海洋钙同位素分馏机制及其古海洋学应用

钙在海洋中是离子浓度仅次于钠和镁的金属元素,在海洋生物过程及矿物形成中都占据重要的地位。随着同位素分析仪器精度的提高,钙同位素等非常规稳定同位素的研究逐渐成为地球化学的热门,钙同位素在海洋环境中的分馏机制及其在古海洋学中的应用研究不断完善。系统介绍了钙同位素高精度分析的方法和原理,海洋环境中无机成因和有机成因2种钙同位素分馏的机制和应用;通过大量的文献调研综述了钙同位素地球化学研究在古海洋参数恢复上的应用。通过有孔虫Globigerinoides sacculifer的钙同位素具有对温度敏感、温感公式简单、后生成岩作用对其影响小和分析材料完整易得等优点,并同其他传统地质温度计联用,为古海洋研究提供精确的海洋表面温度(Sea Surface Temperature,SST);利用钙同位素值温度相关性较小的钙质壳体来恢复古海洋钙通量;利用无机成因碳酸盐岩盖帽的钙同位素恢复海水CO2-3浓度和研究甲烷渗漏对古海洋环境的影响。

Fractionation Mechanism and Paleoceanographic Applications of Calcium Isotopes in Marine Settings

The concentration of calcium is only below sodium and magnesium among metalions, which plays a crucial role in biological processes and the formation of minerals. As analytic accuracy has been increasing, studies of calcium isotopes now become hot focus. Fractionation mechanism and paleoceanographic applications of calcium isotopes in marine settings are perfected with time. Globigerinoides sacculifer is the most promising proxy allied with other proxies of sea surface temperature because its calcium fractionation being sensitive to temperature, with simple formulas and resistant to diagenesis and it is also accessible to test. Those who are not sensitive to temperature in fractionation can be used to recover calcium budget. Inorganic calcium carbonates are promising to evaluate the influences that seepage of methane may exert on paleo-climate.