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101.
Giulio Morteani Giovanni Ruggieri Peter Möller Christine Preinfalk 《Mineralium Deposita》2011,46(2):197-210
The CO2-rich geothermal fluids produced in the Piancastagnaio geothermal field (Mt. Amiata geothermal area, Southern Tuscany, Italy)
show temperatures up to 360°C and pressures of about 200 bar at depths of around 3,500 m (Giolito, Ph.D. thesis, Università
degli Studi di Firenze, Italy, pp 1–147, 2005). CaCO3- and/or SiO2-dominated scales are deposited in the pipes leading to the pressure and atmospheric separators of the geothermal wells. High
content of metastibnite and/or stibnite in both calcite and silica scales and Sb contents of up to 50 mg/L in the fluids indicate
their mineralising potential. The red or black colours of the scales depend on the predominance of red metastibnite or black
stibnite, respectively. In our condensation experiments, as well as during deposition of the scales, metastibnite is the first
Sb2S3 mineral to form. In a second stage, metastibnite is transformed to stibnite. During depressurization the Hg content of geothermal
fluids partitions preferentially into the gas phase, whereas Sb and As remain in the liquid phase. This separation explains
the often observed areal separation of Hg and Sb mineralization. The multistage deposition of Sb in the mining district of
Tuscany is due to a periodic restoration of the permeability of the ore-bearing faults by microseismic events and subsequent
host rock brecciation. The still ongoing microseismic events are induced by the accumulation of high-pressure CO2-rich fluids along faults followed by mechanical failure of the faults. 相似文献
102.
F. Cara G. Di Giulio G. P. Cavinato D. Famiani G. Milana 《Bulletin of Earthquake Engineering》2011,9(6):1961-1985
The Fucino basin (Central Italy) is one of the largest intramountain alluvial plain in the Apennines range. It has a tectonic
origin related to the presence of important systems of faults located in its northern and eastern edges. Some of these faults
are still active and capable of generating strong seismic events. Site effects related to the soft soils filling the basin
can be very important. In this paper we show the preliminary results of a seismic network installed in the Fucino area in
order to collect information about site amplification effects and geometry of the basin. We analyze ambient seismic vibrations
and recordings of about 150 local earthquakes mainly related to the seismic sequence of the April 6th 2009 Mw 6.3 L’Aquila
event. Moreover the strongest events of L’Aquila sequence were analyzed at the three permanent strong-motion stations operating
in the area. Using standard spectral techniques we investigate the variation of resonance frequencies within the basin. The
ground motion recorded in the Fucino plain is mainly characterized by strong energy at low-frequencies (f < 1 Hz) affecting both horizontal and vertical components. This is particularly evident for stations deployed in correspondence
of very thick deposits of sedimentary filling, where a significant increase of ground-motion amplitude and duration is likely
caused by locally generated surface waves. The amplification at low-frequencies (<1 Hz) on the horizontal components can reach
up a factor of 10 in comparison to nearby stiff sites. However, we found evidences of seismic amplification phenomena also
for stiff sites surrounding the basin, including stations of the Italian strong motion network. The independent geological
information and the shallow shear-velocity profiles available for the basin can be combined with resonance frequencies for
deriving representative geological sections to be used as base for future numerical 2D–3D modeling of the basin. 相似文献
103.
Marinella A. LAURENZI Giulio BIGAZZI Maria Laura BALESTRIERI Vladimìr BOUKA 《Meteoritics & planetary science》2003,38(6):887-893
Abstract— A new 40Ar/39Ar data set is presented for tektites from the Central European strewn field (moldavites). This is the only strewn field that is entirely situated in a continental environment and still characterized by scattered ages (14–15.3 Myr). The main objectives of the study were to define more precisely the moldavite formation age and provide a good calibration for a glass standard proposed for fission‐track dating. The laser total fusion ages obtained on chips from 7 individual specimens from the Southern Bohemian and Moravian subfields are restricted to a narrow interval of time, with an average of 14.34 ± 0.08 Myr relative to the 27.95 ± 0.09 Myr of the Fish Canyon Tuff biotite. This result gives a more precise age not only for the tektite field but also for its producing impact. If the genetic link between the moldavites and the Nördlinger Ries impact crater is maintained, then this new age has to be considered a reliable estimate for the Ries crater also. This new value places the formation of Central European tektites within the Lower Serravallian period in the latest geologic timescales. Evidence of their impact products, such as glass spherules or shocked minerals, can, therefore, be sought in sedimentary marine formations in a more precisely defined age interval. 相似文献
104.
