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101.
The clonal growth of 9 seagrass species was modeled using a simulation model based on observed clonal growth rules (i.e.,
spacer length, rhizome elongation rates, branching rates, branching angle) and shoot mortality rates for seagrass species.
The results of the model confirmed the occurrence of complex, nonlinear growth of seagrass clones derived from internal dynamics
of space occupation. The modeled clones progressed from a diffuse-limited aggregation (DLA), dendritic growth, identified
with a guerrilla strategy of space occupation, to a compact (Eden) growth, comparable to the phalanx strategy of space occupation,
once internal recolonization of gaps, left by dead shoots within the clone, begins. The time at which seagrass clones shifted
from diffuse limited to compact growth was predictable from the branching angle and frequency of the species and varied from
1 yr to several decades among species. As a consequence the growth behavior and the apparent growth strategy of the species
changes with the development of the clones. The results of the model demonstrate that the emergent complexity of seagrass
clonal growth is contained within the simple set of growth rules that can be used to represent clonal growth. 相似文献
102.
Besides granites of the ilmenite series, in which the anisotropy of magnetic susceptibility (AMS) is mainly controlled by paramagnetic minerals, the AMS of igneous rocks is commonly interpreted as the result of the shape-preferred orientation of unequant ferromagnetic grains. In a few instances, the anisotropy due to the distribution of ferromagnetic grains, irrespective of their shape, has also been proposed as an important AMS source. Former analytical models that consider infinite geometry of identical and uniformly magnetized and coaxial particles confirm that shape fabric may be overcome by dipolar contributions if neighboring grains are close enough to each other to magnetically interact. On these bases we present and experimentally validate a two-grain macroscopic numerical model in which each grain carries its own magnetic anisotropy, volume, orientation and location in space. Compared with analytical predictions and available experiments, our results allow to list and quantify the factors that affect the effects of magnetic interactions. In particular, we discuss the effects of (i) the infinite geometry used in the analytical models, (ii) the intrinsic shape anisotropy of the grains, (iii) the relative orientation in space of the grains, and (iv) the spatial distribution of grains with a particular focus on the inter-grain distance distribution. Using documented case studies, these findings are summarized and discussed in the framework of the generalized total AMS tensor recently introduced by Cañon-Tapia (Cañon-Tapia, E., 2001. Factors affecting the relative importance of shape and distribution anisotropy in rocks: theory and experiments. Tectonophysics, 340, 117–131.). The most important result of our work is that analytical models far overestimate the role of magnetic interaction in rock fabric quantification. Considering natural rocks as an assemblage of interacting and non-interacting grains, and that the effects of interaction are reduced by (i) the finite geometry of the interacting clusters, (ii) the relative orientation between interacting grains, (iii) their heterogeneity in orientation, shape and bulk susceptibility, and (iv) their inter-distance distribution, we reconcile analytical models and experiments with real case studies that minimize the role of magnetic interaction onto the measured AMS. Limitations of our results are discussed and guidelines are provided for the use of AMS in geological interpretation of igneous rock fabrics where magnetic interactions are likely to occur. 相似文献
103.
Estimating concentrations or flow rates along a stream network requires specific models. Two classes of models, recently proposed in the literature, are generalized, to the intrinsic case in particular. We present a global construction by ‘streams’, i.e. on the whole set of paths between sources and outlet. Combining stationary or intrinsic one-dimensional random functions leads to stationary or intrinsic models on segments, with discontinuities at the forks. A construction from outlet to sources, leads to stationary or intrinsic models on each stream, without any discontinuity at the forks. The linear variogram is found as a particular case. The extension to the linear model of coregionalization is immediate, allowing a multivariate modelling of concentrations. To cite this article: C. de Fouquet, C. Bernard-Michel, C. R. Geoscience 338 (2006). 相似文献
104.
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106.
