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1.
Chan-Hee Park Christof Beyer Sebastian Bauer Olaf Kolditz 《Environmental Geology》2008,55(8):1755-1766
Precise and efficient numerical simulation of transport processes in subsurface systems is a prerequisite for many site investigation
or remediation studies. Random walk particle tracking (RWPT) methods have been introduced in the past to overcome numerical
difficulties when simulating propagation processes in porous media such as advection-dominated mass transport. Crucial for
the precision of RWPT methods is the accuracy of the numerically calculated ground water velocity field. In this paper, a
global node-based method for velocity calculation is used, which was originally proposed by Yeh (Water Resour Res 7:1216–1225,
1981). This method is improved in three ways: (1) extension to unstructured grids, (2) significant enhancement of computational
efficiency, and (3) extension to saturated (groundwater) as well as unsaturated systems (soil water). The novel RWPT method
is tested with numerical benchmark examples from the literature and used in two field scale applications of contaminant transport
in saturated and unsaturated ground water. To evaluate advective transport of the model, the accuracy of the velocity field
is demonstrated by comparing several published results of particle pathlines or streamlines. Given the chosen test problem,
the global node-based velocity estimation is found to be as accurate as the CK method (Cordes and Kinzelbach in Water Resour
Res 28(11):2903–2911, 1992) but less accurate than the mixed or mixed-hybrid finite element methods for flow in highly heterogeneous media. To evaluate
advective–diffusive transport, a transport problem studied by Hassan and Mohamed (J Hydrol 275(3–4):242–260, 2003) is investigated here and evaluated using different numbers of particles. The results indicate that the number of particles
required for the given problem is decreased using the proposed method by about two orders of magnitude without losing accuracy
of the concentration contours as compared to the published numbers. 相似文献
2.
Physically based modeling approach has been widely developed in recent years for simulation of dam failure process resulting
from overtopping flow. Due to the lack of field data, there exist few applications to natural quake dams with complex erosion
mechanisms. This paper presents a physically based simulation of the failure process of the Tangjiashan Quake Dam formed as
a result of the “May 12, 2008” Wenchuan earthquake in China. The one-dimensional model adopted features as cost saving but
enables capturing the main characteristics of the failure process, where selective sediment transport and gravitational slope
collapse are accounted for. The simulated flow hydrograph and breach progression process are generally in good agreement with
the observed data. Unsteadiness and non-uniformity are found to be substantial characteristics of breach progression during
the failure process of natural quake dams. Sensitivity analysis showed that the Manning resistance coefficient and the erodibility
coefficient in Osman and Thorne’s (J Hydraul Eng 114(2):134–150, 1988) model significantly influences the flow peak discharge but has less influence on its occurrence time, while the velocity
lag coefficient associated with bed-load transport may affect the two breaching parameters substantially. 相似文献
3.
Mingbin Huang D. G. Fredlund M. D. Fredlund 《Geotechnical and Geological Engineering》2010,28(2):105-117
There are significant advantages in using indirect pedo-transfer functions, (PTFs) for the estimation of unsaturated soil
properties. The pedo-transfer functions can be used for the estimation of the soil–water characteristic curve (SWCC) which
in turn is used for the estimation of other unsaturated soil properties. The accuracy of the indirect pedo-transfer function
method for the estimation of the SWCC depends on the PTF and the equation used to best-fit the particle-size distribution
(PSD) data. The objectives of this study are to: (1) evaluate the performance of the Fredlund et al. (Can Geotech J 37:817–827,
2000) equation for best-fitting the particle-size distribution, (PSD) data, and, (2) compare the predictions made by two of the
commonly used PTFs; namely, Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) and Fredlund et al. (Can Geotech J 39:1103–1117, 2002), for estimating the SWCC from the PSD. The authors used 258 measured PSDs and SWCC datasets from the Loess Plateau, China,
for this study. The dataset consisted of 187 silt–loam soils, 41 loam soils, 11 silt–clay–loam soils, 10 sand–loam soils,
6 silt–clay soils, and 3 loam–sand soils. The SWCC and PSD datasets were measured using a Pressure Plate apparatus and the
pipette method, respectively. The comparison between the estimated and measured particle-size distribution curves showed that
the Fredlund et al. (Can Geotech J 37:817–827, 2000) equation closely prepresented the PSD for all soils in the Loess Plateau, with a lower root mean square error (RMSE) of
0.869%. The comparison between the estimated and measured water contents at the same suction showed that the Fredlund et al.
