Correlation between geological units and mineralized zones using fractal modeling in Zarshuran gold deposit (NW Iran)

In this study, the relation between ore grade and geological characteristic has been studied as a principle and also important conceptual in Zarshuran gold deposit in NW Iran. The main subject in this study was identifying a correlation among the ore grade populations and rock types which could be used in other steps of local estimation in the deposit concentration–number (C–N) fractal model and logratio matrix. The C–N log–log plot reveals six geochemical zones defined by Au?<?0.02 ppm as non-mineralized zone and Au?>?0.02 ppm as mineralized zones. According to geological logging and field geology inspection, black gauge, jasperoid, fault gauge and breccia, and carbonaceous rocks are considered as main rock types which contain major Au mineralized zones. The correlation between geological and fractal modeling by logratio matrix shows that there is a good correlation between geological assumed host rocks and C–N fractal modeling. Black gauge rock type with 93.48 % of overall accuracy shows a significant correlation with supergene zone of fractal model, and jasperoid with 92.5 % and carbonaceous rock type with 52.90 % have a decent correlation with highly and lowly mineralized zone of fractal model relatively. Black gauge, jasperoid, and fault gauge and breccia have an approximately near cooperation in this zone for mineralization.     

全球重要农业文化遗产(GIAHS)保护与适应性管理(英文)

世界各地世代居住的农牧民,以多样化的自然资源为基础,通过因地制宜的生产实践活动,创造、形成并保持着许多独具特色的农业系统和景观。这些在本土知识和传统经验基础上所建立起来的农业文化遗产巧夺天工,充分反映了人类及其文化多样性和与自然环境之间深刻关系的演进历程。这些系统不仅维持并适应了具有全球重要意义的农业生物多样性,形成了丰富的本土知识体系,而且更为重要的是,还为人类持续提供了多样化的产品和服务,保障了食物安全和生计安全,提高了人们的生活质量。但是,许多这样的农业生产系统正面临着包括全球化在内的多种影响因素的威胁。2002年,联合国粮农组织发起了一个国际合作计划"全球重要农业文化遗产(GIAHS)保护与适应性管理"。这一全球性倡议旨在建立这些农业文化遗产及其有关的生物多样性、食物与生计安全、景观与文化的保护体系,并在世界范围内得到认可,实现动态保护和可持续管理。     

Collocated cokriging of iron deposit based on a model of magnetic susceptibility: a case study in Morvarid mine,Iran

Arabian Journal of Geosciences - This paper describes a general framework of incorporating magnetic data as prior information in the modeling of an iron deposit based on sparse drilling boreholes....     

Use of caesium‐137 data to evaluate SHETRAN simulated long‐term erosion patterns in arable lands

The caesium‐137 method of quantifying soil erosion is used to provide field data for validating the capability of the SHETRAN modelling system for predicting long‐term (30‐year) erosion rates and their spatial variability. Simulations were carried out for two arable farm sites (area 3–5 ha) in central England for which average annual erosion rates of 6·5 and 10·4 t ha^?1 year^?1 had already been determined using caesium‐137 measurements. These rates were compared with a range of simulated values representing the uncertainty in model output derived from uncertainty in the evaluation of model parameters. A successful validation was achieved in that the simulation range contained the measured rate at both sites, whereas the spatial variability was reproduced excellently at one site and partially at the other. The results indicate that, as the caesium‐137 technique measures the erosion caused by all the processes acting at a site, it is relevant to hydrologically based models such as SHETRAN only if erosion by wind, agricultural activities and other processes not represented in the model are insignificant. The results also indicate a need to reduce the uncertainty in model parameter evaluation. More generally, the caesium‐137 technique is shown to provide field data that improve the severity of the validation procedure (accounting for internal as well as outlet conditions) and that add spatial variability to magnitude as a condition for identifying unrealistic parameter sets when seeking to reduce simulation uncertainty. Copyright © 2004 John Wiley & Sons, Ltd.     

Applying ultrasonic waves to evaluate the volumetric block proportion of bimrocks

As a result of civilization, a lot of underground and surface structures have been constructed on or within complex rocks such as mélange and lahars. There are many engineering problems related to this group of rocks called block-in-matrix rocks (bimrock). In the literature, the more important parameter controlling the geomechanical characteristics of bimrocks is volumetric block proportion (VBP), and there is much uncertainty related to estimated VBP applying sieve or image analysis. So, in this research, to develop a relation between the VBP and ultrasonic wave velocities and find how the fractal dimension and maximum block size affect the P and S wave velocities, 90 large-scale cubic samples were fabricated and the P and S wave velocities were measured in three perpendicular directions inside the physical samples. The fabricated samples were almost isotropic, and there was a direct relation between ultrasonic wave velocities and VBP. The difference between the evaluated VBP and the real one was in the range of ?10 to +15% when the real VBP was equal or less than 60% and up to +25% when the real VBP was equal to 75%. In general, the fractal dimension had an indirect relation with ultrasonic velocities and there was no dominant trend for ultrasonic wave velocity variation versus the maximum block size.     

