Formation of highly evolved melts on the Precambrian Earth

地球大陆地壳的长期演化以3.2至2.5 Ga之间的性质和组成的明显变化为标志（Arndt 2013; Brown et al. 2020; Nebel et al. 2018; Palin et al. 2020），这可能反映了产生该地壳的主要地质过程的变化。然而，尽管经过了数十年的集中研究，在前寒武纪地球上运作的地质过程仍然是个谜（Cawood et al. 2006; Korenaga 2013; Nebel et al. 2018）。更深入地了解太古代-元古代边界的地壳性质如何以及是什么导致了地球上地壳性质的演变，对于理解行星尺度从停滞到活动盖地球动力学机制的转变的时间和原因至关重要（Bédard 2018; Korenaga 2013; Palin等人，2020年），毫无疑问，这将有助于正在进行的旨在探索和解释我们太阳系中其他岩石天体演化的行星外任务（Wade et al. 2017）.与太古代-元古代过渡相关的是地质记录中锂-铯-钽（LCT）伟晶岩丰度的急剧增加-高度分化的长英质熔体产物，占全球锂的三分之一，几乎占世界上所有的铯和钽产量（布拉德利& Mccauley 2017）。这些关键金属对于向可持续和可再生能源过渡至关重要。例如，锂是电动汽车所需的大多数电力存储解决方案的基础，也是确保可再生能源向电网持续供应的基础（欧盟委员会，2020年）。此外，铯和钽都用于提高太阳能电池板的效率（欧盟委员会2020; Deepa等人2017）。尽管许多LCT伟晶岩的矿物学、地球化学和侵位年龄已经得到了很好的研究，但它们在其形成的岩浆岩背景下的构造-岩浆演化却知之甚少（布拉德利和麦考利2017;穆勒等人2017; Stilling等人，2006年）。在这里，我建议对太古代和元古代的岩石学进行重点研究，涉及实地和实验室工作包，其中心主题是调查地壳生长过程中如何产生高度演化的长英质熔体。这项研究将提供两个（1）在我们的社区的思想如何地球的前寒武纪大陆形成的构造体制，可能不是由俯冲，以及（2）更有针对性的研究，将解决当前和未来的社会经济问题，如通过采用清洁能源的替代来源实现碳中性社会的愿望。

The secular evolution of Earth's continental crust is marked by a distinct change in properties and composition between 3.2 and 2.5 Ga (Arndt 2013; Brown et al. 2020; Nebel et al. 2018; Palin et al. 2020), which may reflect changes in the prevailing geological processes which generated this crust. However, despite decades of focused research, the geological processes that operated on the Precambrian Earth remain enigmatic (Cawood et al. 2006; Korenaga 2013; Nebel et al. 2018). Gaining a greater understanding of how and what caused the evolution in crustal properties on Earth at the Archean-Proterozoic boundary is essential to understand the timing and cause of planetary-scale transitions form stagnant to mobile-lid geodynamic regimes (Bédard 2018; Korenaga 2013; Palin et al. 2020), and would undoubtedly aid ongoing off-planet missions that aim to explore and interpret the evolution of other rocky bodies in our solar system (Wade et al. 2017).Associated with the Archean-Proterozoic transition is the dramatic increase in abundance of lithium-cesium-tantalum (LCT) pegmatites in the geological record - highly differentiated felsic melt products that account for one-third of global Li, and almost all of the world's Cs and Ta production (Bradley & Mccauley 2017). These critical metals are vital for transitioning towards sustainable and renewable energy sources. For example, lithium is fundamental to the majority of electrical storage solutions required for electric cars and also for ensuring a consistent supply of renewable energy to the power grid (European Commission 2020). Additionally, cesium and tantalum are both used to enhance the efficiency of solar panels (European Commission 2020; Deepa et al. 2017). Whereas the mineralogy, geochemistry, and age of emplacement of many LCT pegmatites have been well studied, their tectono-magmatic evolution within the context of the cratons in which they form is poorly understood (Bradley & Mccauley 2017; Muller et al. 2017; Stilling et al. 2006).Here, I propose to conduct a petrologically focused study of Archean and Proterozoic terranes, involving both field- and lab-based work packages, which have a central theme of investigating how highly evolved felsic melt was generated during crustal growth. This research will provide both (1) far-reaching and conceptual advances in our community's thinking of how Earth's Precambrian continents formed in a tectonic regime that was likely not dominated by subduction, as well as (2) more focused research that will address current and future socio-economic problems, such as the desire to achieve a carbon-neutral society by adopting alternative sources of clean energy.