CrystalMom: a new model for the evolution of crystal size distributions in magmas with the quadrature-based method of moments     

Colucci?SimoneEmail authorView author&#;s OrcID profile  de’?Michieli?Vitturi?Mattia  Landi?Patrizia 《Contributions to Mineralogy and Petrology》2017,172(11-12):100

Nucleation and growth of crystals, and the resulting crystal size distribution, play a fundamental role in controlling the physical properties of magmas and consequently the dynamics of the eruptions. In the past decades, laboratory experiments demonstrated that size and shape of crystals strongly control the physical properties of magma and lava. Additionally, natural and experimental samples are usually characterized in terms of their crystal size distribution to link it with physical processes that are not directly observable, such as cooling or decompression mechanisms. In this paper, we present CrystalMoM, a new predictive model, based on the quadrature-based method of moments, developed for studying the kinetic of crystallization in volcanic systems. The quadrature-based method of moments, well established in the field of chemical engineering, represents a mesoscale modelling approach that rigorously simulates the space–time evolution of a distribution of particles, by considering its moments. The method is applied here, for the first time, for studying the equilibrium/disequilibrium crystallization in magma, modelling the temporal evolution of the moments of a crystal size distribution. The model, verified against numerical and experimental data, represents a valuable tool to infer the cooling and decompression rates from the crystal size distribution observed in natural samples.  相似文献   

The Varre-Sai chondrite,a Brazilian fall: petrology and geochemistry     

Caio Vinícius Gabrig Turbay Rangel  Marcos Tadeu D’Azeredo Orlando  Cláudio De Morisson Valeriano  Alexandre de Oliveira Chaves 《International Geology Review》2017,59(15):1966-1973

The Varre-Sai meteorite fell along the border of the states of Espirito Santo and Rio de Janeiro, Brazil; on 19 June 2010 at 5:40 pm. Petrography and X-ray powder diffraction (XRD) indicate that the rock is an L5 S4 chondrite, with blastoporphyritic texture that has not been previously described. Geochemical data based on major and rare-earth elements (REEs) show that Varre-Sai is highly similar to the other L chondrites. In Harker diagrams, Varre-Sai, L, and LL chondrites form a single group, suggesting no significant chemical differences between them and contributing to the long-standing debate of whether LL chondrites form a distinct group or whether they are a subset of the L group. Harker diagrams also define a trend from E to H and L/LL chondrites, similar to the cosmochemical trends suggested by other authors. The behaviour of Fe₂O_3t and NiO indicates a relationship with Fe-Ni alloys, and their trend in the diagram suggests some chemical differentiation in the ordinary chondrite parental bodies. The REE content in Varre-Sai, normalized to C chondrites, falls in the field of L chondrites and others, but with slight REE enrichment. The chemical differences in chondrites, mainly in REEs, Fe₂O_3t and NiO could be alternatively interpreted as variations in the inherited agglutinated materials as chondrules, Ca–Al-rich inclusions and Fe–Ni nodules.  相似文献   

Recognition of geochemical footprints of mineral systems in the regolith at regional to continental scales     

