Alicudi rocks are basaltic to high-K andesitic and have the most primitive petrological compositions (high MgO, Ni, Cr contents), the lowest Sr–O and the highest Nd–He isotope ratios (87Sr/86Sr=0.70352 to 0.70410; 143Nd/144Nd=0.51289 to 0.51279; δ18O=+5.0 to 5.6; 3He/4He–R/Ra=c. 6.5 to 7.1) over the entire Aeolian archipelago. Their composition and variation through time are the result of polybaric crystal–liquid fractionation of parental calc-alkaline basalts to give basaltic andesitic and andesitic derivative melts. These underwent crustal assimilation during ascent, with basalts being contaminated more strongly than andesitic magmas. Sr–Nd–Pb isotopes suggest source metasomatic modification by fluids from an oceanic-type slab, with a minor role for subducted sediments. DVD: The 10 000 scale geological map of Alicudi is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a geochemical dataset for Alicudi.

Late-Quaternary ancient shorelines at Lipari (Aeolian Islands): stratigraphical constraints to reconstruct geological evolution and vertical movements

Indicators of three fossil shorelines, located at elevations of 43–45 m asl (I order), 23–27 m (II order) and about 12 m (III order), are recognized on the island of Lipari. Detailed evaluation of the stratigraphic relationships to the volcanic substratum allows their correlation with Late-Quaternary eustatic highstands of Tyrrhenian age, corresponding to marine oxygen isotope substages 5e (124 ka), 5c (100 ka) and 5a (81 ka). Marine deposits related to the ancient shorelines represent useful stratigraphic markers, as related unconformities constrain the geological evolution of Lipari. This is interpreted as a result of two main stages of volcanic activity (pre- and post-Tyrrhenian) spaced out by one stage characterized by prevalent marine erosional episodes (Tyrrhenian). Chronological and altimetrical data concerning the ancient shorelines have been used to estimate the vertical mobility of the volcanic edifice of Lipari, which is characterized by a continuous uplift at an average rate of 0.34 mm/a during the last 125 ka: this estimation is fully concordant with the values obtained, during the same time period, from the nearby islands of Filicudi (0.31 mm/a) and Salina (0.36 mm/a), suggesting a similar uplift trend induced by the prevalence of regional tectonic processes.

Chapter 12 Geological history of the Panarea volcanic group (eastern Aeolian archipelago)

Abstract The Panarea volcanic group is made up of dome-fields that are the subaerial culminations of a largely dissected volcanic complex mostly located below sea level. The correlation of marine isotope stage (MIS) 5 marine terrace deposits and numerous tephra layers, combined with the available radiometric ages, shows that the Panarea dome-fields mostly developed between c. 155–149 and 124–118 ka through the emplacement of successive lava domes, lava flows and minor pyroclastic products, interrupted by dormant periods and episodes of faulting in a context of regional uplift, plus volcano-related deformation. Recurrent explosive phases subsequently occurred in the area of minor islets at c. 100 ka (Punta Falcone), 67–56 ka (p1) and 24–8.7 ka (Drauto), together with the emission of the c. 54 ka Basiluzzo dome. The Panarea volcanic group is presently in a quiescent state with fumarolic activity and episodic gas outbursts. Panarea rocks show basaltic andesite and high-K basaltic andesite to high-K dacite and rhyolite compositions, with minor shoshonites. Radiogenic isotope signatures range between those typical of the western Aeolian islands and Stromboli. This reveals a heterogeneous mantle source, which resulted from migration of more primitive asthenospheric mantle from the west during slab rollback, and its admixture with more strongly contaminated Stromboli-type resident mantle. DVD: The 10 000 scale geological map of Panarea is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a full geochemical data set for the Panarea volcanic group.

Evidence of surges overtopping a large topographic barrier: Salina island, Aeolian Archipelago, Italy

Abstract Surge-type deposits mantling a volcanic cone (Fossa Felci) derive from an adjacent eruptive center, not from the volcano itself. Erosional and depositional evidence of the surge mechanism is presented. The topographic obstacle supposed to be overtopped by the surges was over 600 m high.