摘要
通过多参数磁性测量,分析探讨了长江中下游干流3种不同粒级(<2mm,<0.28mm和<0.125mm)河底沉积物中磁性矿物的类型、含量、颗粒变化及空间分布特征。3种粒级中,磁性矿物主要富集在<0.125mm的细质沉积物中。对细质沉积物的分析表明,长江中下游干流河底沉积物的磁性矿物含量较长江口高近10倍,类型以亚铁磁性矿物磁铁矿为主,颗粒以假单畴-多畴为主,超顺磁性颗粒含量较低。从中游到下游,磁性矿物含量呈下降趋势,颗粒呈变细趋势。干流磁性矿物含量远高于支流,颗粒远粗于支流,支流泥沙的汇入不断影响干流沉积物的磁性特征。
The environmental magnetic properties of sediments from the middle and lower reaches of Changjiang River have been been investigated by seventeen samples collected along the river between Jingzhou to Jiangyin. Among sediments of three different grain sizes （ 〈 2mm, 〈 0.28mm, 〈 0. 125mm）, the magnetic minerals are mainly contained by samples whose gain size is less than 0. 125mm. Through the testing analysis of finer samples （〈0. 125mm）, the results show that： 1 ）Content of magnetic mineral in sediments from the middle and lower reaches of Changjiang River is high,with the mean Z being 489 × 10^ -5m3/kg,which is l0 times more than that from estuary region. 2）According to typical hysteresis loop, thermal magnetic parameter curve, and demagnetization parameter of the samples, magnetic mineral particles are dominated by ferromagnetic magnetite and a few of incomplete anti-ferromagnetic minerals are also present. Day plots,XARM/X,and XARM/SIRM illustrate that magnetic mineral particles are dominated by single domain （ PSD ） - Multi-domain （ MD ） and the content of super- paramagnetic particles（SP） is less. 3）From the middle reaches to the lower, the mean magnetic susceptibility （%） ranges from 564 × 10^-8 m3/kg （ middle reaches） to 431 × 10^ -8 m3/kg （ estuary）, while the XARM/SIRM is from 12 × 10 ^- 5 m/A （ middle reaches） to 17 ×10^ - 5 m/A （ estuary）, showing a gradual decrease of magnetic mineral content and a gradual thinning of magnetic mineral particles. 4） Another obvious feature is that magnetic mineral content of the mainstream of Changjiang River is much higher than that of its tributaries,while magnetic mineral particles of the mainstream are much coarser. With water and sands inflowing from tributaries into the mainstream,difference of sources may be the main factor controlling the regional difference of the magnetic characters of the river sediments in the middle and lower reaches of Changjiang River.
出处
《第四纪研究》
CAS
CSCD
北大核心
2008年第4期640-648,共9页
Quaternary Sciences
基金
上海市优秀学科带头人项目(批准号:07XD14010)
上海市科委重大科技攻关项目(批准号:07DZ12038)资助
关键词
河底沉积物
磁性矿物
长江中下游干流
river sediments, magnetic minerals, middle and lower reaches of Changjiang River
