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本文介绍了甚低频电磁法的基本原理及其野外工作方法,并论述了甚低频电磁法在四川雀儿山错坝活动断裂中的应用。沿该断裂实测22条甚低频测线,其中16条测线结果显示出水平电场及电阻率的低值异常,其异常范围宽度60~120m。实践表明,甚低频电磁法在确定断层的空间展布时是行之有效的,最后笔者总结了应用甚低频工作所得出的几点认识及体会。 相似文献
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甚低频电磁法是一种基于电磁原理的地球物理手段,该方法对寻找受断裂构造控制的脉状矿床效果显著。在矿床勘查中,一般利用目标矿区(及外围)地质体对电磁波作用反映的物性特征进行扫面工作,用以快速发现覆盖层之下的矿化构造系统。本文通过对大兴安岭西南段某铜多金属矿点的实际应用,发现矿区内存在明显的甚低频异常,该异常为矿致异常,展示了良好的成矿前景。实践表明,在具备甚低频电磁法应用的地质、地球物理条件的前提下,通过对观测数据进行技术处理,并结合矿区针对性的地质研究,能够有效地揭示覆盖区断裂构造体系的产状及空间展布规律,达到对隐伏-半隐伏金属矿床快速评价的目的。 相似文献
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本文结合实例阐述了甚低频电磁法在基基山区找术水中的工作方法及应用效果。实践证明,甚低频电磁法作为一种物探剖面手段,具有效果好、工效高、成本低等优点,实为在山区找水工作中的好方法。 相似文献
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矿体地质-地球物理快速定位预测模型——以丰宁门营铜多金属矿床为例 总被引:1,自引:1,他引:0
随着矿产勘查实践的日益深入及找矿难度的增大,矿区大比例尺矿体定位预测已成为矿产勘查评价领域一项重要的研究课题.甚低频电磁法(VLF-EM)作为一种浅层物探技术,具有仪器轻便、方法简单、经济高效等优点,已经得到了国内外矿产勘查实践的检验,且勘查效果明显.简要叙述了甚低频电磁法及其数据处理的基本原理,并应用该方法对丰宁门营铜多金属浅地表隐伏一半隐伏矿体进行快速定位预测,建立了目标矿体的地质一地球物理模型;实践研究表明,在矿体地质研究的基础上,应用甚低频电磁法进行大比例尺地球物理数据采集,并应用磁倾角数据的Fraser滤波、线性滤波技术可以很好提取地球物理异常,揭示隐伏矿体的空间产状及延伸,为勘探工程的部署提供优选靶区.值得指出的是,由于地质噪声及外界电磁噪声的干扰,结合研究区地质特征的分析并对解译成果进行二维三维的表达和对比研究,是正确提取矿致异常的关键. 相似文献
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草原覆盖区隐伏金属矿体定位预测——以大兴安岭中南段某铅锌矿点为例 总被引:7,自引:0,他引:7
草原区一般第四纪覆盖严重,为在草原浅层覆盖区有效地寻找、定位隐伏矿体,利用甚低频电磁法和EH4电磁成像系统开展了地球物理勘查工作。研究表明,甚低频电磁测量和EH4连续电导率剖面测量均能确定出明显的异常,且由两种技术手段得出的异常相互对应。说明甚低频电磁法和EH4电磁成像系统的联合应用是草原浅层覆盖区找寻隐伏矿体的有效技术方法。 相似文献
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袁庆华 《物探化探计算技术》1981,(2)
前言地质部科技局于1980年12月在重庆召开了“地面甚低频电磁法和仪器”鉴定会。参加会议的有全国20多个单位,会议对成都地质学院和重庆地质仪器厂试制的工艺样机DDS—1型地面甚低频电磁仪进行了评定,认为该样机达到及有些指标超过 相似文献
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Landslides are very common in high-altitude Himalayan terrains. Major roads in the Himalayas are frequently blocked due to
heavy landslides and remain closed for long periods of time. Permanent mitigatory solutions to these landslides are required
to keep the highways open. Lanta Khola, located 71.2 km north of Gangtok (capital of the Indian state of Sikkim), is one of
the oldest landslides on the North Sikkim Highway and is active since 1975. The rock types on either side of the landslide
are different (augen gneiss in the east and metapelitic schist in the west), and it is believed that the Main Central Thrust
passes through the slide zone. Since the slide is invariably activated in the aftermath of heavy rainfall, it is important
to identify the subsurface structures that channel water below the landslide surface in order to understand the triggers of
slide activity. This can only be accomplished by geophysical survey; however, an appropriate geophysical technique that can
be applied in such terrains must be identified. Very low-frequency (VLF) electromagnetic survey was performed over the Lanta
Khola landside in order to delineate subsurface structures. Although a very limited number of VLF transmitters are available
worldwide, it was possible to pick up VLF signals from a number of VLF stations even in this high-altitude mountainous terrain.
