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1.
铜陵矿集区中酸性岩体航次3D成像及对深部找矿方向的指示 总被引：5，自引：0，他引：5
铜陵矿集区中酸性侵入岩与成矿关系密切,区内几乎所有的内生金属矿均与侵入岩有关,岩体周边和深部是主要的找矿方向,发现和圈定隐伏及半隐伏岩体对本区新一轮深部找矿工作有着重要意义.本研究以铜陵矿集区1:5万航磁数据的3D反演成像为基础,结合物性参数和地质信息,选取适当的磁化率边界,对矿集区岩体的空间分布进行了识别和圈定,共确定了33个岩体,并对其3D空间形态进行了定量分析,大部分推测岩体与地表地质填图所得岩体吻合较好.依据"层位+岩体"的找矿模式,以航磁反演推测岩体为基础,结合其他成矿信息,确定了本区圈定深部找矿远景区的6条基本原则,圈定了6个深部找矿远景区,对铜陵矿集区深部找矿具有重要的指示意义. 相似文献
2.
Odleiv Olesen Mark A. Smethurst Trond H. Torsvik Torben Bidstrup 《Tectonophysics》2004,387(1-4):105-130
Gravity and magnetic anomalies have previously been interpreted to indicate strongly magnetic Permian or even Tertiary intrusive bodies beneath the Skagerrak waterway (such as the ‘Skagerrak volcano’) and beneath Silkeborg in Denmark. Our combined modelling of the magnetic and gravity anomalies over these rock bodies indicates that a steep upward magnetisation is required to explain the magnetic anomalies at the surface, reminiscent of the magnetic direction in the Sveconorwegian rocks of the Rogaland Igneous Province in southern Norway. The younger rocks of the Permian Oslo Rift region have intermediate and flat magnetisation that is inadequate to explain the observed magnetic field. The positive part of the Skagerrak aeromagnetic anomaly is continuous with the induced anomalies associated with the eastward extension of the Rogaland Igneous Province. This relation also suggests that rocks of the Rogaland Igneous Province and its offshore extension are responsible for the Skagerrak anomalies. Both the negative, remanence-dominated aeromagnetic anomaly and the positive gravity anomaly can be modelled using constraints from seismic reflection lines and available density data and rock-magnetic properties. A 7 km thick complex of ultramafic/mafic intrusions is located below a southward dipping 1–4 km thick section of Mesozoic sediments and 1–2 km of Palaeozoic sediments. The enormous body of dense, ultramafic/mafic rocks implied by the modelling could be the residue of the parental magma that produced the voluminous Rogaland anorthosites. The application of similar petrophysical properties in the forward modelling of the Silkeborg source body provides an improved explanation of the observed gravity and magnetic anomalies compared with earlier studies. The new model is constrained by magnetic depth estimates (from the Located Euler method) ranging between 6 and 8 km. Forward modelling shows that a model with a reverse magnetic body (anorthosite?) situated above a dense, mafic/ultramafic body may account for the Silkeborg anomalies. The anorthosites may have formed by differentiation of the underlying mafic intrusion, similar to the intrusive relations in the Rogaland Igneous Province. We conclude that there is strong evidence for a Sveconorwegian age for both the Skagerrak and the Silkeborg anomalous rock bodies. 相似文献
3.
