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1.
A great deal of early-to-mid Early Cretaceous magmatic activities have been recorded in the Zhalantun area of Inner Mongolia,while the late Early to Late Cretaceous magmatic rocks have been barely reported(Guo et al.,2018;Zhang Xiangxin et al.,2017).At present,only a few Late Cretaceous magmatic activities were reported in the Arongqi area,such as volcanic rocks of the Gushanzhen Formation.However,the Gushanzhen Formation lacks accurate isotopic age,and contemporaneous intrusive rocks has not been reported yet.In this work,we collected the volcanic rocks from the Gushanzhen Formation and contemporaneous intrusive rocks in the Zhanlantun and nearby,and aim to figure out the formation ages of volcanic rocks of the Gushanzhen Formation and accompanied intrusive rocks by analyzing zircon U-Pb isotopes(Fig.1). 相似文献
2.
J. Trofimovs B. K. Davis R. A. F. Cas M. E. Barley G. I. Tripp 《Australian Journal of Earth Sciences》2013,60(2):303-327
Two main deformational phases are recognised in the Archaean Boorara Domain of the Kalgoorlie Terrane, Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia, primarily involving south-over-north thrust faulting that repeated and thickened the stratigraphy, followed by east-northeast – west-southwest shortening that resulted in macroscale folding of the greenstone lithologies. The domain preserves mid-greenschist facies metamorphic grade, with an increase to lower amphibolite metamorphic grade towards the north of the region. As a result of the deformation and metamorphism, individual stratigraphic horizons are difficult to trace continuously throughout the entire domain. Volcanological and sedimentological textures and structures, primary lithological contacts, petrography and geochemistry have been used to correlate lithofacies between fault-bounded structural blocks. The correlated stratigraphic sequence for the Boorara Domain comprises quartzo-feldspathic turbidite packages, overlain by high-Mg tholeiitic basalt (lower basalt), coherent and clastic dacite facies, intrusive and extrusive komatiite units, an overlying komatiitic basalt unit (upper basalt), and at the stratigraphic top of the sequence, volcaniclastic quartz-rich turbidites. Reconstruction of the stratigraphy and consideration of emplacement dynamics has allowed reconstruction of the emplacement history and setting of the preserved sequence. This involves a felsic, mafic and ultramafic magmatic system emplaced as high-level intrusions, with localised emergent volcanic centres, into a submarine basin in which active sedimentation was occurring. 相似文献
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<正>Objective The Susong complex zone(SCZ)is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,metamorphic processes and petrogenesis are still 相似文献
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Based on the fracture trace length distribution, conditions for the existence, uniqueness, and correctness of the fracture diameter distribution are given using Warburton’s fracture model. In particular, a solution for the fracture diameter distribution exists and is unique for all trace length probability density functions, h A (y), such that \(h_{A}(y)/\sqrt{y^{2}-x^{2}}\) is Lebesgue integrable on [x,∞). This condition is met by the uniform, exponential, gamma, lognormal, and power-law trace length distributions as well as by the trace length distributions that arise from a deterministic fracture diameter or from a discontinuous fracture diameter length distribution. Exponential, gamma, lognormal, and power-law trace length distributions satisfy necessary conditions for the diameter distribution to be non-negative, and necessary and sufficient conditions for the distribution to have unit integral over the real line. Negative values of the fracture diameter distribution arise when the trace has a uniform distribution and the lower bound of the fracture trace is greater than zero. 相似文献
7.
The need for improved product quality in the aggregates industry is driving the search for greater automation in rock type
identification. In practice, reflectance spectra in visible and near-infrared light may reliably be used for the classification
of rock classes and their variants. Previous studies introduced statistical classification of six rock variants by means of
infrared spectra. The present investigation extends these studies to cover twelve rock types and variants of worldwide economic
importance. These were measured by visible and near-infrared light. Statistical classification of these spectra is highly
challenging due to the high number of groups and the high dimensionality of the data. In functional data analysis, spectra
are regarded as curves instead of vectors of characteristics. To obtain a compact form that is more susceptible to further
analysis, the spectra are represented by a B-spline basis. Two functional versions of linear support vector machines and penalized
functional discriminant analysis are considered for classification. The multiclass problem is addressed by margin trees and
by considering all one-against-one classifications combined with a voting strategy for testing. Since classification error
estimated by 5-fold cross-validation is very low, in particular for penalized discriminant analysis, we conclude that the
rock types can be classified reliably. 相似文献
8.
