Mesoarchean diamond-bearing sediments: implications for Archean continental roots and their surface expression

中太古代含金刚石沉积物：对太古代大陆根及其表面表达的影响

• 批准号: 2118161
• 负责人: Jesse Reimink
• 金额: $ 38.57万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2118161&HistoricalAwards=false
• 关键词: Mesoarchean; diamond; bearing; sediments; implications; Mesoarchean; diamond; bearing; sediments; implications

The continental crust is fundamental to the development and sustainment of life on Earth. Continental crust, and in particular ancient continental crust, produces 90% of the world’s gold and platinum deposits and nearly all of the mined diamonds. Ancient continental crust is clearly stable on Earth today and often has a much deeper mantle root than younger crustal blocks. Yet, how ancient continental crust formed and, perhaps more importantly, was stabilized, remains an outstanding question in the Geosciences. This project will help to address this question by making use of recent discoveries of 2.85 billion-year-old diamonds preserved in ancient sedimentary rock samples. Diamonds are the best available tools to sample the deep roots of continents, and the sediments they are contained within preserve a record of the elevation and surface of the continents back in Earth history. These small diamonds are likely some of the oldest diamonds on Earth, and their chemical signatures record how the earliest roots of the continental crust formed. This project will look for more of these valuable records of the deep continental root, while also investigating the sedimentary rocks where they are now found. Sedimentary rocks record the surface features at the time they were deposited, so this combined deep-and-surface study will help address questions such as: Was the early Earth an ocean world? Did the roots of continents form first before continents rose above sea level? Were ancient continents loose and malleable early in their life before they became rigid and stable? The outputs of this research will serve as input data for scientists trying to understand the composition of the ancient atmosphere, ancient biological processes, and how important mineral deposits were formed on Earth. The research team involved in this proposal recently discovered detrital diamonds preserved in ca. 2.85 billion-year-old sediments in the Canadian shield. The presence of Archean diamonds at Earth’s surface during this time interval, and their detailed geochemical signatures, contain key evidence for the formation and time-integrated stability of regions of preserved continental crust. The team will evaluate the prevalence, location, and mantle-residence ages of these ancient diamonds, as well as their geochemical signatures to test models for the timing of the formation deep lithospheric mantle roots and their significance for large scale craton formation. The team will also evaluate the sediments that now contain the ancient diamonds including their catchment size (size of the ancient watershed), catchment age distributions, and the depositional environment. These inputs will help understand if significant continental elevation was formed in the very early in Earth history, potentially due to continental root stabilization. The work in this proposal will address two major aspects of craton formation and continental stability, using a single sample set and a dedicated field campaign. The research team will use float planes to sample rocks in the remote regions of Northern Canada and will then conduct state-of-the-art chemical analyses in laboratories in the US and Canada. A full understanding of the life cycle of continental crust throughout Earth history has broad scientific implications for the geoscience community, including helping to understand how the atmosphere became rich in oxygen and how life evolved on the surface of the Earth. This proposal will also result in a large collection of ancient diamonds which can be studied in future work. Additionally, ancient cratonic blocks host a large fraction of Earths economic Pt, Au, and diamonds making them economically important geologic features. Importantly, the prevalence of detrital diamonds in ancient sediments is largely unknown, such that the results of this project may drive economic activities (exploration and resource development) in similar sediments globally. This project will fund training of a PhD who will also be exposed to many sections of the geoscience industry, including academia, governmental surveys, and economic exploration and mining as well as many types of advanced analytical techniques. Diamond research, as well as the geology of the early Earth, is a research topic that is popular with the science media and general public. Every effort will be made to engage with the popular science media to expand the influence and public engagement with the results of this project.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.

大陆地壳是地球上生命的发展和维持的基础。大陆壳，尤其是古代大陆壳，生产了90％的世界黄金和铂金沉积物以及几乎所有采矿的钻石。当今的古代大陆壳显然在地球上显然是稳定的，并且通常比年轻的地壳块具有更深的地幔根。然而，古代大陆壳的形成是如何形成的，也许更重要的是稳定，在地球科学中仍然是一个杰出的问题。该项目将利用最近在古代沉积岩石样品中保存的28.5亿年历史的钻石来帮助解决这个问题。钻石是采样最深根的最佳工具，它们包含在地球历史上延续的海拔和表面的记录中。这些小钻石可能是地球上一些最古老的钻石，它们的化学特征记录了大陆壳的最早根源是如何形成的。该项目将寻找更多这些深色大陆根的宝贵记录，同时还调查了现在发现的沉积岩石。沉积岩石记录了它们在沉积时的表面特征，因此，这项结合的深层研究将有助于解决以下问题：早期地球是海洋世界吗？在继续升起海平面之前，大陆的根部是否首先形成？古代大陆在他们变得僵化和稳定之前的生命早期是否松散且可延展？这项研究的输出将作为试图了解古代气氛，古代生物学过程以及地球上矿物质的重要性的科学家的投入数据。参与该提案的研究小组最近发现了加利福尼亚州保存的碎屑钻石。加拿大盾牌中有28.5亿年历史的沉积物。在此时间间隔内，地球表面的存在及其详细的地球化学特征，其中包含了保留连续壳区域区域的形成和时间集成稳定性的关键证据。该团队将评估这些古代钻石的流行，位置和地幔居民年龄，以及它们的地球化学特征，以测试模型的地层深层岩石圈地幔根部的时机及其对大型Craton形成的重要性。还评估现在包含古老钻石的沉积物，包括其集水区的大小（古老的流域的大小），流域年龄分布和沉积环境。这些投入将有助于了解地球历史早期是否形成了显着的连续升高，这可能是由于连续的根稳定。该提案中的工作将使用单个样本集和专门的现场活动介绍Craten形成和连续稳定性的两个主要方面。研究小组将使用浮动飞机在加拿大北部的偏远地区采样岩石，然后在美国和加拿大实验室进行最先进的化学分析。对整个地球历史上连续地壳的生命周期的充分理解对地球科学界具有广泛的科学意义，包括帮助了解大气如何富含氧气以及生命如何在地球表面演变。还将导致大量的古代钻石，这些钻石可以在以后的工作中进行研究。此外，古老的克拉通块拥有大量的地球经济PT，AU和钻石，使它们在经济上重要的地质特征。重要的是，古代沉积物中碎屑钻石的流行率在很大程度上是未知的，因此该项目的结果可能会在全球类似的沉积物中推动经济活动（探索和资源开发）。该项目将资助博士学位的培训，该博士还将接触到地球科学行业的许多部分，包括学术界，政府调查以及经济探索和采矿以及许多类型的高级分析技术。钻石研究以及地球早期的地质学是一个研究主题，在科学媒体和公众中很受欢迎。将尽一切努力与流行的科学媒体互动，以扩大该项目结果的影响力和公众参与。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，通过评估诚实地认为支持了支持。