86,673 research outputs found
Composition and evolution of fluids during skarn development in the Monte Capanne thermal aureole, Elba Island, central Italy
No full textWe describe the chemistry of the fluids circulating during skarn formation by focusing on fluids trapped in calc-silicate minerals of the inner thermal aureole of the Late Miocene Monte Capanne intrusion of western Elba Island (central Italy). Primary, CH4-dominant C-O-H-S-salt fluid inclusions formed during prograde growth of the main skarn-forming mineral phases: grossular/andradite and vesuvianite. The variable phase ratios attest to heterogeneous entrapment of fluid, with co-entrapment of an immiscible hydrocarbon - brine mixture. Chemical elements driving skarn metasomatism such as Na, K, Ca, S and Cl, Fe and Mn were dominantly partitioned into the circulating fluid phase. The high salinity (apparent salinity between 58 and 70 wt% NaCl eq.) and the C-component of the fluids is interpreted as evidence for a composite origin of the skarn forming fluids that involves fluids derived from the crystallizing intrusion with contributions from metamorphic devolatilisation. Oxidation of a Fe-rich brine in an environment dominated by fluctuation in pressure from lithostatic to hydrostatic conditions (maintained by active crack-sealing) contributed to skarn development. Fluid infiltration conformed to a geothermal gradient of about 100 °C km–1, embracing the transition from high-temperature contact metamorphism and fluid-assisted skarn formation (at around 600 °C and 50-200 MPa) to a barren hydrothermal stage (around 200 °C and 20 MPa)
Evidence for homologous repeating segments within the elementary polypeptide chain of guinea pig thyroglobulin.
No full textIn this paper we report on the peptide maps of the three polypeptides produced by reduction of denatured 19-S thyroglobulin from guinea pig. These maps were obtained by both chemical cleavage (CNBr) and by limited enzymatic proteolysis (Staphylococcus aureus SV 8 protease). Analysis of these peptides showed a strict correspondence among the electrophoretic bands produced by cleavage of the guinea pig thyroglobulin components. These results support the idea that thyroglobulin, even though it has an apparently complex molecular structure, contains polypeptide sequences which are repeated in the elementary chain. Since similar structures should correspond to similar functions, each of these regions may work as a functional domain for the biosynthesis of the thyroid hormones
Re-equilibration textures of fluid inclusions in exhumed high-pressure rocks: the example of the Tuscan Archipelago (Northern Tyrrhenian Sea, Italy)
No full textFluid inclusion study of fluorite from Camissinone deposit, Brembana Valley, Bergamasc Alps
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Fluid inclusion study of fluorite from Camissinone deposit, Brembana Valley, Bergamasc Alps
No full textCassiterite Vein Deposits Related to Late Variscan Ilmenite-series in SW Sardinia (Italy): Insights for a New Tin Province
No full textIn the Arburese region (SW Sardinia, Italy) several vein-type ore deposits, including small Sn minerali-zations, are arranged, with different trends, around two contrasting late-to post-collisional shallow plutons: the Arbus and the Monte Linas plutons, dated at 304 +/- 1Ma, and 289 +/- 1Ma respectively. These intrusions belong to two different ilmenite suites: an earlier high-K rock-series (Arbus Pluton), and a later F-bearing rock-series (Monte Linas Pluton). In the apical portion, close to the host rocks, they suffered greisen type alteration testified by secondary muscovite, B-rich and F-bearing phases. Preliminary fluid inclusion analyses in cassiterite veins, documented polyphase mineralizations and temperature close to 400 degrees C. The petrochemical features and the emplacement history of the Linas pluton meet high favourability for tin accumulation. Despite of their limited extent, the Sn ores of SW Sardinia have a metallogenic relevance as they document a long lasting metallogenic epoch all over the South Variscan Realm
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