重磁异常对应分析在相山地区的应用

从泊松定理出发,计算重磁异常的相关性,并根据相关性的分布特征来分离和鉴别不同类型的异常区,为划分地质构造单元及认识地壳结构的其他特征提供信息,在对相山地区重磁异常对应分析中,用对应异常分析方法联合解释重磁异常,对该区地壳结构提出了一些认识。     

青藏高原亚东—格尔木地学断面重磁异常的对应分析

对应分析方法是一种重磁异常的定量化联合解释方法。从泊松定理出发,计算重磁异常的相关性,并根据相关性的分布特征来分离和鉴别不同类型的异常区,为划分地质构造单元及认识地壳结构的其它特征提供信息。在对青藏高原亚东—格尔木地学断面的综合研究中,本文用对应分析方法联合解释重磁异常,对该区地壳结构提出了一些认识。     

重磁对应分析方法在东北地区实际资料处理中的应用

本文从泊松定理出发,设计三度体理论模型,运用重磁对应分析方法,研究理论模型的重磁异常相关系数R、斜率B和截距A。由其等值线图得出点、线距的疏密不影响分析窗口半径的选择,确定了分析窗口半径的选择范围在模型半径的1.5倍左右以及截距的变化是剩磁反映的结论。进而从东北地区实际资料的重磁对应分析方法处理中推断出:该区强磁性岩石的剩磁较强,且由重磁异常的斜率B和截距A确定了强磁与剩磁的分布范围。     

磁源重力技术及其应用

磁异常的复杂性对资料处理和解释带来了一定的困难,而重力异常相对更为简单、更易处理和解释。通过运用空间域的泊松公式,可以在频率域内推导出由磁异常换算重力异常的计算公式,这种由磁异常换算所得到的重力异常称为磁源重力异常。这里对理论模型的磁异常数据进行了计算与实验分析,并对实际航测的磁异常资料进行了计算与处理,取得了良好的应用效果,表明了磁源重力技术的可行性、正确性和精确性。     

均质多面体重磁异常正演计算表达式的一致性

根据重力位、重力异常、磁位和磁异常公式,应用泊松关系,通过严格的公式推导,给出了重力位、重力异常、磁位和磁异常之间的数学关系,从而使重磁异常正演计算表达式包含于简单的规则之中,揭示出均质多面体重磁异常正演理论的一致性。     

井中磁位异常的计算与解释

在泊松公式的基础上推演了某些规则形体井中磁位异常的正演式及其相应的一些反演方法;进而提出了用B样条函数换算磁位异常。它具有统一、灵活、简便的优点。算例和实例表明B样条换算磁位异常用于磁测解释的可行性。     

北美区域重磁相关异常

重磁异常结合其他地质、地球物理资料进行相关分析,有利于提高位场异常地质解释的质量。利用等效点源反演绘制的图件,来研究北美及相邻海域的地面自由空间重力异常、POGO(线轨道地球物理观测)卫星磁异常,以及区域热流和构造信息间的视一空间相关关系。在卫星高度上相关异常的区域位场,也用泊松理论在重、磁场导数异常之间,移动窗口线性回归作定量分析。在大陆地区观测到长波长重磁异常之间的一种反相关关系。重力异常为负、磁力异常为正的地区,其特点是地壳相对较厚,磁化强度较高。例如:一个突出的磁力高与爱那达科盆地向辛辛那堤穹窿延伸的重力低相对应。磁力异常为负、重力异常为正的地区,其特征是地壳较薄,区域热流值较高。如:北美和中美洲的科迪勒拉地区,以及黄石地热区。虽然,海洋区域的重磁异常显示弱相关,但统计相关的符号一般为正。     

自适应重磁对应分析

采用传统重磁对应分析数据处理方法,计算了单体模型和三体模型条件下重磁异常的相关系数。结果显示:重磁异常中心区域的相关系数绝对值在重磁异常重合时为1,否则小于1(能指示重磁异常是否相关);在远离异常源或无重磁异常地区的相关系数绝对值不论重磁异常是否重合都趋于1(没有实际意义)。鉴于此,笔者提出了自适应重磁对应分析方法,并在晋冀北缘-辽西铁矿成矿带进行了2种方法的对比应用试验。结果表明:在滦南、司家营南部、马城等重磁异常完全重合的地区,2种数据处理方法的处理结果都表明为重磁正相关地区;在新集以东、小马庄西南部、石门东北部等重磁异常不完全重合或根本没有重磁局部异常的地区,传统重磁对应分析数据处理方法的处理结果也显示为正相关地区,自适应重磁对应分析数据处理方法的处理结果没有相关数据点或异常。     