(Can Geotech J 39:1103–1117, 2002) PTF performed somewhat better than the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) function. The Fredlund et al. method had RMSE value of 0.039 cm3 cm−3 as opposed to 0.046 cm3 cm−3 for the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) method. The Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF produced the closest predictions for sand–loam, loam–sand, and loam soils, with a lower RMSE for gravimetric water content
ranging from 0.006 to 0.036 cm3 cm−3. There were consistent over-estimations observed for silt–loam, silt–clay–loam, and slit–clay soils with RMSE values for
gravimetric water content ranging from 0.037 to 0.043 cm3 cm−3. The measured and estimated air-entry values were closest when using the Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF. The measured and estimated maximum slopes on the SWCC were closest when using the Arya and Paris (Soil Sci Soc Am J
45:1023–1030, 1981) PTF. 相似文献
4.
James M. D. Day Colin G. Macpherson David Lowry D. Graham Pearson 《Contributions to Mineralogy and Petrology》2012,164(1):177-183
Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) report laser-assisted fluorination (LF) and secondary ionization mass spectrometry (SIMS) 18O/16O datasets for olivine grains from the Canary Islands of Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro. As with prior studies of oxygen isotopes in Canary Island lavas (e.g. Thirlwall et al. Chem Geol 135:233–262, 1997; Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010), these authors find variations in δ18Ool (~4.6–6.0 ‰) beyond that measured for mantle peridotite olivine (Mattey et al. Earth Planet Sci Lett 128:231–241, 1994) and interpret this variation to reflect contributions from pyroxenite-peridotite mantle sources. Furthermore, Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) speculate that δ18Ool values for La Palma olivine grains measured by LF (Day et al. Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) may be biased to low values due to the presence of altered silicate, possibly serpentine. The range in δ18Ool values for Canary Island lavas are of importance for constraining their origin. Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) took a subset (39 SIMS analyses from 13 grains from a single El Hierro lava; EH4) of a more extensive dataset (321 SIMS analyses from 110 grains from 16 Canary Island lavas) to suggest that δ18Ool is weakly correlated (R 2 = 0.291) with the parameter used by Gurenko et al. (Earth Planet Sci Lett 277:514–524, 2009) to describe the estimated weight fraction of pyroxenite-derived melt (Xpx). With this relationship, end-member δ18O values for HIMU-peridotite (δ18O = 5.3 ± 0.3 ‰) and depleted pyroxenite (δ18O = 5.9 ± 0.3 ‰) were defined. Although the model proposed by Gurenko et al. (Contrib Mineral Petrol 162:349–363, 2011) implicates similar pyroxenite-peridotite mantle sources to those proposed by Day et al. (Geology 37:555–558, 2009, Geochim Cosmochim Acta 74:6565–6589, 2010) and Day and Hilton (Earth Planet Sci Lett 305:226–234, 2011), there are significant differences in the predicted δ18O values of end member components in the two models. In particular, Day et al. (Geochim Cosmochim Acta 74:6565–6589, 2010) proposed a mantle source for La Palma lavas with low-δ18O (<5 ‰), rather than higher-δ18O (c.f. the HIMU-peridotite composition of Gurenko et al. in Contrib Mineral Petrol 162:349–363, 2011). Here we question the approach of using weakly correlated variations in δ18Ool and the Xpx parameter to define mantle source oxygen isotope compositions, and provide examples of why this approach appears flawed. We also provide reasons why the LF datasets previously published for Canary Island lavas remain robust and discuss why LF and SIMS data may provide complementary information on oxygen isotope variations in ocean island basalts (OIB), despite unresolved small-scale uncertainties associated with both techniques. 相似文献
5.