Alkaline intrusions at the edges of the Paraná Basin are mostly grouped in provinces, but occur in a few cases as isolated bodies. All of these intrusions surround the edge of the basin and intrude into weak zones, such as belts and arches. In rare cases, the intrusions are covered by basin sediments, but they are mainly found in the exposed crystalline basement. In this study, we discuss the gravimetric and magnetic signatures of the alkaline intrusions in the Ponta Grossa Arch, Alto Paranaíba and Goiás provinces. The provinces ages range from 120 to 60 Ma, and are thus contemporary or subsequent to the Serra Geral magmatic event. The magnetic signature of the province intrusions indicates a strong residual magnetization, as observed on maps of the anomalies reduced to the pole, which were different from the anomalies resulting only from induced field. The residual magnetization was often verified by magnetic measurements in the laboratory. Some of the studied intrusions have reverse magnetization. Other intrusions shows two magnetization directions, normal and reverse, indicating the likely presence of carbonatite. With the exception of the intrusions containing carbonatite, anomalies reduced to the pole are characterized by highly concentrated magnetization and well-defined 3D geometry. Intrusions with carbonatite usually exhibit dual polarization. The gravimetric signature is a positive anomaly of great magnitude. When carbonatite is present, a negative anomaly within the positive anomaly is observed, where the negative anomaly is associated with carbonatite. The gravimetric anomalies are also highly localized, indicative of 3D bodies. Gravimetric and aeromagnetic maps of the provinces show a coincidence between the location of the mapped intrusions and the anomalies. These maps also show anomalies that have the same signature but are not related to the mapped outcrops. This result suggests that these anomalies are indicative of the presence of alkaline intrusions that are covered by sediments (from either the Paraná Basin or alluvial sources) or are not emergent from the basement. The analysis of these maps and the inversion of the anomalies allows inference of the subsurface geometry, and thus also calculation of the body volume and its emplacement mechanism, which are elements necessary for mineral deposit evaluation. The maps also allow the identification of pre-existing faults and those formed during the emplacement. We compare geophysical models developed for gravimetric and magnetic data for the intrusions of the Ponta Grossa Arch, Alto Paranaíba and Goiás provinces in order to identify physical similarities and differences in the alkaline intruded into lithospheric segments with different tectonic histories. 相似文献
4.
三维地质填图为我国启动的新一轮地质调查项目,为提高重磁资料在三维地质填图中的应用效果,笔者提出重磁资料2.5D/3D相互约束重磁反演技术方案:利用重磁资料2.5D剖面反演结果、3D物性反演结果作为彼此反演约束条件,并通过了理论模型试验。试验结果表明,该技术方案使反演结果中物性参数、空间位置更接近理论模型体。通过对本溪—临江地区思山岭铁矿磁异常及酸性岩体重力异常进行反演实践——估算磁异常铁矿资源量、研究酸性侵入岩深部展布形态的效果良好,可为大面积三维填图提供有效途径。 相似文献
5.
Chengping Wu Changchun Yu Weiping Wang Xunbiao Ma Zhengguo Fan Hongwei Zhu 《地球科学进展》2019,34(10):1099-1107
In order to understand the physical characteristics of rocks and ores in Qihe, western Shandong and serve to basic geology and mineral resources investigation, the magnetic and density properties were collected in the survey area and the surrounding area, and statistics and analysis were given on the physical properties in terms of different kinds of rocks and ores. The result is that magnetite has the maximum value of magnetic property, the values of magnetic properties of basic rocks are bigger than the intermediate-acidic intrusive rocks, and the values of magnetic properties of sedimentary rocks are the smallest. The density of the Cenozoic strata is obviously different from formations and intrusive rocks under the covered area. Their interfaces cause the obvious gravity anomalies. The density value of magnetite is the biggest, and the density value of iron pyrite is the second biggest. The density of the metamorphic rocks of the Archeozoic Taishan rock group can cause certain gravity anomaly. Taking advantage of the relationship between the physical characteristics and the geophysical field, this paper mapped the lithology synthesizing other data, determined the ranges of metamorphic rocks and intrusive rocks, and delimited the ranges of ferromagnetic geological bodies as the target prospecting areas. Based on the physical characteristics, the depth and thickness information about the magnetite ore was inferred by conducting gravity and magnetic joint inversion. The result was nearly the same as the result of the verification borehole. The work of the research has promoted the understanding of physical characteristics of rocks and ores in this area, and provided more reliable basis for geophysical inversion and interpretation, geological structure and mineral resources research. 相似文献
6.
