Abstract High precision triple oxygen isotope measurements of carbonates can better constrain temperatures and oxygen isotope compositions of seawater through geologic time than 18O/16O measurements alone, but lack of a definitive calibration has hindered progress. In this study, we fluorinated both carbonate and water samples to measure quantitatively the triple oxygen isotope composition of each phase. We compared the oxygen isotope fractionation between carbonate and water for different carbonate materials: calcite synthesized with and without carbonic anhydrase, abiogenic calcite from Devils Hole, and extant biogenic calcite and aragonite of marine origin. We found similar 1000lnα18Occ-wt values for all materials and combined the results with the high temperature experimental data of O'Neil et al. (1969) , resulting in the following fractionation equation (T in Kelvins) 1000 ln α 18 O cc - w t = 2.84 ( ± 0.02 ) × 10 6 T 2 - 2.96 ( ± 0.19 ) . The calcite triple oxygen isotope values yielded a θ-T relationship of θcc-wt = –1.39(±0.01)/T + 0.5305 whereas the aragonite triple oxygen isotope values yielded a θ-T relationship of θara-wt = –1.53(±0.02)/T + 0.5305. The calcite-water triple oxygen isotope equilibrium fractionation equation for natural samples is Δ 17 ′ O cc - Δ 17 ′ O wt = 2.84 ( ± 0.02 ) × 10 6 T 2 - 2.96 ( ± 0.19 ) - 1.39 ( ± 0.01 ) T + 0.5305 - λ . The combined 1000lnα18O and 1000lnα17O relationships can be used to assess equilibrium in ancient samples and to evaluate potential secular changes in the δ18O value of seawater. Most of the Phanerozoic samples analyzed in this study, which were determined to be pristine in previous studies, have undergone some level of diagenesis. Two samples appear to preserve their original oxygen isotope compositions and suggest a cool ocean with a δ18O value similar to the modern ocean. Using a fluid-rock interaction model, we can “see through” the diagenetic process and estimate the triple oxygen isotope composition of the carbonate prior to alteration. In doing so, we show that for the time intervals and sample locations measured in this study, Phanerozoic oceans had a comparable range of oxygen isotope compositions and temperatures as modern seawater.

中文翻译：

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碳酸盐-水三氧同位素分馏的校准：看穿古代碳酸盐岩的成岩作用

摘要 与单独的 18O/16O 测量相比，碳酸盐的高精度三氧同位素测量可以更好地通过地质时间限制海水的温度和氧同位素组成，但缺乏明确的校准阻碍了进展。在这项研究中，我们对碳酸盐和水样品进行了氟化，以定量测量每个相的三氧同位素组成。我们比较了不同碳酸盐材料的碳酸盐和水之间的氧同位素分馏：使用和不使用碳酸酐酶合成的方解石、来自魔鬼洞的非生物方解石，以及现存的海洋生物方解石和文石。我们发现所有材料都有相似的 1000lnα18Occ-wt 值，并将结果与​​ O'Neil 等人的高温实验数据相结合。(1969) , 得到以下分馏方程（开尔文中的 T） 1000 ln α 18 O cc-wt = 2.84 (± 0.02 ) × 10 6 T 2 - 2.96 (± 0.19) 。方解石三氧同位素值产生 θcc-wt = –1.39(±0.01)/T + 0.5305 的 θ-T 关系，而文石三氧同位素值产生 θara-wt = –1.53(±0.02) 的 θ-T 关系)/T + 0.5305。天然样品方解石-水三氧同位素平衡分馏方程为Δ 17 ′ O cc -Δ 17 ′ O wt = 2.84 (±0.02) × 10 6 T 2 - 2.96 (±0.19) - 1.39 (±0.01) + 0.5305 - λ。组合的 1000lnα18O 和 1000lnα17O 关系可用于评估古代样品中的平衡和评估海水 δ18O 值的潜在长期变化。本研究中分析的大多数显生宙样品，在之前的研究中被确定为原始的，经历了一定程度的成岩作用。两个样本似乎保留了其原始的氧同位素组成，并表明其 δ18O 值类似于现代海洋的凉爽海洋。使用流体-岩石相互作用模型，我们可以“看穿”成岩过程，并估算出蚀变前碳酸盐的三氧同位素组成。通过这样做，我们表明，对于本研究中测量的时间间隔和样本位置，显生宙海洋的氧同位素组成和温度范围与现代海水相当。我们可以“看穿”成岩过程，并估算出蚀变前碳酸盐的三氧同位素组成。通过这样做，我们表明，对于本研究中测量的时间间隔和样本位置，显生宙海洋的氧同位素组成和温度范围与现代海水相当。我们可以“看穿”成岩过程，并估算出蚀变前碳酸盐的三氧同位素组成。通过这样做，我们表明，对于本研究中测量的时间间隔和样本位置，显生宙海洋的氧同位素组成和温度范围与现代海水相当。