The old calcium plages differential rotation latitudinal profile: Its gross and fine structure evolution with the solar cycle     

Maurizio Ternullo 《Solar physics》1987,112(1):143-151

This work is a study of the rotational properties of the solar calcium plages, during the time interval 1967–1977; only plages older than 4 days have been the object of this research. We have looked systematically for any significant change occurring during the course of the solar cycle, and any kind of ‘anomaly’ or fine structure in the differential rotation latitudinal profile. We find that such a profile undergoes a cyclic transformation, making it assume the highest steepness at the solar maximum; a sudden flattening then occurs in the first years of declining activity; the last years of the cycle, as the first years of the next one, are characterized by intermediate steepness values. Moreover, we find that, in spite of the general belief that the angular rotation rate is continuously decreasing with increasing heliographic latitude, at least two inversions do exist of such an overall tendency:

1. A narrow, minimal angular-rotation-rate strip lies very close to the equatorward margin of the plage production band; this feature shifts continuously, in a wave-like manner, throughout the solar cycle, from 15/18° to 3/6° latitude.
2. A narrow, maximal angular-rotation-rate strip has been observed lying in the neighbourhood of the poleward margin of the activity band; a process of continuous transformation of the rotation rate profile is always active, in a narrow latitude strip on the equatorward side of such a feature, generating new features of the same kind, which replace the older ones, that disappeared due to the equatorward shift of the plage zone. All that simulates an equatorward shift of the observed ‘anomalies’; we observed them until the minimum activity epoch (1976), at 15/18° latitude. Some relations of these features with both torsionai waves (Howard and LaBonte, 1980) and magnetic activity are briefly discussed.

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Alkali metasomatism as a process for trondhjemite genesis: evidence from Aspromonte Unit, north-eastern Peloritani, Sicily     

P. Fiannacca  P. Brotzu  R. Cirrincione  P. Mazzoleni  A. Pezzino 《Mineralogy and Petrology》2005,84(1-2):19-45

Summary Rocks of trondhjemitic composition are widespread in the North-Eastern Peloritani Belt within the Aspromonte Unit, a Hercynian medium- to high-grade metamorphic complex intruded by late-Hercynian peraluminous granites and later affected by MP/LT Alpine metamorphism. Among these trondhjemitic bodies, the Pizzo Bottino trondhjemites form one of the largest, outcropping over about 6km² and up to 400m thick. These rocks display concordant to discordant relationships with associated metamorphic rocks and are often cut by late-Hercynian leucogranitic dykes. The field, petrographic and geochemical features of these trondhjemites are consistent with an igneous origin. Petrographic and geochemical evidences suggest that the trondhjemitic character of the Pizzo Bottino rocks is due to an alkali metasomatism process involving cationic exchange of Na and Ca for K and consequent replacement of K-feldspar by oligoclase in the original granitoids. The major and trace element contents of the Pizzo Bottino trondhjemites are in fact comparable to those of the peraluminous late-Hercynian granitoids from the southern Calabrian-Peloritani Arc (CPA), when the elements directly involved in the alkali metasomatism process (Na, Ca, K, Sr, Ba, Rb) are not considered. The behaviour of REE elements, plus Th and U, also seems to be partially controlled by metasomatic processes, because their abundances vary with the K/Na ratio. Metasomatism seems to be the only viable mechanism involved in the genesis of the Pizzo Bottino trondhjemites. Other trondhjemite generation processes such as fractionation from basaltic parents and partial melting of metabasaltic or metasedimentary sources are ruled out on geological, petrographic and isotopic (Sr, Nd) grounds. Lastly, regional considerations place the metasomatic event during the late Hercynian, after the emplacement of the original granitoids and preceding the intrusion of the leucogranitic dykes, which are not affected by metasomatism.  相似文献   

Equivocal carbonatite markers in the mantle xenoliths of the Patagonia backarc: the Gobernador Gregores case (Santa Cruz Province,Argentina)     

Giorgio?RivalentiEmail author  Alberto?Zanetti  Maurizio?Mazzucchelli  Riccardo?Vannucci  Carlos?A.?Cingolani 《Contributions to Mineralogy and Petrology》2004,147(6):647-670

Amphibole ± phlogopite ± apatite-bearing mantle xenoliths at Gobernador Gregores display modal, bulk-rock and phase geochemical characteristics held as indicators of carbonatitic metasomatism. However, part of these xenoliths has high TiO₂/Al₂O₃ and those displaying the most pronounced carbonatitic geochemical markers modally trend towards harzburgite. Bulk-rock, clinopyroxene and amphibole show Zr, Hf and Ti negative anomalies, which increase at decreasing Na₂O and high field strength elements (HFSE) concentrations. Steady variation trends between xenoliths which have and do not have carbonatitic characteristics suggest a control by reactive porous flow of only one agent, inferred to be initially a ne-normative hydrous basalt (because of the presence of wehrlites) evolving towards silica saturation. Variation trends exhibit cusps when amphibole appears in the mode. Appearance of amphibole may explain the Ti anomaly variations, but not those of Zr and Hf. Numerical modelling [Plate Model (Vernières et al. in J Geophys Res 102:24771–24784, 1997)] gives results consistent with the observed geochemical features by assuming the presence of loveringite. Modest HFSE anomalies in the infiltrating melt may be acquired during percolation in the garnet-facies.In memory of Carlo Rivalenti  相似文献   

