High Precision Time Domain Forward Modeling for Crosshole Electromagnetic Tomography

To improve the resolution of crosshole electromagnetic tomography, high precision of forward modeling is necessary. A pseudo-spectral time domain (PSTD) forward modeling was used to simulate electromagnetic wave propagation between two boreholes. The PSTD algorithm is based on the finite difference time domain (FDTD) method and uses the fast Fourier transform (FFT) algorithm for spatial derivatives in Maxwell's equations. Besides having the strongpoint of the FDTD method, the calculation precision of the PSTD algorithm is higher than that of the FDTD method under the same calculation condition. The forward modeling using the PSTD method will play an important role in enhancing the resolution of crosshole electromagnetic tomography.     

作为赋存于花岗岩中钨锡矿化勘探指南的流体包裹体异常——前景展望

Studies of the distribution and abundance of fluid inclusions in granitic quartz associated with granite-hosted Sn-W mineralization of the British Isles reveal local and regional scale anomalies.At a sampling interval of c.5～50m,inclusion abundances increase towards zones of vein and stockwork mineralization exemplified by case history examples from exploration prospects in the Mourne Mountains of Northern Ireland and the Carrock Fell mining district of northwestern England.These steam aureoles provide a greater exploration target than the zone of visible alteration and mineralization and the lithogeochemical halo.But it is important to link them to geochemical data on fluid inclusion compositions,such as the semi-quantitative data from decrepitation-linked,ICP-AES (D-ICP)analysis,to optimize their exploration potential.Regional scale fluid inclusion anomalies,based on sampling intervals of c. 2km from the Sn-W mineralized granites of southwest England also broadly correlate with zones of intense mineralization in some areas. Regional-scale D-ICP analyses of quartz from SW England granites did not provide any convincing regional scale anomalies linked to mineralization except for positive boron anomalies around the centrally-mineralized Birch Tor area of the Dartmoor granite.Follow-up D-ICP analysis of quartz from stream sediments from this area,however,could be used to discriminate between samples related to mineralization from those draining unmineralized areas,using multivariate statistical analysis.At the present stage of development, the main contribution of fluid inclusion studies to mineral exploration is mostly limited to the conceptual stage where they continue to contribute to ore genetic theory and models.Costs and lack of knowledge transfer between research scientists and mineral explorationists limit their direct use during regional and target selection stages of exploration.Analysis of steam sediment quartz,using the more sensitive ICP-MS technique as a variant of the D-ICP method,appears to offer the greatest potential for future development as an exploration tool.     

爆裂法作为快速测定流体包裹体中二氧化碳（和其它气体）含量的手段及其在勘探中的使用：以中国山东和河北省金矿为例

The acoustic decrepitation method heats a small monomineralic sample and counts pressure impulses as the inclusions burst when they develop high internal pressures.For aqueous fluids,the decrepitation temperature is correlated with the homogenisation temperature,but gas rich fluids give a distinct and characteristic low temperature decrepitation peak which can be used to recognize gas rich fluid inclusions.This information is useful in exploration for Au deposits,which are frequently associated with CO_2 rich and sometimes CH_4 rich fluids. This distinctive decrepitation occurs because the CO_2 rich inclusion fluids expand according to the gas law and develop internal pressures high enough to burst the host mineral grain at temperatures well below their homogenisation temperatures.In contrast,aqueous fluids condense to a liquid and vapour phase during post-entrapment cooling.Upon subsequent heating their internal pressures do not increase significantly until after homogenisation to a single phase occurs and hence they do not decrepitate"prematurely"as gas rich inclusions do. This behaviour is usually regarded as an annoyance in conventional microthermometric homogenisation studies,but can readily be used as an exploration aid to find mineralisation deposited from such gas rich fluids.Decrepitation results on samples from Cowra Ck, NSW,Australia,which have also been microthermometrically measured for CO_2 content,show that amounts of less than 5 mole % CO_2 are easily distinguished by decrepitation and amounts as low as 1 mole % CO_2 may be determinable. Examples of the use of acoustic decrepitation in the study of 6 gold mines in the Shandong and Hebei provinces of China are discussed.     

云南茶树林铅锌矿电磁波找矿效果

茶树林铅锌矿，过去认为震旦系赋矿，钻探验证未见矿。本次利用物探方法实施深部探矿。依据物探异常，结合地质规律综合分析，认为是构造控矿。布置验证坑道，沿断裂破碎带发现新的厚大、品位高铅锌矿体，收到良好的找矿效果。     

均匀介质中F-K反偏移法正演模拟

F-K反偏移法正演模拟是在给定地质模型后通过构建人工偏移场,再对人工偏移场进行F-K反偏移来实现。人工偏移场的构建是在地质模型上直接放上经正确拉伸和幅度校正后的地震脉冲子波。F-K反偏移中插值映射采用两点sinc插值,其能避免假同相轴的出现且具有较快的速度。奇异点处理使用泰勒近似展开。最后对凹陷模型进行了F-K反偏移法正演模拟实现,得到了预期的效果。     

Thesaurus and Domain Ontology of Geoinformatics

Geoinformatics is a comparatively new interdisciplinary science and as a part of space informatics uses methods and terminology of informatics and many natural sciences. An ontology of geoinformatics is discussed in the paper, especially concerning its structure, relationships with other ontologies, resources for development and utilization. The ontology of geoinformatics is a kind of domain ontology and has a layered structure consisting of syntactic and semantic layers. The corpus of this ontology is an existing multilingual dictionary of geographical information systems (GIS) enriched with terminology from other external sources. The building of the ontology is preceded by the development of a taxonomy and thesaurus of geoinformatics. The thesaurus database is converted into an OWL ontology by a Visual Basic application. The reusing of the ontology is proposed by its transformation in application ontologies for geoinformatics education.     

一个韧性转换挤压带的变形分解作用：以阿尔金断裂带东段为例

变形构造研究显示阿尔金划分成具有近水平拉伸线理的韧性左行走滑变形域和具有陡角度倾伏拉伸线理的收缩变形域。在ＳＳ与ＰＳ之间的过渡区域还发现中等角度倾伏的拉伸线理。     

Closed Form Solutions of the Two-Dimensional Turning Bands Equation

The turning bands method generates realizations of isotropic Gaussian random fields by means of appropriately summed line processes. For two-dimensional simulations the relation between the isotropic correlation function of the random field and the correlation function to be simulated along the lines is given by an integral equation of Abel type. We present closed form solutions of this integral equation for almost all two-dimensional correlation models encountered in practice and discuss their numerical implementation. As an additional benefit, our tables and illustrations serve as a concise guide to correlation models useful in geostatistics.     

三维结线动力无穷元及其特性研究

研究了文献[2]提出的结线动力无穷元的特性及其参数确定。由于这种单元将衰减函数定义在无穷向结线上,从而不仅可同时考虑多种波动形式,而且对于不同介质,不必通过改变节点坐标分布的形式实现介质间的过渡,而直接以结线上参数的改变来实现,因而可以更好地模拟无穷波动场,使用起来更方便．更容易推广。     

连续变脉宽发送激电方波与自动变周期测量二次场信号

介绍一种新的激电数据采集方式。该方式的主要特点在于一次测量操作可同时获取极化二次场随时间衰减和随深度变化的信息,同时还讨论了实现该采集方式的仪器工作原理和信号测量过程中的一些技术问题。