Speleothem annual layers revealed by seasonal SIMS δ^(18)O measurements  

作　　者：LIU YuHui TANG GuoQiang LING XiaoXiao HU ChaoYong LI XianHua 

机构地区：[1]State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences [2]Faculty of Materials Science and Chemistry, China University of Geosciences [3]State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, China Academy of Sciences

出　　处：《Science China Earth Sciences》2015年第10期1741-1747,共7页中国科学（地球科学英文版）

基　　金：supported by the Open Project Program of State Key Laboratory of Geological Processes and Mineral Resources(Grant No.GPMR201201);National Natural Science Foundation of China(Grant No.41371216)

摘　　要：In-situ seasonalδ18O measurements of section 236.3-235.6 cm of speleothem HS4, from Qingjiang Valley of the Middle reaches of Yangtze River, China, were performed by an Secondary Ionization Mass Spectrometry （SIMS） with Oka （Chinese primary calcite standard GBW04481） and UWC-3 （international calcite standard from University of Wisconsin）. The potential of using SIMS δ18O measurements to establish speleothem time series has been explored and the differences between conventional and SIMS δ18O values have been discussed. During a 3-day period, UWC-3 δ18O has been measured on Cameca IMS δ18O Ion Microprobe Mass Spectrometer against ＂Oka＂ external standard. The measured mean value of UWC-3 （δ18OVPDB= -17.85‰±0.22‰, 1SD） matches well with its recommended value （δ18OvPDB=-17.83‰±0.08‰）, suggesting that the instrument was stable. The same method applied on HS4 produced δ18O measurements at seasonal resolution with distinct annual cycles and the total cycle number in agreement with that from Mg/Ca cycles and lamination layer counting of the same section, so it offers an alternative for accessing speleothem time series. However, compared with conventional δ18O values of HS4, SIMS δ18O values are more negative by 0.90‰ with larger seasonal variation. The main reasons might come from the mi- cro-cracks, micro-pores or liquid inclusions existing in HS4, and organic materials in the speleothem might be another factor affecting the SIMS δ18O values, indicating that to obtain reliable speleothem SIMS δ18O values, both compaction and purity of samples are crucial.In-situ seasonalδ18O measurements of section 236.3–235.6 cm of speleothem HS4,from Qingjiang Valley of the Middle reaches of Yangtze River,China,were performed by an Secondary Ionization Mass Spectrometry(SIMS)with Oka(Chinese primary calcite standard GBW04481)and UWC-3(international calcite standard from University of Wisconsin).The potential of using SIMSδ18O measurements to establish speleothem time series has been explored and the differences between conventional and SIMSδ18O values have been discussed.During a 3-day period,UWC-3δ18O has been measured on Cameca IMS1280 Ion Microprobe Mass Spectrometer against"Oka"external standard.The measured mean value of UWC-3(δ18OVPDB=?17.85‰±0.22‰,1SD)matches well with its recommended value(δ18OVPDB=?17.83‰?0.08‰),suggesting that the instrument was stable.The same method applied on HS4 producedδ18O measurements at seasonal resolution with distinct annual cycles and the total cycle number in agreement with that from Mg/Ca cycles and lamination layer counting of the same section,so it offers an alternative for accessing speleothem time series.However,compared with conventionalδ18O values of HS4,SIMSδ18O values are more negative by 0.90‰with larger seasonal variation.The main reasons might come from the micro-cracks,micro-pores or liquid inclusions existing in HS4,and organic materials in the speleothem might be another factor affecting the SIMSδ18O values,indicating that to obtain reliable speleothem SIMSδ18O values,both compaction and purity of samples are crucial.

关 键 词：SIMS Δ18O annual cycles SPELEOTHEM time series 

分 类 号：P585[天文地球—岩石学]