The effect of organic compounds in the oxidation kinetics of Cr(III) by H₂O₂     

Maurizio Pettine  Francesca Gennari  Frank J. Millero 《Geochimica et cosmochimica acta》2008,72(23):5692-5707

The oxidation of Cr(III) has been studied in NaCl solutions in the presence of two siderophore models, acetohydroxamic acid (Aha) and benzohydroxamic acid (Bha), the natural siderophore Desferal (DFOB) and the synthetic aminocarboxilate (ethylenedinitrilo)-tetra-acetic acid (EDTA) as a function of pH (8-9), ionic strength (0.01-2 M) and temperature (10-50 °C), at different Cr(III)-organic compound ratios. The addition of Aha and Bha caused the rates to increase at low ligand/Cr(III) ratios and decrease at high ratios. The variation of the pseudo first order rate constant (k₁) as a function of the ligand concentration has been attributed to the formation of three Cr(III)-organo species (1:1, 1:2, 1:3), which can form in the presence of monohydroxamic acids. A kinetic model has been developed that gives a value of 600 (min⁻¹) for the pseudo first order rate constant k_1CrAha²⁺ and values approaching zero for and k_1CrAha3. These kinetic results demonstrate that these monohydroxamic acids are able to bind with Cr(III) under experimental conditions that may occur in natural waters and can increase the oxidation rates of Cr(III) with H₂O₂ by a factor of 3.5 at an Aha/Cr(III) ratio of about 50-100.The monohydroxamic acids also affect the rates on aged products of Cr(III), suggesting that these ligands are able to affect the oxidation rates by releasing reactive Cr(III). DFOB and EDTA do not have a great effect on the oxidation of Cr(III) with H₂O₂. This is thought to be due to the much longer times they need to form complexes with Cr(III) compared to Aha and Bha. The rates for the formation of DFOB and EDTA complexes with Cr(III) are not competitive with the rates of the formation of aged Cr(III). After allowing Cr(III) and DFOB to react for 5 days to form the complex, reaction rates of Cr(III) with H₂O₂ appear to be lowered probably because of steric hindrance of the chelated Cr(III).  相似文献   

Flow analysis in a channel with flexible vegetation using double-averaging method     

Maurizio Righetti 《Acta Geophysica》2008,56(3):801-823

The paper addresses the problem of the resistance due to vegetation in an open channel flow, characterized by partially and fully submerged vegetation formed by colonies of bushes. The flow is characterized by significant spatial variations of velocity between vertical profiles that make the traditional approach based on time averaging of turbulent fluctuations inconvenient. A more useful procedure, based on time and spatial averaging (Double-Averaging Method) is applied for the flow field analysis and characterization. The vertical distribution of mean velocity and turbulent stresses at different spatial locations has been measured with a 3D Acoustic Doppler Velocimeter (ADV) for two different vegetation densities where fully submerged real bushes (salix pentandra) have been used. Velocity measurements were completed together with the measurements of drag exerted on the flow by bushes at different flow depths. The analysis of velocity measurements allows depicting the fundamental characteristics of both the mean flow field and turbulence. The experimental data show that the contribution of form-induced stresses to the momentum balance cannot be neglected. The mean velocity profiles and the spatially averaged turbulent intensity profiles allow inferring that the vegetation density is a driving parameter for the development of a mixing layer at the canopy top in the case of submerged vegetation. Moreover, the net upward turbulent momentum flux, evaluated with the methodology proposed by Lu and Willmarth (1973), appears to be damped for increased vegetation density; this finding can rationally explain the reduction of the suspended sediment transport capacity typically observed in free surface flows over a vegetated bed.  相似文献   

Population MCMC methods for history matching and uncertainty quantification     

Linah Mohamed  Ben Calderhead  Maurizio Filippone  Mike Christie  Mark Girolami 《Computational Geosciences》2012,16(2):423-436

This paper presents the application of a population Markov Chain Monte Carlo (MCMC) technique to generate history-matched models. The technique has been developed and successfully adopted in challenging domains such as computational biology but has not yet seen application in reservoir modelling. In population MCMC, multiple Markov chains are run on a set of response surfaces that form a bridge from the prior to posterior. These response surfaces are formed from the product of the prior with the likelihood raised to a varying power less than one. The chains exchange positions, with the probability of a swap being governed by a standard Metropolis accept/reject step, which allows for large steps to be taken with high probability. We show results of Population MCMC on the IC Fault Model—a simple three-parameter model that is known to have a highly irregular misfit surface and hence be difficult to match. Our results show that population MCMC is able to generate samples from the complex, multi-modal posterior probability distribution of the IC Fault model very effectively. By comparison, previous results from stochastic sampling algorithms often focus on only part of the region of high posterior probability depending on algorithm settings and starting points.  相似文献   

