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Assessing segment-scale compositional control over slow-spreading ridge morphology

评估对缓慢扩展的脊形态的分段尺度成分控制

基本信息

批准号：
1658011
负责人：
Lynne Elkins
金额：
$ 25.92万
依托单位：
University of Nebraska-Lincoln
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-03-15 至 2023-02-28
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658011&HistoricalAwards=false
关键词：
Assessing segment scale compositional control

项目摘要

The formation of oceanic crust at mid-ocean ridges is a major component of plate tectonics, and plays a key role in long-term chemical cycles and energy budgets on Earth. The seafloor topography observed at mid-ocean ridges is generated through a combination of faulting and volcanic eruptions, but the underlying factors that control faulting and volcanism remain only partially understood. Variations in these two processes can result in dramatically different crustal and seafloor characteristics, particularly at mid-ocean ridges that spread apart at slow rates. This study uses the geochemistry of seafloor lavas erupted at the slow-spreading Mid-Atlantic Ridge to investigate and understand how underlying variations in Earth's mantle layer might influence the vigor of volcanic activity and therefore, the physical characteristics of the seafloor itself and the structure of the oceanic crust. The project supports the training of a PhD student, and public outreach materials describing the project will be distributed through the University of Nebraska State Museum.This project aims to investigate the causes of underlying variations in magma flux to slow-spreading ridge axes, which in turn drive crustal construction style and the presence, absence, or episodicity of long-lived detachment faults at the ridge axis. The project rationale is that constraints on crustal construction mechanisms will ultimately lead to a robust, comprehensive model that will accurately characterize global crustal growth at all spreading rates. The central hypothesis tested in the project states that slow-spreading ridge morphology is principally controlled at the segment scale by the compositional heterogeneity of the underlying mantle. The specific research goal for the proposed study is to identify and assess geochemical variations that fingerprint the contributions of partial melts derived from enriched, fertile mantle rocks at the ridge segment length scale. The project principally uses U-Th-Pa-Ra isotope disequilibria, which are particularly sensitive to mantle melt fertility. Disequilibria will be assessed through comparisons between second-order ridge segments that exhibit distinct morphologic types along the Kane-Atlantis supersegment of the northern Mid-Atlantic Ridge between 24-30N.

洋中脊洋壳的形成是板块构造的一个主要组成部分，对地球上的长期化学循环和能量收支起着关键作用。在大洋中脊观测到的海底地形是断层和火山喷发共同作用的结果，但对控制断层和火山活动的基本因素仍然只有部分了解。这两个过程的变化可能导致地壳和海底特性的巨大差异，特别是在以缓慢速度扩展的大洋中脊。本研究利用在缓慢扩张的大西洋中脊喷发的海底熔岩的地球化学，调查和了解地球地幔层的潜在变化如何影响火山活动的活力，从而影响海底本身的物理特性和海洋地壳的结构。该项目支持博士生的培训，介绍该项目的公共宣传材料将通过内布拉斯加州立大学博物馆分发。该项目旨在调查缓慢扩张的山脊轴的岩浆流量的潜在变化的原因，这反过来又驱动了地壳构造样式以及山脊轴长期剥离断层的存在，不存在或偶发性。该项目的理由是，对地壳构造机制的限制将最终导致一个强大的，全面的模型，将准确地描述全球地壳增长的所有扩展速度。该项目中测试的中心假设指出，缓慢扩张的山脊形态主要是由下伏地幔的成分异质性在段尺度上控制的。拟议的研究的具体研究目标是确定和评估地球化学变化，指纹的贡献，部分熔融来自富集，肥沃的地幔岩在脊段长度尺度。该项目主要使用U-Th-Pa-Ra同位素不平衡，这对地幔熔融肥力特别敏感。将通过比较在北纬24- 30度之间的北方中大西洋海岭的凯恩-亚特兰蒂斯超级段沿着表现出不同形态类型的二级海岭段来评估不平衡。