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111.
A. Mottana R. Bocchio R. Crespi L. De Capitani G. Liborio G. Della Ventura 《Mineralogy and Petrology》1994,51(1):67-84
Summary Cummingtonite and hornblende occur together in metamorphosed basic rocks interlayered with lower-amphibolite facies sillimanite-muscovite-bearing schists and gneisses in the upper Lake Como region, South-Alpine basement complex of the Alps. Textural, chemical and spectroscopic studies indicate that they do not represent equilibrium pairs, but that hornblende was overgrown by cummingtonite during a late stage of either temperature increase or, more likely, of isothermal pressure release, by a continuous reaction which also produced the reverse zoning of plagioclase.
With 5 Figures 相似文献
Cummingtonit in den Amphiboliten des südalpinen Grundgebirges (oberes Comosee-Gebiet, Italien): seine Beziehungen mit Hornblende
Zusammenfassung Im Gebiet des oberen Como-Sees, im südalpinen Basement-Komplex, kommen Cummingtonit und Hornblende zusammen in metamorphen, basischen Gesteinen mit Zwischenlagen von Sillimanit-Muskovit-führenden Schiefern und Gneisen der unteren Amphibolit-Fazies vor. Untersuchung der Texturen, der chemischen Zusammensetzung und Infrarot-Spektroskopie zeigen, daß diese nicht Gleichgewichts-Paare darstellen, sondern daß Hornblende während eines späten Stadiums, entweder bei zunehmender Temperatur, oder eher während isothermalen Druck-Nachlasses durch eine kontinuierliche Reaktion von Cummingtonit überwachsen wurde, die auch für die reverse Zonierung der Plagioklase verantwortlich ist.
With 5 Figures 相似文献
112.
Dr. F. Princivallel Prof. A. Della Giusta Dr. S. Carbonin 《Mineralogy and Petrology》1989,40(2):117-126
Summary Microprobe analyses and X-ray crystal structure refinement data of Mg-Fe-Al-Cr spinels from different environments are compared. The investigated crystals represent both restitic and recrystallized spinels from an Alpine peridotitic massif, and restitic spinels from four suites of ultramafic xenoliths. Within each suite the crystals represent different steps of an increasing melting process, which causes a strong increase in Cr3+ and a moderate increase in Fe2+, with depletion of Al3+ and Mg2+. Within each suite, in spite of relevant bulk chemistry changes, the ratio of the octahedral to tetrahedral coordination distances, and consequently the oxygen positional parameterx, are kept constant. Conversely,x may differ in suites with similar bulk chemistry, mainly due to different Mg-Al ordering between octahedral and tetrahedral sites. This suggests that thex parameter is strongly affected by physical environment, and that consequently, within the range of the investigated compositions, it could be used as a marker.
With 3 Figures 相似文献
Vergleich der Kristallchemie von Spinellen aus einigen Suiten von ultramafischen Gesteinen
Zusammenfassung EMS-Analyse und röntgenograhsch verfeinerte Kristallstrukturen von Mg-Fe-Al-Cr Spinellen aus verschiedenen petrologischen Situationen wurden verglichen. Unter den untersuchten Kristallen befinden sich sowohl restitische und rekristallisierte Spinelle aus alpinen Peridotiten, als auch restitische Spinelle aus vier Suiten von ultramafischen Xenolithen. Die Kristalle in jeder Suite gehören zu verschiedenen Stufen eines Schmelzprozesses, der ein starkes Anwachsen der Cr3+ - und ein mäßiges Anwachsen der Fe2+- Konzentration bei gleichzeitiger Verminderung des Al3+ - und Mg2+-Gehaltes, verursacht. Jede Suite zeigt, trotz bedeutender chemischer Veränderungen, ein feststehendes Verhältnis von oktaedrischen zu tetraedrischen Polyederdimensionen, weshalb der Sauerstoffparameter x unveränderlich bleibt. Jedoch sehen wir, daß sich diex von den Spinellen zweier verschiedener Suiten mit ähnlichem Chernismus unterscheiden, was auf die unterschiedliche Mg-Al- Anordnung in oktaedrischen und tetraedrischen Positionen zurückzuführen ist. Dies läßt vermuten, daß der Parameterx sehr stark von der petrogenetischen Situation abhängig ist, was bedeutet, daß er als Anhaltspunkt zum Verständnis der physikalischen Entstehungsbedingungen verwendet werden kann.
