Mantle metasomatism and kimberlite emplacement recorded in the dissolution and reaction products on diamond and other mantle minerals

金刚石和其他地幔矿物的溶解和反应产物记录的地幔交代作用和金伯利岩侵位

• 批准号: RGPIN-2015-04650
• 负责人: Fedortchouk, Yana
• 金额: $ 1.6万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=678769
• 关键词: Mantle; metasomatism; kimberlite; emplacement; recorded

Diamond forms deep in the mantle and is carried upwards to the Earth's surface by the deepest known magma, kimberlites. Our modern knowledge of diamond internal structure and inclusions implies a complex history of interaction with melts and fluids, which percolate through the mantle beneath the continents modifying its composition. The complexity of the diamond carrier, kimberlite magma, precludes the usage of conventional methods to study kimberlites leaving their origin ambiguous. The proposed research offers a novel approach for investigating deep magmas and fluids by uncovering the record, which they leave on the surface of diamond and other mantle minerals during interaction. Experiments carried out at the conditions simulating the natural environments will explore development of surface features on diamond during dissolution. Comparing these features to those on natural diamonds will test the exiting hypotheses of the complex chemical processes in the different domains of subcontinental mantle and the hypotheses of the composition of kimberlite melt, the behavior of volatiles, and their effect on kimberlite emplacement. The proposed study will use diamonds obtained from different sections of composite kimberlite pipes. This unique opportunity to study diamond parcels with geological control is possible due to the support of my research by diamond industry. In order to derive a predictive model applicable to natural kimberlites, I am developing a quantitative method to study diamond morphology using atomic force microscopy. This approach provides three-dimensional dataset of mineral surface and allows to quantify the H2O:CO2 ratio and temperature of diamond-destructive fluids. The results of this work will complement the studies of diamond mineral inclusions and isotope systematic to resolve fundamental questions related to the origin of kimberlite magmatism, processes triggering diamond growth, and complex chemical processes modifying the subcontinental mantle. The anticipated results will establish the mechanism of diamond interaction with fluids and explain the variety of surface features observed on natural diamonds, which origin is not yet understood. The project will advance modeling of the oxidation state of the Earth's mantle, provide new robust constraints on the nature of fluids in different mantle environments, and compare the evolution of the deep continental roots beneath North America and Africa. The study will address important exploration problem of diamond preservation. Diamond dissolution may result in significant diamond loss and decrease in diamond grade. If substantial dissolution occurs in the kimberlite magma the decrease in diamond grade may not be apparent from the existing methods for diamond potential assessment. The proposed research will provide new tools for improving exploration techniques and assessment of kimberlite bodies.

钻石在地幔深处形成，并被已知最深的岩浆金伯利岩带到地球表面。我们对钻石内部结构和内含物的现代知识意味着与熔体和流体相互作用的复杂历史，熔体和流体渗透到大陆下面的地幔中，改变了其成分。钻石载体金伯利岩岩浆的复杂性，排除了使用常规方法研究金伯利岩，使其起源模糊不清。这项研究为研究深部岩浆和流体提供了一种新的方法，通过揭示它们在相互作用过程中留在金刚石和其他地幔矿物表面的记录。在模拟自然环境的条件下进行的实验将探索溶解过程中金刚石表面特征的发展。将这些特征与天然金刚石的特征进行比较，将检验有关陆下地幔不同区域复杂化学过程的现有假设，以及金伯利岩熔体成分、挥发分行为及其对金伯利岩侵位的影响的假设。拟议的研究将使用从复合金伯利岩管的不同部分获得的钻石。这个独特的机会，研究钻石包裹地质控制是可能的，由于我的研究的支持，钻石行业。为了得到一个适用于天然金伯利岩的预测模型，我正在开发一种定量的方法，使用原子力显微镜研究金刚石形态。这种方法提供了矿物表面的三维数据集，并允许量化的H2O：CO2比和温度的钻石破坏性流体。这项工作的结果将补充钻石矿物包裹体和同位素系统的研究，以解决有关金伯利岩岩浆活动的起源，触发钻石生长的过程，以及修改次大陆地幔的复杂化学过程的基本问题。预期的结果将建立金刚石与流体相互作用的机制，并解释在天然金刚石上观察到的各种表面特征，这些特征的起源尚未被理解。该项目将推进地球地幔氧化状态的建模，为不同地幔环境中流体的性质提供新的强大约束，并比较北美和非洲深层大陆根的演变。该研究将解决金刚石保存的重要勘探问题。金刚石溶解可能导致金刚石的大量损失和金刚石品位的降低。 如果金伯利岩岩浆发生大量溶解，金刚石品位的降低可能不会从现有的金刚石潜力评估方法中明显看出。拟议的研究将为改进金伯利岩体的勘探技术和评估提供新的工具。