Characteristics of strontium isotopes and their implications in the Qixing Cave of Guizhou, China  

作　　者：ZHU XiaoLong WANG ShiJie LUO WeiJun 

机构地区：[1]State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550002,China [2]Graduate University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Science Bulletin》2011年第7期670-675,共6页

基　　金：supported by the Orientation Project of Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-306);the International Partnership Project of the Chinese Academy of Sciences, the National Basic Research Program of China (2006CB403200);the National Natural Science Foundation of China (90202003);the Personnel Training Project (Western Doctor) of West Light Foundation of the Chinese Academy of Sciences

摘　　要：The strontium isotopic compositions (87Sr/86Sr) of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave (QXC), Guizhou Province, China, were systemically measured and analyzed. The results indicate that there are significant Sr isotopic differences among samples. The mean 87Sr/86Sr ratios in drip water for the samples 1#, 4# and 9# were 0.709568, 0.709139 and 0.708761, respectively, which possibly result from different flow paths, residence times, and other hydrogeological processes in the unsaturated zone overlying QXC. Meanwhile, levels of 40.8%, 57.6% and 72.4% of Sr in drip waters for 1#, 4# and 9#, respectively, were derived from bedrock dissolution, which was calculated by the mixture model of the two end-members (soil and bedrock). There is, however, no positive correlation between the relative proportion from bedrock dissolution (δ13C value is 1.8‰) and drip water δ13CDIC values. The mean drip water δ13CDIC value in 1# is the heaviest (–4.5‰) with the lowest contribution rate of bedrock dissolution, whereas the value in 9# is the lightest (–9.3‰) with the highest contribution rate of bedrock dissolution. The proportion from host rock dissolution in 4# is higher than that in 1# and lower than that in 9#, while its mean drip water δ13CDIC value (–8.6‰) is higher than that of 9# and lower than that for 1#. This suggests that the prior calcite precipitation (PCP) processes in the unsaturated zone overlying the cave are responsible for the δ13CDIC value differences between different drip waters, and not bedrock dissolution. Furthermore, this study also demonstrates that the 87Sr/86Sr ratios of speleothems in the 1# and 4# mainly reflect the variation in the relative proportions from the soil system (soil water) and bedrock dissolution overlying the cave. It is, therefore, feasible to use the strontium isotopic signals of speleothems as an indicator for soil chemical weathering intensity, and consequently as a monsoon proxy in the sThe strontium isotopic compositions （^87Sr/^86Sr） of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave （QXC）, Guizhou Province, China, were systemically measured and analyzed. The results indicate that there are significant Sr isotopic differences among samples. The mean ^87Sr/^86Sr ratios in drip water for the samples 1#, 4# and 9# were 0.709568, 0.709139 and 0.708761, respectively, which possibly result from different flow paths, residence times, and other hydrogeological processes in the unsaturated zone overlying QXC. Meanwhile, levels of 40.8%, 57.6% and 72.4% of Sr in drip waters for 1#, 4# and 9#, respectively, were derived from bedrock dissolution, which was calculated by the mixture model of the two end-members （soil and bedrock）. There is, however, no positive correlation between the relative proportion from bedrock dissolution δ13C value is 1.8%o） and drip water δ13C_DIC values. The mean drip water δ13C_DIC value in 1# is the heaviest （4.5%0） with the lowest contribution rate of bedrock dissolution, whereas the value in 9# is the lightest （-9.3%0） with the highest contribution rate of bedrock dissolution. The proportion from host rock dissolution in 4# is higher than that in 1# and lower than that in 9#, while its mean drip water δ13C_DIC value （-8.6‰） is higher than that of 9# and lower than that for 1#. This suggests that the prior calcite precipitation （PCP） processes in the unsaturated zone overlying the cave are responsible for the δ13C_DIC value differences between different drip Waters, and not bedrock dissolution. Furthermore, this study also demonstrates that the ^87Sr/^86Sr ratios of speleothems in the 1# and 4# mainly reflect the variation in the relative proportions from the soil system （soil water） and bedrock dissolution overlying the cave. It is, therefore, feasible to use the strontium isotopic signals of speleothems as an indicator for soil chemical weathering intensity, and consequ

关 键 词：锶同位素 同位素特征 贵州省 中国 洞穴堆积物 同位素组成 流动路径 停留时间 

分 类 号：P597[天文地球—地球化学] P618.510.4[天文地球—地质学]