Microstructure characterization of mechanically activated hematite using XRD line broadening

The effect of dry milling in a vibratory mill on the structural changes and microstructural characteristics of hematite using different methods was investigated. We have described the line profile analysis (LPA) to extract the size of coherently diffracting domains and the lattice strain of activated hematite in a vibratory mill. The Warren–Averbach and Williamson–Hall methods were used as the main tools for characterization. The changes in the particle size, surface area and new phase formation of hematite concentrate were also investigated. It was concluded that the breakage and agglomeration of particles take place mainly at lower and higher levels of specific energy input, respectively. The pores in agglomerates remain accessible for the nitrogen gas. Milling of hematite increased specific surface area up to 18.4 m²/g. The hematite milled under various levels of specific energy input did not undergo a significant reaction or phase transformation during milling. The Williamson–Hall method confirms its merit for a rapid overview of the line broadening effects and possible understanding of the main causes. The anisotropic character of line broadening for deformed hematite as a function of specific energy input was revealed. Higher level of specific energy input favors the generation of small crystallite size, higher microstrain, BET surface area, amorphization and line breadth. The Warren–Averbach method suggested that the nanocrystalline hematite with grain sizes of 73.5–12.2 nm was formed by mechanical treatment using different milling intensities in the vibratory mill. The root mean square strain (RMSS) at L = 10 nm varies between 1.7 × 10^− 3 and 4.0 × 10^− 3 depending on the level of energy input. Limits in the applicability of Williamson–Hall method and reliability of the results are discussed in detail.     

The impact of pyrite variability, dispersive transport and precipitation of secondary phases on the sulphate release due to pyrite weathering

The objective of this study was to investigate the impact of flow, transport and geochemical parameters in the unsaturated and saturated zones on the release of SO₄ from overburden lignite spoil piles into the adjacent lake. A vertical one-dimensional model was set up using the reactive transport simulator SULFIDOX in order to account for the unsaturated zone. The SULFIDOX model was calibrated for effective diffusion using measured O₂ in the gas phase and SO₄ concentrations in the liquid phase from the unsaturated zone of the heap. The results show high sensitivity to O₂ supply and initially present gypsum, but the inclusion of secondary mineral precipitation in equilibrium is of minor importance for the results. To account for the transport of released SO₄ from the saturated zone into the surface water, scenarios were performed by using SULFIDOX results as input concentration for a two-dimensional vertical model set up with PROCESSING MODFLOW and MT3D. These scenarios indicate a rising discharge of SO₄ into the adjacent lake due to continued pyrite weathering for 80 a. Results are highly sensitive to dispersivity, whereas the spatial variability of pyrite distribution did not show any influence on the results. The consideration of initially present gypsum shows a major effect on the modelled SO₄ release.     

Fuzzy logic mineral potential mapping for copper exploration using multi-disciplinary geo-datasets,a case study in seridune deposit,Iran

This paper describes the application of the knowledge-based fuzzy logic method to integrate various exploratory geo-dataset in order to prepare a mineral prospectivity map (MPM) for copper exploration. Different geophysical layers which are derived from the magnetic and the electrical surveys, along with the ones extracted from the background geology (i.e., lithology, fault and alteration) and geochemical data are incorporated in such process. Seridune copper deposit located in the Kerman province of Iran is the case study to delineate its high potential zones of Cu-bearing mineralization for drilling additional boreholes. Four layers from the magnetic data involving upward continuation, analytic signal, reduced to pole and pseudo gravity are assigned in the multi-disciplinary geo-dataset to locate the intrusive complexes responsible for Cu mineralization. The apparent resistivity, chargeability and sulfide factor layers acquired from geo-electrical data are also included in the final preparation of MPM. Then the normalized weights of seven geophysical, three geological and one geochemical evidential layers as main criteria are determined based upon the knowledge of expert decision makers. Fuzzy operators (i.e., Sum and Gamma) are applied to integrate these exploratory features. To evaluate the performance and applicability of the approach, the productivity of the drilled boreholes (Cu concentration multiplied by ore thickness) are used to validate the produced MPMs. It is shown that an optimum correlation coefficient of 0.86 exists between the MPM values and Cu productivity criterion along drilled boreholes.     

An investigation into the effects of block size distribution function on the strength of bimrocks based on large-scale laboratory tests

Considering the geomechanical characteristics of rocks which are a mixture of rock blocks embedded in fine grain matrix can be challenging due to their complex structure and difficulty in preparing representative in situ or laboratory samples. In the literature, this group of rocks is called block in matrix Rocks (bimrocks). In this paper, the effects of volumetric block proportion (VBP), maximum block size, and distribution function on the compressive strength and failure patterns of these rocks were considered by executing the unconfined compressive test on large-scale synthetic samples. The compressive strength of bimrocks was found to have a direct relation with VBP and maximum block size and an indirect one with fractal dimension in accordance with multivariable regression analysis. The fracture patterns of remolded samples were changed from an inter-granular facture to a matrix and between-granular one by the reducing the VBP and increasing the fractal dimension. In addition, the failure mechanism was spalling for the low values of VBP and the high values of fractal dimension and it was changed to shear failure by increasing VBP and decreasing fractal dimension.     

Rupture process of November 6, 1988, Lancang-Gengma, Yunnan, China, earthquake of M s=7.6 using empirical Green’s function deconvolution method

The empirical Green’s function deconvolution technique is applied to the November 6, 1998,M _s=7.6, Yunnan, China earthquake to study the rupture process of this event. An aftershock ofM _s=6.3 is taken as the empirical Green’s function. Recordings of these two events at six stations of China Digital Seismographic Network (CDSN) are employed. Deconvolution results show that this event is a relatively simple event. Directivity analysis indicates that the rupture was initiated at hypocenter and propagated bilaterally and early symmetrically towards the northwest and southeast directions with a total length of 70 km and a time duration of 19 s. The rupture velocity is estimated to be about 2.0 km/s. Contribution No. 98A01004, Institute of Geophysics, State Seismological Bureau, China. This study is supported by the Chinese Joint Seismological Science Foundation(95-07-411).