风化作用对铁陨石矿物学特征影响的探讨

本文对南丹IIICD铁陨石的矿物学特征进行了研究,并与同为铁陨石但化学分类不同的阿根廷IAB铁陨石和西伯利亚IIB铁陨石进行了对比,重点探讨了风化作用对铁陨石矿物学特征的影响.首先用偏光显微镜、静水称重、扫描电镜观察了样品的基本矿物学特征和微形貌特征,然后用振动式样品磁强计、X射线衍射与电子探针能谱半定量测试研究了样品的磁学性质、物相和化学组成.研究结果表明,南丹铁陨石在较强的自然风化作用下,光泽变弱为土状光泽,相对密度降低;风化产生的反铁磁性物质会使陨石的磁性下降;另外,样品表面物相组成也发生较大变化,以针铁矿(FeOOH)和磁铁矿(Fe₃O₄)等铁的次生矿物为主;但风化壳以下的矿物物相及化学成分均未发生明显变化,以Fe、Ni为主的铁纹石、镍纹石物相存在.

The effects of weathering on the mineralogical characteristics of iron meteorites

In this paper, the authors studied the mineralogical, magnetic, phase and chemical composition characteristics of IIICD iron mereorite from Nandan, and compared this kind of mereorite with Argentine IAB iron meteorite and Siberian IIB Iron meteorite that belong to different chemical types, focusing on the weathering effects. The mineralogical characteristics of the sample were observed by means of polarizing microscope, hydrostatic weighing, and scanning electron microscope, and the magnetic properties, phases and chemical composition of iron meteorites were studied through vibrating sample magnetometer, X-ray diffraction and electron microprobe spectroscope semi-quantitative test. The results show that weathering can change the mineralogical properties of iron meteorite. With the strongly weathered iron meteorites from Nandan as an example, the authors have found that the luster is weakened to earthy luster, and the relative density is reduced. Moreover, antiferromagnetic substances produced by weathering can reduce the magnetism of iron meteorite. In addition, mineral phases also change greatly with secondary minerals of iron being such main phases as goethite (FeOOH) and magnetite (Fe₃O₄). Nevertheless, below its crust of weathering, the mineral phases and chemical composition have not changed significantly, and exist as kamacite and taenite phases dominated by Fe and Ni.