Statistical Features of Vein Systems in the Hishikari Epithermal Gold Deposit, Japan

Abstract. The Hishikari epithermal gold deposit consists of parallel vertical veins hosted by the Quaternary volcanic rocks (QVR) and Cretaceous sedimentary rocks (CSR) at the shallow and deep levels, respectively. In order to reveal the litholog‐ical influence on the evolution of vein systems in the Hishikari field, vein density, width, spacing and position were statistically examined using cores sampled from three boreholes. The statistical features of the veins identified were summarized as follows, (i) The QVR have lower mean vein densities than the CSR. (ii) The former has smaller deformation degrees (ratios of total vein width per length) than the latter, (iii) Cumulative frequencies of vein density obey negative‐exponential distributions in both the types of rocks, (iv) Cumulative frequencies of vein width obey power‐law distributions with exponents of about ‐1 in both the types of rocks, but consist of two segments in the CSR. (v) Cumulative frequencies of vein spacing obey lognormal distributions with coefficients of variation between 1.8 and 3.5 in both the types of rocks. And (vi) fractal dimensions of vein position are between 0.45 and 0.52 at measure lengths between 0.1 and 10 m without distinctive difference between the two types of rocks. The feature (i) indicates higher ductility of the QVR against fracturing than the CSR. The feature (ii) implies that large deformation was accumulated in rocks themselves (e.g., alteration zones) in addition to the veins examined in the QVR compared to only the veins in the CSR. The feature (iv) suggests that the vein systems in the CSR reached a stage at which the several selected large veins grew as main conduit, that potentially provided pathways for ore‐forming fluids to ascend from deep levels. The coefficients of variation of vein spacing and fractal dimensions of vein position (features v and vi) indicate clustered distribution of the veins in the field. This study might be helpful for a better understanding of lithological influence on the evolution of vein systems not only in the Hishikari field but also in other fields.     

Statistical mapping of PM10 concentrations over Western Europe using secondary information from dispersion modeling and MODIS satellite observations

This paper illustrates the use of statistical techniques to standardize ground based measurements of particulate matter (PM10). Concentrations are interpolated over Western Europe using uncertain secondary information from a chemical transport model and of aerosol optical thickness from MODIS satellite observations. A consistent overview of PM10 concentrations over Europe based solely on ground based measurements is complicated by differences between countries. Different monitoring methods are used and calibrations are applied. There also is an inherent limitation to the spatial representativeness of ground based measurements. Validation showed that adding secondary information from either the chemical transport model or the satellite observations improved the PM10 mapping. The URMSE decreased from 5.14 to 4.26 and 4.58, respectively. A combination of both sources of secondary information gave the most accurate and precise predictions, with an URMSE of 3.62. This means that both external sources contain additional information on the spatial distribution of PM10 concentrations and should therefore be preferred.     

Theory of EM monitoring of sea bottom geothermal areas

Monitoring of geophysical conditions of marine sedimentary basins is necessary for predicting seismic events and for adaptation of geothermal technologies for seismically active (as a rule) sea bottom geothermal areas. These conditions are characterized by seismo-hydro-electromagnetic (EM) geophysical field interaction in the presence of gravity. Based on the main physical principles, geophysical and petrophysical data, we formulate a mathematical model of seismo-hydro-EM interaction in a basin of a marginal sea and calculate the transformation of a seismic excitation in the upper mantle under the central part of the sea of Japan into the low-frequency (0.1 to 10 Hz) EM signals at the top of the sea bottom sedimentary layer, at the sea surface and in the atmosphere up to the lower boundary of the ionosphere. Physics of the EM generation and propagation process is shown including: generation of EM waves in the upper mantle layer M by a seismic wave from under M, spatial modulation of diffusive EM waves by a seismic wave, stopping of the EM wave arrived (before the seismic P wave) from the upper mantle at the top of the sediments because of the high electric conductivity of seawater (3.5 S/m), immediate penetration of the EM wave through the seawater thickness after the delayed seismic P wave shock into the sea bottom, and EM emission from the sea surface into the atmosphere. Let us note that the EM signal in the sea bottom sediments is the first measurable signal of a seismic activation of geological structures beneath the seafloor and this signal is protected by seawater from the influence ionosphere disturbances. Amplitude of the computed magnetic signals (300, 200, 50, and 30 pT at the ocean–atmosphere interface and at the height of 10, 30 and 50 km, respectively), their predominant frequency (0.25 Hz), the delay of the seismic P wave in regard to the magnetic signal for the receivers at the shore (20 s), the amplitude of temperature disturbances in sediments (up to 0.02 K), the parameters of the long (150 km) tsunami wave of a small (up to 20 cm) amplitude far from the shore and other values that characterize the seismo-hydro-EM process are of the orders observed. Recommendations for the EM monitoring of dynamic processes beneath seafloor geothermal areas are given.     

