CAREER: Is Continental Crust Juvenile or Reworked? A Test of Growth Models Using the Extant Neoarchean Granitoid Record

职业：大陆地壳是年轻的还是经过改造的？

• 批准号: 2145334
• 负责人: Jesse Reimink
• 金额: $ 90.32万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2145334&HistoricalAwards=false
• 关键词: CAREER; Continental; Crust; Juvenile; Reworked

There currently exist more geological samples from the Moon than from our own planet during the first 500 million years of the Solar System. This dearth of samples has led to vigorous debate amongst the geological community regarding three very important aspects of Earth evolution: 1) when, 2) how, and 3) to what extent did continents emerge on the early Earth. Recent advances in technical capabilities now allow these questions to be revisited. Earth is a tectonically active planet, which means that old rocks are constantly being altered, leaving few pristine samples from the earliest phases of Earth history. By looking for very small, but important isotopic signatures in preserved rock samples, one may infer how much continental crust was around very early in Earth history. This project will fund advanced isotopic analyses of ~2.6-billion-year-old rocks in a search of evidence for great than 4.0-billion-year-old continental material, material that may have been reworked during later tectonic events. Collection of this data will allow the research team to test the hypothesis that very large volumes of ancient continental crust existed on the early Earth and to answer a fundamental question about planetary formation and evolution – when did continental crust form on Earth? This project will also support an undergraduate field research experience, which will serve to train the next generation of geoscientists in skills that employers are keenly interested in – field geology and spatial reasoning skills.This proposal will combine petrology and isotope geochemistry to test broad hypotheses regarding the growth and reworking of continental crust. Neoarchean granitoid rocks represent some of the oldest well-preserved suites of rocks on Earth. Detailed analysis of samples will address the fundamental question of when continental crust formed on Earth. This proposal will analyze suites of granitoids from three distinct North American cratons for their igneous chemical signatures. Zircon age and isotopic information (U-Pb-Hf-O) will be measured from several compositional groups to test the fidelity of commonly used tracers for crustal melting and overprinting. Analyses of xenocrystic zircons and bulk rock Nd-isotope ratios will be used to search for reworking of truly ancient (4.0 Ga) crust in the Neoarchean—a time that has been suggested to have experienced broad overprinting of the continental record. The research team focus on 142Nd analyses as these data are particularly adept at identifying Hadean crustal relics. This proposal will fund an REU field experience aimed at developing a diverse and strategically important workforce with training in field geology and spatial reasoning. The maps created and samples collected by undergraduate researchers will be used for advanced isotopic analyses conducted during the scientific study, and undergraduate participants will not only gain important—and in-demand—skills in spatially-focused critical thinking but will also be exposed to advanced geochemical techniques and datasets. These participants will finish their undergraduate experience well positioned to pursue many types of careers in the geosciences.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.

目前，在太阳系的前5亿年中，来自月球的地质样本比我们自己的星球的地质样本更多。样本的死亡导致地质社区中关于地球进化的三个非常重要方面的辩论：1）何时，2）如何和3）在地球早期继续出现了多大程度的程度。现在，技术能力的最新进展可以重新审视这些问题。地球是一个具有构造活跃的行星，这意味着旧岩石正在不断变化，从地球历史最早的阶段中几乎没有原始样本。通过在保存的岩石样品中寻找非常小但重要的同位素特征，人们可以确定地球历史早期的连续地壳是多少。该项目将资助约26亿块岩石的高级同位素分析，以寻找大量超过4000亿年历史的连续材料的证据，这些材料可能在以后的构造事件中已重新设计。这些数据的收集将使研究团队能够检验以下假设：地球早期存在大量的古代连续性地壳，并回答有关行星形成和进化的基本问题 - 地球上连续地壳何时形成？该项目还将支持本科实地研究经验，该研究将在雇主敏锐感兴趣的技能方面培训下一代的地球科学家 - 现场地质学和空间推理技能。该提案将结合质学和同位素地球化学，以测试有关连续甲壳的增长和重新工作的广泛假设。新体系花纹岩石代表了地球上最古老的岩石套件。样品的详细分析将解决地球上连续地壳何时形成的基本问题。该提案将分析来自三个不同北美克拉通的花岗岩的套件，因为它们的火成岩化学特征。锆石的年龄和同位素信息（U-PB-HF-O）将从几个复合基团测量，以测试常用的示踪剂的忠诚度，以实现地壳融化和过度打印。对异晶锆石和散装岩石ND同位素比的分析将用于寻找在Neoarchian中真正古老的（4.0 GA）地壳的重制（这是一个建议的时间，建议经历了持续的记录的广泛过分打印。研究小组重点关注第142个分析，因为这些数据特别擅长识别Hadean Crustal文物。该提案将资助REU现场经验，旨在通过领域地质和空间推理进行培训来发展潜水员和具有战略意义的劳动力。在科学研究期间进行的高级同位素分析将使用本科研究人员收集的样品，并将本科参与者不仅会在空间注重的批判性思维中获得重要的和需求的技能，而且还将暴露于先进的地球化学技术和数据集中。这些参与者将在地球科学领域完成他们的本科经验，从而从事许多类型的职业。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来评估，被认为是珍贵的支持。