摘要
近年来发现台湾西部河流泥沙对东海内陆架区域,尤其是泥质区南部的贡献不可忽视.建立有效的判源指标是识别海洋沉积物的前提.本文拟从大陆和台湾河流表层沉积物入手,分析其磁性和磁性矿物特征,并建立物源判别指标.通过对大陆东南沿海河流（长江、钱塘江、瓯江和闽江）和台湾西部河流（浊水溪、大安溪、大甲溪和乌溪）44个表层沉积物样品细颗粒组分（＜45μm）进行多参数磁性测量、热磁和X射线衍射分析,发现长江和浙闽河流沉积物磁性较强,磁性矿物颗粒较细,以磁铁矿为主;台湾西部河流沉积物磁性很弱,SIRM/x.值异常高,磁性矿物颗粒较粗,磁黄铁矿为主要磁性矿物,浊水溪最具代表性.这一磁性和磁性矿物的差异主要是由流域母岩以及流域内沉积物风化搬运过程的不同导致.本文提出基于SIRM/xlf和HIRM磁性参数的物源判别指标,可较好地示踪大陆东南沿海河流和台湾西部河流的沉积物.
Sediment source-sink is a hot topic in recent years. This process is not only existing in the riverine system but also going on in the sea. Zhejiang-Fujian Coast Current and Taiwan Warm Current in the East China Sea control the dispersal of terrestrial sediments derived from Yangtze River, Zhejiang-Fujian rivers and west Taiwan rivers. These sediments deposit along the coast, forming the inner shelf mud of East China Sea. To trace the sources of marine sediments, a prerequisite is to find an effective provenance indicator for these riverine sediments. The present study aims to set up such a provenance indicator through analyzing surficial sediments from the mainland （Yangtze River, Qiantang River, Ou River and Min River） and west Taiwan （Choshui River, Da＇an River, Dachia River, and Wu River） rivers. The measurement of the magnetic properties, thermomagnetic and X-ray diffraction analysis （XRD） were tested for the fine sediments （a fraction of less than 45 μm） of 44 riverine samples. The results showrivers and west Taiwan rivers. The Yangtze River are characteristic of highest χlf （106× 10-8m3/kg in average, all data in abstract is in average） and HIRM （464×10-6Am2/kg）, and a lower SIRM/χlf （10kA/m）. Zhejiang- Fujian rivers including Qiantangjiang, Oujiang and Minjiang are similar to the Yangtze River, with higher χlf （62× 10-8m3/kg） and HIRM （297 × 10-6 Am2/kg）, and a lower SIRM/χlf （ 13 kA/m）. By comparison, Taiwan Choshui sediments are featured by lower χlf （24×10-8m3/kg） and HIRM （156×10-6Am2/kg）, half of them with an anomalously high SIRM/χlf （〉60kA/m; maximum of 136kA/m）. The west Taiwan short rivers have low χlf （11×10-8m3/kg） and HIRM （14×10-6AmZ/kg）. The results of thermomagnetic curves show that the mainland rivers are represented by magnetite peak of 580℃. The west Taiwan rivers are characterized by pyrrhotite peak of 320℃, especially in the Choshui River. The results of XRD confirm that characteristic diffraction peaks of magnetite and pyrrhotite occur respectively in the sediments of mainland and west Taiwan rivers. That＇s to say, the dominant magnetic minerals are magnetite in the mainland rivers and pyrrhotite west Taiwan rivers which is the reason of anomalously high SIRM/χlf. Such a difference is believed related to basin-wide geomorphology and geology including： （1） the difference of parent rocks （representative E＇mei basalt block of the Yangtze basin; intermediate-acidic igneous rock of Zhejiang-Fujian coasts and low-grade metamorphic rocks of west Taiwan） ; and （2） the different process of weathering and transportation in the riverine system （long duration in the Yangtze River system vs. short in the west Taiwan rivers）. Based on the above analysis, this paper proposes a provenance indicator of SIRM/χlf and HIRM, which would be effective for tracing sediments derived from mainland and west Taiwan rivers.
出处
《第四纪研究》
CAS
CSCD
北大核心
2016年第1期227-236,共10页
Quaternary Sciences
基金
国家自然科学基金项目（批准号：41301214）资助 致谢本文浊水溪河口部分样品由台湾国立中山大学刘祖乾教授提供,华东师范大学河口海岸学国家重点实验室张卫国老师在磁性参数的解释上给予许多帮助,刘演博士协助野外采样工作,在此一并谨致谢忱.
关键词
长江
浙闽河流
台湾西部河流
磁性特征
物源
Yangtze River, Zhejiang-Fujian rivers, west Taiwan rivers, magnetic properties, sediment provenance