《地学前缘(英文版)》2022,13(2):101321
The Shuangjianzishan deposit in Inner Mongolia is a typical Ag-Pb-Zn deposit of the southern Great Xing’an Range. Proven reserves of Ag, Pb, and Zn in this deposit have reached the scale of super-large deposits, with favorable metallogenic conditions, strong prospecting signs, and high metallogenic potential. This paper reports a study involving integrated geophysical methods, including controlled-source audio-frequency magnetotelluric, gravity, magnetic, and shallow-seismic-reflection methods, to determine the spatial distribution of ore-controlling structures and subsurface intrusive rock for a depth range of <2000 m in the Shuangjianzishan ore district. The objective of this study is to construct a metallogenic model of the ore district and provide a scientific basis for the exploration of similar deposits in the deep and surrounding regions. We used three-dimensional inversion for controlled-source audio-frequency magnetotelluric data based on the limited memory quasi-Newton algorithm, and three-dimensional physical-property inversion for the gravity and magnetic data to obtain information about the subsurface distribution of ore-controlling structures and intrusive rocks. Under seismic reflection results, regional geology, petrophysical properties, and borehole information, the geophysical investigation shows that the Dashizhai group, which contains the main ore-bearing strata in the ore district, is distributed within a depth range of <1239 m, and is thick in the Xinglongshan ore block and the eastern part of the Shuangjianzishan ore block. The mineralization is spatially associated with a fault system characterized by NE-, NW-, and N-trending faults. The magnetic and electrical models identify large, deep bodies of intrusive rock that are inferred to have been involved in mineralization, with local shallow emplacement of some intrusions. Combining the subsurface spatial distributions of ore-bearing strata, ore-controlling faults, and intrusive rock, we propose two different metallogenic models for the Shuangjianzishan ore district, which provide a scientific basis for further prospecting in the deep regions of the ore district and surrounding areas. 相似文献
7.
根据湖南怀化地区1∶20万区域重力资料和1∶5万航磁资料,研究了怀化地区深部断裂及岩浆岩特征,圈定了隐伏-半隐伏岩体和断裂构造,并根据地质矿产和物化探综合信息,分析了成矿区带与岩体和构造的关系,总结了成矿区带的区域重磁场特征,圈出5个成矿远景区,为怀化地区寻找深部矿和隐伏矿提供了重要信息。 相似文献
8.
基于GPU的任意三维复杂形体重磁异常快速计算 总被引：3，自引：0，他引：3
提出了基于图形处理单元的任意三维复杂形体的重磁异常快速正演计算方法。将地下半空间剖分为大小相等规则排列的一组长方体单元,任意三维复杂形体可以表示成很多不同体积和密度(磁性)的长方体的近似组合。用解析方法计算出所有这些长方体在计算点的重力(磁力)异常,并累加求和,就可以得到整个模型体在计算点引起的重(磁)异常值。为了提高近似程度,需将地下半空间剖分得很细,用传统的CPU串行程序计算相当耗时。GPU在处理能力和存储器带宽上相对CPU有明显优势,采用GPU并行算法,可大大提高计算速度。相关试验结果表明,用GPU实现的正演快速算法计算结果正确,效率明显提高,为重磁异常三维物性反演提供了基础。 相似文献
9.
2010年笔者完成了西藏朗县秀沟工区1∶5 000高精度重磁勘探,重力测量总精度达0.069 4 mGal。根据岩矿石物性特征建立了铬铁矿地球物理模型与找矿标志。局部重力高异常0.1～0.6 mGal、宽度几十米至一二百米,并且磁异常中等强度、反向磁化的重磁异常组合特征是识别铬铁矿的标志;局部重力高异常带与环状镶边的正磁异常带的组合特征是识别超基性岩带的标志。运用小波分析提取铬铁矿与超基性岩体局部重磁异常,倾斜角(tilt-angle)法识别岩体边界,Paker法密度填图及2.5D交互反演推断了蛇纹石化橄榄岩的范围及14个铬铁矿与矿化体的重磁远景异常,其中6个远景异常已经得到证实。指出在西藏进行铬铁矿勘探,不仅要求野外施工精度高,而且要求室内处理解释工作精细,应充分运用各种数据处理的新方法技术,才能够获得良好的地质效果。 相似文献
10.
This paper is devoted to the possibility of inverse remanent magnetization that is acquired in intrusive rocks due to a magnetic field that is produced by a sum of the normal core field and an anomalous effect induced by solidified rocks. A computer program has been created to simulate the process of solidification of intrusive body rocks from its edges to the center. The computing results showed the possibility of remanent magnetization that is acquired, which can have a different direction as compared to the external magnetic field, up to the inverse one. 相似文献
11.