磁法勘探在尼勒克县松湖铁矿中的应用

对尼勒克县松湖铁矿进行的地面磁法测量工作,获取了直接的磁异常数据。通过化极处理和不同高度的延拓分析,圈定了4个磁异常体,并通过用二度半重、磁异常人机联作实时二维剖面反演,拟合出矿体的形态特征,分析了其对应异常体的相对深度,为矿床勘探提供了较为明确的地球物理依据。     

灌注桩中钢筋笼磁异常特征研究

灌注桩中钢筋笼由主筋、加劲筋和箍筋组成。钢筋笼长度随桩长变化,单根钢筋的长度是一定的,为了满足长桩的需要,钢筋笼常常由一节或多节焊接而成。灌注桩中的钢筋笼是一磁性体,在地磁场磁化作用下,在其周围空间分布有磁异常。钢筋笼是一个规则磁性体,本文由重磁位场的泊松公式出发,推导出钢筋笼磁异常表达式,研究了灌注桩中钢筋笼磁异常分布特征。     

On the quantitative interpretation of magnetic anomalies by pseudo-gravimetric integration.

Poisson's theorem relates linearly the derivative of the gravity potential (taken along the total magnetization vector direction) and the magnetic potential due to a common, isolated source with constant density and magnetization distributions.
From that theorem, two very useful functional transformations for magnetic anomalies were formulated by Baranov, that is the 'pseudo-gravimetric integration' and the 'reduction to the pole'.
In this paper, it is shown that the first transformation is, in some sense, more useful than the reduction to the pole and, further, that its utilization presents noticeable advantages as regards the interpretation of magnetic anomalies. In fact, the pseudo-gravimetric integration, in contrast to the reduction to the pole, also provides a smoothing of the anomaly map and, in particular, reduces the degree of non-linearity existing in the mathematical relationship between the data and the source depth.
In order to show this last property of the transformation, spectral expansion inversions by 2_1/2D structures were performed on both magnetic and pseudo-gravimetric synthetic anomalies and the respective speed and precision were compared. The tests clearly indicate that very accurate estimates of the geometric parameters of the known source can be more easily and rapidly calculated by the transformed anomalies. Furthermore, due to its smoothing property, the method seems particularly useful when data are noisy. Tests on real anomalies confirm these results.     

Geological interpretation of Bouguer gravity and aeromagnetic data from the Gobi-desert covered area,Eastern Tianshan,China: Implications for porphyry Cu-Mo polymetallic deposits exploration

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.     

Characteristics of the Density and Magnetic Susceptibility of Rocks in Northern Borneo and their Constraints on the Lithologic Identification of the Mesozoic Rocks in the Southern South China Sea

Based on the volume magnetic susceptibility and specific gravity measurements and mineral and lithologic identification results for 540 samples,the rock type,density,and magnetic susceptibility of rocks from northern Borneo were analyzed,and the applicability of gravity and magnetic data to the lithologic identification of the Mesozoic strata in the southern South China Sea was assessed accordingly.The results show that there are 3 types and 25 subtypes of rocks in northern Borneo,mainly intermediate-mafic igneous rocks and exogenous clastic sedimentary rocks,with small amounts of endogenous sedimentary rocks,felsic igneous rocks,and metamorphic rocks.The rocks that are very strongly-strongly magnetic and have high-medium densities are mostly igneous rocks,tuffaceous sandstones,and their metamorphic equivalents.The rocks that are weakly magnetic-non-magnetic and have medium-very low densities are mostly conglomerates,sandstones,siltstones,mudstones,and coal.The rocks that are weakly magnetic-diamagnetic and have highmedium densities are mostly limestones and siliceous rocks.The Cenozoic rocks are characterized by low densities and medium susceptibilities;the Mesozoic rocks are characterized by medium densities and medium-high susceptibilities;and the pre-Mesozoic rocks are characterized by high densities and low magnetism.Based on these results and the distribution characteristics of the various rock types,it was found that the pre-Mesozoic rocks produce weak regional gravity anomalies;the Mesozoic sedimentary rocks produce negative regional gravity anomalies;whereas the Mesozoic igneous rocks produce positive regional gravity anomalies;and the Cenozoic igneous rocks produce positive regional gravity anomalies.The regional high magnetic anomalies in the southern part of the South China Sea originate from the Mesozoic mafic igneous rocks and their metamorphic equivalents;and the regional medium magnetic anomalies may be produced by the felsic igneous rocks and their metamorphic equivalents.Accordingly,the identification of the Mesozoic lithology in the southern South China Sea shows that the Mesozoic sedimentary rocks are distributed over a large area of the southern South China Sea.Thus,it is concluded that the Mesozoic strata in this area have the potential for oil and gas exploration.     

