黄东海陆架及朝鲜海峡泥质沉积物的磁学特征比较研究  

COMPARATIVE RESEARCHES ON THE MAGNETIC PROPERTIES OF MUDDY SEDIMENTS FROM THE YELLOW SEA AND EAST CHINA SEA SHELVES AND THE KOREA STRAIT

作　　者：刘健[1] 秦华峰[2] 孔祥淮[3] 李军[1] 

机构地区：[1]国土资源部海洋油气资源和环境地质重点实验室,青岛266071 [2]中国科学院地质与地球物理研究所,北京100029 [3]青岛海洋地质研究所,青岛266071

出　　处：《第四纪研究》2007年第6期1031-1039,共9页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:49976012);国家重点基础研究发展规划项目(批准号:2005CB422304)资助

摘　　要：黄东海陆架和朝鲜海峡等5个泥质沉积区全新世中期以来(自约6kaB.P.至今)的细粒沉积物主要是黄河、长江和朝鲜半岛的河流入海物质在复杂的海洋动力系统中的沉积产物。对取自山东半岛北部近岸泥质区和长江口以南的闽浙沿岸泥质区(舟山群岛近岸海区)的表层细粒沉积物(粘土质粉砂和粉砂质粘土)开展了详细的岩石磁学测试,包括磁化率、等温剩磁和样品磁化率随温度的变化等分析,并将实验数据与以往研究过的济州岛西南陆架区、南黄海东南部陆架区和朝鲜海峡西岸等3个泥质沉积区细粒沉积物的磁学特征进行比较研究。结果表明,上述5处细粒沉积物的磁性矿物主要组分为磁铁矿、磁赤铁矿和赤铁矿,其中低矫顽力磁性矿物为主,平均粒度为准单畴(PSD)。根据磁性矿物的粒度和低矫顽力组分的相对含量,这5处细粒沉积物可以划分为3种类型:第1种类型是朝鲜海峡西岸细粒沉积物,其磁性矿物的粒度最粗,低矫顽力组分的相对含量为中等;第2种类型是南黄海东南部陆架细粒沉积物,其磁性矿物的粒度为中等,低矫顽力组分的相对含量最大;第3种类型是山东半岛北部近岸、闽浙沿岸(舟山群岛近岸)和济州岛西南陆架区的细粒沉积物,其磁性矿物的粒度最细,低矫顽力组分的相对含量最低。在这5处细粒沉积物中,闽浙沿岸(舟山群岛近岸)细粒沉积物的磁性矿物含量最高,其他4处细粒沉积物的磁性矿物含量都较低且大体相当。这种磁学特征的差异反映了物源的不同。从磁学特征来分析,济州岛西南陆架区的泥质沉积物主要来自黄河和长江;南黄海东南部泥质区的主要物源是朝鲜半岛进入黄海的河流,黄河和长江对其没有重要贡献。The present research focuses on the fine-grained sediments in five areas of muddy sediments in the Yellow Sea and East China Sea Shelves and the Korea Strait, which are formed since the middle Holocene at about 6kaB. P. and are mostly derived from the Huanghe River, Changjiang River, and rivers from the Korean Peninsula under the complex system of marine dynamics. Detailed rock-magnetic measurements are conducted on the fine-grained sediments （ clayey silt and silty clay） from the muddy areas in the nearshore of the north coast of Shandong Peninsula and in the coasts of Fujian and Zhejiang Provinces, south of the Changjiang River mouth, including analyses of magnetic susceptibility, isothermal remanent magnetization, and the temperature-dependency of magnetic susceptibility. The analytic data is subject to comparative researches with the previously reported magnetic properties of the fine-grained sediments in three muddy areas in the shelf southwest of the Cheju Island, in the southeastern shelf of South Yellow Sea, and in the west coast of Korea Strait. The results show that the fine-grained sediments in the five muddy areas are characterized by magnetic minerals with magnetite, maghematite, and hematite as the major magnetic components but dominated by low-coercivity ferrimagnetic minerals, and with an average magnetic granulometry of pseudo-single domain（PSD）. In terms of magnetic grain size and relative content of low-coercivity ferrimagnetic minerals, the fine-grained sediments in the five areas can be divided into 3 categories, reflecting the difference in sediment provenance. The first category is sediments from the west coast of Korea Strait, which are the coarsest in magnetic grain size and contain middle amount of low-coercivity ferrimagnetic minerals. The second category is the sediments from the southeastern shelf of South Yellow Sea, which have medium magneitc granulometry and highest amount of low-coercivity minerals. The third category covers those from the nearshore of the north coast of S

关 键 词：黄海 东海 朝鲜海峡 泥质沉积 环境磁学 物源 

分 类 号：P318[天文地球—固体地球物理学] P722[天文地球—地球物理学]