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1.
S K Pal Jitendra Vaish Sahadev Kumar Piyush Priyam Abhay Kumar Bharti Rajwardhan Kumar 《Journal of Earth System Science》2017,126(4):53
The present study deals with the characterization of subsurface coal fires of East Basuria colliery in Jharia coal field, India using tilt derivative and downward continuation of magnetic data. Magnetic data processing methods such as diurnal correction, noise removal, reduction to pole, tilt derivative and downward continuation have been used to process the data and for the interpretation of results on the basis of magnetic properties of overlying materials which change with the temperature variation above or below the Curie temperature. Most of the magnetic anomalies are associated with coal fire and non-coal fire regions which are correlated with tilt-derivative anomaly and corresponding downward-continued anomaly at different depths. The subsequent surface and subsurface characteristics are explained with good agreement. Approximate source depth of principal anomaly inferred from tilt derivatives method are corroborated with multi-seam occurrences, mine working levels and surface manifestation which are also correlated well with 3D model of downward continued anomaly distribution. 相似文献
2.
The Basque country magnetic anomaly follows a NW–SE trend over the Basque country (northern Spain) with intensities up to
250 nT measured at 3000 m above sea level. The paired negative part of the anomaly is located to the north and presents intensities
down to –60 nT. A model of the magnetic properties of the crust in the area, taking into account previous geological and geophysical
data, indicates a wedge of material with a magnetic susceptibility of 0.07 SI emplaced along a NE-directed basal thrust. The
anomalous wedge is composed of basic and/or ultrabasic Cretaceous intrusives and lower crustal rocks, and reaches a minimum
depth which increases towards the northwest from 5–7 to 12 km. According to previous works, geological features of the rocks
on top of the anomalous wedge indicate that during the Cretaceous this zone constituted a deep marine environment which underwent
important crustal thinning related to rifting. The transition towards the southwest was to a normal continental platform.
Alpine deformation gave rise to displacement on a basal thrust, which can be correlated with the lower contact of the magnetic
wedge, and emplacement of this wedge towards the northeast. The southeastern termination of the anomaly can be related to
the lateral termination of the basic rocks which constitute the anomalous wedge in a transform fault related to the rifting
event.
Received: 30 January 1995 / Accepted: 9 February 1996 相似文献
3.
近年来,甘肃西成铅锌矿的勘探向周边地区扩展,高精度磁法测量发挥了一定作用。利用化极磁异常垂向一阶导数和归一化总水平导数垂向导数,推断出5处地质体边界和4条断裂。根据该区地质和矿产分布特征,推测矿体主要分布于黑云母石英片岩向大理岩的接触或过渡地带,对应中泥盆统安家岔组厂坝层D2a1条带状大理岩。根据化极磁异常和该区构造,结合化探圈定出与成矿有关的4个靶区,这些靶区与Pb、Zn化探异常对应,可见若干矿化点。选取靶区内一磁测剖面进行反演,反演结果说明矿体向北西倾斜。经钻孔验证,已在不同深度见矿,证明了靶区的找矿潜力。 相似文献
4.
In this study, Bouguer gravity and aeromagnetic data have been used to better understand the geology and mineral resources near the late Carboniferous-late Permian porphyry Cu-Mo polymetallic mineralization in the Chinese Eastern Tianshan belt, which is extensively covered by Gobi-desert. The reduced-to-pole (RTP) transformation of regional-scale aeromagnetic data shows that the porphyry Cu-Mo deposit is within a cluster of magnetic anomaly highs that overprint on a northeast trending magnetic gradient belt generally along the crustal-scale Kanguertag-Huangshan fault. The 10 km upward continuation transformation of both Bouguer gravity and aeromagnetic data indicates that the known porphyry Cu-Mo polymetallic deposits are located on the flanks of prominent gravity and magnetic anomaly highs. These anomalies are spatially correlated with the late Carboniferous-late Permian igneous rocks and in the Tuwu-Yandong mineralization district are centered over the granodiorite rocks genetically related to porphyry copper systems. In order to minimize interpretational ambiguities, a useful approach that is correlation analysis (CA) based on correlation coefficient (CC) given by gravity and magnetic data was employed to separate positively and negatively correlated anomalies features. The CA procedure is applied to 10 km upward continuation transformation of both Bouguer gravity and RTP transformed aeromagnetic data for mapping correlative magnetization and density contrast anomalies from deep sources, which may be associated with the porphyry Cu-Mo polymetallic mineralization. Five prominent CC positive anomalies have been found in the southern margin of Dananhu-Tousuquan arc. Those anomalies zones could be interpreted to reflect a late Carboniferous-late Permian magmatic belt that is favorable for additional discoveries of late Carboniferous to late Permian porphyry copper systems in north region of Eastern Tianshan. 相似文献
5.
