1,721,119 research outputs found
High-resolution analysis of silica and sulphate-rich rock varnishes from northern Victoria Land (Antarctica)
No full textFluid-Mineral equilibrium in antitaxial quartz vein system in manganese-ore from Val Graveglia (Northern Apennines, Italy).
No full textHigh-resolution analysis of silica and sulphate-rich rock varnishes from Victoria Land (Antarctica)
No full textRock varnishes on subaerially exposed surfaces of magmatic rocks in northern Victoria Land (Antarctica) have been analyzed using XRD, SEM-EDS and TEM-AEM techniques. The varnishes are tens of micron in thickness and consist of laminae with different chemical compositions. They always show sharp contacts with the underlying rocks. X-ray microanalysis enables two components to be recognized from their chemical compositions: a component rich in Si with minor Al, Fe, and Mg, and a S and Fe-rich component with minor Al, K, and P. Results of XRD and TEM work reveal that the Si-rich component is made of amorphous material containing few nanometer-thick smectite crystals, most of which have formed in situ. The S-rich component forms subrounded areas and laminae oriented parallel to the outer surface of the rock substrate and may be amorphous or crystalline. The crystals are sulphates of the alunite-jarosite series. The varnish is inferred to have formed by accretion onto the external surface of the rock substrate of airborne dust, followed by remobilization of some constituent and subsequent crystallization of clays and sulphates. The sulphur may have been derived from marine spray and/or fallout of active volcanoes
Tectono-metamorphic evolution of the siliciclastic units in the Middle Tuscan Range (inner Northern Apennines): Mg-carpholite bearing quartz veins related to syn-metamorphic syn-orogenic foliation
No full textIntelligenza fluida e comprensione delle emozioni in soggetti giovani/adulti affetti da ritardo mentale
No full textThe tectono-metamorphic record of the Tuscan Nappe from the Colline Metallifere region (Northern Apennines, Italy)
No full textThis paper deals with a structural and petrographic study carried
out on key outcrops belonging to the Tuscan Nappe exposed in
the Colline Metallifere region (Montieri-Poggio Prugnoli). Here, the
Tuscan Nappe was affected by polyphase deformation characterised
by superposed folding events (F1, F2 and F3) and related tectonic
foliations (S1 and S2) in agreement with the structural setting
described for the Tuscan Nappe exposed both in other places of
southern Tuscany, and in the Alpi Apuane region. The development
of F1 folds was accompanied by metamorphism which produced a
sin-kinematic mineralogical assemblage developed on the S1 tectonic
foliation. This paragenesis, consisting of calcite + quartz ±
muscovite ± Fe- and Ti-oxides, is indicative for a temperature of
about 200-300°C according to the T values estimated for the F1 folding
event documented for the Tuscan Nappe of the Apuan Alps, suggesting
a very low grade metamorphism which affected the Tuscan
Nappe during its stacking in the Northern Apennines collisional bel
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