Hydrothermal activities and seawater acidification in the Late Devonian F-F transition:Evidence from geochemistry of rare earth elements  

作　　者：ZENG JianWei XU Ran GONG YiMing 

机构地区：[1]Key Laboratory of Biogeology and Environmental Geology of Ministry of Education & State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China [2]Institute of Resources and Environment, Key Laboratory of Biogenic Traces & Sedimentary Minerals of Henan Province, Henan Polytechnic University, Jiaozuo 454003, China

出　　处：《Science China Earth Sciences》2011年第4期540-549,共10页中国科学（地球科学英文版）

基　　金：supported by Natural Science Foundation of China(Grant Nos.40730209,40802005,40872001,40921062);the"111" Project(Grant No.B08030);the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources

摘　　要：Rare-earth dements （REE） in limestones were measured by ICP-MS from the Yangdi section across the Frasnian-Famennian （F-F） transition in Guilin, Guangxi of South China. The average EREE contents of measured samples are 33.32 ppm. The average LREE/HREE ratio is 6.35. Data show LREE-enriched REE distribution pattern in the Yangdi section. Most of samples are characterized by positive Eu anomaly with average of 1.13, and there are two maxima of Eu anomaly just below the F-F boundary. Almost all analytical samples show obvious tetrad effects. Remarkable M-shaped tetrad effects are observed in these samples with positive Eu anomaly. The characters of REE and some relative elements （Fe, Mn, Al, etc.） indicate that hydro- thermal activities occurred and resulted in seawater acidification in Upper and Lower Kellwasser horizons of the Late Devonian. The changes of marine environment caused by hydrothermal activities, such as seawater acidification, heavy metal pollution, and eutrophication, would destroy the neritic ecosystem and finally result in the F-F mass extinction.Rare-earth elements(REE) in limestones were measured by ICP-MS from the Yangdi section across the Frasnian-Famennian(F-F) transition in Guilin,Guangxi of South China.The averageΣREE contents of measured samples are 33.32 ppm.The average LREE/HREE ratio is 6.35.Data show LREE-enriched REE distribution pattern in the Yangdi section.Most of samples are characterized by positive Eu anomaly with average of 1.13,and there are two maxima of Eu anomaly just below the F-F boundary.Almost all analytical samples show obvious tetrad effects.Remarkable M-shaped tetrad effects are observed in these samples with positive Eu anomaly.The characters of REE and some relative elements(Fe,Mn,Al,etc.) indicate that hydrothermal activities occurred and resulted in seawater acidification in Upper and Lower Kellwasser horizons of the Late Devonian.The changes of marine environment caused by hydrothermal activities,such as seawater acidification,heavy metal pollution,and eutrophication,would destroy the neritic ecosystem and finally result in the F-F mass extinction.

关 键 词：DEVONIAN mass extinction REE hydrothermal activities tetrad effects seawater acidification 

分 类 号：P618.51[天文地球—矿床学] P534.44[天文地球—地质学]