Description: The Cenozoic igneous activity of Sardinia is essentially concentrated in the 38-0.1 Myr time range. On the basis of volcanological, petrographic, mineralogical, geochemical and isotopic considerations, two main rock types can be defined. The first group, here defined SR (Subduction-Related) comprises Late Eocene-Middle Miocene (~ 38-15 Ma) igneous rocks, essentially developed along the Sardinian Trough, a N-S oriented graben developed during the Late Oligocene-Middle Miocene. The climax of magmatism is recorded during the Early Miocene (~ 23-18 Ma) with minor activity before and after this time range. Major and trace element indicators, as well as Sr-Nd-Pb-Hf-Os-O isotope systematic indicate complex petrogenetic processes including subduction-related metasomatism, variable degrees of crustal contamination at shallow depths, fractional crystallization and basic rock partial melting. Hybridization processes between mantle and crustal melts and between pure mantle and crustally contaminated mantle melts increased the isotopic and elemental variability of the composition of the evolved (intermediate to acid) melts. The earliest igneous activity, pre-dating the Early Miocene magmatic climax, is related to the pushing effects exerted by the Alpine Tethys over the Hercynian or older lower crust, rather than to dehydration processes of the oceanic plate itself. The second group comprises volcanic rocks emplaced from ~ 12 to ~ 0.1 Ma. The major and, partially, trace element content of these rocks roughly resemble magmas emplaced in within-plate tectonic settings. From a Sr-Nd-Pb-Hf-Os isotopic point of view, it is possible to subdivide these rocks in two subgroups. The first, defined RPV (Radiogenic Pb Volcanic) group comprises the oldest and very rare products (~ 12-4.4 Ma) occurring only in the southern sectors of Sardinia. The second group, defined UPV (Unradiogenic Pb Volcanic), comprises rocks emplaced in the remaining central and northern sectors during the ~ 4.8-0.1 Ma time range. The origin of the RPV rocks remains quite enigmatic, since they formed just a few Myr after the end of a subduction-related igneous activity but do not show any evidence of slab-derived metasomatic effects. In contrast, the complex origin of the mafic UPV rocks, characterized by low 206Pb/204Pb (17.4-18.1), low 143Nd/144Nd (0.51232-0.51264), low 176Hf/177Hf (0.28258-0.28280), mildly radiogenic 87Sr/86Sr (~ 0.7044) and radiogenic 187Os/188Os ratios (0.125-0.160) can be explained with a mantle source modified after interaction with ancient delaminated lower crustal lithologies. The strong isotopic difference between the RPV and UPV magmas and the absence of lower crustal-related features in the SR and RPV remain aspects to be solved.

Description: In an Original Article by Melluso et al. recently published online (1 November 2011), the mineral named as rosenbuschite should be named låvenite throughout, having the chemical composition broadly corresponding to the chemical formula (Na, Ca)2(Mn, Fe)(Zr, Ti)Si2O7(O, OH, F)2 (see Sørensen, 1997).

Description: A Ba-rich alkali feldspar (hyalophane to almost pure celsian) coexists with melilite in the groundmass of the S. Caterina melafoidite lava, Mt. Vulture, Italy. The accompanying phases are a very Al- and Ti-rich clinopyroxene, magnetite, hauyne-sodalite, Ca-rich nepheline, leucite, apatite-britholite and accessory phases (mainly pyrochlore). This mineral assemblage is considered to be the result of the crystallization of a highly silica-undersaturated, alkali-rich magma, in an environment that stabilized S-Cl-rich minerals and inhibited the crystallization of minerals such as phlogopite, owing to the lack of sufficient amounts of volatile species (F, OH) promoting mica crystallization. As a result, the concentration of Ba in the residual liquids, due to its broadly incompatible behavior with respect to the early-crystallized phases, forced crystallization of an increasingly Ba-rich feldspar, along with melilite and volatile-poor feldspathoids such as nepheline and leucite. This apparently incompatible mineral assemblage may occur where interstitial liquid compositions (and thus the eventual crystallizing feldspar) are very rich in Ba or Sr or both, as noted in other rare occurrences worldwide. The final liquid composition crystallized in an assemblage made up of clinopyroxene + feldspathoids + melilite + hyalophane or celsian; it was thus far more undersaturated in silica than a phonolite.

