Imaging distribution patterns of magnetic minerals by a novel high-Tc-SQUID-based field distribution measuring system: application to Permian sediments

A newly developed field distribution measuring system based on a high- T _c SQUID has been employed in the study of magnetic mineral distribution in several Permian sedimentary rocks. The instrument consists of a small, 1.4×1.4 mm sized YBaCu-oxide SQUID magnetic field sensor that is operated in a thin-walled dewar, so that the sample's surface, at room temperature, can be scanned at a distance of only ∼1.5 mm. The samples were subjected to a saturation remanence perpendicular to the surface and the scanning measurements in zero field reveal that the magnetization might be carried by only a small part of a sample, in one case associated with secondary oxide phases. High-resolution magnetic scans can aid in the interpretation of the magnetic remanence acquisition process.     

陀螺马达转速稳定性对陀螺定向影响的探讨

本文探讨了陀螺马达转速稳定性对陀螺定向的影响规律。     

关于磁异常化到地磁极问题的几点认识

文中阐述了磁异常化到地磁极（简称化极）的物理意义,指出了化极和换算为垂直磁化条件下的垂直磁异常的差别。在做化极处理时,实测的磁异常要完整,否则将会引起化极结果的畸变。利用教科书中给出的公式对二度体磁异常做化极处理,对化极结果解释所得的磁化强度是磁性体的总磁化强度,一般情况下不是原始的ΔＴ（或Ｚａ）异常所对应的有效磁化强度。     

延矾盆地北缘断裂深浅构造关系研究

在已有的地表地质构造、浅层探测与深部探测等资料基础上，利用高精度地震局域网的数字地震记录，分析了延庆矾山次级盆地北缘断裂上的微、小地震活动特征, 及其与地表活断层和深部地壳结构关系. 通过对地震局域网获得的微、小地震的精确位置、震源机制解及其特点的分析，厘定了地表活断层延庆矾山盆地北缘断裂属旋转平面状正断层，揭示了延怀盆地区浅表地质与深部构造的相互关系，以及地壳脆韧性变形随深度的转换特征.      

A late diagenetic (syn-folding) magnetization carried by pyrrhotite: implications for paleomagnetic studies from magnetic iron sulphide-bearing sediments

Paleomagnetic, rock magnetic, and sedimentary micro-textural data from an early Miocene mudstone sequence exposed in Okhta River, Sakhalin, Russia, indicate the presence of pyrrhotite and magnetite at different stratigraphic levels. Sites that contain only magnetite have a reversed polarity characteristic remanent magnetization (ChRM) with a low-coercivity overprint, which coincides with the present-day geomagnetic field direction. Pyrrhotite-bearing sites have stable normal polarity ChRMs that are significantly different from the present-day field direction. After correction for bedding tilt, the ChRM data fail a reversals test. However, the normal polarity pyrrhotite ChRM directions become antipodal to the tilt-corrected magnetite ChRM directions and are consistent with the expected geocentric axial dipole field direction at the site latitude after 40% partial unfolding. These data suggest that the pyrrhotite magnetization was acquired during folding and after lock-in of the magnetite remanences. Electron microscope observations of polished sections indicate that fluid-associated halos surround iron sulphide nodules. Pyrrhotite is present in randomly oriented laths in and around the nodules, and the nodules do not appear to have been deformed by sediment compaction. This observation is consistent with a late diagenetic origin of pyrrhotite. Documentation of a late diagenetic magnetization in pyrrhotite-bearing sediments here, and in recent studies of greigite-bearing sediments, suggests that care should be taken to preclude a late origin of magnetic iron sulphides before using such sediments for geomagnetic studies where it is usually crucial to establish a syn-depositional magnetization.     

ABCAnalytical and Semi-Analytical Analysis of an Artificial Satellite’s Rotational Motion

The rotational motion of an artificial satellite is studied by considering torques produced by gravity gradient and direct solar radiation pressure. A satellite of circular cylinder shape is considered here, and Andoyers variables are used to describe the rotational motion. Expressions for direct solar radiation torque are derived. When the earths shadow is not considered, an analytical solution is obtained using Lagranges method of variation of parameters. A semi-analytical procedure is proposed to predict the satellites attitude under the influence of the earths shadow. The analytical solution shows that angular variables are linear and periodic functions of time while their conjugates suffer only periodic variations. When compared, numerical and analytical solutions have a good agreement during the time range considered.     

中国区域地磁异常的提取及分析

区域地磁异常的提取对于研究地壳区域的、深部的情况是很有益的。为此,采用地磁台站的多分量磁场强度,经过处理获得了区域地磁异常,提供了丰富的地质信息。