ABR: Axial Magma Chambers and Shallow Fractionation Processes: A Comparative Mineralogic and Petrologic Study of Three Ridge Segments

ABR：轴向岩浆室和浅层分馏过程：三个山脊段的矿物学和岩石学比较研究

• 批准号: 9711294
• 负责人: Michael Garcia
• 金额: $ 20.5万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-15 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9711294&HistoricalAwards=false
• 关键词: ABR; Axial; Magma; Chambers; Shallow

Processes of shallow fractionation of mantle-derived melts are central to the creation of oceanic crust. In this study, we will undertake a comprehensive, systematic and quantitative study of the mineralogy and petrology of phyric lavas from three mid-ocean ridge segments with very different AMC characteristics and progressive shrinking and disappearance of the melt lens. The three ridge segments are the East Pacific Rise at 9 30'N, 10 30'N and the Mid- Atlantic Ridge at 26 S, for which we have samples that are well studied for major elements, trace elements, isotopic ratios, and baseline petrography and mineralogy. The samples we propose to study in detail contain phenocryst and microphenocryst assemblages, as well as refractory megacrysts containing melt inclusions. Using a variety of techniques (point counting, Nomarski, crystal size distributions, and electron microprobe) we will determine the abundances, compositions and compositional zoning of different crystal populations and their melt inclusions. These data will be interpreted using available petrologic tools to constrain the order and relative importance of identified processes of shallow fractionation relating the various liquids and solids present in each of the three areas. The comparative nature of the study and the wide variety of quantitative mineralogic and petrologic constraints will allow us to test numerous current ideas about AMC processes, including the notion that the melt lens is the site of extensive magma mixing.

幔源熔体的浅部分离过程是洋壳形成的核心。本研究 将 承担 一个全面的， 系统 斑状熔岩的矿物学和岩石学定量研究 从三个大洋中脊部分， 非常不同的AMC特性和熔融透镜的逐渐收缩和消失。这三个海脊段分别是北纬9 30 '、10 30'的东太平洋海隆和南纬26 '的大西洋中脊，我们对这三个海脊段的样品进行了充分的主元素、微量元素、同位素比值和基线岩相学和矿物学研究。我们建议详细研究的样品含有斑晶和微斑晶 组装， 作为 以及 作为 含有熔融包裹体的耐火巨晶。 使用各种技术 （点 计数， 诺玛斯基， 晶体 粒度分布和电子探针），我们将确定不同晶体群体及其熔体包裹体的丰度、成分和成分分带。 将使用现有的岩石学工具对这些数据进行解释，以限制与三个区域中存在的各种液体和固体相关的已识别浅层分馏过程的顺序和相对重要性。 研究的比较性质和广泛的多样性 的 定量 矿物学 和 岩石学的限制将使我们能够测试许多目前关于AMC过程的想法，包括熔体透镜是广泛的岩浆混合场所的概念。