ESDA支持下的城市地价分布信息提取

在城市地价分布信息提取中，因地价信息空间位置的相关性和样本数量的有限性，传统统计学的两个基本假设（样本独立与大样本）不易实现。为此，采用探索性空间数据分析（ESDA）技术，对地价数据作空间统计分析。在ESDA分析中，数据结构必须满足正态分布，同时，要对全局趋势分析和方向分析等予以考虑，才能得到误差较小的分析结果。镇江市实例研究表明，该地区地价样点的空间数据结构呈对数分布，存在二阶趋势和北北东方向，合理步长为375 m。     

基于数学形态学的毫米波图像边缘检测方法

讨论了数学形态学的基本原理及其在毫米波辐射遥感图像边缘检测中的应用，提出了一种用灰度形态变换原理进行检测的有效算法。对一幅毫米波图像的实验结果表明，该算法具有较好的抗噪和边缘提取能力，比传统的基于模板的图像边缘检测算法具有更好的边缘提取效果。     

火山碎屑岩层孔隙度的计算方法

火山碎屑岩岩性复杂,因此骨架参数难以选择,影响孔隙度的计算效果。针对大庆油田海拉尔盆地的火山碎屑岩储层,对计算孔隙度的一般性方法进行研究;针对火山碎屑岩的成分,根据岩心分析资料计算其理论骨架参数值;采用3层BP神经网络进行训练学习,通过编程处理,实现人工神经网络计算火山碎屑岩储层孔隙度,其结果与岩心分析孔隙度比较,平均误差小于2%,能满足储量计算要求。     

Geo-environmental quality assessment in Jharia coalfield,India, using multivariate statistics and geographic information system

A study on geo-environmental quality assessment in Jharia coalfield, India, has been attempted using multivariate statistical analysis and geographic information system (GIS) modelling techniques. Water quality index, calculated for each sample network station in the study area to assess the suitability of water for human consumption, revealed very poor to poor quality surface water and mine water. Air quality indexing indicated that there is no sample station with clean air as per the Indian standards, which indicate the hazardous air quality. Multi-criteria evaluation (MCE), a potential GIS tool, has been applied to the delineation of various degrees of stressed villages in terms of quality of life (QoL). The role of various geo-environmental parameters such as quality of groundwater, surface water, mine water and air together with village population densities has been emphasized for delineation of the environmentally stressed villages in Jharia coalfield. The integrated cluster analysis and MCE approach provide an improved means to geo-environmental quality assessment in Jharia coalfield in terms of QoL. The assessment study is aimed to be used for future coal mining, ensuring ecologically sustainable industrial development, particularly in a coalfield.     

Reducing fluctuations in the sample variogram

In the analysis of regionalized data, irregular sampling patterns are often responsible for large deviations (fluctuations) between the theoretical and sample semi-variograms. This article proposes a new semi-variogram estimator that is unbiased irrespective of the actual multivariate distribution of the data (provided an assumption of stationarity) and has the minimal variance under a given multivariate distribution model. Such an estimator considerably reduces fluctuations in the sample semi-variogram when the data are strongly correlated and clustered in space, and proves to be robust to a misspecification of the multivariate distribution model. The traditional and proposed semi-variogram estimators are compared through an application to a pollution dataset.     

Analytical modelling of wintertime coastal jets in the Adriatic Sea

Two diagnostic models, reproducing circulation generated in a marginal sea by variable density, have been developed. The models’ domain is a 2D transverse section for which analytical solutions have been obtained. They describe the winter situation in the northern Adriatic, with a strong vertical mixing present and the density maximum dominating the centre of the basin. Both models employ Boussinesq-type parametrisation of friction and linear slip at the bottom. The first model allows for frictional departure from hydrostatic equilibrium and includes vertical friction only. The second one is hydrostatic but allows for lateral friction as well. The results obtained by the two models are similar and to some extent dependent on the vertical and bottom friction. They reproduce several well known characteristics of the Adriatic circulation (cyclonic surface flow, downwelling in the central and larger part of the basin compensated by upwelling in the coastal zone) but also predict some phenomena that are still not well understood. A conspicuous feature of the model results are coastal jets, which were observed in the Adriatic on several occasions. The present models show that the distance of jets from the coasts depends on lateral friction: it is found to vary from 1 up to 10 km on the Italian side and between 2 and 15 km on the Croatian side. Both models reproduce the west–east asymmetry, with the wider current on the east side of the basin. The asymmetry is a subject on which conflicting empirical results exist in the Adriatic. In the two models cyclonic flow occupies the whole water column, which disagrees with some recent theoretical findings of the near-bottom anticyclonic flow and thus leaves the issue open.     

Modelling the hydrodynamics of offshore sandbanks

This paper describes the details of a quasi-three-dimensional model (3DBANK), which has been developed to investigate medium and long-term morphological evolution and development of offshore sandbanks. The model is based on a three-dimensional tidal module using the Galerkin-eigenfunction method, but also includes four sub-modules to compute: the instantaneous bedform characteristics from which the temporal and spatial variations of the shear stresses at the sea bed can be derived; the suspended sediment concentration through the water column; the bed-load and suspended sediment fluxes at a point-in-plan; and the resulting morphological changes, respectively. The model also includes the effects of the wind and waves at the sea surface, as well as the wave–current interaction (WCI), and operates with full hydrodynamic and morphodynamic interaction. The components of the model were tested against laboratory and field data, and the complete model was then applied to Middlekerke Bank off the Flemish coast where extensive field measurements were taken during the European Community (EC) funded Circulation and Sediment Transport Around Banks (CSTAB) Project using various advanced instrumentation including STABLE and HF OSCR. Comparisons of the model results with the field measurements and observations show that the model is capable of reproducing the current and wave-induced bedforms, bed roughness, tidal currents and tidal residuals around the sandbank satisfactorily, and can be used to study the long-term sandbank evolution under various offshore conditions. This paper, however, focuses on the hydrodynamic aspects of the model, while the details of the morphological components will be given in a companion paper.