电法勘探中“双极-偶极”装置的某些特点

本文通过对球体上ρ_s与η_s异常及观测信号的理论计算,阐明了“双极-偶极”装置的异常特征以及“双极- 偶极”较“偶极-偶极”装置在增大观测信号、节约电源方面的主要优点.并由计算提出“临界AB/MN值”的概念,为实际工作中双极距AB的选择提供了理论依据.     

金属矿自然电位的空间分布及其应用

本文根据坑道、钻孔的自然电位观测资料及模型实验结果,提出了金属矿体自然电位空间分布的模型：自然电位空间分布具有正、负异常中心的偶极场特征,自然电流场受半空间的影响较大,矿体埋藏深度较大时形成“8”字形的电位分布,埋藏深度较小时形成似双叶双曲线形态的电位分布。自然电位空间分布的研究表明,观测金属矿床坑道、钻孔的自然电位可以揭露矿体的埋深和产状,且有可能探测钻孔和坑道附近的盲矿体。     

关于频率电磁测深几个问题的探讨(五)——频率电磁测深中电磁场波型及意义

引出水平分层大地面上水平电偶极源及垂直磁偶极源的电磁场分量表达式,对式中核函数进行了变换,分析所含的波型及其与场区的关系,指出了TE型场、TM型场和TEM型场穿透地层的能力。根据波型与地层作用特点,优化电磁场分量,以提高频率电磁测深的探测效果。      

关于频率电磁测深几个问题的探讨(六)——频率电磁测深的电磁场分布与观测参量

分析了水平电偶源与垂直磁偶源的电磁场在半空间大地中的分布特点,指出观测各场分量的合适地面部位。为了定性解释,一般将场分量计算为单分量视电阻率或比值视电阻率;做定量解释时,可直接采用场强进行反演,以减小换算误差。基于当前电偶源与磁偶源的发射功率和电磁场衰减规律,在实际应用中,水平电偶源可探测更大深度(<3 000 m),垂直磁偶源探测浅部(<500 m)。      

瞬变电磁场的波场变换研究

通过对不同条件下层状介质模型瞬变电磁场数据的波场变换、分析,提高了对瞬变电磁场波场变换物理意义的认识,并总结出若干有价值的规律.指出这种通过数学方法变换出的波场,不仅在形式上满足波动方程,而且在导电介质中也存在“传播”现象,在“传播”过程中,当遇到电性分界面时,也存在“反射”和“透射”.这些结论为在瞬变电磁法中,正确合理地引入地震处理解释方法提供了重要的理论依据.     

海洋可控源电磁法几类偶极源探测海底高阻薄层的分辨率分析

针对海洋可控源中几类典型偶极源发射装置,建立各向异性地层高阻油气藏模型,采用基于格林函数的海洋一维地层解析方法,借助电磁场的互易性质,计算得到不同偶极源激发的电磁响应曲线。分析了不同偶极源的电磁响应特征,比较了各电磁场分量振幅和相位归一化曲线幅值。结果表明:垂直电偶极子源的各场的振幅归一化曲线对异常的反应最大,水平电偶极源对高阻层的分辨率高于垂直磁偶极源,水平电偶极源的轴向观测模式和水平磁偶极子源的赤道观测模式均有较好的分辨率,这两种模式下测量的与测线平行的电场和与测线垂直的磁场的分辨率最佳,且存在着最佳收发距,相位也有着近似相同的变化规律。      

鄂尔多斯盆地南缘铜川地区三叠系延长组油页岩中“钙质结核”的成因初探

在鄂尔多斯盆地南缘铜川地区野外露头三叠系延长组长7段油页岩中发现了一些“钙质结核”,野外露头中呈层状发育于长7段油页岩中,形态为“透镜状”、“椭球状”、“飞碟状”,直径大小约为10～70 cm。为探明其岩石类型和主要岩石组分,运用显微镜薄片鉴定、电子探针实验、能谱分析等方法,对结核体进行岩石学特征分析。在此基础上,对其成因进行初步探讨。岩石学特征显示,霸王庄和宜君套滩剖面的“钙质结核”主要成分为重结晶方解石和晶粒方解石,具“球粒状”结构,岩石类型为灰岩;瑶曲聂家河剖面结核体主要岩石类型为泥-粉晶白云岩。分析认为这些“钙质结核”其野外产状和岩石成分,符合热水沉积碳酸盐岩和受热液活动影响的特征,并且铜川地区在长7期具备热液活动的条件。初步认为这些“钙质结核”为湖底热液活动成因的湖相碳酸盐岩。     

