湿润亚热带花岗岩风化壳发育红壤中不同类型磁赤铁矿及其成因  

DIFFERENT TYPES OF MAGHEMITE AND THEIR GENSIS IN HUMID SUBTROPICAL RED SOIL DERIVED FROM GRANITE WEATHERING CRUST

作　　者：刘鑫 吕镔[1,2,3] 刘秀铭[1,2,4] 郑兴芬[1,2] 陈梓炫 杜佳昊 LIU Xin;LüBin;LIU Xiuming;ZHENG Xingfen;CHEN Zixuan;DU Jiahao(State Key Laboratory for Subtropical Mountain Ecology of the Ministry of Science and Technology and Fujian Province,Fujian Normal University,Fuzhou 350007,Fujian;School of Geographical Sciences,Fujian Normal University,Fuzhou 350007,Fujian;Institute of Geography,Fujian Normal University,Fuzhou 350007,Fujian;Department of Earth and Environmental Sciences,Macquarie University,Sydney NSW 2109,Australia;Key Laboratory of Western China's Environmental Systems,Ministry of Education,College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,Gansu)

机构地区：[1]福建师范大学湿润亚热带山地生态国家重点实验室培育基地,福建福州350007 [2]福建师范大学地理科学学院,福建福州350007 [3]福建师范大学地理研究所,福建福州350007 [4]Department of Earth and Environmental Sciences,Macquarie University,Sydney NSW 2109,Australia [5]兰州大学资源环境学院,西部环境教育部重点实验室,甘肃兰州730000

出　　处：《第四纪研究》2021年第1期63-77,共15页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41877435和41772180);福建师范大学创新团队项目(批准号:IRTL1705)共同资助。

摘　　要：本研究对福建省武夷山市发育于花岗岩风化壳上的亚热带红壤剖面进行了系统的热磁和常温磁学测量,剖析该剖面磁学性质与成土因素(气候和母质)的关系,探讨2种类型磁赤铁矿的成因。研究结果表明:该剖面具有较高的亚铁磁性矿物含量,磁颗粒以多畴(MD)颗粒为主。土壤发育过程中,成土作用使磁颗粒变细、单畴(SD)颗粒增加、亚铁磁性矿物含量降低使得磁化率减小。红壤剖面中至少存在2种不同类型的磁赤铁矿:磁赤铁矿A,在300~450℃即转化为赤铁矿,不能测得居里点;磁赤铁矿B,在650℃以上才较为完全地转化为赤铁矿,可测得645℃的居里点。磁赤铁矿A是水铁矿转化为赤铁矿的中间产物,该化学反应过程在氧化环境下广泛存在,是被普遍认识的一类磁赤铁矿。土壤淀积层、淀积-母质过渡层、母质层的主导磁性矿物磁赤铁矿B由含铁硅酸盐矿物经风化成土作用演化而成,而非原生磁铁矿低温氧化;磁赤铁矿B形成与气候条件(较高的气温)和母岩/母质物质组成有关,两者缺一不可。In order to explore the magnetic characteristics of the red soil section in the humid subtropical region and the relationship between its magnetic properties and soil forming factors(climate and parent material),this study selected a Wuyishan red soil section(WYS section)derived from granite weathering crust.The section was located in Wuyishan City,northern Fujian Province,with geographic coordinates of 27°37’55.67″N and 117°59’40.59″E,it belonged to a humid climate zone of mid-subtropical monsoon.The multi-year average temperature in this area was 18.3℃,and the multi-year average precipitation was 1926.8 mm.The section was 4.5 m thick,and could be divided into 4 layers from top to bottom:Horizon A(leached horizon,0~20 cm),horizon B(illuvial horizon,20~230 cm),horizon BC(B~C transition layer,230~330 cm),horizon C(parent material horizon).After removing the surface floating soil,46 soil samples were collected at intervals of 10 cm;In addition,one semi-weathering parent material sample and one weakly weathering parent rock sample were collected in the outcrop area within2 meters of the section.From the comparison of the degree of weathering:Soil samples(horizon A,horizon B,horizon BC and horizon C)>semi-weathering parent material samples>weakly weathering parent rock samples.This study carried out detailed room temperature magnetic parameters measurement on all samples,conducted thermomagnetic analysis on representative samples,and performed sample magnetic separation at equal intervals of20 cm.System room temperature magnetic parameters were also performed on the remaining samples after magnetic separation.The following results were obtained:The overall magnetic susceptibility of the WYS section was relatively high,and the content of magnetic minerals was relatively high.The magnetic particles in the horizon BC and horizon C of the section were mainly multi-domain particles.With the decreased of depth,the magnetic particles became finer and single-domain particles increase.There were almost no superpar

关 键 词：湿润亚热带 红壤 高温磁学 居里点 磁赤铁矿 

分 类 号：P318[天文地球—固体地球物理学] P534.63[天文地球—地球物理学]