ANISOTROPY OF MAGNETIC SUSCEPTIBILITY AND ORIGIN OF THE CHINESE LOESS AND ITS SIGNIFICANCE TO THE QUATERNARY RESEARCH*

Anisotropy of magnetic susceptibility is used in the present study to reveal thedepositional fabric on the original (windblown) loess and secondary (redeposited) loess. The two kinds of sediments mentioned above can be distinguished in terms of their susceptibility anisotropy, e.g. anisotropy degree, magnetic foliation and lineation parameters. On this basis the magnetic fabric of the Pliocene red soil underlaying the loess is studied, and compared with the results of a typical residue-deposited red clay in South China. Considering its geological features, the red soil in Xifeng is regarded probably as aeolian in origin also.     

中国黄土磁颗粒分析及其古气候意义

本文运用岩石磁学方法,对各地黄土和古土壤样品进行低温磁化率、频率磁化率和低温剩磁退磁的研究,证明了黄土中的磁颗以顺磁(单畴和多畴,即>0.03μm)为特点,而古土壤以超顺磁(<0.03μm)为主要特征.黄土中的磁铁矿相对含量(占天然剩磁强度的百分比)比古土壤高,黄土频率磁化率的波谷、波峰分别与剖面黄土和古土壤的风化或土壤化程度相关,说明在黄土形成古土壤的成土过程中,是由于许多细小铁磁性矿物(磁赤铁矿和磁铁矿)生成,使其磁化率增高.这些细小铁磁性矿物的含量反映了古气候温湿程度的强弱和持续时间的长短.     

碳钢低合金钢中磷砷连续测定

当钢中含有砷时 ,会干扰用磷铋钼蓝光度法测定磷。近几年来 ,不少资料报道了采用硫代硫酸钠掩蔽砷能排除此干扰 ,并进一步用此进行磷、砷的连续测定 ,这种方法确实有简单易行操作方便等优点 ,但对于能否掩蔽彻底尚存争议。因此 ,在参考有关文献的基础上 ,采用如下方式进行钢中磷、砷连续测定。本法仍基于磷 (砷 )铋钼蓝光度法连续测定磷和砷含量。试样用稀硝酸溶解 ,高氯酸氧化 ,氢溴酸 -盐酸混合液挥砷 ,蒸发至盐状 ,再用硫硝混合酸溶解盐类并显色测磷。同时 ,另称一份试样 ,在相同的条件下操作 ,但不作挥砷处理 ,比较两次所测的吸光度 ,用…     

MAGNETIC SUSCEPTIBILITY OF CHINESE LOESS AS A PALAEOCLIMATIC INDICATOR

Through the studies on low temperature susceptibility, frequency dependent susceptibility, isothermal remanent magnetization, low temperature magnetization and demagnetization for loess and palaeosols one can easily reveal some significant characters of rock magnetism for the magnetic minerals of ultrafine grain sizes, those are very difficult to identify by general geological methods. It is shown in the present study that both loess and palaeosols cover magnetic grain size from superparamagnetism, single domain to multidomain. Loess samples with relative high peramagnetic minerals are dominantly of thermally stable characteristics while palaeosols have relatively high percentage of superparamagnetic grain (0.01—0.03μm). The relative grain size of magnetite is always finer in palaeosol with higher susceptibility than in loess, indicating that many tiny ferri-ferromagnetic minerals formed during the process of soll formation, which has caused a higher susceptibility in palaeosols than in loess. The cli     

中国黄土磁化率各向异性与成因及其对第四纪研究的意义

本文利用磁化率各向异性来研究原生黄土和次生黄土的沉积组构。根据它们的磁化率各向异性(如各向异性度、磁性面理和线理度等参数的差异),可区分上述两种沉积物。在此基础上,研究了黄土下伏的上新统红壤土的磁组构,并与我国南方残积风化壳的红粘土的结果进行比较,考虑到地质特点,认为西峰黄土下伏的红壤土可能也属风积成因。