What is dolomite telling us about ancient seawater chemistry

白云石告诉我们有关古代海水化学的什么信息

• 批准号: 2592953
• 金额: --
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2592953
• 关键词: What; dolomite; telling; us; about

Modern environments that produce ordered dolomite on Earth today all share a key set of physical and chemical characteristics. At the same time, recent advances in our understanding of carbonate mineralisation indicate that specific chemical fluctuations are crucial in driving the precipitation of high-Mg carbonates. As a consequence, there is a unique opportunity to test key hypotheses related to the mechanisms of Mg-rich carbonate precipitation that reconcile available constraints on both the modern and ancient distributions of dolomite. This project will examine the mechanisms of high-Mg carbonate precipitation (including dolomite) by combining experimental geochemistry, the environmental geochemistry of modern hyper-saline systems, high-resolution microstructural investigations of modern and ancient dolomite-rich sediments, and numerical modeling.This project provides an opportunity to combine field work in modern hyper-saline systems and/or well-preserved Precambrian dolomitic successions, experimental geochemistry, advanced geochemical and mineralogical analysis, and theoretical geochemistry. There is scope for these elements to be tailored somewhat to the student's interests. A key component will involve collecting (either through targeted field work or sample acquisition from collaborators) a wide range of early diagenetic and authigenic dolomitic samples that represent a broad spectrum of modern and paleo-environments. The student will also design and implement a targeted program of experimentation that deconstructs the key processes generating high-Mg carbonates and modifies their crystal chemistry and structure. In addition, the signatures of these mechanisms in synthetic, modern and ancient samples using a combination of EPMA, XRD, micro-Raman spectroscopy, solid state NMR, synchrotron-micro XRF and XANES, and high-resolution TEM. Finally, there is an opportunity to explore the biogeochemical significance to modern and ancient systems through geochemical modeling and dynamical simulations (box modeling).

今天地球上生产有序白云石的现代环境都具有一套关键的物理和化学特征。与此同时，我们对碳酸盐矿化的最新了解表明，特定的化学波动在驱动高镁碳酸盐沉淀方面至关重要。因此，有一个独特的机会，以测试有关的机制，镁丰富的碳酸盐沉淀，调和现有的限制现代和古代的分布白云石的关键假设。本计画将探讨高镁碳酸盐沉淀的机制通过结合实验地球化学、现代高盐系统的环境地球化学、现代和古代富镁铁质沉积物的高分辨率显微结构调查以及数值模拟，研究了现代高盐系统和/或保存完好的前寒武纪镁铁质岩系的地质特征（包括白云石）。实验地球化学、高级地球化学和矿物学分析以及理论地球化学。这些内容可以根据学生的兴趣进行调整。一个关键组成部分将涉及收集（通过有针对性的实地工作或从合作者处获取样品）代表广泛的现代和古环境的各种早期成岩和自生磷灰石样品。学生还将设计和实施有针对性的实验计划，解构产生高镁碳酸盐的关键过程，并修改其晶体化学和结构。此外，使用EPMA，XRD，显微拉曼光谱，固态NMR，同步加速器显微XRF和XANES以及高分辨率TEM的组合，在合成，现代和古代样品中这些机制的签名。最后，有机会通过地球化学模拟和动力学模拟（箱模型）探索现代和古代系统的地球化学意义。