Ye Zhang 《Mathematical Geosciences》2009,41(2):145-162
A hierarchical geostatistical analysis is conducted on a high-resolution, multiscale hydraulic conductivity (ln K) map, created by scaling up an experimental stratigraphy. Unlike a previous study which evaluates ln K variograms within individual depositional environments, this study analyzes deposits (or samples) that incorporate multiple
depositional environments. Based on conductivity cutoffs selected from a global ln K histogram, an indicator map is created to divide the deposits into 4 categories: sand, silty sand, clayey silt, and clay
(Hierarchy-I). Based on facies and facies assemblage types selected using geological criteria, two more indicator maps are
created at a higher hierarchy (Hierarchy-II) to divide the deposits into 14 units and 2 units, respectively. For each sample,
its experimental ln K variogram is decomposed into 4 auto- and cross-transition component variograms. The decomposition characteristics are then
evaluated against the underlying heterogeneity and specific division rule. The analysis reveals that: (1) ln K cutoffs (sand contents of the physical stratigraphy) can be used to distinguish the shifts in dominant deposition mode; (2) sample
univariate modes depend on the choice of hierarchical division; (3) sample variograms exhibit smooth-varying correlation structures
(exponential-like variograms are observed in samples with a large variance in mean facies length); (4) the decomposition characteristics
are sensitive to the division based on conductivity cutoffs, but not sensitive to the division based on depositional environment
(For all samples, with appropriate division, the sample variogram is closely approximated by the sum of the cross-transition
component variograms.); and (5) at the Hierarchy-II level, the 2-unit division gives similar decomposition characteristics
as the 14-unit division. For the select samples, parsimony in hierarchical division is achieved at the facies assemblage scale. 相似文献
9.
Mg-rich and Fe-rich metatholeiites intruded the Willyama Supergroup of the southern Australian Curnamona Province in the Late Palaeoproterozoic at ca 1700 Ma and 1685 Ma, respectively. Intrusion of the Fe-rich metatholeiites occurred during a period of punctuated extension in the Willyama basin. Major-element concentrations are variable (SiO2 45.4 – 56.5 wt%; Fe2O3? 8.5 – 20.7; TiO2 0.46 – 2.52 wt%; Mg# 70.5 – 29.1) and, in conjunction with trace-element data, support near-closed-system fractionation of a mantle-derived melt with little or no replenishment. Fractionation produced progressively Fe-rich derivative melts. Crystallising phases were dominated by clinopyroxene and olivine, whereas Fe – (Ti) oxide crystallisation was hindered. Primitive mantle-normalised immobile trace elements are characterised by variable Th, Nb, Sr, P and Ti anomalies. Chondrite-normalised rare-earth element patterns for the most primitive, Mg-rich samples from the western Broken Hill Domain have LaN/SmN < 1, whereas the most evolved Fe-rich samples from the Olary Domain have ratios of LaN/SmN > 1. Initial εNd values range between – 2.2 and + 2.7 for the majority of the samples, with the isotopic compositions showing no correlation with differentiation or assimilation. The combined geochemical and isotopic data suggest that the southern Curnamona Province metatholeiites were extracted from a depleted mantle in the western Broken Hill Domain, and a variably enriched, heterogeneous subcontinental lithospheric mantle in the Olary Domain. Magmatism most likely occurred in a backarc basin or intracontinental setting. It is speculated that the geochemically enriched mantle component was derived from subduction-related processes, probably related to pre-Willyama basin accretionary processes along the southern and eastern margins of the North Australian Craton. 相似文献
10.
Lutz Christoph Götze Rainer Abart Erik Rybacki Lukas M. Keller Elena Petrishcheva Georg Dresen 《Mineralogy and Petrology》2010,99(3-4):263-277
We synthesize reaction rims between thermodynamically incompatible phases in the system MgO-Al2O3-SiO2 applying uniaxial load using a creep apparatus. Synthesis experiments are done in the MgO-SiO2 and in the MgO-Al2O3 subsystems at temperatures ranging from 1150 to 1350 °C imposing vertical stresses of 1.2 to 29 MPa at ambient pressure and under a constant flow of dry argon. Single crystals of synthetic and natural quartz and forsterite, synthetic periclase and synthetic corundum polycrystals are used as starting materials. We produce enstatite rims at forsterite-quartz contacts, enstatite-forsterite double rims at periclase-quartz contacts and spinel rims at periclase-corundum contacts. We find that rim growth under the “dry” conditions of our experiments is sluggish compared to what has been found previously in nominally “dry” piston cylinder experiments. We further observe that the nature of starting material, synthetic or natural, has a major influence on rim growth rates, where natural samples are more reactive than synthetic ones. At a given temperature the effect of stress variation is larger than what is anticipated from the modification of the thermodynamic driving force for reaction due to the storage of elastic strain energy in the reactant phases. We speculate that this may be due to modification of the physical properties of the polycrystals that constitute the reaction rims or by deformation under the imposed load. In our experiments rim growth is very sluggish at forsterite-quartz interfaces. Rim growth is more rapid at periclase-quartz contacts. The spinel rims that are produced at periclase-corundum interfaces show parabolic growth indicating that reaction rim growth is essentially diffusion controlled. From the analysis of time series done in the MgO-Al2O3 subsystem we derive effective diffusivities for the Al2O3 and the MgO components in a spinel polycrystal as ${\rm D}_{MgO} = 1.4 \pm 0.2 \cdot 10^{-15}$ m2/s and ${\rm D}_{Al_2O_3} = 3.7 \pm 0.6 \cdot 10^{-16}$ m2/s for T?=?1350 °C and a vertical stress of 2.9 MPa. 相似文献
11.
