磁化率测量过程中样品重量对磁化率的影响

磁化率是新生代乃至前新生代地层古环境研究的常规代用指标,被广泛用于风尘堆积、湖泊沉积物以及海洋沉积物中。沉积物磁化率值的准确测量对于古环境重建十分重要。在磁化率测量过程中单个样品质量对于磁化率测量值的影响,目前尚无报道。选取甘肃临洮晚第四纪黄土—古土壤样品,通过测量同一样品不同质量的磁化率,查看样品质量对磁化率值的影响。结果表明,1)样品质量对于磁化率值具有显著影响。样品质量小于6 g时,LT297和LT365样品的低频磁化率值(!lf)随着样品质量增加而变大,质量达到6 g之后!lf基本保持不变。2)样品的频率磁化率(!fd%)与质量之间关系复杂,没有一定的规律,样品质量小于6 g时与大于等于6 g时相比,!fd%变化幅度加大。3)建议测量磁化率的样品净重以不少于6 g为宜。

The Influence of Mass on Magnetic Susceptibility during the Measurement

Magnetic susceptibility, usually used in eolian deposits, lacustrine sediments and marine sediments, has been one of the most important indexes to reconstruct the paleoenvironmental evolution for Cenozoic strata and even pre-Cenozoic strata. Accurate measurement of magnetic susceptibility is critical. Investigating the effect of mass of a specific sample on magnetic susceptibility measurement has not been reported yet. The current study measured the magnetic susceptibilities of various masses for two air-dried samples （LT297 and LT365 ） taken from the late Quaternary loess-paleosol sequences at Lintao County, Gansu Province, in the Chinese Loess Plateau. The effect of mass on susceptibility measurement were in- vestigated. The results show that ： （ 1 ） The effect of mass is significant. When the mass is less than 6g, the low-frequency magnetic susceptibilities （xlf） increases with the increase of mass, and when the mass is no less than 6g the Zlf values remians stable. （2） The relationship between frequency-dependent magnetic susceptibility （xfd%） and the mass is complicated. When the mass is less than 6g, the amplitude of variation of xfd% value is larger than that of mass of more than 6g. （ 3 ） The authors suggest that mass should be no less than 6 g for a sample during the susceptibility measurement.