武夷山紫色土磁学特征及其对成壤的指示意义  

Magnetic characteristics of purple soils in Wuyishan and their significance for pedogenesis

作　　者：苏泳岑 吕镔[1,2] 刘鑫 陈梓炫 郑兴芬 SU Y ongcen;LÜBin;LIU Xini;CHEN Zixuan;ZHENG Xingfen(Key Laboratory for Humid Subtropical Eco-geographical Processes of the Ministry of Education,Fujian Normal University,Fuzhou 350007,Fujian;School of Geographical Sciences,Fujian Normal University,Fuzhou 350007,Fujian;Key Laboratory of Western China's Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,Gansu)

机构地区：[1]福建师范大学,湿润亚热带生态地理过程教育部重点实验室,福建福州350007 [2]福建师范大学地理科学学院,福建福州350007 [3]兰州大学西部环境教育部重点实验室,甘肃兰州730000

出　　处：《第四纪研究》2023年第1期154-162,共9页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41877435)资助。

摘　　要：紫色土是非地带性土壤,具有磁性本底值低的特征,是研究成土初始阶段土壤磁性矿物与成土因素关系的良好材料。目前,国内紫色土系统的环境磁学研究处于起步阶段。本研究以福建省武夷山市的紫色土剖面(简称WYS剖面,地理坐标为27°44'24''N,118°00'36''E;海拔216.3m)为分析对象。该剖面发育于白垩系紫红色粉砂质泥岩之上,厚度为0.9m。通过系统的环境磁学研究,结合漫反射光谱一阶导数曲线、色度指标和常量地球化学元素指标,分析其磁学特征的层次分异,探讨磁学参数对成壤的指示意义。结果表明:1)WYS剖面以反铁磁性矿物赤铁矿为主。A层的亚铁磁性矿物磁铁矿含量略有增加,超顺磁(SP)颗粒含量更高,磁颗粒相对更细。成壤作用是造成A层和C层的磁学特征差异的主导因素。2)WYS剖面母岩具有易于物理风化、不易化学风化的特征。由于成土时间短,即便在湿热气候条件下,母质中磁性矿物转化微弱。母质和成土时间是影响紫色土磁学性质的主导因素。3)成壤过程中,少部分赤铁矿转化为磁铁矿。磁学参数的微小变化响应于弱成壤作用,表明紫色土磁学特征可以非常敏感地指示成壤强度。Purple soils are a type of azonal soils with weak background magnetic properties,which make it useful for studying the relationship between soil magnetic minerals and soil-forming factors in the initial stage of pedogenesis.However,so far there are few environmental magnetic studies of purple soils in China.We studied a purple soil profile(27°44'24''N,118°00'36''E;altitude 216.3m)in Wuyishan City,Fujian Province,China,termed the WYS section.The profile is developed on Cretaceous purplish red silty mudstone and is 0.9-m thick;it has a typical humus-rich A horizon,overlying the parent material C horizon.We collected seven samples from the A horizon(0~30cm)at 5-cm intervals,and six samples from the underlying C horizon,at 10-cm intervals.Magnetic parameters,chromaticity index,diffuse reflectance spectroscopy(DRS)and major element contents were measured on all the samples,with the aim of determining the pedogenic significance of the magnetic properties.The principal results are as follows:(1)The most abundant magnetic mineral throughout the profile was the imperfect antiferromagnetic mineral hematite.There were minor differences in the magnetic properties of the A and C horizons.The content of the ferrimagnetic mineral magnetite was slightly higher in the A horizon,and a small quantity of the iron oxyhydroxide goethite was also present.Additionally,the content of superparamagnetic(SP)particles was higher in the A horizon.(2)The parent material of the WYS section,purplish red silty mudstone,is susceptible to physical weathering,but the degree of chemical weathering is relatively weak,which is consistent with the short duration of pedogenesis.Therefore,the degree of magnetic mineral transformation of the parent rock was limited,despite the humid and warm climate.The parent material and the duration of pedogenesis are the dominant factors affecting the magnetic properties of the purple soil.(3)During pedogenesis,a small quantity of hematite in the weathered crust of the purple silty mudstone is reduced under the combi

关 键 词：环境磁学 磁化率 赤铁矿 成壤作用 紫色土 

分 类 号：P595[天文地球—地球化学] P318[天文地球—地质学]