Massimo Chiaradia Dave Banks Robert Cliff Robert Marschik Antoine de Haller 《Mineralium Deposita》2006,41(6):565-573
The origin of the hypersaline fluids (magmatic or basinal brine?), associated with iron oxide (Cu–U–Au–REE) deposits, is controversial. We report the first chlorine and strontium isotope data combined with Cl/Br ratios of fluid inclusions from selected iron oxide–copper–gold (IOCG) deposits (Candelaria, Raúl–Condestable, Sossego), a deposit considered to represent a magmatic end member of the IOCG class of deposit (Gameleira), and a magnetite–apatite deposit (El Romeral) from South America. Our data indicate mixing of a high δ 37Cl magmatic fluid with near 0‰ δ 37Cl basinal brines in the Candelaria, Raúl–Condestable, and Sossego IOCG deposits and leaching of a few weight percent of evaporites by magmatic-hydrothermal (?) fluids at Gameleira and El Romeral. The Sr isotopic composition of the inclusion fluids of Candelaria, Raúl–Condestable, and El Romeral confirms the presence of a non-magmatic fluid component in these deposits. The heavy chlorine isotope signatures of fluids from the IOCG deposits (Candelaria, Raúl–Condestable, Sossego), reflecting the magmatic-hydrothermal component of these fluids, contrast with the near 0‰ δ 37Cl values of porphyry copper fluids known from the literature. The heavy chlorine isotope compositions of fluids of the investigated IOCG deposits may indicate a prevailing mantle Cl component in contrast to porphyry copper fluids, an argument also supported by Os isotopes, or could result from differential Cl isotope fractionation processes (e.g. phase separation) in fluids of IOCG and porphyry Cu deposits. 相似文献
107.
The area of Serravalle, sited in the northern part of the town of Vittorio Veneto (TV), NE Italy, has been the target of a
seismic microzonation campaign. 10 seismic stations have been deployed for a 7 months period to record in continuous mode.
Three stations were installed on bedrock outcrops and seven on sedimentary sites with variable cover thickness. Spectral analyses
have been performed on the collected data-set using the Generalized Inversion Technique (GIT, e.g. Andrews, 1986). In particular,
spectral ratios have been calculated for each station relatively to the average of the three reference, bedrock sites. The
spectral ratios provide quantitative estimates of the seismic motion amplifications which occur in each of the monitored sites.
Two sites show high values of amplification, 5 times larger than signal amplitude at the reference sites, in correspondence
of well discernible peak frequencies of 5 Hz. Results for the other stations show smaller amounts of site amplification spreading
over a broad range of frequencies. Sites where the highest amplifications were recorded all lie on the left bank of the Meschio
River and in areas farther away from its outlet into the plain correlating with the presence of thick layers of Quaternary
deposits. 相似文献
108.
Planning for source water protection in Ontario 总被引:2,自引:0,他引:2
Ontario began developing a drinking water source protection planning process in 2000, after a rural community's water supply was contaminated by pathogens from agricultural runoff. An expert committee report has recommended legislating a new source protection “sphere of jurisdiction” for municipalities; however, no specific new municipal tools or authorities have been proposed as yet. This paper reports findings from an evaluation of the extent to which existing institutional arrangements for land use planning and water management facilitate or constrain source protection by municipalities. A case study of the Regional Municipality of Waterloo suggests there is the potential to link land use planning more strongly to water management through creative use of existing tools, forgoing the need for major institutional changes. 相似文献
109.
110.
Geraldo Magela da Costa Gabriel de Oliveira Polli Márcio A. Kahwage Eddy de Grave Antônio Claret Soares Sabioni Júlio Cesar Mendes 《Physics and Chemistry of Minerals》2006,33(3):161-166
Mössbauer spectra (MS) of blue, green and yellow beryl (ideally Be3Al2Si6O18) containing approximately 1% of iron were obtained at 295 and 500 K. Room temperature (RT) spectra of both blue and green samples showed the presence of an asymmetric Fe2+ doublet (ΔE
Q~2.7 mm/s, δ~1.1 mm/s), with a very broad low-velocity peak. There is no clear evidence for the presence of a ferric component. The MS of the yellow sample at RT consists of an intense central absorption with parameters typical for Fe3+ (ΔE
Q~0.4 mm/s, δ~0.29 mm/s), plus an apparently symmetrical Fe2+ doublet. This sample acquires a light-blue shade upon heating in air at about 620 K. Thermal treatments at high temperatures caused no significant changes in the MS, but the green and yellow beryl acquire a blue colour. All these results are interpreted in relation to the existence of channel water and the distribution of iron among the available crystallographic sites. 相似文献