Phosphate defects and apatite inclusions in coral skeletal aragonite revealed by solid-state NMR spectroscopy     

Harris E. Mason  Paolo Montagna  Laura Kubista  Malcolm McCulloch 《Geochimica et cosmochimica acta》2011,75(23):7446-7457

Recent development of paleo-nutrient proxies based on the phosphorus/calcium (P/Ca) ratio in tropical- and deep-water corals (also known as cold-water corals) require an understanding of the processes by which P is incorporated into the coral skeletal aragonite. Here, we apply single- and double-resonance solid-state nuclear magnetic resonance (NMR) spectroscopy to determine the speciation of P in coral aragonite. The results show that the majority of P occurs as phosphate defects in the aragonite structure, but in many samples a significant fraction of the P occurs also in crystalline hydroxylapatite inclusions. Quantification of the amount of hydroxylapatite indicates that its presence is not related simply to external environmental factors and that it can occur at varying abundances in different parts of the same corallite. Since there is currently no model available to describe the relationship between dissolved inorganic phosphate and its incorporation as apatite inclusions into carbonates, careful screening of samples which contain only phosphate in the aragonite structure or selective microsampling could improve proxy development.  相似文献   

Polyphase thrusting and dyke emplacement in the central Southern Alps (Northern Italy)     

Paolo D’Adda  Andrea Zanchi  Maria Bergomi  Fabrizio Berra  Marco G. Malusà  Annalisa Tunesi  Stefano Zanchetta 《International Journal of Earth Sciences》2011,100(5):1095-1113

The Triassic succession of the central Southern Alps (Italy) is stacked into several units bounded by south-verging low-angle thrust faults, which are related to two successive steps of crustal shortening. The thrust surfaces are cut by high-angle extensional and strike-slip faults, which controlled the emplacement of hypabissal magmatic intrusions that post-date thrusts motions. Intrusion ages based on SHRIMP U–Pb zircon dating span between 42 ± 1 and 39 ± 1 Ma, suggesting close time relationships with the earliest Adamello intrusion stages and, more in general, with the widespread calc-alkaline magmatism described in the Southern Alps. Fission-track ages of magmatic apatites are indistinguishable from U–Pb crystallization ages of zircons, suggesting that the intrusion occurred in country rocks already exhumed above the partial annealing zone of apatite (depth < 2–4 km). These data indicate that the central Southern Alps were already structured and largely exhumed in the Middle Eocene. Although we describe minor faults affecting magmatic bodies and local reactivations of older structures, no major internal deformations have occurred in the area after the Bartonian. Neogene deformations were instead concentrated farther south, along the frontal part of the belt.  相似文献   

The Second World Landslide Forum     

Claudio Margottini  Paolo Canuti  Kyoji Sassa 《Landslides》2011,8(1):133-138

ICL\IPL Activities

The Second World Landslide Forum  相似文献   

New model to determine forces at on-bottom slender pipelines     

Francesco Aristodemo  Giuseppe Roberto Tomasicchio  Paolo Veltri 《Coastal Engineering》2011

The present paper proposes a numerical model to determine horizontal and vertical components of the hydrodynamic forces on a slender submarine pipeline lying at the sea bed and exposed to non-linear waves plus a current. The new model is an extension of the Wake II type model, originally proposed for sinusoidal waves (Soedigdo et al., 1999) and for combined sinusoidal waves and currents (Sabag et al., 2000), to the case of periodic or random waves, even with a superimposed current. The Wake II type model takes into account the wake effects on the kinematic field and the time variation of drag and lift hydrodynamic coefficients. The proposed extension is based on an evolutional analysis carried out for each half period of the free stream horizontal velocity at the pipeline. An analytical expression of the wake velocity is developed starting from the Navier–Stokes and the boundary layer equations. The time variation of the drag and lift hydrodynamic coefficients is obtained using a Gaussian integration of the start-up function. A reduced scale laboratory investigation in a large wave flume has been conducted in order to calibrate the empirical parameters involved in the proposed model. Different wave and current conditions have been considered and measurements of free stream horizontal velocities and dynamic pressures on a bottom-mounted pipeline have been conducted. The comparison between experimental and numerical hydrodynamic forces shows the accuracy of the new model in evaluating the time variation of peaks and phase shifts of the horizontal and vertical wave and current induced forces.  相似文献   

