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

寻找全球科马提岩-玄武岩系统中钨的起源

• 批准号: 2220936
• 负责人: Igor Puchtel
• 金额: $ 30.83万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-12-01 至 2025-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2220936&HistoricalAwards=false
• 关键词: search; origin; tungsten; global; komatiite

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.

在过去20年里，对地球内部的技术驱动的研究使我们对全球进程的理解取得了重大突破，自地球诞生以来，这些进程一直在塑造我们的星球。最近仪器设备的进步使科学家们能够发现古代和现代岩石成分的微小差异。其中一些变化是现已灭绝的元素放射性击穿的结果。这些变化直到今天的幸存表明，地球内部过去和现在仍然存在着水库，这些水库肯定是在地球历史的最初数千万年--到数亿年--内形成的。这些水库显然经受住了创造月球的巨大撞击、随后猛烈的晚期吸积，以及数十亿年来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想象的那样活跃。这一非凡发现的证据来自对古代和现代岩石中钨元素的微小变化的观察。然而，这些变异的起源仍然鲜为人知。这项研究旨在限制地球岩石中钨的来源。这项研究将主要集中在数十亿年前直接对地球内部进行采样的古老岩石中的矿物中钨的行为，并将它们与类似的现代岩石进行比较。该项目的工作将包括对钨在地球内部变化的起源模型进行批判性评估，以及评估这些解释对我们理解地球历史的影响。这项研究与行星如何形成和演化这一长期争论的问题有关，并将增进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职业生涯或在他们直接过渡到劳动力市场时提供必要的培训。对这一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，特别是在研究人员无法获得最先进的分析设施的情况下。这项研究的结果将发表在同行评议的科学期刊上，并在国际会议上发表，并将随时提供给更广泛的科学界进行合作研究。拟议的研究项目旨在限制科马提岩-玄武岩系统中钨的来源，以便批判性地评估地幔中182W异常的起源模型，并通过获得来自全球15个科马提岩-玄武岩系统的包括W在内的一系列微量元素的高精度丰度数据，评估这些解释对我们理解地球历史的影响。使用UMD提供的最先进的分析技术。研究的目的是：(1)在选定的科马提岩-玄武岩系统的分异过程中建立大量的微量元素分配；(2)在保存完好和变化不定的科马提岩-玄武岩系统中，建立微量元素在主微量矿物相和硅酸盐液体之间的分配；(3)量化科马提岩-玄武岩系统中相对微量元素丰度/亏损与其182W组成之间的关系的矿物和化学控制；(4)区分这些系统中W的内源和外源来源；(5)对以前提出的地幔182W异常成因模型进行批判性评价。以及(6)评估由于这个项目而获得的解释如何影响我们对地球历史的理解。之所以选择科马提岩-玄武岩系统进行分析，是因为大多数科马提岩-玄武岩系统都有182W、142、143Nd、176Hf、186、187Os和HSE丰度数据。那些尚未获得182W数据的系统，之所以被选中，是因为它们的原始矿物学和化学特征保存程度最高，这将有助于建立总体上W的岩浆宿主，并作为评估保存良好的系统与可变蚀变系统中W行为的比较点。这项研究的一个重要成果将是一个全面的新数据库，关于岩浆和岩浆后过程中不同主要和微量矿物相之间的微量元素，特别是W的分配行为。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。