海南岛三亚小东海岸礁礁坪沉积物的稀土元素分布特征

REE DISTRIBUTION PATTERN IN THE XIAODONGHAI FRINGING REEF-FLAT SEDIMENTS OFF SANYA,HAINAN ISLAND AND ITS ENVIRONMENTAL IMPLICATIONS

对海南岛三亚小东海东北岸礁礁坪表面沉积物的稀土元素进行了分析,结果表明,沉积物的∑REE为80.22mg/kg,稀土元素含量球粒陨石标准化分布模式呈现轻稀土富集、重稀土亏损,Eu明显负异常(0.58),Ce无异常,Y/Ho低(27.60)的陆相模式特征。根据小东海礁坪沉积样品稀土元素的空间分布情况可以推测出礁坪珊瑚表面沉积物的主要来源是陆源物质,稀土元素分配模式也是陆源物质的直接反映。此外,小东海东北礁坪的地貌和生态分带(从陆地向海方向依次为大块珊瑚带、礁坪内带和礁坪外带)中沉积物受到海洋和生物作用程度不同,但稀土元素的含量和特征参数变化很小。小东海岸礁礁坪沉积物特有的稀土元素分布模式,与其所处地域基岩的稀土元素有关,并受到热带海洋气候影响。

REE in the sediments of the northeast Xiaodonghai fringing reef-flat off Sanya City,Hainan Island were systematically analyzed using Inductively coupled palsma mass spectrometry（ICP-MS）.A high resolution record of rare earth elements（REEs） were obtained.The REE content averages 80.22 mg/kg,and the Chondrite-normalized REE pattern of the reef-flat sediments is characterized by the enrichment of light REE（LREE） and deficiency of heavy REE（HREE）,significantly negative Eu,normal Ce and low Y/Ho ratio（27.80）.It indicates that the terrigenous influx is the major source of the reef-flat surface sediments.In addition,the sediments show a geomorphologic and ecological zonations from large massive corals zone,to inner reef flat zone to outer reef flat zone seaward,indicating the influence of marine and biological effects.However,the REEs content and distribution pattern show little change in the zones.It is believed that the REE pattern mentioned above represents a specific tropical fringing reef-flat REEs distribution pattern.It is probably related to the sediments from the bedrock around the reef-flat,and the joint affect of tropical marine climate.