江汉平原主要河流沉积物磁学特征及其与物源区表壳岩性的响应

Magnetic Characteristics of River Sediments in Jianghan Plain and Response to Rock Types of the Provenance

为了建立江汉平原沉积物示踪的磁学模型,对汇入江汉平原的主要河流现代沉积物磁学特征进行了研究,结果表明:(1)在江汉平原范围内,无论长江、汉江,还是周边的漳河、沮水、玛瑙河和清江,它们的现代沉积物的磁学参数特征均显示出明显的差异,而且和源区表壳岩性也显示出极好的相关性;(2)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高;(3)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,并且长江沉积物磁性颗粒总体上要比汉江的粗;(4)在汇入江汉平原的主要支流中,汉江的亚铁磁性矿物含量远远高于其他支流,且磁性矿物的晶粒也比其他支流的粗;(5)除汉江以外的支流中,玛瑙河沉积物中磁性矿物的晶粒比较细且不完全反铁磁性矿物含量较高,漳河中的超顺磁物质含量较高,而清江中不完全反铁磁性矿物含量较高且磁性矿物的晶粒相对较粗.上述结果表明,在江汉平原利用沉积物的磁学特征可达到沉积物物源示踪的目的.

In this paper we report the magnetic characteristics of the confluent river sediments into the Jianghan Plain. Magnetic characteristics are obviously different between different rivers, such as the Yangtze River, Hanjiang River, Zhanghe River, Juhe River, Manaohe River and Qingjiang River, and are well correlated with rock types of the provenance. Magnetic minerals from the Yangtze River and the Hanjiang River are almost ferrimagnetic, which dominate the magnetic characteristics of the samples. Content of ferrimagnetic minerals in the Yangtze River sediments is higher than that in the Hanjiang River. Ferrimagnetic minerals have thicker crystals in the Yangtze River than that in the Hanjiang River, both of which are almost from pseudo-single to multi domain. Higher concentration of ferrimagnetic minerals and thicker magnetic particles are found in the Hanjiang River than the other tributaries of the Yangtze River flowing to Jianghan plain. High concentration of incomplete anti-ferromagnetism minerals and superparamagnetic particles are found in the Mannaohe River and Zhanghe River sediments respectively. High concentration of incomplete anti-ferromagnetism minerals are found in the Qingjiang River sediments, also with thick magnetic particles. Based on the research we conclude that magnetic characteristics of sediments in Jianghan Plain can provide useful information on constraining sediment provenance.