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CAREER:Exploring the early Earth with high-resolution paleomagnetism

职业：用高分辨率古地磁学探索早期地球

基本信息

批准号：
1847042
负责人：
Roger Fu
金额：
$ 63.1万
依托单位：
Harvard University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-03-01 至 2025-02-28
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1847042&HistoricalAwards=false
关键词：
CAREER Exploring early Earth resolution

项目摘要

Conditions on the Earth during the first two billion years of its history (4.5 to 2.5 billion years before present) were vastly different from the modern Earth. Key events in Earth history, including the rise of life and the creation of continents, took place during this time, yet fundamental questions remain unanswered. Did the early Earth exhibit the familiar patterns of continental drift as we see today? When did the first oxygen-producing organisms evolve? Did a global magnetic field similar to that of the present-day isolate the atmosphere from loss to the solar wind? This project will use a new generation magnetic field imaging device, recently developed from advances in quantum sensing, to examine the magnetic properties of rock samples between 2.7 and 4.2 billion years in age. These experiments are expected to yield new insights into the initiation of plate tectonics, the evolution of the early atmosphere, and the rise of oxygen-producing life. In parallel with these measurements this project will develop a series of lessons with Boston-area middle school teachers involving student-led observations of the sun through solar telescopes distributed to the schools. These observations will serve as an introduction to changes in the sun's properties through time and its impact on surface conditions on the early Earth.The fundamental challenge to understanding conditions on Earth during the Archean Eon (4.0-2.5 billion years ago, or Ga) is the lack of well-preserved rocks dating from that time. Consequently, attempts to recover information about ancient magnetic fields have been severely hampered by pervasive remagnetization through metamorphism and chemical alteration of ferromagnetic phases. This project will apply a recently developed technology for micrometer-scale magnetic imaging, known as the quantum diamond microscope (QDM), to address major outstanding questions in Archean Earth history. The high spatial resolution of the QDM permits direct imaging of remanent magnetization carriers in complex, altered rocks, which aids the identification of primary paleomagnetic signals. In Task 1, the QDM will be used to infer the existence of the geodynamo before 3.5 Ga by recovering magnetic signals from a newly discovered population of 3.3-4.2 Ga zircons from the Barberton Greenstone Belt (BGB) of South Africa. As part of Task 2, the project team will apply both QDM and traditional paleomagnetic techniques on carefully selected igneous rock units to quantify the mobility of lithospheric plate at 3.45 Ga. Finally, Task 3 of the project will use the QDM to infer the origin of ferromagnetic iron oxides preserved in 2.78 Ga micrometeorites, thereby testing the controversial hypothesis that the upper atmosphere of the Earth was oxygen-rich several hundred million years before the Great Oxidation Event.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.

在地球历史的前20亿年（距今45亿至25亿年），地球上的条件与现代地球大不相同。地球历史上的关键事件，包括生命的兴起和大陆的创造，都发生在这段时间，但基本问题仍然没有答案。早期地球是否表现出我们今天所看到的大陆漂移模式？第一个产生氧气的生物是什么时候进化的？是否有一个类似于今天的全球磁场使大气层免受太阳风的损失？该项目将使用新一代磁场成像设备，最近从量子传感的进步中开发出来，以检查年龄在27亿至42亿年之间的岩石样本的磁性。这些实验有望对板块构造的起源、早期大气的演化以及产氧生命的兴起产生新的见解。在进行这些测量的同时，该项目还将与波士顿地区的中学教师一起开设一系列课程，包括由学生主导通过分发给学校的太阳望远镜观察太阳。这些观测结果将介绍太阳性质随时间的变化及其对早期地球表面状况的影响。了解太古宙（40 - 25亿年前，或Ga）地球状况的根本挑战是缺乏可以追溯到那个时候的保存完好的岩石。因此，试图恢复有关古代磁场的信息已经严重阻碍了普遍的再磁化通过变质和化学蚀变的铁磁相。该项目将应用最近开发的称为量子金刚石显微镜（QDM）的微米级磁成像技术，以解决太古代地球历史中的重大未决问题。 QDM的高空间分辨率允许在复杂的蚀变岩石中直接成像反射磁化载体，这有助于识别原始古地磁信号。在任务1中，QDM将被用来推断地球发电机的存在之前，3.5 Ga恢复磁信号从一个新发现的人口3.3-4.2 Ga锆石从南非的巴伯顿绿岩带（BGB）。作为任务2的一部分，项目组将在精心挑选的火成岩单元上应用QDM和传统的古地磁技术，以量化3.45 Ga时岩石圈板块的活动性。最后，该项目的任务3将使用QDM来推断保存在2.78 Ga微陨石中的铁磁性氧化铁的起源，从而验证了一个有争议的假设，即地球的上层大气是氧气，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，更广泛的影响审查标准。