Dual clumped isotope thermometry of carbonates: resolving the effects of temperature from kinetics and diagenesis for accurate reconstruction of Earth’s surface temperature

我们的星球是如何以及为什么变得适合居住的？什么样的边界条件引发了地球上生命的进化？气候将如何演变，如何影响生物多样性？为了找到这些重要问题的答案，必须重建过去大气温室气体丰度、地球表面温度和生物多样性之间的相互作用。地球表面的温度是根据年代久远的沉积物档案中的化学和同位素代用数据重建的。然而，目前还没有明确记录地球表面温度的代用品。除了温度，动力学和成岩过程以及化学和同位素组成的母流体施加控制的代理组成的沉积档案。非排他性的温度控制和原始代用成分的二次改变在重建温度中引入了很大的不确定性。我的研究小组最近开创了碳酸盐的双聚集同位素分析，即，对CO2中稀有分子12 C18 O 18 O（Δ48）的丰度进行极具挑战性的分析是从碳酸盐的磷酸消化沿着13 C18 O 16 O（Δ47）中得出的。现在，第一次，双块同位素测温法，可以让我们解决温度的动力学和成岩信息，只是从一个单一的碳酸盐相的分析，而不需要任何进一步的知识，从碳酸盐结晶的流体的组成。它有可能成为重建精确地层温度（不受动力学影响）的首选方法，具有前所未有的精度（在95%置信区间水平上< ±2°C）。我请求资助，以系统和全面地研究Δ47与Δ48空间中碳酸盐（生物）矿化的基本热力学和动力学系统学。这可能使我们能够可靠地重建过去高pCO 2间隔的地球表面温度和温室气体丰度之间的相互作用。提供准确的古纬度温度梯度的时期与pCO 2高预测将在不久的将来遇到的是必要的，以改善国家的最先进的模型预测未来的气候。此外，基础热力学和动力学的探索将提供信息的进一步潜在应用的双聚集同位素代理。这些包括埋藏和岩石隆起的温度-时间路径的重建，海洋生物生产的演变，碳酸盐生物矿化对人为CO2强迫的响应，以及自太古代以来地球表面温度和可居住性的演变。

How and why did our planet become habitable? Which boundary conditions triggered the evolution of life on Earth? How will climate evolve and how will it affect biodiversity? To find answers for these important questions it is essential to reconstruct the past interplay between atmospheric greenhouse gas abundances, Earth’s surface temperatures and biodiversity. Earth’s surface temperatures are reconstructed from chemical and isotopic proxy data from well-dated sedimentary archives. Yet, there is no proxy available that unambiguously records Earth’s surface temperature. Besides temperature, kinetic and diagenetic processes as well as the chemical and isotopic composition of the parent fluid exert control on the proxy composition of the sedimentary archive. Non-exclusive temperature control and secondary alteration of the original proxy composition introduce large uncertainties in reconstructed temperatures.My research group has most recently pioneered dual clumped isotope analysis of carbonates, i.e., the extremely challenging analysis of the abundance of rare molecules of 12C18O18O (Δ48) in CO2 evolved from phosphoric acid digestion of carbonates along with 13C18O16O (Δ47). Now, for the first time, dual clumped isotope thermometry, may allow us to resolve temperature from the kinetic and diagenetic information just from the analysis of a single carbonate phase, without requiring any further knowledge about the composition of the fluid from which the carbonate crystallized. It has the potential to become the method of choice for the reconstruction of accurate formation temperatures (unbiased by kinetics) with unprecedented precision (< ±2°C on the 95% confidence interval level).I request funding to systematically und comprehensively investigate the fundamental thermodynamic and kinetic systematics of carbonate (bio)mineralization in Δ47 vs. Δ48 space. This may allow us to reliably reconstruct the interplay between Earth’s surface temperature and greenhouse gas abundance for past high-pCO2 intervals. The provision of accurate paleo-latitudinal temperature gradients for epochs with pCO2 as high as predicted to be encountered in the near future is necessary to improve state-of-the-art models predicting future climate. Moreover, the exploration of fundamental thermodynamics and kinetics will provide information essential for further potential applications of the dual clumped isotope proxy. These include reconstructions of temperature-time paths of burial and uplift of rocks, the evolution of marine biological production, the response of carbonate biomineralization to anthropogenic CO2 forcing and the evolution of Earth’s surface temperature and habitability since the Archean.