Apatite fission-track (AFT) data have been obtained along a traverse across the Marrakech High Atlas to constrain its tectono-thermal evolution. AFT ages vary between 212 ± 15 Ma and 20 ± 4 Ma. An Early Miocene AFT age accompanied by long mean track length from the central part of the chain has been interpreted as the timing of the main inversion of this region with the creation of relief because of the shortening induced by the interplay between the African and Eurasian plates. Thermal modelling of samples collected south of the South Atlas Fault Zone indicates a Middle-Late Miocene or even later cooling that has been attributed to the component of the uplift of the chain related to the thermal anomaly present beneath the Atlas Mountains. 相似文献
105.
K‐Ar ages of authigenic illite from two drill‐core gouge samples of a fault in the Palaeoproterozoic basement of Finland record two distinct faulting events. The older sample yields apparent ages from 1240 ± 26 to 1006 ± 21 Ma for four grain size fractions between 6 and <0.1 μm. The second sample is structurally younger and yields statistically distinct ages ranging from 978 ± 20 to 886 ± 18 Ma. We interpret the ages of the <0.1 m fractions, which are the youngest, as representing the actual time of faulting. XRD analysis and age modelling exclude significant age contamination of the finest dated fractions with inherited host rock components. These results provide therefore an example of meaningful isotopic dating of illite‐type clay material formed during Precambrian faulting, demonstrate and constrain fault reactivation and give evidence for brittle Sveconorwegian Mesoproterozoic shortening and Neoproterozoic extension in Fennoscandia. 相似文献
106.
Giulio Ottonello 《Geochimica et cosmochimica acta》2009,73(21):6447-6654
The hexa-aqua complexes [Fe(H2O)6−m−n(OH)n](2−n)+n = 0 → 3, m = 0 → 6 − n; [Fe(H2O)6−m−n(OH)n](3−n)+n = 0 → 4, m = 0 → 6 − n were investigated by ab-initio methods with the aim of determining their ground-state geometries, total energies and vibrational properties by treating their inner solvation shell as part of their gaseous precursor1 (or “hybrid approach”). After a gas-phase energy optimization within the Density Functional Theory (DFT), the molecules were surrounded by a dielectric representing the Reaction Field through an implicit Polarized Continuum Model (PCM). The exploration of several structural ligand arrangements allowed us to quantify the relative stabilities of the various ionic species and the role of the various forms of energy (solute-solvent electronic interaction, cavitation, dispersion, repulsion, liberation free energy) that contribute to stabilize the aqueous complexes. A comparison with experimental thermochemistries showed that ab-initio gas-phase + solvation energies are quite consistent with experimental evidence and allow the depiction of the most stable form in solution and the eventual configurational disorder of water/hydroxyl species around central cations. A vibrational analysis performed on the 54Fe, 56Fe, 57Fe and 58Fe isotopomers indicated important separative effects systematically affected by the extent of deprotonation. The role of the system’s redox state (fO2) and acidity (pH) on the isotopic imprinting of the aqueous species in solution was investigated by coupling the separative effects with speciation calculations. The observed systematics provided a tool of general utility in the interpretation of the iron isotopic signature of natural waters. Applications to the interpretation of isotopic fractionation in solution dictated by redox equilibria and to the significance of the Fe-isotopic imprinting of Banded Iron Formations are given. 相似文献
107.