The Rapid Inversion of 3-D Potential Field and Program Design 总被引：1，自引：0，他引：1
The application of three-dimensional inversion of gravity and magnetic fields is very important not only in geophysical researches, but also in the study of geological structures. A formula of potential field in frequency-domain, developed by Parker in 1973, can be used as a rapid and effective algorithm in gravity and magnetic inversion. The technique has been improved then by Oldenburg, Sprenke, Feng and others.In addition to a brief introduction of Parker's algorithm and its applications, this paper includes the following five parts: basic computational techniques, inversion of single layer, convergence and constraints, simultaneous inversion for density and topography as well as inversion of multilayers. The authors present relevant practical iterative formulas and its varieties when density distribution varies with depth in linear or exponential relation. In order to maintain computation stability and speed up iteration convergence, some approaches are taken in the program design, for instance shifting lower interface of the studied layer, inverting corrections of topography, reducing grid boundary effects and utilizing low-pass filter. With the consideration of the nonuniqueness of the inversion, a method of using seismic data to constrain the range ofpossible models is discussed. It is pointed out that the density variation generates less effects than those of topography on the spectrum of gravity anomaly in second order. Therefore density contrast and topography can be inverted simultaneously by an alternative weighting iteration. By analogy, the inversion of multilayer model can be done in the above procedure. An approach of model decomposition is useful in the computation of multilayer model. The techniques discussed in the present paper for gravitational field are also valid for magnetic field. 相似文献
12.
Evolution of the magmatic plumbing system at Mt Etna: new evidence from gravity and magnetic data 总被引：1，自引：0，他引：1
New gravity and aeromagnetic data from Mt Etna volcano are presented which provide evidence for and constraints on relatively dense, high magnetization bodies at shallow levels below the summit craters. These are modelled and interpreted in terms of dyke/sill complexes, which may be the sites of short-term magma storage. A similar but larger body with high density and high magnetization is modelled below the southern wall of the Valle de Bove and may be the remnant of a prehistoric storage system. This body is close to the Valle del Bove, a major collapse feature, and may have influenced its geometry by buttressing and/or focusing zones of weakness. 相似文献
13.
位场自动反演技术的研究现状及意义 总被引：4，自引：0，他引：4
本文首先叙述了重、磁异常自动反演技术的特点。与传统的定性分析重、磁场分布特征的方法不同,重、磁异常自动反演方法通过反演得到地下场源分布,即地下密度或磁性的分布特征。由于密度体或磁性体与地质体的关系更为直接,因此这种新一代重、磁解释成果及图件将成为人们从新的角度来认识地质构造的基础材料。文中不但阐述了该方法的研究现状,同时也说明了存在的问题。 相似文献
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15.
长江中下游成矿带是我国重要的铁铜多金属矿产资源基地,燕山期中酸性岩浆岩对铜、铁、金等各种内生金属矿床的形成起着举足轻重的作用,识别和厘定岩浆岩体特别是隐伏岩体的三维分布形态对成矿动力学研究和深部找矿预测工作都有着重要意义。我们采用重磁三维物性反演技术,获得长江中下游成矿带磁化率和密度差三维模型,根据物性与岩性对应关系,识别和分析了区内岩浆岩体三维空间结构。推测了区内存在5个主要的岩浆活动中心,探讨了岩浆流动形式与轨迹。根据重磁三维反演反映的长江中下游岩浆岩三维分布特征,结合区域莫霍面、均衡重力异常和重磁多尺度边缘检测结果,以及区域成矿背景,预测了5个找矿远景区。结果表明,重磁三维反演技术是一种行之有效的岩浆岩体识别手段,通过对反演所得磁化率、密度分布情况的分析,可识别、圈定隐伏或半隐伏岩体,并可定量获取岩体三维形态特征,从而为寻找与火山岩、侵入岩体有关的金属矿产提供指示信息。 相似文献
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基于重磁反演的三维岩性填图试验——以安徽庐枞矿集区为例 总被引：8，自引：4，他引：4
开展大型矿集区深部精细结构探测研究,通过岩性识别与填图实现矿集区5km以内"透明化",发现深部矿产、揭示成矿规律是实现资源可持续发展的主要途径。鉴于重力和磁力数据覆盖面积广、采样密度高,重磁三维反演算法比较成熟,采用重磁反演进行岩性填图是现阶段实现三维岩性填图最有可能的途径。本文以安徽庐枞矿集区为例,提出了基于重力、磁力三维反演的岩性填图流程并开展了填图试验。在分析岩性和密度、磁化率关系的基础上,采用高精度的重力和航磁数据,进行先验信息约束的重磁三维反演,对反演所得的密度体和磁化率体进行逻辑拓扑运算,获得了庐枞矿集区地下5km以内五类主要岩性的三维分布。岩性填图结果显示的浅部特征与地表地质填图结果基本吻合,更重要的是反映了深部岩性的变化,弥补了地表地质填图的不足。庐枞矿集区岩性填图试验结果表明,开展基于重磁三维反演的岩性填图,是了解矿集区深部岩性特征,发现深部矿产的有效方法。 相似文献
18.
