中太平洋第四纪沉积物地球化学特征及沉积环境

Geochemistry and sedimentary environments of the Quaternary sediments in the mid-Pacific Ocean

关键词:  中太平洋  第四系  地球化学

Key words:  mid-Pacific Ocean  Quaternary  geochemistry

摘要:

本文采用多元统计分析的方法,研究了中太平洋地区第四纪沉积物中元素含量的地球化学特征,探讨了其物质来源及沉积环境。研究表明:元素含量在垂向上有3次比较明显的变化,Al₂O₃、Fe₂O₃、TiO₂、MnO、P₂O₅的含量在早期沉积物中变化不明显,中期含量明显增加,晚期则减少。CaCO₃、CaO、Sr在晚期沉积物中含量较高,并与前者常微量元素含量形成明显的互为消长关系。元素的相关性分析和R型因子分析揭示SiO₂与Al₂O₃、Fe₂O₃、K₂O、MnO、TiO₂、Cu、Ni、Zr等元素为正相关关系,说明元素组合共生关系好,在沉积物中所起的作用相近,地球化学行为比较相似,主要受陆源碎屑沉积及火山活动的影响;与CaCO₃、CaO、Sr之间为负相关关系,说明后者与前者元素氧化物之间内在关系较为疏远,相关性差,沉积物源不同,主要与生物作用有关。中太平洋第四纪的沉积物主要为钙质硅质粘土和钙质软泥,早期沉积物受火山活动的影响较大,晚期与生物作用密切相关,表明该时期沉积物主要形成于陆源、生物源、火山源物资供应比较充足的沉积环境。

Abstract:

The geochemistry, sediment sources and sedimentary environments are examined on the basis of analyses of the major and trace element contents in the sediments from the PC5356, PC5362 and PC5417 drill holes in the mid-Pacific Ocean, in integration of the multivariable statistical analysis. Vertically, there are three phases of marked changes in element contents in different burial depths of sediments. The contents of Al₂O₃, Fe₂O₃, TiO₂, MnO and P₂O₅ remain unchangeable in the early sediments, and show a marked increase in the middle sediments and a decrease in the late sediments in which CaCO₃, CaO and Sr contents are relatively higher and there is a negative correlation with the trace element contents. The element correlation analysis and R-mode factor analysis show that there is a positive correlation between SiO₂ contents and Al₂O₃, Fe₂O₃, K₂O, MnO, TiO₂, Cu, Ni and Zr contents indicating the same terrigenous origin, while a negative correlation between SiO₂ contents and CaCO₃, CaO and Sr contents indicating a distinct biogenetic origin. The Quaternary sediments in the mid-Pacific Ocean consist mainly of calcareous-siliceous clay and calcareous ooze. They may owe their origin to the volcanism in the early stages, and biological action in the late stages.