帕里西维拉海盆西北部表层沉积物中粘土矿物的分布特征及物源分析

CLAY MINERALS IN SURFACE SEDIMENT OF THE NORTHWEST PARECE VELA BASIN:DISTRIBUTION AND PROVENANCE

提要应用X射线衍射(XRD)方法对菲律宾海帕里西维拉海盆西北部的257个表层沉积物样品<2μm粘土组分进行了分析。结果表明,本研究区粘土矿物的组合特点是伊利石含量最高(平均含量47%),蒙皂石含量次之(平均含量35%),高岭石和绿泥石含量均很低(平均含量小于10%)。根据该区表层粘土矿物中伊利石、蒙皂石相对含量的分布,可以大体上分为两种含量组合类型,据此也可以划分出两个组合分区:Ⅰ.富伊利石分区,主要位于帕劳海脊和帕里西维拉海沟之间的大部分区域的地形平坦处;Ⅱ.富蒙皂石分区,主要位于研究区东部帕里西维拉海沟附近和南部零星区域。根据粘土矿物的平面分布特征,结合个别样品的扫描电子显微镜(SEM)和X射线能谱(EDS)分析,认为伊利石主要来源于研究区以西陆地及周边岛屿。伊利石的化学指数和结晶度指数表明,伊利石形成于物理风化较强的气候环境并可能与中国内陆黄土有关系,区内大部分蒙皂石具有富铁并含少量镁的特征,基性火山物质的蚀变是其主要成因,高岭石和绿泥石以陆源为主;风力的吹扬是研究区伊利石物质来源的主要输送方式,洋流作用对粘土矿物,尤其是蒙皂石矿物的分布具有一定影响。

The mineralogy, composition, distribution, and provenance of clay minerals in surface sediments in the northwest Parece Vela Basin, the Philippine Sea, were studied. 257 surface sediment samples were analyzed using XRD, and several samples were analyzed using SEM and EDS techniques. Illite, kaolinite, smectite, and chlorite were the main clay components. Surface morphology and chemistry of single clay mineral particle were studied with SEM. The results indicate that, illite is the most abundant for 47%; smectite 35%; and both kaolinite and chlorite were 10%. Two clay mineral assemblages can be recognized in the study area as in Province I . where illite was enriched in flat seafloor between the Palau Ridge and the Parece Vela Rift, and Province Ⅱ. where smectite was enriched in the eastern part as well some patches in the south. Provenance study shows that illite was derived mainly from the East Asia continent and nearby islands, so were kaolinite and chlorite, while most smectite were originated from submarine basalt alteration. Wind was the main agent for transporting illite from land to ocean, and also ocean currents that influenced the distribution of the clays, especially the smectite.