Inheritance of Jurassic rifted margin architecture into the Apennines Neogene mountain building: a case history from the Lucretili Mts. (Latium, Central Italy)     

Andrea Bollati  Sveva Corrado  Maurizio Marino 《International Journal of Earth Sciences》2012,101(4):1011-1031

The western Lucretili Mts. in the central Apennines (Latium, Italy) have been recently re-mapped in great detail and are the subject of combined stratigraphic, sedimentological and structural investigations. In this paper, we present a new stratigraphic interpretation of the Jurassic paleogeography of western Lucretili Mts., where a rift-derived intrabasinal paleo-high of the Alpine Tethys has been identified for the first time by means of facies analysis and biostratigraphic dating. Recognised facies associations, combined with dated stratigraphic sections, allow to define the morphology of the structural paleo-high and to identify the associated gravity-driven deposits (olistoliths) accumulated in the surrounding basin. Furthermore, we investigated the modes of interaction between Jurassic extensional structures and the subsequent contractional patterns developed during the Tertiary mountain building. In detail, the role played during Apennines tectonics by the paleo-escarpments bounding the paleo-high and by the surrounding olistoliths has been analysed. The paleo-escarpments either acted as focussing features for ENE-directed frontal thrust ramp localisation and were offset with small shortening amounts or reactivated as NNE striking high angle transpressional faults or preserved the original geometries as a result of variable orientation of paleo-escarpments with respect to the Neogene compressive stress field (with ENE oriented sigma1). Newly formed ENE striking tear faults connect these either inherited or neo-formed discontinuities. This complex stratigraphic and structural pattern is substantially different from the previous interpretations of this portion of the central Apennines based on a hypothesised layer-cake stratigraphy deformed by neo-formed Neogene thrusts. This contribution strengthens the importance of integrating facies analyses and structural investigations to detect the influence of pre-orogenic structures on compressive structural patterns, in an area where commercial seismic lines are not available and cannot help in reconstructing the subsurface geometries.  相似文献   

Variability of the health effects of crystalline silica: Fe speciation in industrial quartz reagents and suspended dusts—insights from XAS spectroscopy     

Francesco Di Benedetto  Francesco D’Acapito  Fabio Capacci  Gabriele Fornaciai  Massimo Innocenti  Giordano Montegrossi  Werner Oberhauser  Luca A. Pardi  Maurizio Romanelli 《Physics and Chemistry of Minerals》2014,41(3):215-225

We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe–K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous Fe^III oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences).  相似文献   

Occurrence of phlogopite in the Finero Mafic layered complex     

Tommaso Giovanardi  Maurizio Mazzucchelli  Alberto Zanetti  Antonio Langone  Massimo Tiepolo  Anna Cipriani 《Central European Journal of Geosciences》2014,6(4):588-613

Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major- and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif.  相似文献   

Effects of desferrioxamine-B on the release of arsenic from volcanic rocks     

Barbara Casentini  Maurizio Pettine 《Applied Geochemistry》2010

Microorganisms play an important role in As mobilization into groundwater by directly influencing As speciation or indirectly inducing solubilisation from As-bearing phases, such as Fe, Mn and Al oxides. Iron oxide dissolution could also be induced by siderophores, small-molecule compounds produced by microorganisms to favour Fe uptake. Well waters exceeding the potable water limit of 10 μg As L⁻¹ (0.133 μM) have been widely reported in geothermal areas. Mechanisms responsible for these high As concentrations have not yet been thoroughly elucidated and the complexity of As mobilization in volcanic aquifers is still open to multiple interpretations. The present study was based on batch release experiments aimed at verifying and quantifying the effect of siderophores on As mobilization from volcanic rocks (lava, tuff, peperino and fallout deposit) at different pH and ligand concentration. In the experiments the siderophore trihydroxamate desferroxamine B (Dfob) was used and its effect on As release from volcanic rocks was manifest after the first days. The most favourable pH for As release was pH 6 while concentrations above 250 μM Dfob considerably enhanced As and Fe concentrations in solution. The As release from rocks was between 2.0–10% at pH 6 and 2.4–8.8% at pH 8. The As/Fe ratio in solution changed with time suggesting different release mechanisms and higher mobility of As compared to Fe during the first phase of the experiment. The presence of siderophore increased Fe dissolution rates up to 10 orders of magnitude. The As release correlated with Al, Mn, Fe, Si, V, Ga and Sb and the release of all these elements increased with increasing Dfob concentration. In alkaline environments also Cu, Zn and Pb were mobilized. The presence of siderophores represents a possible trigger for As mobilization from iron binding minerals to the water phase, with interesting implications for groundwater quality, plant uptake and bacterial communities.  相似文献