大地电磁测深法拓扑去静态软件的实现与应用

在连续阵列大地电磁(CEMAP)时间域电场空间拓扑理论研究的基础上,提出了使用单频点多极距ρXY曲线来表现地表横向电性不均匀体所产生的静态效应的思路,在同一观测系统中以人机联作的方式正演计算不均匀体所产生多极距静电压曲线,并用其压制实测多极距ρXY曲线上由静态效应引起的形态起伏,以实现静态校正。开发的拓扑去静态软件,在对实测数据处理的过程中取得显著效果。     

大地电磁测深时间域数据拓扑处理软件的实现及应用

在对电场拓扑理论研究的基础上,将拓扑公式中原记录点与加密点的两个拓扑公式合并成一个公式,通过研究大地电磁时间域数据格式,利用VC++语言编写软件,实现了大地电磁时间域数据的拓扑计算。对实测CEMAP数据进行了拓扑处理,计算结果表明,拓扑处理实现了判别与压制静态效应,通过与空间滤波处理结果对比表明,拓扑处理去静态方法是可行的,且效果优于空间滤波处理。软件界面简单,布局合理,运行高效,处理快速。     

电偶源频率电磁测深中的EX分量

在电偶源频率电磁测深的各场量中,电场ＥＸ分量具有分辨率同,观测信噪比高,不需作近场改正等优点。在有地表电性不均匀引起的静态偏移情况下,可通过转换相位消除静态偏移。因此在资料处理与解释中可不局限于比值电阻率的模式,使频率电磁测深具有更大的灵活性与适应性。     

基于实测积累电荷静电场消除静态效应的方法

频域电磁测深法存在的静态效应问题是由地表浅层电性不均匀体在一次天然电场作用下不均匀体界面积累电荷引起的。积累电荷引起的二次静电场与一次天然电场成线性关系,且二次电场与一次电场的比值K只和地下介质的电性有关,地下介质的电性不变,则K值不变。因此,利用人工源供电的方法,在供电时测量测点一次场和二次场的总场Et;断电后测量二次场E_2,然后求取K值,利用各测点的K值和大地电磁法实测电场计算一次电场,进行静态校正。本文采用有限元二维大地电磁正演模拟地下浅层电性不均匀体产生的静态效应,利用K值校正静态效应,获得了成功。结果显示这种方法能有效压制静态效应,达到静态校正的目的。     

时间域激电测深不同装置数据去耦分析

为消除激电测深中的电磁耦合干扰,根据频率域和时间域可相互转换的理论,采用静态IP和cole-cole参数的全波形IP、延时反演去耦方法,实现了快速去耦,最大限度地保留了激电信息。以山东沂南金矿金场矿区等为例,对时间域激电测深数据进行了去耦前反演与去耦后反演,结果表明：对称四极装置和非常规电极排列的电磁耦合效应随电极距的增大而增强,电磁耦合的影响深度大部分在时间域激电测深反演断面150 m以浅;非常规电极排列采用三极+四极+偶极混合共线装置,其产生的电磁耦合干扰明显大于对称四极装置和单极—偶极装置;非共线单极—偶极装置的时间域激电测深电磁耦合影响较小。     

内蒙古乌尼克吐铅锌矿电法异常特征及试验

以时间域中梯装置激发极化、偶极—偶极装置相位激电测深和可控源音频大地电磁测深在内蒙古乌尼克吐铅锌矿试验结果为例,验证综合电法在寻找矽卡岩型铅锌矿床中的作用及找矿效果。试验结果表明,在激发极化普查测量中应注意供电电极与异常体之间相互关系,否则会产生虚假异常;在勘查区岩矿石电性条件较好的情况下,激发极化面积测量基本能够反映出异常源平面分布情况。在矿(体)与围岩之间的电阻率差异不明显的条件下,较相位激电测深,可控源音频大地电磁测深基本能够推断出矿体的空间赋存位置。所以,时间域中梯装置激发极化与可控源音频大地电磁测深的电法组合在有色金属矿产勘查中可以发挥更大作用。     

天然电场选频法的响应特性分析与应用

静态效应是频率域电磁法应用中不可避免的一种物理现象,通常通过校正方法进行压制或消除。本文提出一种直接利用天然电磁法的静态效应进行浅部电性异常体勘探的新思路,利用天然电场选频法(FSM)能够测量天然交变电磁场在地表所产生的几个不同频率的水平电场分量来研究地下介质的电性变化。首先采用二维有限单元法对FSM开展正演模拟,模拟结果表明：当近地表存在低阻异常体时,地表沿测线方向的水平电场分量曲线与FSM实测曲线形态相同,在低阻体的上方出现十分明显的低电位异常;当计算的频率点增多时,电场分量剖面曲线及其拟断面图会出现静态偏移现象,发现FSM异常实质上主要是静态效应所致。FSM实践应用成果及钻井验证结果表明,当有地下水存在时,FSM实测的剖面曲线及拟断面图会出现明显的静态效应现象,且与CSAMT的勘探成果一致。通过理论与实践可知,直接利用天然电磁场的电场分量开展浅部电性异常体的勘探具有可行性,今后也可利用频率域电磁法的静态效应现象开展浅层地质勘探。     

组合激电测深装置的应用与研究

在有色金属矿产勘查中,激电测深由于工作效率低,仅在重点异常剖面布置几个测深点,未能在工区更多剖面发挥出应有作用。为了提高激电测深野外数据采集工作效率,先后引进梯度电测深及借线遥控电极,并且自制"多极距中梯测深电极集中器",组合成一种新的遥控梯度电测深采集装置。该装置在小极距时采用对称四极(亚对称四极)测深装置,在极距较大的情况下更换成中间梯度测深装置,组合完成激电测深剖面观测。通过遥控电极阵列方式代替传统测深"渐进式"的扩大电极极距方式,提高了电测深的观测效率和解释能力。将这种新的中间梯度激电测深装置应用在构造、地层复杂的金矿勘查区,结果表明,它能大大提高激电测深效率,取得较好勘查效果。     

双频激电法感应耦合的数值计算与分析

在吸收前人工作的基础之上,针对均匀半空间情况下,对双频激电测量中的中梯装置电磁耦合规律与特点进行了研究和计算。在该数值的计算中：①以Maxwell方程为基础,从矢量势及边界条件出发,阐述了各向同性、线性均匀半空间时水平电偶极子源产生的谐变电磁场;②针对中间梯度常规测量装置中的平行线布线方式和共线（供电线呈“n”型）布线方式,推导了电磁感应耦合效应的具体计算公式,计算并分析了EM效应引起的视幅频率随供电极距、工作频率、大地电阻率和偏移距等因素的变化规律。最后,对这二种布线方式的电磁耦合效应进行了比较,平行线布线方式的电磁耦合效应比共线布线方式的电磁耦合效应强烈。     

几种大地电磁测深资料静态位移校正方法的研究与应用

由浅部不均匀电性体所引起的静态位移效应,是大地电磁测深(MT)数据处理工作中必须重点考虑的问题。这里阐述了静态位移效应对MT测深资料的影响,结合两组理论模型的研究,通过分析空间滤波法、曲线平移法、阻抗相位校正法等一些常用MT静态位移校正处理方法,得出了一些有用结论,为野外实测MT数据的校正处理工作提供了参考资料。最后将这些方法应用于某工区实测MT数据的处理中,并结合二维地电模型,说明了MT数据校正处理在开展MT工作中的重要地位。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861