| 摘要: |
| 土地资源是浙江沿海地区发展的重要限制性因素。丰富的滩涂资源一直被视为当地最重要的后备土地资源。准确示踪其物质来源，是科学管理滩涂的重要基础。由于在海水中的长期浸泡，矿物被部分溶解，进而影响沉积物的地球化学和矿物学性质，增加示踪结果的不确定性。通过矿物包裹体的磁学特征研究浙江沿海滩涂的物质来源，由于不受海水溶蚀影响，其结果更可靠。对浙江滩涂沉积物中矿物包裹体的环境磁学研究发现：（1）样品的主要载磁矿物依然是磁铁矿；（2）磁铁矿的含量明显降低，饱和等温剩磁（SIRM）值为9.1×10−5—28.6×10−5 A∙m2∙kg−1，仅是原样的2%—8%；（3）样品的赤铁矿与磁铁矿比重较原样明显降低。酸处理后样品的磁化率值（χ）仅为1.0×10−8—2.3×10−8 m3∙kg−1，极易受到测量误差的影响，因此无法准确反映样品中磁铁矿含量的空间分布特征，而在强磁场下获得的磁学参数更适合于矿物包裹体的环境磁学研究。基于非磁滞剩磁磁化率（χ ARM）、SIRM及饱和等温剩磁退磁参数的散点图和模糊聚类方法可以区分长江和浙江当地河流的物质，是可信赖的物源示踪手段。根据矿物包裹体的磁学特征，提出浙江滩涂沉积物主要来源于当地河流的悬浮颗粒物。 |
| 关键词: 矿物包裹体 环境磁学 滩涂沉积 河流沉积 |
| DOI：10.7515/JEE222054 |
| CSTR： |
| 分类号: |
| 基金项目: |
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| Source tracing of tidal flats in Zhejiang coastal zone: evidence from magnetic mineral inclusions |
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JIANG Baorong, JIA Jia, ZHOU Ruhui, WANG Baiyu
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1. College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, China
2. Institute of Surface Processes and Environmental Change in Qiantang River Basin, Jinhua 321004, China
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| Abstract: |
| Background, aim, and scope The tidal flat is important reserve land resource in Zhejiang coastal zone which are lack of flat land, and the abundant bench resource have always been regarded as the most important reserve land resources. Accurate tracing of the material source is an important basis for scientific management of tidal flats. Unlike the aeolian sediments, the tidal flat sediments may be partly dissolved through the transport and deposit processes, in turn, change the properties of sediments. Due to this, it is urgent to use the proxies, which are not affected by seawater dissolution, to accurately trace sources of tidal flat sediments in Zhejiang coastal zone. Materials and methods In this study, the magnetic characteristics of mineral inclusions were used to trace the source of Zhejiang coastal tidal flat, and then the material links between the tidal flat sediments in Zhejiang coastal, local river sediments, the Yangtze River sediments has been determined. Results The results shown that: (1) the main magnetic-carrying minerals is still magnetite in acid-treated samples; (2) the amount of magnetite within the host mineral in Zhejiang tidal flat sediments is very low, which only accounts 2%—8% of the original samples; (3) the proportion of hematite and magnetite in the magnetic-carrying minerals of acid-treated samples decreased significantly compared with the original samples. Discussion It has been found the magnetic parameters can clearly distinguish the sediments from Yangtze River and local river in Zhejiang. It indicates the magnetic characteristics of mineral inclusion is a good approach to trace the source of tidal flat sediments. Based on the scatter plot and fuzzy cluster analysis of χARM, SIRM and SIRM demagnetization parameters of acid-treated samples, the provenance of tidal flat was analyzed and discussed, which showed that they are mainly sourced from suspended particulates of local rivers. Conclusions Our study revealed that the magnetic properties of acid-treated tidal samples exhibited lower magnetite concentration and finer magnetic crystal particle size, which supports the materials of the tidal flat are mainly contributed by the local river sediments rather than Yangtze River sediments. Recommendations and perspectives These findings indicate the sediment supply in the coastal of Zhejiang will be stable and not decrease obviously, and the environmental magnetic characteristics of sediments is a reliable method that used for provenance tracing in the future. |
| Key words: mineral inclusion environmental magnetism tidal flat sediments fluvial sediments |
