镉同位素在古环境重建中的应用:以晚泥盆世弗拉期-法门期生物灭绝事件为例  

The Application of Cd Isotopes in the Paleo-environment Reconstruction:A Case Study of the Frasnian-Famennian Mass Extinction Event in the Late Devonian

作　　者：王伟中 张朝晖[1] 温汉捷[2,3,4] 朱传威 张羽旭[2] WANG Wei-zhong;ZHANG Zhao-hui;WEN Han-jie;ZHU Chuan-wei;ZHANG Yu-xu(Ocean College,Zhejiang University,Zhoushan Zhejiang 316021,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China;Institutions of Earth Science,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]浙江大学海洋学院,浙江舟山316021 [2]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550081 [3]中国科学院大学,北京100049 [4]中国科学院地球科学研究院,北京100029

出　　处：《矿物岩石地球化学通报》2020年第1期80-88,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国科学院战略性先导科技专项(B类)(XDB18030302);矿床地球化学国家重点实验室开放基金项目(201703);国家自然科学基金项目(41773015,41573007);贵州省科学技术基金项目(黔科合J字[2014]2162)。

摘　　要：磷(P)是海洋初级生物不可或缺的营养元素,现代海水中溶解态镉与磷的含量线性关系极好,表明镉可能作为海洋初级生物的营养元素而被利用。浮游生物优先摄取轻的镉同位素,使得海水中的镉同位素变化与海洋初级生产力的变化紧密相关。目前镉同位素已成功应用于二叠纪-三叠纪之交古海洋初级生产力的重建。广西桂林晚泥盆世弗拉期-法门期(Frasnian-Famennian,F-F)之交杨堤剖面的镉同位素数据显示,在F-F灭绝事件前,δ114Cd总体偏重(0.03‰~0.49‰),指示当时海洋具有较强的初级生产力;F-F之交,δ114Cd呈现负偏(-0.44‰^-0.01‰),表明这一时期海洋初级生产力显著下降;F-F灭绝事件后,δ114Cd又逐渐增大(-0.04‰~0.13‰),反映灭绝事件后海洋初级生产力的恢复。海洋初级生产力的下降,导致了海洋生态系统中的食物链受到破坏,从而引发了F-F之交的生物灭绝事件。Phosphorus is an essential nutrient for marine primary organisms.The excellent linear relationship between dissolved Cd and P in modern seawater indicates that Cd may be used as a nutrient element for marine primary organisms.The preference of phytoplankton to absorb light Cd isotopes makes the change of Cd isotopes in seawater closely related to the change of marine primary productivity.At present,Cd isotopes have been successfully used in the reconstruction of marine primary productivity at the turn of the Permian-Triassic periods.The Cd isotopic data of the Late Devonian Frasian-Famenian boundary(FFB)Yangdi profile in the Guilin area,Guangxi show thatδ114Cd values of carbonates below the FFB are relatively heavy in a range varying from 0.03‰to 0.49‰,indicating a relatively high marine primary productivity,then those of carbonates in the FFB are abruptly decreased to negative in a range varying from-0.44‰to-0.01‰,suggesting a rapid decline of the marine primary productivity,and finally those of carbonates above the FFB are returned to normal levels varying from-0.04‰to 0.13‰,indicating a recovery of the marine primary productivity after the F-F mass extinction event.Therefore,it is believed that the abrupt decline of marine primary productivity had resulted in the destruction of food chain in the marine ecosystem,and subsequently the FFB mass extinction event.

关 键 词：镉同位素 初级生产力 生物灭绝 晚泥盆世 弗拉期-法门期(F-F) 

分 类 号：P736.44[天文地球—海洋地质]