P. de Caritat  P. T. Main  E. C. Grunsky  A. W. Mann 《Australian Journal of Earth Sciences》2017,64(8):1033-1043

Understanding the character of Australia's extensive regolith cover is crucial to the continuing success of mineral exploration. We hypothesise that the regolith contains geochemical fingerprints of processes related to the development and preservation of mineral systems at a range of scales. We test this hypothesis by analysing the composition of surface sediments within greenfield regional-scale (southern Thomson Orogen) and continental-scale (Australia) study areas. In the southern Thomson Orogen area, the first principal component (PC1) derived in our study [Ca, Sr, Cu, Mg, Au and Mo at one end; rare earth elements (REEs) and Th at the other] is very similar to the empirical vector used by a local company (enrichment in Sr, Ca and Au concomitant with depletion in REEs) to successfully site exploration drill holes for Cu–Au mineralisation. Mapping of the spatial distribution of PC1 in the region reveals several areas of elevated values and possible mineralisation potential. One of the strongest targets in the PC1 map is located between Brewarrina and Bourke in northern New South Wales. Here, exploration drilling has intersected porphyry Cu–Au mineralisation with up to 1 wt% Cu, 0.1 g/t Au, and 717 ppm Zn. The analysis of a comparable geochemical dataset at the continental scale yields a compositionally similar PC1 (Ca, Sr, Mg, Cu, Au and Mo at one end; REEs and Th at the other) to that of the regional study. Mapping PC1 at the continental scale shows patterns that (1) are spatially compatible with the regional study and (2) reveal several geological regions of elevated values, possibly suggesting an enhanced potential for porphyry Cu–Au mineralisation. These include well-endowed mineral provinces such as the Curnamona and Capricorn regions, but also some greenfield regions such as the Albany-Fraser/western Eucla, western Murray and Eromanga geological regions. We conclude that the geochemical composition of Australia's regolith may hold critical information pertaining to mineralisation within/beneath it.  相似文献   

Community vulnerability to hazards: introducing local expert knowledge into the equation     

Yago Martín  Marcos Rodrigues Mimbrero  María Zúñiga-Antón 《Natural Hazards》2017,87(1):367-381

The accuracies of three different evolutionary artificial neural network (ANN) approaches, ANN with genetic algorithm (ANN-GA), ANN with particle swarm optimization (ANN-PSO) and ANN with imperialist competitive algorithm (ANN-ICA), were compared in estimating groundwater levels (GWL) based on precipitation, evaporation and previous GWL data. The input combinations determined using auto-, partial auto- and cross-correlation analyses and tried for each model are: (i) GWL _t?1 and GWL _t?2; (ii) GWL _t?1, GWL _t?2 and P _t ; (iii) GWL _t?1, GWL _t?2 and E _t ; (iv) GWL _t?1, GWL _t?2, P _t and E _t ; (v) GWL _t?1, GWL _t?2 and P _t?1 where GWL _t , P _t and E _t indicate the GWL, precipitation and evaporation at time t, individually. The optimal ANN-GA, ANN-PSO and ANN-ICA models were obtained by trying various control parameters. The best accuracies of the ANN-GA, ANN-PSO and ANN-ICA models were obtained from input combination (i). The mean square error accuracies of the ANN-GA and ANN-ICA models were increased by 165 and 124% using ANN-PSO model. The results indicated that the ANN-PSO model performed better than the other models in modeling monthly groundwater levels.  相似文献   

Erratum to: Methodology for the analysis of causes of drought vulnerability on the River Basin scale     

Jesús Vargas  Pilar Paneque 《Natural Hazards》2017,87(2):623-657

An inclinometer is a high-precision instrument used to detect displacement along sliding zones. From the time the inclinometer pipe is embedded to inclinometer calibration and to measured data collection and processing, many errors or misjudgments can occur that affect the measurement data. The most important objective for correctly using the observation results is the accurate interpretation of the horizontal displacement profiles obtained from the observation. This study combines existing inclusive data accumulated by a monitoring system on a test sloping site in a campus. It focuses on a comprehensive interpretation of the displacement relationships among different monitoring instruments. This study uses data interpretation principles, categorizes different mechanisms, and performs quantitative analysis and discussion in order to determine the significance presented by various types of monitored information in terms of slope sliding. In addition, in this study, stairwells in a campus building are used, an inclinometer is set up, and calibration equipment for the experiment is added in order to simulate various configurations and observe patterns for displacement curves. The examples for the various conditions include empty holes in the backfill around the pipe, connection points falling off, pipe torsion, relative sliding between layers reaching an extreme condition and leading to stuck pipes, multi-layered sliding, and different thicknesses in sliding zones. The experiment illustrates changes in behavior in terms of environmental factors. The results can be used for instrument calibration and measurement, and as a reference for disaster warning and prevention in hazardous areas with slopes.  相似文献   