With 3 Figures 相似文献
113.
Bruno Della Vedova Claudio Vecellio Stefano Bellani Umberta Tinivella 《International Journal of Earth Sciences》2008,97(2):317-332
We present a 3-D thermal model of the Larderello geothermal field (Tuscany) to evaluate (1) the extent and contribution of
the heat transfer mechanisms (conduction vs. convection) at the intermediate-upper crust levels, (2) the variability of the
heat and mass fluxes entering from below and (3) the crucial role of the formation permeability. The model, composed by three
main layers, considers the upper 10 km of the crust to better constrain the simulations with experimental data from borehole,
fluid inclusion studies and hypocentral distributions. Several sets of simulations were carried out with different bottom
boundary temperatures and different formation permeabilities for the two deeper layers. The results indicate that the present
temperature (T) and pressure distributions in the Larderello field require deep reservoir rocks with higher permeability than the overlying
capping units and underlying intermediate crust. Permeability values of 1 mDarcy for the reservoir rocks are enough to allow
fluid convection, if the temperature at 10 km depth is as high as 500 ± 50°C. The presence of localized zones with formation
permeability 50–100 times higher than the surrounding rocks strongly favours the migration of over-pressurized fluids, which
episodically break through the overburden, feeding the presently exploited geothermal fields. 相似文献
114.
D’Aniello Andrea Cozzolino Luca Cimorelli Luigi Della Morte Renata Pianese Domenico 《Natural Hazards》2015,75(2):1403-1433
Natural Hazards - In this paper, it is described the development and the assessment of a 1D numerical procedure for the simulation of debris flow phenomena. The procedure focuses on: (1) the... 相似文献
115.
Vola Gabriele Sarandrea Luca Della Porta Giovanna Cavallo Alessandro Jadoul Flavio Cruciani Giuseppe 《Mineralogy and Petrology》2018,112(4):555-576
Mineralogy and Petrology - This study evaluates the influence of chemical, mineralogical and petrographic features of the Neoarchean limestone from the Ouplaas Mine (Griqualand West, South Africa)... 相似文献
116.
Gregor P. Eberli Daniel Bernoulli Adam Vecsei Rizky Sekti Mark Grasmueck Thomas Lüdmann Flavio S. Anselmetti Maria Mutti Giovanna Della Porta 《Sedimentology》2019,66(4):1266-1301
The Upper Cretaceous (Campanian–Maastrichtian) bioclastic wedge of the Orfento Formation in the Montagna della Maiella, Italy, is compared to newly discovered contourite drifts in the Maldives. Like the drift deposits in the Maldives, the Orfento Formation fills a channel and builds a Miocene delta‐shaped and mounded sedimentary body in the basin that is similar in size to the approximately 350 km2 large coarse‐grained bioclastic Miocene delta drifts in the Maldives. The composition of the bioclastic wedge of the Orfento Formation is also exclusively bioclastic debris sourced from the shallow‐water areas and reworked clasts of the Orfento Formation itself. In the near mud‐free succession, age‐diagnostic fossils are sparse. The depositional textures vary from wackestone to float‐rudstone and breccia/conglomerates, but rocks with grainstone and rudstone textures are the most common facies. In the channel, lensoid convex‐upward breccias, cross‐cutting channelized beds and thick grainstone lobes with abundant scours indicate alternating erosion and deposition from a high‐energy current. In the basin, the mounded sedimentary body contains lobes with a divergent progradational geometry. The lobes are built by decametre thick composite megabeds consisting of sigmoidal clinoforms that typically have a channelized topset, a grainy foreset and a fine‐grained bottomset with abundant irregular angular clasts. Up to 30 m thick channels filled with intraformational breccias and coarse grainstones pinch out downslope between the megabeds. In the distal portion of the wedge, stacked grainstone beds with foresets and reworked intraclasts document continuous sediment reworking and migration. The bioclastic wedge of the Orfento Formation has been variously interpreted as a succession of sea‐level controlled slope deposits, a shoaling shoreface complex, or a carbonate tidal delta. Current‐controlled delta drifts in the Maldives, however, offer a new interpretation because of their similarity in architecture and composition. These similarities include: (i) a feeder channel opening into the basin; (ii) an excavation moat at the exit of the channel; (iii) an overall mounded geometry with an apex that is in shallower water depth than the source channel; (iv) progradation of stacked lobes; (v) channels that pinch out in a basinward direction; and (vi) smaller channelized intervals that are arranged in a radial pattern. As a result, the Upper Cretaceous (Campanian–Maastrichtian) bioclastic wedge of the Orfento Formation in the Montagna della Maiella, Italy, is here interpreted as a carbonate delta drift. 相似文献
117.