In this paper, we present an original methodology for recovering boundary conditions and hydraulic parameters in an aquifer
domain. Boundary data are identified from the knowledge of over-specified boundary data on another part of the boundary. Then
parameters, here wells’ positions and fluxes, are recovered by the use of the reciprocity principle (Andrieux and Ben Abda,
Mech Res Commun 20:415–420, 1993; Andrieux and Ben Abda, Inverse Probl 12:553–564, 1996). The boundary recovering method is based on the minimization of an energy-like error functional (Andrieux et al., Inverse
Probl 22:115–133; Baranger and Andrieux, 2010). 相似文献
6.
Lázaro Valentin Zuquette Janaina Barrios Palma Osni José Pejon 《Environmental Geology》2006,50(3):371-387
This study was carried out in the Córrego do Vaçununga basin constituted of eolic sandstones of Botucatu Formation and residual unconsolidated materials (>90%), considered the most important unconfined aquifer in Brazil, in the city of Luiz Antonio, State of São Paulo, Brazil. Laboratory and in situ tests were performed to characterize the unconsolidated materials in terms of basic physical properties, potential infiltration rate, suction and hydraulic conductivity. The results for infiltration and overland flow depths were obtained according to Morel-Seytoux and Khanji (Water Resour Res 10(4):795–800, 1976) and Chu (Water Resour Res 14(3):461–466, 1978) adaptation of the Green and Ampt [J Agr Sci 4(Part 1):1–24, 1911] model for steady and transient rainfalls, respectively. Rainfall data were collected from January of 2000 to December of 2002, and 12 scenarios were defined considering the intensity and durations. Rather than high homogeneity in terms of the texture of unconsolidated materials, the infiltration and overland flow ratio depends on the type of land use and associated management practices. The results showed that rainfall with high intensity and short duration do not produce high overland flow ratio as we have observed for transient scenarios with long duration and low intensities. 相似文献
7.
The comment of Martin Oczlon contains some significant contributions to the topics discussed in the article of Huckriede et
al. (Int J Earth Sci 93:414–431, 2004). Contrary to Oczlon’s comment, the central results of Huckriede et al. (Int J Earth Sci 93:414–431, 2004) are clearly different from the tectonic model of Oczlon (Geol Rundsch 83:20–31, 1994). Additionally, there is no reason for a new interpretation of the 40K/40Ar muscovite cooling-ages from allochthonous units. 相似文献
8.
The Sumatra–Andaman Tsunami left distinctive sedimentological and geomorphological signatures in the area of Khao Lak. Fine-grained
sediments, predominantly layers of cohesive, carbonate-rich, fine-sandy silt with thicknesses of 1–10 cm, erosionally overlying
pre-tsunami sandy soils and sediments, represent the most common tsunami deposits in the study area. Petrographically, they
differ significantly from other coastal sediments and affiliated soils. Due to their grain size and corresponding clay mineral
content, muddy shelf sediments (sub-wave base) are indicated as a main source. The present results suggest that indications
of shelf influence, although varying regionally, might contribute to the identification of fine-grained tsunami sediments
and their differentiation from storm sediments. However, the observed differences of tsunami sediments to soils and other
coastal sediments, especially with respect to carbonate mineralogy, might disappear in short geological time under conditions
of intensive weathering and bioturbation. At Cape Pakarang, hundreds of boulders with up to 24 tons were deposited on the
foreshore and upper shoreface. Applying Nott’s (Earth Planet Sci Lett 210:269–276, 2003) formulas, minimum flow velocities of 3.9 m/s are required to transport the largest boulders. The devastating tsunami effect
of both, onshore flow and backflow, is documented by damaged human constructions. Geomorphological effects include intensive
widening of estuary mouths and the development of erosional channels. Now, estuary mouths are reduced, and erosional channels
cut off from the sea due to the formation of a post-tsunami beach ridge. 相似文献
9.