Multidisciplinary inferences on a newly recognized active east‐dipping extensional system in Central Italy          下载免费PDF全文

Giusy Lavecchia  Guido Maria Adinolfi  Rita de Nardis  Federica Ferrarini  Daniele Cirillo  Francesco Brozzetti  Raffaella De Matteis  Gaetano Festa  Aldo Zollo 《地学学报》2017,29(1):77-89

We use a multidisciplinary approach to gather preliminary evidence for a Quaternary east‐dipping extensional detachment in Central Italy. This structure crops out in the Sabini‐Eastern Simbruini (SES) and would be hidden at mid‐crustal depths beneath the L'Aquila 2009 (M_w6.3) epicentral area. The SES geometry is reconstructed through geological mapping, structural analysis and seismic line interpretation. The geometry of the mid‐crustal segment, referred to as the Ocre Segment (OS), is interpreted through seismological analyses of the largest aftershock (M_w5.4) of the L'Aquila 2009 sequence. The kinematic compatibility between the SES and the OS under a common SW–NE tensional field is tested through stress inversion of both geological and seismological data. The reliability of OS activation is tested through slip tendency analysis. Like other Italian cases, the SES and the OS are preliminarily interpreted as expressions at different depths of the same unknown east‐dipping extensional detachment, characterized by a ramp–flat–ramp geometry.  相似文献   

Using very long-range terrestrial laser scanner to analyze the temporal consistency of the snowpack distribution in a high mountain environment     

Juan I. López-Moreno  Jesús Revuelto  E. Alonso-González  Alba Sanmiguel-Vallelado  Steven R. Fassnacht  Jeffrey Deems  Enrique Morán-Tejeda 《山地科学学报》2017,14(5):823-842

This study demonstrated the usefulness of very long-range terrestrial laser scanning (TLS) for analysis of the spatial distribution of a snowpack, to distances up to 3000 m, one of the longest measurement range reported to date. Snow depth data were collected using a terrestrial laser scanner during 11 periods of snow accumulation and melting, over three snow seasons on a Pyrenean hillslope characterized by a large elevational gradient, steep slopes, and avalanche occurrence. The maximum and mean absolute snow depth error found was 0.5-0.6 and 0.2-0.3 m respectively, which may result problematic for areas with a shallow snowpack, but it is sufficiently accurate to determine snow distribution patterns in areas characterized by a thick snowpack. The results indicated that in most cases there was temporal consistency in the spatial distribution of the snowpack, even in different years. The spatial patterns were particularly similar amongst the surveys conducted during the period dominated by snow accumulation (generally until end of April), or amongst those conducted during the period dominated by melting processes (generally after mid of April or early May). Simple linear correlation analyses for the 11 survey dates, and the application of Random Forests analysis to two days representative of snow accumulation and melting periods indicated the importance of topography to the snow distribution. The results also highlight that elevation and the Topographic Position index (TPI) were the main variables explaining the snow distribution, especially during periods dominated by melting. The intra- and inter-annual spatial consistency of the snowpack distribution suggests that the geomorphological processes linked to presence/absence of snow cover act in a similar way in the long term, and that these spatial patterns can be easily identified through several years of adequate monitoring.  相似文献   

Assessment of agri-spillways as a soil erosion protection measure in Mediterranean sloping vineyards   总被引：2，自引：1，他引：1  

Jesús Rodrigo-Comino  Stefan Wirtz  Eric C. Brevik  José D. Ruiz-Sinoga  Johannes B. Ries 《山地科学学报》2017,14(6):1009-1022

Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s~(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s~(-1)) and sediment concentrationrates(up to 1538.6 g l~(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.  相似文献   

Elasticity of antigorite,seismic detection of serpentinites,and anisotropy in subduction zones     

