摘要
应用矿物磁测、X-衍射和电镜技术对浙江省第四纪红土的磁性与氧化铁矿物学特征进行了研究。结果表明，均质层和网纹层的磁化率（x）、频率磁化率（xfd）、软剩磁（SoftIRM）、非滞后剩磁（ARM）、他和等温剩磁（SIRM）和剩磁矫顽力（（BO）CK）等磁性参数存在明显差异，均质层的磁化率和饱和等温剩磁分别是网纹层的6倍和4倍；第四纪红土的磁化率主要由风化成土作用产生的超顺磁性颗粒（SP）和稳定单畴颗粒（SSD）贡献，它们的磁化率值与频率磁化率和非滞后剩磁是显著正相关；均质层中DCB处理后的磁化率和xfd损失量明显高于网纹层，其DCB处理损失的磁性主要是次生的SP和SSD颗粒，DCB处理后损失的磁化率与频率磁化率呈指数正相关；根据均质层的IRM获得曲线、剩磁矫顽力、X－衍射和透射电镜观察证明红土中的氧化铁矿物组成主要是圆片状的赤铁矿、鱼鳞状的磁赤铁矿和针状的针铁矿。对红土磁性成因的物理机制进行了讨论，初步认为第四纪红土中磁性矿物的数量、粒度、类型等特征的变异指示了红土化作用的变异，可作为研究第四纪环境变化的手段之一。
Characterization of magnetism and iron oxide mineras for Quatemary red earthwas inveshgated by mineral magnetic measurements, X-ray powder diffraction andtransmission electron microscopy. The data indicated that there were significantdifferences in magnetic susceptibility (X), frequency dependent suscephbility (Xfd)'anhysteretic remanent magnetization, saturation isothermal remanent magnetization(SIRM and demagnetizahon prneters between homogeneous horizon and reticularhorizon for red earth. It was found that X and SIRM of homogenous horizon weresix and four times more than that of rehcular horizon, respectively. Magneticsusceptibility of red earth mostly come from the contribution of pedogeneticferrimagnetic minerals that were superparamagnetic (SP) and stable-single domain (SSD)grains. It was found that X of red earth was highly significantly correlated with Xfdand ARM values. Following dithionite-citrate bicarbonate (DCB) treatmenL X lossamount for homogeneous horizon was significantly greater than that for reticularhorizon. Magnetic suscephbility removed by DCB has been attributed to presence ofthe secondary SP and SSD grains. Based on the acquisition curves of IRM,demagnetization curves, X-diffration pattem and morphology observation, iron oxideminerals for red earth were comprised of hemahte, maghmatite andxgoethite. Wesuggest that concentration, grans size and mineral assemblage of ferrimagnetic phasebe reflection and signature of the Quatemary environmenta changes. It can beconcluded that L Xfo, x and Xfd removed by DCB beatment were increased withincreasing red earthening. Thus, these differences are considered effective indicatorsfor the quantitative study of the environmental fluctuations recorded.by the Quatermaryred earth.
出处
《土壤学报》
CAS
CSCD
北大核心
2000年第2期182-191,共10页
Acta Pedologica Sinica
基金
国家自然科学基金!49301010
关键词
第四纪红土
磁性
氧化铁
环境变迁
环境磁学
Quaternary red earth, Magnetic susceptibility, Frequent dependent susceptibility, Magnetic minerals, Environmental changes