大王北洼陷精细油源对比

应用饱和烃生物标志化合物、芳烃、碳同位素和轻烃等地球化学分析资料,多种方法相结合,详细对大王北洼陷3个油田原油进行了油油和油源对比研究。结果表明：大王北洼陷原油具有4种成因类型,分别为来源于沙四段、沙三段、沙一段烃源岩的“沙三型原油”、“沙四型原油”、“沙一型原油”和来源于2套或3套烃源岩的“混合型原油”。“沙三型原油”分布于大王北油田和大65油田,而其它类型原油在英雄滩油田均有分布,并且以受沙三段烃源岩影响的“混合型”为主。沙三段烃源岩是大王北洼陷的主力烃源岩,主力油层内的石油主要是由该层烃源岩贡献的。不同烃源岩的生烃潜力、埋藏生烃演化历史和圈闭的发育历史共同影响了原油类型的分布。     

浅埋煤层地表厚砂土层“拱梁”结构模型研究

西部地区拥有储量最大的浅埋煤田,煤层顶板主要特点是基岩薄,地表为厚砂土层。浅埋煤层采动后,上覆岩层垮落运动将直接波及地表厚砂土层,引起采场强烈来压及地表塌陷等灾害。通过物理模拟试验,揭示了厚砂土层贯通地表裂缝的形成和发展规律,发现地表厚砂土层初次垮落的“拱梁”和周期垮落的“弧形岩柱”结构。通过建立厚砂土层“拱梁”结构数学模型,得出了“拱梁”内的应力分量,并给出了厚砂土层破裂的判据和出现拉裂缝的位置,为确定周期性“弧形岩柱”的有关参数提供了依据,为工作面顶板压力控制和地表塌陷的分析提供了基础。     

秦岭凤太矿田层控铅锌矿床的岩相古地理环境

凤太矿田,位于秦岭中段,陕西省凤县至太白一带。西接“西成矿田”;东邻“柞山矿田”。属秦岭泥盆系多金属、铁成矿带的一部分。本区铅锌矿产丰富,已经发现矿床、矿点数十处,其中大中型矿床四处。对于矿床成因,前人多认为属“中低温热液矿床”。随着工作的不断深入,发现凤太矿田内之铅锌矿体,主要赋存于中泥盆统古道岭组上岩段与星红铺组地层界面附近,严格受此地层层位控制;矿体形态多呈层状、似层状分布,沿走向和倾向均较稳定,矿体与围岩产状基本一致,多呈整合接触;矿石中矿物组份简单,主要金属矿物为闪锌矿、方铅矿;矿石中见有浸染状、胶状、条带状、细纹状等原生沉积作用所形成之构造残余;矿田内岩浆岩不发育,而且矿体空间分布和岩浆岩无明显的直接联系。因此，目前认为应属层控铅锌矿床。自一九七九年以来，在此认识的指导下，经过四年来的找矿实践，使原来四个中小型矿床发展成为四个大中型矿床，储量成倍增长，并在矿田内划分了七个矿化带，使找矿远景不断扩大。为了查明层控铅锌矿床形成规律，我们试图对主要含矿层位-一中泥盆统古道岭组上岩段沉积期的岩相古地理环境进行研究，以总结规律，继续扩大找矿效果。     

巷道围岩中瞬变电磁场三维数值模拟

为了进一步研究井中瞬变电磁法的问题, 建立了巷道和异常体模型, 用推导出的扩散方程的七点差分格式对磁偶极源激发的瞬变场进行了数值模拟。观察到 "烟圈"场在低阻体处早期等值线发生明显畸变, 随着时间的增加影响逐渐减弱;而巷道处的畸变较弱, 持续时间长。根据多个测点计算得到的数据, 绘制了磁场和和磁场对时间导数的等值线断面图, 显示等值线向低阻体处聚集畸变;而磁场对时间导数等值线的畸变可持续较长时间。     

瞬变测深视电阻率曲线的正演计算及其初步解释

本文以垂直磁偶极子发射,接地导线测量这样一种发一收装置为例,讨论了求解时间减电磁场问题的计算方法,具体思路是：用线性滤波法,先求解频率域问题,然后且Ｇａｖｅｒ－Ｓｔｅｈｆｅｓｔ逆拉氏变换法将频率测深正演问题转化为相对应瞬变测深（时间域）正演问题,得到了垂直磁极子场中,水平层状介质表面瞬变电磁场分量的近似表达式,由此计算了视电阻率曲线,并从理论上探讨了瞬变测深视电阻率曲线的垂向分辨能力,本文试图对中     

Highly siderophile element evidence for early solar system processes in components from ordinary chondrites