The low-temperature heat capacity (C
P) of stishovite (SiO2) synthesized with a multi-anvil device was measured over the range of 5–303 K using the heat capacity option of a physical
properties measurement system (PPMS) and around ambient temperature using a differential scanning calorimeter (DSC). The entropy
of stishovite at standard temperature and pressure calculated from DSC-corrected PPMS data is 24.94 J mol−1 K−1, which is considerably smaller (by 2.86 J mol−1 K−1) than that determined from adiabatic calorimetry (Holm et al. in Geochimica et Cosmochimica Acta 31:2289–2307, 1967) and about 4% larger than the recently reported value (Akaogi et al. in Am Mineral 96:1325–1330, 2011). The coesite–stishovite phase transition boundary calculated using the newly determined entropy value of stishovite agrees
reasonably well with the previous experimental results by Zhang et al. (Phys Chem Miner 23:1–10, 1996). The calculated phase boundary of kyanite decomposition reaction is most comparable with the experimental study by Irifune
et al. (Earth Planet Sci Lett 77:245–256, 1995) at low temperatures around 1,400 K, and the calculated slope in this temperature range is mostly consistent with that determined
by in situ X-ray diffraction experiments (Ono et al. in Am Mineral 92:1624–1629, 2007). 相似文献
10.
Coupling of oceanic and continental crust during Eocene eclogite-facies metamorphism: evidence from the Monte Rosa nappe,western Alps 总被引:1,自引:0,他引:1
Thomas J. Lapen Clark M. Johnson Lukas P. Baumgartner Giorgio V. Dal Piaz Susanne Skora Brian L. Beard 《Contributions to Mineralogy and Petrology》2007,153(2):139-157
High precision U–Pb geochronology of rutile from quartz–carbonate–white mica–rutile veins that are hosted within eclogite
and schist of the Monte Rosa nappe, western Alps, Italy, indicate that the Monte Rosa nappe was at eclogite-facies metamorphic
conditions at 42.6 ± 0.6 Ma. The sample area [Indren glacier, Furgg zone; Dal Piaz (2001) Geology of the Monte Rosa massif: historical review and personal comments. SMPM] consists of eclogite boudins that are exposed
inside a south-plunging overturned synform within micaceous schist. Associated with the eclogite and schist are quartz–carbonate–white
mica–rutile veins that formed in tension cracks in the eclogite and along the contact between eclogite and surrounding schist.
Intrusion of the veins at about 42.6 Ma occurred at eclogite-facies metamorphic conditions (480–570°C, >1.3–1.4 GPa) based
on textural relations, oxygen isotope thermometry, and geothermobarometry. The timing of eclogite-facies metamorphism in the
Monte Rosa nappe determined in this study is identical to that of the Gran Paradiso nappe [Meffan-Main et al. (2004) J Metamorphic Geol 22:261–281], confirming that these two units have shared the same Alpine metamorphic history. Furthermore,
the Gran Paradiso and Monte Rosa nappes underwent eclogite-facies metamorphism within the same time interval as the structurally
overlying Zermatt-Saas ophiolite [∼50–40 Ma; e.g., Amato et al. (1999) Earth Planet Sci Lett 171:425–438; Mayer et al. (1999) Eur Union Geosci 10:809 (abstract); Lapen et al. (2003) Earth Planet Sci Lett 215:57–72]. The nearly identical P–T–t histories of the Gran Paradiso, Monte Rosa, and Zermatt-Saas units suggest that these units shared a common Alpine tectonic
and metamorphic history. The close spatial and temporal associations between high pressure (HP) ophiolite and continental
crust during Alpine orogeny indicates that the HP internal basement nappes in the western Alps may have played a key role
in exhumation and preservation of the ophiolitic rocks through buoyancy-driven uplift. Coupling of oceanic and continental
crust may therefore be critical in preventing permanent loss of oceanic crust to the mantle. 相似文献
11.
