In search for the origin of tungsten in the global komatiite-basalt systems

在过去的二十年里，技术驱动的对地球内部的研究使我们对自地球诞生以来一直在塑造地球的全球过程的理解取得了重大突破。仪器的最新进展使科学家们能够发现古代和现代岩石成分的微小变化。其中一些变化是现已灭绝的元素的放射性分解的结果。这些变化的存在直到今天表明，在地球历史的最初几千万到几亿年里，地球内部一定形成了储藏库，而且现在仍然存在。这些储层显然经受住了形成月球的巨大撞击，随后剧烈的晚期增生，以及数十亿年强烈的对流地幔混合，这表明我们的星球在早期可能并不像之前认为的那样繁荣。这一重大发现的证据来自对古代和现代岩石中钨元素微小变化的观察。然而，这些变异的起源仍然知之甚少。这项研究的目的是限制地球岩石中钨的来源。这项研究将主要集中在几十亿年前从地球内部直接取样的古代岩石中提取的矿物中钨的行为，并将它们与最近的类似岩石进行比较。该项目的工作将包括对地球内部钨变化起源的模型进行批判性评估，并评估这些解释对我们对地球历史的理解的影响。这项研究与长期争论的行星如何形成和演化的问题有关，并将提高我们对现代地球的理解。预期的科学进步的很大一部分将是本科生参与这项研究的结果，这将为他们未来的科学事业或直接过渡到劳动力市场提供必要的培训。对该项目的支持将有助于维持大学在全球范围内分享和合作的使命，特别是与缺乏最先进分析设施的研究人员。这项研究的结果将发表在同行评议的科学期刊上，在国际会议上提出，并将随时提供给更广泛的科学界进行合作研究。该研究项目旨在限制科马铁矿-玄武岩系统中钨(W)的起源，以便批判性地评估地幔中182W异常起源的模型，并通过在150个完整岩石样品中获得包括W在内的一整套微量元素的高精度丰度数据，以及主要和微量矿物相，评估这些解释对我们对地球历史的理解的影响。利用UMD最先进的分析技术，从全球15个科马铁矿-玄武岩系统中进行分析。研究目标是：(1)在选定的科马铁矿-玄武岩体系的分异过程中建立了大量微量元素的分配；(2)在保存良好和变化不明显的科马铁矿-玄武岩体系中建立了微量元素在主矿物相、微量矿物相和硅酸盐液体之间的分配；(3)量化了科马铁矿-玄武岩体系中微量元素相对丰度富集/消耗与其182W组成之间关系的矿物和化学控制。(4)区分这些系统中W的内源性和外源性起源；(5)批判性地评估之前提出的地幔182W异常起源模型；(6)评估该项目获得的解释如何影响我们对地球历史的理解。之所以选择科马马岩-玄武岩体系进行分析，是因为大多数科马马岩-玄武岩体系都有182W、142143nd、176Hf、186187os同位素和HSE丰度数据。这些系统的182W数据尚未获得，之所以选择这些系统，是因为它们的主要矿物学和化学特征保存程度最高，这将有助于总体上建立W的岩浆宿主，并作为评估保存完好的系统与变化较大的系统中W行为的比较点。本研究的一个重要成果将是建立一个关于岩浆和岩浆后过程中微量元素，特别是W在不同主微量矿物相之间分配行为的综合性新数据库。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The technology-driven research of the Earth's interior over the past two decades resulted in major breakthroughs in our understanding of the global processes that have been shaping our planet from the time it was born. Recent advances in instrumentation have allowed scientists to discover small variations in the composition of ancient and modern rocks. Some of these variations are the result of the radioactive breakdown of elements that are now extinct. The survival of these variations until present day indicate that there were and still are reservoirs in the Earth's interior which must have formed within the first few tens of millions- to hundreds of millions of years into Earth history. These reservoirs have apparently survived the giant impact that created the Moon, subsequent violent late accretion, and billions of years of vigorous convective mantle mixing, suggesting that our planet may not have been as exuberant in its early days as previously thought. Evidence for this remarkable discovery came from observation of small variations in the element tungsten in ancient and modern rocks. The origin of these variations, however, remains poorly understood. This research is aimed at constraining the source of tungsten in Earth’s rocks. The research will largely focus on the tungsten behavior in minerals from ancient rocks that directly sampled the Earth’s interior billions of years ago, and compare them to similar recent rocks. The work for this project will include critical evaluation of the models for the origin of variations of tungsten in Earth’s interior, and an assessment of the impact of these interpretations on our understanding of Earth’s history. This research has relevance to the long-debated question of how planets form and evolve, and will improve our understanding of modern Earth. A significant part of the expected scientific advances will be the result of involvement of undergraduate students in this research, which will provide necessary training crucial for their future scientific careers or as they transition directly into the workforce. Support for this project will help sustain the University's mission to share and collaborate worldwide, especially with researchers lacking access to state-of-the-art analytical facilities. The results of this research will be published in peer-reviewed scientific journals, presented at international conferences, and will be made readily available to the broader scientific community for collaborative research efforts.The proposed research project is aimed at constraining the origin of tungsten (W) in komatiite-basalt systems in order to critically evaluate the models for the origin of 182W anomalies in the mantle and assess the impact of these interpretations on our understanding of Earth's history via obtaining high-precision abundance data for a comprehensive set of trace elements, including W, in 150 whole-rock samples, as well as major and trace mineral phases, from 15 komatiite-basalt systems from around the globe, using the state-of-the-art analytical techniques available at UMD. The research objectives are to: (1) establish bulk trace element partitioning during differentiation of the selected komatiite-basalt systems, (2) establish the partitioning of trace elements between major and trace mineral phases and silicate liquid in both well-preserved and variably altered komatiite-basalt systems, (3) quantify the mineral and chemical control on the relationships between the relative trace element abundance enrichments/depletions in the komatiite-basalt systems and their 182W compositions, (4) distinguish between endogenous and exogenous origins of W in these systems, (5) critically evaluate the previously proposed models for the origin of 182W anomalies in the mantle, and (6) evaluate how the interpretations obtained as a result of this project impact our understanding of the Earth's history. The komatiite-basalt systems chosen for analysis were selected because 182W, 142,143Nd, 176Hf, 186,187Os isotope, and HSE abundance data are available for most of them. Those systems, for which 182W data are not yet available, were selected due to the highest degrees of preservation of their primary mineralogical and chemical features, which will aid in establishing magmatic hosts of W in general and serve as a point of comparison in evaluating W behavior in well-preserved versus variably altered systems. An important product of this study will be a comprehensive new database on the partitioning behavior of trace elements, particularly W, between different major and trace mineral phases during magmatic and post-magmatic processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.