冲绳海槽北部稀土元素沉积地球化学研究

GEOCHEMICAL CHARACTERISTICS OF RARE EARTH ELEMENT IN THE SEDIMENTS OF NOKTH OKINAWA TROUGH

本文对冲绳海槽北部（１２６°３０＇一１２９°３０＇Ｅ；２８°３０＇一３２°００＇Ｎ）海底表层沉积物和４个柱状岩芯沉积物样品的稀土元素（ＲＥＤ）沉积地球化学特征进行了系统的分析。研究结果表明，调查区表层沉积物ＲＥＥ的分布主要与沉积物的物质组成有关，特别是海洋生物沉积组份的比例不仅影响ＲＥＥ，总量的分布，而且影响标准化 ＲＥＥ分布模式的形态。研究海区以海槽中轴为界，东、西两侧海区的ＲＥＥ分布明显不同，说明它们在沉积环境和沉积物物源上有着重要的差异。对岩芯样品的分析结果则证明，ＲＥＥ的分布可以很好地反映沉积学上的岩性特征，标准化ＲＥＥ分布模式形态上的变化可能暗示着调查区沉积环境的一次较大变化。

surface samples and 4 cores of sediments were recovered from the north OkinawaTrough(126°30'一129°30'E,28°30'一32°00'N).The analysis of these samples for rareearth elements(REE )reveals that the effects on both concentrations and normalizedpatterns of REE are mainly from sediment compositions,especially the proportion of bio-genic component, instead of grain size of sediments. The north area of the trough is di-vided into east part(near Ryukyu Arc)and west part(adjacent to East China Sea shelf)by mid-trough axis. The geochemical differences between the sediment samples fromthese two parts have suggested that they had different sedimentary environment and ma-terial sources. The research of core samples has verified a sharp change in the sedimenta-ry environment in the light of the concentration distribution and the normalized patternsof REE,This change corresponded to the boundary between Late Pleistocene andHolocene.