划分重磁区域异常与局部异常的一种方法泛克立格法

在重（磁）资料的分析处理中,经常需要划分区域异常与局部异常。本文对用于矿床品位预测的方法—泛克立格法加以改进、完善,使其适合于求重（磁）资料的区域异常与局部异常。根据某点周围若干个信息点上的重（磁）观测数据估计出该点处的区域异常值,而且这种估计是在满足线性、无偏、最小估计方差条件下求得的。从重（磁）观测数据中减去区域异常就可得到局部异常,这就是泛克立格法。它比经常用来划分区域异常与局部异常的方法—趋势分析方法有许多优点。趋势分析方法只是泛克立格法的一个特例。在本文中,作者还提出在小范围内,重力区域异常适合于用一次多项式拟合;而磁法区域异常适合于用二次多项式拟合的观点     

秦岭造山带中段重磁异常与成矿带的关系

成矿带的展布受地质构造的控制,而地质构造在重磁异常上有明显反映。为了研究秦岭造山带中段重磁异常与成矿 带的关系,该文系统整理、处理了秦岭造山带中段已获得的重磁力测量资料,分析研究了重磁异常的展布特征、推断了研 究区的断裂构造,讨论了结晶基底的起伏特征,并结合区域地质资料及矿床分布资料讨论了重磁场特征及其与地质构造、 成矿带的关系。结果表明,秦岭造山带中段成矿带均分布在重、磁异常梯度带上或几组不同方向异常的交汇部位,尤其在 局部重力高异常范围内及其边部梯度带上矿体富集。这一结果为研究秦岭造山带的地质演化、地质构造（尤其是深部构 造）、断裂分布及下一步的成矿有利区预测提供重要的参考信息。     

重磁三维可视化反演系统的设计与实现

重磁三维可视化反演解释系统一直是国内外重磁勘探领域的研究重点之一。介绍了基于Visual C++与OpenGL环境研发的重磁三维可视化反演系统,详细阐述了系统的设计思想与实现的关键技术,包括可视化技术、面向对象技术、图形拾取技术、碰撞检测技术及反演约束技术等。系统具有人机交互几何反演与最优化物性自动反演两种功能,可满足目标异常、区域模拟和盆地建模。     

APPLICATION OF MAGNETOMETRIC DATA IN THE STUDY OF DEEP CRUSTAL STRUCTURE IN PLATFORM PROVINCES

Results of regional geophysical work in the U.S.S.R. allow a measure of correlation between the known structural features of the crust and those of the geomagnetic field. The “normal” magnetic field used for identifying magnetic anomalies is obtained by graphic smoothing of isolines of total intensity T. Detailed analysis of data obtained in aeromagnetic and gravity surveys throughout the U. S. S. R. leads to the conclusion that the cause of the observed regional magnetic and gravity anomalies lies in the same associated geologic objects located at the same level - that of a magnetoactive interval of the crystalline envelope of the earth. The conclusions that can be drawn from existing data are: 1) the existence of “continental” anomalies of the geomagnetic field cannot be explained as an effect of the crust; 2) the basaltic layer does not affect the distribution of the geomagnetic field; 3) the anomalies in the basic (normal) geomagnetic field are caused by the presence of thermomagnetic geologic bodies in the granitic layer; accordingly, it is theoretically possible to determine the thickness of the continental layer from magnetometric data. A table showing correlative depths of the basaltic layer, its thickness, and anomalous magnetic field, as well as magnetic profiles is included.--C. E. Sears.     

庐枞火山岩盆地及其外围重、磁场特征

为探测长江中下游成矿带庐江-枞阳白垩纪火山岩盆地的深部构造和地壳结构,2007年初在庐枞火山岩盆地进行了以深反射地震剖面探测为主的,新一轮重力、磁力和大地电磁剖面测量。作者在前人研究的基础上对庐枞火山岩盆地及其外围重、磁场特征进行了研究。作者首先分析长江中下游地区重、磁场的分布特征,然后以区域重、磁场特征为背景来认识庐枞地区重、磁场的分布特征。研究各类地质体的物性参数是开展地球物理解释的前提,文中收集并分析了前人对庐枞地区的岩石物性的较为系统研究成果。为了提取重、磁异常的特征,文中对重、磁异常进行了位场转换和图像处理。利用新的深反射地震剖面探测和大地电磁剖面研究成果,采用定性和定量解释方法对庐枞地区重、磁场的分布特征进行了研究并提出新的认识。庐枞火山岩盆地深部存在隐伏的磁性强的中碱性岩类是产生区域磁异常的主要原因。庐枞火山岩盆地下部火成岩所侵入的地层向盆地东南方向延伸,盆地的西北边界向东南方向倾斜。而在罗河断裂带以西没有火成岩存在。亦即庐枞火山岩盆地是一个沿北东向罗河断裂向东发育的非对称火山盆地。另外,在庐枞火山岩盆地西部边缘罗河深部存在切穿莫霍面的断裂带沿北东向延展数十千米。