VLF measurements along five profiles perpendicular to the geological strike were recorded, and a high conducting zone was
delineated from the VLF observations. This conducting zone correlates with the low resistive zone identified from gradient
resistivity profiling. The anomalies confirm that there is a water-saturated zone (soggy zone) even in the subsurface of the
slide parallel to the geological gneiss–schist contact within the Lanta Khola slide. This indicates that the conductive feature
correlates with a weak water-saturated debris layer that lies along the slide and is parallel to the geological contact. Resistive
structures on either side of the landslide zone can thus be correlated with the stable ground. It is necessary to drain out
water from the soggy zone to minimize slide activity since this zone appears to penetrate into the body of the slide. 相似文献
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内蒙古老国营子金铜矿床是近年来利用地质与地球物理相互结合手段新发现的一个矿床。本次研究利用基于电磁原理的地球物理手段进行了找矿测试,结果表明:甚低频(VLF)地球物理扫面发现了近EW向和NW向的高阻带,分别对应了两条相应的矿化蚀变带。音频大地电磁法(EH4)测深影像显示矿化蚀变带表现为高阻异常带,与VLF的测量结果相一致。激电(IP)中梯测量显示矿化蚀变带具有高阻、高充电率和高金属因子异常特征。结合具体的地质特征,在老国营子金铜矿区综合运用这三种地球物理方法,取得了较好的找矿效果。 相似文献
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During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at
the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate
magnetic storm activity (Σ K
P
− = 32, K
P
index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra
of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain.
In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions.
In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler
mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine
parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions. 相似文献
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疏勒河断裂带中段为一隐伏基底断裂。由于规模较大,并且充填了低阻的构造角砾岩,因此对VLF有很好的响应。本文分析了该构造的VLF响应特点,指出在本区用VLF方法寻找隐伏构造的有效性和局限性。 相似文献
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Mohamed Khalil Akpofure Orubu Brad Rutherford Marvin Speece Fernando Santos Mohammad Farzamian 《Arabian Journal of Geosciences》2018,11(23):764
Geoelectrical methods involving electrical resistivity tomography (ERT), self-potential (SP), frequency domain electromagnetic (FDEM), and very low frequency (VLF) methods have been used to provide valuable information in locating a known sulfide ore body in Soap Gulch, Montana. The study develops basis of comparison for the geophysical techniques employed. Ranges of resistivity along the area have been established using interpreted ERT which can help to understand the subsurface distribution of sulfides in the area. A sulfide body was delineated from the survey area corresponding to anomalously low resistivity values on the ERT section, negative SP, and high apparent current density zone in VLF. Depth to the localized ore zone ranges approximately from 10 to 20 m. FDEM data reflect the conductivity distribution of the shallow subsurface (less than 6 m deep); hence, the delineated sulfide zone had minimal contribution to FDEM measurements. The results of the study show that SP, VLF, and ERT methods provide significant information in localizing ore bodies. The survey revealed that the resistivity values obtained from ERT profile corroborate the FDEM, SP, and VLF from the area. 相似文献
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Localization of water bearing fractured zones in a hard rock area using integrated geophysical techniques in Andhra Pradesh,India 总被引:1,自引:0,他引:1
Knowledge of the existence of fracture zones, their extent, intensity and direction is very useful for assessing groundwater in hardrock regions and in this context geophysical methods are widely accepted as a powerful means of study. In the modern era of exploration, application of the Resistivity Imaging technique gives a new opportunity for groundwater study in hardrock regions. Exploration surveys were conducted at one of the important sites in Maheshwaram watershed, Andhra Pradesh, India with a multielectrode resistivity imaging system. To reduce the ambiguity of geophysical interpretation some complementary geophysical studies like ground Magnetic and VLF were also carried out.A number of 2D resistivity images were prepared in a grid pattern, which clearly show the weathered and fractured zones in different parts of the study area. With the help of all 2D profiles a quasi-3D image has been created, which indicates the orientation and extension of the fracture zone in a horizontal as well as vertical direction in the study area. Strong agreement exists among the anomalies identified using the ground magnetic, VLF and resistivity imaging methods. The litholog data available in the study area also helps to interpret geophysical results to find a potential groundwater bearing zone in that area. 相似文献
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On the use of gravity and magnetic anomalies for locating probable areas of metallic mineralization in South Sinai, Egypt 总被引:1,自引:0,他引:1
The present study deals with processing and interpreting the potential gravity and magnetic data in order to locate promising
sites for metallic mineral occurrences in the basement rocks of South Sinai. Two promising sites were anticipated by combining
the geophysical results and the available geological information. Each site was profiled and interpreted to the nearly approximated
subsurface feature model, and the geometrical parameters of the expected subsurface structures may form mineralized bodies
such as depth, thickness, width, dipping, density contrast, and magnetic susceptibility contrast could be delineated. Detailed
ground Very Low Frequency (VLF) and Vertical Magnetic Gradient (VMG) methods were carried out in the site A2, eight VLF and
VMG anomalies were determined, and their depths were calculated. 相似文献
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