Frank E. Senftle Arthur N. Thorpe Corrinne C. Alexander Charles L. Briggs 《Geochimica et cosmochimica acta》1973,37(4):1053-1062
Magnetic susceptibility measurements have been made on four glass spherules and fragments from the Luna 20 fines; two at 300°K and two from 300°K to 4°K. From these data the magnetic susceptibility extrapolated to infinite field, the magnetization at low fields and also the saturation magnetization at high fields, the Curie constant, the Weiss temperature, and the temperature-independent susceptibility were determined. Using a model previously proposed for the Apollo specimens, the Curie constant of the antiferromagnetic inclusions and a zero field splitting parameter were calculated for the same specimens. The data show the relatively low concentration of iron in all forms in these specimens. In addition, the Weiss temperature is lower than that measured for the Apollo specimens, and can be attributed almost entirely to the ligand field distortion about the Fe2+ ions in the glassy phase. The data further suggest that the Luna 20 specimens cooled more slowly than those of the Apollo missions, and that some of the antiferromagnetic inclusions in the glass may have crystallized from the glass during cooling. 相似文献
6.
新疆哈密东天山构造岩浆带位于尾亚-罗布庄磁力高带上的喀拉塔格磁场小区,该带发育幅值在200～300 nT的正磁场区,封闭磁异常对应于石炭纪石英闪长岩或隐伏基性侵入岩体.钳子山C07-2磁异常为该区带高磁异常,最高幅值2 340 nT.经钻探验证,打出3层低品位含铜钛磁铁矿,总厚119m.据81个化学样分析,TFe约3.6％～28.80％,平均品位13.5％,TiO2 1.31％～2.33％.ZK0701-10/5层(111～113 m)见有2m厚具工业品位的铜矿体和磁铁矿体,分析结果为Cu 0.4％,TFe 28.8％.该钻探成果为在哈密玉西地区寻找岩浆型钛磁铁矿提供了有力依据. 相似文献
7.
《Gondwana Research》2001,4(3):443-454
A systematic regional magnetic survey was carried out in the districts of Vizianagaram, Visakhapatnam and Srikakulam in Andhra pradesh, India comprising an area of 15, 000 sq. km of eastern migmatite zone of Eastern Ghat Mobile Belt. The magnetic anomalies are very noisy, varying between −1300 nT and +700 nT in amplitude and correlate very poorly with the surface geology. Upward continuation of these anomalies brought out distinct magnetic anomaly trends, running along NE-SW on the south and turning later to E-W on the north, consistent with the folding pattern of Eastern Ghats. Based on the termination of anomaly closures and displacement of anomaly trends, five faults, all striking approximately in the N-S direction, were inferred. From inversion of anomaly profiles, it is established that the anomalies are produced by structures in the magnetic basement composed of charnockites. 相似文献
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Piston cores 7 m and 6.5 m long were collected from Lakes Zug and Zurich respectively. Radiocarbon age determinations, pollen assemblage zones and varve counts indicate dates of 5000–6000 years B.P. (Zug), and 12,000–13,000 years B.P. (Zurich) for the base of the cores. Declination of the magnetic remanence varies through 70° and inclination varies through 30°. Although the correlation with the geomagnetic secular variation curve covering the last 15,000 years as determined from Lake Windermere, England (Creer et al., 1972) is not precise, the results suggest that Lake Zug and Lake Zurich sediments have been recording the broad outline of past secular variations of the earth's magnetic field. Since intensity of magnetization and susceptibility correlate markedly with lithology, a detailed sediment stratigraphy is presented. The amount and texture of the detrital input appears to be a controlling factor for the natural magnetic remanence. Intensity varies from 90 μG in zones of organic, sulphide pigmentation and those with ultra-fine laminations to 0.8 μG in impure lacustrine chalk. Susceptibility ranges from 9 μG/Oe in laminated, fine-grained glacially derived muds to 0.5 μG/Oe in impure lacustrine chalk. Intensity of magnetization also varies systematically within individual turbidites with lowest values in the coarse-grained, basal fractions. Slumped beds were identified on the basis of erratic anomalies in magnetic declination and inclination measurements. 相似文献
10.
