Temperature Effect on Stable Isotope Fractionation and Trace Element Partition in Aragonite：Inorganic Precipitation Experiments

• Main Authors: Wen-Han Wang, 王文扞
• Other Authors: Chen-Feng You
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/44639568812324151313

碩士 === 國立成功大學 === 地球科學系碩博士班 === 96 === Trace element contents or stable isotopic ratios in marine calcium carbonate are commonly used as proxies for reconstructing climatic conditions in the past ocean. Previous investigations have showed that the incorporation of trace elements into CaCO3 crystal can be influenced by various environmental factors but the major controlling mechanism is still unclear. Due to the potential complexity in the natural environment, we designed an inorganic precipitation experiment to study the relationships between trace elements and the potential impact factors, i.e., temperature, growth rate and pH. Precipitation experiments with constant pH and growth rate at five different temperatures (15 oC, 20 oC, 25 oC, 30 oC, and 35 oC) were conducted and concentrations of Li, B, Mg, Sr and Ba in solutions and carbonate precipitates were both analyzed by Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS). The isotopic ratios of Li and B were analyzed by Multi Collector Inductively Coupled plasma Mass Spectrometry (MC-ICP-MS). The results reveal that partitioning coefficients of Li, B and Mg have weak correlations with temperature, and are enriched in calcite. In contrast, Sr and Ba are enriched in aragonite. The partitioning coefficient of Ba shows a negative relationship with temperature, whereas Sr displays a minor temperature effect. B isotopic ratios are mainly controlled by temperature. On the other hand, Li isotopes fractionated differently in calcite and aragonite. The consistent results observed in the experimental specimens and the natural samples imply minor vital effect on Li isotopes in carbonate.