Used extensively in exploration geology to simulate the natural weathering of mineral deposits, sequential extractions have found new use in environmental studies determining the processes governing metal transport in the environment as well as estimating the bioavailability of contaminants in soils, sediments and waste materials. Many extracting solutions and extraction sequences can be found in the literature and the abilities of any given extracting solution to solubilise a target component of a soil/sediment system is much debated. A study into the mechanisms of aqueous metal uptake by bauxite refinery residues (red mud) revealed the need to establish the selectivity of the sodium acetate solution used to extract metals from carbonates, an extracting solution common to most sequential extraction schemes. The phase extractability of copper and lead removed from solution by hydroxide and carbonate compounds was used to demonstrate and define the abilities of the sodium acetate extracting solution. The experiments in this study demonstrate that 1 M Na acetate, pH 5, also releases metals associated with hydroxide minerals. The impact of these findings will depend on the chemistry and mineralogy of the soil/sediment system or waste material studied. 相似文献
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Methods of Three-part Quantitative Assessments of Undiscovered Mineral Resources: Examples from Victoria,Australia 总被引：1，自引：0，他引：1
Vladimir Lisitsin 《Mathematical Geosciences》2010,42(5):571-582
Quantitative mineral resource assessments following the 3-part form rely on grade and tonnage models and probabilistic estimates
of the number of undiscovered deposits. Assessments completed in Victoria, Australia, indicate that undiscovered mineral resources
can be effectively estimated using grade and tonnage sub-models constructed using only medium- and large-tonnage deposits.
Numbers of undiscovered deposits can be estimated on the basis of expert judgement or entirely by statistical means. Appropriate
mathematical aggregation of individual expert views, expressed at interactive expert workshops, provides robust estimates
of the number of undiscovered deposits. Underestimation of uncertainty, which is common in expert judgement, can be compensated
by the statistical modification of individual interval estimates. In this study, the linear opinion pool was used as a simple
and robust method of mathematical aggregation of multiple expert estimates of the number of undiscovered deposits. A general
regression model, which estimates numbers of undiscovered deposits based on the size of the geologically permissive area and
the median deposit tonnage, provided results generally compatible with those based on expert judgement or local deposit density
models. 相似文献
15.
The sign and the magnitude of the zeta potential must be known for many engineering applications. For clay soils, it is usually
negative, but it is strongly dependent on the pore fluid chemistry. However, measurement of zeta potential time is time-consuming
and requires special and expensive equipment. In this study, the prediction of zeta potential of kaolinite has been investigated
by artificial neural networks (ANNs) and multiple regression analyses (MRAs). To achieve this, ANN and MRA models based on
zeta potential measurements of kaolinite in the presence of salt and heavy metal cations at different pH values have been
developed. The results of the models were compared with the experimental results. The performance indices, including coefficient
of determination, root mean square error, mean absolute error, and variance, were used to assess the performance of the prediction
capacity of the models developed in this study. The obtained indices make it clear that the constructed ANN models were able
to predict zeta potential of kaolinite quite efficiently and outperformed the MRA models. Results showed that ANN models can
be used satisfactorily to predict zeta potential of kaolinite as a rapid inexpensive substitute for laboratory techniques. 相似文献
16.
This paper presents an approach conducive to an evaluation of the probability density function (pdf) of spatio-temporal distributions
of concentrations of reactive solutes (and associated reaction rates) evolving in a randomly heterogeneous aquifer. Most existing
approaches to solute transport in heterogeneous media focus on providing expressions for space–time moments of concentrations.
In general, only low order moments (unconditional or conditional mean and covariance) are computed. In some cases, this allows
for obtaining a confidence interval associated with predictions of local concentrations. Common applications, such as risk
assessment and vulnerability practices, require the assessment of extreme (low or high) concentration values. We start from
the well-known approach of deconstructing the reactive transport problem into the analysis of a conservative transport process
followed by speciation to (a) provide a partial differential equation (PDE) for the (conditional) pdf of conservative aqueous
species, and (b) derive expressions for the pdf of reactive species and the associated reaction rate. When transport at the
local scale is described by an Advection Dispersion Equation (ADE), the equation satisfied by the pdf of conservative species
is non-local in space and time. It is similar to an ADE and includes an additional source term. The latter involves the contribution
of dilution effects that counteract dispersive fluxes. In general, the PDE we provide must be solved numerically, in a Monte
Carlo framework. In some cases, an approximation can be obtained through suitable localization of the governing equation.