航磁异常的构造解释和华北-塔南-扬子超陆块演化 总被引：11，自引：0，他引：11
在现代地球磁场中,总体感磁效应与岩石的磁化率无关。典型地区大比例尺构造组构填图结果与岩石磁组构的对照分析,证明磁线理和构造线理具有一致的矢量特征。强烈韧性剪切导致岩石中区域一致的矿物定向和磁化率各向异性,是干扰现代地球磁场、产生特定航磁异常分布格局的主要因素。对五种基本的区域尺度构造 航磁异常样式的成因进行了分析,证明华北地区的航磁异常的分布样式与结晶基底的基本构造格架基本一致。并据此对塔里木、扬子地体基底岩石的构造性质进行了解释,提出存在前寒武纪华北－ 塔南－ 扬子超陆块。结合显生宙构造演化的地质证据,划分出新太古代克拉通化、古元古代左行韧性剪切改造和活动带发育、中－ 新元古代裂解和活动大陆边缘、古生代原地改造和中生代再裂解五个演化历史阶段 相似文献
11.
介绍了利用区域磁测资料计算居里等温面的几种常用方法。对影响居里等温面的几个重要因素,诸如区域异常的选择、滑动窗口的尺度选择等进行了理论分析。根据影响岩石居里点温度的各种因素,提出评估居里等温面计算精度的方法。给出居里等温面在区域负磁异常起因、油气资源预测、成矿作用与物性界面关系等方面的应用 相似文献
12.
QIANGTANG MASSIF CRUST DEFORMATION FEATURES, DIFFERENCE AND ITS GENETIC MECHANISM STUDY 相似文献
13.
Alessandro Sandrin sa Edfelt Tod E. Waight Robert Berggren Sten-ke Elming 《Journal of Geochemical Exploration》2009,103(2-3):80-96
The Tjårrojåkka Fe–Cu-prospect in northern Sweden is considered an example of a Fe-oxide Cu–Au (IOCG) deposit and is hosted in metamorphosed Paleoproterozoic volcanic and intrusive rocks. Rock samples from 24 outcrops were collected for petrophysical analysis (magnetic susceptibility, remanent magnetization, variation of magnetic susceptibility with temperature, Curie temperature and density). The major Cu-prospect in the area has been studied by magnetic and electron microprobe analyses of four selected rock samples. The samples are from an exploration well that intersects the main Cu-mineralized body.The magnetic analyses show that magnetite is the dominant magnetic mineral, while hematite and other Fe-minerals are present in minor amounts. The electron microprobe observations confirm the presence of magnetite and further indicate that hematite is an alteration product of magnetite. Moreover, microprobe observations indicate that Fe-sulfides are present in negligible amounts in the samples from the Tjårrojåkka area. The strong spatial relationship of Cu-minerals (e.g., chalcopyrite) and the oxidation of magnetite to hematite suggest that the presence of rocks with low magnetic susceptibility in areas dominated by high susceptibility rocks may be a signal of related Cu-prospects. 相似文献
14.
