Helium, Sr, Nd, and Pb Isotope Geochemistry of Intraplate Mafic Igneous Rocks in Eastern Pacific: Implications for the Origin of Linear Volcanic Chains

东太平洋板内镁铁质火成岩的氦、锶、钕和铅同位素地球化学：对线性火山链起源的启示

• 批准号: 0550237
• 负责人: Paterno Castillo
• 金额: $ 32.26万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0550237&HistoricalAwards=false
• 关键词: Helium; Sr; Nd; Pb; Isotope

ABSTRACT Castillo (0550237)Intellectual merit: The origin of the high 3He/4He signature of some intraplate lavas is one of the most controversial topics in Earth Science today. In general, the origin of the signature boils down to two competing models: the perisphere model, which states that high 3He/4He lavas originate from the shallow part of the mantle that contains recycled extraterrestrial materials and/or experienced (U + Th)/ 3He depletion processes, and the plume model, which claims that high 3He/4He lavas originate from a more primitive, relatively undegassed portion of the lower mantle. This research tries to determine which of the two models better explains the origin of high 3He/4He signature of intraplate lavas by testing which model makes valid predictions. The perisphere model predicts: (1) all intraplate lavas exhibit similar compositional characteristics, (2) some intraplate lavas have high whereas others have low 3He/4He ratios and (3) there is no correlation between He and radiogenic isotopic signatures. The plume model predicts: (1) lavas from localized intraplate volcanoes have a helium source signature different from those of lavas that form major linear volcanic chains and (2) these localized intraplate volcanoes do not have high 3He/4He ratios. This research uses He-Sr-Nd-Pb isotopic compositions of mafic igneous rocks from fossil spreading centers and fissure ridges in the eastern Pacific, as well as their corresponding major and trace element chemistry to test the models to see which is supported by the data. Broader Impacts: This project supports investigators in the state of California and form part of a Ph.D. dissertation of a student who will be responsible for much of the chemical and isotopic analyses and interpretation of the analytical results. All the analyses will support use of existing analytical infrastructure at the Scripps Institution of Oceanography. The research also supports work with the California Center for Ocean Sciences Education Excellence (COSEE-CA) to share key aspects of the research with the public, particularly science educators and students. It involves working with the creators of Earthguide (http://earthguide.ucsd.edu/), an online science educational resource to produce an interactive online animation feature focusing on the formation of magmas and lavas that comprise the oceanic crust. Also covered are the driving forces of plate tectonics, the nature of the Earths hidden interior, planetary rheology, and the geophysical and petrological evidence on which our current understanding is based.

摘要 Castillo (0550237)智力价值：一些板内熔岩的高 3He/4He 特征的起源是当今地球科学中最具争议的话题之一。一般来说，特征的起源可归结为两个相互竞争的模型：外围模型，该模型指出高 3He/4He 熔岩源自地幔浅部，其中包含回收的外星材料和/或经验丰富的 (U + Th)/ 3He 耗尽过程和羽流模型声称，高 3He/4He 熔岩起源于下地幔更原始、相对未脱气的部分。本研究试图通过测试哪个模型做出有效的预测来确定这两个模型中哪个更好地解释板内熔岩高 3He/4He 特征的起源。周边模型预测：（1）所有板内熔岩表现出相似的成分特征，（2）一些板内熔岩具有较高的 3He/4He 比率，而其他板内熔岩具有较低的 3He/4He 比率，（3）He 和放射性同位素特征之间没有相关性。羽流模型预测：(1) 来自局部板内火山的熔岩具有与形成主要线性火山链的熔岩不同的氦源特征，并且 (2) 这些局部板内火山不具有高 3He/4He 比率。 本研究利用来自东太平洋化石扩散中心和裂隙脊的基性火成岩的 He-Sr-Nd-Pb 同位素组成及其相应的主量和微量元素化学来测试模型，看看哪些模型得到了数据的支持。更广泛的影响：该项目为加利福尼亚州的研究人员提供支持，并构成博士项目的一部分。学生的论文，该学生将负责大部分化学和同位素分析以及分析结果的解释。所有分析都将支持使用斯克里普斯海洋学研究所现有的分析基础设施。该研究还支持与加州海洋科学教育卓越中心 (COSEE-CA) 的合作，与公众，特别是科学教育工作者和学生分享研究的关键方面。它涉及与在线科学教育资源 Earthguide (http://earthguide.ucsd.edu/) 的创建者合作，制作一个交互式在线动画专题片，重点关注构成洋壳的岩浆和熔岩的形成。 还涵盖了板块构造的驱动力、地球隐藏内部的性质、行星流变学以及我们当前理解所依据的地球物理和岩石学证据。