西峰和段家坡剖面S_(5-1)层段磁性矿物的成分与组合特征  

Magnetic mineral composition and the assemblage feature in layer S_(5-1) of Xifeng and Duanjiapo sections

作　　者：贾蓉芬[1] 彭先芝[1] 周正[1] 刘德汉[1] 王冠鑫[1] 王德强[1] 

机构地区：[1]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640

出　　处：《地球化学》2004年第2期171-177,共7页Geochimica

基　　金：国家自然科学基金(40073029);中国科学院广州地球化学研究所所长基金(A05-020501-4)

摘　　要：从西峰和段家坡黄土剖面S5-1层段中分选出<30μm粒级、磁性相对最强的组分(分别为XS-4J和DS-4J),先后进行了MPV-3光学显微镜的观察与反射率测定、矿物的扫描电镜能谱测定和X射线衍射物相分析。两个样品的磁性矿物均以风尘碎屑状的钛铁氧化物为主。XS-4J样矿物的反射率和Fe的含量都普遍较高,磁性矿物除磁(赤)铁矿、赤铁矿外还见有含铁高的氧化物(Fe72.20%～86.70%,质量分数)和含Cr、Ni的钛铁晶石或钛铁矿。DS-4J样的磁性矿物中Fe与Ti元素呈明显的负线性相关关系,Si、Al、Ca的含量较高,矿物以磁(赤)铁矿、赤铁矿、针铁矿和褐铁矿为主,并明显见有磁性矿物被溶蚀和新生的磁(赤)铁矿。磁性矿物成分与组合特征的差异反映了西峰与段家坡S5-1岩石中磁性矿物的物质来源与保存条件有较明显的差异。The strongest magnetic and fine components (< 30 μm, XS 4J and DS 4J) which are most environmentally sensitive were separated from S5-1 in Xifeng and Duanjiapo sections for morphometry and reflectance measurement by MPV 3, element content examination by SEM ESD and mineral phase analysis by XRD, respectively. The results show that detrital iron titanium oxides of aeolian origin are in majority in the magnetic mineral components of XS 4J and DS 4J. In XS 4J, the reflectance and Fe content of magnetic minerals are often higher, besides magnetite (Fe3O4), maghemite (γFe2O3) and hematite (Fe2O3), some oxide containing high Fe (mass fraction 72%～86.67%), ilmenite (FeTiO3), magnetite ulvospinel (Fe(FeCr)O4 and Fe(FeNi)O4) are also found. In DS 4J, the negative relationship of Ti and Fe is observed, and Mn, Si, Al and Ca elements are often found in the magnetic minerals, and a lot of goethite (FeOOH) and limonite (containing Si and OH) minerals, as well as magnetic mineral corrosion and some neogenic magnetic minerals are also found. The differences in the magnetic mineral compositions and the assemblages between Xifeng and Duanjiapo sections reflect that there are obvious differences in the source rocks and in the maintenance conditions.

关 键 词：磁性矿物 钛铁晶石 钛铁矿 氧化-还原 黄土-古土壤序列 

分 类 号：P599[天文地球—地球化学] P579[天文地球—地质学]