Soil radon concentration levels in Deir Abu-Said District, Irbid, Jordan were measured for several depths using CR-39 detectors,
in the summer 2004 for six geological formations, namely, Wadi umm ghudran (WG), Wadi esSir “massive” limestone, Amman silicified
limestone (ASL), Al-Hisa phosphatic limestone (AHP), Muwaqqar chalky-marl (MCM), and Basalt. Using a model (Yakovleva in Ann
Geophys 48(1):195–198, 2005) based on the solution of the diffusion equation in the quasi-homogenous approximation, the characteristics of radon transport
were calculated. Radon flux density from the Earth’s surface, the depth Z
eq, at which the equilibrium value of soil radon concentration is reached and the convective radon flux velocity (v) for the different soils are calculated and found to be consistent with similar values presented elsewhere. Calculations
indicate that the soil covering WG has a low radon risk while, on the contrary, AHP has a higher radon risk as expected, since
AHP has higher content of uranium. The other formations have intermediate values. The results of the present study confirm
the statement by Yakovleva (Ann Geophys 48(1):195–198, 2005) that two measurements suffice in order to estimate the characteristics of soil radon transport. 相似文献
12.
The high-pressure behavior of Keokuk kaolinite has been studied to 9.5 GPa by infrared spectroscopy using synchrotron radiation.
The kaolinite-I → kaolinite-II and kaolinite-II → kaolinite-III transformations have clear spectroscopic expression, with
discontinuities coinciding with the transformation pressures bracketed by X-ray diffraction (Welch and Crichton in Am Mineral
95:651–654, 2010). The experimental spectra have been interpreted from band assignments derived from density functional theory for the structures
of kaolinite-II and kaolinite-III, using as starting models the ab initio structures reported by Mercier and Le Page (Acta
Crystallogr A B64:131–143, 2008, Mater Sci Technol 25:437–442, 2009) and unit-cell parameters from Welch and Crichton (Am Mineral 95:651–654, 2010). The relaxed theoretical structures are very similar to those reported by Mercier and Le Page (Acta Crystallogr A B64:131–143,
2008, Mater Sci Technol 25:437–442, 2009) in their theoretical investigation of kaolinite polytypes at high pressure. The vibrational spectra calculated from the
quantum-mechanical analysis allow band assignments of the IR spectra to be made and provide insights into the behavior of
different OH environments in the two high-pressure polytypes. The single perpendicular-interlayer OH group of kaolinite-III
has a distinctive spectroscopic signature that is diagnostic of this polytype (ν = 3,595 cm−1 at 9.5 GPa) and is sensitive to the compression/expansion of the interlayer space. This OH group also has a distinctive signature
in the calculated spectra. The spectra collected on decompression are those of kaolinite-III and persist largely unchanged
to 4.6 GPa, except for a continuous blue shift of the 3,595 cm−1 band to 3,613 cm−1. Finally, kaolinite-I is recovered at 0.6 GPa, confirming the kaolinite-III → kaolinite-I transformation previously observed
by X-ray diffraction, and the irreversibility of the kaolinite-II → kaolinite-III transformation. The ambient spectra collected
at the start and finish of the experiment are those of kaolinite-I, and start/finish band frequencies agree to within 6 cm−1. 相似文献
13.
The paper presents a closed-form solution for the convergence curve of a circular tunnel in an elasto-brittle-plastic rock
mass with both the Hoek–Brown and generalized Hoek–Brown failure criteria, and a linear flow rule, i.e., the ratio between
the minor and major plastic strain increments is constant. The improvement over the original solution of Brown et al. (J Geotech
Eng ASCE 109(1):15–39, 1983) consists of taking into account the elastic strain variation in the plastic annulus, which was assumed to be fixed in the
original solution by Brown et al. The improvement over Carranza-Torres’ solution (Int J Rock Mech Min Sci 41(Suppl 1):629–639,
2004) consists of providing a closed-form solution, rather than resorting to numerical integration of an ordinary differential
equation. The presented solution, by rigorously following the theory of plasticity, takes into account that the elastic strain
components change with radial and circumferential stress changes within the plastic annulus. For the original Hoek–Brown failure
criterion, disregarding the elastic strain change leads to underestimate the convergence by up to 55%. For a rock mass failing
according to the generalized Hoek–Brown failure criterion, using the original failure criterion leads to a high probability
(97%) of underestimating the convergence by up to 100%. As a consequence, the onset or degree of squeezing may be underestimated,
and the loading on the support/reinforcement calculated with the convergence/confinement method may be largely underestimated. 相似文献
14.