Characteristics of the boundary layer at the bottom of a solitary wave     

Giovanna Vittori  Paolo Blondeaux 《Coastal Engineering》2011

The results of direct numerical simulations of the boundary layer generated at the bottom of a solitary wave are described. The numerical results, which agree with the laboratory measurements of Sumer et al. (2010) show that the flow regime in the boundary layer can be laminar, laminar with coherent vortices and turbulent. The average velocity and bottom shear stress are computed and the results obtained show that the logarithmic law can approximate the velocity profile only in a restricted range of the parameters and at particular phases of the wave cycle. Moreover, the maximum value of the bottom shear stress is found to depend on the dimensionless wave height only, while the minimum (negative) value depends also on the dimensionless boundary layer thickness. Diagrams and simple formulae are proposed to evaluate the minimum and maximum bottom shear stresses and their phase shift with respect to the wave crest.  相似文献   

Garnet and spinel in fertile and depleted mantle: insights from thermodynamic modelling   总被引：2，自引：1，他引：1  

Luca Ziberna  Stephan Klemme  Paolo Nimis 《Contributions to Mineralogy and Petrology》2013,166(2):411-421

We performed thermodynamic calculations based on model and natural peridotitic compositions at pressure and temperature conditions relevant to the Earth’s upper mantle, using well-established free energy minimization techniques. The model is consistent with the available experimental data in Cr-bearing peridotitic systems and can therefore be used to predict phase relations and mineral compositions in a wide range of realistic mantle compositions. The generated phase diagrams for six different bulk compositions, representative of fertile, depleted and ultra-depleted peridotitic mantle, shown that the garnet + spinel stability field is always broad at low temperatures and progressively narrows with increasing temperatures. In lithospheric sections with hot geotherms (ca. 60 mW/m²), garnet coexists with spinel across an interval of 10–15 km, at ca. 50–70 km depths. In colder, cratonic, lithospheric sections (e.g. along a 40 mW/m² geotherm), the width of the garnet–spinel transition strongly depends on bulk composition: In fertile mantle, spinel can coexist with garnet to about 120 km depth, while in an ultra-depleted harzburgitic mantle, it can be stable to over 180 km depth. The formation of chromian spinel inclusions in diamonds is restricted to pressures between 4.0 and 6.0 GPa. The modes of spinel decrease rapidly to less than 1 vol % when it coexists with garnet; hence, spinel grains can be easily overlooked during the petrographical characterization of small mantle xenoliths. The very Cr-rich nature of many spinels from xenoliths and diamonds from cratonic settings may be simply a consequence of their low modes in high-pressure assemblages; thus, their composition does not necessarily imply an extremely refractory composition of the source rock. The model also shows that large Ca and Cr variations in lherzolitic garnets in equilibrium with spinel can be explained by variations of pressure and temperature along a continental geotherm and do not necessarily imply variations of bulk composition. The slope of the Cr# [i.e. Cr/(Cr + Al)mol] isopleths in garnet in equilibrium with spinel changes significantly at high temperatures, posing serious limitations to the applicability of empirical geobarometric methods calibrated on cratonic mantle xenoliths in hotter, off-craton, lithospheric mantle sections.  相似文献   

Effect of the dilution process on the attenuation of contaminants in aquifers   总被引：1，自引：1，他引：0  

Manuela Lasagna  Domenico Antonio De Luca  Laura Debernardi  Paolo Clemente 《Environmental Earth Sciences》2013,70(6):2767-2784

This paper discusses the effects of the dilution process on levels of aquifer contamination attenuation, developing analytical equations for application in theoretical and practical cases. The key finding is that, in aquifers, the dilution process causes a reduction of the contaminant concentration. Analytical equations for the assessment of the contaminant attenuation capacity, by means of the dilution process in an aquifer, are put forward. In particular, the attenuation of the contaminant concentration in an aquifer, and thus the dilution, is described by the volumetric flow rate per unit width perpendicular to the flow direction (q _u). Moreover, a classification of q _u was developed, considering six classes of attenuation capacity due to dilution. For the equations validation, nitrate contamination attenuation due to dilution was analysed in two sample areas in Piedmont (North-West Italy). The results confirmed the hypothesis, evidencing high nitrate concentrations in areas with low q _u values, connected to low dilution rate of the contaminant in the groundwater; vice versa, low nitrate concentrations were evidenced in areas with high q _u values, due to a high nitrate dilution rate.  相似文献   

