1,721,113 research outputs found
Small-scale heterogeneity in calc-alkaline granitoids: an example from leucogranites and granodiorites of the Budduso’ intrusion (NE Sardinia, Italy)
No full textRare earth elements, yttrium, and the isotopic composition of Sr and Nd for assessing the origin of the Quaternary travertines from Acquasanta Terme (Marche, central Italy)
No full textSome constraints to the isochron method by an iterative least-squares approach: application to the Budduso’ leucogranites (NE Sardinia, Italy)
No full textGeochemistry and Sr-Nd isotopic composition of leucogranites and mafic enclaves from the Budduso’ intrusion, northern Sardinia
No full textOrigin of post-Variscan gabbro-derived granulites (Northern Apennines, Italy): crustal contamination processes and implications for mantle sources
No full textAssessing the origin of Sr and Nd isotopes and (REE+Y) in Middle-Upper Pleistocene travertines from the Acquasanta Terme area (Marche, central Italy) and implications for neotectonics
No full textPleistocene (bedded) travertines from Acquasanta Terme display ranges of Sr and (REE + Y) contents (462–1576 mg/kg and 250–13,789 ng/g, respectively), which are consistent with an evaporitic rock source. PAAS-normalized (REE + Y) patterns may support the origin of travertine-bearing fluids from marine rocks. Travertines exhibit a very narrow range of δ87Sr values (from −1.9 to −1.84 or 87Sr/86Sr ratios from 0.70782 ± 6 to 0.70786 ± 6), indicating an unchanged rock source throughout the travertine depositional time (from about >350 to 26 ka), likely represented by Burano evaporites (Upper Triassic), as suggested by previous authors. No Sr contribution from magmatic sources has been detected. Travertines also display a very narrow range of εNd values (from -9.1 to −7.8 or 143Nd/144Nd ratios from 0.51217 to 0.51224), indicating an unchanged source also for (REE + Y) through time, likely the same one providing Sr. Lastly, chemical and isotopic data of Acquasanta travertines have been compared with those of bedded travertines from Semproniano (Tuscany) of similar age. In particular, δ87Sr values clearly distinguish between the two groups, in agreement with their different rock sources. As a whole, these new geochemical and isotopic data on Acquasanta travertines have provided a deeper insight into the origin of their parent hydrothermal fluids, which, upwelling from significant depth, circulated through an area still affected by major seismic activity. In particular, the application of Nd isotopes has resulted useful, as, unlike Sr isotopes of fluid which tend to re-equilibrate rather quickly with rocks along upwelling pathways, Nd isotopes sluggishly do so, thus better reflecting the fluid source
Rare earth element and Sr-Nd isotopic evidence for the origin of fluorite from the Silius vein deposit (southeastern Sardinia, Italy)
No full textRare earth element (REE) and Y contents along with Sr-Nd isotopic ratios have been determined in fluorite and calcite samples from the two main veins of the Silius deposit, hosted in Lower Paleozoic metavolcanic rocks, in southern Sardinia. Fluorite from the late San Giuseppe vein contains higher (107–336 mg/kg) (REE + Y) than fluorite from the early San Giorgio vein (29–94 mg/kg), whereas calcite exhibits a range (175–440 mg/kg) overlapping with that of San Giuseppe fluorite. Irrespective of either vein, the 87Sr/86Sr ratios of fluorite range from 0.71106 to 0.71566, overlapping with those of calcite (0.71257–0.71406), whereas the 143Nd/144Nd ratios are slightly higher for fluorite (0.51221–0.51236) than calcite (0.51211–0.5122). Moreover, the 147Sm/144Nd versus 143Nd/144Nd ratio relationship suggests that San Giuseppe fluorites were deposited by 294 ± 40 Ma, whereas it yields no information for San Giorgio fluorites. Assuming 270 Ma as the most probable age of emplacement, the initial Sr-Nd isotopic ratios and (REE + Y) contents in fluorite indicate the crustal origin of Silius mineralizing fluids, likely from mixing in different proportions of evaporated seawater brines with fluids from the Paleozoic siliciclastic basement and Late Variscan/post-Variscan magmatic rocks. Mineralizing fluids evolved their chemical and isotopic composition through interaction with wallrocks and/or dilution with meteoric waters circulating through the Paleozoic basement. As a whole, the chemical and isotopic composition of fluorite from the Silius deposit resembles that of other fluorite deposits from Variscan Europe
The role of fractional crystallisation, crustal melting and magma mixing in the petrogenesis of rhyolites and mafic inclusion-bearing dacites from the Monte Arci volcanic complex (Sardinia, Italy)
No full textTrace element and isotope geochemistry of gabbro-derived and felsic granulites from the Northern Apennines (Italy): evidence for assimilation/fractional crystallisation in the lower crust
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