Application of Siderophile Elements to the Study of the Chemical Structure and Mixing History of the Oceanic Mantle

亲铁元素在大洋地幔化学结构和混合历史研究中的应用

• 批准号: 1423879
• 负责人: Richard Walker
• 金额: $ 28万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1423879&HistoricalAwards=false
• 关键词: Application; Siderophile; Elements; Study; Chemical

The oceanic mantle may comprise more than 60% of the mass of the Earth. The modern oceanic mantle is known to be chemically and isotopically heterogeneous, primarily documented through studies of mid-ocean ridge basalts (MORB). The processes that resulted in the creation of the heterogeneities were most likely dominated by a combination of partial melting (melt removal), metasomatism (melt/fluid addition) and incorporation of recycled crust (via subduction). The relative impacts of each of these processes, the timing of the processes, and the length scales of the resulting heterogeneities remain topics of considerable debate. Clarifying the causes, timing and spatial extent of chemical and isotopic heterogeneities in the oceanic mantle is, therefore, critical for refining our knowledge of the present bulk composition of this major terrestrial reservoir, for achieving a more complete understanding of how the chemical and isotopic composition of Earth's mantle evolved through time, and for assessing the efficiency by which the oceanic mantle is convectively mixed today. To tackle these issues, sections of the oceanic mantle accessible in four ophiolite complexes (tectonically emplaced slivers of oceanic lithosphere) will be studied. The targeted ophiolites range in age from 1.95 billion years old to 6 million years old. The study will primarily focus on examining the absolute and relative abundances of siderophile (iron-loving) elements in the mantle rocks exposed in these locations. The study will seek to answer fundamental questions about the present and past oceanic mantle including: 1) What is the geometry of long-term, exceptionally melt-depleted portions of the oceanic mantle? 2) Do common oceanic mantle lithologies, such as pyroxenites and dunites, have chemical compositions and sufficient volume to be implicated in the generation of certain volcanic rocks with unusual compositions, for example some Hawaiian lavas? 3) Have key geochemical parameters in the oceanic mantle changed through time? If so, can they be correlated with the rates of processes that may have acted on the mantle through time. In addition to answering these questions about the chemical structure of the oceanic mantle, comparison of data from ophiolites spanning nearly two billion years will begin the process of documenting secular changes in the chemical structure of this mantle.

海洋的地幔可能占地球质量的60％以上。已知现代海洋套是化学和同位素异质性的，主要是通过对中洋山脊玄武岩（MORB）的研究来证明的。导致异质性产生的过程很可能是由部分熔化（熔体去除），融化/融化/添加熔体/流体添加）和再生地壳（通过俯冲）组合所控制的。这些过程中的每一个，过程的时机以及所得异质性的长度尺度的相对影响仍然是相当大的争论的主题。因此，阐明海洋套中化学和同位素异质性的原因，时机和空间范围对于完善我们对这种主要陆地储层的当前大量​​组成的了解至关重要地球的地幔随着时间的流逝而演变，并用于评估当今海洋地幔的效率。为了解决这些问题，将研究四个蛇绿岩复合物（构造岩石圈的构造片）中可进入的海洋地幔的部分。目标蛇绿岩的年龄从19.5亿年龄到600万年。这项研究将主要集中于检查在这些位置暴露的地幔岩石中铁的绝对和相对丰度。这项研究将寻求回答有关当前和过去海洋壁画的基本问题，包括：1）长期，融化的海洋斗篷的几何形状是什么？ 2）常见的海洋地幔岩性是否具有化学成分和足够的体积，与某些具有异常组成的火山岩的产生有关，例如某些夏威夷熔岩？ 3）随着时间的流逝，海洋披风中的地球化学参数发生了变化吗？如果是这样，它们是否可以与可能随着时间的推移在地幔上作用的过程率相关。 除了回答有关海景的化学结构的这些问题外，跨越近20亿年的蛇绿岩的数据的比较还将开始记录该地幔化学结构的世俗变化的过程。

项目成果

Length-scales of chemical and isotopic heterogeneity in the mantle section of the Shetland Ophiolite Complex, Scotland

• DOI: 10.1016/j.epsl.2018.02.020
• 发表时间: 2018-04
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: B. O’Driscoll;R. Walker;P. Clay;J. Day;R. Ash;J. Daly

Oceanic and Continental Lithospheric Mantle in the 1.95-Ga Jormua Ophiolite Complex, Finland: Implications for Mantle and Crustal Evolution

芬兰 1.95 Ga Jormua 蛇绿岩杂岩中的海洋和大陆岩石圈地幔：对地幔和地壳演化的影响

• DOI: 10.1093/petrology/egad080
• 发表时间: 2023
• 期刊: Journal of Petrology
• 影响因子: 3.9
• 作者: Finlayson, Valerie A;Haller, Mitchell;Day, James M;Ginley, Stephen;O'Driscoll, Brian;Kontinen, Asko;Hanski, Eero;Walker, Richard J
• 通讯作者: Walker, Richard J