Experimental Investigation of Mantle Heterogeneity: Behavior of Ga, Ge, and First-row Transition Elements (FRTE) During Partial Melting of Pyroxenite and Spinel Peridotite

地幔是地球质量和体积最大的一层，也是地球表面附近产生的大多数岩浆的最终来源。地球地幔中岩石的化学和矿物成分也作为时间胶囊，记录了地球形成时的事件及其随后的演变，这些演变是由近地表物质通过板块构造过程再循环回地幔造成的。该项目是对可能在地幔中发现的不同类型岩石可能产生的岩浆化学性质的实验研究。将进行高压和高温实验，以研究第一行过渡元素（FRTE; Sc-Zn元素周期表）和Ga和Ge在地幔岩浆形成过程中的行为。这些元素对于识别可能正在熔化产生岩浆的岩石类型特别有用。该项目的成果将增加关于岩浆如何在地球上形成的科学知识，并通过与天然样品的化学性质进行比较，增加我们对地球上不同岩石类型分布的了解。的内部。这项研究的更广泛的影响包括支持一个早期的职业研究人员在主要是本科院校。该项目将支持培训一名女研究生，使其获得提出科学问题、设计和进行实验、使用几种分析方法进行分析以及解释和传播实验结果方面的专门知识。该项目还将促进明尼苏达大学杜卢斯实验室与佛罗里达州立大学地球化学和宇宙化学实验室之间的合作，在那里进行分析。这项研究是一项实验研究的FRTE之间的地幔矿物和熔体的分配，这将改善地球化学工具，以确定玄武岩岩浆的源岩性。含有熔体和橄榄岩或辉石岩矿物残留物的实验将在活塞缸装置中在地幔熔体生成条件下进行（压力为1.5和3 GPa，温度为1270至1450 °C）。这些实验将掺杂FRTE和Ga和Ge。将通过激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）分析实验运行产品（淬火熔体和矿物）中这些元素的浓度。这些分析将产生每种矿物和共存熔体之间每种感兴趣元素的分配系数。该项目的目的是改善对地幔橄榄岩和辉石岩部分熔融产生的熔体中FRTE浓度和比率的限制。模型熔体组合物将产生使用这些新的实验限制和天然玄武岩的化学相比，以更好地了解如何在地幔岩性异质性的玄武岩浆的化学表示。对天然玄武岩源岩岩性的更好的限制将改善对地球上地幔再循环岩性丰度和分布的估计。

Earth's mantle is its largest layer by mass and volume and is ultimately the source of most of the magmas generated near Earth's surface. The chemistry and mineral composition of the rocks in Earth's mantle also serve as a time capsule that records events from the time of Earth's formation and its subsequent evolution caused by the recycling of near-surface materials back into the mantle through the processes of plate tectonics. This project is an experimental investigation of the chemistry of magmas that can be generated in Earth's mantle by different types of rocks that are likely to be found there. High pressure and high temperature experiments will be performed to investigate how the first-row transition elements (FRTE; Sc-Zn on the periodic table) and Ga and Ge behave during the formation of magmas in Earth's mantle. These elements are particularly useful for identify the types of rocks that may be melting to generate magmas. The results of this project will increase scientific knowledge of how magmas are formed on Earth and, through comparison with the chemistry of natural samples, will increase our understanding of the distribution of different rock types in Earth?s interior. Broader impacts of this research include support for an early-career researcher at a primarily undergraduate institution. The project will support training of a female graduate student who will gain expertise in formulating scientific questions, designing and performing experiments, analysis using several analytical methods, and interpretation and dissemination of experimental results. This project will also foster collaboration between the experimental lab at the University of Minnesota Duluth and the geochemistry and cosmochemistry lab at Florida State University, where analyses will be performed.This research is an experimental study of the partitioning of FRTE between mantle minerals and melts, which will improve geochemical tools for identifying the source lithology of basaltic magmas. Experiments containing melts and either peridotite or pyroxenite mineral residues will be performed in a piston cylinder apparatus at conditions of mantle melt generation (pressures of 1.5 and 3 GPa and temperatures from 1270 to 1450 °C). These experiments will be doped with FRTE and Ga and Ge. The concentrations of these elements in the experimental run products (quenched melts and minerals) will be analyzed by laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). These analyses will yield partition coefficients for each element of interest between each mineral and coexisting melt. The project will aim to improve constraints on the concentrations and ratios of FRTE in melts generated by partial melting of peridotite and pyroxenite in Earth's mantle. Model melt compositions will be generated using these new experimental constraints and compared with the chemistry of natural basalts to better understand how lithological heterogeneity in the mantle is expressed in the chemistry of basaltic magmas. Better constraints on the source lithology of natural basalts will improve estimates of the abundance and distribution of recycled lithologies in Earth's upper mantle.