Micòl Mastrocicco Giulio Vignoli Nicolò Colombani Nasser Abu Zeid 《Environmental Earth Sciences》2010,61(2):311-322
A portion of an unconfined alluvial aquifer located in the Padana Plain (Italy) was characterized following an integrated
hydro-geophysical approach. Initially an electrical resistivity tomography (ERT) survey was employed to localize the boundaries
of a modest paleo-channel body and to design the installation of a groundwater monitoring network. Multilevel slug-tests were
performed to estimate the aquifer’s saturated hydraulic conductivities. Determined permeability values together with electrical
resistivity data were correlated. The correlation resulted in a site specific bi-logarithmic linear relationship. Based on
this relationship, punctually determined hydraulic conductivities were spatially extended over the studied flow domain. Finally,
continuously measured piezometric heads were used to calibrate a 3D flow model. Sensitivity analysis was performed to confirm
the reliability of the reconstructed permeability field, as well as, to assess the minimum number of direct measurements needed
to safely characterize the selected aquifer portion. The integration of the ERT survey results with the classical hydrogeological
tests can be conveniently applied to constrain the permeability field during flow model calibration. Although the applicability
of the determined relationship is site specific, the followed procedure is useful especially when there is a need to optimize
the available resources and in case of small-scale pilot studies. 相似文献
108.
109.
Giovanni Zanchetta Alessandra Borghini Anthony E. Fallick Francesco P. Bonadonna Gabriello Leone 《Journal of Paleolimnology》2007,38(2):227-239
Ten meters of lacustrine deposits retrieved from Lake Pergusa (Sicily, southern Italy) were investigated through stable isotope
composition (carbon and oxygen) of authigenic carbonate (calcareous muds) and freshwater shells. The core chronology was established
through three AMS dates, and by correlation with a previously dated nearby core. Stable isotope data show that the lake water
evolution was mainly dominated by evaporation. Between ca. 20 and 28 ka the recovered sediments have very high δ18O values, likely corresponding to very dry climatic conditions. The observed rapid oscillations in the δ18O of the recovered sediments during this period also suggest important climatic fluctuations. More humid conditions dominated
during the Holocene period, with the wettest interval occurring between ca. 9000 and 3000 years BP. Late Holocene sediments
represent a substantial return to drier conditions. The available pollen data from a nearby core substantially confirm this
general climatic trend during the Holocene. The positive correlation between δ13C of the calcareous muds and carbonate content suggests that biological activity played a key role in the carbon isotope evolution
of dissolved inorganic carbon. However, a clear climatic signal is not evident from the δ13C record. 相似文献
110.
The cardiac activity of three limpets (Patella rustica, P. caerulea and P. aspera), having a different vertical zonation on the Mediterranean rocky shores, was monitored using a non-invasive technique, during 6 h exposure to copper solutions (0.1 and 0.5 ppm), and after return to copper-free conditions. At 0.1 ppm no significant variation of heart rate was observed in the three species with respect to control conditions, while after 3 h at 0.5 ppm a consistent bradycardia was evident in P. caerulea and P. aspera, but not in P. rustica. After 6 h at 0.5 ppm most of the specimens of the three species were acardic but still reactive to mechanical stimulation. Tests on the resumption of cardiac activity after 6 h exposure to 0.5 ppm showed that even after a prolonged cessation of cardiac activity, limpets quickly resumed heartbeating once returned to clean seawater. However, recovery of heartbeating was faster in the mid- and high-shore species (P. caerulea and P. rustica, respectively) than in the lower-shore P. aspera. Moreover, the cardiac pattern upon recovery was definitely bradycardic in P. aspera, while the other two species showed a significant overshooting in heartbeating rate. Measurement of body burdens of copper showed that P. rustica and P. caerulea were faster in removing the excess of copper than the lower-shore P. aspera. In conclusion, this study showed that taxonomically close and syntopic species having a different zonal distribution exhibit different cardiac responses to waterborne copper and stresses the importance of comparative studies on physiological responses of organisms to metal pollution. 相似文献