Victor Kress 《Contributions to Mineralogy and Petrology》2007,154(2):191-204
Experiments were performed in the system O–S–Fe–Ni designed to extend our understanding of the chemistry of sulfide liquids.
Results indicate that adding nickel to Fe-rich sulfide liquids in equilibrium with silicate liquids extends their stability
field to much higher oxygen fugacities and lower sulfur fugacities. Increasing Ni/Fe at a given temperature and sulfur and
oxygen fugacity is accompanied by a significant decrease in the oxygen content of the sulfide liquid. Results of these experiments
are combined with data from the literature to calibrate an associated regular solution model for O–S–Fe–Ni liquids. This model
represents a complete refit of the associated regular solution model of Kress (Contrib Mineral Petrol 139:316–325, 2000). The resulting model is combined with the olivine solution model of Hirschmann (Am Mineral 76:1232–1248, 1991) to explore the effect of variations in oxygen and sulfur fugacities on the distribution of Fe and Ni between olivine and
sulfide liquid. Predicted olivine–sulfide distribution trends parallel those observed by Gaetani and Grove (Geochim Cosmochim
Acta 61:1829–1846, 1997), Gaetani and Grove (Earth Planet Sci Lett 169:147–163, 1999), Brenan and Caciagli (Geochim Cosmochim Acta 64:307–320, 2000) and Brenan (Geochim Cosmochim Acta 67:2663–2681, 2003), but are systematically offset toward lower predicted Ni in the sulfide. Nevertheless our results are consistent with the
assertion that low K
D
os
values in magmatic ore deposits such as the J-M Reef reflect high iron contents in the sulfides combined with relatively
high oxygen fugacities.
相似文献
Victor KressEmail: |
15.
T. W. Sisson J.-I. Kimura M. L. Coombs 《Contributions to Mineralogy and Petrology》2009,158(6):803-829
A basanite–nephelinite glass suite from early submarine Kilauea defines a continuous compositional array marked by increasing
concentrations of incompatible components with decreasing SiO2, MgO, and Al2O3. Like peripheral and post-shield strongly alkalic Hawaiian localities (Clague et al. in J Volcanol Geotherm Res 151:279–307,
2006; Dixon et al. in J Pet 38:911–939, 1997), the early Kilauea basanite–nephelinite glasses are interpreted as olivine fractionation products from primary magnesian
alkalic liquids. For early Kilauea, these were saturated with a garnet–phlogopite–sulfide peridotite assemblage, with elevated
dissolved CO2 contents responsible for the liquids’ distinctly low-SiO2 concentrations. Reconstructed primitive liquids for early Kilauea and other Hawaiian strongly alkalic localities are similar
to experimental 3 GPa low-degree melts of moderately carbonated garnet lherzolite, and estimated parent magma temperatures
of 1,350–1,400°C (olivine–liquid geothermometry) match the ambient upper mantle geotherm shortly beneath the base of the lithosphere.
The ~3 GPa source regions were too hot for stable crystalline carbonate and may have consisted of ambient upper mantle peridotite
containing interstitial carbonate–silicate or carbonatitic liquid, possibly (Dixon et al. in Geochem Geophys Geosyst 9(9):Q09005,
2008), although not necessarily, from the Hawaiian mantle plume. Carbonate-enriched domains were particularly susceptible to further
melting upon modest decompression during upward lithospheric flexure beneath the advancing Hawaiian Arch, or by conductive
heating or upward drag by the Hawaiian mantle plume. The early Kilauea basanite–nephelinite suite has a HIMU-influenced isotopic
character unlike other Hawaiian magmas (Shimizu et al. in EOS Tran Amer Geophys Union 82(47): abstr V12B-0962, 2001; Shimizu et al. in Geochim Cosmochim Acta 66(15A):710, 2002) but consistent with oceanic carbonatite involvement (Hoernle et al. in Contrib Mineral Petrol 142:520–542, 2002). It may represent the melting products of a fertile domain in the ambient upper mantle impinged upon and perturbed by the
sustained plume source that feeds later shield-stage magmatism. 相似文献
16.
