Origin and Evolution of the Absolute and Relative Highly Siderophile Element Abundances Present in the Early Earth

智力优势。该项目旨在约束的起源和时间演化的高度亲铁元素（HSE：Re，Os，Ir，Ru，Pt，Pd）的绝对和相对丰度在太古代地幔。这项任务对于理解基本的行星过程至关重要，包括地球的初级分化，晚期吸积和随后的化学演化。这项研究的重点是来自巴伯顿绿岩带（BGB）的超镁铁质岩浆（科马提岩），它保存了地球演化非常早期阶段的遗迹，当时地幔受到熔体提取、通过地壳再循环再施肥和核幔相互作用的影响较小。BGB科马提岩具有独特的化学成分，包括极高的MgO含量和各种LREE和HREE亏损/富集的签名，清楚地将它们与年轻的科马提岩区分开来，并暗示其岩浆生成的非常特定的条件。共CA。150化学性质良好的科马提岩全岩样品和橄榄石和铬铁矿分离的3.48 Ga Komati，3.30 Ga Weltevreden，和3.30 Ga Mendon形成的BGB将检查高精度绝对HSE丰度和186，187 Os/188 Os同位素系统。保存完好的样品，从贫铝到富铝的成分，有的已经在手上，有的将由合作者提供;更多的样品将通过国际综合开发项目巴伯顿钻探项目提供，PI是该项目的积极参与者。绝对和相对HSE丰度将估计的地幔源的三个各自的科马提岩系统在UMD。与亲石微量元素和同位素数据一起，这些HSE数据将与高精度HSE数据进行比较，用于南极陨石，原始上地幔，月球撞击熔体和太古代科马提岩系统，以评估太古代科马提岩地幔源组成的长期变化，并开发有关HSE在地幔中的起源和演化的模型。现存的假说包括[1]由于星子的持续吸积而增加HSE，[2]在岩浆海洋条件下高压金属硅酸盐平衡，[3]随后由于俯冲带环境中的质量转移和海洋岩石圈的再循环而导致的修改。该项目的推广工作将促进来自四大洲的科学家之间的合作，包括PI和Christophe Robin博士。Nick Arndt（格勒诺布尔大学）的学生，以及ICDP巴伯顿钻井项目的成员。它也将涉及UMD本科生。对这项研究的支持将有助于维持IGL的使命，在世界范围内分享和合作，特别是与那些缺乏必要的分析设施的人。由于巴伯顿地区的独特性质，它目前被提名为联合国教科文组织世界遗产。该项目将为保护和保存该地区的自然遗产的动议提供更多的科学支持。

Intellectual Merit. This project is designed to constrain the origin and temporal evolution of the absolute and relative abundances of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Pd) in the early Archean mantle. This task is crucial for understanding fundamental planetary processes including Earth's primary differentiation, late accretion, and subsequent chemical evolution. The study focuses on ultramafic magmas (komatiites) from the Barberton Greenstone Belt (BGB), which preserved relicts of the very early stages of the Earth's evolution at a time when its mantle was less modified by processes of melt extraction, re-fertilization via crustal recycling, and core-mantle interaction. The BGB komatiites have unique chemical compositions, including extremely high MgO contents and a variety of LREE- and HREE-depleted/enriched signatures that clearly distinguish them from younger komatiites and imply very specific conditions of their magma generation. A total of ca. 150 chemically well characterized komatiite whole rock samples and olivine and chromite separates from the 3.48 Ga Komati, 3.30 Ga Weltevreden, and 3.30 Ga Mendon Formations of the BGB will be examined for high-precision absolute HSE abundances and 186,187Os/188Os isotope systematics. Well-preserved samples, ranging from Al-depleted to Al-enriched compositions, either are already in hand, or will be provided by collaborators; additional samples will become available through the ICDP Barberton Drilling Project, of which the PI is an active participant. Absolute and relative HSE abundances will be estimated for the mantle sources of the three respective komatiite systems at UMd. Together with lithophile trace element and isotopic data, these HSE data will be compared with high precision HSE data for chondritic meteorites, primitive upper mantle, lunar impact melts, and Archean komatiite systems to evaluate secular variations in the composition of the Archean komatiite mantle sources, and to develop models regarding the origin and evolution of HSE in the mantle. Extant hypotheses include [1] additions of HSE as a result of continuous accretion of planetesimals, [2] high pressure metal-silicate equilibration under the magma ocean conditions, and [3] subsequent modifications resulting from mass transfer in subduction zone environments and recycling of oceanic lithosphere.Broader Impacts. Outreach efforts of this project will foster collaborations between scientists from four continents, including the PI and Christophe Robin, a Ph.D. student of Nick Arndt (Univ. Grenoble), and members of the ICDP Barberton Drilling Project. It also will involve a UMd undergraduate student. Support for this research will help sustain the IGL's mission to share and collaborate world-wide, especially with those lacking access to necessary analytical facilities. Due to the unique nature of the Barberton region, it is currently being nominated as a UNESCO World Heritage Site. This project will provide added scientific support for this motion to protect and preserve the natural heritage of the area.