Lucile Bezacier  Bruno Reynard  Jay D. Bass  Carmen Sanchez-Valle  Bertrand Van de Moortèle 《Earth and Planetary Science Letters》2010,289(1-2):198-208

Serpentinization of the mantle wedge is an important process that influences the seismic and mechanical properties in subduction zones. Seismic detection of serpentines relies on the knowledge of elastic properties of serpentinites, which thus far has not been possible in the absence of single-crystal elastic properties of antigorite. The elastic constants of antigorite, the dominant serpentine at high-pressure in subduction zones, were measured using Brillouin spectroscopy under ambient conditions. In addition, antigorite lattice preferred orientations (LPO) were determined using an electron back-scattering diffraction (EBSD) technique. Isotropic aggregate velocities are significantly lower than those of peridotites to allow seismic detection of serpentinites from tomography. The isotropic V_P/V_S ratio is 1.76 in the Voigt–Reuss–Hill average, not very different from that of 1.73 in peridotite, but may vary between 1.70 and 1.86 between the Voigt and Reuss bonds. Antigorite and deformed serpentinites have a very high seismic anisotropy and remarkably low velocities along particular directions. V_P varies between 8.9 km s^? 1 and 5.6 km s^? 1 (46% anisotropy), and 8.3 km s^? 1 and 5.8 km s^? 1 (37%), and V_S between 5.1 km s^? 1 and 2.5 km s^? 1 (66%), and 4.7 km s^? 1 and 2.9 km s^? 1 (50%) for the single-crystal and aggregate, respectively. The V_P/V_S ratio and shear wave splitting also vary with orientation between 1.2 and 3.4, and 1.3 and 2.8 for the single-crystal and aggregate, respectively. Thus deformed serpentinites can present seismic velocities similar to peridotites for wave propagation parallel to the foliation or lower than crustal rocks for wave propagation perpendicular to the foliation. These properties can be used to detect serpentinite, quantify the amount of serpentinization, and to discuss relationships between seismic anisotropy and deformation in the mantle wedge. Regions of high V_P/V_S ratios and extremely low velocities in the mantle wedge of subduction zones (down to about 6 and 3 km.s^?1 for V_P and V_S, respectively) are difficult to explain without strong preferred orientation of serpentine. Local variations of anisotropy may result from kilometer-scale folding of serpentinites. Shear wave splittings up to 1–1.5 s can be explained with moderately thick (10–20 km) serpentinite bodies.  相似文献   

Daily morphological changes determined by high‐energy events on an embayed beach: a qualitative model     

Cristina Celia Martins  Michel Michaelovitch de Mahiques  João Manuel Alveirinho Dias 《地球表面变化过程与地形》2010,35(4):487-495

This paper examines the daily morphological responses of Sununga Beach, an embayed beach located on the south‐eastern Brazilian coast, to storms in the South Atlantic Ocean. The main mechanisms and timing of beach erosion and accretion, the relationship between wave height and direction, and beach volume changes are considered, to establish a qualitative model for short‐term embayed beach morphological changes. The methodology consisted of daily topographic surveys during the month of May in 2001, 2002, and 2003, using an RTK‐GPS (real‐time kinematics – global positioning system). Weather and wave model results were used to correlate hydrodynamics and beach morphology. The results indicate that the morphodynamics of Sununga Beach are characterized by a process of beach rotation, which occurred more or less clearly during all three surveys. Unlike what has been commonly described in the literature for longer time intervals and alternations of fair and stormy weather, the beach rotation processes on Sununga Beach occurred under conditions of moderate‐to‐high wave energy change (wave heights greater than 2 m). An integrated evaluation of the behaviour of the meteorological aspects, together with beach morphology, enabled us to recognize that extra‐tropical cyclones were the most important agent in remobilizing the beach planform, whether in beach rotation or in cross‐shore erosion. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献