Gowri Srinivasan Elizabeth Keating John David Moulton Zora V. Dash Bruce A. Robinson 《Computational Geosciences》2012,16(3):551-563
A convolution-based particle tracking (CBPT) method was recently developed for calculating solute concentrations (Robinson
et al., Comput Geosci 14(4): 779–792, 2010). This method is highly efficient but limited to steady-state flow conditions. Here, we present an extension of this method
to transient flow conditions. This extension requires a single-particle tracking process model run, with a pulse of particles
introduced at a sequence of times for each source location. The number and interval of particle releases depends upon the
transients in the flow. Numerical convolution of particle paths obtained at each release time and location with a time-varying
source term is performed to yield the shape of the plume. Many factors controlling transport such as variation in source terms,
radioactive decay, and in some cases linear processes such as sorption and diffusion into dead-end pores can be simulated
in the convolution step for Monte Carlo-based analysis of transport uncertainty. We demonstrate the efficiency of the transient
CBPT method, by showing that it requires fewer particles than traditional random walk particle tracking methods to achieve
the same levels of accuracy, especially as the source term increases in duration or is uncertain. Since flow calculations
under transient conditions are often very expensive, this is a computationally efficient yet accurate method. 相似文献
17.
Sebastiano Imposa 《Environmental Geology》2008,55(5):1061-1073
In this study 50 seismic events, preceding and accompanying the eruptions occurring in 1981 and 1983, have been considered.
Seismic moments, fault radii, stress drops and seismic energies have been calculated using Brune’s model (J Geophys Res 75:4997–5009,
1970; J Geophys Res 76:5002, 1971); site, anelastic attenuation along the propagation path, geometrical spreading and interaction with the free surface effects
are taken into account. For each event we have also estimated the equivalent Wood–Anderson magnitude (MWAeq) (Scherbaum and
Stoll in Bull Seism Soc Am 73:1321–1343, 1983); relations among all these source parameters have been determined. Furthermore, the hypothesis of self-similarity (Aki in
J Geophys Res 72:1217–1231, 1967) is not verified for events with seismic moments <1012 N-m: in fact the relationship between log-stress drop and log-moment is linear up to a moment of 1012 N-m (events of 1981 eruption), while for higher moments (events of 1983 eruption) the slope of the regression line is not
significantly different from zero. We suppose that such a behaviour is related to a heterogeneous medium with barriers on
the faults. Finally, the main conclusion is that eruptions of 1981 and 1983 differ from one another both in eruptive and seismic
aspects; analysis of seismic energies indicates an increase in Mt. Etna’s activity, confirmed by studies performed on the
following lateral eruption of 1991–1993 (Patanè et al. in Bull Volcanol 47:941–952, 1995), occurring on the same structural trend. 相似文献
18.
The standard thermodynamic properties at 25°C, 1 bar (ΔG
fo, ΔH
fo, S
o, C
Po, V
o, ω) and the coefficients of the revised Helgeson–Kirkham–Flowers equations of state were evaluated for several aqueous complexes
formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta
52:2009–2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359–1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate
the log K of the destruction reactions of these metal–arsenate and metal–arsenite aqueous complexes at pressures and temperatures required
by the EQ3/6 software package, version 7.2b. Apart from the AlAsO4o and FeAsO4o complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally
for the Ca–dihydroarsenate and Ca–hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)–hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79–94, 2006), whereas the disagreement with the log K measured for the Ca–arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and
arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous
solutions deriving from mixing of acid mine waters and surface waters.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
19.