Separated magnetic and nonmagnetic components from the ordinary chondrites Dhajala (H3.8) and Ochansk (H4) were analyzed for their Re-Os isotopic compositions, as well as for the abundances of the highly siderophile elements (HSE) Re, Os, Ir, Ru, Pt and Pd. The Re-Os isotopic systematics of these components are used to constrain the timing of HSE fractionations, and assess the level of open-system behavior of these elements in each of the different components. The high precision, isotope dilution mass spectrometric analyses of the HSE are used to constrain the origins of, and possible relations between some of the diverse components present in these chondrites. The relative and absolute abundances of the HSE differ considerably among the components. Metal fractions have Re/Os that are factors of ∼2 (Dhajala) to ∼3 (Ochansk) higher than those of their nonmagnetic fractions. The isotopic data for both meteorites are consistent with the largest Re-Os fractionations occurring between metal and nonmagnetic components early in solar system history, although minor to moderate late stage, open-system behavior, and limited variations in Re/Os preclude a precise determination of the age for that fractionation. Open-system behavior is generally absent to minor in the metal fractions, and highly variable in nonmagnetic fractions. Re/Os ratios of nonmagnetic fractions deviate as much as 40% from a primordial isochron. Although some deviations are large for isochron applications, nearly all are negligible with respect to consideration of fractionation processes controlling the HSE.Metal from both meteorites contains about 90% of the total budget of HSE. Metal in Ochansk has ∼2 to 10 times the abundances of the bulk meteorite, while metal from the matrix of Dhajala has ∼2 to 4 times the abundances of the bulk. Fine metal in both meteorites has higher abundances than coarse metal, as has been previously observed. Nonmagnetic components, consisting of chondrules and matrix from which metal was removed in the laboratory, have highly fractionated HSE, characterized by much lower Re/Os than the bulk meteorites, as well as large relative depletions in Pd. The abundances of Re, Os, Ir, Ru and Pt in the nonmagnetic fractions are 14-120 ng/g, much higher than would be expected if they had equilibrated with the metal phases present (150-16,000 ng/g). Collectively, the data are consistent with the HSE budget in ordinary chondrites being dominated by two HSE-bearing carrier phases with distinct compositions. These phases formed separately, and never subsequently equilibrated. Metal components incorporated a HSE carrier that formed at high through moderate temperatures and relatively high pressures, such that the relatively volatile Pd behaved coherently with the more refractory HSE. Nonmagnetic fractions from both chondrules and matrix have HSE compositions that likely require at least two processes that fractionated the HSE. Depletions in Pd are consistent with the presence of HSE carriers that formed as either highly refractory condensates, or residues of high degrees of metal melting. Depletions in Re may implicate a period of relatively high f_O2 during which a volatile form of Re was separated from the other HSE.     

Dipole sources of the main geomagnetic field

The parameters of 15 arbitrary dipoles that, in aggregate, represent the main geomagnetic field (MGF) are estimated to obtain information on the distribution of MGF sources within the Earth in the form of dipoles with an arbitrary position and value of the magnetic moment vector. For an adequate estimation of the results, the method of obtaining the data is described, including: the eccentric dipole model and the derivation of the basic formulas for the magnetic field components of an arbitrary dipole; the method of estimating the parameters of these dipoles, including the computational scheme and optimization method; necessary constraints on the dipoles parameters and a justification of the choice of the initial values in the optimization fitting of the parameters. The results are presented as a map of the location of the centers of the dipoles and their northern axial poles for the epochs 1955 and 2005 and plots of changes in all six parameters of 15 dipoles for 50 years. Most of the dipole centers are located in the lower mantle. The results suggest the existence of current systems in the lower mantle that produce dipole magnetic fields. These currents are provided by the high conductivity of wustite, an important component of the mantle, which, at a depth of 1000-2200 km, transforms to the low-spin state of iron with increased density and electrical conductivity.     

新疆511铀矿床7号采区U-Se-Re-Mo等元素分布特点

Re、Se是中国急需的紧缺矿种,对国家的资源战略与环境安全保障具有重要影响。新疆伊犁盆地511矿床在开采铀的过程中,发现了Re、Se和Mo等元素存在富集的现象。文章以511矿床7号采区为例,采取野外地质调查与室内分析测试及综合研究相结合的技术路线,以探求Re、Se、Mo等元素的分布特点及其与U元素富集之间的关系。研究表明,Re和Se在空间上与砂岩铀矿体密切共生,说明在511矿床中矿源等条件具备的情况下,7号采区内的层间氧化作用促使Re和Se富集成矿,证实了511铀矿床中与U密切相关的Se、Re等元素具有线状分布的特点。     

Interlayer proton transfer in brucite under pressure by polarized IR spectroscopy to 5.3 GPa

