The Importance of Diagenesis upon the C, S, and B Isotopic Composition of Carbonates: Implication for Reading the Rock Record

成岩作用对碳酸盐 C、S 和 B 同位素组成的重要性：对解读岩石记录的启示

• 批准号: 1537727
• 负责人: Peter Swart
• 金额: $ 49.69万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537727&HistoricalAwards=false
• 关键词: Importance; Diagenesis; upon; Isotopic; Composition

The study of diagenesis in carbonates uses classic tools of C and O isotopes and trace elements and now there are a number of additional geochemical proxies and methods that are potentially available. The PI proposes to examine the influence of diagenetic process upon the isotopic systematics of two of these proxies, sulfur and boron, as well as take a new look at factors controlling the carbon isotopes of organic material and inorganic carbonates. This work will be carried out mainly in Plio-Pleistocene sediments using material collected by shallow water and land drilling as well as the ODP. Material will include unaltered samples as well as those affected by diagenesis involving freshwater and marine fluids. In addition to the more Modern samples, the PI will also study B within older, Neoproterozoic, sections which have been proposed by some to have both retained their original geochemistry and by others to have been influenced by diagenesis. The PI will test one of the most established criteria for determining that the carbon isotopic signals are original, rather than diagenetic, mainly the presence of a correlation between the carbon isotopes of organic and inorganic material, which has recently been questioned. The work has implications for paleoclimatic and paleoceanographic studies. Other broader impacts include graduate and undergraduate training, outreach to high school students and collaboration with the Miami-based Creative Learning and Engagement Opportunities program.The PI suggests that the study of diagenesis in carbonate rocks using geochemistry is at an exciting point. Not only have the classic tools of C and O isotopes and trace elements continued to improve in terms of their accuracy, sensitivity and microsampling ability, but there are a number of additional geochemical proxies and methods of applying these proxies potentially available. Some of these proxies need to be refined while others wait to be discovered and developed. The PI will examine the influence of diagenetic process upon the isotopic systematics of two of these, sulfur and boron, as well as take a new look at factors controlling the carbon isotopes of organic material and inorganic carbonates. This work will be carried out mainly in young carbonate sediments (Plio-Pleistocene) deposited on the flanks and surface of carbonate platforms using material collected by shallow water and land drilling as well as the ODP. Material will include supposedly unaltered samples as well as materials which have been unequivocally affected by diagenesis involving freshwater and marine fluids. The rationale for this proposal is that the isotopes of C, B, and S have already been used over a wide ranges of geological time scales to interpret changes in the Earth?s geochemical systems. Such work is being undertaken without some of the fundamental understanding of the processes which may alter these proxies. In addition to the more Modern samples, the PI will also study B within Neoproterozoic sections which have been proposed by some to have both retained their original geochemistry and by others to have been influenced by diagenesis. Finally, one of the most established criteria for determining that the carbon isotopic signals are original, rather than diagenetic, mainly the presence of a correlation between the carbon isotopes of organic and inorganic material, has recently been questioned. Hence there is a need to establish to what extent such correlations indicate that the signals are original or whether in fact the presence of a correlation indicates that diagenesis has actually occurred. The work has implications for paleoclimatic and paleoceanographic studies. Other broader impacts include graduate and undergraduate training, outreach to high school students and collaboration with the Miami-based Creative Learning and Engagement Opportunities program.

碳酸盐岩成岩作用的研究主要使用碳、氧同位素和微量元素等经典工具，现在又有一些新的地球化学指标和方法。PI建议研究成岩过程对其中两个代用指标硫和硼的同位素系统学的影响，并重新审视控制有机物质和无机碳酸盐的碳同位素的因素。这项工作将主要在上新世-更新世沉积物中进行，使用浅水和陆地钻探以及ODP收集的材料。材料将包括未改变的样品以及受淡水和海洋流体成岩作用影响的样品。除了更现代的样品外，PI还将研究更古老的新元古代剖面中的B，有些人认为这些剖面保留了原始的地球化学特征，另一些人则认为这些剖面受到了成岩作用的影响。PI将测试确定碳同位素信号是原始的而不是成岩的最成熟的标准之一，主要是有机和无机物质的碳同位素之间的相关性，最近受到质疑。这项工作对古气候学和古海洋学研究具有重要意义。其他更广泛的影响包括研究生和本科生的培训，推广到高中学生和与迈阿密的创造性学习和参与机会计划的合作。PI表明，使用地球化学的碳酸盐岩成岩作用的研究是在一个令人兴奋的点。不仅传统的碳和氧同位素和微量元素工具在准确性、灵敏度和微量取样能力方面不断改进，而且还有一些额外的地球化学代用指标和应用这些代用指标的方法。其中一些代理需要改进，而另一些则有待发现和开发。PI将研究成岩过程对其中两种硫和硼的同位素系统学的影响，并重新审视控制有机物质和无机碳酸盐的碳同位素的因素。这项工作将主要在沉积在碳酸盐台地侧面和表面的年轻碳酸盐沉积物（上新世-更新世）中进行，使用浅水和陆地钻探以及ODP收集的材料。材料将包括假定未改变的样品以及已明确受到涉及淡水和海洋流体的成岩作用影响的材料。提出这一建议的理由是，碳、B和硫的同位素已经在广泛的地质时间尺度上被用来解释地球的变化。的地球化学系统。这些工作是在没有对可能改变这些代理人的过程有一些基本了解的情况下进行的。除了更现代的样品外，PI还将研究新元古代剖面中的B，有些人认为新元古代剖面保留了原始的地球化学特征，另一些人则认为新元古代剖面受到了成岩作用的影响。最后，确定碳同位素信号是原始的，而不是成岩的最既定的标准之一，主要是有机和无机物质的碳同位素之间的相关性的存在，最近受到质疑。因此，需要确定这种相关性在多大程度上表明信号是原始的，或者相关性的存在实际上是否表明成岩作用实际上已经发生。这项工作对古气候学和古海洋学研究具有重要意义。其他更广泛的影响包括研究生和本科生培训，与高中生的外联以及与迈阿密创意学习和参与机会计划的合作。