Invariants in toroidal and tangentially geostrophic frozen-flux velocity fields

We derive two new types of invariant that must be obeyed by the radial magnetic field at the core-mantle boundary if the hypothesis of frozen flux is valid and the fluid motion is either toroidal or tangentially geostrophic there. These general invariants incorporate specific invariants that are already known and can, in principle, be tested using magnetic data that cover an interval of time.     

Periodicity of magnetic intensities in magnetic anomaly profiles: the Cenozoic of the South Atlantic

Spectral analyses of several published magnetic anomaly profiles from Candé & Kent (1992a) were undertaken prior to analysing, in the same way, raw magnetic anomaly data from similar parts of the South Atlantic. It was found that similar and distinct medium and short wavelengths were present in both the published and raw data. When these are converted into the time domain using the average rate of spreading for each profile, these periodicities appear similar, possibly identical, to those expected from the long-term eccentricity orbital parameters (Fischer, DeBoer & Premoli Silva 1990). While such correlations are not necessarily causative, they suggest that magnetohydro-dynamical processes near the core-mantle boundary may be affected by gravitational changes due to planetary orbital perturbations.     

Three-dimensional Rayleigh hysteresis of oriented core samples from the German Continental Deep Drilling Program: susceptibility tensor, Rayleigh tensor, three-dimensional Rayleigh law

Rayleigh hysteresis, as defined by the well-known Rayleigh relations, has been observed not only when magnetization of pyrrhotite-bearing KTB-samples is measured in parallel to a weak dc magnetic field, but also in experiments where field and measuring directions have been adjusted strictly perpendicularly to each other. Nine-tupels of independent Rayleigh hysteresis loops could thus be compiled. Their characteristic coefficients X ^ijk of initial susceptibility together with the Rayleigh loss coefficients α^jk have been proved to determine completely the samples' weak-field magnetic anisotropy. Interpreting the coefficient matrices ( X ^ijk) and (α^jk) as the tensor of initial susceptibility and the Rayleigh tensor, respectively, generalization of the isotropic Rayleigh relations in terms of corresponding tensor relationships has been suggested for the anisotropic case. Application to the KTB samples showed 3-D Rayleigh hysteresis measurements to be an excellent tool for rock magnetic analysis in terms of ore content and crystalline texture. In particular, a magnetocrystalline double texture of the basal planes of pyrrhotite precipitates and their [1120] directions of easy magnetization have been clearly detected. Surprisingly, the welt-known theorem α= const. X ²_I, formulated by Néel (1942) for the isotropic case, has been found to hold true even in tensor generalization (α_jk) = const ( X ²_jk). To reach sufficient resolution for the measurements performed, a sensitive vibrating coil magnetometer (VCM) has been developed.     

覆盖层下三维异常体对垂直磁偶极源的电磁响应

针对地下半空间存在三维异常体及覆盖层情况，计算了垂直磁偶极子的场，计算结果表明σ１与σ２接近时，覆盖层影响减小；σ１增加时覆盖层影响增大；对于不同的σ２／σ１值，场幅值对高频（ｆ≥２ｋＨｚ）和低频（ｆ≤１０Ｈｚ）都明显减小，只有在２ｋＨｚ≥ｆ≥１０Ｈｚ之间，场幅值可达最大。还表明垂直磁偶极子的场具有较强的岩性识别和分层能力     

黑色岩系中铂族元素地质地球化学特征

含ＰＧＥ黑色岩系可根据黑色岩系中有无火成岩，将其分为：（１）与火山作用或岩浆活动无关的黑色岩系；（２）与火山作用或岩浆活动有关的黑色岩系不同地质背景下，富金属黑色岩系的特征及其ＰＧＥ的分布特征既有相似之处，又各具特点，反映出两者ＰＧＥ的地球化学演化过程有所差别。有关ＰＧＥ比值不仅可以反映出元素的地球化学行为，亦可区分或指示不同环境下ＰＧＥ地球化学演化的规律性。     

东海西湖凹陷保俶斜坡带圈闭类型及含油气性分析

保俶斜坡带位于西湖凹陷的西部,新生代沉积厚度可达1万m,始新统和渐新统是主要的含油气目的层段。现已发现的含油气圈闭类型不仅受构造因素控制,而且受沉积环境因素控制,预测还有与岩浆作用有关的圈闭类型。     

航空短波红外分光谱遥感技术直接寻找油气藏的有效性及应用实例

采用航空短波红外分光谱遥感技术，在新疆准噶尔盆地和塔里木盆地某些油气区，进行直接寻找油气资源的试验研究后发现，油气区含油岩系，油气藏上方盖层土壤的光谱在２３００和２３５０ｎｍ波段具有双吸收特征。     

山西阳高堡子湾金矿地质特征及找矿标志

堡子湾金矿位于华北地台北缘天镇断拱东部阳高凸起区，是与印支未－－海西期火山一次火岩有关的隐爆角砾岩型金矿床。成矿物质主要来自重熔型岩源－－石英二长（斑）岩，隐爆角砾岩为容矿岩石，与隐爆带总体走向平行的张扭性断裂为导矿构造，隐爆角砾岩的内部裂隙及角砾间隙，是良好的储矿构造。     

我国磁法勘探的研究与进展

简要概述了我国磁法勘探50年来的研究与进展，主要包括：地面、航空与海洋磁测工作，磁力仪研制与生产，磁异常处理与转换技术，磁异常解释理论与方法，岩石磁性研究，磁法勘探在基础地质研究、固体矿产勘查、油气勘查和其他领域中的应用．     

克服低纬度化磁极困难的有效方法

低纬度地区（尤其是磁赤道附近）磁场化极是长期以来没有很好解决的问题。这里提出的方法只时常规化极稍加改进，通过时化极因子的频点偏移，避开无界点，使化极结果改善很大，甚至在赤道上也可以化极。它既有很高的精度，又因仍是在频率域内进行，故计算方便、快速，非常适合大面积的资料计算