Recent geomorphological changes of the middle and lower Calore River (Campania, Southern Italy)   总被引：1，自引：1，他引：0  

Paolo Magliulo  Alessio Valente  Elena Cartojan 《Environmental Earth Sciences》2013,70(6):2785-2805

The geomorphological changes experienced by the middle and lower Calore River (Southern Italy) between 1957 and 1998 were investigated. Data derived from field surveys and interpretation of topographic maps and aerial photos were introduced into a geographic information system (GIS) and processed. The results showed that the Calore River underwent a mean narrowing of 66 %, with a peak of 86 %. The channel length increased by approximately 75 m and the sinuosity from 1.311 to 1.314. The extension of fluvial bars reduced by more than 83 %, while their number increased from 151 to 381. Field evidence of riverbed lowering, such as river terraces formed in the considered time span and exhumation of foundations of bridges and flood-walls, were also constantly detected. Due to these channel adjustments, the Calore River morphology changed from transitional to single-thread. These results were coherent with those reported in the pre-existing literature about channel adjustments experienced by many rivers during the twentieth century. They all were explainable with a reduction of the bedload transport; this latter, in turn, is completely in accordance with the environmental changes that affected the Calore River system in the considered period (i.e., damming and/or channelization of the main tributaries, reduction of liquid discharge due to water withdrawals and sediment mining from the riverbed).  相似文献   

Scenario Reduction Applied to Geostatistical Simulations     

Margaret Armstrong  Aziz Ndiaye  Rija Razanatsimba  Alain Galli 《Mathematical Geosciences》2013,45(2):165-182

Having a large number of geostatistical simulations of a mineral or petroleum deposit provides a better idea of its upside potential and downside risk; however, large numbers of simulated realizations of a deposit may pose computational difficulties in subsequent decision-making phases. Hence, depending on the specific case, there can be a need to select a representative subset of conditionally simulated deposit realizations. This paper examines and extends an approach developed by the stochastic optimization community based on stochastic mathematical programming with recourse and is discussed here in the context of mineral deposits while it is possibly suitable for other earth science applications. The approach is based on measuring the “distance” between simulations and the introduced distance measure between simulated realizations of a mineral deposit is based on the metal above a given set of cutoff grades while a pre-existing mine design is available. The approach is tested on 100 simulations of the Walker Lake data with promising results.  相似文献   

Archaeoseismic evidence for a Late Roman earthquake in the Crotone area (Ionian Calabria, Southern Italy): Seismotectonic implications     

P. Galli  A. Ruga  V. Scionti  R. Spadea 《Journal of Seismology》2006,10(4):443-458

The earthquakes of Calabria are among the strongest in the whole Mediterranean, and they all occurred between the disruptive sequences of 1638 and 1908 (6.7 ≤ M ≤ 7.2). Recent paleoseismological studies show that the return time of these events on their causative fault are larger than 1 ky, thus making ancient earthquakes not recognizable through ‘conventional’ historical research. On the other hand, in those areas characterized by highly erodible deposits, the identification and paleoseismic trenching of active seismogenetic faults has remained a challenge. In order to overcome these issues, we took an archaeoseismological approach for casting light on earthquake occurrence in one of these regions, i.e., the SE area of central Ionian Calabria (Marchesato region). The extensive traces of simultaneous and abrupt collapses in the Roman settlement of Capo Colonna (in the area of the sixth and fifth b.c. sanctuary of Hera Lacinia, near the town of Crotone) are evidence of a disruptive earthquake, which occurred possibly in the third century a.d. To the same event we ascribe the definitive collapse of the Hera Lacinia temple. Considering the seismotectonic framework of the region, this event could be tentatively associated with the active fault system which cuts from NW to SE the whole Sila massif and its Ionian slope, and which should be responsible for all the others known M > 6 earthquakes in the area.  相似文献