We illustrate the methodology to depict key features of transport in randomly stratified media in the absence of transverse
dispersion effects. In this case, all the pdfs can be explicitly obtained, and their evolution with space and time is discussed. 相似文献
17.
Mokhles Kamal Azer Robert J. Stern Jun-Ichi Kimura 《International Journal of Earth Sciences》2010,99(2):245-267
New geochemical, isotopic, and geochronological data and interpretations are presented for late Neoproterozoic intrusive carbonates
and related rocks of southern Sinai, Egypt (northernmost Arabian–Nubian Shield). The Tarr carbonates are coarsely crystalline
and related to explosive emplacement of hypabyssal and volcanic albitite at 605 ± 13 Ma. The carbonates associated with the
albitites are divisible into two types: primary dolomitite and secondary breunneritite (Fe-rich magnesite). The dolomitite
was clearly intrusive but differs from classic igneous carbonatites, containing much lower abundances of incompatible elements,
such as REE, U, Th, Rb, Nb, Y, P, Sr, Zr, Ba, and total alkalies. The breunneritite is a secondary replacement of dolomitite,
probably marking the roots of a vigorous hydrothermal system. Albitites show pristine abundances of major and trace elements
and were not subjected to a major metamorphic overprint. They are relatively more fractionated, alkaline and related to within-plate
A-type magmas, were emplaced in an extensional or non-compressive tectonic regime in the cupola of high-level A-type granite.
Tarr albitites may represent residual magma remaining after near-total crystallization of an A-type granite pluton at depth,
forcibly emplaced into the roof above the cooling pluton. The intrusive dolomitite exsolved from highly differentiated albitite
melt, in the apical regions of a still-buried alkaline “A-type” granite pluton that was rich in CO2; these volatiles migrated upwards and towards the cooler margins of the magma body. Late NNE-SSW extension allowed a shallow-level
cupola to form, into which albitite melts and carbonate fluids migrated, culminating in explosive emplacement of albitite
breccia and intrusive carbonate. Isotopic compositions of Tarr dolomitite and albitite indicate these are consanguineous and
ultimately of mantle origin. Magmatic volatiles fenitized the wall rock, while submarine hydrothermal activity transformed
some of the dolomitite into breunneritite. Recognition of Tarr-type should encourage similar hypabyssal complex intrusions
to be sought for in association with A-type granitic plutons elsewhere. 相似文献
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The computation of sparse representations of data on the sphere (e.g. topographical data) is a crucial step for further processing
such as multiple separation, migration, imaging and sparsity promoting data-recovery. The Easy Path Wavelet Transform (EPWT)
is a new tool for sparse data representation that has recently been introduced for image compression. In this paper we consider
the EPWT on spherical triangulations. It is a locally adaptive transform that works along pathways through the array of function
values and exploits the local correlations of the data in a simple appropriate manner. In our approach the usual discrete
one-dimensional orthogonal or biorthogonal wavelet transform can be applied. The EPWT can be used for defining a multiresolution
analysis on the sphere in which the scaling spaces and the wavelet spaces depend adaptively on the data. Issues of implementation
of the EPWT are also considered. 相似文献
20.
Modeling fractured rocks with numerical methods requires some derived parameters, among which the fracture network connectivity
and the size of the representative elementary volume (REV) are both of crucial importance. Percolation and REV analyses were
made by the RepSim code. The program uses input parameters such as fractal dimension of the fracture midpoints (D
c), length exponent (E) and relative dip (α
r) data. For percolation analysis, the relative sizes of the largest percolation clusters have been calculated by stochastic
realizations of the simulated fracture networks with different parameter triplets. Furthermore, fracture networks can be classified
into three major types on the basis of their (E,D
c,α
r) parameters. For the REV calculations, the porosity of the generated fracture network was calculated. The derived REV size
of a fracture network depends essentially on input parameters and shows a decreasing tendency with increasing D and E and vice versa. The method mentioned above was tested on both metamorphic samples of the Pannonian Basin and Variscan granitoid
rocks of the Mórágy Complex. Percolation values predicted for the Mórágy granite are highly sensitive to alterations in the
input parameters. The amphibolite bodies displayed a modeled fracture network with 80 to 90% of all fractures being interconnected,
while the largest achievable percolation cluster size of gneiss is less than 10%. The REV size of the amphibolite is about
20 m as a result of connected fractures filling the whole body, while gneiss has lower porosity and higher REV (approximately
70 m). 相似文献