长江、汉江沉积物磁学特征比较研究

A COMPARATIVE STUDY ON MAGNETIC PROPERTIES OF SEDIMENTS FROM THE YANGTZE RIVER AND THE HANJIANG RIVER

长江和汉江现代沉积物的磁学特征分析研究结果表明:1)长江和汉江现代沉积物中铁磁性矿物均以亚铁磁性矿物为主,它们主导了样品的磁性特征。但长江沉积物比汉江沉积物亚铁磁性矿物含量要高;2)长江和汉江沉积物的亚铁磁性矿物晶粒都以假单畴～多畴为主。相对汉江沉积物,长江沉积物磁性颗粒总体上要比汉江的粗;3)长江沉积物中的不完全反铁磁性矿物含量比汉江高,但不完全反铁磁性矿物对沉积物磁性参数x和SIRM的贡献却比汉江的小;4)长江上游金沙江段比长江中游(宜昌-武汉)江段沉积物中亚铁磁性矿物含量要高,且长江中游沉积物样品磁性颗粒要比长江上游的偏细,这可能与搬运距离有关;5)长江样品的磁性参数的变化区间比汉江大,数据间的相关性也比汉江差。这可能与长江较汉江流域范围广、支流多、物源复杂有密切的关系。

The paper analyzed and compared magnetic properties of modern sediments from the Panzhihua to Xiangjiaba Reservoir and from the Yichang to Wuhan segment respectively in the upper and middle reaches of the Yangtze River,as well as from the Shiyan to Wuhan segment in the Hanjiang River. Our results are as the following： （1） The ferromagnetic minerals in these specimens are mainly ferrimagnetic minerals, as the magnetic properties of sediments are dominated by ferrimagnetic minerals. But the ferrimagnetic mineral contents of the Yangtze River sediment is higher than those in sediments from the Hanjiang River. （2）The pseudo-single domain and multi- domain particles are main crystal grains of the ferrimagetic minerals of these sediments. On the whole,the magnetic particles of the Yangtze River sediments are coarser compared with the Hanjiang River sediments. （3） The imperfect antiferromagnetic mineral contents of the Hanjiang River are significantly lower,whereas their contribution to the magnetic properties of the sediments from the Yangtze River is relatively low. （4） The ferrimagnetic mineral contents of sediments from the upper reaches（The Jinsha River）are much higher than those of the middle reaches（Yichang-Wuhan） of the Yangtze River, while the latter is relatively finer for the magnetic particles. This is likely related with transportation distance. （5）The range of magnetic parameters of the Yangtze River is broader than that of the Hanjiang River and its data correlation is worse than that of the Hanjiang River,which probably has a close relation with the richer source of materials and more tributaries flowing into the Yangtze River.