加瓜海脊铁锰结壳的年龄及其定年方法适用性比较  

Age of a Fe-Mn crust on the Gagua Ridge and applicability studies of dating methods

作　　者：罗顺开 周怀阳[1] 赵国庆[2] 袁伟 LUO Shunkai;ZHOU Huaiyang;ZHAO Guoqing;YUAN Wei(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;Institute of Earth Environment,Chinese Academy of Science,Xi'an 710061,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]中国科学院地球环境研究所,西安710061

出　　处：《海洋地质与第四纪地质》2022年第1期135-145,共11页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目“南海深部计划重点项目”(91428207)。

摘　　要：深海铁锰结壳的定年对其记录的百万年尺度古海洋环境变化研究至为关键。综合运用10Be/9Be、Co经验公式、230Thex/232Th和磁性地层学,对采自加瓜海脊的铁锰结壳样品开展了系统的年代学对比研究。结果表明:相对于开阔大洋的铁锰结壳,较多的陆源物质输入造成了不同定年方法获得的年龄或生长速率的明显差异。其中,因为大量陆源物质携带的232Th以及对Co含量的稀释,铁锰结壳表层的230Thex/232Th初始通量以及样品部分层位的Co通量出现显著变化,230Thex/232Th定年方法与Co经验公式获得的结果受到碎屑物质的影响最为显著。尽管10Be/9Be初始通量也受到了陆源物质输入的影响,但是10Be/9Be初始通量变化很小,应该是本研究中最为可信的结果。而古地磁地层学定年法需要参考其他定年结果,最后也只能得到几个年龄控制点。最终得出加瓜海脊该铁锰结壳样品的年龄为7.09 Ma,而不同核素在铁锰结壳中的赋存状态应该是今后值得深入研究的一个重要方向。Precise dating of deep-sea Fe-Mn crust is crucial to the research of paleoceanographic changes.In this paper,dating methods of 10Be/9Be,Co empirical formula,230Thex/232Th and paleomagnetic stratigraphy are comparatively used for systematical chronological studies of a Fe-Mn crust sample collected from the Gagua Ridge.Different growth rate or different age figures are observed as different dating methods are adopted due to large inputs of terrigenous materials.Co content is diluted by the excessive amounts of 232Th brought in by the terrigenous inputs,and the Co flux in certain layers and initial 230Thex/232Th flux at the surface layer are both greatly fluctuated,which will render greatly influence onto the dating results of the two methods.Although the 10Be/9Be initial flux is also influenced by terrigenous inputs,it remains relatively stable.Therefore,10Be/9Be can be regarded as the most precise dating method in the case.Paleomagnetic stratigraphy dating results may provide several age controlling points after referring to other dating results.Finally,the initial growth age of the Fe-Mn crust is confirmed as 7.09 Ma.For more precise age figure,further studies are required on the occurrence of nuclides in the Fe-Mn crust.

关 键 词：铁锰结壳 定年方法 古地磁 同位素地球化学 加瓜海脊 

分 类 号：P736.4[天文地球—海洋地质]