In order to investigate the behaviour of proton in brucite under pressure, polarized IR absorption spectra and polarized absorbance distributions of (001) and (110) oriented single crystal of brucite under high pressure were measured by Fourier transform polarized infrared microspectroscopy with diamond anvil cell. A pressure-induced absorption peak at 3645 cm⁻¹ observed under pressures over 2.9 GPa was confirmed to be due to a secondarily formed OH dipole. Polarized absorbance distribution measured under pressure of (110) suggests that the secondary OH dipole is oriented 136.0° to c-axis under 5.3 GPa. Isotropic absorbance distribution of (001) suggests that the secondary OH dipole is disorderly trifurcated. Abrupt onset of the secondary peak and its reverse pleochroism suggest that the process of secondary OH dipole formation is due to proton transfer between layers in brucite. The calculated orientation of the secondary OH dipole consistent with the O-H···O′ angle revealed by neutron diffraction supports the existence of proton transfer along H···O′. The secondary OH dipole implies a new site of proton in brucite under pressure. Received: 6 March 1997 / Revised, accepted: 9 June 1997     

Optimization fitting of the eccentric dipole models to the observed geomagnetic field

We have obtained formulas to calculate the field components of an eccentric dipole (ED) with an arbitrarily directed moment from specified coordinates of the dipole center and from its moment vector. With these formulas, the model dipole position was fitted to the observed geomagnetic field, and the approximation accuracy was estimated according to the standard deviation from IGRF along the X, Y, and Z components; the fitting procedure was checked in several tests.We computed the ED parameters (position and moment orientation) and harmonic coefficients of the ED field for 50 years using surface IGRF components, discovered some changes, and compared them with those according to the Schmidt eccentric dipole model. It was found that the nondipolar contributions to the geomagnetic field increase as the dipole field decays with time, and the dipole center drifts northand eastward away from the Earth's gravity center.The main contribution of the dipole part in the Gaussian spherical harmonic expansion of the geomagnetic field turned out to come from the terms with n of 1 to 5 rather than from two first terms, and the contribution of higher harmonics increases with time. Therefore, the Schmidt ED approximation based on the first eight Gauss coefficients (n ≤ 2) must have only relative significance indicating changes of the parameters. On the other hand, world magnetic anomalies (WMA) show up already in two first Gauss terms rather than since the third term as it has been commonly assumed.     

Distribution characteristics and differential enrichment mechanism of rhenium in molybdenite in the Dexing copper ore fieldSCIEI北大核心CSCD

世界上绝大部分Re赋存在斑岩型矿床的辉钼矿之中,且分布极不均匀。在矿床-矿石-矿物颗粒等不同尺度上,Re含量均存在较大差异,但造成这些差异的因素目前尚不清楚。本文以德兴矿田中富家坞和铜厂二个矿床的辉钼矿为研究对象,在细致的矿相学研究的基础上,对其开展了EPMA、LA-ICP-MS和XRD分析,同时结合前人研究资料,详细探讨了Re在这两个矿床辉钼矿中的分布规律及差异性富集机制。结果显示:富家坞和铜厂均普遍发育两种形态的辉钼矿(细粒集合体型和粗粒片状型),Re在两种辉钼矿中的分布均极为不均,但细粒集合体型相对更富Re,而同一形态辉钼矿铜厂矿床则具有更高的Re含量;同一矿床中辉钼矿结晶越晚,往往越富集Re;个别辉钼矿可见扭结现象,且扭结部位的Re含量更低,暗示后期构造变形可能导致了Re的丢失;两个矿床高Re辉钼矿和低Re辉钼矿的结构均为2H多型,表明Re含量与辉钼矿晶体结构无关。结合前人资料,本文认为成矿流体性质(如温度、盐度等)是导致铜厂和富家坞辉钼矿Re含量差异的主要因素。     

Application of electrical resistivity tomography (ERT) technique to detect underground cavities in a karst area of South Korea

Recently, the electrical resistivity tomography (ERT) technique has been increasingly applied to underground cavity detection filled with groundwater and/or clay. In this study, an ERT survey was conducted to examine the spatial distribution and shape of underground cavities in a karst area in Korea. Numerical ERT modeling and inversion were carried out to select appropriate field survey parameters. Two geological structures, similar to those that exist in the field survey area, were modeled: a sinkhole model and a vein-type structure. Electrode configurations using pole–pole, pole–dipole, dipole–pole, and dipole–dipole arrays were tested with the two geologic models and compared. The numerical modeling showed that the resistivity distribution of the ERT tomogram using the pole–dipole array produced the best representation of the two models. The pole–dipole and pole–pole array configurations were applied in an ERT field survey using six boreholes. The field ERT results show that cavity areas filled with clay or groundwater appeared as low-resistivity anomalies in the limestone formation. This was particularly evident in the inclined vein-type structures attributed to fracture zones, where the field data were similar to the modeling results. Therefore, the ERT technique could be effectively used for detecting underground limestone cavities under similar geological conditions as those at our study area.