1,721,019 research outputs found
Mineral chemistry and Nd isotopic composition of two anorthositic rocks from the Kunene complex (South Western Angola).
No full textCrystal chemistry of clinopyroxenes in spinel-peridotite mantle xenoliths from the Fernando de Noronha oceanic island (NE-Brazil).
No full textCrystal chemistry of a clinopyroxene series in ultrafemic xenoliths from North-Eastern Brazil
No full textA series of clinopyroxenes (Cpx) in peridotitic spinel nodules from Rio Grande do Norte, North-Eastern Brazil, was investigated by X-ray diffraction and electron microprobe analyses and compared with an analogous series from spinel peridotite nodules from Mt. Leura, Victoria, Australia. The examined Cpx series is mainly characterized by increasing Mg/(Mg+Fe2+) ratio (i.e. increase of refractory character of the host nodules), by the substitutions of Alvi vs Mg in the M1 site and Na vs (Ca+Mg) in the M2 site, whereas Aliv in the T site remains substantially constant. The strong Na depletion in the Brazilian Cpx causes a different charge balance from that in the Australian Cpx, in which Na remains quite constant. This feature, associated with the differences in polyhedral and cell volumes which are significantly higher in the Brazilian Cpx than in those of the Australian Cpx, suggests that the Brazilian Cpx crystal chemistry may be related to a lower pressure regime, compared with that of the Australian Cpx series
Differentiation of partial melts in the mantle : evidence from the Balmuccia peridotite, Italy
No full textCrustal fertility and generation of a large silicic magmatic system triggered by underplating in the Ivrea-Verbano case.
No full textPressure gradient and original setting of the southern Ivrea-Verbano Zone, northern Italy.
No full textScambi e strategie di approvvigionamento nel Ljubljansko Barje del IV millennio a.C. dedotti dallo studio archeometrico di manufatti in pietra
No full textWe present results of archaeometrical research of almost 50 stone tools – mostly flat and shaft-hole axes – originating from the bed of the Ljubljanica and several sites of Ljubljansko barje, including Stare gmajne, dating to the second half of the 4th millennium BC. The majority of finds shows exploitation of local raw materials. Tuffs and tuffites, which occur in the area of northern Slovenia and in gravel deposits of the Sava not far from the Barje, can be found among them. The assemblage also includes a group of tools made of imported rocks, such as flat axes made of HP metaophiolites from north-western Italy, shaft-hole axes made of serpentinites and metaultramafites, which respectively are likely to originate from central Austria and from a still unknown area, probably located more to the East. These finds indicate that the Ljubljansko barje played a key role as a mediation place between the Po lowland and the Danubian area and between the Eastern Alps and the Balkans in the 4t
Distinct magma pulses in the Ferrar tholeiites of Thern Promontory (Victoria Land, Antarctica).
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