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

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.

大陆地壳对于地球上生命的发展和维持至关重要。大陆地壳，特别是古代大陆地壳，生产了世界上90%的黄金和铂金矿床以及几乎所有的钻石。古代大陆地壳在今天的地球上显然是稳定的，并且通常比年轻的地壳块体具有更深的地幔根。然而，古代大陆地壳是如何形成的，也许更重要的是，是如何稳定的，仍然是地球科学中一个悬而未决的问题。该项目将利用最近发现的保存在古代沉积岩样品中的28.5亿年前的钻石，帮助解决这一问题。 钻石是对大陆深根进行取样的最佳工具，它们所含的沉积物保存了地球历史上大陆海拔和表面的记录。这些小钻石可能是地球上最古老的钻石，它们的化学特征记录了大陆地壳最早的根源是如何形成的。该项目将寻找更多有价值的大陆深层根记录，同时也调查现在发现的沉积岩。沉积岩记录了它们沉积时的表面特征，因此这种深层和表面相结合的研究将有助于解决以下问题：早期地球是海洋世界吗？大陆的根是在大陆升出海平面之前形成的吗？古代大陆在变得坚硬和稳定之前，在其生命早期是否是松散和可延展的？ 这项研究的结果将作为科学家的输入数据，帮助他们了解古代大气的组成、古代生物过程以及地球上重要的矿藏是如何形成的。 参与这一提议的研究小组最近发现了保存在大约1000年的碎屑钻石。2.85数十亿年前的沉积物在这段时间内，地球表面存在太古代钻石，其详细的地球化学特征包含了保存大陆地壳区域形成和时间综合稳定性的关键证据。该团队将评估这些古代钻石的流行程度，位置和地幔居住年龄，以及它们的地球化学特征，以测试岩石圈深部地幔根形成时间的模型及其对大规模克拉通形成的意义。该团队还将评估现在含有古代钻石的沉积物，包括其集水面积（古代流域的大小），集水年龄分布和沉积环境。这些输入将有助于了解是否在地球历史的早期形成了显著的大陆隆起，这可能是由于大陆根的稳定。本提案中的工作将利用单一样本集和专门的实地调查，解决克拉通形成和大陆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方偏远地区进行岩石取样，然后在美国和加拿大的实验室进行最先进的化学分析。 全面了解整个地球历史上大陆地壳的生命周期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地球表面的生命如何进化。这一提议还将产生大量的古代钻石收藏，可在今后的工作中加以研究。此外，古老的古陆块拥有地球上大部分经济铂、Au和钻石，使其成为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普遍性在很大程度上是未知的，因此该项目的结果可能会推动全球类似沉积物中的经济活动（勘探和资源开发）。该项目将资助一名博士的培训，该博士也将接触地球科学行业的许多部门，包括学术界，政府调查，经济勘探和采矿以及许多类型的先进分析技术。钻石研究，以及早期地球的地质，是一个受科学媒体和公众欢迎的研究课题。 该奖项反映了NSF的法定使命，通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Mesoarchean diamonds formed in thickened lithosphere, caused by slab-stacking

中太古代钻石在加厚的岩石圈中形成，由板片堆积引起

• DOI: 10.1016/j.epsl.2022.117633
• 发表时间: 2022
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Timmerman, S.;Reimink, J.R.;Vezinet, A.;Nestola, F.;Kublik, K.;Banas, A.;Stachel, T.;Stern, R.A.;Luo, Y.;Sarkar, C.
• 通讯作者: Sarkar, C.