The Loncopué Trough is a Pliocene to Quaternary extensional basin developed over the hinterland area of the Southern Central Andes. This basin is bounded by two neotectonic extensional fault systems delimiting a narrow topographic low. Previous studies have mostly focused on structural and geochemical aspects of this feature. However, geophysical surveys, aimed to unravel deep structure beneath a thick-younger than 5 My volcanic coverage, are scarce and based their interpretations on low resolution data sets. In this study, we collected new aeromagnetic data with the objective of characterizing the magnetic properties of the crust in the Loncopué Through and nearby zones. Additionally, we analyze the spatial relation between geological structures, volcanic fields and magnetic data. In order to highlight the boundaries of the magnetic sources and calculate the basement depth, we applied derivative techniques and the source parameter imaging. Also, we estimated an effective susceptibility model using the Magnetization Vector Inversion method, which takes into account the combined effects of remanence and induced magnetization. To determine the thermal structure of the area, we calculated the Curie depth points through the spectral analysis technique. From the analysis of magnetic data we were able to characterize the main structures and lineaments associated with this retroarc extensional trough. Notably, only the Loncopué eastern fault system seems to be a crustal-scale tectonic feature, while E-W-, ENE- and ESE-trending lineaments are interpreted as relatively minor structures segmenting the basement. Finally, our susceptibility model, together with the analysis of the Curie point, revealed potential magmatic/hydrothermal reservoirs in the Copahue volcano, and the Codihue and Cajón de Almanza regions that could be connected at depth forming a regional magmatic body. 相似文献
15.
The Curie point depth map of Eastern Iran was constituted from spectral analysis of the aeromagnetic data. The reduction to pole (RTP) was applied to the magnetic anomaly data. The Curie point depth values from 165 overlapping blocks, 100 × 100 km in size, have been estimated. The Curie point depth method provides a relationship between the 2-D FFT power spectrum of the magnetic anomalies and the depth of magnetic sources by transforming the spatial data into the frequency domain. The centroid and top depth of the magnetic sources (respectively Z0 and Zt) is calculated from radially averaged log power spectrum for each block. Finally, the Curie point depth of Eastern Iran is obtained by Zb = 2Z0–Zt. The highest value of 24 km is located in eastern and western boundaries of the Lut block, and the lowest value of 12 km is located at north of study area. The shallow depths in the Curie-point depth map are well correlated with the young volcanic areas and geothermal potential fields. Geothermal gradient ranging from 24 to 45°C/km. The deduced thermal structure in eastern Iran has a relationship with orogenic collapse associated with delamination of thickened lithospheric root between the Lut and Afghan continental blocks. 相似文献
16.
着重论述了丁家山铅锌（银）矿床的地质地球物理特征，磁法找矿的特殊作用，总结了建筑梅仙式矿床的物化探异常标导。 相似文献
17.
甘肃省西和县大坪测区、礼县马家沟测区、肃南县黑沟西测区应用高精度磁法测量划分弱磁性地层界线的效果良好,岩性磁化率差值在10～20×10-5SI以上,磁异常差值在10～20nT以上的弱磁性地层界线可以明显区分。在实际生产中对地质填图起到了指导作用。 相似文献
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20.
退磁作用对磁测资料解释的影响 总被引：1，自引：0，他引：1
退磁作用使磁异常幅值变小,形态畸变,影响磁测资料反演解释的地质结果的准确性。用有限元法数值模拟磁性体在考虑退磁作用下的磁场,以二度水平圆柱体理论模型为例,研究退磁作用对磁异常的影响。当磁化率κ≥1.0 SI时,考虑与不考虑退磁作用,异常极大值偏差可达1 300 nT以上,相对偏差可达30%以上,因此认为退磁作用的影响很大,不可忽略。青海尕林格铁矿区磁测资料的反演实例说明,忽略退磁作用将导致反演的矿体体积偏小,影响钻孔的布置和资源储量的评价。 相似文献