1,721,033 research outputs found
Black gloss pottery: production sites and technology in northern etruria. Part I: provenance studies
No full textThe object of the present study is an assemblage of 149 black gloss pottery samples found in northern Etruria (Tuscany, Italy), at Arezzo, Volterra, Chiusi and Populonia. Complete chemical analyses have been performed for the whole set of samples, whereas mineralogical characterization has been provided for most of the Volterra, Chiusi and Populania samples. The Chiusi-Marcianella production site has been the further object of a detailed study aimed at the creation of a complete reference group. Moreover, several trade routes have been reconstructed, shedding light on the import and export of these ceramics from inland Etruria to the coast and vice versa
Short-range mobilization of elements during thermal metamorphism of the Kharlovo gabbro aureole
No full textMass balance and compositional variation in the outer part of the contact aureole shows that mass transfer of the main petrogenetic components was confined to small domains of a few hundredths of mm3 in chlorite-biotite-mica and epidote-plagioclase-titanomagnetite aggregates. The chemical homogeneity of the environment was practically unaffected by the thermal metamorphism. -Author
Zoning of chloritoid from kyanite facies rocks, Alpi Apuane, Italy
No full textChloritoid with significant Mg-Fe zoning occurs as lath-shaped porphyroblasts and as clusters of subradiating crystals in the Triassic Verrucano metapsammite (quartz + muscovite + chlorite + chloritoid ± kyanite) of the Massa Unit, Alpi Apuane. Two main types of chloritoid zoning profiles were found. The first type is characterised by gradual increase in Mg from core to rim of the porphyroblasts. In the second type the Mg content is constant from the core to the inner rim, but sharply decreases in the outer rim. Both types of zoning have been interpreted as the result of prograde growth during the Alpine metamorphism. The temperature, estimated using the chlorite-chloritoid thermometer, ranges from 467 to 560°C
La spettroscopia Raman nella diagnostica dei Beni Culturali: esempio di applicazione alla caratterizzazione degli affreschi conservati nella Chiesa di Sant’Agostino a Siena
No full textClay mineral fluctuations and surface textural analysis of quartz grains in Pliocene-Quaternary marine sediments from Wilkes Land continental rise (East-Antarctica): Palaeoenvironmental significance
No full textPliocene-Quaternary marine sediments from Wilkes Land continental rise were investigated using clay mineral analysis and quartz grain surface texture observations. The studied piston cores were collected during a geophysical and geological survey in the framework of the Italian and Australian WEGA Project. The cores were collected along two transects crossing the channel-mound system that characterizes the Wilkes Land continental rise. Massive and laminated facies were recognized in these sedimentary sequences. The clay mineral assemblages are dominated by illite. Smectite and chlorite occur in intermediate amounts, whereas kaolinite is scarce. Illite derives from the hinterland of the Mertz and Ninnis glaciers. Smectite and kaolinite derive from the Ross Sea area and they are transported by westward marine bottom currents. Chlorite is derived both from the adjacent continent and from the Victoria Land. Different concentrations of individual clay minerals in the massive and laminated facies are controlled by the interplay between different source areas and the main sedimentary processes. Glacial and eolian quartz grains prevail in the massive units indicating short transportation and rapid deposition from melting ices, with no further significant transport action by marine currents. In the laminated facies the high amount of quartz grains affected by high-energy subaqueous transport features are related both to turbiditic processes and to bottom current transport. © 2005 Elsevier B.V. All rights reserved
b0 of muscovite in low and high variance assemblages from low grade Verrucano rocks, Northern Apennines, Italy
No full textThe origin of arfvedsonite in metabasites from contact aureole of the Kharlovo gabbro intrusion
No full textHornblende and arfvedsonite were formed at T = 525-550 degrees C and P = 1-1.5 kbar in the middle part of the contact aureole of the Kharlovo gabbro massif according to the following reactions:
(1) 0.8 Chl + 0.27 Bt + 0.83 Cal + 1.38 Mag + 1.68 Spn + 1.4 Ab = 1.5 Hbl + 1.58 Ilm + 4.65 H2O + 0.83 CO2
(2) 0.02 Chl + 1.18 Ab + 0.21 Cal + 0.14 Mag = 0.1 Arf + 1.0 Olg + 0.02 H2O + 0.21 CO2
A rare combination of heterogeneous rock composition, PT-parameters and thermal metamorphism of short duration led to the formation of arfvedsonite in metabasites. Arfvedsonite formed under local saturation of pore solution by Si, Na and Fe in a very small volume as a result of a local metasomatic reaction. These reactions were controlled mainly by sodium and silicon leaching during incongruent dissolution of acid plagioclase. Mass balance analysis and the variation of composition and amount of coexisting mineral show that the transfer of the main petrogenetic components was limited to volumes as small as 0.06-0.1 mm(3)
Glazed ceramic manufacturing in southern Tuscany (Italy): evidence of technological continuity throughout the medieval period (10th-14th century)
No full textArchaeometric investigation allowed the characterization of two important classes of ceramics: 'vetrina sparsa' and 'invetriata grezza'. Their archaeological peculiarity makes them particularly suited for tracing the evolution of glaze manufacturing in southern Tuscany throughout the medieval period (10th-14th centuries). These ceramics were found in different sites of historical importance, and also from a mining perspective. Local copper, lead, zinc and iron mineralizations supported the growth of several settlements in the vicinity of the mines. The many castles and different archaeological finds (ceramics, glazed ceramic, slag etc.) attest to the intense mineral exploitation of the area from at least the first millennium BC up to the modern period. In light of these geological and archaeological characteristics, archaeometric investigation was intended to provide insight into ancient technical knowledge of ceramic glazing and to determine the source area for raw materials in the medieval period (10th-14th centuries). Ceramic bodies were analysed through OM, XRDp, SEM-EDS and XRF, while coatings were investigated through SEM-EDS. Mineralogical, petrographic and chemical analyses revealed slightly different preparation and firing processes for the two classes of ceramics. These data suggest the continuity through the centuries of the 'vetrina sparsa' and 'invetriata grezza' production technology. The mineralogical phases, such as monazite, xenotime, zircon, barite, Ti oxide, ilmenite, titanite, tourmaline and ilvaite, and the lithic (intrusive and volcanic) fragments detected within the ceramic bodies suggest a source area in the vicinity of the Campiglia mining district. Lastly, the presence of Cu-Zn-Pb (Ag) and Fe sulphide mineralizations (materials used to produce glaze) in the area supports the hypothesis of local manufacture. © University of Oxford, 2007
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