Clumped isotope thermometry of carbonate-bearing apatite: Revised sample pre-treatment, acid digestion, and temperature calibration
Clumped isotope thermometry of carbonate-bearing apatite: Revised sample pre-treatment, acid digestion, and temperature calibration
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DOI：
10.1016/j.chemgeo.2016.09.009
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发表时间：
2016-12
期刊：
影响因子：
3.9
通讯作者：
U. Wacker;T. Rutz;N. Löffler;A. C. Conrad;T. Tütken;M. Böttcher;J. Fiebig
中科院分区：
文献类型：
--
作者：
U. Wacker;T. Rutz;N. Löffler;A. C. Conrad;T. Tütken;M. Böttcher;J. Fiebig
最近已经表明，来自牙齿和骨骼的含碳酸盐的羟基磷灰石（HA）的聚集同位素组成（Δ47）揭示了关于脊椎动物体温的重要信息（Eagle等人，2010年、2011年）。在这项研究中，我们重新研究了Δ 47的温度依赖性，将温度范围从2 ° C扩展到59 °C。此外，还研究了化学预处理对Na 2SO 4的整体和团聚同位素组成的影响。Na 2SO 4最好在90 ~ 110 °C下与磷酸反应，以最大限度地减少释放的CO2或反应中间体在酸性环境中与痕量水重新平衡的可能性。在110 °C下的反应确保在60分钟内完成样品的数字化。结果表明，在误差范围内，文石的Δ 47 δ 90 - 110值为0.032 ± 0.008‰，而牙釉质的Δ47 δ 90- 110值为0.019 ± 0.007‰。此外，预处理的牙本质和骨材料也观察到类似的趋势：与未处理的样品相比，测得的Δ 47值较高，δ 18 O和δ 13 C值较低。其回归方程为：Δ47= 0.0320（± 0.0022）× 106/T2+ 0.1977（± 0.0259）（Δ 47以‰计，T以K计）。Henkes等人，2013; Wacker等人，2014年; Defliese和Lohmann，2015年）。在90 °C下反应的未处理的釉质（旧釉质）样品的Δ 47数据与在相同消化温度下制备的方解石的Δ47-1/T2关系密切匹配（Wacker等人，2014年）。这些初步结果表明，在90 °C的反应温度下进行的方解石校准可能直接适用于方解石样品，以确定其形成温度。
It has recently been shown that the clumped isotopic composition (Δ47) of carbonate-bearing hydroxyapatite (CHAP) from teeth and bones reveals important information about the body temperature of vertebrates (Eagle et al., 2010, 2011). In this study we reinvestigate the temperature dependence of Δ47in CHAP, extending the temperature range from 2 to 59 °C. In addition, the effects of chemical pre-treatment of CHAP on its bulk and clumped isotopic composition are studied.CHAP is best reacted with phosphoric acid at 90 to 110 °C minimizing the potential of evolved CO2or reaction intermediates to re-equilibrate with traces of water in the acid environment. Reaction at 110 °C ensures that digestions of CHAP samples are complete within 60 min. We determined a Δ47⁎90–110value of 0.032 ± 0.008‰ that is - within errors - indistinguishable from a Δ47⁎90–110value of 0.019 ± 0.007‰ received for aragonite.For tooth enamel pre-treated with H2O2lower Δ47values, and higher δ18O and δ13C values were measured than for pre-treated tooth dentine. In addition, similar trends were observed for pre-treated dentine and bone material: higher Δ47values, and lower δ18O and δ13C values were determined compared to untreated samples.A new tentative clumped isotope temperature calibration based on a synthetic apatite, untreated tooth enamel of an African elephant and enameloid from teeth of a Greenland shark is presented using a reaction temperature of 110 °C. It follows the equation:Δ47= 0.0320 (± 0.0022) × 106/T2+ 0.1977 (± 0.0259) (Δ47in ‰ and T in K).The slope of this regression line is identical to those previously obtained from 90 °C digestions of calcite and/or aragonite in several laboratories (e.g., Henkes et al., 2013; Wacker et al., 2014; Defliese and Lohmann, 2015). The Δ47data of untreated enamel(oid) samples reacted at 90 °C closely match a Δ47-1/T2relationship for calcite that was made at the same digestion temperature (Wacker et al., 2014). These preliminary results suggest that calcite calibrations made at a reaction temperature of 90 °C might be directly applicable to CHAP samples to determine their formation temperatures.