上接211页13 n个无限薄板叠加场反演13.1 复场展开以Mj代替2Mmj和2fMgj,以F(S)代替G′(S)和T(S),得复场F(S)= nj=1Mjσj-S=- nj=1MjS-σj。(13.1)展开上式,即F(S)=-1(S-σ1)(S-σ2)…(S-σn)×{M1(S-σ2)(S-σ3)…(S-σn)+M2(S-σ1)(S-σ3)…(S-σn)+…+Mn(S-σ1)(S-σ2)…(S-σn-1)}。(13.2)根据(9.2)、(9.9)式有(S-σ1)(S-σ2)…(S-σn)=-1F(S){Φ1+Φ2+…+Φn};Φ1=M1{Sn-1-x1(1)Sn-2+x2(1)Sn-3- …+(-1)n-1x(n-1)(1)},Φ2=M2{Sn-1-x1(2)Sn-2+x2(2)Sn-3- …+(-1)n-1x(n-1)(2)},Φn=Mn{Sn-1-x1(n)S… 相似文献
19.
重力场数据处理涉及的内容一般有场的延拓、方向导数以及局部场、背景场分离提取等,它们均属于重力异常分离问题的范畴。而重力场视密度三维反演技术是根据重力异常求取和确定场源体视密度的三维分布,其视密度分布图与地层岩性、地质构造以及地下矿体直接关联。对姚家岭地区重力场视密度三维反演技术的应用结果表明,视密度分布图对区内不同岩性地层的分布、褶皱和坳陷构造的分布特征等地质现象取得了良好的应用效果。 相似文献
20.
Snežana Ignjatović Ivana Vasiljević Milenko Burazer Miodrag Banješević Ivan Strmbanović Vladica Cvetković 《Swiss Journal of Geoscience》2014,107(1):101-112
The study reports new aeromagnetic and gravity data for the northern part of the Timok Magmatic Complex (TMC), East Serbia. The TMC is part of the Tethyan Eurasian metallogenic zone well known for hosting large copper and gold deposits. The complex formed by continuous volcanic activity 90–78 Ma ago, that developed in roughly three phases: Turonian andesites, Santonian–Campanian andesites/basaltic andesites (both mostly volcanic) and Campanian latites/monzonites (mostly shallow intrusive). The aeromagnetic measurements included acquiring total magnetic intensity data that were corrected for diurnal variations, leveling, microleveling, calculated normal field values, calculated anomaly values of total magnetic field intensity and reduction to the pole. The gravity measurements were carried out in an irregular grid with relative gravity values obtained using a Worden gravity meter. 2D modeling reveals that the subsurface extension of the Campanian Valja Str? pluton is ten times larger than it is indicated by its surface outcrops. This implies that the area south and southeast from the pluton can be interesting in terms of finding new porphyry systems. The model indicates that this intrusive body should not be considered as a deeply dissected pluton. This sheds new light onto its potential with respect to epithermal gold mineralization, as well. The model also suggests that there are larger non-exposed bodies of Santonian–Campanian volcanics and near-surface hydrothermally altered rocks than it is inferred from geological maps. The results of our study suggest that further interdisciplinary investigations in the TMC, in particular those integrating geophysics and geology, may have potential of advancing the existing exploration models. 相似文献