1,721,021 research outputs found
CARMIGNANI L., FRANCESCHELLI M., GHEZZO C., MEMMI I., PERTUSATI P.C. RICCI C.A. (1981)- Some PT time path recorded in the Sardinia metamorphic basement. Terra Abstract EUG I, Strasbourg
No full textLa distribuzione del calcio tra granato e plagioclasio nelle metapsammiti della Sardegna nord-orientale
No full textRe-equilibration of detrital muscovite and the formation of interleaved phyllosilicate grains in low temperature metamorphism, northern Apennines, Italy
No full textLi, B-rich Rhaetian metabauxite, Tuscany, Italy: reworking of older bauxites and igneous rocks
No full textCa distribution between garnet and plagioclase in pelitic and psammitic schists from the metamorphic basement of north eastern Sardinia
No full textb0 of muscovite in low and high variance assemblages from low grade Verrucano rocks, northern Apennines, Italy
No full textLi-and B-rich cookeite-bearing metabauxite within late Triassic talus breccia, Alpi Apuane, Italy
No full textApplication of the Rietveld method for the investigation of mortars: a case study on the archaeological site of Thamusida (Morocco)
No full textThis study presents a multi-technique approach to the investigations of mortars, involving the application of the Rietveld method. The quantitative mineralogical analysis of samples was aimed at (1) verifying its significance in relation to results obtained through other techniques and (2) evaluating its potential in mortars characterisation.
Six type of mortars used in the Roman settlement of Thamusida (50 km north of Rabat, Morocco) were investigated through X-ray powder-diffraction and Rietveld refinement, optical microscopy, image analysis, scanning electron microscopy, electron microprobe analysis, X-ray fluorescence (XRF) and combined differential thermal, and thermo-gravimetric analysis (DT-TGA).
All the adopted techniques yielded unique results and complementary data; however, the Rietveld method can actually Substitute thermal analysis accurately. CaO oxide contents obtained by DT/TGA and Rietveld are in good agreement, but both were only partly comparable to XRF results. In our case, XRF and Rietveld results diverge when binders contain more than 67 wt.% CaO. The discrepancies can mainly be ascribed to the presence of amorphous material and to the obtainable accuracy by QPA-Rietveld method; conversely, the nonstoichiometry of phases does not affect our results, because phases with variable compositions are present in small amounts.
Results further showed that the adopted methods were suitable for mortar characterisation. All studied mortars (1) have weak hydraulic properties; (2) employed binders characterised by highly variable CaO contents and by significant amounts of SiO(2); (3) used coarse to fine quartz-carbonate-rich sands as the aggregate; and (4) selectively mixed 2 or 3 parts of aggregate with I part of binder, depending on the destination of the mortar
Shrimp dating of zircons in eclogite from the Hercynian basement from north eastern Sardinia (Italy)
No full textSHRIMP (Sensitive High-Resolution Ion Microprobe) U–Pb ages of zircons from a single sample of mafic eclogite (Punta de li Tulchi, Sardinia, Italy) are reported. The study under cathodoluminescence (CL) reveals two groups of metamorphic zircons and the SHRIMP analyses allow recognition of three stages: 1) 453 +/- 14 Ma; 2) 400 +/- 10 Ma; and 3) 327 +/- 7 Ma. The age of 453 +/- 14 Ma could be that of the magmatic protolith and an age of 327 +/- 7 Ma can reasonably be attributed to the main Variscan collisional event in Sardinia, which produced Barrovian-type metamorphism, and retrogression of eclogite under amphibolite-facies metamorphism. The intermediate age 400 +/- 10 Ma is difficult to interpret and it could represent either the age of the eclogite facies metamorphism or it is a result of Pb-loss during the main Variscan event at 327 +/- 7 Ma
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