摘要
对中国大陆科学钻探孔区——江苏省东海县毛北地区的55块榴辉岩样品进行了古地磁研究,并从中抽样测试了等温剩磁、磁滞迴线、磁组构、热磁化率以及电子探针和镜下分析,结果表明,毛北榴辉岩有两组稳定的剩磁,即反向磁化和正向磁化,稳定剩磁方向分别为:D=94.3°,I=-29.1°和D=273.7°,I=15.4°,携带正向磁化与携带反向磁化样品的磁化强度和密度变化很大;毛北榴辉岩的磁各向异性度非常弱,最小轴方向很难确定;等温剩磁和磁滞迴线显示磁铁矿可能是毛北榴辉岩的主要载磁矿物,且在以Mr/Ms和Hcr/Hc的对数为纵、横坐标的图上落在视单畴(PSD)区域.根据磁性特征,对毛北榴辉岩的磁性载体成因、剩磁获得机制及构造意义进行了讨论.
In this paper, a pilot study of paleomagnetism and rock magnetism is done on 55 eclogite samples collected from Maobei area, Donghai County, Jiangsu Province. Synchronously, some of the samples are analyzed by electron-probe and scanning electric microscope, and tested for the isothermal remanence, hysteresis loop, magnetic fabric, thermal magnetic properties. The result indicates that there are two groups of stable remanence, i.e. the normal polarity and reversed polarity. The remanence orientations are: D=94.3°, I=-29.1° and D=273.7°, I=15.4° respectively. The magnetization and the density of the samples with normal polarities are very different from that of the samples with reversed polarities. The magnetic anisotropy is weak, and the minimum axis is hardly confirmed. The isothermal remanence and the hysteresis loop show that the magnetic carriers of the eclogite may be SD (single domain) and PSD (pseudo-single domain) magnetite. According to the magnetic property, the cause of the formation of magnetic carrier, the causation of the remanence, and the significance for the geotectonic are discussed at the end of the paper.