南海沉积物中蒙脱石的成因探讨  

DISCUSSION ON SMECTITE FORMATION IN SOUTH CHINA SEA SEDIMENTS

作　　者：刘志飞[1] 李夏晶[1] 

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《第四纪研究》2011年第2期199-206,共8页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40925008和40876024);国家重点基础研究发展规划项目(973项目)(批准号:2007CB815906);上海市优秀学科带头人计划(批准号:10XDl406300)资助

摘　　要：南海粘土沉积学的以往研究都认为粘土矿物主要是陆源碎屑提供,包括蒙脱石在内的粘土矿物都是在周边流域经风化作用形成后输入到南海,再经不同洋流的搬运作用而发生沉积,忽略粘土矿物在海底的自生成岩作用及海底火山物质原地风化作用的影响。然而,南海表层及晚第四纪沉积物中蒙脱石含量过高(达到30%～40%以上),似乎同周边流域沉积物的供给能力相矛盾。研究认为,南海蒙脱石有两种最可能的潜在来源或成因:1)主要是陆源碎屑提供,粘土矿物被输入到海洋环境后发生的差异沉降和分选作用可能大幅度提高蒙脱石的相对含量;2)海底火山物质的原地化学风化作用,基性火山喷发物质容易在海水作用下原地风化成自生蒙脱石。文章建议在南海粘土沉积学的未来研究中,加强调查粘土矿物的差异沉降和分选作用以及火山灰的原地风化作用,在理论和机制上研究南海蒙脱石的成因。Previous studies on clay sedimentology of the South China Sea show that clay minerals are mainly detrital particles supplied from continents. All clay mineral species including smectite which carried from various oceanic currents are produced by weathering in surrounding drainage basins, and then transported to the South China Sea and finally deposited. Any significant diagenesis of clay minerals on the seafloor and in situ weathering of submarine volcanic matters are always ignored. However,distinctly high contents of smectite（ over 30% -40% ）in both surface and Late Quaternary sediments of the South China Sea seem inconsistent with the sediment supply ability of the surrounding drainage basins. This study reports the two most potential sources or origins of the South China Sea smectite：（ 1 ）mainly terrigeneous input; the differential settling and selective deposition of clay minerals when discharged in the oceanic environment may greatly increase the relative percentage of smectite ; （2） in situ chemical weathering of submarine volcanic matters; basaltic erupted materials are easily weathered to smectite with action of seawater. In future study on clay sedimentology of the South China Sea, the differential settling and selective deposition of clay minerals and the in situ weathering of submarine volcanic matters are recommended as priorities to address the theory and mechanism of smectite formation in the South China Sea.

关 键 词：蒙脱石 粘土矿物 洋流搬运 晚第四纪南海 

分 类 号：P736.2[天文地球—海洋地质] P534.63[天文地球—海洋科学]