The composition and evolution of an Oligocene regolith on top of the Sesia–Lanzo Zone (Western Alps)
Notburga Kapferer Ivan Mercolli Alfons Berger 《International Journal of Earth Sciences》2011,100(5):1115-1127
An Oligocene paleosurface (regolith) lies on top of the high-pressure metamorphic rocks of the Sesia–Lanzo Zone near Biella,
NW Italy. Only the saprock, the lowermost part in a regolith profile, is preserved. No evidence for any paleosoil can be observed.
Field observations indicate that the regolith developed through in situ mechanical fracturing of the rocks of the Sesia–Lanzo
Zone in a continental environment. Density estimations of the regolith and the underlying rocks of the Sesia–Lanzo Zone confirm
the field observations and imply that a relatively small amount of alteration minerals was formed. The main detected alteration
phases are chlorite, various carbonates, quartz, clay minerals, Fe-oxides, and Fe-hydroxides. Chlorite differing in chemistry
and crystallographic ordering demonstrates different stages of alteration. Oxygen and carbon isotopic composition of carbonates
suggests temperatures higher than surface conditions. Illite and chlorite thermometry indicates temperatures related to the
anchizone (~250–300°C). These data are considered as a robust indication of the re-burial of the regolith together with its
substrate and its volcanic cover. The burial is closely related to the tilting of the preserved stratigraphic sequence formed
by the rocks of the Sesia–Lanzo Zone, the regolith, and the rocks of the Biella Volcanic Suite (Lanza, in Schweiz Miner Petrogr
MItt 57: 281–290, 1977; Lanza, in Geologishe Rundschau 68: 83–92, 1979). Furthermore, the burial is consistent with this sequence of subaerial rocks being very close to the intrusion depth of
the Valle del Cervo Pluton at the time of its emplacement (4–7 km; Zanoni et al., in Rend Online SGI Note Brevi 1: 199–202,
2008; Zanoni et al., in Int Geol Rev 52: 1244–1267, 2010 and references therein). 相似文献
20.
Chapman and Pollack (C and P)[2007, Int J Earth Sci] criticize Hamza et al. [2007, Int J Earth Sci] for using actual heat flux measurements in young oceanic crust instead of values from 1-D cooling models.
The rationalization of C and P and previous authors is that hydrothermal circulation causes the discrepancy between model
and measurement. However, the discrepancy between model values and measured heat flux exists over the entire ocean floor and
is opposite to the perturbations that hydrothermal circulation would superimpose on a conductive system [Hofmeister and Criss
(2005) Tectonophysics 409:199–203]. The error lies in force-fitting a 1-D cooling model to the 3-D oceanic crust [Hofmeister and
Criss (2005) Tectonophysics 395:159–177]. Shortcomings of the 1-D model include mathematical errors, such as use of volumetric rather
than linear thermal expansivity to describe contraction which, by assumption, is limited only to the Z
-direction [Hofmeister and Criss (2006) Tectonophysics]. This 3× error, traceable to McKenzie and Sclater [1969, Bull Vocanol 33–1:101–118], accidentally provides good agreement of model values with globally averaged seafloor depths
for young, but not old ages, and is the sole rationale for using the simplistic cooling model. There is no justification for
selective substitution of erroneous 1-D model values for measurements only for the younger half of the 3-D oceanic crust,
as stridently and arbitrarily promoted by C and P. Hamza et al. [2007, Int J Earth Sci], in contrast, use the scientific method, which calls for discarding models that do not well describe physical
phenomena.
The remainder of this report summarizes the shortcomings of cooling models, particularly the half-space cooling (HSC) model
touted by C and P, and explains how hydrothermal circulation affects heat flux. We focus on the basics, as these have been
misunderstood. With the key issues of C and P being erroneous, it is not necessary to address their remaining comments, many
of which enumerate the vote for an imagined, gargantuan circulation of hot fluid through oceanic basins that is somehow warmed
without removing heat from the rocks. The use of “consensus” to belittle valid challenge is the enemy of the scientific method. 相似文献