Insights into the Earliest Magmas from Inclusions and Trace Elements in Zircon

从锆石中的包裹体和微量元素洞察最早的岩浆

• 批准号: 1551437
• 负责人: Timothy Harrison
• 金额: $ 28.06万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-02-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551437&HistoricalAwards=false
• 关键词: Insights; into; Earliest; Magmas; Inclusions

Earth's first few hundred million years remains one of the last frontiers for fundamental discovery in the earth sciences but lacks a rock record. Grains of the mineral zircon deposited in younger sediments are the best known resource for investigating this period. Zircons from the Jack Hills locality in Western Australia have yielded great insights into the character of Hadean (i.e., 4 billion years ago, or Ga) magmas through investigation of both their trace chemistry and exotic phases trapped within the zircons as they grew (i.e., mineral inclusions). However, fully exploiting the information recorded in these zircons and their inclusions has been hampered by a lack of foundational studies. This project constitutes a series of investigations into various aspects of zircon trace element chemistry and inclusion character, which will allow for better understanding of the geologic processes acting on Hadean Earth. Fundamental observations on the trace element chemistry and mineral inclusion character of the Hadean Jack Hills zircons have revealed several aspects of the chemistry and mineralogy of the magmas from which they grew. Quartz and muscovite dominate thelikely primary inclusion assemblages of the zircons, suggesting shale-like precursors. The zircons also contain rare oxide, sulfide, and carbonaceous phases relevant to various under-explored aspects of their host magma chemistry, especially volatiles. However, questions remain as to how to distinguish primary inclusion assemblages, their relationship to magma chemistry, and the relevance of various aspects of host zircon trace chemistry to magmatic volatile contents.This project constitutes several allied investigations of Hadean zircon trace chemistry and inclusion character which can reveal important aspects of source melt chemistry and define objective criteria for distinguishing primary versus altered mineral inclusions. The discovery of carbonaceous inclusions in Hadean zircons allows for the documentation of carbon isotopic variations during the Hadean and early Archean. In addition, the relationship of source magma trace element content and redox conditions with zircon chemistry and inclusion assemblages will be investigated using a suite of ~400 million year old granitoids of known composition and origin, and the results applied to better understand the last dark age of Earth history.

地球的头几亿年仍然是地球科学基本发现的最后边界之一，但缺乏摇滚记录。 沉积在年轻沉积物中的矿物锆石的谷物是研究此期间的最著名资源。 来自西澳大利亚州杰克山（Jack Hills）地区的锆石通过调查其痕量化学反应和奇异的相位，对哈德斯（即40亿年前或GA）岩浆的特征产生了很大的见解。 但是，由于缺乏基础研究，充分利用这些锆石及其夹杂物的信息受到了阻碍。 该项目构成了对锆石痕量元素化学和包容性特征各个方面的一系列研究，这将使人们可以更好地理解对Hadean Earth上作用的地质过程。 Hadean Jack Hills锆石的痕量元素化学和矿物包容性的基本观察结果揭示了它们生长的岩浆的化学和矿物学的几个方面。 石英和麝香木占主导地位的锆石的原发性融合组合，暗示着页岩样前体。锆石还包含稀有的氧化物，硫化物和碳质相，与宿主岩浆化学（尤其是挥发物）的各种未探索的方面相关。然而，关于如何区分主要的纳入组合，它们与岩浆化学的关系以及宿主锆石痕量化学与岩浆挥发物含量的各个方面的相关性仍然存在问题。该项目构成了Hadean锆石痕量化学和包容性的几项相关研究，这些研究可以揭示源化学的重要方面，以揭示源化学的重要方面，并定义了梅尔特化学的重要方面，并构成了分化的一小部分。 Hadean锆石中碳质夹杂物的发现允许在Hadean和早期大帝期间记录碳同位素变化。 此外，将使用约4亿年历史的已知成分和起源的套件来研究源岩浆痕量元素含量和氧化还原条件与锆石化学和包容组合的关系，并适用于更好地了解地球历史的最后一个黑暗时代。