Collaborative Research: Evolution of an Early Enriched Reservoir in the Northern Wyoming Province: Evidence from Ancient Zircons

合作研究：怀俄明州北部早期富集储层的演化：来自古代锆石的证据

• 批准号: 0609952
• 负责人: Paul Mueller
• 金额: $ 17.4万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0609952&HistoricalAwards=false
• 关键词: Collaborative; Research; Evolution; Early; Enriched

Intellectual Merit. Constraining the size, spatial distribution, and extent of elemental fractionation that characterized both depleted and enriched geochemical reservoirs in the early Earth has been a fundamental long-term goal of terrestrial and planetary geochemists. For the Sm-Nd and Lu-Hf systems, crust-mantle evolution subsequent to 2.5 Ga has been viewed in terms of a generally monotonic increases in the radiogenic daughter isotopes within the mantle that reflects extraction of continental crust to produce a 'melt'-depleted upper mantle reservoir characterized by parent/daughter ratios that are greater than the values for the bulk silicate earth. The complementary enriched reservoir over this interval is the continental crust. However, for the earliest 4.5 to 2.5 Ga of Earth history, the rock record is more difficult to decipher - in part owing to limited exposures of rocks this old. Available data indicate that crust-mantle evolution in this period may have been quite different in terms of melt-extraction processes, leading to 'anomalous' departures from the younger Nd-Hf isotopic record. Recently, analysis of Lu-Hf systematics in old, well-preserved zircons have provided a new approach to resolving isotopic records for early earth evolution. This approach will be used to gain insights into the development of Earth's early enriched reservoirs through analysis of a suite of 3.2 to 4.0 Ga zircons preserved in both metasedimentary and metaigneous rocks from the northern Wyoming Province. The proposed research will consist of 3 primary components: [1] U-Pb dating and trace element analyses via ion probe (SHRIMP-RG), [2] finer scale elemental analyses and imaging via electron probe, and [3] measurement of Lu-Hf systematics via LA-ICP-MS on dated portions of individual zircons. The PIs have previously documented the antiquity of the crust in this region, and argued that understanding its evolution will provide fundamental insights into the early geochemical differentiation of the Earth. Broader Impacts. This project will involve training of graduate students and post-doctoral researchers in geologic and analytical skills that will serve in future research and/or private sector employment. Undergraduate students will also be involved in this project - introducing them to methods of geologic research. Prior research results of this group have been included in popular books and in educational displays at the American Museum of Natural History (e.g., "The Earth Inside and Out", Gottesman's Hall of Planet Earth exhibit). Likewise, the proposed research will also be incorporated into formal and informal education and outreach. An example is provided by the "pet rock" approach utilized for petrology instruction at LSU. All results of this research will be disseminated via traditional presentations at professional meetings and peer reviewed publications.

智力优点。在地球早期，限制了表征耗尽和富集的地球化学储层的大小，空间分布和元素分馏的程度，一直是陆地和行星地球化学家的基本长期目标。对于SM-ND和LU-HF系统，在2.5 GA之后的地壳可能发生了，从地幔中的放射性子同位素的一般单调增加来看，反映了大陆壳以产生“融化的上皮上的地形层相比，由父母/子/女儿相比，该价值都更大的是silate sil sil sil sil sil sil sil carter sil sil carter sil carte sil carte the the of sil sil carte the the of sil sil carte the the the the of sil sil carte the the the the the the the the of sil sil carte sil carte sil carte sil carter。在此时间间隔内，互补的富含储层是大陆地壳。但是，在最早的4.5至2.5 GA的地球历史上，岩石记录更难破译 - 部分是由于这种古老的岩石暴露有限。可用的数据表明，在这一时期，地壳竖孔的演变可能在熔融萃取过程方面可能完全不同，从而导致“异常”与年轻的ND-HF同位素记录不同。 最近，对旧，保存完好的锆石中LU-HF系统学的分析为解决早期地球演化的同位素记录提供了一种新方法。这种方法将通过分析在怀俄明州北部省份的沉积物和晶体岩石中保存的3.2至4.0 Ga锆石，以洞悉地球早期富集的水库的发展。拟议的研究将由3个主要组成部分组成：[1]通过离子探针（Shrimp-RG）进行[1] U-PB年代分析和痕量元件分析，[2]通过电子探针通过电子探针进行的尺度元素分析和成像，以及[3]通过LA-ICP通过LA-ICP对单个载体的日期来测量LU-HF Systematics。 PI以前已经记录了该地区外壳的古代，并认为了解其进化将提供对地球早期地球化学分化的基本见解。更广泛的影响。该项目将涉及对研究生和博士后研究人员的地质和分析技能培训，这些研究人员将在未来的研究和/或私营部门就业中提供服务。本科生也将参与该项目 - 将他们介绍给地质研究方法。该小组的先前研究结果已包含在美国自然历史博物馆的流行书籍和教育展览中（例如，Gottesman's Planet of Glanet Earth展览的“内在和外地”）。同样，拟议的研究也将纳入正规和非正式教育和外展中。 LSU的“宠物岩石”方法用于岩石学指导，提供了一个示例。这项研究的所有结果将通过专业会议和同行评审出版物的传统演讲来传播。