Description: The lava domes in the northwestern (Cuma), northern (Punta Marmolite) and central (Accademia) parts of the Phlegrean Fields are the subject of this study. The Cuma and Punta Marmolite trachyphonolitic lava domes are among the oldest Phlegrean products cropping out. The Cuma rocks have an agpaitic groundmass, with early alkali feldspar, Fe-rich clinopyroxene, Fe-edenite and sodalite and late rosenbuschite, fluorite, baddeleyite, pyrochlore, britholite, monazite, aegirine (often Zr-rich) and exceptionally Fe–Mn-rich olivine. The bulk-rock compositions at Cuma have some of the highest concentrations of Zn, Mn, Zr, Nb, Th, U and lanthanides among the Phlegrean Fields rocks, and some of the lowest MgO, P2O5, Sr, Eu and Ba. The Punta Marmolite dome is chemically less evolved, and lacks characteristic agpaitic minerals, but features alkali feldspar, sodalite, nepheline and relatively Na-poor, Fe-rich hedenbergite, with rare Ca-rich plagioclase xenocryst cores. The Accademia dome, belonging to the recent activity, is latitic to trachytic in composition, has highly forsteritic olivine (with chromiferous spinel inclusions), calcic plagioclase and Mg-rich diopside (± phlogopite) xenocrysts in an evolved host rock (with phenocrysts and microlites of alkali feldspar, Fe-rich clinopyroxene, Fe-rich amphibole, magnetite, Fe-rich olivine and accessory baddeleyite, zirconolite and fluorite). There is clear evidence of open-system magma crystallization in the form of interaction between a crystallizing, primitive shoshonitic basalt in a reservoir already filled by rather evolved trachytic magma. The magmatic evolution towards the evolved compositions is dominated by crystallization of more and more Na-rich alkali feldspar in a Cl-, F-rich and relatively H2O-poor environment. Input of mafic magma is evident in many trachytic eruptions of the Phlegrean Fields and even in the products of the Campanian Ignimbrite, but eruptions having mineral assemblages rich in xenocryst phases as well as eruptions virtually free of mafic magma input are also frequently observed throughout the history. This suggests a variable pattern of open- and closed-system crystallization, which may or may not be linked to explosive activity, and that can be caused by intermittent supply of basaltic magma from depth.

Description: A Roman luxury villa (1st century BC) was discovered in the town of Positano, in the Sorrento peninsula (Campania region, southern Italy). Despite being more than 20 km away from Vesuvius, the villa was buried under almost overall 20 meters (total thickness) of pyclastic materials of the Plinian eruption of 79 AD, which destroyed Pompeii and Herculaneum towns. The exceptional level of conservation of this residential complex is due to the peculiar burial process, which determined the excellent state of preservation of both the fresco decorations (Fourth Style) and all other artefacts (masonries, plasters, tiles, furnishing remains, wooden elements, kitchenware, glazed oil lamps, bronze vessels and other metallic findings, etc.). This study presents the results of a multi-analytical archaeometric analysis of plasters, fresco pigments and roof tiles, aimed at identifying their mineralogical and petrographic nature and the provenance of raw materials. Constraints to the geoarchaeological landscape of the Positano area are also given. The analyzed plasters are mainly lime-based, usually with the addition of an aggregate. The anchoring layer is made by a volcanic component, characterized by clinopyroxene, alkali feldspar, garnet, amphibole, biotite and leucite crystals, together with a sedimentary component represented by carbonatic fragments, also with traces of microfossils. The features of plasters confirm the high degree of technological standardization of plasters in classical Roman age. Mineral pigments recognized by preliminary XRD are mainly iron-based for the ochers-red-crimson colors and copper-based for green-blues colors. In the roof tiles two kind of tempers are identified. In three samples a volcanic temper was identified, and represented by clinopyroxene, feldspar, garnet and leucite, whereas the temper of a fourth sample contained pumices with minor amounts of alkali feldspar, clinopyroxene and biotite. The raw materials are of local provenance (Somma-Vesuvius, Phlegraean Fields, Apennine limestones), and the microstructure of the materials are comparable with similar artefacts from Pompeii, Herculaneum and other Roman sites in Campania region. On the basis of geoarchaeological investigations, here reported, it is reasonable to think that there are other unearthed archaeological areas in Positano that will require further study to be properly known.

Description: Published

Description: 319-344

Description: 5V. Processi eruttivi e post-eruttivi

Description: JCR Journal

Description: The potentiality of isotope analysis has largely been explored in archaeological sciences to date objects, attribute their provenance and depict ancient human dietary habits. However, the potential of this technique for provenance studies of ancient ceramics has barely been explored, due to the fact that the ceramic process often involves the selection of different raw materials and, consequently, different sources of radiogenic isotopes. In this paper, 87Sr/86Sr and 143Nd/144Nd isotope ratios were measured on raw materials (clays and volcanic temper) that were exploited in antiquity for producing pottery in the Campania region of Italy and, for the first time, on experimental ceramic materials that replicate archaeological pottery. To validate the method, Sr and Nd isotope ratios were also measured on selected archaeological pottery from Cuma. The results of this pioneering approach clearly show that the synthetic mixtures used for the ceramic replicas plot exactly on the theoretical mixing curve between the clay and volcanic temper end-members. On the other hand, technological processes employed during pottery manufacturing such as firing and levigation induce no significant variations in Sr and Nd isotope ratios. Isotope characterisation represents an effective fingerprint of pottery that strictly depends on the geochemical affinity of the raw materials, thus providing a better discrimination among different ceramic productions.

Description: Published

Description: 51-59

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal