西太平洋海山盆地沉积物黏土矿物特征及其指示意义

Clay mineral characteristics of sediments in the seamount basin of the Western Pacificand its indicative significance

深海沉积物中的黏土矿物组合特征能反映物源区古气候与古环境的变化。前人已有较多关于马里亚纳海沟以西太平洋沉积物黏土矿物组合特征方面的研究,但对马里亚纳海沟以东黏土矿物组合特征的研究较少,从而限制了对亚洲大陆风尘输入与太平洋深海沉积环境之间关系的深入认识。本文以2019年大洋54航次在西太平洋马尔库斯-威克海山区采集到的31个表层样和1个柱状样为研究对象,结合收集到的西太平洋海域及附近地区的数据,开展了黏土矿物组成与分布特征、物质来源等研究。结果表明,研究区表层沉积物中的黏土矿物类型以伊利石为主,含量平均值为69%;绿泥石和高岭石次之,含量平均值分别为16%与11%;蒙脱石最少,含量平均值为3%。柱状样黏土矿物组合与表层沉积物基本一致,但在250 cm深度以下,蒙脱石含量明显增高,伊利石含量相对减少。物源分析表明,亚洲风尘是研究区伊利石的主要物源,高岭石和绿泥石的主要物源可能也是亚洲风尘,东亚冬季风是这些风尘物质的主要搬运营力。沉积物中的蒙脱石则主要由海底火山物质风化形成。P04柱上部伊利石含量增加而蒙脱石含量降低的变化响应了中更新世以来亚洲风尘输入量增加的过程。

The clay mineral assemblage in abyssal sediments can reflect the paleoclimate and paleoenvironment changes of the provenance area.Predecessors have many studies about the characteristics of clay mineral assemblages in the Pacific sediments west of the Mariana Trench,but the less research on the characteristics of clay mineral assemblages in the east of the Mariana Trench limits a deeper understanding of the relationship between the Asian aeolian dust input and the Pacific deep-sea sedimentary environment.In this study,31 surface samples and 1 core sample collected in the Malkus-Wake Seamount area of the Western Pacific during the 2019 DY54 cruise were analyzed for clay minerals,combined with the data collected in the Western Pacific and nearby areas,we discussed the characteristics of composition,distribution and the provenance of clay minerals.The results showed that illite was the main clay mineral in surface sediments of the study area,with an average value of 69%;the content of chlorite and kaolinite were the second,with an average of 16%and 11%respectively;that of smectite was the least,with an average of 3%.In the core P04,the assemblage of the clay mineral was basically the same as surface samples,but below 250 cm depth,the content of smectite increased significantly,while the content of illite decreased relatively.Provenance analysis showed that Asian aeolian dust was the main source of illite in the study area,and kaolinite and chlorite might also be from Asian aeolian dust,and the East Asian winter monsoon was the main transport force of these clay minerals.The smectite in sediments could be mainly formed by weathering of submarine volcanic materials.The increase of illite content while the decrease of smectite content in the upper layer of core P04 sediment was responded to the increase of Asian aeolian dust input since the Middle Pleistocene.