论文部分内容阅读
磁铁矿是岩石、土壤和沉积物中少量而又普遍存在的副矿物,是环境磁记录的主要载体。磁铁矿在表生地质过程中受到机械、生物和化学风化作用使其结构、粒径、氧化程度、磁学性质发生一系列变化,这些变化对环境磁学以及表生地质过程的研究具有重要意义。从矿物学角度研究了磁铁矿粒径、相转变、氧化程度和磁化率随着研磨时间的变化规律。结果表明,平均粒径为4μm的磁铁矿在研磨1 h后粒径变化趋于稳定,但随着研磨时间的增加,磁化率逐步降低而氧化率逐渐增加。通过对研磨后样品进行XRD分析表明,随着研磨时间的增加,磁铁矿衍射峰强度明显减弱,衍射峰宽化,赤铁矿的衍射峰强度逐渐增强。由此可见,原生磁铁矿(对沉积物而言属于碎屑磁铁矿)低温氧化产物是赤铁矿而不是磁赤铁矿。在表生地质演化过程中颗粒的机械碰撞不仅使磁铁矿颗粒变细,而且可能影响到磁铁矿常温氧化、磁学性质和晶体结构。
Magnetite is a small but ubiquitous accessory mineral in rocks, soils and sediments and is the main carrier of environmental magnetic recording. Magnetite has been subjected to mechanical, biological and chemical weathering in epigenetic geology to make a series of changes in its structure, grain size, oxidation degree and magnetic properties. These changes are of great importance to the study of environmental magnetism and supergene geology significance. From mineralogical point of view of the magnetite particle size, phase transition, degree of oxidation and magnetic susceptibility changes with grinding time. The results show that the average particle size of 4μm magnetite after grinding 1h particle size changes stabilized, but with the grinding time increases, the magnetic susceptibility gradually decreased and the oxidation rate increased. XRD analysis of the samples after grinding shows that the diffraction peak intensities of magnetite are obviously weakened, the diffraction peak is broadened and the diffraction peak intensity of hematite is gradually enhanced with the increase of grinding time. Thus, the native magnetite (a detrital magnetite for sediments) is a hematite instead of a maghemite. The mechanical collision of particles not only makes the magnetite particles thinner during the epoch evolution, but also may affect the magnetite normal temperature oxidation, magnetic properties and crystal structure.