Studies on denudation rates can provide insight into the influence of climate change, tectonics, and human activities on landscape evolution. Research performed in Central Italy has shown considerable spatial variability of denudation rates in the major river basins. These studies have focused mainly on the Tyrrhenian side of the Italian peninsula, where Plio-Pleistocene marine deposits filling NW–SE elongated sedimentary basins have been uplifted during the Quaternary up to several hundreds of meters above present sea level. Small sub-catchments developed on clays are affected by sharp- and/or rounded-edged badlands (i.e. calanchi and biancane), representing denudation “hot spots” in the present-day morphoclimatic framework.In this paper, we analyze the relationships between indirectly estimated denudation rates at the catchment scale and field monitoring data at the hillslope scale. We attempt to better understand and quantify all hillslope processes that contribute to seasonal variability of denudation, to help with predicting the net input from “hot spots” to the overall estimated sediment yield at the basin outlets. At the hillslope scale, we discuss, in particular, the variability of denudation rates at calanchi and biancane badlands as a function of their different morphoevolution. 相似文献
118.
Lotfi Mabrouk Taher Guarred Asma Hamza Imed Messaoudi Ahmed Noureddine Hellal 《Marine pollution bulletin》2014
Fluctuating asymmetry, a random deviation of bilateral traits, is assessed on grass goby Zosterisessor ophiocephalus Pallas, 1811 living in one disturbed site and in one unpolluted site Gulf of Gabes (Tunisia). Statistical analysis showed that assessed asymmetries are fluctuating. FA of orbital diameter, sub-orbital distance, pectoral fin and post-orbital length are higher in polluted site compared to control. Chemical pollution seems to be responsible for this high FA. 相似文献
119.
Testing geomorphic signal of active normal faulting: The case of the Cittanova Fault (Calabria,southern Italy)
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Edoardo Peronace Marta Della Seta Francesco Troiani Paolo Galli Biagio Giaccio Paolo Messina Paola Fredi 《地球表面变化过程与地形》2018,43(10):2256-2270
Extracting tectonic signals from the landscape is an important challenge for constraining the style and rate of deformation associated with active faults, especially where their displacement history cannot be independently determined. Based on previous paleoseismological data coupled with new geomorphological field work and 14C dating of geomorphic markers, we analysed the geomorphic signal of the along‐strike differential throw of the Cittanova Fault in southern Calabria (Italy), the recent activity of which is already well documented and constrained. Through DTM‐derived stream power law parameters (SL and χ), we provide evidence of drainage network disequilibrium and reorganization in response to fault growth and deformation style. Furthermore, a methodological test of the reliability of the χ metric as a proxy for the differential throw along the strike of active normal faults provided good preliminary results, consistent with a strong inverse linear correlation with fault throw. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
120.
V. Kuncser U. Russo R. Graziani A. Della Giusta P. Palade M. Bulinski G. Filoti 《Physics and Chemistry of Minerals》1999,27(2):95-102
The local configurations and related hyperfine interactions of the tetrahedrally coordinated Fe2+ in two natural spinels were investigated. A special fitting procedure of the Mössbauer spectra is proposed in order to cover the involved mechanisms over the whole temperature range. The behavior of the quadrupole splitting vs temperature was successfully explained in terms of the split of the electronic 3d ground state doublet under a non-cooperative Jahn-Teller effect also providing estimates of the splitting energy for each configuration. 相似文献